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Toronto Notes 2019 Nuclear Medicine Medical Imaging MI27
Radionuclide Ventriculography
• 99mTc-taggedtoredbloodcells,taggedalbuminisalsoacceptable
• firstpassthroughRV→pulmonarycirculation→LV;providesinformationaboutRVfunction,presence
of shunts
• cardiacMUGAscansumsmultiplecardiaccycles,usuallyatleast200beats
• evaluationofLVfunctionandregionalwallmotion,ejectionfraction
• imagesareobtainedbygating(synchronizing)thecountacquisitionstotheECGsignal
• canassessdiastolicdysfunction
• providesinformationonejectionfraction(normal=50-65%),ventricularvolume,andwallmotion
• indications:mostcommonlytomonitorpotentialcardiactoxicitywithchemotherapyorherceptin,asa
gold standard of ejection fraction in defibrillator workup
Abdomen and Genitourinary System
HIDA Scan (Cholescintigraphy)
• IVinjectionof99mTc-disofenin(DISIDA)or99mTc-mebrofeninwhichisboundtoprotein,takenup,and excreted by hepatocytes into biliary system
• canbeperformedinnon-fastingstatebutpreferNPOaftermidnight
• indicatedinworkupofcholecystitiswhenabdominalultrasoundresultisequivocal:
■ acute cholecystitis: no visualization of gallbladder at 4 h or 1 h after administration of morphine ■ chronic cholecystitis: no visualization of gallbladder at 1 h but seen at 4 h or after morphine
administration
• gallbladdervisualizedwhencysticductispatent(rulesoutacutecholecystitiswith>99%certainty),
usually seen by 30 min-1 h
• differentialdiagnosisofobstructedcysticduct:acute/chroniccholecystitis,decreasedhepatobiliary
function (commonly due to alcoholism), bile duct obstruction, parenteral nutrition, fasting less than 4 h
or more than 24 h
• alsousedtoassessbileleakspost-operativelyorintrauma
• gallbladderejectionfraction(>38%isnormal)canbemeasuredafterafattymealorcholecystokininto
assess for biliary dyskinesia
RBC Scan
• IVinjectionofradiotracerwithsequentialimagesoftheabdomen(99mTcRBCs) • GIbleed
■ if bleeding acutely at <0.5 mL/min, the focus of activity in the images generally indicates the site of the acute bleed, look for a change in shape and location on sequential image, requires active bleeding to localize (more sensitive than angiography in detecting slower bleeding)
■ if bleeding acutely at >0.5 mL/min, use angiography (more specific, better for localizing, both diagnostic and therapeutic)
• liverlesionevaluation
■ hemangioma has characteristic appearance: cold early (limited blood flow to lesion), fills in later
(accumulation of tagged cells greater than surrounding liver parenchyma)
Other Important Nuclear Medicine Abdominal Tests
• Meckel’sScan:uses99mTcpertechnetate;givepatientranitidinepremedication;Meckel’sdiverticulum contains gastric mucosa which will light up at the same time as the stomach and get brighter with time like stomach
• 111Inoctreoscan:asomatostatinanalogusedforevaluationandstagingofneuroendocrinetumours including carcinoid; gastrinoma and carcinoid tend to be more octreotide avid than insulinoma.
• iodinatedMIBG:anorepinephrineanalogue,usedforpheochromocytoma,neuroblastomaand
medullary thyroid cancer most commonly; limited cardiac applications as above
• solidandliquidgastricemptying:astandardizedsolidorliquidmealislabelled,usuallywith99mTc
sulfur colloid and gastric emptying studied over time. There are normal ranges for solids and liquids
Urea Breath Test
• indication:diagnosisofgastricH.pyloriinfection
• patientadministered14C-labelledureaorally,ureametabolizedbyH.pyloritoammoniaand14CO2,
14C-labled CO2 is measured via plastic filament detectors or liquid scintillation
Functional Renal Imaging
• evaluationofrenalfunctionandanatomyusing99mTcDTPAor99mTcMAG3
• frequentlyusedtoprovideindexofrelativefunctionbetweentwokidneys
• frequentlyusedinadultstoassessforUPJobstruction(byassessingtheclearancehalftimewith
furosemide), and assess renal transplants or as a nuclear GFR study in patients wanting to donate
kidneys
• inchildren,imagingwith99mTcDMSAisusedtoassessforpyelonephritis
• inchildren,theinjectionoftracerintothebladderviafoleycatheterisoftenusedtoassessforreflux