Makindo Medical Notes

💡 Medical Imaging in the MLA Students are expected to know the indications, basic principles, and limitations of common imaging tests. You are not expected to report scans in detail, but you should recognise classic patterns and understand when to order the right test.

📸 Plain Radiography (X-ray)

• How it works: Uses ionising radiation; dense structures (bone, metal) appear white, air appears black.
• Indications: Fractures, chest pathology (pneumonia, effusion, pneumothorax), bowel obstruction, foreign bodies.
• Advantages: Quick, cheap, widely available, low radiation dose.
• Limitations: Poor soft tissue detail; early fractures or subtle pathology may be missed.

🖥️ Computed Tomography (CT)

• How it works: Multiple X-ray slices processed by computer → cross-sectional imaging.
• Indications: Trauma (CT head, C-spine, chest/abdomen/pelvis), stroke (non-contrast CT), pulmonary embolism (CTPA), staging of cancers.
• Advantages: Fast, good bone and organ detail, 3D reconstructions possible.
• Limitations: Higher radiation dose, contrast risks (allergy, nephropathy), less sensitive than MRI for soft tissue/cord.

🧲 Magnetic Resonance Imaging (MRI)

• How it works: Uses magnetic fields and radiofrequency pulses to image protons; excellent soft tissue contrast.
• Indications: Brain/spinal cord lesions, multiple sclerosis, ligament/cartilage injuries, tumour characterisation, ischaemic stroke (DWI).
• Advantages: No ionising radiation; superb soft tissue detail; multiple sequences (T1, T2, FLAIR, DWI).
• Limitations: Longer, claustrophobia, contraindications (pacemakers, ferromagnetic implants), expensive, less available acutely.

🩺 Ultrasound (USS)

• How it works: High-frequency sound waves reflected by tissues.
• Indications: Gallstones, biliary tree, AAA screening, obstetrics, gynae, DVT, guided procedures (biopsy, drainage, line insertion).
• Advantages: No radiation, real-time, portable, safe in pregnancy.
• Limitations: Operator dependent; poor penetration in obese patients or with bowel gas; limited bone/lung detail.

⚡ Nuclear Medicine (Scintigraphy)

• How it works: Injection of radiotracer (e.g., Tc-99m) → gamma camera detects uptake.
• Indications: Bone scan (metastases, infection), V/Q scan (PE), thyroid scan, renal isotope studies (MAG3, DMSA).
• Advantages: Functional information, whole-body survey possible.
• Limitations: Limited anatomical detail; radiation exposure; not as widely available.

🌀 Positron Emission Tomography (PET-CT)

• How it works: Uses positron-emitting tracer (e.g., FDG-glucose) combined with CT for anatomy + function.
• Indications: Cancer staging, recurrence detection, some neuro/cardiac applications.
• Advantages: Functional + structural data, whole-body assessment.
• Limitations: Radiation exposure, costly, limited availability.

💉 Fluoroscopy

• How it works: Real-time X-ray imaging (with contrast agents).
• Indications: Swallow studies, angiography, interventional procedures (stents, embolisation).
• Advantages: Dynamic studies, therapeutic as well as diagnostic.
• Limitations: Higher radiation exposure, requires contrast.

🔎 Specialised Imaging to be aware of (MLA)

• CT Head (non-contrast): First-line in suspected stroke, head trauma, SAH (within 12h).
• CT Pulmonary Angiography (CTPA): Test of choice for PE (unless contraindicated — then V/Q scan).
• CT Abdomen/Pelvis with contrast: Acute abdomen, cancer staging.
• MRI Spine: For cord compression, cauda equina, MS lesions.
• USS Abdomen: First-line for gallstones, AAA, renal obstruction.
• Echocardiography (TTE/TOE): Valvular disease, endocarditis, pericardial effusion.

⚠️ Safety & Contraindications

• Radiation risk: CT > X-ray > USS/MRI (no ionising radiation).
• Contrast nephropathy: Risk with iodinated contrast in CT; check renal function.
• MRI contraindications: Pacemakers, cochlear implants, metallic foreign bodies.
• USS: Safe in pregnancy, but limited by operator skill and patient habitus.

📚 Key Teaching Pearls

• Always ask: What am I trying to confirm/exclude? → Choose imaging accordingly.
• Don’t over-order: Radiation accumulates; justify CT requests.
• Learn to recognise classic MLA images: CXR pneumonia, CT head bleed, XR fracture, USS gallstones, bone metastases on isotope scan.
• Know first-line investigations: CXR (dyspnoea), USS (RUQ pain), CT head (stroke/trauma), XR (fracture).