New Page 1

Quality Control

RADIOPHARMACEUTICALS
Mo breakthru & Al+ ion breakthru must be checked at EVERY elution

1. Radionuclide Purity - amount of activity present due to nuclide of choice
Mo Breakthrough Test - differential absorbtion from Tc-99m
sample sheilded w 3mm lead, only 452keV Mo pass
.15uCi Mo per 1mCi Tc-99, 1:1000 allowable

2. Radiochemical Purity - precise account of Tc compounds
Free pertechnetate & hydrolyzed reduced Tc dec image quality
hydrolyzed if exposed to air
monitored by paper & gel chromatography, <2% resonable
NOT neccessary for it to be "Carrier Free" (free of stable isotope)
Tc activity out of generator 150mCi/ml
adjust by decreasing amt of saline infused

3. Chemical Purity - Chemicals from elution process dec image q
Al+ ion breakthrough test - tested colormetrically
sample drop on test paper compared to standard w 10ppm of AL+
if sample is redder than the standard then test fails
Al+ will inc lung or liver activity due to clumping w sulfur colloid

4. Pyrogen Testing - testing for endotoxin etc
USP XX Test - injected into rabbits & temp monitored
Limulus Amoebocyte Lysate Test - 10X more sensitive for G-

5. Misadministration - wrong med, wrong pt, wrong route or wrong dosage
Diagnostic dose must be within 50% of prescribed dose
Theraputic dose within 20%
Report to NRC if pt recieves 5rad whole body or 50rad to an organ

6. Ideal Radiopharmaceutical - pure gamma, 100-250keV
T1/2eff = 1.5x the length of the test
high target to background ratio - at least 5:1, 25:1 ideal, SPECT 2:1
All injected pharmaceuticals must be sterile, isotonic & calibrated

CALIBRATORS
Ionization Chamber quality control
Chamber contains argon gas - a question by Dr. Guiberteau at orals

1. Constancy - Daily test for precision w Co-57 & Cs-137 sample
must be the same on all settings day to day, +/- 5%

2. Linearity - Quarterly test done w high activity Tc-99m sample
50-300mCi source measured q4hrs for up to 48hrs
matched to calculated decay curve, +/- 5%

3. Accuracy - Anual test of 3 different source standards, +/- 5%

4. Geometry - check activity does not change w location in chamber
done by manufacturer & at times of repair, +/- 5%

SCINTILLATION CAMERA QC
10 dinodes in each Photomultiplier tube
each generates 4 electrons for each one recieved, amplifies x 1million
Pulse Height Analyzer - removes all but desired peak
Ideal Energy - 100-250keV

1. Field Uniformity - Daily, variability of counts w homogeneous flux
Intergral Uniformity - maximum deviation
Differential Uniformity - max rate of change over 5 pixels
Causes - High kilovoltage drift of photomultiplier tubes
collimator damage & contamination
Improper photopeak setting
Intrinsic Field Uniformity Test - done w/o collimator
point source of Tc-99 w 200mCi placed 5 diameters away
aquire 1-2million counts & register results
Extrinsic Field Uniformity Test - Done w collimator
Sheet source w 2-10mCi placed on collimator
Compare corrected & uncorrected images & note aquisition time

2. Spatial Resolution and Linearity - weekly, ability to localize a gamma ray in X,Y
Intrinsic Spatial Linearity - defines positional distortion
Tested w lead phantom attached to front of crystal
point source of 1-3mCi placed at 5 crystal diameters away
1-2million counts then aquired, depends on size of crystal

3. Peak Energy Correction - monthly evaluation of Pulse Height Analyzer
Tc-99 source placed 5 crystal dia away, should be +/- 20% from 140keV

Off Peak Images - wrong setting or circuitry problem
Setting too Low for pharmaceutical - PM tubes light up in honeycomb pattern
Setting too High - PM tubes form photopenic regions in field

4. Full-Width Half-Maximum Value - measure of resolution, NOT sensitivity
the range of energy at 1/2 the max energy divided by the max energy x 100%

SPECT QUALITY CONTROL
keep all parameters & settings same as w pt study

1. Field Uniformity - weekly test w 64x64 word matrix flood
Co-57 sheet source also - <1% uniformity variance

2. Center of Rotation - Tc-99 source placed 5cm from center

LOGBOOKS
Many but only 3 are important

1. Area Room Monitoring Logbook - Daily map of relative activities
if an area is 10-20x above background cleanup done, then relogged

2. Incoming Package Logbook - all info on each radioisotope arrival
done at the time of arrival

3. Dose Calibrator QC Test Logbook - done as each test performed

Radiopharmaceuticals

TECHNETIUM 99m
accounts for over 70% of radionuclide use in US
Ideal - minimum particle emission, photopeak between 5-500keV
reactive w many chemicals, low toxicity, stable

Production - separated from Mo-99 in generator sys, Al column
washed off column as sodium pertechnetate, anion w one charge
column reaches 50% activity at 6hrs, 100% at 23hrs
convienent to "milk" the elution daily

Decay - Gamma Decay, most easily detected & least ionizing ray
follows intial decay events simultaneously in most cases
Isomeric Transtion - dec nuc E w/o change in N-P ratio
Mo99 decays by Beta-Gamma emmision to Tc99m
radionucliotides in this state are "metastable"
tissue damaging B particles emitted during elution
Gamma produced when Tc99m completes decent to stable
Internal Conversion - photon absorbed within same atom
if sufficient E the e- is ejected (internal conversion e-)
KE = difference between E of gamma & binding E of e-
characteristic X-ray follows, incidental & not useful

Energy Level - 140keV (98%) gamma photon
t1/2 - 6hrs

Dose - 10mCi, critical organ colon receives 1-2rad/10mCi
Safe for fetus, only .5rads w any dose type, keep hydrated, bone worst

Uptake - pertechnatate loosely bound to protein
50% leaves plasma in minutes - salivary, choroid, Gastric, breast & thyroid
PreTx w Stannous Chloride reduces pertechnetate, binds to RBC

Excretion - by GI & glomerular filtration w partial tubular resorb
30% eliminated in urine in 24hrs

IODINE 123

Production - cyclotron bombardment, or allow Xe-123 to decay
contaminated w 5% I-124 if from Te-122, .5% from Xe-123
I-125 contamination increases w elapsed time
agent of choice but expensive & difficult to distribute

Decay - e- capture, unstable proton captures e- to turn to neutron
k shell e- taken w fixed portion of E taken away as neutrino
l shell e- drops in producing characteristic X-ray
Auger e- occasionally produced instead of X-ray
E from inward migrating e- ejects outer shell e-
also called internal photoelectric effect
predominates when Z less than 30

Energy Level - 28keV (92%), 159keV (84%) X-rays
t1/2 - 13.3hrs, decay by e- capture

Dose - 200-400uCi orally, whole body dose .04mrad/uCi
thyroid dose 7.5mrad/uCi, usually 3-6rads total
higher thyroid dose than I-131 but lower whole body

Uptake - trapped & organified by thyroid, stomach & salivary
GI tract 10%, distributes to extracellular space

Excretion - 75% by renal in 24hrs, GI also

IODINE 131
Too energetic for Gamma camera but cheap & availabe
high E does allow for theraputic uses

Production - fission decay

Decay - B- emission to stable Xe-131
Negative Beta Decay, neutron changed to proton
e- & neutrino emitted, Z number increases by one
E of Beta particle varies from 0-max transition E
average E must be determined experimentally
Gamma emitted due to residual nuclear Energy

Energy Level - principle 364keV (82%) gamma, 192keV (92%) Beta
t1/2 - 8 days

Dose - 30-50uCi, whole body dose .6mrad/uCi, 90% beta, 10% gamma
Critical organ is thyroid 1rad/uCi

Excretion - identical to I-123, 75% renal in 24hrs, GI also

XENON 133
used almost exclusively for Ventalation scanning

Production - fission product of U-235

Decay - B- emmision to stable Cs-133
Negative Beta Decay, neutron changed to proton
e- & neutrino emitted, Z number increases by one
E of Beta particle varies from 0-max transition E
average E must be determined experimentally
Gamma emitted due to residual nuclear Energy

Energy Level - 82keV gamma photon, 31keV X-ray & beta component
t1/2 - 5.2day physical & 30sec biologic

Dose - 15mCi via closed circuit ventilator
Critical Organ - beta component causes 1 rad to lung

Uptake - highly soluble in oil, even soaks into plastic syringes

INDIUM 111
better than Ga for infection, NO GI or urinary activity
Oncoscint - new Ab-Ag complex for colorectal & ovarian Ca
Octreotide - goes to somatostatin receptors

Production - Cyclotron bombardment of Cadmium-112
harvested WBC chelate of DTPA, take up induim over 2hrs

Decay - e- capture to stable Cadmium-111

Energy Levels - 173keV (89%), 247keV (94%) X-ray photons
Detected with dual pulse height analyzer,

t1/2 - 67hrs, distributes to spleen, liver, marrow in 6-7hrs
I-111 chelated w DTPA has longer, intercranial cisternography

Dose - .5mCi, spleen critical organ w 13-18rads/mCi
all other organs lower than Ga-67

THALLIUM 201 CHLORIDE
must avoid caffeine before any thallium test

Production - Cyclotron bombards thallium producing Lead-201
this is allowed to decay to Tl-201

Decay - e- capture to Hg201 which is actual X-ray source

Energy Levels - 71keV (98%) X-rays, 167keV (10%) gamma photons
Quality Control - <.25% Pb-203 & <.5% Tl-202 (439keV)

t1/2 - physical 73hrs, biologic 10days, leaves blood in 30sec

Uptake - Potassium analog, rapidly distributes thru body esp muscle
uses Na+/K+ pump

