Intravenous contrast Iodine-based preparations are usually used to opacify the vascular tre e. Different phases of enhancement can be obtained, depending on the timing of image acquis ition. IV contrast is used to differentiate normal blood vessels from abnormal masses and t o demonstrate the vascular nature of an abnormality. Drawbacks of CT These include the use of ionizing radiation (doses vary according to the ty pe of examination but can be high), hazards of IV contrast (renal impair- ment, allergy), l ack of portability, and relative cost. Some areas of the body are imaged poorly with CT, in cluding the posterior cranial fossa and spine. Fig. 1.6 Axial CT image showing normal upper abdominal anatomy. SUBASH KC/NMC-15TH/2014 12 CHAPTER 1 Techniques Nuclear medicine (traditional) Description Nuclear medicine differs from other forms of ima ging in that it shows the physiological function of a system rather than an anatomical regi on. Radioactive isotopes permit detection by emitting gamma radiation ( which is detected b y a gamma camera. In most cases the radioisotope is coupled to a biologically active molecu le or drug to localize to a desired system. Pathological conditions may lead to increased u ptake, i.e. hotspots or decreased activity, i.e. cold spots. G ) Radionuclides and radiopharmaceuticals When a radioactive substance decays it may emit radi ation in the form of alpha ( A ) and beta ( B ) particles and electromagnetic radiation in the form of gamma rays and X-rays. It is gamma rays, which penetrate the body allowing dete ction, which are exploited in nuclear medicine imaging. Radionuclides are selected which pr oduce a high volume of gamma emis- sions without emitting harmful particulate radiation (i. e. The half-life needs to be only long enough for the intended use, usually a few hours. A or B particles). The radionuclide is manufactured arti \201 cially and degrades spontaneously. The commones t radionuclide in use is technetium 99m (Tc-99m). This decays to technetium 99 with the emi ssion of a and has a half-life of 6 hours. G ray of 140keV (kilo-electron volts) When a radionuclide is coupled with a drug, it is called a radio- pharmaceutical. The pharm aceutical is chosen to rapidly localize to the intended target without side effects. Certai n radionuclides, e.g. I-123 and Ga-67, localize to the desired area without an attached pha rmaceutical. The radiopharmaceutical is injected, ingested orally, or inhaled. The gamma camera The gamma camera consists of a large sodium iodide crystal with thallium i odide as an activator. The gamma rays striking the camera are converted into light photons, which are multiplied and converted into small voltage pulses to record activity. Some scat tered rays are absorbed by a colli- mator placed in front of the crystal and the pulse heig ht analyzer selects photons of a predetermined narrow spectrum. The whole \201 eld image is shown on a cathode ray tube, which can be photographed or captured as an electrical puls e for a digital image. The image The patient must sit or lie still in front of the gamma camera until suf- \201 cient activity is recorded. Images are acquired in each desired plane, e.g. anterior, poste rior, lateral, or oblique. The image may be static or multiple frames may be acquired over a period of time to create dynamic images. SUBASH KC/NMC-15TH/2014 NUCLEAR MEDICINE (TRADITIONAL) 13 Selected image from a technetium bone scan in a patient with prostate Fig. 1.7 cancer. Mult iple areas of increased radioisotope uptake are consistent with bony metastases. SUBASH KC/NMC-15TH/2014 14 CHAPTER 1 Techniques Indications There are multiple uses of nuclear medicine imaging. Some of the com- monest ty pes of imaging are listed here with common indications. \200 Bone scan: Tc-99m labeled MD P (methyl-di-phosphonate): Infection. \200 Occult fracture. \200 Bone metastases (Fig. 1.7 ). Myocardial perfusion scan: Tl-201 chloride. \200 Thyroid uptake scan: I-123. \200 Renal imaging: Static imaging: Tc-99m DMSA (dimercaptosuccinic acid) \200\224 for split renal function, ?renal scars. Dynamic imaging: Tc-99m DTPA (diethylene triamine penta- acetic acid) or Tc-99m MAG 3 (mercaptoacetyltriglycine) excretion, renovascular hypertensio n. \200\224 renal Ventilation/perfusion scan (V/Q scan): inhaled gas, e.g. Kr-81m or Tc-99m DTPA and injected Tc-99m albumin macroaggregates: \200 Pulmonary embolus exclusion (Fig. 1.8 ). Contraindications The radiation dose of each scan must be weighed up against the alterna- t ive imaging techniques available. Particular care is needed with children, pregnant women, and breastfeeding mothers. Advantages \200 Demonstrates physiology. \200 Widely available. \200 Relatively cheap . Disadvantages \200 Radiation dose. Patient continues to emit radiation after procedure, i n diminishing doses. Poor spatial resolution