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JUNE 2026 - Paper 1: Complete Theory Answers

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QUESTION 1

a. Cranial USG Procedure (2 marks)

• High-frequency sector probe: 5-10 MHz (7.5 MHz most commonly used in neonates)
• A curvilinear or sector (phased array) transducer is preferred

• Supine, head in neutral or slightly extended position

1. Anterior Fontanelle (primary window): Open in neonates up to 9-18 months; gives best coronal and sagittal views
2. Posterior Fontanelle: For posterior fossa evaluation
3. Mastoid Fontanelle (posterolateral): Best for posterior fossa and cerebellum
4. Temporal window: For Doppler assessment of Circle of Willis

• Level of frontal horns
• Level of foramen of Monro (caudate-thalamus groove)
• Level of trigones/choroid plexus
• Level of posterior horn and cerebellum

• Midline sagittal (corpus callosum, vermis, 4th ventricle)
• Parasagittal views (caudothalamic groove - GMH site, choroid plexus)

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b. Grading of PVL (4 marks) and GMH (4 marks)

Grading of Periventricular Leukomalacia (PVL) - De Vries / Papile Modified Classification

• Mild: Minor signal abnormality, <3 foci
• Moderate: 3 or more foci, no cysts
• Severe: Extensive signal abnormality with or without cysts

• Increased periventricular echogenicity (flare) on coronal and parasagittal views
• Symmetrical "halo" around ventricles
• Cysts appear as anechoic areas replacing flare (after 2-3 weeks)
• Abnormal ventricular shape - irregular outline, ex-vacuo dilatation later
• Delayed myelination on follow-up MRI

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Grading of Germinal Matrix Hemorrhage (GMH) / Intraventricular Hemorrhage (IVH) - Papile Classification (1978)

• Acute hemorrhage: Hyperechoic (echogenic)
• Subacute (1-2 weeks): Becomes isoechoic then hypoechoic
• Chronic: Porencephalic cyst (anechoic)
• Best seen in parasagittal views at caudothalamic groove

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QUESTION 2

a. Imaging Features in a 7-year-old Male with Pyogenic Osteomyelitis (7 marks)

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• Soft tissue swelling - obliteration of fat planes around bone
• Loss of soft tissue planes
• Periosteal reaction may be absent early

• Lytic metaphyseal lesion (permeative pattern)
• Periosteal reaction - aggressive (laminated/"onion skin" or Codman's triangle)
• Cortical destruction
• Subperiosteal abscess (periosteal elevation)
• Soft tissue mass adjacent to bone
• Sequestrum (dead bone: dense avascular fragment)
• Involucrum (periosteal new bone surrounding sequestrum)
• Cloaca (sinus tract through cortex)
• Brodie's abscess (loculated lucency with sclerotic rim - subacute form)

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• Earliest modality to show subperiosteal abscess (hyperechoic or complex fluid between periosteum and cortex)
• Soft tissue edema and deep tissue abscess
• Periosteal elevation - distance >2mm is significant
• Power Doppler: Increased vascularity around abscess wall
• Cartilage involvement in neonates and young children
• Useful for image-guided aspiration

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• 3-phase bone scan: sensitive within 24-72 hours
• Phase 1 (flow) and Phase 2 (blood pool): Increased activity in inflammation
• Phase 3 (delayed): Increased uptake in osteomyelitis
• False negative in neonates (avascular necrosis pattern - "cold" lesion)
• Sensitivity ~80-90%; helpful for multifocal disease

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• Better bone detail than MRI
• Shows: cortical destruction, periosteal reaction, sequestrum, involucrum, cloaca
• Soft tissue abscess
• Intramedullary gas (very specific)
• Used for guided biopsy
• Limitation: radiation dose in children

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• T1W: Normal marrow replaced by low signal
• T2W/STIR: High signal in medullary cavity (edema/pus)
• Fat-suppressed T2: Best for marrow edema
• T1W+Gd contrast: Rim-enhancing abscess; differentiates phlegmon from abscess

• Marrow edema: Low T1, high T2/STIR signal in metaphysis
• Phlegmon: Ill-defined marrow abnormality without rim enhancement
• Abscess: Well-defined rim-enhancing collection (T1 dark center, T2 bright)
• Subperiosteal abscess: Lenticular fluid collection under periosteum
• Periosteal reaction and soft tissue edema
• Epiphyseal spread (via cartilaginous channels in children <18 months)
• Joint involvement (septic arthritis)
• Sinus tract: Linear T2 high signal channel through cortex to skin

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b. Differential Diagnoses of Pyogenic Osteomyelitis in Children (3 marks)