Dose - 1.2-3mCi, larger for SPECT
whole body .5rad, critical organ kidney 3rad

Excretion - mostly urinary, <10% cleared in 24hrs
washes out slowly from muscle, rate dependent on blood flow
much slower from ischemic areas

GALLIUM-67 CITRATE
bone scan w eyes & a liver

Production - zinc targets bombarded w protons from cyclotron

Decay - e- capture to ground state of Zn-67

Energy Levels - 93keV (38%), 184keV (24%), 300keV (8%) useful
several other unused E levels as well

t1/2 - Physical 78hrs, Biologic 2-3wks

Dose - 3-6mCi or 50uCi per Kg
Whole body .3rads/mCi
Critical organ - colon .9rads/mCi

Uptake - bound to iron binding sites of proteins, ferric ion analog
Plasma transferrin #1, albumin & globulins also in blood
enters interstitial spaces & binds lactoferrine in tissue
PMN's bind 10% of dose due to high cytoplasmic lactoferin levels
even nonviable at sites of inflam, lympho's & macros
Also accumulates in bacteria themselves
Activity most intense in RES at 24hrs, liver, spleen, marrow
kidney's, colon, salivary, lacrimal, blood pool (20%)
will accumulate in the epiphyses of children
72hrs - liver, bone, nasal; kidney no longer visible

Excretion of Ga-67 - 20% via GI & colonic mucosa; use enemas
first 24hrs excretion is renal, 25% of activity eliminated
after 48hrs renal activity N, all elimination via colon
Various body fluids including milk, no nursing for 2wks

Normal Variants - Breasts change w cycle & menarche
Liver - suppresed by chemo, high Fe levels, Dz & radiation
Lung - inc uptake P lymphangiography
Children - uptake in thymus & epiphysis

Imaging Times - 6, 24, 48 & 72hrs
in general optimal target-to-background ratio at 72hrs
6-24hrs for abcess, 24-48 for tumor
lesions <2cm in diameter on NOT detectable
Indications for Gallium Scanning
Infection - Ga replaced by WBC imaging, still good in chronic
Crohns Dz, inflamed & infarcted bowel
for lung sacrcoid, interstial fibrosis, TB, PCP

Tumor - variable but good for Hodgkins & Non-Hodgkin's
Good for DDx of cold liver lesions on sulfur colloid scan
Useful for F/U in tumors that have demonstrated uptake intitially
>50% sensitivity for I' melenoma & met sites
Not useful for head & neck or GI tumors

Bone - 90% more sensitve than Tc-99 MDP for osteomyelitis
sarcoma, cellulitis & pagets
Post orthopedic surg 3 phase bone scan always pos
Ga-67 100% sensitive for osteomyelitis but 25% specific
If neg scan though osteomylitis is ruled out

Lung - obtain at 48hrs, 50% of N have activity at 24hrs
>90% sensitivity for I' pulm malig, not specific
for lung sacrcoid, interstial fibrosis, TB, PCP
sarcoid & inflam lesions have > uptake than Ca

Renal Imaging - abn uptake on images delayed 48-72hrs
tumor, pyelonephritis, collagen-vasc Dz
transplant assesment for acute or chronic reject, ATN

Summary of Energy Isotopes

ISOTOPES
Tc-99 140keV 6hr Isomeric Transition
I-123 159keV 13.3hr e- capture
I-131 364keV 8d B- decay
Xe-133 82keV 5.2d B- decay
In-111 247 & 173keV 67hr e- capture
Tl-201 71 & 167keV 73hr e- capture
Ga-67 93, 184 & 300keV 78hr e- capture

Tc-99m AGENTS, DOSES & CRITICAL ORGANS
MDP 20mCi Bladder 2rads
HIDA 3mCi Colon 6rads
SC 3mCi Liver 1rad
Ceretec 25mCi Lacrimal
DTPA 20mCi Bladder .5rads
MAG3 10mCi Bladder
DMSA 5mCi Kidney 15rads
Cysto .5mCi Bladder 50mrem
Sestamibi 7-22mCi Colon?
MAA 4mCi Lung 1.5rad

Agents for Inflammation

1. Ga-67 Citrate - hyperemia allow leakage into extracellular spa
preferentially binds nonviable PMN's & macrophage
only used for Chronic abcesses now

2. In-111 Labeled WBC - 80% sensitve, 97% specific
NO GI or urinary activity
chelated w DTPA then placed w harvested WBC, takes 24hrs
Dose - .5mCi, spleen critical organ w 13-18rads/mCi, highest in kids
all other organs lower than Ga-67
t1/2 - 67hrs, distributes to spleen, liver, marrow in 6-7hrs
Imaging Times - 18-24hrs w optional 6hr in inflam bowel Dz

Indications - occult sepsis, pyogenic infection, abcess
Vascular Graft - N uptake for 2-3mo
Focal activity >spleen typical for abcess
Activity equal to liver typical for sig inflam process
Crohn's, UC, ischemic bowel, GI abscess
Liver Abscess - always combine sulfur colloid & Ga-67 or In-111
Splenic Infarct - matching cold defects w both In-111 & colloid
abscess will have inc uptake of In-111

Pitfalls - CHF, Embolized Cells & any cause of compliment activation
GI hem, postradiation, ALL, cerebral infarct, hematoma
Splenic abcess can be obscured, accesory spleen can decieve
Surgical wounds less than 10 days old, but better than Ga-67
Swallowed leuckocytes from sinusitis or pneumonia
Osteomyelitis - especially verterbral and chronic may be COLD

3. Tc-99 Labeled WBC - better for osteomylitis in extremities
Production - WBC's do not have to be seperated from plasma
Ceretec passes thru cell membrane then binds to mitochondria
Imaging - 30min & 90min usually give complete exam
bowel should not be seen before 4hrs unless inflammed
renal & bladder activity usually seen by 1hr
advantage over Indium is better photon flux & faster images
In-111 still better for chronic process w slow WBC exchange

Bone Scintigraphy

BONE AGENTS

Cortical Bone Agents - produced by Tc-99 chelation into tin-phosphate
Polyphosphates - first described, up to 46 phos residues
simplest is pyrophosphate PYP
Diphosphonates - Organic analogs of PYP, P-C-P bonds, stable
EHDP - ethylene hydroxydiphosphonate
** MDP - methylene diphosphonate
IDP - Imidodiphosphonates, characterized by P-N-P bonds
labeling effeciency >95% for use, check w chromotography
50% goes to bone of adults, 75% in children
Dose - 20mCi, .01rad/mCi whole body
critical oragan bladder .13rad/mCi
Uptake - rapid dist to ECF, chemisorbs to hydroxyapatite crys
58% efficacy for MDP in 3hrs
3 primary determinates for phosphate uptake:
1) Skeletal Metabolic Activity - most important, osteoblastic lesions
2) Blood Flow - a 3X inc in blood flow causes 30% inc in uptake
3) Sympathetic Tone - loss causes capillaries to remain dilated
Tag Breakdown - Free pertech will localize to GI, Salivary & thyroid
Excretion - Normally 50% of injected dose excreted by kidneys
Clarity of scan lost w renal failure, high ST background
kidneys often not visualized P 4hrs or w "superscan"
Imaging - 2hrs post injection, fx uptake may delay 3-10d
Hydration reduces background, void before imageing
Three Phase Scan - 90% sensitivty & specifictiy for Osteomyelitis
1) rapid sequenc frames, 10 at 5sec each
2) immediate postflow - 1mil counts
3) 4hr delay 1mil counts, 24hr F/U adds to specificity
Specificity dec in child & elderly, may be cold esp early in child
probably due to pressure compromixing blood flow

Bone Marrow Agents - asses hematopoesis & RES uptake
Tc-99 MMAA - micro-microaggregate albumin, liver & spleen also
10mCi of 30-100 micron size particles
6X higher accumulation than sulfur colloid at 1hr
detects hematopoetic expansion beyond & in bone marrow
also detects marrow replacement dz, avasc nec & infarct
Tc-99 Sulfur Colloid - 10% uptake by marrow, smaller particles than MMAA
In-111 Chloride - iron analog taken up by erythrocytes, also used

BONE LESIONS
Photopenic Bone Lesion
Disruption of N blood flow - early osteomyelits, trauma
radiation, sickle crisis, thrombosis
Replacement of Bone by Destructive Lesion - mets or primary
AVN - loss of fem head uptake relative to contralat side
Uptake should be seen in 100% of N 10-20y/o, 40% of 70y/o
Legg-Perthes - 95% specefic & sensitive, better than plain film
Osteoid Osteoma - "Double Density" sign, hot nidus w periph penia
helpful post-op to ensure that nidus was removed
Hemangioma - mostly in vert body, slight dec or inc uptake
vertical striations on plain film

Long Segmental Diaphyseal Uptake
Bilat & Symetric - hypertrophic pulmonary osteoarthropathy
Shin splints, Engelmann Dz (progressive diaphyseal dys)
Unilat - arterial injection, venous stasis, osteomyelitis
fibrous dysplasia, osteoid osteoma, trauma
Pagets - often asym, entire long bone & pelvis freq
very rare to have sim appearance to mets, check plain film
malig degen to osteosarc or giant cell in 10%

Benign Bone Lesions
NO Tracer Uptake - NOF, Osteopoikilosis, Bone Island
healing NOF may have inc uptake
Increased Uptake - Fibrous Dysplasia, EG, Enchondroma, ABC
Chondroblastoma & brown tumor also
Usually no inc on dynamic flow or immediate blood pool
Osteoid Osteoma, Hemangioma & Fx thru benign lesion do though
Sudec's Atrophy - Reflex Sympathetic Dystrophy, see bone file
Nucs - shows inc flow & but dec uptake, plain film shows osteopenia P 6wks
Trauma is often intial event, severity does not influence outcome

