Are MRI's for soft tissue scans?
Lumbar disc disease
In symptomatic cases the diagnosis should be confirmed by an MRI scan. However, in cases with slight symptoms, a faster and cheaper CT scan (although it is inferior to MRI scan) may be recommended. While a CT scan can show the bony structures in more detail, an MRI scan can better portray soft tissue.
Velopharyngeal insufficiency
A relatively new approach in the diagnosis is magnetic resonance imaging (MRI), which is noninvasive. MRI uses the property of nuclear magnetic resonance to image nuclei of atoms inside the body. MRI is non-radiographic and therefore can be repeated more often in short periods of time. In addition, different studies show that the MRI is better as an imaging tool than videofluoroscopy for visualizing the anatomy of the velopharynx. There are some limitations of the MRI however. Unlike videofluoroscopy and nasopharyngoscopy, MRI does not show the movement of the velopharyngeal structures during speech. In addition, artifacts can be shown on the images when the patient moves while imaging or if the patient has orthodontic appliances. MRI is limited in children who are claustrophobic. Finally, MRI is much more expensive than videofluoroscopy or nasopharyngoscopy. Because of these limits, MRI is currently not widely used for clinical diagnostic purposes.
Soft tissue sarcoma in cats and dogs
Prior to initiating any type of treatment, it is important to gather as much information as possible regarding the tumor's tissue origin, size, site, histologic grade (level of aggressiveness) and whether it has spread to other organs.
To definitively confirm the diagnosis of a soft-tissue sarcoma, the veterinarian will have to perform biopsy for histopathologic evaluation. Additional tests are performed in order to evaluate how advanced the cancer is. These tests generally involve blood and serum biochemical tests, chest X-rays to check for metastasis to the lungs and imaging studies [e.g. ultrasound, computed tomography (CT) or magnetic resonance imaging (MRI)] to evaluate the extent of the disease.
Cognitive genomics
Functional magnetic resonance imaging (fMRI) is a widely available imaging technique that measures changes in blood flow in imaged tissue. It’s commonly used in neurophysiological studies to determine neuron activation. Unlike a standard MRI, fMRI can be used to actively measure subject neuronal activity as the patient performs tasks. This technique isn’t used on conscious non-human primates due to the inability to restrain the primates during imaging. However, fMRI illustrates regional brain activity when performed on primates that performed tasks over an extended period of time and were then anesthetized.
Medical imaging
Medical ultrasonography uses high frequency broadband sound waves in the megahertz range that are reflected by tissue to varying degrees to produce (up to 3D) images. This is commonly associated with imaging the fetus in pregnant women. Uses of ultrasound are much broader, however. Other important uses include imaging the abdominal organs, heart, breast, muscles, tendons, arteries and veins. While it may provide less anatomical detail than techniques such as CT or MRI, it has several advantages which make it ideal in numerous situations, in particular that it studies the function of moving structures in real-time, emits no ionizing radiation, and contains speckle that can be used in elastography. Ultrasound is also used as a popular research tool for capturing raw data, that can be made available through an ultrasound research interface, for the purpose of tissue characterization and implementation of new image processing techniques. The concepts of ultrasound differ from other medical imaging modalities in the fact that it is operated by the transmission and receipt of sound waves. The high frequency sound waves are sent into the tissue and depending on the composition of the different tissues; the signal will be attenuated and returned at separate intervals. A path of reflected sound waves in a multilayered structure can be defined by an input acoustic impedance (ultrasound sound wave) and the Reflection and transmission coefficients of the relative structures. It is very safe to use and does not appear to cause any adverse effects. It is also relatively inexpensive and quick to perform. Ultrasound scanners can be taken to critically ill patients in intensive care units, avoiding the danger caused while moving the patient to the radiology department. The real-time moving image obtained can be used to guide drainage and biopsy procedures. Doppler capabilities on modern scanners allow the blood flow in arteries and veins to be assessed.
Pentalogy of Cantrell
Magnetic resonance imaging (MRI) may also be performed to assess the degree of certain anomalies such as abdominal wall and pericardial defects. An MRI uses a magnetic field and radio waves to produce cross-sectional images of particular organs and bodily tissues.
Safety of magnetic resonance imaging
As described in the Physics of magnetic resonance imaging article, many MRI scanners rely on cryogenic liquids to enable the superconducting capabilities of the electromagnetic coils within. Although the cryogenic liquids used are non-toxic, their physical properties present specific hazards.
Ultrasound computer tomography
USCT systems designed for medical imaging of soft tissue typically aim for resolution in order of centimeters to millimeters and require therefore ultrasound waves in the order of mega-hertz frequency. This requires typically water as low-attenuating transmission medium between ultrasound transducers and object to retain suitable sound pressures.
Soft x-ray microscopy
The ALS is also home to the world's first soft x-ray microscope designed for biological and biomedical research. This new instrument, XM-2 was designed and built by scientists from the National Center for X-ray Tomography (http://ncxt.lbl.gov). XM-2 is capable of producing 3-Dimensional tomograms of cells.
Brachial plexus
Imaging of the Brachial Plexus can be done effectively by using a higher magnetic strength MRI Scanner like 1.5 T or more. It is impossible to evaluate the brachial plexuses with plain Xray, CT and ultrasound scanning can manage to view the plexuses to an extent; hence MRI is preferred in imaging brachial plexus over other imaging modalities due to its multiplanar capability and the tissue contrast difference between brachial plexus and adjacent vessels. The plexuses are best imaged in coronal and sagittal planes, but axial images give an idea about the nerve roots. Generally, T1 WI and T2 WI images are used in various planes for the imaging; but new sequences like MR Myelolography, Fiesta 3D and T2 cube are also used in addition to the basic sequences to gather more information to evaluate the anatomy more.
X-ray detector
To obtain an image with any type of image detector the part of the patient to be X-rayed is placed between the X-ray source and the image receptor to produce a shadow of the internal structure of that particular part of the body. X-rays are partially blocked ("attenuated") by dense tissues such as bone, and pass more easily through soft tissues. Areas where the X-rays strike darken when developed, causing bones to appear lighter than the surrounding soft tissue.
Medical ultrasound
Ultrasound is also used for elastography, which is a relatively new imaging modality that maps the elastic properties of soft tissue. This modality emerged in the last two decades. Elastography is useful in medical diagnoses as it can discern healthy from unhealthy tissue for specific organs/growths. For example, cancerous tumors will often be harder than the surrounding tissue, and diseased livers are stiffer than healthy ones.
Optical coherence elastography
Requiring no injections, OCE is an non-invasive imaging method can gives more details than ultrasound or MRI. Using light source to image biological tissue, OCE is considered generally safe compared to CT scan and other radiographic imaging modalities which involve with ionizing radiation. And it is also more affordable and time efficient compared to MRI. However, OCE can also cause tissue damage in some handling. For example, surface acoustic wave OCE can cause to a tissue is primarily concentrated on temperature effects. In the focus point, the temperature of the tissue will rise locally. Therefore, it is necessary to take this into account in certain circumstances.
Neurovirology
CT scans and MRI scans are useful in visualizing inflammation and lesions caused by viral infection of the CNS. MRI is used to visualize deep white matter and temporal lobe lesions, which are not well defined by a CT scan.
In vivo magnetic resonance spectroscopy
Magnetic resonance spectroscopy (MRS), also known as nuclear magnetic resonance (NMR) spectroscopy, is a non-invasive, ionizing-radiation-free analytical technique that has been used to study metabolic changes in brain tumors, strokes, seizure disorders, Alzheimer's disease, depression and other diseases affecting the brain. It has also been used to study the metabolism of other organs such as muscles. In the case of muscles, NMR is used to measure the intramyocellular lipids content (IMCL).
Susceptibility weighted imaging
Susceptibility weighted imaging (SWI), originally called BOLD venographic imaging, is an MRI sequence that is exquisitely sensitive to venous blood, hemorrhage and iron storage. SWI uses a fully flow compensated, long echo, gradient recalled echo (GRE) pulse sequence to acquire images. This method exploits the susceptibility differences between tissues and uses the phase image to detect these differences. The magnitude and phase data are combined to produce an enhanced contrast magnitude image. The imaging of venous blood with SWI is a blood-oxygen-level dependent (BOLD) technique which is why it was (and is sometimes still) referred to as BOLD venography. Due to its sensitivity to venous blood SWI is commonly used in traumatic brain injuries (TBI) and for high resolution brain venographies but has many other clinical applications. SWI is offered as a clinical package by Philips and Siemens but can be run on any manufacturer’s machine at field strengths of 1.0 T, 1.5 T, 3.0 T and higher.
