GC015 Imaging Of The Head And Neck
Diagnostic imaging of the head and neck encompasses radiographic, CT, MRI, and ultrasound techniques used to evaluate structures such as the brain, sinuses, orbits, salivary glands, thyroid, vasculature, and aerodigestive tract for pathology.
Imaging of the Head and Neck
This lecture, delivered by Dr. Jane J. Kim (Department of Radiology), is built around a single clinical scenario that every doctor will face: "Doc, I feel a lump." It teaches you how to think through a neck mass systematically — asking the right clinical questions, choosing the right imaging modality, and recognizing imaging findings — organized by three broad categories: inflammatory/infectious, neoplastic, and congenital. It also covers critical special considerations (contrast allergy, renal disease, pregnancy, MRI contraindications) that come up repeatedly in MCQs.
Why this matters for exams: Radiology questions in HKUMed summatives love testing which modality to order and why, CT vs MRI indications, contrast contraindications, and red flags for malignancy (especially the HPV+ oropharyngeal SCC pitfall). Past papers have directly tested choice of first-line imaging (2020 MCQ Q1, 2022 SAQ Q1, 2024 SAQ Q3), thyroid nodule workup (2019 Minicase, 2022 Minicase, 2024 MCQ Q59, 2025 MCQ Q21-25), and contrast-related complications (2022 SAQ).
Learning Objectives (inferred from slide structure):
- Develop a systematic approach to a patient with a neck mass (age, acuity, signs of infection, location).
- Select the appropriate imaging modality for inflammatory, neoplastic, and congenital neck masses.
- Recognize key CT and MRI findings of common neck pathologies.
- Understand special considerations: contrast allergy, renal disease, pregnancy, MRI contraindications.
- Avoid the critical pitfall of dismissing a cystic neck mass in an adult as benign.
"Adult or pediatric? Acute or subacute or chronic? Signs of infection? Location?" [1]
These four questions are the foundation. They determine the differential diagnosis and the imaging approach.
| Clinical Feature | Why It Matters |
|---|---|
| Age | Children → congenital/inflammatory far more common. Adults → neoplasm must be excluded first. |
| Acuity | Acute (days) → infection/inflammation. Chronic (weeks–months) → neoplasm or congenital. |
| Signs of infection | Fever, pain, erythema, recent dental/pharyngeal symptoms → inflammatory mass. Dictates CT with contrast as first-line. |
| Location | Determines which spaces are involved (submandibular, parotid, parapharyngeal, carotid, posterior triangle) and narrows differential. |
The Three Categories of Neck Mass
The lecture organizes all neck masses into three groups: Inflammatory, Neoplastic, and Congenital. [1] This is the framework examiners use. Every question stem about a neck mass can be mapped to one of these.
Part 2: Inflammatory / Infectious Masses
The lecture presents three classic infectious scenarios:
CT neck with IV contrast is test of choice for suspected head/neck infection — fast, accessible 24/7, good resolution, excellent for evaluating infection source/bone (dental disease). [1]
Why CT with contrast and not without?
- IV contrast makes abscesses visible: the abscess wall enhances (picks up contrast) while the pus inside does not, creating the classic rim-enhancing fluid collection appearance. Without contrast, you cannot distinguish an abscess from surrounding oedematous tissue reliably.
- Contrast also helps delineate vascular structures and their relationship to the infection (critical for surgical planning).
When to use CT WITHOUT contrast:
Renal disease (GFR < 30 mL/min/1.73m²) or documented contrast allergy with no time to premedicate (need at least 5 hours). [1]
This is a direct exam point. If a question gives you a patient with eGFR of 25 who needs urgent neck imaging, the answer is CT without contrast (or consider MRI if time permits).
| CT Finding | What It Means | Clinical Significance |
|---|---|---|
| Fat stranding | Hazy increased density in normally dark fat planes | "Important imaging sign of infection/inflammation" [1] — indicates oedema spreading through fascial planes |
| Rim-enhancing fluid collection | Peripheral enhancement with central low density | = Abscess [1] — this is the imaging definition of an abscess; needs drainage |
| Reactive lymphadenopathy | Enlarged, enhancing lymph nodes | Nodes are reacting to nearby infection; distinguish from malignant adenopathy |
High Yield: Check the Teeth!
