SUBASH KC/NMC-15TH/2014 OXFORD MEDICAL PUBLICATIONS Oxford Handbook of Medical Imaging SUBASH KC/NMC-15TH/2014 Published and upcoming Oxford Handbooks Oxford Handbook for the Foundation Program 3e Oxfor d Handbook of Acute Medicine 3e Oxford Handbook of Anesthesia 3e Oxford Handbook of Applied Dental Sciences Oxford Handbook of Cardiology Oxford Handbook of Clinical and Laboratory I nvestigation 3e Oxford Handbook of Clinical Dentistry 5e Oxford Handbook of Clinical Diagno sis 2e Oxford Handbook of Clinical Examination and Practical Skills Oxford Handbook of Clin ical Hematology 3e Oxford Handbook of Clinical Immunology and Allergy 2e Oxford Handbook of Clinical Medicine \200\224Mini Edition 8e Oxford Handbook of Clinical Medicine 8e Oxford H andbook of Clinical Drugstore Oxford Handbook of Clinical Rehabilitation 2e Oxford Handbook of Clinical Specialties 8e Oxford Handbook of Clinical Surgery 3e Oxford Handbook of Compl ementary Medicine Oxford Handbook of Critical Care 3e Oxford Handbook of Dental Patient Car e 2e Oxford Handbook of Dialysis 3e Oxford Handbook of Emergency Medicine 3e Oxford Handboo k of Endocrinology and Diabetes 2e Oxford Handbook of ENT and Head and Neck Surgery Oxford Handbook of Expedition and Wilderness Medicine Oxford Handbook of Gastroenterology & Hepato logy 2e Oxford Handbook of General Practice 3e Oxford Handbook of Genetics Oxford Handbook of Genitourinary Medicine, HIV and AIDS 2e Oxford Handbook of Geriatric Medicine Oxford Han dbook of Infectious Diseases and Microbiology Oxford Handbook of Key Clinical Evidence Oxfo rd Handbook of Medical Dermatology Oxford Handbook of Medical Sciences Oxford Handbook of M edical Statistics Oxford Handbook of Nephrology and Hypertension Oxford Handbook of Neurolo gy Oxford Handbook of Nutrition and Dietetics 2e Oxford Handbook of Obstetrics and Gynecolo gy 2e Oxford Handbook of Occupational Health Oxford Handbook of Oncology 3e Oxford Handbook of Ophthalmology 2e Oxford Handbook of Pediatrics Oxford Handbook of Pain Management Oxfor d Handbook of Palliative Care 2e Oxford Handbook of Practical Drug Therapy 2e Oxford Handbo ok of Pre-Hospital Care Oxford Handbook of Psychiatry 2e Oxford Handbook of Public Health P ractice 2e Oxford Handbook of Reproductive Medicine & Family Planning Oxford Handbook of Re spiratory Medicine 2e Oxford Handbook of Rheumatology 3e Oxford Handbook of Sport and Exerc ise Medicine Oxford Handbook of Tropical Medicine 3e Oxford Handbook of Urology 2e SUBASH KC/NMC-15TH/2014 Oxford Handbook of Medical Imaging Edited by Michael J. Darby Consultant Radiologist Leeds Teaching Hospitals NHS Trust Leeds, UK Dominic A. Barron Consultant Radiologist Leeds Teaching Hospitals NHS Trust Leeds, UK Rachel E. Hyland Consultant Radiologist Leeds Teaching Hospitals NHS Trust Leeds, UK 1 SUBASH KC/NMC-15TH/2014 1 Great Clarendon Street, Oxford OX2 6DP Oxford University Press is a department of the University of Oxford. It furthers the Univer sity \200\231s objective of excellence in research, scholarship, and education by publishin g worldwide in Oxford New York Auckland Cape Town Dar es Salaam Hong Kong Karachi Kuala Lumpur Madrid Melbourne Mexico Cit y Nairobi New Delhi Shanghai Taipei Toronto With of \201 ces in Argentina Austria Brazil Chile Czech Republic France Greece Guatemala Hungary Italy Japan P oland Portugal Singapore South Korea Switzerland Thailand Turkey Ukraine Vietnam Oxford is a registered trade mark of Oxford University Press in the UK and in certain other countries Published in the United States by Oxford University Press Inc., New York Oxford University Press, 2012 The moral rights of the authors have been asserted Database right Oxford University Press ( maker) First published 2012 All rights reserved. No part of this publication may be reproduced, stored in a retrieval s ystem, or transmitted, in any form or by any means, without the prior permission in writing of Oxford University