Malignant Bone Lesions - most are mets, seen up to 18mo before X-ray
80% axial, 10% skull, 10% long bones
15% of solitary lesions are malig in pt w known primary
less likely to be met though
location effects probability whether a lesion is malig
Renal Cell (bubbly & lytic), prostate, breast, lung, thyroid, neuroblastoma
"Flare Phenomenen" - inc activity in met which is clinically responding
inc blood due to inflam response of healing, peaks at 3mo, resolve by 6mo
also see an earlier peak in alk phos levels, plain films not affected
80% of focal cold lesions are mets, mult scans often not needed
further lesions & specific location w plain film, esp if pregnant
Osteogenic Sarcoma mets to lung etc often take up diphosphonate
Superscan - absent kidney sign, inc bone to soft-tissue ratio
Metabolic - often involve calvaria & long bones, Mets spare them
Hyperparathyroidism - brown tumors can have inc or dec uptake
II' from renal osteodystrophy more likely to cause uptake
50% of I' hyperparathyroidism has abn uptake
Hyperthyroidism - resorbtion > formation, freq fx's
Widespread Bone Dz - diffuse skeletal mets #1, pagets
myelofibrosis, aplastic anemia, waldenstrom macroglobulin
Activity inc esp in metaphysis & periarticular
Most common cause is factitious, delay of 4hrs or more

Fractures - uptake from inc osteoblastic activity, DDx from tumor
Acute Phase - 3-4wks, 80% abn at 24hrs, 95% abn at 72hrs
elderly delayed, children positive in <24hrs
Subacute Phase - 2-3mo, time of most intense uptake along Fx
Chronic Phase - 1-2yrs, slow decline in uptake, 65% N in 1yr
Rib Fx return most rapidly, complicated Fx at stress long
Compression Fx - use pinhole collimator for 500,000 counts at 10cm
the view gives mag & inc spatial resolution, DDx from met & infec
Stress Fx - focal area of inc uptake, more sensitive than radiograph

Shin Splints - abn stress of soleus musc at it's tibial origin
uptake increased along the length of the posterior 1/3 of both tibia

Osteomyelitis - 3 phase Tc-99m MDP gold standard, shows delayed bone activity
tagged WBC more specific, In-111 or Tc-99, shows site of WBC migration
tend to have false neg if being treated
Ga-67 more sensitive, goes to area of inc metabolism in bone
may be better for chronic, tends to dec activity w healing
MDP may also appear as a COLD defect in early imaging, esp w young

Prosthesis - can have inc activity up to 1yr w cemented & 2yr w cementless
Loosening - usually low level uptake or discreet area adjacent to prosthesis
Infection - marked inc uptake more diffuesely distributed
Ga-67 or tagged WBC differentiate if a recently placed prosthesis infected

Post Radiation - Sclerosis & osseous necrosis develop within 2-3mo
Arteritis assoc which correlates w decreased uptake of radiotracer

Pitfalls - normal increased uptake in patella, thyroid cartilage & deltoid tuberosity
uptake can also be seen in an axillary node on the side of injection
Free Pertechnatate - activity in salivary, thyroid & gastric
Always consider urine contamination

SOFT TISSUE UPTAKE IN BONE SCAN
physiologic in breast, kidney & bowel
Free pertechnetate will inc saliva, thyroid, stomach activity
Excess Tc colloid will inc liver, due to Al ions in eluate
Tumor - osteosarcoma, neuroblastoma, meningioma, mets
Inflammation - abcess, myositis ossificans, pericarditis
delays of 4 & 24hrs show washout to DDx from osteomyelitis
Trauma - healing wounds, subdural, ischemic bowel, IV sites
Rhabdomyolysis - musc injury P seizures, IM injection, pressure nec etc
extreme form can lead to actue tubular necrosis
Heterotopic Ossification - occurs 4-10wks P injury
Metabolic - hypercalcemia in stomach, lung, ie hyperparathyroidism etc
Dystrophic Soft tissue calc - necrosis or amyloid deposits
Lungs - Hyperparathyroid, elev vit D, fibrothroax, sarcodosis
uptake can be seen in lung ca w/o gross calc or bone invasion
Malignant Plueral effusion - inc uptake in assoc side
Abdomen - diffuse inc uptake w peritoneal Dz or studding

Incidental Urinary Tract Abnormalities
Bilat Inc - hypercalcemia, tissue damage from chemo, Ca, inf
iron overload from sickle cell or thalassemia
can get diffuse inc due to damage from chemo etc
Bilat Dec - end stage renal Dz or superscan
Focal Dec - abscess, cyst, met, scar
Focal Inc - N in upper calyces, urinoma or ileal conduit
Acute Renal Failure - bilat uptake usually seen, but poor clearance
this causes diffuse inc soft tissue activity & poor bone discrimination

Brain Scintigraphy

BRAIN SCINTIGRAPHY - RADIONUCLIDE ANGIOGRAPHY

Agents for Brain Perfusion
Tc-99m HMPAO (Ceretec) - lipophilic, crosses blood-brain barrier
Distribution proportional to blood flow, NO redistribution
80% taken up by brain in 1st pass, equilibrium in 5min
Acute infarct evident within 1hr, before CT or MRI
Sensitive for seizure foci if injected during seizure
PITFALL - must be injected within 30min of preperation
breaks down to a hydrophilic form, uptake will be seen in parotid
I-123 Iodoamphetamine - dist proportional to blood flow like ceretec
Cb & basal ganglia brighter due to inc flow
homogeneous distribution in gray matter, will redistribute
Tc-99m Pertechnatate - good for assesment of angiographic pattern
active transport into choroid plexus in addition to the salivary etc
Tc-99m DTPA - Blood Brain Barrier scan, only crosses if broken down
can be used for neoplasm or stroke

Stroke - area of dec activity w agents that cross BBB
inc uptake w agents that don't cross BBB such as Tc-99m DTPA
Luxury Perfusion - can cause inc w all agents
DDx from tumor by vascular distribution

Arterial Stenosis - limited value, 50% sensitivity to 80% occ
"Flip-flop" sign - initial low activity on involved side
late arterial phase shows inverse due to slow coll filling
Luxury Perfusion can show inc activity on involved side initially
Static images often N early, diminished or flame-shaped P 7-10d

Cerebral Death - inc ICP results in dec cerebral flow, thrombos
Carotid arteries must be visualized to confirm good bolus
activity stops abruptly at skull base, NO sagital sinus
arteries of skull & face seen, "hot nose" sign
Rules out barbituate intoxication which can fool EEG

Scalp Lesion - can be cause of false positive findings
always do physical exam
Agents for Brain Lesions
Tc-99m Glucoheptonate - 15-20mCi, obtain q2min flow images
enter brain only if BBB breakdown, CVA seen P 1wk
then 4 & 24 hr delays w 1mil counts each
higher target to background than Tc-99 DTPA
Tl-201 - best predictor of tumor burden
uptake proportional to growth rate, >1.5 times N assoc w high-grade
good for DDx of necrotic tissue post-rad from reccurance
nonspecific for tumor type

Brain Tumor - close correlation to inc perfusion & enlarged vessels
Meningioma inc activity in 80%
Mets - inc activity in 20%, esp if vasc mets
thyroid, renal cell, melenoma, anaplastic lung & breast
tend to have slow uptake but very bright by 2-3hrs
Gliomas may cross the midline, very rare for benign lesion

Seizures - abn flow images within 1wk of event even w/o lesion
35% due to tumors, if >50 vasc Dz more common, trauma, inflam
Transient hyperperfusion of involved hemisphere

Radionucleotide Cisternography

Thyroid and Parathyroid Scintigraphy

THYROID AGENTS
Do not use past 10th week of gestation

I-123 - agent of choice for thyroid imaging
200-400uCi oral, give 24hrs prior to imaging, 7.5mrads/uCi
2-3rad total dose to thyroid, less than I-131to whole body
Iodine readily absorbed from GI, distributes to extracellular
Thyroid traps & organifies, trapped by stomach & saliva
75% renal excretion in 24hrs, GI also
Cyclotron produced & Expensive, less available than I-131

I-131 - 30-50uCi dose, 1.5rad/uCi, 50rad to thyroid, 90% beta
Used for uptake studies & treatment of hyperthyroid or Ca
364keV gamma & 192keV beta too energetic for gamma camera
rectilinear scanner better with limited resolution
Dose to high for routine diagnostics

Tc-99m Pertechnetate - 5-10mCi dose, 100-300mrad/mCi (lowest dose)
Assessment of trapping fxn, Maximum uptake at 20min (.5-3.7%)
NO organification, completely discharged by K+ perchlorate
Target to background less favorable than iodine
Better photon flux - detectablility of nodule <8mm improved
Image w 5mm pinhole for mag, organ takes up 2/3 of view
200-500,000 counts acquired 5min P dose, include markers
Results in <2hrs, good if pt unable to take PO meds
Also good if Pt has had Iodine dose, ie contrast
Discordant Nodule - 2% of Tc-99 hot nodules will be cold w iodine
nodule cannot be considered functioning until confirmed w Iodine

Iodine Fluorescene Imaging - 15mrad dose but need special equip
beam of 60keV photons from Am-241 source fired at thyroid
K-characteristic X-rays produced at 28.5keV
Good if iodine pool flooded, measures total Iodine content
Thyroid Uptake Measurement - for Dx of Graves Dz & Thyroiditis
% uptake = (Neck counts - thigh counts)/(counts in administered dose) in CPM
actual mCi taken up = (% uptake) x (mCi given)
Best w 200uCi I-123 or 10uCi I-131 uptake only, 50uCi for image & uptake
Tc-99m requires calibration
N 5-15% at 4hrs, 10-30% at 24hrs
Inc w Graves, dec w subacute thyroiditis
not for Dx of hyperthyoidism, may turn over by 24hrs
Neonates have marked inc uptake in 1st 2 wks
don't underestimate dose to gland