"If there is infection/inflammation in the neck, check the teeth!" [1] Dental infection is the most common cause of deep neck space infection in adults. The 2024 SAQ Q3 directly tested this: "What is the MOST COMMON infective origin?" — Answer: Dental infection (odontogenic). Always look at the teeth on CT.
CT has radiation — follow principle of ALARA. [1]
ALARA = As Low As Reasonably Achievable. In children, the thyroid is particularly radiosensitive, and lifetime cancer risk from radiation is higher because of more remaining years of life. However, if a deep neck infection is suspected and drainage may be needed, CT with IV contrast is still indicated — the benefit outweighs the risk.
Case 1: Submandibular abscess from dental infection
- 42 yo M, toothache 2 days → neck swelling, fever, pain
- CT shows rim-enhancing fluid collection in submandibular space
- Source: dental caries/periapical abscess visible on CT
Case 2: Cervical adenitis and retropharyngeal edema from Streptococcal pharyngitis
- 10 yo M, fever, sore throat, neck swelling 2 days
- CT shows fat stranding, reactive lymphadenopathy, retropharyngeal edema
- No abscess [1] — important distinction; edema alone may not need drainage
Case 3: Acute submandibular sialadenitis
- 21 yo F, right neck pain worse with eating (classic for salivary gland obstruction — eating stimulates saliva production, which builds up behind the stone causing pain)
- CT shows inflamed submandibular gland, possible calcified sialolith (bright on CT because calcium is hyperdense)
Bright on CT ("hyperattenuating"/"hyperdense"): Bone/calcium, Metal, Contrast [1] Dark on CT ("hypoattenuating"/"hypodense"): Air, Fat [1] Intermediate on CT: Soft tissue/muscle, Fluid [1]
Why does this matter? Understanding CT density is fundamental to reading any CT. The principle is simple: denser materials attenuate more X-rays and appear brighter. This is quantified using Hounsfield Units (HU):
| Material | Approximate HU | Appearance |
|---|---|---|
| Air | -1000 | Very dark |
| Fat | -50 to -100 | Dark |
| Water | 0 | Dark grey |
| Soft tissue/muscle | +30 to +60 | Grey |
| Acute blood | +50 to +70 | Light grey/white |
| Bone | +400 to +1000 | Bright white |
| Metal | +2000+ | Extremely bright |
| IV contrast (enhanced vessels) | +100 to +300 | Bright white |
Clinical application examples:
- A lipoma is confirmed by measuring its HU — it will be in the fat range (-50 to -100), matching subcutaneous fat
- A sialolith appears bright because it is calcified
- An abscess cavity appears dark (fluid density) surrounded by a bright rim (enhancing wall)
Part 4: Neoplastic Masses
A new neck mass in adult without signs of infection should be considered malignant until proven otherwise (malignant UPO = Until Proven Otherwise). [1]
This is arguably the single most important teaching point of the lecture. An adult presenting with a painless, firm, fixed neck mass of weeks-to-months duration — especially with risk factors like tobacco and alcohol — has cancer until you prove otherwise.
CT or MRI neck with contrast for suspected neoplasm. [1]
The choice between CT and MRI depends on location:
| Location | Preferred Modality | Why |
|---|---|---|
| Suprahyoid neck (nasopharynx, oropharynx, oral cavity, parotid) | MRI | Superior soft tissue contrast, better for detecting perineural spread and intracranial invasion |
| Infrahyoid neck (larynx, hypopharynx) | CT | Faster, less motion artifact from swallowing/breathing, good for cartilage invasion |
MRI is study of choice for: NPC staging, intracranial/perineural invasion, parotid tumours, oral cavity tumours (tongue), generally suprahyoid neck. [1] CT is good for: generally infrahyoid neck (larynx, hypopharynx). [1]
Case 4: Base of tongue cancer with nodal metastases
- 54 yo M, left neck mass 4 months, firm and fixed, tobacco + alcohol abuse
- CT: primary tumour at base of tongue with enlarged cervical nodes
- "In cases of malignant appearing cervical adenopathy, report should comment on primary" [1] — the radiologist must look for the primary tumour site
- "Imaging important for staging information (TNM)" [1]
Case 5: HPV-associated oropharyngeal cancer — THE CRITICAL PITFALL
A new cystic neck mass in adult should NOT be dismissed as branchial cleft cyst (BCC) or developmental lesion. Must exclude cystic nodal metastasis from HPV+ oropharyngeal SCC! [1]
This is highlighted repeatedly in the lecture for good reason. The scenario:
- 37 yo M, new left-sided cystic neck mass
- Outside hospital says "branchial cleft cyst"
- WRONG. In an adult, this is HPV+ oropharyngeal SCC with cystic nodal metastasis until proven otherwise.
