Radiology Basics: Cross-sectional Imaging CT, MRI, USS An e-learning resource for medical students and junior doctors Melisa Sia Vikas Shah An e-learning resource for medical students and junior doctors Radiology Basics: Cross-Sec9onal Imaging Foreword Disclaimer Radiology is often a neglected component of the undergraduate This book is intended for educational purposes only. All efforts have curriculum. Plain films are given much more importance than cross- been made to minimise mistakes - if you do find any, please contact us sectional imaging, and rightly so. However, it is important for junior and let us know! Please do not use this book to interpret images doctors to be able to identify certain important pathology on cross- independently - seek the advice of your friendly consultant radiologist! sectional imaging, particularly in the ED where the interpretation of a radiologist may not be immediately available. The aim of this book is to provide an easily accessible resource on Contact Us cross-sectional imaging, aimed at the appropriate level for medical Any feedback and comments are much welcomed and appreciated! students on clinical attachments and junior doctors. An interactive e- Please send any correspondence to: [email protected] book format has been chosen as this is a very visual subject, and also for ease of distribution. This book includes the underlying physics, You can find updates and news about new books on our website: important presentations and common pathologies, with a focus on http://www.RadiologyBasics.net acute conditions. Important cross-sectional anatomy is also presented, this may be useful for more junior students and for revision purposes for Find us on... senior students. Twitter @BasicRadiology, @Melisa_Sia, @DrVikasShah Facebook http://www.facebook.com/BasicRadiology Dr Melisa Sia Foundation Year 1 doctor; MBChB (Hons) University of Leicester Dr Vikas Shah Consultant Radiologist, University Hospitals Leicester < < < SWIPE to turn the page 1 How to Use This Book Pinch with two fingers to return to the main Table of Contents. General Controls Swipe left/right to turn pages. Swipe to scroll Tap the centre of the page to open the between menu bar, where you can adjust chapters brightness, search the text, or add a bookmark. Swipe to scroll between pages in selected chapter Zoom by pinching outwards with two fingers. Tap to select page Scroll through an image stack using the arrows beneath it. Layout This book is divided into five chapters. Look through an image gallery by Chapter 1 - general overview of imaging modalities, with particular focus swiping over the image, or by on cross-sectional imaging. tapping on the thumbnails. Chapter 2, 3, 4 - each chapter covers one of the main body areas, starting with annotated normal studies to show anatomy, followed by common pathologies. and then a quiz section. Chapter 5 - requesting imaging and relevant guidelines. Tap this button to play animations. There is a short quiz section at the end of each chapter. Select an answer and tap . Web links will open a new browser window for further reading You can tap the button for a more detailed explanation of the correct (Internet connection required). answer. 2 The contents of this book have been mapped to the RCR undergraduate curriculum and foundation programme competencies. Royal College of Radiologists’ Undergraduate Learning Outcomes System Clinical Presentation Example Conditions (in this book) Chest pain Pneumonia Pneumothorax Thoracic trauma Pleural effusion Pulmonary embolism Cardiorespiratory Breathlessness Lung cancer Aortic dissection Cough Metastases to lung Rupture of AAA Haemoptysis Chronic lung disease Abdominal pain Metastases to liver Inflammatory bowel disease Abdominal masses Liver abscess Appendicitis Abdominal trauma Cholecystitis Diverticulitis Swallowing disorders Gastrointestinal Gallstones Perforation Bowel obstruction Pancreatitis Air in bladder Bowel perforation Pancreatic cancer Bowel ischaemia Change in bowel habit Bowel obstruction Traumatic lacerations Jaundice Urinary colic Renal cell carcinoma Haematuria Simple renal cysts Renal Acute kidney injury Renal stones Urinary obstruction Hydronephrosis Acute presentation of testicular disease Head injury Haemorrhage Stroke Infarct Severe headache Mass lesions Neurology Seizures Degenerative changes Altered consciousness Venous sinus thrombosis Spinal cord compression Skull fracture Bone pain Joint pain Vertebral fracture Bone and soft tissue trauma Metastases to spine Musculoskeletal Bone and soft tissue infection Spinal injury Neck and back pain Suspected or abnormal pregnancy Normal pregnancy Abnormal vaginal bleeding; pelvic pain Uterine fibroids O&G Pelvic mass Ultrasound in normal pregnancy Principles of oncological