1. Ewing's Sarcoma: Aggressive periosteal reaction (sunburst/onion skin), permeative lysis in diaphysis, large soft tissue mass, systemic symptoms mimic infection
2. Langerhans Cell Histiocytosis (LCH): Punched-out lytic lesions, vertebra plana, periosteal reaction; eosinophilic granuloma
3. Leukemia: Permeative lysis, metaphyseal lucent bands, periosteal reaction, multifocal
4. Septic Arthritis (contiguous spread): Joint space widening, periarticular swelling
5. Bone lymphoma: Aggressive permeative pattern
6. Stress fracture: History of physical activity, no systemic signs
7. Chronic recurrent multifocal osteomyelitis (CRMO): Multifocal, non-infective inflammatory

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QUESTION 3

Acromegaly: Imaging Workup (10 marks)

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I. MRI Pituitary (Investigation of Choice)

• 3T MRI preferred; thin slices (2-3mm) through pituitary fossa
• Coronal and sagittal T1W, T2W
• Dynamic contrast-enhanced coronal T1W (key for microadenoma)
• T2W: Adenoma often isointense to slightly hypointense to brain
• Post-gadolinium: Normal pituitary enhances brightly; adenoma enhances less (hypointense in early phase)

• Macroadenoma (>10mm): Most common in acromegaly
  • Enlargement of pituitary fossa/sella turcica
  • Suprasellar extension - "snowman" or "figure of 8" appearance
  • Optic chiasm compression (bitemporal hemianopia)
  • Cavernous sinus invasion (encircling carotid artery - Knosp grading)
  • Sphenoid sinus invasion
  • T1: Iso/hypointense; T2: Variable; post-contrast: Heterogeneous enhancement
• Microadenoma (<10mm): Less common in acromegaly
  • Off-center pituitary gland
  • Contralateral tilt of stalk
  • Asymmetric enlargement of sella

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II. Skull and Facial Bones (Plain X-ray)

• Skull X-ray:
  • Enlarged sella turcica (>23mm wide, >17mm deep - "ballooned sella")
  • Double floor of sella (adenoma extension)
  • Thickening of calvarium (frontal bone)
  • Increased skull base thickness
  • Prognathism - elongation of mandible
  • Enlarged frontal sinuses (pneumosinus dilatans)
  • Increased skull density
• Facial bones:
  • Prognathism (protruding jaw)
  • Enlarged mandibular condyles
  • Widened mandibular angle
  • Widely spaced teeth (diastema)

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III. Hands and Feet (X-ray)

• Broad, "spade-like" hands
• Increased thickness of soft tissue (soft tissue hypertrophy)
• "Arrowhead" or "spade-like" terminal phalangeal tufts (widened)
• Widened joint spaces (cartilage hypertrophy)
• Premature osteoarthritis
• Sesamoid index (sum of sesamoid dimensions) >40mm² in women, >72mm² in men - diagnostic

• Heel pad thickness >21mm in females, >23mm in males = DIAGNOSTIC (most reliable plain film sign)
• Wide, square-shaped metatarsals
• Soft tissue hypertrophy

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IV. Spine (X-ray / MRI)

• Posterior vertebral body scalloping (due to dural ectasia)
• Increased anteroposterior diameter of vertebral bodies
• Disc space widening
• Dorsal kyphosis
• Vertebral osteophytes (spondylosis)
• Spinal canal widening

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V. Chest X-ray

• Cardiomegaly (acromegalic cardiomyopathy)
• Rib thickening/elongation
• Sternal deformity
• Barrel chest appearance

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VI. Other Imaging

• CT Chest/Abdomen: To detect ectopic GH-secreting tumor (rare source - bronchial carcinoid, pancreatic tumor)
• Echocardiography: Concentric LVH, diastolic dysfunction, valvular disease
• Somatostatin receptor scintigraphy / Ga-68 DOTATATE PET-CT: For ectopic GHRH/GH source
• CT sinuses: Enlarged sinuses (diagnostic hallmark)
• Lateral cervical spine X-ray: Atlantoaxial subluxation (due to ligamentous laxity)
• DXA scan: Osteoporosis assessment (hypogonadism secondary to tumor compression)

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Summary of Key Diagnostic Imaging

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QUESTION 4

a. Glioma Imaging Features (5 marks)

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• Hypodense to isodense lesion
• No significant mass effect
• Absent or minimal contrast enhancement (blood-brain barrier intact)
• Calcification in ~20% (especially oligodendroglioma)
• No edema or minimal edema

• T1W: Hypointense (dark)
• T2W/FLAIR: Hyperintense (bright) - "bright T2 lesion"
• No or minimal enhancement on T1W+Gd
• Cortical expansion without mass effect
• Smooth borders (relatively)
• No restricted diffusion (high ADC values)
• Low rCBV on perfusion (low vascularity)
• DWI: No restriction
• MRS: Mildly elevated Cho, reduced NAA, no lactate

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• Heterogeneous hypodense/isodense mass
• Vivid ring enhancement (thick, irregular) post contrast
• Central necrosis (hypodense)
• Surrounding vasogenic edema (finger-like white matter edema)
• Mass effect - midline shift, herniation
• "Butterfly glioma" - crosses corpus callosum to contralateral side (diagnostic feature)
• Hemorrhagic foci (heterogeneous density)
• Multifocal in 2-5%