for anatomical localization. \200 Time-consuming. Dose The administered dose is measured in becquerels (usually in kilo- or mega- becquerels) . The effective patient dose is given in millisievert (mSv). The effective dose of a nuclear medicine scan varies with type and administered does of radiopharmaceutical. The effective dose of a typical Tc-99m MDP bone s can is 3mSv (compared to chest radiograph = 0.1mSv, average annual background radiation UK = 2.6mSv). Patient preparation Certain types of nuclear medicine scan require patient preparation in t erms of fasting, stopping medication, or taking medication prior to the examination. It is worth checking local policy with your nuclear medicine scan team when requesting an investi gation for your patient. SUBASH KC/NMC-15TH/2014 NUCLEAR MEDICINE (TRADITIONAL) 15 Fig. 1.8 Selected images from a V/Q scan, looking for a pulmonary embolus. Matched ventilat ion (upper row) and perfusion (lower row) in a normal scan. SUBASH KC/NMC-15TH/2014 16 CHAPTER 1 Techniques PET-CT PET-CT is a relatively new technique, rapidly developing a central role in many imag ing pathways. It involves the fusion of images from two very dif- ferent imaging modalities puted tomography (CT). The patient undergoes both scans sequentially, in the same session, and the results are merged, giving a combination of functional information from the radioi sotope PET scan and the accurate anatomical detail of CT (Figs. 1.9 and 1.10 ). \200\224 positron emission tomography (PET) and com- Technique A short-lived radioactive tracer isotope \200\224 2 \200\22318 \202 uorodeoxy- D-glucose (FDG) \200\224 is injected intravenously. This radioisotope undergoes a process known as beta-decay, emitting a positron, which when it collides with an electron produces a pair of gamma photons that are subsequently detected within a gamma camera. FDG is a glucose analog that accumulates within areas of high intracellular metabolism and glycolysis. Tumor cells are highly metabolically active, and a lso retain FDG more than do normal cells, meaning that the isotope becomes concentrated wit hin the tumor resulting in a \200\230hot spot \200\231 on the image. FDG is not cancer spe ci \201 c, however, and is taken up in all areas of high metabolic activity, such as the b rain, as well as by areas of in \202 ammation or increased muscle activity. Patient preparation \200 The patient is fasted for at least 4 \200\2236 hours prior to th e scan. \200 Plasma glucose levels should be checked before scanning. \200 An IV inject ion of FDG is administered. \200 The patient rests quietly for a period while the isotope circulates. Movement and talking are discouraged to prevent muscle uptake. Scanning begins approximately 60 minutes following the injection and the total scan time is approx. 30 \200\22390 minutes. Images are acquired from the top of the head to mid thighs, with the patient \200\231s arms above their head. Usually the CT is obtained \201 rst followed by the gamma camera image s. Because the scanners are in the same gantry the patient remains on a single scanning tab le and in the same position during both scans. Indications \200 In general, PET is better than conventional imaging at demonstrating dis tant metastases from a wide variety of tumors. It is therefore used to complete the staging in cases where more traditional tests have suggested localized disease; e.g. in lung cance r, PET has been shown to upstage a signi \201 cant proportion of patients thought on CT to be potentially operable. PET is being used to provide early assessment of tumor response to chemotherapy allowing regimens to be altered if appropriate. Also useful in early assessment of suspected disease recurrence in areas of post-treatment scarring or \201 brosis. Research roles in assessing myocardial perfusion. \200 Developing roles in neuro imaging. SUBASH KC/NMC-15TH/2014 PET-CT 17 Relative contraindications \200 Pregnancy (high-dose examination, around 20mSv). \200 U ncontrolled diabetes makes interpretation dif \201 cult. \200 Patients must be able to l ie still for considerable length of time. Fig. 1.9 oesophageal tumor (caliper). Coronal image from staging PET-CT showing increased uptake of Fig. 1.10 Image from a staging PET scan in a patient with lung cancer. Second incidental fo cus found within the left \202 ank, found to be an incidental colonic tumor. The other ar eas of increased uptake are physiological. SUBASH KC/NMC-15TH/2014 18 CHAPTER 1 Techniques Magnetic resonance imaging General principles Materials placed in a magnetic \201 eld can absorb and then re-emit electro- magnetic radiation of a speci \201 c frequency, usually in the form of radio- signals. When tissue is placed in a magnetic \201 eld (MRI scanner) the protons (hydrogen nuclei) align with the \201 eld. A radiofrequency electromagnetic \201 eld is then brie \202 y turned on, causing the protons to alter their alignment rel ative to the \201 eld. When this \201 eld is turned off the protons return to the origi nal magnetization alignment. These alignment changes create a signal which can be detected by the scanner. The frequency at which the protons resonate depends on the strength of the magnetic \201 eld. The posi- tion of protons in the body can be determined by applying ad ditional mag- netic \201 elds during the scan, which allows an image of the body to be bu ilt up. These are created by turning gradient coils on and off which creates the knocking s ounds heard during an MR scan. Protons in different tissues return to their equilibrium state at different rates. By changing the parameters on the scanner, this effect is used to create contrast be tween different types of body tissue. Various sequences can be achieved by changing imaging parameters. Basic sequences are T1, T2, T2 * , proton density, inversion recovery (short t au inversion recovery, STIR (Fig. 1.11 ); \202 uid attenuation inversion recovery, FLAIR) . More specialized sequences include diffusion-weighted imaging (DWI), MR angiography and f unctional imaging. The most widely used MR contrast agents are gadolinium chelates. Gadolin ium is a paramagnetic substance that enhances the relaxation rate of surrounding tissue the reby producing greater T1 signal i.e. \200\230bright \200\231 on T1 imaging. Applications MRI is used to image every part of the body, and is particularly useful for ne urological conditions, disorders of the muscles and joints, tumors, and for showing abnorma lities in the heart and blood vessels. While CT offers greater spatial resolution (ability to distinguish two structures a small dis- tance apart as separate structures) MRI offers g reater contrast resolution (ability to distinguish two similar, but not identical tissues). MRI does not use ionizing radiation and there are as yet no reported long-term biological e ffects from prolonged exposure to a magnetic \201 eld. This makes MRI more appropriate in children and pregnancy. There are disadvantages to MRI. Acquiring images is time consuming and scans can often last 20 \200\22340 minutes. Patients must be able to lie still for this length of time. Young children will often require a general anesthetic. Patients with clau strophobia may not tolerate MRI and sedation or alternative imaging may be required. Contraindications There are absolute contraindications: \200 Cardiac pacemakers. \200 C ochlear implants. \200 Tissue expanders. \200 Ocular prostheses. SUBASH KC/NMC-15TH/2014 MAGNETIC RESONANCE IMAGING 19 Dental implants. \200 Neurostimulators. \200 Bone growth stimulators. \200 Implantabl e cardiac de \201 brillators. \200 Implantable drug infusion pumps. New medical devices tend to be MRI compatible and MRI safe pacemakers are now available. Ot hers to consider are orthopedic implants/metalwork, vascular clips, intravascular coils and bullets/pellets/shrapnel. Most of these are safe, but they should be evaluated on a patien t-by-patient basis. More information is freely available online ( http://www.mrisafety.com ). Fig. 1.11 oedema secondary to tuberculosis. Sagittal STIR image of the cervical spine showing intra-cord abscess and SUBASH KC/NMC-15TH/2014 20 CHAPTER 1 Techniques Interventional radiology Radiological interventional techniques use image guidance such as \202 uoros- copy, ultrasound, or CT to help in a diagnostic or therapeutic procedure. The role of interventional radiology is continually expanding and there is hardly any area of hospital medicine where it does not have an impact on patient management. The advantages in clude reduced risk as compared to surgery, shorter hospital stay, lower cost, greater comfo rt, quicker conva- lescence, and return to work. Non-vascular intervention Includes diagnostic biopsies, drainage of collections, GI procedu res such as oesophageal, gastroduodenal and colonic stent placement, percutaneous gastrosto my and gastrojejunostomy insertions, biliary drainage, urological procedures such as percut aneous nephrostomy and antegrade ureteric stent placement, etc. Vascular intervention Includes procedures such as angiography (Fig. placement, thrombolysis , EVAR (endovascular aneurysm repair), tumor embolization, uterine \201 broid embolizatio n, postpartum hemorrhage management, bronchial artery embolization, Hickman line insertions , Varicocoele embolization, IVC \201 lter placement and retrieval, etc. 1.12 ), angioplasty, stent Pre-procedure preparation \200 Con \201 rm the clinical indication. \200 Check previou s imaging. \200 Check the coagulation and infection screen as per local protocols. \200 Consider use of medication such as sedatives, analgesics, etc. \200 Choose the correct i maging modality for the procedure. \200 Obtain informed consent. Ultrasound-guided