Medical imaging
Like CT, MRI traditionally creates a two-dimensional image of a thin "slice" of the body and is therefore considered a tomographic imaging technique. Modern MRI instruments are capable of producing images in the form of 3D blocks, which may be considered a generalization of the single-slice, tomographic, concept. Unlike CT, MRI does not involve the use of ionizing radiation and is therefore not associated with the same health hazards. For example, because MRI has only been in use since the early 1980s, there are no known long-term effects of exposure to strong static fields (this is the subject of some debate; see 'Safety' in MRI) and therefore there is no limit to the number of scans to which an individual can be subjected, in contrast with X-ray and CT. However, there are well-identified health risks associated with tissue heating from exposure to the RF field and the presence of implanted devices in the body, such as pacemakers. These risks are strictly controlled as part of the design of the instrument and the scanning protocols used.
MRI sequence
Magnetic resonance angiography ("MRA") is a group of techniques based to image blood vessels. Magnetic resonance angiography is used to generate images of arteries (and less commonly veins) in order to evaluate them for stenosis (abnormal narrowing), occlusions, aneurysms (vessel wall dilatations, at risk of rupture) or other abnormalities. MRA is often used to evaluate the arteries of the neck and brain, the thoracic and abdominal aorta, the renal arteries, and the legs (the latter exam is often referred to as a "run-off").
Magnetic resonance angiography
Magnetic resonance angiography (MRA) is a group of techniques based on magnetic resonance imaging (MRI) to image blood vessels. Magnetic resonance angiography is used to generate images of arteries (and less commonly veins) in order to evaluate them for stenosis (abnormal narrowing), occlusions, aneurysms (vessel wall dilatations, at risk of rupture) or other abnormalities. MRA is often used to evaluate the arteries of the neck and brain, the thoracic and abdominal aorta, the renal arteries, and the legs (the latter exam is often referred to as a "run-off").
SQUID
For example, SQUIDs are being used as detectors to perform magnetic resonance imaging (MRI). While high-field MRI uses precession fields of one to several teslas, SQUID-detected MRI uses measurement fields that lie in the microtesla range. In a conventional MRI system, the signal scales as the square of the measurement frequency (and hence precession field): one power of frequency comes from the thermal polarization of the spins at ambient temperature, while the second power of field comes from the fact that the induced voltage in the pickup coil is proportional to the frequency of the precessing magnetization. In the case of untuned SQUID detection of prepolarized spins, however, the NMR signal strength is independent of precession field, allowing MRI signal detection in extremely weak fields, on the order of Earth's magnetic field. SQUID-detected MRI has advantages over high-field MRI systems, such as the low cost required to build such a system, and its compactness. The principle has been demonstrated by imaging human extremities, and its future application may include tumor screening.
Siemens Healthineers
The first magnetic resonance imaging (MRI) scanner, Siemens’ MAGNETOM system, came to the market in 1983. With the aid of powerful magnetic fields, MRI scanners produce high-quality cross-sectional images without exposing patients to radiation. The sectional images displayed tissues and organs more clearly than ever before.
3D reconstruction from multiple images
3-D models are used for planning the operation, morphometric studies and has more reliability in orthopedics.
To reconstruct 3-D images from 2-D images taken by a camera at multiple angles. Medical imaging techniques like CT scanning and MRI are expensive, and although CT scans are accurate, they can induce high radiation doses which is a risk for patients with certain diseases. Methods based on MRI are not accurate. Since we are exposed to powerful magnetic fields during an MRI scan, this method is not suitable for patients with ferromagnetic metallic implants. Both the methods can be done only when in lying position where the global structure of the bone changes. So, we discuss the following methods which can be performed while standing and require low radiation dose.
Positron emission tomography–magnetic resonance imaging
Presently, the main clinical fields of PET-MRI are oncology, cardiology and neurology. Research studies are actively conducted at the moment to understand benefits of the new PET-MRI diagnostic method. The technology combines the exquisite structural and functional characterization of tissue provided by MRI with the extreme sensitivity of PET imaging of metabolism and tracking of uniquely labeled cell types or cell receptors.
There is discussion and investigation into utilizing PET-MR with Ion Therapy for the purpose of cancer treatment. with MRI's ability to accurately depict the proton density of tissue is a good match for the benefits and technical challenges of treatment planning utilizing Ion Therapy systems.
Bone marrow
Medical imaging may provide a limited amount of information regarding bone marrow. Plain film x-rays pass through soft tissues such as marrow and do not provide visualization, although any changes in the structure of the associated bone may be detected. CT imaging has somewhat better capacity for assessing the marrow cavity of bones, although with low sensitivity and specificity. For example, normal fatty "yellow" marrow in adult long bones is of low density (-30 to -100 Hounsfield units), between subcutaneous fat and soft tissue. Tissue with increased cellular composition, such as normal "red" marrow or cancer cells within the medullary cavity will measure variably higher in density.
Lordosis
Bone scans are conducted in order to rule out possible fractures and infections, magnetic resonance imaging (MRI) is used to eliminate the possibility of spinal cord or nerve abnormalities, and computed tomography scans (CT scans) are used to get a more detailed image of the bones, muscles and organs of the lumbar region.
Phase-contrast X-ray imaging
Due to its high sensitivity to small changes in the refraction index this method is well suited to image soft tissue samples and is already implemented to medical imaging, especially in Mammography for a better detection of microcalcifications and in bone cartilage studies.
Marrow adipose tissue
To improve quantification of MAT, novel imaging techniques have been developed as a means to visualize and quantify MAT. Although proton magnetic resonance spectroscopy (1H-MRS) has been used with success to quantify vertebral MAT in humans, it is difficult to employ in laboratory animals. Magnetic resonance imaging (MRI) provides MAT assessment in the vertebral skeleton in conjunction with μCT-based marrow density measurements. A volumetric method to identify, quantify, and localize MAT in rodent bone has been recently developed, requiring osmium staining of bones and μCT imaging, followed by advanced image analysis of osmium-bound lipid volume (in mm) relative to bone volume. This technique provides reproducible quantification and visualization of MAT, enabling the ability to consistently quantify changes in MAT with diet, exercise, and agents that constrain precursor lineage allocation. Although the osmium method is quantitatively precise, osmium is toxic and cannot be compared across batched experiments. Recently, researchers developed and validated a 9.4T MRI scanner technique that allows localization and volumetric (3D) quantification that can be compared across experiments. 
Hematopoietic cells (also known as blood cells) reside in the bone marrow along with marrow adipocytes. These hematopoietic cells are derived from hematopoietic stem cells (HSC) which give rise to diverse cells: cells of the blood, immune system, as well as cells that break down bone (osteoclasts). HSC renewal occurs in the marrow stem cell niche, a microenvironment that contains cells and secreted factors that promote appropriate renewal and differentiation of HSC. The study of the stem cell niche is relevant to the field of oncology in order to improve therapy for multiple hematologic cancers. As such cancers are often treated with bone marrow transplantation, there is interest in improving the renewal of HSC. Recent work demonstrates that marrow adipocytes secrete factors that promote HSC renewal in most bones.
Magnetic resonance imaging
MRI is the investigative tool of choice for neurological cancers, as it has better resolution than CT and offers better visualization of the posterior cranial fossa, containing the brainstem and the cerebellum. The contrast provided between grey and white matter makes MRI the best choice for many conditions of the central nervous system, including demyelinating diseases, dementia, cerebrovascular disease, infectious diseases, Alzheimer's disease and epilepsy. Since many images are taken milliseconds apart, it shows how the brain responds to different stimuli, enabling researchers to study both the functional and structural brain abnormalities in psychological disorders. MRI also is used in guided stereotactic surgery and radiosurgery for treatment of intracranial tumors, arteriovenous malformations, and other surgically treatable conditions using a device known as the N-localizer.
Erwin L. Hahn Institute for Magnetic Resonance Imaging
The Erwin L. Hahn Institute for Magnetic Resonance Imaging is a research institute which develops magnetic resonance imaging (MRI) for both cognitive neuroscience and medical diagnosis and treatment.
Soft x-ray microscopy
Sources of soft X-rays suitable for microscopy, such as synchrotron radiation sources, have fairly low brightness of the required wavelengths, so an alternative method of image formation is scanning transmission soft X-ray microscopy. Here the X-rays are focused to a point and the sample is mechanically scanned through the produced focal spot. At each point the transmitted X-rays are recorded with a detector such as a proportional counter or an avalanche photodiode. This type of Scanning Transmission X-ray Microscope (STXM) was first developed by researchers at Stony Brook University and was employed at the National Synchrotron Light Source at Brookhaven National Laboratory.