Press, or as expressly permitted by law, or under terms agreed with t he appropriate reprographics rights organization. Enquiries concerning reproduction outside the scope of the above should be sent to the Rights Department, Oxford University Press, a t the address above You must not circulate this book in any other binding or cover and you must impose the same condition on any acquirer British Library Cataloging in Publication Data Data available Library of Congress Cataloging-in-Publication Data Darby, Michael (Michael J.) Oxford handb ook of medical imaging/Michael Darby, Dominic Barron, Rachel Hyland. p. ; cm. \200\224(Oxford handbooks) Handbook of medical imaging Includes index. ISBN 978 \200\2230 \200\22319 \200\223921636 \200\2239 (alk. paper) I. Barron, Dominic. II. Hyland, Rachel. III. Title. IV. Title: Handb ook of medical imaging. V. Series: Oxford handbooks. [DNLM: 1. Diagnostic Imaging \200\224H andbooks. WN 39] LC classi \201 cation not assigned 616.07 \200\23157 \200\224dc23 2011033024 Typeset by Cenveo, Bangalore, India Printed in China on acid-free paper through Asia Paci \201 c Offset ISBN 978 \200\2230 \200\22319 \200\223921636 \200\2239 10 9 8 7 6 5 4 3 2 1 SUBASH KC/NMC-15TH/2014 v Preface Radiology is becoming more and more important in the initial diagnosis, follow up, and, inc reasingly, the treatment of patients. At the same time it becomes more complex, and covers every anatomical and organ system group. This book is written using a system-based approach, covering the various modalities and exp laining their relevance in each situation. For each system there are three separate section s. The \201 rst deals with common presenting symptoms, listing the most likely diagnoses. There is then a review of the imaging approach to each of these presenting conditions and the value of each modality. The second section lists the common radiological \201 ndings which may be encountered and the differential diagnoses which need to be considered. The \201 nal section discusses in detail a number of common conditions. Using this approach, the authors hope that this book will help to guide junior doctors and other professionals through the increasingly varied roles imaging can play in the managemen t of their patients. With a book of this size, it is impossible to include all known conditions. The authors hav e concentrated on those conditions which are either common, or of such importance that any delay in diagnosis may be signi \201 cant. The authors would value feedback on the text which could lead to improvements being made in future editions. SUBASH KC/NMC-15TH/2014 vi Acknowledgements In preparing the text, the authors are aware that many of the lists, statis- tics used, and radiological signs described have previously been published. Acknowledgement is made to th e following texts: Chapman S. Nakielny R. Aids to Radiological Differential Diagnosis , 5th edition. Philadelp hia: WB Saunders, 2009. D hnert W. Radiology Review Manual , 7th revised international edition. Baltimore: Lippinc ott Williams & Wilkins, 2011. SUBASH KC/NMC-15TH/2014 vii Contents Contributors ix Symbols and abbreviations xi 1 Techniques 1 2 Respiratory differential diagnosis 23 3 Respiratory presenting syndromes 2 7 4 Respiratory conditions 5 Vascular differential diagnosis 6 Vascular presenting syndrome s 7 Vascular conditions 8 Neurology differential diagnosis 9 Neurology presenting syndromes 10 Neurology conditions 11 Head and neck differential diagnosis 169 12 Head and neck prese nting syndromes 171 13 Head and neck conditions 14 Genitourinary differential diagnosis 199 15 Genitourinary presenting syndromes 203 16 Genitourinary conditions 17 Musculoskeletal d ifferential diagnosis 257 18 Musculoskeletal presenting syndromes 259 19 Musculoskeletal co nditions 265 20 Trauma 311 21 Gastrointestinal differential diagnosis 341 22 Gastrointestin al presenting syndromes 345 23 Gastrointestinal