Critical Exam Pitfall: Cystic Neck Mass in Adults
"Pitfall: do not assume a new cystic neck mass in adult is branchial cleft cyst — must rule out HPV+ SCC or thyroid cancer." [1] True branchial cleft cysts present in childhood. A new cystic mass in an adult is metastatic SCC (often HPV-related) or thyroid cancer with cystic nodes until proven otherwise. This is a classic exam trap.
Younger, mostly male, often nonsmokers. Better prognosis than alcohol/tobacco-associated OPCA. Separate AJCC cancer staging system (new). Primary cancer in palatine or lingual tonsil. May be very small/occult. Cervical nodes often cystic. Test by p16 (kinase inhibitor). p16+ is surrogate marker for HPV+ OPCA. [1]
| Feature | HPV+ OPCA | Traditional Tobacco/Alcohol OPCA |
|---|---|---|
| Demographics | Younger, male, non-smokers | Older, smokers + drinkers |
| Primary site | Palatine tonsil, lingual tonsil (base of tongue) | Variable H&N subsites |
| Primary tumour size | May be very small or occult | Usually visible |
| Nodal metastases | Often cystic — mimics branchial cleft cyst! | Usually solid |
| Prognosis | Better | Worse |
| Biomarker | p16+ (surrogate for HPV) | p16- |
| Staging | Separate AJCC system | Standard AJCC |
Why are HPV+ nodes cystic? The tumour cells undergo cystic degeneration within the lymph node, producing a fluid-filled appearance that can be mistaken for a benign cyst on imaging.
25 yo Chinese woman with left neck mass 3 months → MRI is preferred for NPC staging. [1]
NPC is especially relevant for HKUMed because of its high prevalence in Southern Chinese populations. The 2023 MCQ Q64 directly tested NPC management.
Why MRI over CT for NPC?
- NPC arises in the nasopharynx, which is a deep suprahyoid structure surrounded by complex anatomy (skull base, cavernous sinus, cranial nerves)
- MRI provides superior soft tissue contrast to delineate tumour extent
- MRI good for intracranial and perineural disease [1]
- Critical for T-staging: detecting skull base invasion, intracranial extension (T4)
Radiation concern in young patients:
Radiation dose of neck CT: 3 mSv (Annual background radiation dose: 3 mSv). Thyroid gland is most radiosensitive organ in neck. [1]
This is why MRI is preferred over CT when possible in young patients, especially for NPC staging. The thyroid, being in the field of a neck CT, receives significant radiation.
| Body Part CT | Approximate Radiation Dose |
|---|---|
| Neck CT | 3 mSv |
| Chest CT | 7 mSv |
| Abdomen/Pelvis CT | 14 mSv |
| Annual background radiation | 3 mSv |
Case: Adenoid cystic carcinoma of parotid with CN-VII involvement
- 57 yo F, right-sided pain and facial paralysis
- MRI shows tumour along facial nerve
- "MRI to check for perineural tumour spread" [1]
Adenoid cystic carcinoma is notorious for perineural spread — tumour cells track along nerve sheaths, sometimes far from the primary tumour. This is invisible on CT but detectable on MRI (enhancement and thickening of the nerve on post-contrast fat-saturated T1 sequences).