procedures Ultrasound is used for various biopsy and drainage procedures. It is ideal if the target is clearly visible and a suitable approach is possible. The adva n- tages of using ultrasound are that procedure is performed in real time, it can be done p ortably in ICU etc, and does not involve ionizing radiation. The procedure can be performed using a needle guide attached to the ultrasound probe, which shows the path the needle will take. Another method is to use a fre ehand technique wherein the probe is \201 xed with one hand and the needle is advanced in to the target with the other. The latter technique is more dif \201 cult and requires expe rtise. CT-guided intervention When it is not possible to access the target using ultrasound guidan ce (e.g. pathology within lung, related to bowel, etc.), CT guidance may be used. The punct ure site is marked following a reference scan. Needle path to the target is planned. After each needle pass, the patient goes into the scanner and is then brought out again making th e procedure more \200\230stop/ start \200\231 and time consuming than when using US. Once the needle is in a satisfactory position, the appropriate procedure is performed. SUBASH KC/NMC-15TH/2014 INTERVENTIONAL RADIOLOGY 21 Aftercare This varies with the type of procedure, the general condition of patient, the coa gulation status, etc. Depending on local protocols the procedure may be performed as a dayc ase and all aftercare takes place in the radi- ology department, or the patient may be retu rned to a ward in which case a written aftercare plan should go with them. It should always be mentioned if the procedure was dif \201 cult or if there were any immediate complicati ons. Complications These vary with the type and site of procedure, and between individual patien ts. Serious complications are rare. Following are some of the impor- tant complications to look out for: \200 Bleeding. \200 Infection. \200 Bowel perforation. \200 Pneumotho rax. Most complications can be managed adequately but need to be thought about and recognized ea rly. Useful information for the radiologist Detailed clinical history and clinical differential diagnosis, coagulation status, and infection screen. If the patient is uncooperative or ext remely anxious then may need to consider pre-medications or sedation. Fig. 1.12 endovascular repair of their abdominal aortic aneurysm. The stents can be clearly seen. Image from a vascular angiography study in a patient who has undergone SUBASH KC/NMC-15TH/2014 This page intentionally left blank SUBASH KC/NMC-15TH/2014 23 Chapter 2 Respiratory differential diagnosis Focal consolidation 24 Widespread consolidation White out 24 Solitary lung mass 24 Multiple lung masses Pleural effusion 25 Cardiomegaly 25 Unilateral hyperradiancy 25 Bilateral hype rradiancy Upper zone \201 brosis 26 Small \201 brotic lungs 26 Kerley B lines 26 Bilate ral hilar enlargement Unilateral hilar enlargement 26 24 25 25 26 SUBASH KC/NMC-15TH/2014 24 CHAPTER 2 Respiratory differential diagnosis Focal consolidation \200 Pneumonia. \200 Hemorrhage. \200 Contusion. \200 Alveolar cell carcinoma. \200 Cryptogenic organizing pneumonia. \200 Lymphoma. Widespread consolidation \200 Infection. \200 Oedema. \200 Pulmonary hemorrhage. \200 Tumor: \200 BAC. \200 Lymphoma. \200 Widespread metastases. Proteinosis. \200 Alveolitis. \200 Cryptogenic organizing pneumonia. \200 Eosinophili c pneumonia. White out \200 Mediastinum shifted toward white out: Collapsed lung. \200 Pneumonectomy. Mediastinum shifted away from white out: Pleural \202 uid. \200 Large mass. Mediastinum central: Combination of collapse and \202 uid. \200 Widespread consolidation. \200 Pleural tum or. Solitary lung mass \200 Primary lung cancer. \200 Solitary metastasis. \200 Lymphoma. \200 Benign tumor: \200 Carcinoid. \200 Hamartoma. Arteriovenous malformation (AVM). \200 Post-infective scar/granuloma. \200 Round pneumo nia. \200 Rheumatoid nodule (usually multiple). \200 Infarct. SUBASH KC/NMC-15TH/2014 BILATERAL HYPERRADIANCY 25 Multiple lung masses \200 Multiple metastases. \200 Vasculitis. \200 Rheumatoid nodul es. \200 Multiple emboli. \200 Multi focal infection. \200 Progressive massive \201 brosis (PMF). Pleural effusion \200 Large, unilateral. \200 Mesothelioma. \200 Metastatic pleural t umor. \200 Empyema. Small/moderate, unilateral: Parapneumonic (associated with consolidation). \200 Empyema. \200 Malignancy (as above) . Bilateral: Heart failure. \200 Fluid overload. \200 Hypoalbuminaemia. Cardiomegaly \200 LV failure. \200 Pericardial effusion. Unilateral hyperradiancy \200 Rotation of the patient. \200 Pneumothorax. \200 Chest wall abnormality: Mastectomy. \200 Poland \200\231s syndrome. Bilateral hyperradiancy \200 Bilateral pneumothorax. \200 Over expanded lungs: Chronic obstructive pulmonary disease (COPD). \200 