conditions 41 93 97 101 133 137 141 175 215 357 SUBASH KC/NMC-15TH/2014 viii CONTENTS 24 Breast differential diagnosis 25 Breast conditions 413 415 Index 431 SUBASH KC/NMC-15TH/2014 ix Contributors Raneem Albazaz SpR Leeds Bradford Radiology Training Scheme, UK Nalinda Panditaratne SpR Leeds Bradford Radiology Training Scheme, UK Anu Balan Consultant Radiologist Addenbrookes Hospital Cambridge University Hospitals NHS F oundation Trust Cambridge, UK Sabrina Rajan SpR Leeds Bradford Radiology Training Scheme, UK Emma Rowbotham SpR Leeds Bradford Radiology Training Scheme, UK Priya Bhatnagar Leeds Teaching Hospitals NHS Trust, Leeds, UK Nisha Sharma Director of Breast Screening Leeds/Wake \201 eld Breast Screening unit, UK Robert Briggs Consultant Radiologist Calderdale and Hudders \201 eld NHS Foundation Trust, UK Stephen Slater SpR Leeds Bradford Radiology Training Scheme, UK Barbara Dall Consultant Breast Radiologist Leeds Teaching Hospitals NHS Trust Leeds, UK Gemma Smith Consultant Radiologist Bradford Teaching Hospitals NHS Foundation Trust, UK Karen Flood SpR Leeds Bradford Radiology Training Scheme, UK Manil Subesinghe SpR Leeds Bradford Radiology Training Scheme, UK Nerys Forrester SpR Leeds Bradford Radiology Training Scheme, UK Sophie Swinson SpR Leeds Bradford Radiology Training Scheme, UK Shishir Karthik SpR Leeds Bradford Radiology Training Scheme, UK Stuart Viner Consultant Radiologist Bradford Teaching Hospitals NHS Foundation Trust, UK Amit Lakkaraju Musculoskeletal Radiology Fellow Royal Liverpool Hospital Prescott St, Liver pool, UK SUBASH KC/NMC-15TH/2014 Oxford University Press makes no representation, express or implied, that the drug dosages in this book are correct. Readers must therefore always check the product information and c linical procedures with the most up-to-date published product information and data sheets p rovided by the manufacturers and the most recent codes of conduct and safety regulations. T he authors and publishers do not accept responsibility or legal liability for any errors in the text or for the misuse or misap- plication of material in this work. Except where othe rwise stated, drug doses and recommendations are for the non-pregnant adult who is not brea stfeeding. SUBASH KC/NMC-15TH/2014 xi Symbols and abbreviations b 8 A B G 2D 3D ABG ACE AP AS ASD ATN AV AVF AVM AVN BSO Ca CC CEA CM CMCJ COPD CRP CT C TA CTPA CTU CXR DCBE DCM DIPJ DMSA DRE cross-reference approximately with or without alpha beta gamma 2-dimensional 3-dimensional arterial blood gasses angiotensin converting enzyme anteroposterior aortic stenosis atrial septal defect acute tubular necrosis arteriovenous arteriovenous \201 stula arteriovenous malformation avascular necrosis bilateral salpingo-oophorectomy calcium craniocaudal carci noembryonic antigen cardiomyopathy carpometacarpal joint chronic obstructive pulmonary dise ase C-reactive protein computed tomography computed tomography angiography computed tomogra phy pulmonary angiography CT urogram chest X-ray double-contrast barium enema dilated cardi omyopathy distal interphalangeal joint dimercaptosuccinic acid digital rectal examination SUBASH KC/NMC-15TH/2014 xii SYMBOLS AND ABBREVIATIONS DTPA DVT DWI EAA ECG EF e.g. ERCP ESR EUS FAST diethylene triamine pentaacetic acid deep vein thrombosis diffusion-weighted imaging extrin sic allergic alveolitis electrocardiogram ejection fraction for example endoscopic retrogra de cholangiopancreatography erythrocyte sedimentation rate endoscopic ultrasound focused as sessment with sonography for trauma arm speech test full blood count \202 uorodeoxy-D-glu cose International Federation of Gynecology and Obstetrics \202 uid attenuated inversion recovery Glasgow Coma Score germ cell tumor gastrointestinal genitourinary hepatocellular c arcinoma human chorionic gonadotropin hypertrophic cardiomyopathy hyperparathyroidism high resolution computed tomography hormone replacement