Suppression Scan - defines autonomy of a hot nodule
if nodule suppresed by T3/T4 than autonomy does NOT exist
activity should drop 50% from baseline

Stimulation Scan - demonstrates thyroid tiss supp by hot nod
TSH documents functioning tyroid tiss, rarely done

Perchlorate Washout Test - demonstrates organification defect
N Thyroid binds Iodine to Tyrosine after uptake (organification)
Once bound Iodine cannot be washed out by Perchlorate
Hashimoto Thyroiditis & Peroxidase defeciency prevents binding
If not organified activity will dec by >15% P perchlorate
TSH continues to encourage uptake due to low T4
hyperactive uptake freq seen

NORMAL THYROID ANATOMY
Thyroid begins functioning at 3rd month of gest
N thyroid 25g (1g per cubic cm), upper limit size 4 x 2 x 2cm

Pyramidal Lobe - present in 10%, thyroglosal duct rem
downgrowth from foramen cecum of tounge
Also prominent in Grave's Dz & Hashimoto's Thyroiditis

Lingual Thyroid - incomplete decent, like thyroglossal duct cyst
causes hypothyroidism in infants, give replacement quickly
may present as lump in tounge
Don't resect until N thyroid confirmed in neck
Thyroglossal duct cyst will not take up iodine

THYROID PATHOLOGY
Goiter is a generic term meaning enlaragement of the thyroid
Nodules - most are cold, 25% malig if solitary, less if multiple

Mutinodular Goiter - most due to iodine deficiency induced hyperplasia
functioning nodules formed which then hemorrhage
the nodules then filled in w nonfunctioning colloid
heterogenous uptake & overall enlargement eventually develop
a dominant nonfunctioning nodule should never be ignored though
Iodine Deficiency Goiter unusual in USA, low serum T4, high uptake
occurs II' to chronic TSH stimulation
multiple nodules much more likely to be benign than solitary

Adenomatous Goiter - also a multinodular goiter, 3:1 female
Develops in 4th decade, often present up to 20yrs before hyperthyroid
NUCS - mult hot nodules w some cold suppressed nodules poss
US - shows mult 1-4cm hyperechoic nodules, asym gland
areas of hem, nec & coarse calc poss
Toxic Nodular Goiter - Plummer's Dz, autonomous fxn of a thyroid adenoma
high T4, low TSH, must be 2-3cm to cause hyperthyroidism
Hot nodule w suppression of remainder of gland
suppressed tissue can be recruited if TSH given or levels elevated by Tx
80% higher uptake in 24hrs than N
Tx - tissue is more resistant to treatment than in Graves
25-29mCi I-131, extranodular tissue spared due to suppresion by nodule
DO NOT Tx w I-131 if pt is on anti-thyroid medication, propylthyouracil
scan to assure that only nodule is functioning
otherwise subsequent hypothyroidism rises from near zero to 30%

Graves Disease - Diffuse Toxic Goiter, 5:1 female
Autoimmune, Ab bind to TSH receptors, cause hyperplasia
marked inc uptake, depressed TSH prod
US - diffusely hypoechoic, 2-3 times normal size
Rad Tx - dose is (100uCi I-131 x grams of gland)/(% uptake at 24hrs)
divide again by 1000 to get dose in mCi, usually 5-10mCi
deliver approx 8000-10,000 rads to gland, 90% eu- or hypothyroid
Medical Tx - Propylthyouracil (PTU), suppresses production
Conservative Tx - many will just burn themselves out
risky in a pt w heart Dz

Struma Ovarii - ovarian teratoma w thyroid tissue
causes low thyroid uptake w low TSH & high T4
should NOT be treated w I-131
Thyrotoxicosis without visible uptake in thyroid gland
exogenous thyroid hormone, struma ovarii, De Quervain's Thyroiditis
also amioderone & other sources of excess dietary iodine can cause this

Thyroiditis
Hashimoto's Thyroiditis - Chronic Lymphocytic Thyroiditis, painless
#1 cause of goiterous hypothyroidism in USA
iodine deficiency more common in world pop
Autoimmune w familial predisposition, 30-40yrs in males
NUCS - low tracer uptake, mild nontender enlargement
Organification defect freq, high 4hr uptakes, low 24hr
prominent pyramidal lobe
US - initial hypoechoic but later densly echogenic

De Quervain Thyroiditis - subacute thyroiditis, probably viral
lymphocytic infiltrate & granulomas, painful tender gland & fever
may involve only one lobe
50% get short-lived severe hyperthyroidism due to gland destruction
DDx from Graves w iodine uptake, always dec with De Quervain
NUCS - low uptake & mult hypofunctioning areas
Tx - symptomatic, pain killers & B blockers for hyperthyroid Sx

Acute Suppurative Thyroiditis - focal diffuse enlargement, poss abcess

Congenital Dyshormonogenesis
Trapping Defect - defective cellular uptake of iodine
high doses of inorganic iodine overcome this & diffuse in
diagnostic dose not sufficient, secreted entirly in 24hrs
Organification Defect - deficient peroxidase activity
iodine not bound to tyrosine, High TSH, Low T4
gland has high uptake but very rapid turnover of I131
Pendred Syndrome - auto rec w peroxidase def & nerve deafness
Discordant Nodule - cold on Iodine scan due to organification defect
hot on Tc-99m scan, not dependent on organification
Deiodinase Defect - cannot release iodine from tyrosine
high I131 uptake, rapid intrathyroidal turnover
Thryoxin-Binding Globulin Deficiency - abn T4 transport, euthyroid
End-Organ Resistance to T4 - high serum T4, stippled Epiphysis

Substernal Thyroid - due to goiterous downward extention or abn migration
I-131 best due to ability to delay until blood pool has cleared
tissue usually has poor fxn, delay of 48-72hrs gives best target-background
Tc-99 pertechnatate poor due to high blood pool in region at 20-30min
Thyroid Malignancy - 10% of solitary cold nodules malig, mult less freq
Ultrasound guided FNA should be done on all nonfunctioning nodules
Risk factors - Hx of 1500rad Tx to neck, 20% abn, 5% get Ca
dec if higher doses due to gland destruction
inc if irradiated before 6yrs old, 20yr latent period
T4 suppression reduces risk, dec stim of gland
1 in 27,000 incidence in N population, no diff in aggresiveness

Papillary Carcinoma - 60%, unencapsulated & well differentiated
most in female >50yrs, mixed w follicular more freq under 40yrs
90% 10yr survival, worsens in older & w extrathyroidal Dz
lymphogenic spread in 40%, children 90%, hem mets to lung 5%
Psammomatous calc poss, Hypoechoic w cystic deg & nec
Pure papillary w no colloid formation rarely takes up significant I-131
often has mixed follicular elements which may take up iodine

Follicular Carcinoma - 20%, slow growing, early hematogenous MET
30% lytic met to bone, very rare in papillary
80% 10yr survival w/o extensive mets, 30% with
unencapsulated, well diff, no papillary elements, 25% multifocal
Follicular elements freq concentrate Iodine, mets responsive to Tx

Anaplastic Carcinoma of Thyroid - 15%, 5% 5yr survival, most 6mo
NO radioiodine uptake, >60yrs w equal sex incidence

Medullary Carcinoma - 5%, arises from parafollicular C-cells
Adolescent pts assoc w MEN II, older pts have sporadic occurance
MEN IIa - w parathyroid hyperplasia & pheochromocytoma (PMP)
MEN IIb - w ganglioneurocytomas & pheochromocytoma (GMP)
50% have early mets to bone, liver & lung, elevated calcitonin
90% 10yr survival w no nodes, 40% 10yr survival w nodes due to slow growth
Scan w Tc-99 DMSA, NO radioiodine or pertechnatate uptake
I-131 MIBG also, but only 30% sensitivity, can be therapy if taken up

Treatment for Thyroid Ca - Thyroid recieves 1.1Rad/mCi absorbed
Total Body Survey - 4 days post-surg, 5mCi, image at 48 or even 72 hrs
Treatment - 100mCi for thyroid residual, 150mCi local recur, 200mCi distant met
discharge when activity <29.9mCi or <5mRem/hr at 1meter
Retreatment - not considered for 6-12mo to avoid marrow suppresion
additional doses up to a total of 1Ci may be needed
thyroid replacement therapy stopped prior to Tx
Differentiated thyroid Ca does not take up iodine at N TSH levels
make sure TSH levels are above 30mU/liter
Tl-201 can be used for follow-up also, thyroxine need not be stopped

PARATHYROID SCINTIGRAPHY
Thallium-technetium subtraction
1-3mCi Tl-201 given, 2mm pinhole images aquired over 20min
accumulates homogeneously in both thyroid & parathyroid
1-10mCi Tc-99m given, images taken every min for 20min
accumulates only in thyroid, computer subtract
Sensitivity - 90% for adenoma >60mg, NO vis of hyperplasia
most can be visualized subjectively w/o computer subtraction
greater than CT or MRI for ectopic & post-op detection
Specificity - 43%, thyoid adenomas, Ca & lymph nodes also
etiology for Tl-201 uptake to adenomas etc unknown
Autonomous thyroid nodule or multinodular goiter can give false pos

Tc-99m Sestamibi - both parathyroid & thyroid take up in early phase (30min)
at 3hr delay thyroid washes out, also very sensitive & specific
20-25mCi, use planar images w a high resolution collimator