Asthma. SUBASH KC/NMC-15TH/2014 26 CHAPTER 2 Respiratory differential diagnosis Upper zone \201 brosis \200 Sarcoid. \200 Tuberculosis (TB). \200 Post radiation. \200 Pneumoconiosis. \200 Extrinsic allergic alveolitis (EAA; chronic). \200 Ankylosin g spondylitis. Small \201 brotic lungs \200 Idiopathic pulmonary \201 brosis. \200 Drug-induced \201 brosis. \200 Asbestosis. \200 Connective tissue disease. Kerley B lines \200 Heart failure. \200 Lymphangitis. \200 Sarcoid. Bilateral hilar enlargement \200 Sarcoid. \200 Pulmonary hypertension. \200 Lymphoma. Unilateral hilar enlargement \200 Lung cancer. \200 TB. \200 Infection. SUBASH KC/NMC-15TH/2014 27 Chapter 3 Respiratory presenting syndromes Chest pain 28 Wheeze 30 Shortness of breath 32 Cough 34 Haemoptysis 36 Hypoxia 38 SUBASH KC/NMC-15TH/2014 28 CHAPTER 3 Respiratory presenting syndromes Chest pain This symptom is associated with a variety of disease processes, many of which ar e common and potentially life threatening. A possible myocardial infarction must be the \201 rst consideration in all adults with acute chest pain. Once this has been excluded, th e list of differential diagnoses can be narrowed by accurate interpretation of history, exa mination, and investigations (Table 3.1 ). Investigations These will be guided by the presentation and likely diagnosis. In general, a n electrocardiogram (ECG) is required to rule out cardiac ischaemia/infarction as well as a plain chest radiograph. A summary of available imaging tests relevant in the investigation of chest pain are brie \202 y described in the \200\230Imaging \200\231 section. More de tailed applications and \201 ndings will be discussed under each relevant condition. Imaging Plain chest radiograph This may prove to be diagnostic. It may show signs of cardia c failure, pneu- mothorax, or collapse/consolidation. Mediastinal widening, shift, and the presence of free gas can all be detected. Ultrasound Ultrasound examination of the heart (echocardiography) can be used to detect aor tic arch aneurysms, dissecting aneurysms, cardiomayopathy and pericardial effusion. Transoe sophageal echocardiography (TOE) has been developed to overcome limitations of conventional echocardiography in trying to image through the anterior chest wall. Ultrasound examination of the chest can be used to detect the presence of pleural \202 uid and to guide aspiration/drainage. CT Can be used to evaluate/diagnose dissecting thoracic aneurysms, pericar- dial effusions, and myocardial tumors. More advanced scanners allow non-invasive assessment of the coronar y arteries. Recent NICE guidelines recommend unenhanced CT to assess coronary artery calci \201 cation in cases of atypical chest pain. Respiratory causes of chest pain can be evaluated with CT, including CT pulmonary angiograp hy (CTPA) for suspected cases of pulmonary embolism. CT also allows evaluation of the pleural space and chest wall. Nuclear medicine Thallium ( Not used in the acute setting but can differentiate viable from non-viable myocardium and hence identify those patients who would bene \201 t from corona ry revascularization. Following injection with formed immediately after exercise and then r epeated 4 hours later. 201 TI) exercise test 201 TI, imaging is per- SUBASH KC/NMC-15TH/2014 CHEST PAIN 29 Ventilation/perfusion imaging Combined perfusion scanning with technetium-99m-labeled macro aggre- gates of human albumin and ventilation scanning with inhaled radioactive gas or aero sol to assess possible pulmonary embolus. MRI Little role in acute setting. Has some value in assessing pericardial effusions, hypert rophic cardiomyopathy, and congenital/valvular heart disease. MR angiography provides a non -invasive method of imaging vascular abnor- malities such as aneurysm and dissection, but d oes not have the spatial resolution necessary to assess the coronary arteries. Arteriography Coronary angiography This is a commonly performed examination during which co ntrast is ini- tially injected into the left ventricle to evaluate function, and subsequent ly into the coronary arteries to demonstrate the extent of any stenoses or occlusion. Angio plasty and stenting can then be performed if indicated. Pulmonary angiography This is an invasive procedure which is now rarely performed since the advent of CTPA. It involves selective catheterization of the pulmonary artery (either thro ugh the jugular or femoral vein) and contrast injection to visualize the pulmonary circulat ion. Table 3.1 Differential diagnosis Cardiac Pulmonary Other Myocardial ischaemia/ * infarction Pneumothorax Oesophageal rupture with mediastinitis Aortic dissection Pulmonary * embolus Pancreatitis Pericarditis Pneumonia Oesophagitis Myocarditis Lung cancer Cholecystitis Mitral valve prolapse Mesothelioma Herpes zoster (shingles) Pleural effusion Costochondritis (Tietze \200\231s