Femoroacetabular impingement
Radiographic assessment is often considered first line for FAI, providing a two-dimensional view of the hip joints. Anterior-posterior pelvis and a lateral image of the hip in question should be attained. A 45-degree Dunn view is also recommended. MRI imaging may follow, particularly if there is no specific evidence on radiographs, producing a three-dimensional reconstruction of the joint for better definition, to evaluate the hip cartilage, or measure hip socket angles (e.g. the alpha-angle as described by Nötzli in 2-D and by Siebenrock in 3-D). MR arthrogram had been used in the past, as it was more sensitive for picking up soft tissue lesions; however, due to improvement in technology, MRI is now considered comparable for picking up such lesions. CT is not usually used due to radiation exposure and no benefit above MRI. It is possible to perform dynamic simulation of hip motion with CT or MRI assisting to establish whether, where, and to what extent, impingement is occurring.
Transient synovitis
More advanced imaging techniques can be used if the clinical picture is unclear; the exact role of different imaging modalities remains uncertain. Some studies have demonstrated findings on magnetic resonance imaging (MRI scan) that can differentiate between septic arthritis and transient synovitis (for example, signal intensity of adjacent bone marrow). Skeletal scintigraphy can be entirely normal in transient synovitis, and scintigraphic findings do not distinguish transient synovitis from other joint conditions in children. CT scanning does not appear helpful.
Synthetic MRI
Creating a synthetic contrast weighted image is very quick and the scanner setting parameters can be changed interactively. This is different from acquiring the images directly on the MRI scanner with a pulse sequence where it might take several minutes to get new images with different settings. Synthetic MRI also enables the possibility to create new image contrast weightings after the scan has been completed and the patient has left the hospital. A prospective multi-reader, multi-case, multi-center clinical trial of overall image quality of synthetic MRI compared to conventional MRI in a general neuroimaging population has shown that synthetic MRI is non-inferior to conventional imaging.
Synthetic MRI is based on parametric maps. These maps are generated by using the MR scanner not to acquire an image, but to measure magnetic properties in the tissue.
Magnetic resonance imaging
Applications in the musculoskeletal system include spinal imaging, assessment of joint disease, and soft tissue tumors.
Unicameral bone cyst
Magnetic resonance imaging scans are used to identify the precise location of the cyst, to see how aggressive the disease is, and to determine the actual shape and size. The MRI uses a combination of magnets and radio-frequencies to produce various detailed, computerized images of the cyst and its surrounding body structures.
Raymond Damadian
According to a "Wall Street Journal" article, Damadian's initial methods were flawed for practical use, relying on a point-by-point scan of the entire body and using relaxation rates, which turned out to not be an effective indicator of cancerous tissue. However, the same article pointed out, “Nevertheless, his observation of T and T differences in cancerous tissue was a Eureka moment for Paul Lauterbur.” Furthermore, Damadian's seminal paper documented in its Table 2 that T relaxation times were different, beyond experimental uncertainty, across all his samples over different healthy tissues: rectus muscle, liver, stomach, small intestine, kidney, and brain. This showed the way to accurate imaging of the body's soft tissues for the first time; X-ray imaging was severely deficient for soft tissue analysis because the difference in absorption was so small (<4%). 
So when in the court case Fonar v. General Electric, GE's attorneys made the same claim that relaxations times were also prolonged in non-cancerous tissue, so were not a good diagnostic, Fonar's attorneys responded that it was unfair to punish Damadian because his methods detected even "more" features than he had intended. Indeed, even today, 90% of MRI scans on patients produce images that are relaxation dependent, either T- or T-dependent images.
In 1974, he received the first patent in the field of MRI when he patented the concept of NMR for detecting cancer after filing an application in 1972—now there are over 4,500 patents on MRI. As the National Science Foundation notes, “The patent included the idea of using NMR to ‘scan’ the human body to locate cancerous tissue.” However, it did not describe a method for generating pictures from such a scan or precisely how such a scan might be done. But without Damadian's discovery of the profound sensitivity of the relaxation time to different tissue types and malignant tissue, there would be no picture at all.
In the 1950s, Herman Carr reported creating a one-dimensional MR image. Prompted by Damadian's report on the potential medical uses of NMR, Paul Lauterbur expanded on Carr's technique and developed a way to generate the first MRI images, in 2D and 3D, using gradients. Peter Mansfield from the University of Nottingham then developed a mathematical technique that would allow scans to take seconds rather than hours and produce clearer images than Lauterbur had. While Lauterbur and Mansfield focused on animals and human limbs, Damadian built the first full-body MRI machine and produced the first full magnetic resonance imaging ("MRI") scan of the human body, albeit using a “focused field” technique that differs considerably from modern imaging. In recording the history of MRI, Mattson and Simon (1996) credit Damadian with describing the concept of whole-body NMR scanning, as well as discovering the NMR tissue relaxation differences that made this feasible.
Interventional magnetic resonance imaging
Because of the lack of harmful effects on the patient and the operator, MR is well suited for "interventional radiology", where the images produced by an MRI scanner are used to guide a minimally-invasive procedure intraoperatively and/or interactively. Interventional MRI can be used for a variety of specialized procedures. iMRI systems are often used for doing biopsies of lesions, resections of tumors, guiding thermal ablation of tissue, as well as other procedures. It is commonly used in neurosurgery where every millimeter of tissue spared in surgery can make a difference for patient recovery.
Implant (medicine)
Patient with orthopaedic implants sometimes need to be put under magnetic resonance imaging (MRI) machine for detailed musculoskeletal study. Therefore, concerns have been raised regarding the loosening and migration of implant, heating of the implant metal which could cause thermal damage to surrounding tissues, and distortion of the MRI scan that affects the imaging results. A study of orthopaedic implants in 2005 has shown that majority of the orthopaedic implants does not react with magnetic fields under the 1.0 Tesla MRI scanning machine with the exception of external fixator clamps. However, at 7.0 Tesla, several orthopaedic implants would show significant interaction with the MRI magnetic fields, such as heel and fibular implant.
Safety of magnetic resonance imaging
Although painless, MRI scans may be unpleasant for those who are claustrophobic or otherwise uncomfortable with the imaging device surrounding them. Older closed bore MRI systems have a fairly long tube or tunnel. The part of the body being imaged must lie at the center of the magnet, which is at the absolute center of the tunnel. Because scan times on these older scanners may be long (occasionally up to 40 minutes for the entire procedure), people with even mild claustrophobia are sometimes unable to tolerate an MRI scan without management. Some modern scanners have larger bores (up to 70 cm) and scan times are shorter. A 1.5 T wide short bore scanner increases the examination success rate in patients with claustrophobia and substantially reduces the need for anesthesia-assisted MRI examinations even when claustrophobia is severe.
Podiatry
All podiatrists may refer patients for Medicare rebatable plain x-rays of the foot, leg, knee and femur, as well as ultrasound examination of soft tissue conditions of the foot. Podiatrists may refer patients for other radiology investigations such as CT, MRI or bone scans, however Medicare rebates do not currently exist for these examinations. Similarly, podiatrists may refer patients when needed to specialist medical practitioners, or for pathology testing, however similar exclusions in the Medicare Benefits Schedule prevent rebates being available to patients for these referrals.
Magnetic resonance elastography
Magnetic resonance elastography (MRE) is a non-invasive medical imaging technique that measures the mechanical properties (stiffness) of soft tissues by introducing shear waves and imaging their propagation using MRI. Diseased tissues are often stiffer than the surrounding normal tissue. For instance, breast cancers are much harder than healthy fibroglandular tissue. This characteristic has been used by physicians for screening and diagnosis of many diseases, through palpation. MRE calculates the mechanical parameter as elicited by palpation, in a non-invasive and objective way.
Vein matching
While other types of biometric scanners are more popular for security systems, Vascular scanners are growing in popularity. Fingerprint scanners are more frequently used, but Naito says they generally do not provide enough data points for critical verification decisions. Since fingerprint scanners require direct contact of the finger with the scanner, dry or abraded skin can interfere with the reliability of the system. Skin diseases, such as psoriasis can also limit the accuracy of the scanner, not to mention direct contact with the scanner can result in need for more frequent cleaning and higher risk of equipment damage. Vascular scanners do not require contact with the scanner, and since the information they read is on the inside of the body, skin conditions do not affect the accuracy of the reading. Vascular scanners also work with extreme speed, scanning in less than a second. As they scan, they capture the unique pattern veins take as they branch through the hand. Compared to the Retinal Scanner, which is more accurate than the vascular scanner, the retinal scanner has much lower popularity, because of its intrusive nature. People generally are uncomfortable exposing their eyes to an unknown light, not to mention retinal scanners are more difficult to install, since variances in height and face angle must be accounted for.
