NUCLEAR MEDICINE: OVERVIEW Jiraporn Sriprapaporn, M.D. Division of Nuclear Medicine Department of Radiology Siriraj Hospital
Thyroid ScanTechnique: Prep: No T4 at least 2 wks Tc-99m iv. or I-131 orally Static imaging at 20 min or 24 hr respectivelyIndications: Solitary thyroid nodule or MNG with dominant nodule (suspected CA) Congenital hypothyroid, R/O ectopic thyroid Substernal goiter (I-131) Hyperthyroidism with single thyroid nodule; R/O toxic adenoma Evaluate thyroid remnant post thyroid surgery
Thyroid Scan: TechniquesTc-99m thyroid scan I-131 thyroid scan For routine use !! For special purposes 2 mCi TcO4- IV 60-100 uCi I-131 is injected orally given Imaging at 20 mins Imaging at 24 hr. later later Trapping Trapping + Organification Withdraw T4 at least 2 wks before thyroid scan
I-131 Total-body Scan (TBS): TechniquesPatient preparation: Withdraw thyroid H (T4) 4-6wks prior to TBS, TSH > 30 mIU/LDiagnostic dose of I-131: 2-5 mCi orally givenAnterior and posterior whole-body imaging at 72hrs laterTBS can also performed after 3-7 d of RAI Rxdose
I-131 Total-body ScanThyroid T Lung metas. CBladder B
Bone Scan: IndicationsCancer patients: Bone scan is anextremely sensitive and cost effectivemodality for staging Evaluate patients with bone pain, increased alkaline phosphate, or hypercalcemia to rule out osseous metastasis.Infection: DDx cellulitis & osteomyelitisReflex sympathetic dystrophy (RSD)
Myocardial Perfusion StudyTo evaluate the presence of significantcoronary artery disease (CAD).Indications Suspected CAD Preoperative evaluation Evaluate extent of myoc ischemia & infarct Guide for treatment-med or revasc Pre-post revascularization procedures Risk stratification post MI
MPS: Information1. The presence or absence of significantCAD2. The extent and severity of ischemia orscarring of the myocardium3. Functional information about resting LVwall motion and LVEF. (gated SPECT)4. Information about the stress part of thestudy which can be treadmill exercise orpharmacological
GI SystemEsophageal transit Liver-spleen scantime Spleen scanGE reflux study Hepatobiliary scanGastric emptying Salivary scantimeGI bleeding study RBC scan Meckel’s diverticulum scan
GE Reflux StudyOther name: Milk scanTechnique: NPO Tc-99m phytate is orally taken. Dynamic imaging to cover E-G junctionIndications: Vomiting, failure to thrive,recurrent pneumoniaInterpretation: Regurgitation of theradioactivity from stomach into eso.
Gastric Emptying:Technique: Tc-99m phytate, In-111 Chloride Liquid vs solid meal Dynamic imaging for 90 min curvesIndications: Dyspepsia, eating disorders Diabetes After GI surgery: to evaluate gastric outlet obstruction or "dumping" syndrome.
Normal Solid-LiquidGastric Emptying StudyLIQUID SOLID Lag phase
GI Bleeding StudyTechnique: NPO Tc-99m RBC, Tc-99m phytate iv. Dynamic imaging for at least 1 hr.Indication: Lower GI bleedingMech: ExtravasationPositive: Active bleeding- hot spot,move along peristalsis
Positive GI Bleeding •Tc-99m RBC •Hepatic flexureExtravasation of the tracer into bowel lumen Focal area of increased activity, move // bowelmovementPattern depends on site of bleeding & bowelperistalsis
Meckel’s Diverticulum ScanTechnique: NPO Tc-99m pertechnetate IV. Serial imaging upto 2 hrs.Mech: Ectopic gastric localization No active GI bleeding requiredIndication: Lower GI bleeding in small childrenPositive: Abnormal intraabdominal hot spot // gastricactivity
Liver Spleen ScanTechnique: No prep required Tc-99m phytate iv. Static planar imaging 6 views + SPECTUses: Evaluate the size & shape of the liver & spleen, also function (hepatocellular dysfunction (colloid shift) To evaluate SOL-nonspecific !
Hepatobiliary ScintigraphyTechnique: NPO at least 4 hr. Tc-99m DISIDA iv. Mech: Hepatocytes Dynamic imaging for at least 1 hrIndications: Acute RUQ pain- acute cholecystitis Biliary tract obstruction, neonatal Jx Bile leakInterpretation:Normal-visualize biliary tract,GB, small bowel within 1 hr.
Rim sign in acute cholecystitiscurvilinear band of increased activity along the hepatic margin abovethe GB fossa.The rim sign is identified in about 20-30% of patients with acutecholecystitis,The PPV for acute cholecystitis is about 95% when a rim sign isidentified in association with non-visualization of the GB at one hour.Approximately 40% of patients who demonstrate the rim sign willhave complicated cholecystitis
Rim sign in acute cholecystitisRefers to increased pericholecystic hepatic activitywithout GB visualization.The rim sign appears as curvilinear band of increasedactivity along the hepatic margin above the GB fossaand is usually identified early in the examination.It may be due to increased flow and/or impairedhepatocyte radionuclide excretion.The rim sign is identified in about 20-30% of patientswith acute cholecystitis,The PPV for acute cholecystitis is about 95% when a rimsign is identified in association with non-visualization ofthe GB at one hour .Approximately 40% of patients who demonstrate therim sign will have complicated cholecystitis (extensivenecrosis, perforated or gangrenous GB), thus thepresence of this sign indicates the need for moreemergent surgery. auntminnie.com
Cystic duct signThe dilated cystic duct sign refers to a nubbinof activity projecting from the proximal end ofthe common bile duct medial to thegallbladder fossa.It is believed to represent the a patent cysticduct distal to the site of obstruction.This sign is observed in about 7% of patientswith acute cholecystitis and should not bemistaken for a small, shrunken gallbladder.
Radionuclide Venography Tracers : Tc-99m MAA, Tc-99m phytate Uses : Venous occlusion (DVT)-proximal deep veins** Technique IV. injection of the tracer into pedal veins of both feet Imaging: during on and off tourniquet over both ankles Multiple overlapping static or whole-body images upto IVC level* If MAA RNV + Q lung scan (same setting)
Tc-99m MIBI Scan Normal DTC s/p TT & RAI Rx with Lt cervical LN metas. Abnormal
Parathyroid ScanSensitive modality to detect parathyroidadenoma (or hyperplasia), also ectopic.Sensitivity for adenoma is > 95% and forhyperplasia is between 75 to 85%.Many patients with hyperparathyroidismpresent with bone pain, renal stones, orhypercalcemia.Technique: Single isotope-Tc-99m sestamibi Dual isotopes- MIBI & TcO4-