MRI superior to CT for intracranial or perineural invasion. [1]
The lecture shows two examples [1]:
- Carotid space schwannoma — arises from nerve sheath, well-defined, enhancing
- Carotid body paraganglioma — characteristic "flow voids" on MRI (tiny dark dots within the tumour representing fast-flowing blood vessels; paragangliomas are highly vascular)
Why flow voids? On MRI, rapidly moving blood produces no signal (appears dark). Paragangliomas have such rich vascularity that these flow voids create a characteristic "salt and pepper" pattern on T1-weighted images.
Case: 58 yo M, painless, slow-growing neck lump for several years
- CT: "Typical fat attenuation on CT confirms diagnosis" [1]
- The mass measures the same HU as subcutaneous fat (-50 to -100 HU)
- On MRI: "Fat is bright on T1 (also: blood, melanin, protein, mineralization, gadolinium)" [1]
- "Confirm it is fat with fat suppression" [1] — when you apply a fat-saturation pulse sequence, the bright signal from fat disappears. If the lesion goes dark on fat-sat, it's confirmed as fat.
T1 Bright Lesions Mnemonic
Things that are bright on T1-weighted MRI: Fat, blood (subacute), melanin, protein (concentrated), mineralization (paramagnetic), gadolinium contrast. If you see a T1-bright lesion, use fat suppression to determine if it's fat (signal drops) or something else (signal persists). [1]
Part 5: Congenital Masses
Start with ultrasound if suspected congenital mass. [1]
Why ultrasound first?
- No radiation (critical in children)
- Determines solid vs cystic nature
- Assesses vascularity with Doppler
- Cheap, readily available, no sedation needed
- If US is unclear or the lesion is deep/extensive → MRI
MRI can be complementary to US — visualize full extent of lesion (deep, multifocal). May require sedation. [1] CT/MRI offers better anatomic localization and may be helpful as next step if US is unclear. [1]
Case 6: Second branchial cleft cyst
- 6 yo boy, painless slowly enlarging lump, recent increase after viral URI
- US demonstrates cystic (vs solid) nature of lesion
- US with Doppler shows no internal vascularity (confirming cystic nature)
- This is a TRUE branchial cleft cyst — in a child, this diagnosis is appropriate (unlike in an adult!)
Why does it enlarge after viral URI? Branchial cleft cysts are lined by lymphoid tissue. During an upper respiratory infection, this lymphoid tissue becomes reactive and inflamed, causing the cyst to swell.
Case 7: Venous malformation
- 5 yo boy, soft compressible lump, bluish hue to skin
- US and MRI both helpful for suspected pediatric vascular anomalies [1]
- MRI to visualize full extent (deeper or extensive lesions) [1]
- MRI: T2-bright (fluid-filled spaces), may show phleboliths (calcified thrombi within the malformation)
Why is it compressible and bluish? Venous malformations are low-flow vascular anomalies made up of dilated venous channels. They compress because the blood can be squeezed out (like squeezing a sponge). The blue colour is venous blood visible through thin overlying skin.
Part 6: Special Considerations
Allergy to gadolinium-based contrast for MRI is extremely rare. [1] May premedicate for CT iodinated contrast (12 hours before CT). If more rapid scanning is required (start 5 hours before CT). [1]
What does premedication involve? Typically corticosteroids (e.g., prednisone/hydrocortisone) ± antihistamines given before the scan to reduce the risk of allergic reaction. The 12-hour protocol is standard; the 5-hour is for urgent situations.
Key exam point: If a patient has a contrast allergy AND needs urgent imaging (e.g., suspected deep neck abscess), you have options:
- Use CT without contrast (suboptimal but still useful)
- Use MRI with gadolinium (gadolinium allergy is extremely rare, different mechanism from iodinated contrast)
- Premedicate if 5+ hours are available
Renal Disease and Contrast
| eGFR | Guideline |
|---|---|
| ≥ 30 mL/min/1.73m² | Low risk. Little evidence that IV iodinated contrast is independent risk factor for AKI. [1] |
| < 30 mL/min/1.73m² | Higher risk. Do not give contrast. Unless: patient on dialysis/anuric or contrast is critical and benefits outweigh risks. Document in chart. IV fluid hydration. [1] |
Why the 30 cutoff? Modern evidence has largely debunked "contrast-induced nephropathy" (CIN) in patients with normal renal function. The real risk is in patients with already severely impaired kidneys (eGFR < 30), where the osmotic load and direct tubular toxicity of iodinated contrast can tip them into AKI.