Physics of magnetic resonance imaging
Typically, in soft tissues "T" is around one second while "T" and "T" are a few tens of milliseconds. However, these values can vary widely between different tissues, as well as between different external magnetic fields. This behavior is one factor giving MRI its tremendous soft tissue contrast.
Soft-tissue sarcoma
Most soft-tissue sarcomas are not associated with any known risk factors or identifiable cause. There are some exceptions:The only reliable way to determine whether a soft-tissue tumour is benign or malignant is through a biopsy. The two methods for acquisition of tumour tissue for cytopathological analysis are:
A pathologist examines the tissue under a microscope. If cancer is present, the pathologist can usually determine the type of cancer and its grade. Here, 'grade' refers to a scale used to represent concisely the predicted growth rate of the tumour and its tendency to spread, and this is determined by the degree to which the cancer cells appear abnormal when examined under a microscope. Low-grade sarcomas, although cancerous, are defined as those that are less likely to metastasise. High-grade sarcomas are defined as those more likely to spread to other parts of the body.
For soft-tissue sarcoma, thetwo histological grading systems are the National Cancer Institute system and the French Federation of Cancer Centers Sarcoma Group system.
Soft tissue injury
Ultimately, the best method of imaging soft tissue is magnetic resonance imaging (MRI), though it is cost-prohibitive and carries a high false positive rate.
Bone-anchored hearing aid
Some surgeons perform a reduction of the subcutaneous soft tissue. The rationale for this is to reduce the mobility between implant and skin to avoid inflammation at the penetration site. This reduction of the soft tissue has been questioned and some surgeons do not perform any or a minimum of it. The rationale for this is that any surgery will result in some scar tissue that could be the focus of infection. The infections seen early during the development of the surgical procedure could perhaps be explained by the lack of seal between implant and abutment allowing bacteria to enter the space. A new helium tight seal may be advantageous and prevent biofilm formation. This will also allow the surgeon to use longer abutments should a need exist. Three to six weeks later or even earlier, the audiologist will fit and adjust the hearing processor according to the patient's hearing level. The fitting will be made using a special program in a computer.
Full-body CT scan
An alternative to a full-body CT scan may be Magnetic resonance imaging (MRI) scans. MRI scans are generally more expensive than CT but do not expose the patient to ionizing radiation and are being evaluated for their potential value in screening.
Aortic dissection
The disadvantage of the MRI scan in the face of aortic dissection is that it may be available only in larger hospitals, and the scan is relatively time-consuming, which could be dangerous in people who are already very unwell. Due to the high-intensity magnetic fields used during MRI, it cannot be used on individuals with metallic implants. In addition, some individuals experience claustrophobia while surrounded by the MRI magnet.
Laminotomy
Since an MRI provides excellent imaging of blood vessels and tissues, it is recognized as the best type of imaging to observe signs associated with lumbar compression. The precise measurement of the diameter of the spinal canal is a particularly important component when determining the severity of the stenosis itself. High strength 3-Tesla MRI machines are being utilized due to the increased vascular imaging capabilities. Better resolution capacity allows for more detailed observations by the healthcare provider. The sharp contrast of the high power MRI outlines details in the vertebra that are critical when examining a patient with lumbar spinal stenosis who may need a laminotomy. MRI scanning post invasive surgery is used to see the quality of the surgery itself, yet the appropriate postoperative time elapsed before conducting an MRI is a debated topic.
Physics of magnetic resonance imaging
MRI is used to image every part of the body, and is particularly useful for neurological conditions, for disorders of the muscles and joints, for evaluating tumors, and for showing abnormalities in the heart and blood vessels.
Spontaneous cerebrospinal fluid leak
There is disagreement over whether MRI should be the diagnostic tool of choice. Magnetic resonance imaging is less effective than CT at directly imaging sites of CSF leak. MRI studies may show pachymeningeal enhancement (when the dura mater looks thick and inflamed), sagging of the brain, pituitary enlargement, subdural hygromas, engorgement of cerebral venous sinuses, and other abnormalities. For 20% of patients, MRIs present as completely normal. MRIs performed with the patient seated upright (vs. laying supine) are not better for diagnosing CSF leaks, but are more than twice as effective at diagnosing cerebellar tonsillar ectopia, also known as Chiari malformation. Cerebellar tonsillar ectopia shares many of the same symptoms as CSF leak, but originates either congenitally or from trauma, including whiplash strain to the dura.
Pleurisy
Magnetic resonance imaging (MRI), also called nuclear magnetic resonance (NMR) scanning, uses powerful magnets to show pleural effusions and tumors.
TeraView
Due in part to its ability to recognize spectral fingerprints, terahertz pulsed imaging can be applied to provide contrast between different types of soft tissue. Also, it is a sensitive means of detecting the degree of water content and markers of cancer and other diseases. Attempts have been made to apply Terahertz to image cancers like breast, cancer as well as other diseases in medicine, oral health care, and related areas. The company announced it has been cleared by the Medicines and Healthcare products Regulatory Agency (MHRA) to trial "in-vivo" terahertz spectroscopy for bio-medical research. The trials will be held in Guy's Hospital in London and aim to determine if the technology can be applied real-time for accurate removal of cancer tissue.
Elastography
Elastography is a medical imaging modality that maps the elastic properties and stiffness of soft tissue. The main idea is that whether the tissue is hard or soft will give diagnostic information about the presence or status of disease. For example, cancerous tumours will often be harder than the surrounding tissue, and diseased livers are stiffer than healthy ones.
Vertebral osteomyelitis
Radiological intervention is often necessary to confirm the presence of vertebral osteomyelitis in the body. Plain-film radiological orders are necessary for all patients displaying symptoms of the disease. This diagnostic approach is often preliminary to other radiological procedures, such as magnetic resonance imaging, or MRI, computed tomography (CT) scan, fine-needle aspiration biopsy, and nuclear scintigraphy. The initial plain-film X-ray images are scanned for any indication of disc compression between two vertebrae or the degeneration of one or more vertebrae. Only when these findings are ambiguous is further testing necessary to diagnose the disease. Other radiological approaches offer more comprehensive imaging of the spinal area, but can often prove inconclusive. MRI scans do not expose the patient to radiation and are highly sensitive to changes in the size and appearance of the intervertebral discs; however, findings on the MRI scan may be confused with other conditions such as the presence of tumors or bone fractures. If MRI imaging is inconclusive, the high sensitivity to erosions in the vertebrae or intervertebral discs of CT scans may be preferred for their ability to indicate signs of the disease more clearly than MRI. Additional tests may be ordered if such preliminary tests cannot confirm a diagnosis; for example, needle biopsies may be needed to take samples of bone surrounding the disc space where the infection is thought to live, or nuclear bone scans may be used to contrast areas of healthy bone with areas of infection.
Lameness (equine)
Computed tomography (CT) is an imaging modality that produces a 3-dimensional radiograph. A series of plain radiographs are taken in a spiral around the site of interest, and the individual 2-D radiographs are converted into a 3-D image by a computer. The image may be manipulated to view in different planes, such as cross-section, making it possible to see an injury from multiple perspectives and improving diagnostic capabilities when compared to plain radiographs. Like plain radiographs, CT is not as useful for soft tissue lesions when compared to boney lesions. However, CT requires general anesthesia, and is more costly and less available than plain radiographs, limiting its use in general practice. CT provides a large amount of data with exceptional speed, taking only seconds to minutes to complete. When compared to MRI, it is not only significantly faster (MRI takes 1–2 hours to produce an image), but also less expensive. Its combination of speed and imaging capabilities makes it beneficial for use prior to orthopedic surgery, especially in the case of complicated fractures, as it allows for visualization from all sides so that the surgeon may determine the best approach and method of correction prior to cutting. Upon completion of the CT, the horse may be rolled straight into the surgery suite for immediate surgical treatment. Advances in technology now also allows for a robotic scanner to rapidly image different parts the standing horse without the need for general anesthesia.