Primary Hyperparathyroidism
83% due to solitary parathyroid adenoma, mult very rare
most located at lower margin of thyroid lobes
15% due to parathyroid hyperplasia - assoc w renal failure
glands enlarge but 50% are not visualized
2% due to parathyroid carcinoma - most are functional but not all
Follow-up with US - do not be fooled by esoph or longus colli musc
always use doppler to asses suspiscious hypoechoic lesions
CT is also a good way to get anatomic conformation of etiology

Lung Scintigraphy

PERFUSION AGENTS

1. Tc-99m Macroaggrgated Albumin - from human serum albumin
stannous ions precipitates albumin to tin containing aggre
Tc-99m pertecnetate reduced by SnCl2 & tagged to MAA
physical & biologic t1/2 6hrs
90% of particles trapped in lung 1st pass occluding 1 in 1000 caps
protien lysed within 6-8hrs, taken up by RES, all <.1u RES
Image - Immediate w lg field camera & parallel hole low E collimator
QA - 90% w diameter of 10-90u, none >150u, use within 8hrs
Do not backflush w blood in syringe, inject supine
Dose - 4mCi w 200-700k particles, .25rads/mCi lung, .05rad total body
at least 60,000 particles must reach lung for adequate count
if "hot spots" seen indicates clumping, to few particles left
Ill pt w pulm art Htn or L to R shunt need fewer particle, 150k
tagged activity must remain the same though
children <5yrs need fewer particles & dec activity, 100-350k

2. Tc-99m Human Albumin Microspheres - 20-30u particles, t1/2 8hrs

VENTILATION AGENTS
1. Xenon-133 - 15mci dose, biologic t1/2 2-3min, 1rad to lung
fission product of U-235, decays to Cs-133, beta 374keV bad
gamma of 82keV & X-ray of 31keV, scatter inherent, bad res
3 phase Images - done in posterior postion
Single breath - inhalation of 10-20mCi to vital capacity
image 10-20sec in supine position, 65% sensitive to abn
can identify obstructive pulm Dz
Equilibrium - tidal breathing closed loop rebreather 3-5mi
allows tracer to enter poorly ventilated regions
Oblique scans may help corelation w perfusion scan
Washout - clearance images taken every 3min, best for COPD
Reveals air trapping, exhaled Xe caught in charcoal filt

2. Xenon-127 - cyclotron produced w high cost
172keV (22%) & 203keV (65%) allows images P perfusion study
.3rad to lung sig lower, easily stored due to t1/2 36.4 days
3. Krypton-81m - short t1/2 13sec, don't have to rebreath
eluted from Rb-81 generator, very costly
continuous ventilation for 6-8 views w low dose, 100mrad lung
dist dependent on vent, no wash out due to short t1/2
COPD is NOT assesed due to lack of wash out
can be used simultaneously w Tc-99 due to 190keV (65%) peak

4. Tc-99m DTPA aerosol - deliverd via nebulizer during insp
poor physiologic indicator of ventilation
NO washout phase, only shows initial equilibrium

5. O-15 labeled Carbon Dioxide - need on site cyclotron, t1/2 2min
rapidly diffuses across mem to capillary, dependent on circ
Cold Spot - caused by airway Dz preventing tracer from entry
Hot Spot - Accumulation of tracer due to poor perfusion
Emboli can be detected in preexisting COPD, 87% sensitive
PIOPED CRITERIA - revised, personalized, and rarly adhered to
segmental if >75% of seg involved, small if <25% involved
will detect 90% of emboli that occlude vessel >1mm

Normal - 0% probabiltiy of PE

Low - <20% probability of PE
small unmatched perfusion defects regardless of number or CXR
matched VQ defects with normal CXR
perfusion defect smaller than CXR abnormality
VQ defect correlating with a large plueral effusion
triple matched defect in the upper lobes
non-segmental defects (heart, diaph, dildo's etc)

Intermediate - 20-80% probability of PE
1 large or 2 moderate unmatched perfusion defects
VQ defect correlating with a small pleural effusion
triple matched defect in the lower lobes

High - >80% probability of PE
2 large unmatched perfusion defects
Perfusion defect larger than CXR defect

PATHOLOGIC FINDINGS
Perfusion defects tend to be larger than seen on angio

1. Unilateral Lung Perfusion - 2% incidence
PE - 25%, more than 95% originate in legs
Airway Dz - plueral or parenchmal in 25%, Ca in 25%
aspirated FB or bronchial adenoma (Carcinoid)
Congenital Heart Dz - 15%
Arterial Dz - Swyer-James Syn in 8%, blalock-taussig shunt
Pulm art stenosis or hypoplasia
Absent Lung - Pneumonectomy in 8%, congenital rare

2. Perfusion Defects
Vascular Dz - PE from clot, fat, air, tumor or heartworm
Vasculitis - Collagen Vasc Dz, IV abuse, Rad therapy, TB
Vascular Compression - Ca, Lymphoma, fibrosis, aneurysm
Altered Pulm Circ - Congen, Sequestration, venoocclusive Dz
Pulm Htn - large hila & upward redist, mult periph defects
Mitral Dz - sup segs of upper lobes & RML w inc ant activ
post lungs flattened, fissures accentuated & freq eff
Airway Dz - Asthma, Bronchiectasis, Bulla, Inf, lymangitic Ca
Matched VQ defects are hallmark of airway Dz
Bilat Lower Lobe Perfusion Defects - CHF, Alpha-1 antitrypsin Dz

3. Fat Embolism - NOT thromboembolic Dz, occur 1-2days P Fx or surg
Neutral trigycerides transport to lung
Lung converts to fatty acid, congestion, edema & hem result
fat droplets then enter to brain, kidney & skin
Triad of Petechial rash, mental status change & SOB
CXR - often N or peripheral & basilar alveolar consolidation
VQ - patchy heterogeneous perfusion defects, periph & basilar

4. Fatty Infiltration of Liver - Uptake of Xe-133 propotional
Alcoholic, Diabetic, obestiy, TPN, etc

5. Smoke Inhalation - smoke & other irritants
damage predisposes to infection, early Dx helps prevention
4th post-burn day Xe-133 shows focal areas of retention

6. Increased Pulmonary Venous Pressure - shifts perfusion to upper lungs
alpha-1-antitrypsin def, mitral stenosis, constrictive pericarditis, LV failure

Cardiac Scintigraphy

BLOOD POOL AGENTS
Ejection Fraction - Stroke Vol/End Diastolic Vol
SV = End Diastoloic Vol - End Systolic Vol
N L Vent - 67%, abn <55%, N R Vent 45%, greater EDV, same SV
87% sensistive & 90% specific for detecting CAD
regional wall motion abn most sensitive
better than excercise EKG
Atrial fibrillation prevents cardiac gating, poor study

1. Tc-99m labeled RBC's - #1 choice, good heart to lung ratio
Dose: 35mCi, 1.5rads to heart, .4rads whole body
Labeling to RBC occurs at Beta-Globulin chain of hemoglobin
in vitro - 50ml blood w Tc-99m reduced by stannous ion
95% labeling efficiency
Ultra-tag kit - uses only 2cc blood
in vivo - stannous pyrophosphate injected
15min later Tc-99m pertechnetate injected
70% bound, unbound portion excreted in urine
poor tagging in heparinized pts, Tc binds to IV tubing
D5 flush instead of saline causes poor binding also
Modified in vivo - stannous ion injected to reduce blood
15min later blood drawn into syringe containing Tc-99m
10 min later reinjected, 90% labeling efficiency
Imaging - .005sec per frame for 1200 frames during inj
after first pass gated aquisitions performed
gated aquisitions also made P excercise
Critical Organ - Spleen & blood

2. Tc-99m human serum albumin - good alternative in heperanized pts
poorer heart to lung ratio than RBC's

3. Tc-99m perfusion agents - first pass ventriculography can be performed

4. Gallium-67 - can be used to detect pericarditis

VENTRICULAR FUNCTION
First Pass Ventriculography - transit time of any Tc-99m IV
limited number of cardiac cycles, 3-5, ONE projecion only
RV Ejec Fraction - done in RAO w ventricles super-imposed
counts taken as bolus passes thru RV, then again when thru LV
peaks & valleys of the curves used to calculate EF of each
Correlates well w contrast ventriculography
Evaluates obs of SVC, reflux into IVC or R-L shunts
good for calc of CO & EF, contractility of RV
Shunts - Left to Right only, tight bolus is required
alteration in N activity curve
pulm to systemic flow ratio 1.2:1 or greater

Gated Blood Pool Imaging - Multiple Gated Aquisition (MUGA)
Done at Equilibrium P Tc-99m labeled RBC's have mixed
mult high qual images acquired over 2-10min, >200,000 counts
16-24 portions of the R-R cycle, cine
calc L vent ejec time (LVET), preejection period (PEP)
Fast L vent fill period & slow fill period (LVFT1 & LVFT2)
SV - Diastolic vol minus Systolic
Septal view best (LAO 45deg) for EF calc
EF = (ED-ES)/(ED-Background)
ventricle to background ratio as low as 2.5:1
High background estimate overestimates the EF
Low background estimates underestimate the EF
Stress - 6mil counts, 32 frames before & P excercise, inc EF by >5%
better than 1st pass, higher counts, can reject bad beats
can also asses pharmacologic effects
Paradoxical Images - (end systolic - end diastolic image)
any activity seen over ventricles indicates dyskinesis