therapy Houns \201 eld unit intermenstr ual bleeding international normalized ratio intravenous inferior vena cava intravenous urog ram jugular venous pressure kilo-electron volts kidneys, ureters, bladder large-bowel obstr uction liver function tests last menstrual period lymph node left ventricular failure or face Fbc FDG FIGO FLAIR GCS GCT GI GU HCC HCG HCM HPT HRCT HRT HU IMB INR IV IVC IVU JVP keV KUB LBO LFT LMP LN LVF SUBASH KC/NMC-15TH/2014 SYMBOLS AND ABBREVIATIONS xiii ml mg m/s MAG3 MC&S MCPJ MCUG MDP Mg MHz MI MIBG MLO MR MRCP MRE MRI MS mSv NCCT NG NICE NJ NSAID OGD OHCM PA PACS PCD PCI PDA PET PIPJ PMB PMF PSA RCM RTA SAH SBFT milliliter/s milligram/s meters per second mercapto acetyl triglycerine microscopy, cultur e, and sensitivity metacarpophalangeal joint micturating cystourethrogram methyl-di-phospho nate magnesium megahertz myocardial infarction metaiodobenzylguanidine mediolateral oblique magnetic resonance or mitral regurgitation magnetic resonance cholangiopancreatography mag netic resonance enterography magnetic resonance tomography mitral stenosis millisievert non -contrast computed tomography nasogastric National Institute for Health and Clinical Excell ence nasojejunal non-steroidal anti-in \202 ammatory oesophagogastroduodenoscopy Oxford Ha ndbook of Clinical Medicine posteroanterior picture archive communication systems periphera l vascular disease primary percutaneous intervention patent ductus arteriosus positron emis sion tomography proximal interphalangeal joint postmenopausal bleeding progressive massive \201 brosis prostate speci \201 c antigen restrictive cardiomyopathy road traf \201 c a ccident subarachnoid hemorrhage small bowel follow through , eighth edition (2010) SUBASH KC/NMC-15TH/2014 xiv SYMBOLS AND ABBREVIATIONS SLE SPECT SSRI SUV TA TB Tc TCC TMN TOE TRUS TURP TV U&E UC Uro UTI VQ VSD WCC systemic lupus erythematosus single-photon emission computed tomography selective serotonin reuptake inhibitor standardized uptake value transabdominal tuberculosis technetium transi tional cell cancer tumor, node, metastasis transoesophageal echocardiography transrectal ul trasound transurethral resection prostate transvaginal urea and electrolytes ulcerative col itis urological urinary tract infection ventilation/perfusion ventricular septal defect whi te cell count SUBASH KC/NMC-15TH/2014 1 Chapter 1 Techniques Plain \201 lm radiography Fluoroscopy 4 Angiography 6 Ultrasound 8 Computed tomography 10 Nuclear medicine (traditional) PET-CT 16 Magnetic resonance imaging 18 Interventional radi ology 20 2 12 SUBASH KC/NMC-15TH/2014 2 CHAPTER 1 Techniques Plain \201 lm radiography The electromagnetic spectrum is comprised of different types of radiation, which all travel at the same velocity in a vacuum, 3 \227 10 but which vary in their frequency, wavelength, and energy. Plain \201 lm radi- ography utilizes X-rays, wh ich are a type of ionizing radiation owing to their extremely short wavelengths and high en ergies. 8 m/s (speed of light), Using X-ray tubes, electrons produced by thermionic emission from the negatively charged ca thode are accelerated towards the positively charged anode. These fast moving electrons int eract with the atoms of the metallic anode and by doing so their kinetic energy is converte d into X-rays (1 % ) and thermal energy (99 % ). Most diagnostic radiology sets have anodes made of a tungsten \200\223rhenium alloy but in mammography either molybdenum or rhenium i s used. X-rays that travel through the tissues of the body can be absorbed or scattered. Both these processes contribute to attenuation of the primary X-ray beam. X-rays that are transmitted through the patient re \202 ect a varying degree of attenuation, which is dependent upon several factors including the atomic numbers and physical densities of the materials traver sed in addition to the initial energies of the incident primary X-ray beam. The \201 nal