Exception for dialysis patients: Patients already on dialysis are anuric — their kidneys are already non-functional, so contrast cannot cause further damage. The contrast will be removed during their next dialysis session.
Do not use if GFR < 30 [1] (risk of nephrogenic systemic fibrosis, NSF — a devastating fibrotic condition) At HKU: May use if necessary when GFR < 30 [1] (with newer macrocyclic agents that have very low NSF risk)
eGFR Cutoff for Contrast: The Magic Number is 30
For both CT iodinated contrast AND MRI gadolinium contrast, the critical threshold is eGFR < 30 mL/min/1.73m². Below this, contrast is contraindicated unless benefits outweigh risks. This has been tested directly in past papers (2022 SAQ: "Name one potential complication of administering an iodinated contrast agent"). [1] [3]
Use MRI not CT for head/neck if imaging is needed. [1] No known risks to fetus with MRI in any trimester. [1] But generally good practice to avoid MRI in pregnancy if elective or in first trimester. [1] DO NOT give gadolinium-based contrast. [1]
Why no gadolinium? Gadolinium crosses the placenta and enters the fetal circulation, where it is excreted into the amniotic fluid. The fetus then swallows this fluid, and the gadolinium can remain in the amniotic-fetal circulation for an extended period. Animal studies show potential teratogenic effects.
Why MRI over CT? CT uses ionizing radiation, which carries theoretical risks to the fetus (particularly in the first trimester during organogenesis). MRI uses magnetic fields and radiofrequency pulses — no ionizing radiation.
Contraindications to MRI: [1]
| Absolute Contraindications | Conditional (may be MRI-compatible) |
|---|---|
| Metallic foreign body in eye (needs screening orbit CT) | Implantable drug infusion pump |
| Gastric reflux device | Epidural catheters |
| Insulin pumps | Feeding tubes |
| Temporary transvenous pacing leads | Neural stimulators (VNS, DBS, SCS) |
| Aneurysm clips | Cochlear implants |
| Shrapnel (depending on location) | Pacemaker/ICD |
Why are these dangerous? MRI uses a powerful magnetic field (typically 1.5–3 Tesla). Ferromagnetic objects can:
- Move — the magnet can pull on metallic implants, causing tissue damage (missile effect)
- Heat — radiofrequency pulses can induce currents in metallic objects, causing thermal injury
- Malfunction — electronic devices like pacemakers can be reprogrammed or inhibited
Metallic foreign body in eye is #1 on the list because even a tiny metallic fragment in the orbit can be pulled by the magnet, causing devastating eye injury. This is why patients with occupational metal exposure (grinding, welding) need a screening orbit X-ray or CT before MRI.
"Conditional" means the device has been tested and can be used in MRI under specific conditions (e.g., certain field strengths, specific absorption rate limits, with monitoring). This requires checking the specific device model and following manufacturer protocols.
While the lecture focuses on clinical scenarios, it does reference T1/T2 characteristics:
| Tissue | T1-Weighted | T2-Weighted |
|---|---|---|
| Fat | Bright | Bright |
| Water/CSF/Fluid | Dark | Very bright |
| Muscle | Intermediate | Dark |
| Cortical bone | Dark | Dark |
| Acute blood (deoxyhemoglobin) | Dark | Dark |
| Subacute blood (methemoglobin) | Bright | Variable |
| Gadolinium-enhanced tissue | Bright | N/A |
| Tumour (most) | Dark-intermediate | Bright |
Fat-saturation sequences: When you suppress the fat signal, any T1-bright lesion that disappears is confirmed as fat (e.g., lipoma). If it remains bright, consider blood, melanin, protein, or contrast enhancement.
Part 8: Integration with Related Lectures and Past Papers
GC 218 covers the clinical approach to neck masses (history, examination, differential diagnosis). This imaging lecture is the direct companion — once you've clinically assessed the mass, this lecture tells you what scan to order.
Deep neck space infections and pharyngeal/oral cavity cancers are the primary pathologies imaged in this lecture.
