Cross-Sectional Anatomy
Planes and conventions
Axial (transverse), coronal, sagittal, oblique and curved reformats. Axial CT and MRI images are conventionally displayed as if viewed from the patient's feet, so the patient's left appears on the viewer's right. Coronal and sagittal images are viewed as if facing the patient. Mastering these conventions prevents laterality errors.
Density and signal
CT numbers in Hounsfield units: air about −1000, fat about −100 to −50, water 0, soft tissue 20–60, acute blood 50–80, bone 300–2000, metal far higher. Window width and level select which tissues are displayed with contrast. On MRI, T1 shows fat bright and fluid dark; T2 shows fluid bright; fat suppression, STIR and post-gadolinium sequences change interpretation entirely.
Regional anatomy
Know the mediastinal compartments and great vessel relations, the lobes and segments of the lungs, the liver segments and biliary tree, the retroperitoneal kidneys, aorta and inferior vena cava, the portal triad, and the pelvic organs and spaces. Use vertebral landmarks: carina about T4–T5, renal hila about L1–L2, aortic bifurcation about L4, iliac crest about L4.
Traps
Left-right reversal on axial images; confusing the Hounsfield units of fat and air; calling a structure invisible when it is simply outside the displayed window; misidentifying vessels on unenhanced scans.
Rule of thumb
Find the midline first - spine, aorta, falx - then work laterally, and confirm the scan phase before deciding that a structure enhances abnormally.
Physiology and Pathology Correlation
Why it matters
Radiographers must link the request, the patient's presentation and the expected image to choose technique, timing and contrast. Contrast phases are physiology-driven: arterial around 25–35 seconds, portal venous around 60–80 seconds, and delayed phases over minutes for liver and urinary tract assessment.
Recognisable patterns
Air-space opacity with air bronchograms suggests pneumonia or pulmonary oedema. A meniscus with a blunted costophrenic angle suggests pleural effusion. Absent lung markings suggest pneumothorax. Volume loss with fissure displacement suggests atelectasis. Dilated bowel with air-fluid levels suggests obstruction. A lytic lesion with periosteal reaction suggests tumour or infection. Joint space narrowing with osteophytes suggests osteoarthritis.
Systemic considerations
Cardiac output and renal function affect contrast timing and safety. Dehydration and metformin increase nephropathy risk. Thyroid disease and previous reactions alter preparation. Pregnancy and breastfeeding require individual risk assessment. Respiratory disease affects tolerance of positioning. Diabetes affects wound healing and infection risk.
Traps
Choosing the wrong phase for the question asked, for example a non-contrast study for a vascular question. Attributing an artefact or normal variant to pathology. Assuming a normal radiograph excludes disease.
Worked example
For suspected pulmonary embolism, CT pulmonary angiography needs bolus tracking or a test bolus timed to peak pulmonary arterial enhancement, not a routine portal venous phase. If renal function is impaired, discuss with the radiologist before giving contrast.
Patient Care
Foundations
Positive identification using at least two identifiers precedes every exposure. Obtain consent for the specific procedure, explain in plain language, and check allergies, pregnancy status, implants, mobility and communication needs. Dignity, privacy, chaperones and cultural safety are non-negotiable. Document what was done and any refusal.
Practical care
Safe transfer and moving and handling: assess the load, use aids, keep the spine neutral, never lift alone. Monitor vital signs where relevant, manage oxygen, intravenous lines, catheters and drains without traction, and secure the patient before table movement or tilt. Fasting and hydration instructions vary by examination. Children need play preparation, warm rooms and short, clear instructions; older people need falls precautions and cognitive assessment; bariatric patients need weight-rated equipment and extra staff.
Communication and safety
Use teach-back to confirm understanding. Escalate deterioration immediately: sudden confusion, chest pain, breathlessness or a fall. Report incidents and near misses honestly.
Traps
Accepting a verbal name match without a second identifier; assuming an unconscious patient cannot be imaged (emergency treatment may proceed in their best interests); leaving a patient unattended on a table; using a hoist without training.
Rule of thumb
Before touching the patient: identify, consent, explain, check allergy and pregnancy, and confirm the request matches the patient. Afterwards: confirm the patient is safe to leave and that images are diagnostically acceptable.