• T1W: Hypointense, central dark necrosis, surrounding mass
• T2W: Heterogeneous hyperintense mass with bright edema; necrosis dark
• FLAIR: Extensive surrounding hyperintensity (edema + infiltrating tumor)
• T1W+Gd: Irregular, thick ring enhancement with non-enhancing necrotic center
• DWI: Restricted diffusion in cellular viable tumor portions (low ADC)
• SWI/GRE: Hemorrhagic foci - "blooming" artifacts
• MRS: High Cho/NAA ratio (>2), elevated Cho peak, reduced NAA, lipid/lactate peak (necrosis)
• Perfusion (DSC): High rCBV in enhancing rim (tumor) - >2x normal white matter

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• Cortical-based "cortical" location (frontal most common)
• Calcification in 70-90% (CT: "gyriform" calcification)
• Minimal/absent edema
• 1p/19q co-deletion (molecular marker - better prognosis)
• T2/FLAIR hyperintense, minimal enhancement

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• 4th ventricle (posterior fossa) in children; spinal canal and supratentorial in adults
• "Plastic" tumor - molds to CSF spaces, squeezes through foramina of Luschka/Magendie
• Mixed density/signal (cysts, calcification, hemorrhage)
• Heterogeneous enhancement
• Can drop metastases in spine ("drop mets")

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b. Role of MR Perfusion in Glioma (5 marks)

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1. DSC (Dynamic Susceptibility Contrast) Perfusion:
   • Most widely used
   • Uses T2* signal drop after gadolinium bolus
   • Measures: rCBV (relative cerebral blood volume), rCBF, MTT
   • Key parameter: rCBV (reflects angiogenesis)
2. DCE (Dynamic Contrast Enhanced) Perfusion:
   • T1-based; measures Ktrans (volume transfer coefficient)
   • Reflects capillary permeability
   • Useful for anti-VEGF therapy monitoring
3. ASL (Arterial Spin Labeling):
   • No contrast needed
   • Labels blood water protons as endogenous tracer
   • Measures CBF
   • Useful in pediatric patients

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• High-grade glioma: rCBV >1.75-2.0x (elevated) - high angiogenesis
• Low-grade glioma: rCBV <1.5x - low vascularity
• Correlation: rCBV correlates with histological grade and VEGF expression

• Radiation necrosis: Low rCBV (<0.6x), low Ktrans (disrupted but hypovascular)
• Tumor recurrence/progression: High rCBV (>1.5-2.0x), high Ktrans
• This is crucial post-treatment follow-up: MRI alone cannot distinguish

• Guides stereotactic biopsy to the highest-grade, most vascular portion of the tumor (hot spot)
• Prevents sampling error (avoiding necrotic/non-diagnostic areas)

• "Pseudo-progression" (early post-treatment): Enhancement increases transiently but rCBV is low - favors radiation effect
• True progression: Increasing rCBV confirms tumor growth
• Anti-VEGF therapy monitoring: Normalization of rCBV/Ktrans indicates response; re-elevation indicates failure

• Non-enhancing T2/FLAIR hyperintense region: Perfusion shows elevated rCBV - indicates infiltrating tumor beyond enhancing margin (relevant for surgical planning)

• Higher rCBV correlates with shorter overall survival in GBM
• Helps stratify patients for aggressive vs. palliative management

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QUESTION 5

a. Enumerate Salivary Gland Tumors (2 marks)

1. Pleomorphic adenoma (mixed tumor) - Most common (65-70%)
2. Warthin's tumor (papillary cystadenoma lymphomatosum)
3. Oncocytoma (oxyphilic adenoma)
4. Basal cell adenoma
5. Myoepithelioma
6. Canalicular adenoma
7. Ductal papilloma
8. Hemangioma (children)
9. Lipoma

1. Mucoepidermoid carcinoma (Most common malignant - parotid)
2. Adenoid cystic carcinoma (Most common - submandibular/minor glands; perineural spread)
3. Carcinoma ex-pleomorphic adenoma (malignant transformation)
4. Acinic cell carcinoma
5. Polymorphous adenocarcinoma
6. Squamous cell carcinoma (primary)
7. Lymphoma (primary or secondary)
8. Metastases

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b. Imaging of Pleomorphic Adenoma (4 marks)

• Well-defined, smoothly marginated, hypoechoic mass
• Lobulated contour (lobulated/bosselated border)
• Posterior acoustic enhancement (soft tissue mass)
• Internal homogeneous texture when small; heterogeneous when large
• Color Doppler: Internal vascularity (central and peripheral)

• Well-circumscribed, homogeneous or slightly heterogeneous mass
• Isodense to soft tissue; hypodense areas = myxoid stroma
• Moderate, homogeneous enhancement post-contrast
• Calcification in ~20%
• No invasion of surrounding structures
• Facial nerve plane preserved