The adenoid cystic carcinoma case with CN-VII involvement directly connects to salivary gland malignancies and facial nerve palsy.
CT brain imaging principles (density, Hounsfield units) are the same as taught in this lecture for neck CT.
| Past Paper | Relevant Question | Connection |
|---|---|---|
| 2020 MCQ Q1 | Best imaging for intracranial haematoma in acute head injury → Non-contrast CT | Same principle: plain CT in acute setting |
| 2022 SAQ Q1 | Acute stroke first-line imaging → CT brain | CT first in emergency |
| 2022 SAQ Q1(e) | Complication of iodinated contrast → AKI/contrast-induced nephropathy, allergic reaction | Direct lecture content |
| 2024 SAQ Q3 | Sore throat + painful neck swelling → diagnosis, infective origin, investigation | CT neck with IV contrast, dental origin |
| 2024 MCQ Q59 | Central neck swelling moving with swallowing in 18 yo → thyroid | Not covered directly but thyroid is ruled out as differential |
| 2022 Minicase | Multinodular thyroid with retrosternal extension | Imaging: US thyroid + CT for retrosternal extent |
| 2023 MCQ Q64 | NPC management → IMRT (for localized NPC) | MRI staging for NPC taught in this lecture |
| 2025 MCQ Q21-25 | Head and neck tumour matching | Tests knowledge of NPC, papillary thyroid CA, parotid tumours |
| 2024 MCQ Q1 | CT-guided biopsy disadvantage → No real-time guidance | CT vs US guidance principles |
Summary Tables
| Clinical Scenario | First-Line Imaging | Why |
|---|---|---|
| Acute neck infection (adult) | CT neck WITH IV contrast | Fast, 24/7, shows abscess + source |
| Acute neck infection (child) | CT neck WITH IV contrast (ALARA) | Same indications; minimize dose |
| Suspected neoplasm — suprahyoid | MRI with contrast | Better soft tissue, perineural/intracranial spread |
| Suspected neoplasm — infrahyoid | CT with contrast | Less motion artifact, good for cartilage |
| NPC staging | MRI | Skull base, intracranial invasion |
| Suspected congenital mass (child) | Ultrasound | No radiation, solid vs cystic, Doppler |
| Vascular anomaly (child) | US + MRI | US initial, MRI for extent |
| Renal disease eGFR < 30 | CT without contrast / MRI without gadolinium | Avoid contrast toxicity |
| Pregnancy | MRI without gadolinium | No radiation, no gadolinium |
| Pathology | CT Appearance |
|---|---|
| Abscess | Rim-enhancing fluid collection |
| Cellulitis/inflammation | Fat stranding |
| Reactive lymphadenopathy | Enlarged, mildly enhancing nodes |
| Sialolith | Bright (calcified) stone in salivary duct/gland |
| Lipoma | Fat attenuation (-50 to -100 HU) |
| Malignant lymph node | Heterogeneous, irregular, may be cystic (HPV+), central necrosis |
Likely Exam Questions
-
A 45-year-old man presents with a 3-month history of painless left neck mass. He is a smoker and drinker. What is the most appropriate first-line imaging?
- A. Ultrasound neck
- B. CT neck without contrast
- C. CT neck with IV contrast
- D. MRI neck with and without contrast
- Answer: C (or D if suprahyoid). The key point is that CT/MRI with contrast is needed, not ultrasound alone. For a generic "neck mass suspected malignant" question without specifying location, CT with contrast is usually the answer in MCQ format. If the question specifies nasopharynx or oral cavity, MRI is better.
-
A 35-year-old man has a new cystic mass in the lateral neck. The most important diagnosis to exclude is:
- A. Branchial cleft cyst
- B. Thyroglossal duct cyst
- C. Cystic metastasis from HPV+ oropharyngeal SCC
- D. Lipoma
- Answer: C. This is the lecture's most emphasized pitfall.
-
Which of the following is a contraindication to administering IV iodinated contrast for CT?
- A. eGFR 45
- B. eGFR 25
- C. History of penicillin allergy
- D. Pregnancy (first trimester)
- Answer: B (eGFR < 30 is the cutoff). Pregnancy is a contraindication for CT itself (radiation), not specifically for iodinated contrast. Penicillin allergy is irrelevant.
