Neoplasm, Infection, Inflammation

Question 1

commonly used radiotracers

Answer 1

I-123 MIBG and I-111

Question 2

I-123 MIBG use, distribution

Answer 2

adults: pheochromocytoma
kids: neuroblastoma

also taken up by carcinoid, medullary thyroid carcinoma, paraganglioma

distribution: salivary glands, heart, thyroid (block with Lugol’s solution), liver, kidney, bladder

Question 3

I-111 production, half life, photopeaks

Answer 3

Indium-111 pentetreotide (Octreoscan)

cyclotron, decays by electron capture, emits 2 photons at 173 and 247 keV

half life 67 hours

Question 4

I-111 / Octreoscan

Answer 4

Indium 111 pentetreotide

analog of octreotide that detects tumors with somatostatin receptors

image carcinoid or islet cell tumors; can also image gastrinoma

glomus tumors of head/neck (extra-adrenal pheochromocytomas ) are also seen

distribution in kidneys, spleen, less so hepatic

Question 5

MIBG vs Octreotide

Answer 5

MIBG: adrenal pheochromocytoma (octreotide renal uptake may obscure adrenals)

extra-adrenal pheochromocytomas (MIBG vs pentetretodie are roughly equivalent)

Question 6

gallium 67 production, deay, half life

Answer 6

production: cyclotron
decay: electron capture
emission: 4 gamma peaks (93, 184, 296, 388 keV)
half life: 78 hrs

gallium binds to transferrin&raquo_space; found elevated in infection, inflammation, neoplasm

Question 7

Gallium distribution

Answer 7

high activity in bowel, colon; less in liver, skull, bone marrow, salivary glands

persistent renal activity < 24 hrs signifies renal disease

Question 8

pulmonary uptake with Ga-67

Answer 8

infectious/inflammatory

pneumocystis pneumonia, IPF, sarcoid, lymphangitic carcinomatosis, miliary TB, fungal infection

Question 9

panda sign

Answer 9

Ga67; Sjogren, lymphoma, AIDS, sarcoid

sarcoid if also with hilar/paratracheal adenopathy

increased in nasopharynx, parotids, lacrimal

Question 10

Ga 67 scan first line usage

Answer 10

spinal osteomyelitis

Question 11

Thallium 201 production, decay, half ilfe, distribution

Answer 11

production: cyclotron
decay: electron capture; low energy 69-81 keV xrays
half life: 73 hours

distribution: kidney, heart, liver, thyroid, bowel

Question 12

thallium 201 usage

Answer 12

Kaposi sarcoma, lymphoma, TB with gallium; not used frequently due to long half life/radiation

historically cardiac agent

Question 13

Indium 111 WBC distribution, imaging protocol

Answer 13

spleen > liver > bone marrow

imaged at 24 hours; no physiologic bowel uptake

Answer 14

I-111 WBC disadvantages/advantages

Question 15

disadvantage: tedius labelling procedure, higher radiation dose; less accurate for spinal osteomyelitis
advantages: absence of bowel/renal activity, delayed imaging, can perform simultaneous imaging (ie with abnormal bone scans)

Answer 15

Tc 99 HMPAO WBC advantages/disadvantages

Question 16

advantage: short half life, higher administration/counts, lower dose, arlier imaging (preferred in kids)
disadvantage: uptake in GI/GU tracts, limiting bowel activity; delayed imaging less practical

Answer 16

HCC and gallium 67

Question 17

increased focal gallium uptake&raquo_space; HCC

Answer 17

gallium/thallium imaging

Question 18

gallium/thallium imaging

Answer 18

Kaposi sarcoma: KaT (thalium avid), not gallium

TB: gallium avid (TuG)

Lyphoma: Thallium/gallium avid

Question 19

osteomyelitis

Answer 19

triple phase Tc99 MDP: positive > osteomyelitis

Ga67: increase specificity of positive bone scan (vertebral osteomyelitis/discitis)

I-111 WBC: evaluate infected orthopedic prostehsis

Question 20

WBC vs sulfur colloid in osteomyelitis

Answer 20

increased WBC, decreased sulfur colloid = marrow replacement consistent with WBC

normal marrow = uptake by both WBC/sulfur colloid

Question 21

extra-adrenal pheochromocytoma

Answer 21

1-123 MIBG or I-111 pentetreotide

F-18 FDG PET can also be used

Question 22

metastatic carcinoid/neuroendocrine tumor NM agent

Answer 22

I-111 pentetreotide/octreoscan