• T1W: Isointense to hypointense to muscle
• T2W: Characteristically VERY BRIGHT (hyperintense) - due to high water content (myxoid/chondroid stroma) - "light bulb" T2 brightness
• T1W+Gd: Moderate enhancement; may show capsular enhancement
• Well-defined smooth/lobulated margins
• DWI: Intermediate to low diffusion restriction (ADC ~1.4-1.6 x 10-3 mm²/s)
• Capsule visible as T1/T2 dark rim

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c. Imaging of Warthin's Tumor (4 marks)

• Well-defined, smoothly marginated
• Mixed echotexture: Solid and cystic components
• Multiple anechoic cysts within hypoechoic solid stroma ("sponge-like" appearance)
• Posterior acoustic enhancement
• Color Doppler: Increased vascularity (hilar pattern)

• Well-defined parotid mass
• Mixed density - solid component isodense + cystic areas
• Vivid enhancement of solid portions
• May appear bilateral in 10% cases (virtually diagnostic when bilateral in tail of parotid)
• No calcification (unlike pleomorphic adenoma)
• Slightly higher density than pleomorphic adenoma (less water content)

• T1W: Intermediate-to-high signal (protein-rich cystic fluid - high T1) - key distinguishing feature from pleomorphic adenoma
• T2W: Heterogeneous - intermediate (NOT as bright as pleomorphic adenoma)
• T1W+Gd: Enhancement of solid portions; cysts do not enhance
• DWI: Variable ADC; intermediate restriction
• High T1 signal (due to mucin/proteinaceous content) differentiates from pleomorphic adenoma

• Tc-99m pertechnetate scan: HOT SPOT (increased uptake) in Warthin's - due to oncocytic cells concentrating pertechnetate; pathognomonic feature

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QUESTION 6

a. Enumerate Causes of Leukokoria (2 marks)

1. Retinoblastoma (most common cause in children - must exclude first)
2. Persistent Fetal Vasculature (PFV) / Persistent Hyperplastic Primary Vitreous (PHPV)
3. Coats' disease (retinal telangiectasia with exudative retinal detachment)
4. Congenital cataract
5. Retinopathy of prematurity (ROP) - Stage 4/5
6. Toxocariasis (ocular larva migrans)
7. Vitreous hemorrhage (organizing)
8. Endophthalmitis
9. Norrie disease
10. Familial exudative vitreoretinopathy (FEVR)
11. Myelinated nerve fibers
12. Coloboma

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b. USG Findings of Leukokoria (4 marks)

• Intraocular mass with calcifications (80-90% - highly echogenic foci with posterior acoustic shadowing)
• Hyperdense solid mass in posterior segment
• Detached retina may be visible
• Color Doppler: Internal vascularity

• Microphthalmic eye (small eye - key distinguishing feature)
• Echogenic retrolental membrane (Cloquet's canal remnant)
• No calcification
• Funnel-shaped retinal detachment
• Linear echogenic strand from lens to disc (persistent hyaloid vascularity)
• Color Doppler: May show flow in hyaloid artery

• Subretinal exudate - highly echogenic material in vitreous/subretinal space
• Retinal detachment (exudative - V-shaped or total)
• No calcification (unlike retinoblastoma)
• Normal-sized eye
• No intraocular mass
• Yellow subretinal fluid on ultrasound (proteinaceous)

• Peripheral granuloma or vitreous mass
• Echogenic focus at posterior pole or periphery
• Vitreous membranes/strands
• Traction retinal detachment

• Funnel-shaped or total retinal detachment
• No calcification
• Premature infant history

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c. Retinoblastoma CT Findings (4 marks)

1. Calcification (PATHOGNOMONIC):
   • Present in 80-95% of cases
   • Irregular, "chunky" or "flocculent" calcification within intraocular mass
   • Best demonstrated on CT
   • Calcification in an intraocular mass in a child <3 years = retinoblastoma until proven otherwise
2. Intraocular Mass:
   • Hyperdense to vitreous on pre-contrast CT
   • Arises from retina (posterior segment)
   • May be endophytic (into vitreous), exophytic (into subretinal space), or mixed
   • "Snowball-like" calcification pattern
3. Retinal Detachment:
   • Subretinal fluid/exudate
   • Detached retina visible as linear density
4. Contrast Enhancement:
   • Post-contrast: Heterogeneous enhancement of solid tumor component
   • Calcified areas do not enhance
5. Size and Extension:
   • Small tumors confined to globe (Stage I/II)
   • Choroidal invasion, scleral invasion (intermediate stages)
   • Optic nerve extension: Critical - thickening/enhancement of optic nerve behind globe
   • Extraocular extension: Proptosis, periorbital soft tissue mass
6. Orbital and Intracranial Extension:
   • Invasion through sclera into orbit
   • Intracranial extension via optic nerve to chiasm and brain (Stage V)
   • Pineal region mass ("trilateral retinoblastoma" - bilateral RB + pineoblastoma)
   • Leptomeningeal spread
7. Bilateral Disease:
   • Both eyes should always be imaged
   • Heritable form (Rb1 gene mutation) - bilateral in 25%, higher risk of secondary tumors