radiographic image is formed entirely of transmitted X-rays. Until very rece ntly, radiographic \201 lm was used to display the \201 nal image. X-rays that have pas sed through air are minimally attenuated and therefore maximally transmitted, causing \201 lm blackening. X-rays that have passed through bone are heavily attenuated with very f ew transmitted, resulting in minimal \201 lm exposure and a resultant white appearance. Most modern radiology departments now use digital radiographic acquisition in conjunction w ith picture archiving communication systems (PACS). Digital image plates replace radiograph ic \201 lm with computers playing a fundamental role in post-processing and storage. The \201 nal image is then displayed on a dedicated viewing monitor. Although plain \201 lm radiography utilizes ionizing X-ray radiation, the effective doses for the majority of examinations performed are low in comparison to computed tomography (C T). It is cheap, readily accessible, and easy to perform and for these reasons is commonly the \201 rst-line imaging modality utilized by clinicians. The main applications of plain radiography are initial investigation of the thorax, abdomen , and skeletal system, in particular trauma and joint-based disease (Fig. 1.1 ). Despite it s high spatial resolution, the major disadvantage of radiography is its poor soft tissue co ntrast resolution, which is where other modalities such as magnetic resonance imaging (MRI) and CT, to a lesser extent, are more useful. SUBASH KC/NMC-15TH/2014 PLAIN movie RADIOGRAPHY 3 (a) (b) Fig. 1.1 a) AP radiograph of the ankle joint demonstrating a multisegmental fracture of the distal tibia and \201 bula. b) Chest radiograph demonstrating generalized patchy shadowi ng throughout both lungs and a central line in a 20-year-old with cystic \201 brosis. SUBASH KC/NMC-15TH/2014 4 CHAPTER 1 Techniques Fluoroscopy Historically the \201 rst mode of medical imaging to use ionizing radiation, dating back to 1895. The patient was placed between an X-ray source and the observing radio logist looked down a tube with a \202 uoroscopic coating, unfortunately with substantial radiation to the radiologist. Thankfully monitors were introduced to display images obtaine d by intensi \201 er units. Fluoroscopy uses rapid pulses or streams of X-rays to produce a real-time image rather like a moving radiograph. The devices can be angled or moved in 3 dimensions to achieve optimal views to demonstrate pathology. Fluoroscopy has a role in both diagnostic and procedural work, including vascular intervent ion and use in operating theaters. Orthopedics use screening to align \201 xation plates and reduce fractures. Musculoskeletal (MSK) radiologists use it to perform arthrograms and injections. Gastrointestinal (GI) and urological (Uro) radiologists use screening (see \200\230Imaging \200\231). Contrast agents are central to GI and Uro radiology \202 uoroscopy: Positive agents such as barium and iodine block X-rays; pathology often appears as a \201 lling defect within the contrast. Negative agents (air and water) distend structures/lumens and allow more X-rays through. Double-contrast techniques utilize both of the above and allow surfaces to be visualized in detail (Fig. 1.2 ), e.g. bowel mucosa. Imaging Visualization of the GI tract lends itself well to \202 uoroscopy. Luminal con- t rast can be administered either orally or per rectum. Care is required in preparing the pat ient correctly; fasting or bowel laxative preparation may be required. Check local protocol s for each study. GI radiology \200 Swallow: pharynx and esophagus. \200 Meal: lower esophagus, stomach, and duodenal cap. \200 Small bowel meal: small bowel, in particular the terminal ileum. \200 Single-contrast water soluble upper or lower GI study: to identify perforation or obstruction especially useful postoperatively. Double-contrast enema: colonic pathology, excellent mucosal detail