disease) Vertebral collapse Trauma Potentially rapidly life threatening SUBASH KC/NMC-15TH/2014 30 CHAPTER 3 Respiratory presenting syndromes Wheeze Wheeze is the sound produced by the vibration of narrowed airways. Normally heard be st in expiration, wheeze can be either polyphonic, with multiple different pitches and volu mes, or monophonic with a single constant pitch. Wheeze which can only be heard in inspiration is termed stridor and is indicative of an upper respiratory tract cause. A localized or \201 xed wheeze is suspicious of tumor or foreign body within an airway. Polyphonic wheeze \200 Asthma. \200 COPD. \200 Cardiac failure. \200 Anaphylaxis. \200 Extrinsic allergic alveolitis (EAA). \200 Chondromalacia. \200 Pneumonia (less co mmon). Monophonic wheeze \200 Bronchial carcinoma. \200 Foreign body. Stridor \200 Anaphylaxis. \200 Peritonsilar or retropharyngeal abscess. \200 Epiglott itis/croup. \200 Foreign body. \200 Pharyngeal pouch. \200 Thyroid goiter. \200 Upp er respiratory tract neoplasm. \200 Vocal cord paralysis. \200 Rarely congenital vascul ar abnormalities/rings in children. Imaging In acute life-threatening airway obstruction imaging is a distraction. The patient requires urgent clinical management. Once the patient is stabilized imaging may play a role . Plain \201 lm \200 Chest x-ray (CXR) can identify tumor, foreign bodies, cardiac failur e, or infection. Background conditions such as COPD may be evident. \200 In acute asthma the CXR may be no rmal or show only large volume lungs, but is useful to exclude pneumothorax or exacerbating conditions such as infection. A lateral cervical spine x-ray may identify radio-opaque foreign bodies or rarely a \202 uid level in a retropharyngeal abscess. SUBASH KC/NMC-15TH/2014 WHEEZE 31 CT \200 CT of neck and chest may reveal extrinsic airway compression by mass lesions, end oluminal lesions within the airways, or congenital abnormalities. Expiratory CT can demonstrate focal areas of air trapping in patients with small airways di sease and collapse of the larger airways in those with bronchomalacia. Ultrasound Ultrasound is not routinely used to investigate wheeze. Neck masses such as node s or goiter can be assessed. Fluoroscopy /nuclear medicine/MRI These are not routinely used. However a barium swallow wi ll diagnose a pharyngeal pouch or identify extrinsic oesophageal compression which may indi cate pathology such as vascular rings that are also causing airway compression. Information for the radiologist \200 Any history of background lung conditions. \200 Ha s a foreign body been inhaled (some are not radio-opaque)? \200 Location of the wheeze. \200 Any history of smoking, cancer, or congenital abnormality. \200 Respiratory functio n tests. \200 Is there a seasonal picture or anything to suggest allergy? SUBASH KC/NMC-15TH/2014 32 CHAPTER 3 Respiratory presenting syndromes Shortness of breath A common problem with a wide range of causes. The key to narrowing the differential diagnosis lies in accurate history taking and examination. Presentation Presentation varies according to the cause. Associated symptoms should be elic ited. The duration of illness is helpful to narrow the differential diagnosis: \200 Sudde n onset (over minutes): Pneumothorax: pleuritic chest pain. May be a history of trauma. \200 Myocardial infarctio n: chest pain, sweating, clammy. \200 Pulmonary embolus: pleuritic chest pain, haemoptysi s, syncope. \200 Inhaled foreign body: often in children, cyanosis, stridor. \200 Anaph ylaxis: stridor, tongue/throat swelling, urticarial rash. Acute (onset over hours): Asthma: expiratory wheeze, chest pain. \200 Pneumonia: fever, productive cough, coarse cr epitations. \200 Pulmonary oedema: widespread inspiratory crepitations. \200 Cardiac ta mponade: muf \202 ed heart sounds, raised jugular venous pressure (JVP), hypotension. Metabolic acidosis: e.g. diabetic ketoacidosis. Check glucose, arterial blood gasses (ABG). Inappropriate hyperventilation. Chronic (onset over months): Asthma. \200 COPD: history of smoking, wheeze and recurrent chest infections. \200 Inte rstitial lung disease: e.g. idiopathic pulmonary \201 brosis. \200 Heart failure: worse on exertion, orthopnoea, peripheral oedema. \200 Pulmonary hypertension: chest pain, fat igue, right heart failure. \200 Lung cancer: weight loss, cough, haemoptysis, smoking his tory. \200 Anemia: pallor. Check full blood count (FBC). Adjuncts to clinical examination include ECG, ABG, routine blood tests, and pulse oximetry. Imaging Plain \201 lm CXR is the initial imaging investigation. It may identify many of t he acute causes, e.g. pneumothorax, pleural effusion, cardiac failure, pneumonia. Also usef ul to compare with old radiographs in cases of chronic dyspnoea. CT Occasionally required if the diagnosis cannot be made on plain \201 lm. Performed as h igh resolution