• PFV: No calcification, microphthalmic eye, retrolental membrane
• Coats' disease: No calcification, no intraocular mass
• Toxocariasis: No calcification, older child, peripheral lesion

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QUESTION 7

a. Anatomy of Brachial Plexus (3 marks)

Roots → Trunks → Divisions → Cords → Branches

• Emerge between anterior and middle scalene muscles (scalenus anterior and medius)
• "5 roots between the scalenes"

• Upper (superior) trunk: C5 + C6
• Middle trunk: C7 alone
• Lower (inferior) trunk: C8 + T1
• Located in posterior triangle of neck

• Upper trunk → anterior + posterior
• Middle trunk → anterior + posterior
• Lower trunk → anterior + posterior

• Lateral cord: Anterior divisions of upper + middle trunks (C5,6,7)
• Medial cord: Anterior division of lower trunk (C8, T1)
• Posterior cord: ALL THREE posterior divisions (C5,6,7,8,T1)
• Located in axilla (retropectoral space)

• Musculocutaneous nerve (C5,6,7) - from lateral cord
• Median nerve (C5-T1) - from lateral + medial cords (dual root)
• Ulnar nerve (C8,T1) - from medial cord
• Radial nerve (C5-T1) - from posterior cord
• Axillary nerve (C5,6) - from posterior cord

• Long thoracic nerve (C5,6,7 - roots): Serratus anterior
• Dorsal scapular nerve (C5): Rhomboids
• Suprascapular nerve (C5,6 - upper trunk): Supraspinatus + infraspinatus
• Thoracodorsal nerve (C6,7,8 - posterior cord): Latissimus dorsi

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b. Role of MR Neurography in Brachial Plexopathy (7 marks)

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• 3T MRI preferred (higher SNR)
• Coil: Phased array surface coil / neurovascular coil
• Sequences:
  • Coronal STIR (Short TI Inversion Recovery): T2-weighted with fat suppression - abnormal nerves appear bright
  • 3D SPACE/CUBE/VISTA (3D FSE): Isotropic voxels, multiplanar reformats
  • T1W: For anatomical localization and mass lesions
  • DWI of nerves: Fascicular pattern; ADC changes in injury
  • DTI (Diffusion Tensor Imaging): Tractography of plexus; FA (fractional anisotropy) changes in injury
  • DWIBS (Diffusion Weighted Whole Body Imaging with Background Suppression): Like "MR PET" for nerve tumors
  • MR myelography: Intrathecal root avulsion (pseudomeningoceles)

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• Nerves appear as linear, smoothly coursing structures
• Slight T2/STIR hypersignal compared to muscle
• Uniform caliber
• Preserved fascicular architecture

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• Pre-ganglionic (root avulsion):
  • Pseudomeningocele (CSF-filled dural sleeve at avulsion site - diagnostic)
  • Bare rootlets in thecal sac (empty root sleeve)
  • Best seen on MR myelography / CT myelography
  • Empty root sleeve on coronal images
  • Cord injury possible (contusion/signal change)
• Post-ganglionic:
  • Nerve discontinuity, neuroma formation
  • T2/STIR hyperintensity of involved nerves
  • Nerve retraction with fibrotic scarring
  • Muscle denervation changes: STIR hyperintensity in acute (denervation edema), fatty atrophy in chronic

• Lung apex (Pancoast tumor): T1W hypointense mass invading lower trunk (C8,T1)
• Direct mass infiltration of plexus; nerve thickening/displacement
• Lymph node involvement (axillary, supraclavicular)
• MRN shows: Asymmetric nerve enlargement, T2 hyperintensity, loss of fascicular pattern
• Carcinoma of breast: Direct extension or nodal compression
• Nerve sheath tumors (neurofibroma, schwannoma): Well-defined T2 bright fusiform masses, "target sign" (central T2 dark, peripheral T2 bright)

• Common after breast/lung radiation
• MRN: Diffuse T2 hyperintensity of all nerves within radiation field (vs. neoplasm which is focal/asymmetric)
• No discrete mass
• Fibrosis: Loss of fat planes, tethering
• Key: Radiation affects entire field; tumor affects specific trunks/cords
• Gadolinium: No enhancement (radiation necrosis) vs. tumor (enhancement)

• Vascular MRI/MRA: Subclavian artery compression
• Nerve compression: T2 hyperintensity, caliber change
• Dynamic MRN with arm positioning (elevated vs. neutral)
• Accessory rib (cervical rib) - seen on plain X-ray and MRI

• MRN: Segmental T2 hyperintensity ("beaded pattern")
• Hourglass-like constriction (fascicular constriction) - pathognomonic
• Denervation in muscles (STIR hyperintensity)
• Often self-limiting

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• FA (Fractional Anisotropy) reduced in injured nerves
• ADC elevated in inflammatory/edematous nerves
• 3D fiber tractography: Visualizes nerve continuity, guides surgical exploration
• Predicts surgical prognosis (complete avulsion vs. partial injury)