History of magnetic resonance imaging
The US National Science Foundation notes "The patent included the idea of using NMR to 'scan' the human body to locate cancerous tissue." However, it did not describe a method for generating pictures from such a scan or precisely how such a scan might be done. Meanwhile, Paul Lauterbur at Stony Brook University expanded on Carr's technique and developed a way to generate the first MRI images, in 2D and 3D, using gradients. In 1973, Lauterbur published the first nuclear magnetic resonance image and the first cross-sectional image of a living mouse in January 1974. In the late 1970s, Peter Mansfield, a physicist and professor at the University of Nottingham, England, developed the echo-planar imaging (EPI) technique that would lead to scans taking seconds rather than hours and produce clearer images than Lauterbur had. Damadian, along with Larry Minkoff and Michael Goldsmith, obtained an image of a tumor in the thorax of a mouse in 1976. They also performed the first MRI body scan of a human being on July 3, 1977, studies they published in 1977. In 1979, Richard S. Likes filed a patent on k-space .
During the 1970s a team led by John Mallard built the first full-body MRI scanner at the University of Aberdeen. On 28 August 1980 they used this machine to obtain the first clinically useful image of a patient's internal tissues using MRI, which identified a primary tumour in the patient's chest, an abnormal liver, and secondary cancer in his bones. This machine was later used at St Bartholomew's Hospital, in London, from 1983 to 1993. Mallard and his team are credited for technological advances that led to the widespread introduction of MRI.
Occult fracture
The diagnostic performance of MRI in the detection of occult fractures has been shown to be comparable, or better than MDCT. Indeed, while the specificity of both CT and MRI for the diagnosis of fracture can be as high as 100%, the sensitivity was reported to be higher for MRI. The superiority of MRI over any other imaging modality including MDCT for the detection of occult hip fractures is now recognised. For instance, an occult intertrochanteric extension of a greater trochanter fracture can be most effectively appreciated on MRI Moreover, MRI is extremely helpful in detecting associated soft tissue abnormalities, especially ligamentous lesions. MRI is now considered as the standard in this context. However, because of its relative unavailability in emergency settings and high costs, MRI may only be performed in "high risk patients" with negative X-rays. For example, when a hip occult fracture is suspected, patients with reduced baseline mobility and pain on axial compression are considered at risk and, therefore, should be examined by MRI. MRI signs of occult fractures are evident several weeks before radiographic signs appear. In the hip, a limited and cost effective MR protocol, with only T1 weighted () coronal images, may enable a reliable diagnosis or exclusion of occult fracture in very little time, for example, 7 minutes. Typically, a linear hypointensity is observed on T1 W images. MRI is also highly sensitive to marrow abnormalities surrounding the fracture line, which appear as hypointensity on T1 W images and hyperintensity on fluid-sensitive sequences. Such signal changes are thought to be a combination of bone marrow edema, intraosseous haemorrhage, and/or granulation tissue and help to identify even undisplaced fractures. However, in the absence of a history of trauma and linear hypointensities on T1 W images, isolated bone marrow edema may represent other pathologies such as osteoid osteoma and sclerosing osteomyelitis.
Necrotizing fasciitis
Imaging has a limited role in the diagnosis of necrotizing fasciitis. The time delay in performing imaging is a major concern. Plain radiography may show subcutaneous emphysema (gas in the subcutaneous tissue), which is strongly suggestive of necrotizing changes, but it is not sensitive enough to detect all the cases, because necrotizing skin infections caused by bacteria other than clostridial infections usually do not show subcutaneous emphysema. If the diagnosis is still in doubt, computed tomography (CT) scans and magnetic resonance imaging (MRI) are more sensitive modalities than plain radiography. However, both the CT scan and MRI are not sensitive enough to rule out necrotizing changes completely. CT scan may show fascial thickening, edema, subcutaneous gas, and abscess formation. In MRI, when fluid collection with deep fascia involvement occurs, thickening or enhancement with contrast injection, necrotizing fasciitis should be strongly suspected. Meanwhile, ultrasonography can show superficial abscess formation, but is not sensitive enough to diagnose necrotizing fasciitis. CT scan is able to detect about 80% of cases, while MRI may pick up slightly more.
A white blood cell count less than 15,000 cells/mm and serum sodium level greater than 135 mmol/l have a sensitivity of 90% in detecting the necrotizing soft tissue infection. It also has a 99% chance of ruling out necrotizing changes if the values have shown otherwise. Various scoring systems are being developed to determine the likelihood of getting necrotizing fasciitis, but a scoring system developed by Wong and colleagues in 2004 is the most commonly used. It is the laboratory risk indicator for necrotizing fasciitis (LRINEC) score, which can be used to stratify by risk those people having signs of severe cellulitis or abscess to determine the likelihood of necrotizing fasciitis being present. It uses six laboratory values: C-reactive protein, total white blood cell count, hemoglobin, sodium, creatinine, and blood glucose. A score of 6 or more indicates that necrotizing fasciitis should be seriously considered. The scoring criteria are:
Magnetic resonance microscopy
Magnetic resonance microscopy refers to very high resolution MRI imaging (down to nanometer scale, in some cases comparable with histopathology). The term MR microscopy is most widely used by the High Resolution Magnetic Resonance Imaging department at Duke University, headed by Dr. G. Allan Johnson, and the National High Magnetic Field Lab group at AMRIS, University of Florida/Florida State University.Although MRI is very common for medical applications, MRM is still developing in laboratories up to resonance frequencies of 1000 MHz (for nuclear magnetic resonance; electron magnetic resonance commonly operates at much higher frequencies). The major barriers for practical MRM include:
Myelography
Nowadays, MRI is used for most investigations previously performed by myelography. This has many advantages and does not require contrast fluid to be injected into the spine. However, a CT myelogram may be useful for patients who cannot undergo MRI (e.g., those with pacemakers or cochlear implants), or for those in whom MRI provides limited information (e.g., those with extensive metal in the spine).
Subscapularis muscle
There is no singularly imaging device or technique for a satisfying and complete subscapularis examination, but rather the combination of the sagittal oblique MRI / short-axis US and axial MRI / long-axis US planes seems to generate useful results. Additionally, lesser tuberosity bony changes have been associated with subscapularis tendon tears. Findings with cysts seem to be more specific and combined findings with cortical irregularities more sensitive.
Safety of magnetic resonance imaging
There is no proven risk of biological harm from any aspect of a MRI scan, including very powerful static magnetic fields, gradient magnetic fields, or radio frequency waves. Some studies have suggested possible genotoxic (i.e., potentially carcinogenic) effects of MRI scanning through micronuclei induction and DNA double strand breaks in vivo and in vitro, however, in most, if not all cases, others have not been able to repeat or validate the results of these studies, and the majority of research shows no genotoxic, or otherwise harmful, effects caused by any part of MRI. A recent study confirmed that MRI at some of the most potentially-risky parameters tested to date (7-tesla static magnetic field, 70 mT/m gradient magnetic field, and maximum strength radio frequency waves), did not cause any DNA damage in vitro.
Prostate cancer screening
Transrectal ultrasonography (TRUS) has the advantage of being fast and minimally invasive, and better than MRI for the evaluation of superficial tumor. It also gives details about the layers of the rectal wall, accurate and useful for staging primary rectal cancer. While MRI is better in visualization of locally advanced and stenosing cancers, for staging perirectal lymph nodes, both TRUS and MRI are capable. TRUS has a small field of view, but 3D TRUS can improve the diagnosis of anorectal diseases.
Intraoperative electron radiation therapy
Soft tissue sarcomas can be effectively treated by electron IORT, which appears to be gaining acceptance as the current practice for sarcomas in combination with EBRT (preferably preoperative) and maximal resection. Used together, IOERT and EBRT appear to be improving local control, and this method is being refined so that it can effectively be used in combination with other interventions if indicated. In studies regarding the delivery of therapeutic radiation in the limb-sparing approach to extremity soft tissue sarcomas, electron IORT has been called ‘precision radiotherapy’ by some, because the treating physician has direct visualization of the tumor or surgical cavity and can manually exclude normal tissue from the field.
Zenker's paralysis
An MRI (magnetic resonance imaging) scan is an imaging test that uses powerful magnets and radio waves to create pictures of the body. It does not use radiation. Single MRI images are called slices. The images can be stored on a computer or printed on film. One exam produces dozens or sometimes hundreds of images. To locate nerve palsy, MRI is used by physicians to detect the position and location of damaged peroneal nerve.
Preclinical imaging
Strengths: The advantage of micro-MRI is that it has good spatial resolution, up to 100 µm and even 25 µm in very high strength magnetic fields. It also has excellent contrast resolution to distinguish between normal and pathological tissue. Micro-MRI can be used in a wide variety of applications, including anatomical, functional, and molecular imaging. Furthermore, since micro-MRI’s mechanism is based on a magnetic field, it is much safer compared to radiation based imaging modalities such as micro-CT and micro-PET.
