Nuclear Medicine Cases

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Hypertrophic osteoarthropathy

Primary: 3-5%, rare familial AD, pachydermoperiostosis
Secondary: associated with bronchogenic carcinoma, mesothelioma, Hodgkin’s

Features: periostitis in long bone
Precede clinical symptoms (bone pain, arthralgia), regress after treatment (scans normal 1-6 months after)

DDX diffuse periostitis

Hypertrophic osteoarthropathy
Thyroid acropachy (MC hands)
Venous stasis
Primary hyperparathyroidism
Hyperthyroidism
Reflex sympathetic dystrophy
Hypervitaminosis A
Flurorosis
Caffey's disease (exuberant hyperostosis)

Bone scan

Tc-MDP (methylene diphosphonate)
Increased activity seen with:
Increased osteoid formation (most important)
Increased blood flow to hyperemic areas
Interruption of sympathetic supply (RSD)

Critical organ: bladder (need hydration)
50% fixed to bone by 4 hrs, 70% renal excretion by 24 hrs
Dose 20-25 mCi

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Hodgkin’s lymphoma

Lymphoma: residual disease vs inactive fibrosis

Gallium-67: binds to iron transport proteins (transferrin, ferritin, lactoferritin), uptake by leukocytes
Normal uptake: liver (hottest), spleen, bone marrow

Dose 10 mCi (2x dose used for inflammation or infection)
Imaging at 48,72 hrs (6,24 hrs for abscess)
Critical organ: bowel

Collimator: medium-energy, parallel hole
Use laxatives to decrease bowel activity, image may be delayed 4 to 7 days

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Paget’s disease

Lytic, sclerotic and mixed phases: hot on all 3 phases
Features:
Cortical thickening, bony expansion
Bowing of tibia and femur (shepherd's crook deformity)
Early: thickening of iliopubic and ilioischial lines

Osteoporosis circumscripta:
Lytic phase
Frontal bone, outer table destroyed only

DDX:
Fibrous dysplasia
Chronic osteomyelitis
Primary bone tumors (osteosarcoma)

Malignant degeneration: MC osteosarcoma, fibrosarcoma

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Prostate cancer

Superscan: increased uptake relative to renal and soft tissue

DDX:
Metastases: breast, lung, prostate
Metabolic: renal osteodystrophy, osteomalacia, hyperparathyroidism
Myelofibrosis, systemic mastocytosis

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Plummer’s disease

Plummer’s disease: hyperthyroidism due to an autonomous hot nodule (ATN, usually hyperfunctioning adenoma) with suppression of the remaining gland

Less than 1% of hot nodules represent carcinoma
Increased T4/T3, low TSH from suppression

Diagnose with I-123:
Image 24 hrs (normal uptake 10-30%)
Treatment: Surgery or I-131 ablation (20-25 mCi)
Post-treatment, hypothyroidism uncommon since uptake preferential to hot nodule, little beta-radiation to rest of gland

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Cold thyroid nodule

Nonspecific:
75% of cold nodules are secondary to colloid cyst or adenoma, LC nodes, abscess, hematoma
Incidence for carcinoma is MC in cold nodules than hot nodules but still low (15-25%)

More likely to be benign:
Older female patients
Multiple nodules
Nodule decreases in size while on thyroid hormone
Ultrasound: differentiate solid from cystic lesion

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Pneumocystis carinii pneumonia

Gallium scan:
Bilateral and diffuse uptake without mediastinal involvement
More focal area of increased gallium uptake in LUL

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Toxic multinodular goiter

Case findings:
I-123 24 hour uptake = 53% (normal 10-30%)
Gland of normal size with multiple focal regions of increased activity in both thyroid lobes
Patient subsequently underwent I-131 therapy  recommended dosage is 20-70 mCi

Hyperfunctioning thyroid nodules are the 2nd MC cause of hyperthyroidism (MC Grave’s)

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Sacral insufficiency fracture

Honda sign on bone scan
Stress fracture:
Fatigue fracture: repeated stress on normal bone
Insufficiency fracture: normal stress is placed on abnormal bone (MC secondary to osteoporosis)

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Sacral insufficiency fracture

Honda sign on bone scan
Stress fracture:
Fatigue fracture: repeated stress on normal bone
Insufficiency fracture: normal stress is placed on abnormal bone (MC secondary to osteoporosis)

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Normal pressure hydrocephalus

Persistent ventricular activity
Delayed convexity flow


Normal CSF flow

Spinal (black arrows) and cisternal (white arrows) activity
Progressive flow over convexities at 24 and 48 hours

Abnormal CSF flow

NPH: persistence of ventricular uptake at 24 and 48 hours
CSF leak: activity outside neural axis
Asymmetry of flow in cisterns or around convexities

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Initial static images
2 days later

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Brain death

Case findings:
No blood flow to supratentorial or infratentorial brain
Absent sinuses
Absent ICA flow (hot nose sign)

Hot nose sign:
Nasopharynx uptake: suggests ECA circulation from impeded ICA flow
NOT pathognomonic for brain death

Brain death: absent cerebral flow despite maintained cardiac and respiratory function
Static images after flow show whether tracer is taken up by the cortex

Blood flow agents:
99mTc pertechnetate, 99mTc DTPA, 99mTc glucoheptonate
Need to show presence of flow above the skull base in arterial phase, AND activity in sinuses (especially superior sagittal sinus and transverse sinus) on delayed venous phase
DTPA: no salivary uptake