caution not in acute colitis or diverticulitis (perforation risk). Biliary imaging, including endoscopic retrograde cholangiopancreatography (ERCP). Procedures: nasogastric (NG) and nasojejunal (NJ) tube placement. Oesophageal and colonic stents. Uro radiology \200 Nephrostomy insertion. \200 Nephrostogram. \200 Ureteric stent ins ertion. \200 Cystogram, urethrogram. \200 Retrograde ureterograms (performed in theater by urologists). \200 Loopograms or conduitograms (postoperative studies performed by ret rograde administration of contrast into a neo-bladder after urinary diversions surgery to e xamine both the conduit and upper tracts). SUBASH KC/NMC-15TH/2014 FLUOROSCOPY 5 Fig. 1.2 of the radio-opaque barium, against the radiolucent air. The stomach folds can be clearly seen in the distal stomach. Image from an upper GI contrast study, showing the double-contrast effect SUBASH KC/NMC-15TH/2014 6 CHAPTER 1 Techniques Angiography Angiography is an imaging technique where a radio-opaque contrast agent is inje cted intravenously or intra-arterially and the target vessel is visualized using \202 uor oscopy. The image thus acquired is called an angi- ogram. Visceral, peripheral, and central arteries and veins can be imaged depending on the indication (Fig. 1.3 ). Indications Angiography can identify: \200 Site of vascular stenosis or occlusion. \200 Vascular anatomy or anomalies prior to intervention or surgery. \200 Active bleeding. \200 Arterial dissection. \200 Graft and transplant angiography. Procedure Access The common femoral vein or artery is most commonly used. The brachial rout e is an alternative, used when the femoral approach is either inappro- priate (e.g. demonst ration of upper limb venous anatomy prior to \201 stula formation) or unavailable. Rarely, direct puncture of a graft site may be performed. Jugular or subclavian vein punctu re may also be performed, if the superior (SVC) or inferior vena cava (IVC) needs to be visualized. Local preparation The site is cleaned and under strict asepsis the appropriate vessel is ta rgeted after administering local anesthesia. Technique The choice of proper equipment prior to beginning the procedure is vital to its s uccess. The vessel may be punctured using anatomical landmarks, but in some cases either ultrasound or \202 uoroscopic guidance is needed. Once the vessel is punctured, a guidewire is passed and its position con \201 rmed with \202 uoroscopy. An appropriate vascular catheter is passed over the g uidewire, which is then removed. Contrast is then either hand injected (if a small peripheral artery or vein is to be visualized) or pump injected (if aorta or IVC is to be visualized) and the anatomy is demonstrated. If necessary the appropriate vascular bed may then be selectively catheterized using special catheters or micro-catheters. Once the diagnostic images are acquired, these can then be transferred to an adjacent screen to be used as a road map for further intervention. Contrast agents The commonest agents are iodine-based compounds of different types. Hyperos molar and ionic agents are not commonly used today, as iso-osmolar or hypo-osmolar non-ioni c agents are preferred. Carbon dioxide is used as a negative contrast agent for angiography in patients with iodine allergy or renal failure. Gadolinium is also an alternative to iodinated agents. SUBASH KC/NMC-15TH/2014 ANGIOGRAPHY 7 Complications \200 Puncture site complications: haematoma, pseudo-aneurysm, arteriovenous (AV) \201 stula and infection. Contrast allergy and anaphylaxis. \200 Trauma to the vessel, leading to dissection, ruptu re, bleeding, or occlusion. Alternatives to conventional angiography With the development of both CT and MR, the diagno stic role of inva- sive angiography is diminishing. Contrast-enhanced CT angiography and bo th contrast enhanced and unenhanced MR (such as time of \202 ight and phase contrast MR) can be used to visualize different