Headache
All people who present with red flags indicating a dangerous secondary headache should receive neuroimaging. The best form of neuroimaging for these headaches is controversial. Non-contrast computerized tomography (CT) scan is usually the first step in head imaging as it is readily available in Emergency Departments and hospitals and is cheaper than MRI. Non-contrast CT is best for identifying an acute head bleed. Magnetic Resonance Imaging (MRI) is best for brain tumors and problems in the posterior fossa, or back of the brain. MRI is more sensitive for identifying intracranial problems, however it can pick up brain abnormalities that are not relevant to the person's headaches.
Spinal stenosis
MRI has become the most frequently used study to diagnose spinal stenosis. The MRI uses electromagnetic signals to produce images of the spine. MRIs are helpful because they show more structures, including nerves, muscles, and ligaments, than seen on x-rays or CT scans. MRIs are helpful at showing exactly what is causing spinal nerve compression.
Hip pain
Figure 8: 
Many pathological conditions of the hip are detected early by MRI due to its high soft tissue resolution and sensitivity. Its accuracy in studying acute hip pain in children has proved to be superior to ultrasound and plan film radiography. However, MRI accessibility and the need of sedation relegate its use to selected cases in which diagnosis is not clear with less demanding techniques. These include differentiating transient synovitis from a septic arthritis or osteomyelitis, diagnosis of inflammatory joint disease or bone tumors, and early detection and follow-up of Perthes disease. 
MRI findings correlate with prognosis in LCPD. These include extent and distribution of epiphyseal necrosis, subchondral ossified nucleus fracture, involvement of the lateral pillar, and disturbance of physeal growth, including presence of transphyseal neovascularity or bridging. 
Recent studies have been focused on the role of diffusion weighted MRI because it does not need contrast medium administration. ADC ratio of the femoral metaphysis was positively correlated with the Herring classification. ADC ratio superior to 1.63 indicates bad prognosis with 89% sensitivity and 58% specificity. 
In adult patients, MRI is currently playing a definite role in the assessment of osteoarthritis. Although traditionally belonging to the arena of radiographs, the role of MRI has been stressed after the term femoral acetabular impingement was coined in 2003. Growing interest has been focused in accurate diagnosis of the acetabular and femoral morphological abnormalities that may lead to early osteoarthritis. 
MR imaging is considered paramount to these objectives, mainly when surgery is considered, due to the ability of MRI to portray the whole section of the femoral neck surface, as well as to image the labrum and articular cartilage. 
Diagnosis of impingement can only be achieved if, besides imaging findings, there are also clinical symptoms and positive impingement maneuvers. 
Most of the angles and measurements described in the plain radiograph section can be accurately reproduced on MRI. In addition, the superiority of MRI resolution with intra-articular contrast allows detection of labral and chondral abnormalities that may influence the choice of medical, percutaneous, or surgical management (Figure 9). 
Figure 9: 
MR arthrography has proven superior in accuracy when compared to native MR imaging. It is considered the best technique to assess the labrum. Knowledge of the normal variable morphology of the labrum helps to differentiate tears from normal variants. A triangular shape is most commonly seen in 66% of asymptomatic volunteers, but round, flattened, and absent labra can also be found in asymptomatic populations. MR arthrography has demonstrated sensitivity over 90% and specificity close to 100% in detecting labral tears. Loose bodies are demonstrated as filling defects surrounded by the hyperintense gadolinium. 
Association between labral tears and chondral damage has been demonstrated. This underscores the interaction between cartilage and labrum damage in the progression of osteoarthritis. Chondral damage to the posteroinferior part of the acetabulum as a contrecoup lesion occurs in approximately one-third of pincer cases secondary to persistent abutment on the anterior part of the joint leading to a slight posteroinferior subluxation. This is considered a bad prognosis sign. 
MR arthrography can also demonstrate ligamentum teres rupture or capsular laxity, which are debated causes of microinstability of the hip. Elongation of the capsule or injury to the iliofemoral ligament or labrum may be secondary to microtrauma in athletes. MR can demonstrate abnormalities in these cases, such as increased joint volume or a ligamentum teres tear (Figure 9). 
Intra-articular osseous causes of pain include several conditions: avascular necrosis (AVN), transient osteoporosis of the hip (TOH), tumors, and stress or insufficiency fractures. All these entities may present with a pattern of bone marrow edema characterized by decreased signal intensity on T1 weighted images and increased signal intensity on fluid sensitive sequences, such as fat saturated T2-weighted or STIR images. When there is no evidence of a focal lesion associated with the edema pattern, TOH is suspected. When a band of low intensity is seen inside the edematous area, the shape and length of this band become important. It is generally convex to the articular surface in the case of subchondral stress or insufficiency fractures, whereas it is concave, circumscribing all of the necrotic segment, in cases of AVN. When doubts do persist, gadolinium-enhanced MRI tends to show that the proximal portion beyond the band is enhanced in fractures but is not in AVN. 
MRI has been shown to have 100% sensitivity and specificity in prospective studies of occult hip fractures. These fractures were diagnosed by bone marrow edema and a low signal fracture line, mainly on T1 or T2 weighted images (Figure 10). 
Figure 10: 
In synovial proliferative disorders, MRI demonstrates synovial hypertrophy. In the case of PVNS, characteristic foci of low signal intensity related to hemosiderin deposition are better seen on gradient echo T2* images (Figure 7). In the case of synovial osteochondromatosis, the synovial hypertrophy is accompanied by intermediate signal cartilaginous loose bodies and/or low signal calcified loose bodies. 
Due to radiation concerns, CT has been relegated after MRI in the study of intra-articular causes of hip pain. The only exception where CT is considered superior to MRI is in bone tumors, because of its ability in characterizing matrix calcifications, and in depicting the anatomy of acute traumatic fractures. Typical matrix calcifications include the following: (a) osteoid mineralization, like a dense cloud, (b) chondroid calcification, reproducing a punctate popcorn pattern, or (c) fibrous calcification, ground glass-like appearance. There are also tumors that typically do not show matrix calcification. CT is also used for accurate localization of the nidus in osteoid osteomas and this must be differentiated from Brodie’s abscess or a stress fracture. The current standard treatment of osteoid osteoma is percutaneous radiofrequency ablation and this is usually performed under CT guidance. 
Quite often, CT is widely available unlike MRI, especially in the acute setting. CT is performed in this setting when doubt about the existence of a fracture persists following plain radiograph. Modern multidetector computed tomography (MDCT) shows results comparable with MRI for detecting occult fractures. 
Due to the submillimeter resolution of MDCT arthrography, many authors consider this technique complementary to MR arthrography. It may even have superior sensitivity in detecting cartilage pathology, but lesser detecting labral tears. 
CT can also be used to obtain accurate measurement of the femoral version and torsion. The femoral version is measured by an angle formed between a line through the femoral head-neck axis and another horizontal line drawn between both ischial tuberosities. Normal values range between 5 and 25°. Retroversion is considered abnormal. 
Femoral torsion is the angle between a line along the femoral head and neck axis and a second line that is touching the posterior border of both femoral condyles. The normal value at birth is approximately 32° and decreases gradually with age. In adults, the normal value ranges from 10° to 20°.
Acute pancreatitis
While computed tomography is considered the gold standard in diagnostic imaging for acute pancreatitis, magnetic resonance imaging (MRI) has become increasingly valuable as a tool for the visualization of the pancreas, particularly of pancreatic fluid collections and necrotized debris. Additional utility of MRI includes its indication for imaging of patients with an allergy to CT's contrast material, and an overall greater sensitivity to hemorrhage, vascular complications, pseudoaneurysms, and venous thrombosis.
Interventional magnetic resonance imaging
The non-magnetic environment required by the scanner and the strong magnetic radiofrequency and quasi-static fields generated by the scanner hardware require the use of specialized instruments. For example, use of non-magnetic (e.g. Titanium) surgical instruments and MR compatible patient surveillance accessories in addition to the MRI scanner itself increase the cost of IMRI. Often required is the use of an "open bore" magnet, which permits the operating staff better access to patients during the operation. Such open bore magnets are often lower field magnets, typically in the 0.2 tesla range, which decreases their sensitivity and temporal efficiency but also decreases the radio frequency power potentially absorbed by the patient during a protracted operation. Higher field magnet systems are beginning to be deployed in intraoperative imaging suites, which can combine high-field MRI with a surgical suite and even CT in a series of interconnected rooms. Specialty high-field interventional MR devices, such as the IMRIS system, can actually bring a high-field magnet to the patient within the operating theatre, permitting the use of standard surgical tools while the magnet is in an adjoining space.