CT (HRCT), CTPA, or normal contrast enhanced CT depending on the clinical qu estion. Nuclear medicine V/Q scans are used to identify pulmonary emboli. SUBASH KC/NMC-15TH/2014 SHORTNESS OF BREATH 33 Ultrasound May demonstrate pleural or pericardial effusions. Information for the radiologist \200 Presenting symptoms and duration of illness. \200 Relevant past medical history, e.g. cardiac disease, smoking, allergy. \200 Clinical diff erential diagnosis. SUBASH KC/NMC-15TH/2014 34 CHAPTER 3 Respiratory presenting syndromes Cough Cough is a common presenting complaint and there are a wide range of causes, of which upper respiratory tract infection is the most common. Presentation Presentation varies according to the cause. The nature of the cough should be explored: \200 Duration: acute or chronic (see later in topic). \200 Productivity: dry, sputum, blood. \200 Timing: e.g. worse in early morning (asthma), following food (re \202 ux). \200 Environmental precipitants: e.g. drugs, pets, smoking, exercise. Associated symptoms may include nasal discharge, fever, wheeze, dysp- noea, peripheral oede ma, weight loss, or recurrent chest infections and provide important clues as to the underl ying etiology. The duration of symptoms can be used to classify causes: Acute (<3 weeks): Upper respiratory tract infection. \200 Lower respiratory tract infection and pneumonia. \200 Airway disease: e.g. asthma, COPD. \200 Heart failure. \200 Aspiration. \200 E xtrinsic allergic alveolitis: e.g. pigeon fancier \200\231s lung. \200 Pulmonary embolus. > 3 weeks): Chronic ( Post-nasal drip. \200 Airway disease: COPD, asthma, lung cancer, bronchiectasis. \200 I nterstitial lung disease. \200 Extrinsic allergic alveolitis. \200 Heart failure. \200 Gastro-oesophageal re \202 ux disease with recurrent aspiration. \200 Drugs: e.g. angi otensin converting enzyme (ACE) inhibitors. Imaging Plain \201 lm Recommended if symptoms last 3 weeks or more. A good screening tool if there is concern for a pulmonary or cardiac cause. CT Persistent cough is sometimes investigated with CT, particularly if there is concern for malignancy, bronchiectasis, or interstitial lung disease. Ultrasound Echocardiography is a reliable method of assessing cardiac function. Fluoroscopy Contrast swallow examinations can demonstrate gastro-oesophageal re \202 ux an d aspiration. SUBASH KC/NMC-15TH/2014 COUGH 35 Information for the radiologist \200 Nature of cough and associated symptoms. \200 Rele vant environmental history e.g. pets, occupational history, smoking. SUBASH KC/NMC-15TH/2014 36 CHAPTER 3 Respiratory presenting syndromes Haemoptysis Haemoptysis is the coughing up of blood from the lungs or tracheobron- chial tr ee (Table 3.2). Massive haemoptysis refers to the coughing up of > 200ml of blood in 24 hou rs. Imaging The cause of haemoptysis may be obvious from the history and investiga- tions shoul d be performed according to the likely diagnosis. Plain \201 lm This should be performed in all patients presenting with haemoptysis. It ma y reveal a mass lesion, mediastinal lymphadenopathy, bronchiectasis, cavitation, consolidat ion, or pulmonary oedema. Ultrasound Ultrasound examination of the heart (echocardiography) can be used to detect car diac causes of haemoptysis including anatomical abnormalities, valvular disease, and ventri cular dysfunction. CT CT of the chest may identify parenchymal or endobronchial lesions, or further characteri ze abnormalities seen on plain chest radiograph. HRCT is performed where generalized lung disease is suspected (e.g. bronchiectasis). Tradit ional intermittent HRCT uses widely spaced, thin sections and is therefore unsuitable for t he assessment of lung cancer or other localized lung diseases. Similarly, IV contrast agent s are not routinely administered making the technique unsuitable for assessment of soft tis sues and blood vessels. CTPA is commonly performed for suspected pulmonary embolism. In this test, iodinated contra st is administered intravenously to opacify the pulmonary arterial tree. Any \201 lling d efects indicate the presence of a pulmonary embolus. In cases of massive haemoptysis contrast enhanced CT can be useful in identifying enlarged bronchial arteries which may be suitable for embolization. Nuclear medicine V/Q imaging should be considered for patients with suspected pulmonary emb olism who have a normal chest radiograph and no known history of respiratory disease. Combi ned perfusion scanning with technetium- 99m-labeled macroaggregates of human albumin and ve ntilation scanning with inhaled radioactive gas or aerosol typically produces a perfusion d efect and not a ventilation defect in pulmonary embolus. MRI The lungs are not well visualized with MR and its use in the assessment of respiratory causes of haemoptysis is limited. SUBASH KC/NMC-15TH/2014 HAEMOPTYSIS 37 Angiography