vascular beds for diagnostic purposes. These can then be used to guide conventional angi- ographic intervention. Useful information for the radiologist It is important to know about the patient \200\231s renal function, clotting pro \201 le, and any major underlying morbidity as often these pa tients need to lie \202 at for long periods of time. Prior imaging and background clinical history may provide useful information of the exact vascular bed to be imaged. Fig. 1.3 vascular disease who presented with an acutely ischaemic left leg. The angiogram s hows an occluded left iliac system, and heavily calci \201 ed right iliac arteries. Coronal image from an angiography study in a patient with peripheral SUBASH KC/NMC-15TH/2014 8 CHAPTER 1 Techniques Ultrasound Ultrasound imaging (Fig. 1.4) uses high-frequency sound waves (1 \200\22320MHz) and the way they travel through tissues, to image different areas of the body. Tissues of d ifferent densities re \202 ect the sound waves back to the probe with their own characteri stics. These variances are used to generate an image. \200 Ultrasoundwaves are re \202 e cted by bone and gas. It is therefore poor for imaging these bodily tissues and structures containing gas. It is an operator-dependant form of imaging that is the \201 rst line of investigation in biliary, cardiac, renal, obstetric, and many vascular diseases. It is frequently used to perform guided aspiration, biopsies, and insertion of drains (thoracic or abdomino-pelvic). The use of Doppler ultrasound allows assessment of patency and \202 ow in blood vessels. Abdominal scan This investigation involves the evaluation of the solid organs of the abdome n (liver, gallbladder, pancreas, aorta, kidneys, spleen). It is used to assess: Liver size and texture, assessment of any potential masses. \200 Biliary system: biliary duct dilatation, presence of stones, and gallbladder wall thickness. Doppler of hepatic artery/veins and portal vein for \202 ow characteristics. \200 Pancr eas. \200 Aorta: assessing diameter for presence of an aneurysm. \200 Kidneys: for size , texture, presence of calculi and size of collecting system (i.e. looking for hydronephros is). The bladder is not routinely examined in an abdominal ultrasound scan, therefore a ded icated renal examination should be requested if this is required. Spleen: size and texture. Urinary tract scan Assessment of kidneys (Fig. 1.5 ) and bladder: \200 Examination is per formed with a full bladder to assess the bladder wall thickness accurately. Pre- and post-micturition imaging can be obtained to gain information about the bladder capacity and emptying. Pelvic scan Assessment of the uterus, ovaries, and pregnancy. Scans can be performed: \200 Transabdominally (TA): patient must have a full bladder. \200 Transvaginally (TV): this gives a more detailed assessment of the gynecological organs. Testicular scan This is used to assess testicular masses such as: \200 Tumors. \200 Hyd rocoeles. \200 In \202 ammation/infection. SUBASH KC/NMC-15TH/2014 ULTRASOUND 9 Neck Ultrasound is used to assess: \200 Neck and thyroid masses. \200 Presence and char acteristics of lymph nodes. Cardiac ultrasound Measurement of chamber size. Accurate assessment of valve and wall motio n: \200 2D echocardiography provides real-time images of the anatomy and spatial relationships. Duplex Doppler includes color coding of \202 ow directions and allows direct visualization of shunts and regurgitant \202 ow. Vascular scan Assessment of: \200 Carotid artery disease. \200 Peripheral vasculature. \200 Venous imaging. Fig. 1.4 shoulder movements. The arrow points to the supraspinatus tendon and the arrow- he ad to the thickened subacromial bursa consistent with subacromial bursitis. Longitudinal scan of the shoulder rotator cuff in a patient with restricted (a) (b) Fig. 1.5 with hydronephrosis. b) Longitudinal image of the common carotid artery with cross es outlining