Pathology Seen With MUGA - nonspecific when abn, do Tl-201 next
Wall Motion Defects - detects MI, aneurysm & contusion
at exercise detects ischemic dyskinesis in 60%
limited because only lat, septal & apex seen by 45deg LAO
Heart Failure - dec EF, prolong PEP, dec LVET & dec rate ejec
Hypertensive Heart - N sytolic indices & EF, prolonged LVFT1
Hypothyroidism - prolonged PEP, Norm EF
Aortic Stenosis - mild EF reduction, prolong LV emptying time
N rate of filling but prolonged emptying
Pericardial Effusion - wide band of low activity between heart & lung
Mitral or Aortic Regurg - causes inc SV in LV relative to RV
"Regurgitant Index" - 1 in N pt, >1.2 abn

MYOCARDIAL PERFUSION AGENTS
1. Thallium-201 Chloride - 3.5mCi for stress, 1.0mCi for rest
3 rads to kidneys, .5 to whole
Used for Acute myocardial infarct & CAD, better than EKG
Sensitivity 80% esp w severe stenosis & greater involvement
most sensitive to L main > LAD > RCA > LXC, 90% specific
collaterals & beta blocker dec sensitivity
K+ analog, uptake via Na/K+ ATPase, dist proportional to flow
<5% remains in blood pool P 15min, 90% in 90sec
4% goes to heart, inc 2% w exercise, peak activity 15min
R heart seen in 15% of N individuals or w R heart overload
Cor pulmonale, ASD, tet, corrected trasnposition etc
40% to muscle, 10% to lung, kidney's excrete 10% in 24hrs
Standard aquisition - ant, 40deg LAO, 60deg LAO & L lat
SPECT - 180deg from -45deg RAO to 135deg LAO
32 stops for 40sec each, 25min total scan time
imaging started 5-10 min after excercise complete to slow breathing

Excercise Images - first pass extraction
Peak HR 220-age, should reach 85%, diff if elderly
images suboptimal if limited by CP, fatigue, EKG, etc
Persantine - .15mg/kg over 4min, reverse w amynophyline
5x inc in coronary blood flow, "steel"
Adenosine - .14mg/kg over 6min, drug t1/2 6min
stop if BP drops greater than 10mm or >3 PVC's
90% stenosis symptomatic even at rest
50% sten often detected only w adequate stress
defect >15% of vent surface suggests >50% sten of art
RV better visualized during stress phase
lower pulm, liver, stom & spleen act
also more homogeneous dist than rest images

Delayed Images - redistribution w equilib of tracer in cells
Resting Reinjection - greater sensitivty to viable myocardium
ischemic but viable myocardium imaged at 2-6hrs
Redistribution 90% sensitive & specific for ischemia
fixed defects less specific - cardiomyopathy, sarcoid, malig
wash-out half life is 54min
N zones wash out & viable but ischemic zones inc uptake
Inc Lung Activity - LV failure, Pulm Venous Htn (mitral)
Inc RV Activity - Inc vent sys P, inc pulm art P or resis
Ant wall - L lat veiw, Post septum - LAO, apex - Ant view
False-Positive for Infarct - Infiltrating myocardial Dz, amyloid, sarcoid
Cardiac Dysfxn - cardiomyopathy, aortic stenosis
Abn perfusion for reason other than MI - contusion, fibros
corornary art spasm - lg stress defect, N rest
Normal Variant - focal thinning of myocardium, attenuation
inc in women due to breast

False-Negative - B-blocker, symetric defects, No delay image
insuffecient stress

2. Tc-99m Sestamibi - (Cardiolite), resting 8mCi, stress 22mCi (15-25mCi)
lipophilic molecule, rapidly crosses mem, binds to mitochondria
Rapid Clearance, myocardial uptake proportional to flow
Long retention w NO redistribution, excrete thru GB
Image - rest images 30min P inj, stress 3hrs later
reinject at peak of stress & reimage 30min later
improved photon flux w less radiation due to shorter t1/2
First pass procedure optional on resting injection
used to obtain ejection fraction
Standard aquisition - ant, 40deg LAO, 60deg LAO & L lat
SPECT - 180deg from -45deg RAO to 135deg LAO
64 stops for 25sec each, total scan time 30min
Advantage over thallium is less attenuation of photons in lg pt
can be done much more rapidly in acute setting, more expensive though

3. Tc-99m Teberoxime - 25mCi (Cardiotec), Very rapid clearance
High extraction efficiency, dist proportional to flow
Must begin immediately due to rapid washout
rest images can immediatly follow stress images

4. Combo - 3.5mCi Tl-201 for rest, 20mCi Cardiolite for stress
Stress portion can follow rest immediatly
Pitfall - false fill-in defects due to less attenuation of Tc

CARDIOVASCULAR PATHOLOGY

MYOCARDIAL INFARCT
1. Tc-99m Pyrophosphate - 15-20mCi, image 3-6hrs, HOT SPOT Image
PYP complexes w Ca+ Hydroxyappetite found in nec tissue 10-12hrs P
requires residual collateral blood flow, 30% max accum
peak at 24-72hrs after infarct, N by 10-14 days
prolonged uptake consider aneurysm, CHF, thrombus
90% sensitivity for transmural, 50% for subendocardial
low specificity of 60%, NOT helpful in N stress test & No Sx
Indications - Equivocal EKG, enzyme pattern or S/P open heart
Interpretation - grade 0-4, greater than grade 2 pos
1 - faint activity, 2 - actvity equal to ribs
3 - activity equal to sternum, 4 - greater than sternum
"Doghnut" pattern due to lg defect w no cent flow (Ant)
inf wall uptake suggests RV infarct, SPECT inc sensitivity
diffuse uptake w angina, myopathy, pericarditis, N bl Pool
10% false Pos - contusion, cardioversion, rad, pericarditis
calc heart valves, amyloidosis
5% false Neg - myocardial mets
Post-op open heart pts have elev CPK but new ischemia diff to eval
PYP specific for new ischemia & not altered by surg
SPECT can aide in specificity of uptake, eliminate chest wall defects

2. Indium-111 antimyosin - murine monoclonoal ab to myosin, Hot Spot

3. Cold Spot Imaging - perfusion study for acute MI, rest Tl-201
96% sensitivity within 6-12hrs, drops to 80% at 78hrs
Cannot distinguish between recent & old infarct

MYOCARDIAL ISCHEMIA
assesed directly w stress Tl-201 imaging
indirectly w w gated blood pool imaging, ie wall motion & EF
dec activity in apical & post segs not correlated w any Dz

INTRACARDIAC SHUNTS
Tc-99m MAA, pertechnetate, DTPA, Sulfur Colloid or RBC's
Raw data obtained from pulm activity curve

SVC OBSTRUCTION
see mult cervical & superficial thoracic collaterals, SVC not seen
Hot Spot seen in liver, probably quadrate lobe from umbilical circ

Liver and GI Scintigraphy

LIVER AGENTS AND PATHOLOGY

Tc-99m IDA Analogs - acetanilid iminodiacetic acid, 3-7mCi
3mCi + .5mCi for every increase of 2 in the bilirubin
3 rad/mCi for sm bowel, 2 rad upper lg bowel, .5 to GB, .01 whole
100-200uCi/Kg in children, must fast for 4hrs before

Prep - stop narcotics which inc sphincter of oddi Pressure
fasting 2-4hrs, if >24hrs may need cholecystokinin, 1mg to empty
Phenobarbitol - given for 5-7d primes liver to inc biliary sec

Imaging - 5-10min intervals for 60min, continue periodically up to 4hrs
if GB not vis by 30min give MS >.04ug/kg, inc sphincter of oddi pres
If Bowel not visualized give Narcan, 2mg to reverse optiate effect on oddi

Lipophility varies w side groups - determines renal/hepatic excretion
bind to albumin which dec renal excre, seperate in liver
Elevated Bilirubin reduces excretion, threshold higher for newer IDA's
HIDA - Hepatic, bilirubin threshold <8mg/dl, 15% renal excre
least lipophilic
BIDA - bilirubin threshold <20mg/dl, most lipophilic
DISIDA - (hepatolite), bili threshold <25mg/dl
QA - >90% Tc-99m IDA, <10% tin colloid or Na+ pertechnetate
"HIDA" Scan Findings
Liver - peak activity 5-10min, 85% to RES of liver, 8% to spleen (<liver)
Active Uptake - enters anion pathway of bile, delay = hepatocyte dysfxn
look for liver lesions on early views
Biliary Atresia - <5% of dose excreted into bowel

Biliary - secreted w/o conjugation, GB vis in 30min in all normals
CBD & cystic duct vis in 15min but not always seen in Norm
Cholecystokinin 1mg (.02-.04ug/Kg) 30min before if prolonged fasting
Paracolic activity indicates post-op bile leak
Acute Cholecystitis - 99% specific if GB not vis at 4hrs
inc activity in liver adj to GB fossa due to inflam
Morphine .04mg/kg causes spasm in sphincter of oddi, fill GB
False Pos - recent food, fasting, cholangio ca in cystic duct
liver disfxn, alcoholism, pancreatitis
False Neg - Acalculus Cholecystitis, duodenal tic simulating GB
Chronic Cholecystitis - Delayed filling or bowel activity before GB
Acalculous Cholecystitis - may fill normally, false neg for cholecysitis
use GB ejection fraction - see below
CBD Obstruction - GB visualized but no bowel
may have very hot central liver activity
DDx - narcotic induced oddi contraction, give narcan
Rupture or Fistula - lg area of abn activity collects, esp in 24hr

GB Ejec Frac - inc detect of acalc cholecystitis
Give CCK as above, >30% dec in activity normal
Chronic cholecystitis or acalculus type poss if less, Surg?