Contrast Media and Emergency Management
Agents
Iodinated contrast (ionic or non-ionic, low or high osmolar) is used for CT, angiography and urography; barium sulphate for gastrointestinal studies; gadolinium chelates for MRI. Assess renal function, previous reactions, asthma, cardiac disease, thyroid dysfunction, pregnancy and metformin use. Extravasation requires stopping the injection, elevating the limb, applying a cold compress and arranging documented follow-up.
Reactions
Mild reactions - nausea, urticaria, flushing - need observation and symptomatic treatment. Moderate reactions - persistent urticaria, mild bronchospasm, vomiting - need antihistamine and close observation. Severe anaphylactoid reactions - stridor, hypotension, bronchospasm, laryngeal oedema - require calling for help, ABCDE assessment, high-flow oxygen, supine positioning with legs raised, intramuscular adrenaline 0.5 mg (0.5 mL of 1:1000) into the anterolateral thigh for an adult, repeated after five minutes if needed, plus intravenous fluids and airway support.
Other emergencies
Vasovagal syncope (bradycardia, hypotension; lay flat and elevate the legs), seizures, cardiac arrest (start CPR and attach a defibrillator), aspiration and hypoglycaemia. Know where the emergency trolley, oxygen and suction are, and practise drills.
Traps
Giving intravenous adrenaline 1:1000; delaying adrenaline while giving antihistamines; failing to document the reaction and advise the patient; repeating contrast after a previous reaction without radiologist review.
Rule of thumb
Reaction severity sets the response: skin only - observe; airway or circulation - adrenaline and call for help. Document time, drug, dose, route and response.
Infection Prevention and Control, and Occupational Safety
Standard precautions
Assume every patient may be infectious. Perform hand hygiene at the WHO five moments, before and after patient contact and after touching equipment or body fluids. Use personal protective equipment appropriate to the task: gloves for body fluids, apron or gown, and mask with eye protection when splash is likely. Use aseptic non-touch technique for invasive procedures. Clean shared equipment between patients; classify devices by the Spaulding scheme as critical (sterilise), semi-critical (high-level disinfection) or non-critical (clean and low-level disinfection).
Transmission-based precautions
Contact precautions for MRSA, Clostridioides difficile and scabies (gown, gloves, dedicated equipment). Droplet precautions for influenza and meningococcus (surgical mask, distance). Airborne precautions for tuberculosis, measles and varicella (N95 or FFP3 respirator, negative pressure room). Never recap sharps; dispose immediately and follow the needlestick pathway after any injury.
Occupational safety
Manual handling, ergonomics and repetitive strain; slips and trips; electrical safety, including checking leads and keeping liquids away from equipment; fire safety, including raising the alarm and evacuating; lone working; stress and fatigue; latex allergy; and radiation as an occupational hazard. Report incidents and near misses promptly.
Traps
Wearing gloves instead of performing hand hygiene; reusing personal protective equipment between patients; assuming airborne precautions need only a surgical mask; forgetting to clean cassettes and markers.
Rule of thumb
Gloves are not a substitute for hand hygiene, and hand hygiene is still required after glove removal. Clean hands, clean equipment, correct personal protective equipment - in that order.
Professional Practice, Ethics, Communication and Health Law
Professional framework
Practise within your scope and competence, maintain registration through continuing education, follow professional standards and local protocols, and remain accountable for your own actions, including those of students you supervise. Escalate beyond your competence rather than improvising.
Ethics and law
The four principles - autonomy, beneficence, non-maleficence and justice - guide decisions. Valid consent requires capacity, adequate information and voluntariness; it may be implied, as when a patient holds out an arm, or written, and it can be withdrawn at any time. For children, assess competence; a parent or guardian consents where the child lacks it, and emergency treatment proceeds in the patient's best interests. Negligence requires a duty of care, a breach of that duty, causation and damage. Confidentiality is a legal duty with defined exceptions such as safeguarding, public interest and court order. Records must be accurate, contemporaneous, attributable and secure; patients may access them.
Communication
Use plain language, arrange interpreters when needed and check understanding. Break bad news sensitively and signpost support. Be candid about errors, apologise and report. On social media, never post identifiable patient information and maintain professional boundaries.
Traps
Assuming a signed form equals valid consent; disclosing information to relatives without consent; blurring boundaries online; treating a complaint as a personal attack rather than a system issue.
Rule of thumb
If you would not be comfortable defending the action in a professional, legal or public forum, stop and seek advice. When in doubt: consult, document and escalate.