MRI Robot
To be MRI compatible, a robot needs to safely operate and perform its functions within the magnetic field of the MRI without deteriorating the image quality. Thus, the development of MRI robots is a very challenging engineering task because MRI scanners use magnetic fields of very high density (3 teslas is now common), and most of the components commonly used in robotics may not be used in close proximity of the magnet.
Medical ultrasound
Sonography is effective for imaging soft tissues of the body. Superficial structures such as muscle, tendon, testis, breast, thyroid and parathyroid glands, and the neonatal brain are imaged at a higher frequency (7–18 MHz), which provides better linear (axial) and horizontal (lateral) resolution. Deeper structures such as liver and kidney are imaged at a lower frequency 1–6 MHz with lower axial and lateral resolution as a price of deeper tissue penetration.
Magnetic resonance imaging
MRI was originally called NMRI (nuclear magnetic resonance imaging), but the use of 'nuclear' in the acronym was dropped to avoid negative associations with the word. Certain atomic nuclei are able to absorb and emit radio frequency energy when placed in an external magnetic field. In clinical and research MRI, hydrogen atoms are most often used to generate a detectable radio-frequency signal that is received by antennas in close proximity to the anatomy being examined. Hydrogen atoms are naturally abundant in people and other biological organisms, particularly in water and fat. For this reason, most MRI scans essentially map the location of water and fat in the body. Pulses of radio waves excite the nuclear spin energy transition, and magnetic field gradients localize the signal in space. By varying the parameters of the pulse sequence, different contrasts may be generated between tissues based on the relaxation properties of the hydrogen atoms therein.
Low back pain
Imaging is indicated when there are red flags, ongoing neurological symptoms that do not resolve, or ongoing or worsening pain. In particular, early use of imaging (either MRI or CT) is recommended for suspected cancer, infection, or cauda equina syndrome. MRI is slightly better than CT for identifying disc disease; the two technologies are equally useful for diagnosing spinal stenosis. Only a few physical diagnostic tests are helpful. The straight leg raise test is almost always positive in those with disc herniation. Lumbar provocative discography may be useful to identify a specific disc causing pain in those with chronic high levels of low back pain. Similarly, therapeutic procedures such as nerve blocks can be used to determine a specific source of pain. Some evidence supports the use of facet joint injections, transforminal epidural injections and sacroilliac injections as diagnostic tests. Most other physical tests, such as evaluating for scoliosis, muscle weakness or wasting, and impaired reflexes, are of little use.
Center for Biomedical Imaging
The Center for Biomedical Imaging houses a 3 tesla Philips MRI scanner for functional, structural, and spectroscopic studies of humans and animals. The Center for Biomedical Imaging provides researchers with access to the MRI as well as expertise in all modalities of MRI, not only for the Boston University Community, but also for researchers at other institutions. Currently, researchers at the Center for Biomedical Imaging are working on projects funded by the National Institute of Mental Health, National Institute of Neurological Disorders and Stroke, National Institute on Drug Abuse, Human Frontier Science Program (HFSP) and Nancy Lurie Marks Family Foundation.
Medical imaging
Elastography is a relatively new imaging modality that maps the elastic properties of soft tissue. This modality emerged in the last two decades. Elastography is useful in medical diagnoses, as elasticity can discern healthy from unhealthy tissue for specific organs/growths. For example, cancerous tumours will often be harder than the surrounding tissue, and diseased livers are stiffer than healthy ones. There are several elastographic techniques based on the use of ultrasound, magnetic resonance imaging and tactile imaging. The wide clinical use of ultrasound elastography is a result of the implementation of technology in clinical ultrasound machines. Main branches of ultrasound elastography include Quasistatic Elastography/Strain Imaging, Shear Wave Elasticity Imaging (SWEI), Acoustic Radiation Force Impulse imaging (ARFI), Supersonic Shear Imaging (SSI), and Transient Elastography. In the last decade a steady increase of activities in the field of elastography is observed demonstrating successful application of the technology in various areas of medical diagnostics and treatment monitoring.
Raymond Damadian
Damadian's research into sodium and potassium in living cells led him to his first experiments with nuclear magnetic resonance (NMR) which caused him to first propose the MR body scanner in 1969. Damadian discovered that tumors and normal tissue can be distinguished in vivo by nuclear magnetic resonance (NMR) because of their prolonged relaxation times, both T (spin-lattice relaxation) or T (spin-spin relaxation). Damadian was the first to perform a full body scan of a human being in 1977 to diagnose cancer. Damadian invented an apparatus and method to use NMR safely and accurately to scan the human body, a method now well known as magnetic resonance imaging (MRI).
Fast low angle shot magnetic resonance imaging
The physical basis of MRI is the spatial encoding of the nuclear magnetic resonance (NMR) signal obtainable from water protons (i.e. hydrogen nuclei) in biologic tissue. In terms of MRI, signals with different spatial encodings that are required for the reconstruction of a full image need to be acquired by generating multiple signals - usually in a repetitive way using multiple radio-frequency excitations.
Virtopsy
CT is well suited to show foreign objects, bone and air or gas distribution throughout the body, whereas MRI sequences are strong in detailing organ and soft tissue findings. A comprehensive analysis of both surface and deep tissue findings may require fusion of CT, MRI and 3D surface data.
Saint Boniface Hospital
The Dr. Andrei Sakharov Magnetic Resonance Imaging (MRI) Facility, the first of its kind in Manitoba, has three MRI scanners. The facility allows radiologists to diagnose abnormalities of the brain, spinal cord, internal organs and joints. St. Boniface Hospital Research Centre is a recognized leader in the MRI field and has one of the largest MRI research facilities in Canada. An MRI was first installed at St. Boniface in 1990; this MRI was eventually replaced by a more modern version, which is primarily used for clinical purposes. The other two MRIs are research-oriented: they are an interventional scanner and a head-only functional unit. The clinical scanner enables the Centre to do echo-planar imaging, producing images at video rates; the interventional MRI gives physicians access to the patient during imaging, which supports research into robotics-guided laser surgery. Research carried out at the centre has been published in the "Journal of Magnetic Resonance Imaging".
Safety of magnetic resonance imaging
MRI is contraindicated in the presence of MR-unsafe implants, and although these patients may be imaged with CT, beam hardening artefact from metallic devices, such as pacemakers and implantable cardioverter-defibrillators, also may affect image quality. MRI is a longer investigation than CT and an exam may take between 20 and 40 minutes depending on complexity.
Magnetic resonance imaging
Since its development in the 1970s and 1980s, MRI has proven to be a highly versatile imaging technique. While MRI is most prominently used in diagnostic medicine and biomedical research, it also may be used to form images of non-living objects. MRI scans are capable of producing a variety of chemical and physical data, in addition to detailed spatial images. The sustained increase in demand for MRI within health systems has led to concerns about cost effectiveness and overdiagnosis.
Molecular imaging
To achieve molecular imaging of disease biomarkers using MRI, targeted MRI contrast agents with high specificity and high relaxivity (sensitivity) are required. To date, many studies have been devoted to developing targeted-MRI contrast agents to achieve molecular imaging by MRI. Commonly, peptides, antibodies, or small ligands, and small protein domains, such as HER-2 affibodies, have been applied to achieve targeting. To enhance the sensitivity of the contrast agents, these targeting moieties are usually linked to high payload MRI contrast agents or MRI contrast agents with high relaxivities. In particular, the recent development of micron-sized particles of iron oxide (MPIO) allowed to reach unprecedented levels of sensitivity to detect proteins expressed by arteries and veins.
Magnetic resonance imaging
While the hazards of X-rays are now well-controlled in most medical contexts, an MRI scan may still be seen as a better choice than a CT scan. MRI is widely used in hospitals and clinics for medical diagnosis, staging of disease and follow-up without exposing the body to radiation. However, MRI may often yield different diagnostic information compared with CT. There may be risks and discomfort associated with MRI scans. Compared with CT scans, MRI scans typically take longer and are louder, and they usually need the subject to enter a narrow, confining tube. In addition, people with some medical implants or other non-removable metal inside the body may be unable to undergo an MRI examination safely.
Osteomyelitis
Nuclear medicine scans can be a helpful adjunct to MRI in patients who have metallic hardware that limits or prevents effective magnetic resonance. Generally a triple phase technetium 99 based scan will show increased uptake on all three phases. Gallium scans are 100% sensitive for osteomyelitis but not specific, and may be helpful in patients with metallic prostheses. Combined WBC imaging with marrow studies have 90% accuracy in diagnosing osteomyelitis.