Bowel - excreted to duo in 30min, NO enterohepatic recirc
Enterogastric reflux may indicate biliary gastritis
located posterior, do LAT aquisition to diff GB from bowel
can also give water to wash-out bowel if question remains
Tc-99m Sulfur Colloid - liver-spleen scan
Tc-99m pertech & Na+ trisulphate heated together for 10min
aggregate into colloid particles .1-1u in diameter (MAA is 15u)
Phagocytosis by RE - 85% accum in liver, 10% spleen, 5% marrow, NEVER clears
Accum in lung only if macrophage infiltrated II' to infec
QA - >92% remain at origin of ascending chromotography
upper limit for particle size 1u, smallest .001u, average .1u, use before 6hrs
Dose - 3-6mCi, .3rad/mCi to liver, .02 to marrow, .02 whole
Imaging - 15-30min P injection
Sulfur Colloid has the lowest background activity of any agent
EDTA - added to sulfur colloid kits to bind excess Al 3+ ions
prevents aggregation w RBC's which cause inc liver & lung activity

Hepatomegaly - #1 abn found in the liver, most due to fatty infil
can have a mottled appearance

Colloid Shift - diffuse hepatic Dz shifts uptake to spleen & marrow
Cirrhosis, hepatitis or chronic passive congestion
Hematopoietic Dz - can augment spleen & marrow perfusion
Long term corticosteroid therapy, Ca or systemic illness
Inc pulmonary uptake due to macrophage in lung also poss

Focal Hot Liver Lesions
IVC or SVC obs - inc perfusion to quadrate lobe
Due to collateral flow via umbilical vien
Budd-Chiari Syn - Caudate lobe stands out, all other dec
caudate drained by mult sm tributaries direct to IVC
Focal Nodular Hyperplasia - varying amount of Kupffer cells
60% N uptake, 10% hot (30% cold)
Regenerating nodules of cirrhosis
Right lobe atrophies 1st, compensatory hypertrophy of Left

Focal Cold Liver Defects
Neoplastic - hepatoma, hemangioma, hepatic adenoma & 30% of FNH
85% sensitive & 80% specific for mets if >2cm
Adenoma has a strong assoc & FNH a weak assoc w birth control
Hepatoma creates a cold defect but will take up Ga-67
Infection, abcess, cyst, trauma, N variant
Multiple - mets #1, GI, pancreatic, lung, Breast, gyn
mets can also have hot regions within them

Defects in Porta Hepatis - N variant, parenchymal thinning
Biliary Causes - dil of bile ducts or GB hydrops
enlarged nodes, mets, cysts, postsurg changes
Mottled Hepatic Uptake - Fatty infil #1 cause of hepatomegaly
Cirhosis, hepatitis, granulomatis
Lymphoma, amyloidosis, post chemo or rad therapy

Displaced Liver - COPD can inferiorly displace & flatten dome
Situs Inversus, always confirm marker position

SPLENIC SCINTIGRAPHY

Agents - use sulfur colloid or heat denatured RBC's
Pyrophosphate injected, 20min later 20ml of RBC's drawn
Incubate w 2mCi Tc-99m, heat to 49.5deg C for 35min
overheating causes fragmentation, inc liver uptake
Image 20min post injection
Splenic Infarct - most common cause of cold defect, wedge usually
"functional asplenia" - lake of uptake in an intact spleen, sickle cell
Hematoma, Lymphoma, Abscess, Mets - use WBC label scan to DDx
Accescory Spleen - can cause false pos WBC scan, DDx w sulfur colloid
Leukemia - esp CML can have N app, may be enlarged & hot

GASTROINTESTINAL SCINTIGRAPHY

Gatroesophageal Reflux - done in 6-9mo old, up to 2yrs
.5-1mCi sulfur colloid given in 300ml acidified orange juice
Image supine at 30-60sec intervals for 60min, can use abd pressure
Esoph counts minus background x 100 = Reflux in %
3% normal, can also give evidence of aspiration
Gastric Outlet Obs - done same way only background not subtracted
image in upright position
Radionuclide Esophagram - 250-500uCi sulfur colloid in 10ml H2O
Image while pt drinks thru a straw, diff if hiatal hernia or reflux present

Gastric Emptying - 3mCi Sulfur Colloid mixed w egg or liver pate
simultaneous use of 100-200uCi In-111 DTPA to asses liquid phase
Image at baseline, 10, 30, 60 & 90min, fig activity
Norm has 50% of baseline solid activity gone by 45-100min, LINEAR (60min)
t1/2 for liquids is 10-60min
Acute Delay - stress, narcotics, post-op, nicotine
Chronic Delay - outlet obs, vagotomy, ulcer, diabetes
Abn Rapid Empty - ZE syn, bilroth, duo ulcer, celiac sprue
7. Meckel's Scan - embryologic rem of the vitelline duct
Rule of 2 - 2% of pop, 2% become symtomatic usually before 2y/o
2ft from ileocecal valve, 2in long, 2:1 male
Tc-99m Pertechnatate - 50uCi/Kg
accumulates in mucous sec cells of gastric mucosa
occurs within 5-20min P injection, void to find near bladder dome
>85% sensitive & 95% specific
False Neg due to abscence of gastric mucosa or obscured by N structure
False Pos due to ectopic gastric mucosa or cyst, abscess or AVM
Improve visualization w Pentagastrin, stimulates uptake
also Glucagon inhibits peristalsis & Cimetidine decreases excretion

GI Bleeding - better than angio which requires >.5ml/min active
Tc-99m Sulfur Colloid - requires active bleeding <.05ml/min
Clears in 3.5min, poor for upper bleed, liver/spleen act
image 1 per min x 15min then one 15min delay, no long delay
rare false positves, less sensitive than tagged RBC study

Tc-99m labeled RBC's - detects blood pool of approx 5ml
activity stays in blood stream and at site of hem
Image every 2sec for 64sec, static images q 5min for 30min
glucagon improves localization of site by dec bowel act
93% sensitivity if >500ml/24hrs lost, less sensitive to UGI
False Pos - Hemangioma, AVM, physiologic uptake by GI
Free pertech can localize stomach, NG to prevent flow down
Horseshoe kidney can sim midgut bleed, penile activity

Tc-99m Pertechnetate - for bleeding from gastric mucosa
includes meckel's or intestinal duplication
for adults up to age 25, independent of bleeding rate
avoid irritation of lining w barium or prep of any kind
Dose - 5-10mCi, accumulates in functioning mucus sec cells
Image q 2-3sec for 1min, then q 5min for 20min
enhanced by 3-6 hrs of fasting & NG suction
Pentagastrin 6ug/kg stimulates gastric prod of pertech
Cimetidine 300mg qid x 48hrs reduces release of pertech
False pos - barret's, duo ulcer, UC, Crohn's, AVM
False neg - ulcerated epithelium

Schilling's Test - Co-57 substituted for N cobalt in B12
Co-57 - 122keV, t1/2 of 270 days
.5uCi or Co-57 given in .5ug of B12 given orally
1000ug of unlabeled B12 given subQ to saturate tranport protiens
2 consecutive 24hr urine samples obtained
All of the labeled B12 absorbed will be excreted, N = 18%
2ml aliquots of urine are measured & compared to standards
Part II - labeled B12 also combined w intrinsic factor
asses for malabsorbtion at ileum
Pernicious Anemia - autoimmune Ab against gastric parietal cells
effects elderly northern europeans, M=F
gastric atrophy is main feature, antrum is spared
B12 excretion <6%, part II will be >10%
Megaloblastic Anemia - any cause of ilieal malabsorbtion
may be the only manifestation of malabsorbtion, part II <6%
Acidification of ileum can also effect absorbtion, Zollinger-Ellison
Simultaneous test can be run using CO-57 & CO-58, one w intrinsic factor

Oncoscint - In-111 antibody specific to adenoca of colon & ovary
1mg antibody labeled w 5mCi In-111
normal uptake seen at the site of a colostomy & marrow

Renal Scinitigraphy

RENAL AGENTS

Renal Agents for assesing function
Tc-99m DTPA - DiethyleneTriamine Pentaacetic Acid
choice for perfusion, GFR, obs uropathy & reflux
Chelating agent, 5-10% bound to plasma protein
100% Glomerular Filtration - 20% extracted w each pass
no resorbtion, tubular excretion or metabolism
slight underestimation of GFR because 5% plasma bound
Renal Cortical Activity at 2-4min, renal pelvis at 3-5min
aorta at 15-20sec, spleen & kidneys before liver
Clearance from pelvis accelerated by lasix 20-40mg IV
Ureter - may be seen transiently, contiuous presence means dilation
Dose - 10-20mCi, .85rad/mCi cortex, .5 bladder, .15 whole
Biologic t1/2 20min

Tc-99m MAG3 - MercaptoAcetyltriGlyceride, 10mCi
has largely replaced glucoheptonate & Hippuran
Renal Plasma flow agent sim to Hippuran, better dosimetry
True plasma flow = MAG3 flow x constant (1.4-1.8)
80% tubular secretion, 20% filtered, 2.5X better extraction than DTPA
highly bound to plama protien, rapid tubular secretion
Image - 1sec/frame for 60sec, then 15sec/frame for 30min
curve plotted, static images from 6 summations of 5min each

I-131 Orthoiodohippurate - Hippuran, tubular fxn & plasma flow
80% by prox Tubular Secretion, 20% glom filt, extraction ratio of 1
agent w highest extraction ratio w/o binding to parench
excellent for Estimated Renal Plasma Flow calc (ERPF)
Max renal concentration at 5min, transit time 2-3min
Dose 200uCi, .06rad/200uCi bladder, .02 kidney, .02 whole
give 2% free iodine to protect thyroid (Lugol's Sol)
Image q 15sec for 20min, Uptake determined at 2-3min image, dec w ATN
Avid adrenal uptake, diff to sep from renal, can Dx pheochromocytoma

Lasix - given if collecting sys activity high
if activity does not clear then obs present