disease staging by imaging Multisystem disease Anaemia Lymphoma Pyrexia of unknown origin 3 Royal College of Radiologists’ Foundation Programme Competencies • Requests/arranges appropriate basic imaging (radiology), laboratory tests and other investigations in a timely fashion • Provides concise, accurate information when requesting investigation • Discusses the indications for and expectations of the test to radiology/laboratory staff • Interprets the results correctly within the context of the particular patient/presentation • Recognises that requesting investigations and seeking out then interpreting and acting upon their results is a crucial element of modern medical practice • Requests investigations appropriate for patients’ needs and the clinical context • Discusses requests appropriately and provides relevant information on the request form • Avoids unnecessary investigations and recognises that investigations are only needed if the result will impact on patient management • Interprets basic radiographs in the context of the patients’ history and presentation • Reviews reports when circumstances change 4 Chapter 1 Introduc9on and Overview Overview of Imaging Modalities Modality Terminology Contrast medium Radiation Prep Contraindications/Problems X-ray Opacity vs Lucency Iodine (e.g. IV pyelogram) Yes - Pregnancy (relative) CT Attenuation/Density Iodine Yes Hydration (low eGFR) Renal impairment, Pregnancy (relative) MRI Signal intensity Gadolinium No Remove piercings Metals, Electronics, Claustrophobia Ultrasound Echogenicity Air (‘microbubbles’) No Full bladder (gynae scans) Body habitus, Operator skill Nuclear Uptake Radioactive labelled ‘tracer’ Yes - Pregnancy, Breastfeeding Fluoroscopy Filling defect Barium/Air/Gastrografin Yes NBM/Bowel prep Poor mobility X-rays, or plain films, are used as a first-line imaging investigation in most situations due to their low radiation dose and easy availability. Nuclear imaging measures the uptake of various labelled radioactive isotopes. Bone scans use an IV tracer that concentrates in areas of high bone activity, including inflammation and infection. They are mainly used to show bone metastases (multiple myeloma is an exception which may not show). Arthritis will also show as hot spots. The renal collecting system (kidneys and bladder) show high uptake as they excrete tracer. Anterior and posterior images are taken. Other applications include V/Q scans and PET scans. (PET-CT = PET overlaid over CT) Fluoroscopy is the use of X-rays to obtain live moving images. Common uses include barium studies, angiography, and interventional procedures. Barium studies: Swallow = Oesophagus; Meal = Stomach; Follow-through = Small bowel; Enema (double-contrast if air is also used) = Large bowel Interventional radiology performs procedures under imaging guidance. Examples include the insertion of PICC and Hickman lines. Foams and coils are used to embolise blood vessels that are bleeding or supplying a tumour. Biopsies are done under CT and ultrasound guidance. Percutaneous coronary intervention (PCI) which involves angiography and stenting is an intervention that is now being carried out by cardiologists. CT, MRI and Ultrasound - the cross-sectional imaging modalities - will be discussed further in the following pages. 5 CT Phases of a scan refer to when the images are taken, relative to time of contrast administration. Physics non or pre-contrast > arterial > venous > delayed CT (computed tomography) uses X-rays to obtain images. The arterial phase comes before the venous phase, because even A heated cathode releases high-energy electrons, which in turn though contrast is given into a vein, within approximately 30 seconds, release their energy as X-ray radiation. the contrast has passed through the heart and into the arterial system. X-rays pass through tissues and hit a detector on the other side. • The chest is usually imaged in the arterial phase. The more dense a tissue, the more X-rays it absorbs. • The abdomen is usually imaged in the (portal) venous phase. • Bone: X-rays absorbed = Few X-rays reaching detector: White • Liver lesions are usually imaged with a multiple phase scan. • Air: X-rays not absorbed = Lots of X-rays reaching detector: Black Compared to plain film, CT is able to distinguish more subtle density In a CT chest/abdo/pelvis, the lung bases/liver may be imaged twice: differences and there is no overlap of structures. (overlap between chest - arterial phase, and abdomen - venous phase) Current CT machines use ‘Spiral CT’. An array consisting of a single Artefacts can complicate interpretation. Examples: radiation source with multiple detectors rotates around the patient, • metal (usually seen as radiating bright streaks): sternotomy wires, obtaining a block of