• Guides surgical planning (neurolysis vs. nerve grafting vs. nerve transfer)
• Distinguishes pre vs. post-ganglionic injury (critical for prognosis)
• Differentiates tumor vs. radiation vs. traumatic plexopathy
• Identifies treatable compressive lesion (TOS, mass)

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QUESTION 8

Rheumatoid Arthritis (RA) - Imaging

a. Imaging Features in the Hand (4 marks)

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1. Periarticular soft tissue swelling - fusiform swelling around MCP and PIP joints
2. Periarticular osteopenia - juxta-articular bone demineralization
3. Joint effusion - soft tissue density in joint space

• Swan neck deformity (PIP hyperextension, DIP flexion)
• Boutonniere deformity (PIP flexion, DIP hyperextension)
• Ulnar deviation/drift at MCP joints
• Z-thumb deformity (MCP flexion + IP hyperextension)
• "Piano key" deformity of ulnar head

1. Subluxation at MCP joints (volar subluxation)
2. Ankylosis (bony fusion - late stage, especially in wrist carpus)
3. Carpal crowding - collapse of carpal height
4. Boutonniere deformity of fingers

• Synovial thickening (pannus): Hypoechoic to anechoic thickening in joint
• Joint effusion: Anechoic fluid
• Power Doppler: Active synovitis - increased vascularity in pannus (confirms active disease)
• Erosions: Cortical breaks at bare areas
• Tenosynovitis: Fluid around tendons (flexor tendons)
• Extra-articular: Rheumatoid nodules (hypoechoic/anechoic subcutaneous nodules)

• Synovitis: T1+Gd enhancement of thickened synovium (pannus)
• Bone marrow edema (STIR/T2): Precedes erosions on X-ray by months
• Erosions: T1 cortical defect filled with T2 bright pannus
• Cartilage loss: T1W thin/absent cartilage
• Tendon rupture/tenosynovitis: T2 hyperintense fluid around tendon
• MRI can detect erosions 6-12 months before X-ray

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b. Imaging Features in the Wrist (4 marks)

1. Carpal bones:
   • Erosions at carpal bones - especially triquetrum, pisiform, scaphoid (bare area erosions)
   • Uniform joint space narrowing of radiocarpal and intercarpal joints
   • Periarticular osteoporosis
   • Carpal crowding/collapse (decreased carpal height ratio)
   • Bony ankylosis in late disease (fused carpal bones - "carpal coalition")
2. Distal Radioulnar Joint (DRUJ):
   • DRUJ erosions/widening
   • "Piano key" deformity: Dorsal subluxation of distal ulna
   • Caput ulnae syndrome: Erosive destruction of distal ulna with dorsal subluxation
3. Radiocarpal joint:
   • Uniform joint space narrowing
   • Radial deviation of carpus (while fingers ulnar deviate)
   • Erosions of radial styloid process
4. Tenosynovitis:
   • Extensor tendon compartments (EPL, EDC) - USG: Fluid sheath
   • Extensor carpi ulnaris (ECU) most commonly involved
5. Carpal tunnel syndrome: Secondary RA involvement, USG: Enlarged median nerve, flexor tenosynovitis

• DRUJ synovitis and effusion
• TFCC (triangular fibrocartilage complex) tear/erosion
• Ulnar styloid erosion
• Carpal bone marrow edema
• Tendon rupture (Vaughan-Jackson syndrome: sequential extensor tendon ruptures beginning at EDM)
• Extensor and flexor tenosynovitis
• Carpal tunnel median nerve compression

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c. Differential Diagnoses of RA (2 marks)

1. Osteoarthritis (OA): Asymmetric joint space narrowing, osteophytes, subchondral sclerosis, no erosions; affects DIP > PIP > 1st CMC (spares MCP); no osteoporosis
2. Psoriatic Arthritis: "Ray" distribution, DIP involvement, "pencil-in-cup" deformity, sausage digits, new bone formation (periostitis), HLA-B27
3. Gout: Tophi (punched-out erosions with overhanging edges - "rat bite"), asymmetric, 1st MTP joint (podagra), no osteoporosis
4. Systemic Lupus Erythematosus (SLE/Jaccoud's arthropathy): Reducible deformities without erosions; periarticular soft tissue changes; no true erosions
5. Reactive Arthritis (Reiter's syndrome): Lower limbs predominantly, calcaneal spur, HLA-B27
6. Juvenile Idiopathic Arthritis (JIA): Age <16, periosteal reaction, overgrowth of epiphyses, micrognathia (TMJ involvement)

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QUESTION 9

a. Enumerate Extradural Spinal Tumors (3 marks)

1. Metastases (most common extradural mass - breast, lung, prostate, kidney, thyroid)
2. Multiple myeloma / plasmacytoma
3. Osteosarcoma
4. Chordoma (sacrococcygeal)
5. Giant cell tumor (sacrum, vertebral body)
6. Osteoblastoma
7. Aneurysmal bone cyst
8. Hemangioma (vertebral)
9. Ewing's sarcoma