Breast cancer screening
Despite the aids provided from MRIs, there are some disadvantages. For example, although it is 27–36% more sensitive, it has been claimed to be less specific than mammography. As a result, MRI studies may have up to 30% more false positives, which may have undesirable financial and psychological costs on the patient. Also, MRI procedures are expensive and include an intravenous injection of a gadolinium contrast, which has been implicated in a rare reaction called nephrogenic systemic fibrosis (NFS). Although NSF is uncommon, other patients with a history of renal failure/disease would not be able to undergo an MRI scan. Breast MRI is not recommended for screening all breast cancer patients, yet limited to patients with high risk of developing breast cancer that may have high familial risk or mutations in BCRA1/2 genes. Breast MRI is not a perfect tool despite its increased sensitivity for detecting breast cancer masses when compared to mammography. This due to the ability of MRIs to miss some cancers that would have been detected with conventional mammography, as a result, MRI screening for breast cancer is most affective as a combination with other tests and for certain breast cancer patients. In contrast, the use of MRIs are often limiting to patients with any body metal integration such as patients with tattoos, pacemakers, tissue expanders, and so on.
Magnetic resonance imaging
MRI is in general a safe technique, although injuries may occur as a result of failed safety procedures or human error. Contraindications to MRI include most cochlear implants and cardiac pacemakers, shrapnel, and metallic foreign bodies in the eyes. The safety of MRI during the first trimester of pregnancy is uncertain, but it may be preferable to other options. Since MRI does not use any ionizing radiation, its use is generally favored in preference to CT when either modality could yield the same information. In certain cases, MRI is not preferred as it may be more expensive, time-consuming, and claustrophobia-exacerbating.
CT scan
CT scan can be used for detecting both acute and chronic changes in the lung parenchyma, that is, the internals of the lungs. It is particularly relevant here because normal two-dimensional X-rays do not show such defects. A variety of techniques are used, depending on the suspected abnormality. For evaluation of chronic interstitial processes (emphysema, fibrosis, and so forth), thin sections with high spatial frequency reconstructions are used; often scans are performed both in inspiration and expiration. This special technique is called high resolution CT. Therefore, it produces a sampling of the lung and not continuous images.
Bronchial wall thickening can be seen on lung CTs, and generally (but not always) implies inflammation of the bronchi. Normally, the ratio of the bronchial wall thickness and the bronchial diameter is between 0.17 and 0.23.
Elastography
One strength of MRE is the resulting 3D elasticity map, which can cover an entire organ. Because MRI is not limited by air or bone, it can access some tissues ultrasound cannot, notably the brain. It also has the advantage of being more uniform across operators and less dependent on operator skill than most methods of ultrasound elastography.
Prostate cancer
Prostate MRI has better soft tissue resolution than ultrasound.
Crohn's disease
CT and MRI scans are useful for evaluating the small bowel with enteroclysis protocols. They are also useful for looking for intra-abdominal complications of Crohn's disease, such as abscesses, small bowel obstructions, or fistulae. Magnetic resonance imaging (MRI) is another option for imaging the small bowel as well as looking for complications, though it is more expensive and less readily available. MRI techniques such as diffusion-weighted imaging and high-resolution imaging are more sensitive in detecting ulceration and inflammation compared to CT.
National Center for Spinal Disorders
The Radiology Department of the National Center for Spinal Disorders was one of the first to have a direct digital (ddR) x-ray equipment installed in Hungary. This made the entire spectrum of radiological examinations with lower radiation and no x-ray film possible. A 3D/4D ultrasound equipment has been in use since September, 2005. The CT/MRI laboratory also contains a fast 4 slice multisclice CT equipment for examining every region of the body and an open MRI for patients suffering from claustrophobia. Aside from the examination of the skull and the spine, the equipment is excellent for diagnosing musculoskeletal abnormalities, joints and sports injuries.
Lameness (equine)
The bone scan offers several advantages over traditional radiographs. In some cases, it may be more sensitive due to the fact that some lesions are only apparent on radiographs after they have become chronic. The bone scan allows imaging of the pelvis, vertebral column, and upper limbs, which are areas that are usually poorly imaged by radiographs on the adult horse, due to their size. It also allows some evaluation of soft tissue, which is generally not imaged well by radiographs.
Testicular cancer
For patients treated for stage I seminoma who choose surveillance rather than undergoing adjuvant therapy, there have been no randomized trials to determine the optimum frequency of scans and visits, and the schedules vary very widely across the world, and within individual countries. In the UK there is an ongoing clinical trial called TRISST. This is assessing how often scans should take place and whether magnetic resonance imaging (MRI) can be used instead of CT scans. MRI is being investigated because it does not expose the patient to radiation and so, if it is shown to be as good at detecting relapses, it may be preferable to CT.
Myelomalacia
There are two tests that can provide a definite diagnosis of myelomalacia; magnetic resonance imaging (MRI), or myelography. Magnetic resonance imaging (MRI) is a medical imaging technique used in radiology to visualize the internal structure of the body used in the diagnosing of myelomalacia. Certain MRI findings can detect where bone density and matter has been lost in people with spinal cord injuries. Diffuse hyperintensity appreciated on T2-weighted imaging of the spinal cord can be an indication of the onset or progression of myelomalacia
Neurotechnology
Magnetic resonance imaging is a vital tool in neurological research in showing activation in the brain as well as providing a comprehensive image of the brain being studied. While MRIs are used clinically for showing brain size, it still has relevance in the study of brains because it can be used to determine extent of injuries or deformation. These can have a significant effect on personality, sense perception, memory, higher order thinking, movement, and spatial understanding. However, current research tends to focus more so on fMRI or real-time functional MRI (rtfMRI). These two methods allow the scientist or the participant, respectively, to view activation in the brain. This is incredibly vital in understanding how a person thinks and how their brain reacts to a person's environment, as well as understanding how the brain works under various stressors or dysfunctions. Real-time functional MRI is a revolutionary tool available to neurologists and neuroscientists because patients can see how their brain reacts to stressors and can perceive visual feedback. CT scans are very similar to MRI in their academic use because they can be used to image the brain upon injury, but they are more limited in perceptual feedback. CTs are generally used in clinical studies far more than in academic studies, and are found far more often in a hospital than a research facility. PET scans are also finding more relevance in academia because they can be used to observe metabolic uptake of neurons, giving researchers a wider perspective about neural activity in the brain for a given condition. Combinations of these methods can provide researchers with knowledge of both physiological and metabolic behaviors of loci in the brain and can be used to explain activation and deactivation of parts of the brain under specific conditions.
Medical ultrasound
Musculoskeletal ultrasound in used to examine tendons, muscles, nerves, ligaments, soft tissue masses, and bone surfaces. Ultrasound is an alternative to x-ray imaging in detecting fractures of the wrist, elbow and shoulder for patients up to 12 years (Fracture sonography).
Prostate biopsy
Since the mid-1980s, TRUS biopsy has been used to diagnose prostate cancer in essentially a blind fashion because prostate cancer cannot be seen on ultrasound due to poor soft tissue resolution. However, multi-parametric magnetic resonance imaging (mpMRI) has since about 2005 been used to better identify and characterize prostate cancer. A study correlating MRI and surgical pathology specimens demonstrated a sensitivity of 59% and specificity of 84% in identifying cancer when T2-weighted, dynamic contrast enhanced, and diffusion-weighted imaging were used together. Many prostate cancers missed by conventional biopsy are detectable by MRI-guided targeted biopsy. In fact, a side-by-side comparison of TRUS versus MRI-guided targeted biopsy that was conducted as a prospective, investigator-blinded study demonstrated that MRI-guided biopsy improved detection of significant prostate cancer by 17.7%, and decreased the diagnosis of insignificant or low-risk disease by 89.4%.
Medical imaging
A number of different pulse sequences can be used for specific MRI diagnostic imaging (multiparametric MRI or mpMRI). It is possible to differentiate tissue characteristics by combining two or more of the following imaging sequences, depending on the information being sought: T1-weighted (T1-MRI), T2-weighted (T2-MRI), diffusion weighted imaging (DWI-MRI), dynamic contrast enhancement (DCE-MRI), and spectroscopy (MRI-S). For example, imaging of prostate tumors is better accomplished using T2-MRI and DWI-MRI than T2-weighted imaging alone. The number of applications of mpMRI for detecting disease in various organs continues to expand, including liver studies, breast tumors, pancreatic tumors, and assessing the effects of vascular disruption agents on cancer tumors.