the tunica intima. a) Longitudinal image of a kidney with a dilated collecting system consistent SUBASH KC/NMC-15TH/2014 10 CHAPTER 1 Techniques Computed tomography Computed tomography (CT) uses X-rays to produce cross-sectional images of the body (Fig. 1.6 ). Images are generated by rotation of an X-ray tube around the patie nt. A ring of detectors located around the patient then measures the transmitted radiation. The numerical data obtained is computer processed to reconstruct the \201 nal images. In spiral or helical scanners the X-ray tube rotates continuously around the patient whilst the table, on which the patient is lying, is mechanically moved through the X-ray beam. Th is allows a continuous volume of data to be obtained rather than acquiring data one slice a t a time. All modern CT scanners utilize spiral scanning and incorporate multiple rows of d etector rings (known as multislice or multidetector scanners). Multidetector spiral CT has a number of advantages over single slice scanning: \200 Faster scanning: a greater area o f the patient can be covered in a given time by the X-ray beam. Better dynamic imaging: as a consequence of faster scanning, it is possible to acquire images during different phases of passage of contrast through tissues o f interest. Thinner slices: thin slices, down to sub-millimeter thickness, can be acquired thereby improving spatial resolution. Genuine 3D imaging: this requires thin slices with equal x/y/z dimensions. This allows the volume of data to be reformatted in various planes (axial, sagi ttal, coronal, oblique) and as 3D representations of structures. CT image reconstruction Every CT slice is subdivided into a matrix of up to 1024 x 1024 vol ume elements (voxels). Each voxel has been traversed during the scan by numerous X-ray phot os and the intensity of the transmitted radiation measured by detectors. From these intensi ty readings, the density or attenuation value of the tissue at each point in the slice can be calculated. The viewed image is then reconstructed as a corresponding matrix of picture elements (pixels). Houns \201 eld unit or CT number Each pixel is assigned a numerical value, which is the av erage of all the attenuation values contained within the corresponding voxel. This number i s compared to the attenuation value of water and displayed on a scale of arbitrary units kn own as the Houns \201 eld unit (HU) or CT number (named after Sir Godfrey Houns \201 eld who developed the \201 rst CT scanner in 1972). This scale assigns water an attenuation v alue of zero HU. The range of CT numbers is usually 2000HU. Each number represents a shade of gray with + 1000 (white) and \210\222 1000 (black) at either end of the spectrum. Window level and window width The range of CT numbers recognized by the computer is 2000, b ut the human eye can only distinguish 11 different shades of gray. Hence, in order to be ab le to interpret the image, only a limited number of HU are displayed. This is achieved by s etting the window level and window width on the computer to a suitable range of HU, dependi ng on the tissue being studied. SUBASH KC/NMC-15TH/2014 COMPUTED TOMOGRAPHY 11 The term window level represents the central HU of all the numbers within the window width. The window width covers the HU of all the tissues of interest, which are displayed as various shades of gray. Tissues with HU outside this range are displayed a s either black or white. Contrast media Contrast between the tissues of the body can be improved by the use of contr ast agents. These are usually substances with high molecular weight, which increase the att enuation value of tissues they opacify. Oral contrast This is used to opacify bowel thereby making it easier to identify pathology. Iodine-based preparations are usually used and are normally given to the patient to drink 1 hour prior to the examination. 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.