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b. Imaging Features of Extradural Spinal Tumors (4 marks)

• Vertebral body collapse/destruction
• Pedicle erosion ("winking owl" sign - loss of pedicle shadow on AP view)
• Paravertebral soft tissue mass
• Sclerotic vertebral body (blastic metastasis - prostate, breast)
• Lytic vertebral body (lytic metastasis - lung, kidney)

• Vertebral body/pedicle destruction
• Paravertebral/epidural soft tissue mass
• Extent of cortical destruction
• Soft tissue extension into spinal canal
• Heterogeneous mass with areas of lysis/sclerosis
• Metastases: Multiple level involvement
• Chordoma: Sacrococcygeal destructive mass, calcification, "sentinel" lesion
• Epidural abscess: Rim-enhancing fluid collection

• Metastases:
  • T1W: Low signal replacing normal fatty marrow (high T1)
  • T2W: High signal (most)
  • STIR: High signal (sensitive for marrow replacement)
  • T1+Gd: Enhancement of tumor
  • "Halo sign" on STIR: Surrounding marrow edema
  • Convex posterior cortex/epidural disease
  • Posterior cortical destruction
  • Epidural component: Soft tissue epidural mass
• Epidural space (extradural) characteristics:
  • Mass is OUTSIDE the dura: CSF signal displaced inward
  • "Tenting" of the dura
  • Normal epidural fat obliterated
  • No intradural contrast pooling

• Metastases: Multiple levels, T1 low replacing normal bright marrow, gadolinium enhancement
• Epidural hematoma: Biconvex, T1 bright (acute/subacute), T2 variable; post-traumatic
• Epidural abscess: Rim-enhancing dorsal epidural collection; T2 bright; adjacent spondylodiscitis
• Hemangioma: "Corduroy" pattern on X-ray, T1 AND T2 bright (fat and vascular channels)
• Chordoma: T2 very bright (notochordal tissue), low T1, enhances moderately; presacral mass

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c. Difference Between Intradural and Extradural Spinal Tumors (4 marks)

• Extradural: The dura drapes over the mass ("tenting sign"); epidural fat obliterated; posterior cortical wall destruction of vertebral body; mass spans multiple levels.
• Intradural Extramedullary (IDEM - e.g., meningioma, schwannoma):
  • "Golf tee sign" on myelography
  • "Cap sign" on MRI (CSF above and below lesion)
  • Spinal cord displaced to contralateral side
  • Acute angle of the mass with cord/dura
  • Homogeneous enhancement; dural tail (meningioma)
• Intramedullary (IMT - e.g., ependymoma, astrocytoma):
  • Cord expansion and widening
  • Syrinx/cyst within or adjacent to tumor
  • Ependymoma: Central canal origin, well-defined, "cap sign" (hemosiderin at poles), homogeneous enhancement
  • Astrocytoma: Ill-defined, eccentric, heterogeneous, indistinct margins

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QUESTION 10

a. Moon Mass Enhancement (5 marks)

• Uniform enhancement throughout the mass
• Seen in: Meningioma (intracranial), acoustic schwannoma, lymphoma, carcinoid
• Indicates uniform vascularity and intact blood-brain barrier breakdown

• Enhancing rim with non-enhancing center (necrotic/cystic center)
• Seen in:
  • High-grade glioma (GBM) - thick, irregular ring
  • Brain abscess - thin, smooth ring
  • Metastasis - thick irregular ring
  • MS plaques - "open ring" sign (incomplete ring)
  • Lymphoma - ring or homogeneous
  • Tumefactive MS - "open ring" sign (open towards cortex)

• Mixed pattern due to necrosis, cysts, hemorrhage
• Seen in: GBM, metastases, mixed germ cell tumors

• Intact blood-brain barrier
• Seen in: Low-grade glioma, epidermoid cyst, arachnoid cyst

• Discrete nodule(s) with enhancement
• Seen in: Pilocytic astrocytoma (enhancing mural nodule in cystic tumor), hemangioblastoma

• Linear enhancement of adjacent dura
• Seen in: Meningioma (pathognomonic but not specific)

• Sulcal/pial enhancement
• Seen in: Meningitis, leptomeningeal carcinomatosis, sarcoidosis

• Enhancement of surrounding tissue
• Active inflammation around abscess

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b. 40-year-old Woman with Unilateral Nipple Discharge - Imaging Workup

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• Intraductal papilloma (most common cause of unilateral, bloody/serous discharge)
• Ductal ectasia
• Breast carcinoma (especially ductal carcinoma)
• Papillomatosis
• Fibrocystic change

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• Retroareolar region - focused evaluation of subareolar ducts
• Findings suggesting intraductal lesion:
  • Retroareolar density/mass
  • Ductal dilation
  • Intraductal calcification (rod-shaped, secretory)
  • Duct ectasia (tubular densities converging on nipple)
  • Intraluminal mass/calcification
• Post-contrast digital mammography if standard is inconclusive