Pulmonary angiography can identify the bleeding source in 90 with massive haemo ptysis and can be combined with embolization of the bleeding vessel. % of patients Other Fibreoptic bronchoscopy may be used in cases of suspected malignancy. It is diagnosti c for central endobronchial lesions and allows direct visualiza- tion of the bleeding site. In cases of more peripheral bleeding the broncho- scopist may be able to identify the affe cted lobe, which is useful information for a vascular radiologist considering embolization. It also permits tissue biopsy, bronchial lavage, or brushings for pathological diagnosis. Table 3.2 Differential diagnosis Pulmonary Cardiac Systemic vasculitis Bronchiectasis Pulmonary embolus Systemic lupus erythematosus (SLE) Bronchogenic carcinoma Left ventricular failure Wegener \200\231s granulomatosis Infection Mitral stenosis Goodpasture \200\231s syndrome TB Pulmonary hypertension Pneumonia Aortic aneurysm (aorto-bronchial \201 stula) Lung abscess Aspergilloma Trauma AV malformation SUBASH KC/NMC-15TH/2014 38 CHAPTER 3 Respiratory presenting syndromes Hypoxia Hypoxia is de \201 ned as reduced oxygen supply to tissues despite adequate blood supply. Possible causes are listed: 1. Reduced oxygen carrying capacity \200 Anemia. \200 Carbon monoxide poisoning. \200 Haemoglobinopathies (e.g. sickle cell, thalassaemia). 2. Reduced blood supply to lungs \200 Pulmonary embolism (thrombus, fat, amniotic). \200 Right-sided heart failure. \200 Pulmonary hypertension. \200 Pulmonary valve stenosis . \200 Congenital heart disease. 3. Reduced diffusion of oxygen across the alveolar membrane \200 Upper airway obstruction (e.g. foreign body). \200 Lower airway pathology (e.g. asthma/COPD/tumor). \200 Materi al within alveoli: In \202 ammatory cells (infection/hypersensitivity). \200 Pulmonary hemorrhage. \200 P ulmonary oedema. \200 Tumor. Interstitial lung disease/ \201 brosis. \200 Bronchiectasis/cystic \201 brosis. \200 Collapse of lung due to pneumothorax or pleural effusion. \200 Neuromuscular disorders ( e.g. Guillain \200\223Barr syndrome). Imaging Plain \201 lm \200 A CXR is likely to be the \201 rst form of imaging used to investigate the hypoxic patient. It is most useful for the 3 earlier. rd category of causes listed Cardiac and mediastinal abnormalities may suggest a cause from the 2 nd category. Remember CXR signs may lag behind the clinical \201 ndings. CT \200 Standard CT thorax \200 CTPA is the investigation of choice for detecting pulmo nary emboli. \200 HRCT acquires 1mm slices to assess the structures of the small airways contrast provides detailed 3D information. and interstitium. Used in the diagnosis of interstitial lung disease and atypical infection . Cardiac CT assesses cardiac structure and function; however is usually performed after an echocardiogram. SUBASH KC/NMC-15TH/2014 HYPOXIA 39 Ultrasound \200 Ultrasound can con \201 rm pleural effusions or pneumothorax prior to guided intervention. Echocardiography evaluates cardiac structure and function. Nuclear medicine V/Q scanning can be used to investigate pulmonary embolism if imme- diatel y available but should only be used in those patients with a normal CXR and no previous car diorespiratory disease. MRI Cardiac MRI assesses structure and function of the heart but is usually a second-line e xamination. Information for the radiologist \200 Relevant history including previous respiratory dise ase, smoking, immunosuppression, malignancy, or previous surgery. A differential diagnosis is vital to choose the most appropriate investigation. SUBASH KC/NMC-15TH/2014 This page intentionally left blank SUBASH KC/NMC-15TH/2014 41 Chapter 4 Respiratory conditions Lung abscess 42 Pneumonia 44 Emphysema/COPD 46 Pulmonary embolus 48 Left ventricular failur e Pneumothorax 54 Wegener \200\231s granulomatosis 56 Pulmonary hypertension Solitary pulmo nary nodule 60 Lung cancer 62 Lobar collapse 64 Bronchiectasis 70 Cystic \201 brosis 72 P leural effusion 74 Interstitial lung disease 76 Connective tissue disease and the lung Pneu moconiosis 80 Sarcoidosis 82 Benign asbestos-related disease Tuberculosis 86 Malignant pleu ral disease Mediastinal masses 52 58 78 84 88 90 SUBASH KC/NMC-15TH/2014 42 CHAPTER 4 Respiratory conditions Lung abscess A lung abscess is a well-de \201 ned collection of pus, usually with a discre te wall and surrounded by in \202 amed lung tissue. They usually develop as a complication of bacterial pneumonia and may be solitary or multiple. Clinical presentation The clinical course is often insidious, with fever, lethargy, and nig ht sweats. Breathlessness and productive cough with haemoptysis may be present. \200 If d ue to aspiration, abscesses often involve the posterior segments of the upper lobes and the apical segments of the lower lobes, as these areas are gravity depe ndent when the patient is supine.