Captopril - ACE inhibitor prevents angiotensin I to II conversion
removes efferent arteriol constriction caused by angiotensin
if vasc stenosis present then delay activity curve & inc retention
Dose - 25-50mg
Complication - hypotention, give fluids etc
Renal Cortical Agent
Tc-99m DMSA - DiMercaptoSuccinic Acid
images functioning cortical mass, R/O pseudotum
High protien binding, slow plasma clearance by glom filt
5% at 1hr, 30% by 14hrs, biologic t1/2 >30hrs
50% of dose collects in prox renal tubules by binding sulfhydril groups
Dose - 5mCi, 15-18Rads to kidneys, .014rads/mCi gonads, .015 whole
Image at 3hrs, but poss anywhere from 1-24hrs, SPECT better for structural
Pitfalls - some cases of renal tubular dysfxn may have disproportinate low uptake
Renal Tubular Acidosis - mild renal impairment but no DMSA uptake
also, dysfxn due to obstruction may not be appreciated

Combined Renal Cortical & Function assesment - MAG3 choice
Tc-99m Glucoheptonate - rapid plasma clearance & excretion
45% cleared by glom filtration & tubular excretion in 1hr
pelvocalyceal sys seen well during 1st hr
5-15% accum in tubular cells by 1hr & remains 24hrs
Dose - 10-20mCi, .17rads/mCi renal, .015 nads, .008 whole
Image collecting sys in 1st 30min, renal parench at 1-3hr

Differential Renal Function - generation of time-activity curve
Tc-99m DTPA - measure prior to excretion at 1-3min
serial images q 1.5sec for 30sec, then q min for 30min
inc hepatic & ST uptake w impaired renal fxn
measurements accurate in renal obs if done in 1st 1-3min
Not poss to predict functional recovery P relief of obs
Much more accurate than IVP
>5% difference between kidneys should be further investigated

Radionuclide Cystogram - .5-1mCi Tc-99m pertech-saline to bladd
post upright views obtained thruout filling, calc residual
Lower rad dose in child than contrast study
gives 50-100mRem to pelvis, much less than VCUG

Relative absorbed doses
Gonadal : DMSA > DTPA > Glucoheptonate
Renal: DMSA > Glucoheptonate > DTPA = IOH
Bladder : IOH > DTPA > Glucoheptonate > DMSA
children have less concentrated urine
children also urinate more so they get less dose

RENAL PATHOLOGY

Renal Failure - glomerular filt decreased, DTPA poorly concentrated
Hippuran & MAG3 are excreted by tubules, vis if fxn >3% of N, BUN 50-150
DMSA does even better due to it's binding to the tubules
All will show some dec uptake & excretion
appearance improves after dialysis in severe cases
anions that compete for excretion are removed
Imapaired renal fxn will give erroneus delay in clearance P Lasix
US - used to R/O obs which cannot be assesed in presence of failure

Renal Artery Stenosis - MAG3 & hippuran more sensitive than DTPA
dependent on renal plasama flow
Symetric involvement more difficult to detect
F/U after angioplasty - asseses functional result

Obstuction - 20-40mg IV lasix used to DDx from non-obs dilation
peak effect is at 15-30min w continued effect for up to 2hrs
Renal Failure - makes DDx difficult due to lack of diuretic response
DMSA can be used to asses degree of residual fxn
if one kidney below 15% of total renal fxn damage is permanent
w DTPA % of fxn must be assesed before collecting sys fills
Adults - Stones #1, 80% pass w/o need for intervention, may scar
present w intermittent pain worsened by flued ingestion, neoplasm #2
Children - UPJ obs #1, mult etiology, crossing vessels, folds, abn shape etc
5% assoc w duplicated collectin sys, upper moiety obs, inserts inf & med
38% of siblings also affected if one child has congenital obs
Neonates - low GFR, clearance may be slow normally
Parenchymal atrophy is most serious sequela of obs, glomerulus last to die

Renal Infarct - wedge shaped defect, 50% present w hematuria, 50% bilat
Atherosclerotic Dz from aorta or emboli from heart vegetations
Only 4% due to atherosclerosis of renal art
DMSA is the best agent, 50% of dose localized to kidney in 1hr
SPECT gives best anatomic detail
Tc99m Glucoheptonate in children, lower rad dose than DMSA

Renal Masses - evaluation limited by low resolution, US better
Psuedotumor - accumulates activity like N tissue, ie column of bertin
Renal Cell Ca - use DMSA, early blood flow shows high activity
in late phase it is photopenic
Pyelonephritis - DMSA gives excellent distinction, affected area cold
Ga-67 is taken up in both acute & chronic
uptake also seen w abcess, Renal Cell Ca, sarcoid, post radiation etc

Chronic Pyelonephritis - reflux resulting in cortical scar
DMSA shows as cold segments & dec % of total GFR
must recheck after 3 months to R/O changes of acute pyleo
DTPA - may see late spike in activity due to reflux
especially common after micturation

TRANSPLANT EVALUATION
ureter prominent for 2wks II' to inflam
normal has maximal cortical uptake in 2-6min
Acute Tubular Necrosis - perfusion N, delayed tubular clearance
usually seen within 4 days & rarely P 1mo
occurs in cadeveric transplant due to extended ischemia
NOT seen w living donor
US - used to R/O obs which cannot be detected if in failure
Transplant Rejection - 3 different phases, cause loss of perfusion
Hyperacute - Ab present at time of transplant, occurs in 1-12hrs
Thrombosis of vasc bed, functional destruction
Acute - cellular response occurs in 1-3wks
accelerated form possible in 1day
sensitized lymphocytes destroy cells w/o help from humoral Ab
Chronic - humoral Ab response over months to years
damages endothelial & interstitial cells
occurs in all to some degree
Urinoma - walled off form seen in 5% post-op
can also produce free ascites
delayed visualization w ATN or rejection, decub veiws helpful
Renal Art Thrombosis - sim app to rejection or renal vein thromsosis
Cyclosporine Toxicity - usually only occurs w prolonged excess levels
Tubular cells most effected, causes glomerulosclerosis & interstitial fibrosis
N blood flow, dec function, vasoconstriction poss in acute phase

Adrenal Scinitigraphy

ADRENAL SCINTIGRAPHY

1. Adrenocortical Imaging Agents
I-131 Iodocholesterol - NP-59, incorporated into LDL
absorbed from LDL by adrenal cortex
Detects ACTH independent Cushing syn, adrenocort Ca
hyperandrogenism & hyperfunctioning adenoma
Dose - 1-2mCi, 26rad/mCi to adrenal, 8 to ovaries, 1.2 whole
Lugol solution given to suppress thyroid
Image at 5-7d interval P injection
3-5d interval if used w dexamethasone sup

Se-75 Selenocholesterol (Scintadrin) - similar uptake properties

Dexamethasone Suppresion Test - synthetic glucocorticoid
suppresses N adrenal but not autonomously functioning adenoma
causes both Cushing's & Conn's type adenomas to stand out

2. Sympathoadrenal Imaging Agents
I-131 metaiodobenzylguanidine (MIBG) - sim to norepi
Accumulates in neurosec granules of neurocrest origin cell
Chromaffin cells of adrenal medulla - 90% of pheochromocytoma
melanocytes, C-cell of thyroid, panc cell, Kulchitsky
neuroblastoma, carcinoid, paraganglioma, chorioca
Dose - .4mCi, 35rad/mCi to adrenal medulla, .22 whole
Lugol solution given for 7-10 days to block N thyroid uptake
Image at 24, 48 & 72hrs P injection
False neg - block w imipramine & tricyclic antidepressant

I-123 MIBG - allows spect imaging, image at 6 & 24hrs
bone uptake is always abnormal, indicates marrow involvement

In-111 Octreotide (octreoscan) - detects somatostatin receptor sites on tumors
neuroblastoma, pheo, carcinoid, pancreatic islet cell, medullary thyroid
breast Ca & lymphoma also - if positive may respond to somatostatin therapy
dosage can be boosted to Tx positive masses as well - dose??

Pheochromocytoma - can be evaluated w I-131 MIBG, a nor-epi analog
localizes to sympathetic tissues, 90% sensitivity for pheo masses
N localization to liver, spleen, salivary, heart & bladder
Renal scans also w Tc-99m DTPA subtracted from MIBG images
done only when equivicol CT & clinical findings, "The tumor of 10's"
10% in children, 10% extraadrenal, 10% malig, 10% w MEN II, 10% bilat
most <10cm, undiagnosed in 1/3, may be fatal, check VMA level in urine

Scrotal Scinitigraphy

SCROTAL SCANNING
Done w 15-20mCi Tc-99m Pertechnatate
angiographic images at 5sec intervals for 60sec, then delays
Epididymo-Orchitis - inc uptake in comma shaped epidydimis
Testicular Torsion - dec uptake in affected testicle up to 4hrs
Bull'seye of rim activity develops at 6hrs from collateral hyperemia
if activity exceeds that of femoral artery prognosis is poor
painful, no enlargement
Missed torsion - "bull's eye" w cold center, inc around periph
nonspecific, also seen w abcess & hematoma
Hydrocele - painless enlargment in side w dec uptake
usually normal angiographic flow can be demonstrated
assoc w inflam & neoplastic processes, NOT seen w varicocele
Bull's Eye - also seen w tumor, abscess & hematoma

Positron Emission Tomography

PET

Decay - postive B decay, rarly occurs above N of 55
unstable proton yeilds e+ and turns to a nuetron
Positron matter-antimatter anihilation rxn w an e-
annihilation photons result w 511keV each
F-18 FDG - 110min t1/2, Dose 5-10mCi
N-13 ammonia - 10min t1/2
O-15 - 2min t1/2 & C-11 - 20min

Cyclotron Produced Isotopes - I-123, In-111, Tl-201, Ga-67, Co-57