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• High-frequency linear probe (10-15 MHz)
• Focused retroareolar/subareolar scan
• Intraductal papilloma:
  • Dilated duct with intraluminal echogenic nodule/mass
  • Duct diameter >2mm = abnormal
  • Color Doppler: Vascularity within papilloma
  • Heterogeneous intraductal lesion
• Ductal ectasia: Dilated, tortuous retroareolar ducts without mass
• Malignancy: Irregular hypoechoic mass; ductal involvement; axillary adenopathy
• Compression over the subareolar area may reproduce discharge during scan

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• Cannulation of discharging duct orifice with fine (30G) cannula
• Injection of water-soluble contrast (0.1-0.5 mL)
• Imaging in CC and lateral projections
• Findings:
  • Intraductal filling defect = papilloma (smooth, round intraluminal filling defect)
  • Cut-off/obstruction = carcinoma or large papilloma
  • Duct irregularity = papillomatosis or DCIS
  • Normal duct = benign (ductal ectasia)
• Limitation: Painful; operator-dependent; being replaced by MRI

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• 1.5T or 3T; bilateral breast coil
• T2W: Ductal anatomy; fluid/cysts
• Fat-suppressed T1W pre and post-gadolinium (dynamic subtraction series)
• DWI: Lesion characterization

• Heavily T2-weighted sequence (without contrast)
• Shows dilated ducts as bright tubular structures
• Intraductal masses as filling defects

• Papilloma: Enhancing intraductal nodule with kinetic curve (rapid initial uptake, plateau/washout)
• DCIS: Non-mass enhancement - linear/segmental clumped enhancement along duct
• Invasive carcinoma: Irregular enhancing mass; rapid initial uptake + washout kinetics (Type III curve)
• Ductal ectasia: Non-enhancing dilated ducts

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• Ductoscopy: Direct microendoscopic visualization of discharging duct; biopsy
• USG-guided core biopsy: For discrete lesions visible on ultrasound
• Vacuum-assisted biopsy (stereotactic): For calcifications
• Surgical excision (microdochectomy): If imaging-negative but discharge persists, or confirmed papilloma

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Clinical examination + discharge cytology
        ↓
Mammography (bilateral FFDM)
        ↓
Targeted Breast Ultrasound (subareolar)
        ↓
If lesion found: USG-guided biopsy
If no lesion: Galactography / MR ductography
        ↓
Lesion identified → Core biopsy / Ductoscopy
        ↓
Surgical excision if papilloma/malignancy confirmed

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QUESTION 10 (Corrected)

a. Non-Mass Enhancement (NME) on Breast MRI (5 marks)

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ACR BI-RADS Lexicon for NME

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1. DISTRIBUTION of NME

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2. INTERNAL ENHANCEMENT PATTERN of NME

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Kinetic Curve Analysis in NME

• Type I (Progressive): Gradual rise - favors benign
• Type II (Plateau): Rise then flat - intermediate
• Type III (Washout): Rise then fall - favors malignancy
• Note: Kinetics are less reliable in NME compared to mass lesions; morphology and distribution dominate the assessment

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Pathological Correlates of NME

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MRI Protocol for NME Evaluation

• 1.5T or 3T with dedicated bilateral breast coil
• T1W fat-suppressed pre-contrast: Baseline
• Dynamic DCE (T1W+Gd): Early (90 sec), delayed (3-5 min) post-contrast
• Subtraction images: Removes background fat signal; highlights enhancement
• T2W: Assess for associated cysts, edema
• DWI/ADC: Restricted diffusion (low ADC) in malignant NME; ADC <1.2 x 10⁻³ mm²/s suspicious
• MIP (Maximum Intensity Projection): 3D overview of all enhancement

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Differential Diagnosis of NME

• DCIS (most common malignant cause of NME)
• Invasive ductal carcinoma (IDC) - non-mass pattern
• Invasive lobular carcinoma (ILC) - frequently presents as NME
• Inflammatory carcinoma

• Fibrocystic change / adenosis
• Fibrocystic changes with usual ductal hyperplasia
• Mastitis / inflammatory change
• Sclerosing adenosis
• Fat necrosis (post-surgical/post-radiation)
• Hormonal enhancement (normal background parenchymal enhancement)
• Fibroadenomatosis

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BI-RADS Assessment and Management

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Key Distinguishing Points: NME vs. Mass

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Clinical Importance

• NME accounts for approximately 15-30% of all enhancing lesions on breast MRI
• Malignancy rate in NME: 25-40% overall
• Segmental + clumped pattern carries the highest malignancy risk (~70-80%)
• Linear distribution along duct = strong suspicion for DCIS
• MRI-guided vacuum-assisted biopsy is the standard for NME not visible on second-look ultrasound or mammography

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b. 40-year-old Woman with Unilateral Nipple Discharge - Imaging Workup

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