-
A 65-year-old man presents with sore throat, fever, and painful neck swelling for 4 days. (a) What is the most likely diagnosis? (b) What is the most common infective origin? (c) What investigation would you order?
- (a) Deep neck space infection/abscess
- (b) Dental infection (odontogenic)
- (c) CT neck with IV contrast
-
Name three CT signs of neck infection.
- Fat stranding, rim-enhancing fluid collection (= abscess), reactive lymphadenopathy
-
A 25-year-old Chinese woman presents with a 3-month history of neck mass. NPC is suspected. (a) What is the best imaging modality? (b) Give two reasons why.
- (a) MRI neck with contrast
- (b) Superior soft tissue delineation for NPC staging; better detection of intracranial/perineural invasion; avoids radiation to radiosensitive thyroid in young patient
High Yield Summary
Imaging of the Head and Neck — Key Takeaways:
- Inflammatory masses → CT neck WITH IV contrast (fast, 24/7, shows abscess as rim-enhancing collection, check teeth for dental source)
- Neoplastic masses → CT or MRI with contrast (MRI for suprahyoid/NPC/perineural; CT for infrahyoid)
- Congenital masses → Ultrasound first (no radiation, solid vs cystic, Doppler); MRI for extent
- CRITICAL PITFALL: New cystic neck mass in adult ≠ branchial cleft cyst → MUST exclude HPV+ oropharyngeal SCC or thyroid cancer
- New neck mass in adult without infection = malignant UPO
- Contrast contraindications: eGFR < 30 (both CT iodinated and MRI gadolinium), documented allergy (premedicate if time allows), pregnancy (no gadolinium, no CT)
- MRI contraindications: metallic foreign body in eye, aneurysm clips, temporary pacing leads, insulin pumps
- ALARA principle in children; thyroid is most radiosensitive organ in neck
- CT density basics: Air/fat = dark; soft tissue/fluid = grey; bone/metal/contrast = bright
- T1 bright lesions: fat, subacute blood, melanin, protein, gadolinium → use fat suppression to differentiate
Active Recall - Imaging of the Head and Neck
[1] Lecture slides: GC 015. Imaging of the head and neck.pdf (all pages) [2] Senior notes: Ryan Ho Radiology.pdf (p.17, choice of modality) [3] Past papers: 2022 Fourth Summative SAQ.pdf (Q1 — stroke imaging, contrast complications) [4] Past papers: 2024 Fourth Summative SAQ.pdf (Q3 — sore throat, neck swelling, dental origin, CT) [5] Past papers: 2020 Fourth Summative Assessment MCQ paper.pdf (Q1 — CT for head injury) [6] Past papers: 2023 Fourth Summative MCQ.pdf (Q64 — NPC treatment) [7] Past papers: 2025 Fourth Summative MCQ.pdf (Q21-25 — head and neck tumour matching) [8] Past papers: 2024 Fourth Summative MCQ.pdf (Q59 — thyroid neck swelling; Q1 — CT-guided biopsy) [9] Senior notes: Ryan Ho Diagnostic Radiology.pdf (p.5, imaging modalities comparison) [10] Lecture slides: Cross-sectional 2 CT-MRI 2025_JH.pdf (CT/MRI basics) [11] Past papers: 2019 Fourth Summative Mini Case.pdf (p.10-12 — thyroid nodule workup) [12] Past papers: 2022 Fourth Summative Minicase.pdf (p.9-10 — multinodular goitre imaging)
GC014 How Can Interventional Radiology Help Patient Management
Interventional radiology uses image-guided, minimally invasive procedures—such as angiography, embolization, drainage, biopsy, and stenting—to diagnose and treat a wide range of conditions, thereby reducing surgical morbidity and improving patient management.
GC016 Radiology Of Common Medical And Surgical Problems
Radiology of common medical and surgical problems encompasses the use of imaging modalities such as X-ray, ultrasound, CT, and MRI to diagnose, evaluate, and guide management of frequently encountered clinical conditions across medical and surgical disciplines.