Cross blood-brain barrier and accumulate in the brain:
99mTc HMPAO, 99mTc ECD
Flow study NOT required
HMPAO: shows salivary uptake, preferred agent (obtain dynamic and static images)

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Alzheimer’s disease

Decreased perfusion and FDG uptake in bilateral parietal and posterior temporal lobes
Sparing of sensorimotor cortex, BG, and thalami, which appear more pronounced

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Cross cerebellar diaschisis

Case findings:
Large perfusion defect in left MCA territory
Reduced relative uptake in right cerebellar hemisphere

Crossed-cerebellar diaschisis:
Seen on PET and SPECT
Contralateral cerebellum shows decreased uptake
Due to loss of afferent stimuli, may have accompanying cerebellar symptoms that are reversible

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Myositis ossificans

Case findings:
Soft tissue heterotopic bone formation

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Reflex sympathetic dystrophy (Sudeck's atrophy)

Case findings:
Increased periarticular uptake on bone scan

XR: generalized regional osteopenia with periarticular osteoporosis, with preservation of joint spaces

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Colloid shift in cirrhosis

Splenomegaly, nodular liver
Increased uptake in bone marrow  colloid shift
Secondary to decreased colloid sequestration by the liver due to depletion of reticuloendothelial cells from scarring

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Meckel’s diverticulum

Tracer: 99mTc pertechnetate (taken up and secreted by gastric mucosa)
Abnormal uptake should occur at the same time as gastric uptake

Enhance sensitivity with:
Pentagastrin: increase rapidity, duration, and intensity of uptake
Glucagon: decrease peristalsis
Cimetidine: histamine antagonist, inhibits secretion of pertechnetate from gastric mucosa

Complication:
Bleeding: acid and pepsin secretion by gastric mucosa produces ulceration of adjacent bowel mucosa

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Gastric emptying study

Case findings:
Delayed gastric emptying status post Billroth II surgery

Tracer:
99mTc sulfur colloid
111-In DTPA can alternatively be used in liquids
Indications: diabetic gastroparesis, children with GE reflux
Solid meals better at detecting mild to moderate delay in gastric emptying

Solid emptying: initial lag (time for antrum to grind up food particles) followed by linear emptying, T1/2 = 1 to 2 hours
Liquid emptying: exponential pattern, T1/2 = 30 minutes

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Choledochal cyst

Type 1: MC, fusiform dilatation of CBD
Type 2: diverticulum of CBD
Type 3: dilatation of intraduodenal portion of CBD (choledochocele)

Type IV:
Type IV-a: intrahepatic and extrahepatic ductal dilatation
Type IV-b: extrahepatic ductal dilatation

Type V: Caroli’s disease (MC intrahepatic ductal dilatation)

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Inflammatory bowel disease

Abnormal accumulation of leukocytes in colon
Most likely ulcerative colitis or pseudomembranous colitis

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Parathyroid adenoma

Case findings:
Increased uptake on 99mTc-sestamibi images in the left inferior parathyroid gland
Best appreciated on subtraction images of the 99mTc-sestamibi and 99mTc-pertechnetate

Uptake by thyroid and parathyroid:
Th-201, sestamibi
Uptake ONLY by thyroid:
Pertechnetate, iodine-123
Thalium-201 and 99mTc-pertechnetate subtraction
Thyroid and parathyroid tissue take up Thalium-201
99mTc-pertechnetate is taken up only by thyroid tissue
99mTc-sestamibi and Iodine-123 subtraction
Sestamibi is taken up by both
Iodine is taken up only by thyroid tissue
99mTc-sestamibi and 99mTc-pertechnetate subtraction
Technique used in this case

Only 99mTc-sestamibi (with early and delayed images)
Both thyroid and parathyroid tissue take up sestamibi
Thyroid tissue will wash out the radiotracer, whereas a parathyroid adenoma will retain it on delayed images

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Captopril renography

Tracer: DTPA or MAG3 in combination with Captopril
DTPA:
Decreased excretion with delayed appearance of tracer
Measure of GFR
MAG3:
Prolonged retention of tracer
Renally secreted (hippuran analogue)

Renal perfusion is disproportionately reduced in a kidney with renal artery stenosis when Captopril is used compared with a standard renal scintigram
Captopril: ACE inhibitor, block formation of angiotensin II  thus decreasing renal efferent arteriolar pressure and function of the affected kidney

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Graves’ thyroiditis (early)

Case findings:
24 hours after I-123:
Diffuse increased uptake of radionuclide throughout thyroid
No discrete hot or cold nodules are identified
I-123 uptake 38% (normal 10-35%)

Increased uptake with subnormal TSH and normal fT4 and fT3  early Graves' thyroiditis

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Sarcoidosis

Case findings:
Bilateral hilar uptake of FDG

DDX of PET FDG findings:
Lymphoma

FDG PET

Benign lesions (infectious and inflammatory processes) with false-positive findings

Chronic thyroidosis
Warthin’s tumor of the parotid
Chronic sinusitis

Chest:
Sarcoidosis
Active tuberculosis, granuloma
Thymoma, pneumonia, abscess

LC lesions:
Thymic hyperplasia
Aspergillosis, histoplasmosis
Rheumatoid disease, alveolitis
Radiation pneumonitis