General Nuclear Medicine Part 1

For Medical StudentsFor Medical Students

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Introduction to Nuclear MedicineBone scanKUB system• Renal scan-renogram• Testicular scan• Radionuclide cystography

Lung scanRadionuclide venography

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Nuclear medicine is a medical specialty which uses very small amount of a radioactive substance or a chemical compound labelled with a radioactive substance, called “radiopharmaceutical”or tracers to image or treat diseases.

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Endocrinology eg. Thyroid scan, Parathyroid scanCardiovascular system eg.Myocardial perfusion scan,Radionuclide venographyGenitourinary system eg. Renogram, Testicular scan,Radionuclide cystographyPulmonary system eg. Perfusion/ Ventilation lung scanSkeletal system eg. Bone scanGastrointestinal system eg. Liver scan, Hepatobiliary scan, GE reflux studyTumor imaging eg. Ga-67 scan for Lymphoma, I-131scan for pheochromocytoma, Tc-99m MIBI for parathyroid adenoma

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Functional*SensitiveQuantitativeVery safeMinimally invasiveLow radiation exposureScreeningFollow-up

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Not widely availableGive minimal radiation Generally non-specificRequire NM instrument &radiopharmaceuticalsHigher cost than routine X-ray or U/S

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Low costAvailablePure gamma emitterOptimal gamma energy (100-200 keV) * 140Optimal half life *6 hrSafeChemically active

* Tc-99m is the most ideal agent !

Tc-99m

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Radiopharmaceutical

Patient

Gamma Camera

Images

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Radioisotopes eg. I-131, Tc-99m

Radiolabeled compounds eg. Tc-99m MDP for Bone scan, Tc-99m MAA for Lung scan

* 1 Organ Many R’pharmaceuticals1 R’pharmaceutical Many organs

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Planar gamma camera

SPECT = Single Photon Emission Computed Tomography

PET = Positron Emission Tomography

PET/CT

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PET:Metabolic imagingUsing positron-emitting radionuclidesBiological tracers (C, N, O, F)

More sensitiveBetter imagesWhole body evaluation

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Introduction to Nuclear MedicineBone scanKUB system• Renal scan & renogram• Testicular scan• Radionuclide cystography

Lung scanRadionuclide venography

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Tracer : 99mTc-MDPMechanism: Adsorption to the hydroxyapatitehydroxyapatite crystalRoute : IV injectionTechnique :

Patient preparation : noneAfter inj: good hydration & frequent voidingImaging 3 hr. post injectionViews : Whole-body, anterior and posterior & static images as required

Visualization : The skeletal system

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Indications :Bone metastases*; tumor staging, evaluate bone pain in cancer patientsUndetermined bone pain (wo CA Hx)Infection; osteomyelitisBone trauma; stress fracture

Advantages:Sensitive > plain X-ray *Whole-body evaluationLow radiation

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ANT POSTANT POST

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Diffusely increased axial skeletal uptake with low or no visualized renal uptake

Diffuse metastatic diseasePrimary: prostate*, breast,lung

Metabolic bone diseaseHyperparathyroidismRenal osteodystrophy

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Phase 1; Vascular phase: 60 s dynamic immediately pi.Phase 2; Soft-tissue (blood-pool) phase: 5 min pi.Phase 3; Delayed (bone) phase: 3 hr pi.

INDICATIONS:Infection: DDx acute osteomyelitis vs cellulitisAvascular necrosisTumors: primary tumorOthers

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Vascular phase

Soft-tissue

delayed 3-hr

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Phase I : Vascular phasePhase II : Soft tissue phasePhase III : Bone phase

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Introduction to Nuclear MedicineBone scanKUB system• Renal scan-renogram• Testicular scan• Radionuclide cystographyLung scanRadionuclide venography

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Renal scintigraphy

Testicular scan

Radionuclide Cystography

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Cortical renal scanRenal scar in children with UTI

Renal scan and renogramTo evaluate (split) renal blood flow & renal functionTo evaluate urinary drainage

Diuretic renographyTo evaluate urinary tract obstruction

Captopril renographyTo detect renovascular HT (RVHT)

Radionuclide cytographyTo detect VU reflux

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Tracers : 99mTc-DTPA, 99mTc-MAG3, etcRoute: IV injectionTechnique : Good hydration

Dynamic study for 30 min. in posterior view (native kidneys), anterior view for transplanted kidney. renogram (3 phases)

Uses : Separate renal functionUrinary tract obstruction-Diuretic RenogramRenovascular hypertension-Captopril renogramOthers

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L R LT RT

Posterior

Flow: 1-2 min

Renograms or Renal time-activity curvesRenal Scan-30 min

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Severity of urinary tract obstruction

A-Severe obstruction, good renal functionB-Severe

obstruction, reduced functionC-Less severe obstruction, reduced function

A

B

C

Normal

Time-activity curve

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Deterioration of renal function after chronic urinary tract obstruction

Normal

Time-activity curve

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Diuretic Renograms

Normal

Furosemide Injection

Obstructed

Non-bstructed

Time-activity curve

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Diuretic Renography

T1/2 < 10 min

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Tracer : Tc-99m pertechnetate IV.Positioning : Special*Imaging : Flow and static imagesAim : To DDx Acute testicular torsion VS Acute epididymoorchitisTesticular Torsion flow & uptakeAcute epididymo-orchitis flow &uptake (inflammation)

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Introduction to Nuclear MedicineBone scanKUB system

• Renal scan-renogram• Testicular scan• Radionuclide cystography

Lung scanRadionuclide venography

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Perfusion Lung ScanTracer : • 99mTc-MAA

Route : IV injectionTechnique : Planar images 6 views; anterior, posterior, Rt. lateral, Lt. lateral RPO,LPO

Ventilation Lung ScanTracers :

• 133Xe• 99mTc aerosol- 99mTc-DTPA,

99mTc-phytate• Technegas

Route : InhalationTechnique : Planar images 6 views as in perfusion study

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Pulmonary embolism*Pulmonary hypertensionRight-to-left shuntPrior thoracic surgery

To determine lung function in the affected lung & the potential consequence of removal of diseased lung

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Tracer: Tc-99m MAA, particle size=10-30 uMechanism: Lodged in precapillary arterioles in proportion to regional blood flowDose: 2-5 mCi, 200,000-600,000 particles, block < 1/1000 arteriolesRoute: IV (Not draw blood back into syr !)Imaging: 6 views, Ant, Post, RPO, LPONormal: Uniform distribution

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PE Segmental perfusion defects

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Multiple hot spots

Technique: Drawing Pt’s blood into Tc-99m MAA syringe form clumping hot spots

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Tracers:Gaseous agents:

Xe-133 (washin-equilibrium-washout)Xe-127Kr-81m (Rb-85m generator)

Radioaerosol (particulate agents): 0.5 um99mTc-DTPA, 99mTc-SC, 99mTc-phytate

Technegas: 99mTc labeled fine carbon particles (by heating 99mTcO4- in a graphyte crucible at 1500 C in pure argon atmosphere for 15 sec), size = 0.02 um

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O2

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Perfusion lung scanVentilation lung scanCXR within 24 hrs

Criteria: Modified PIOPED criteria *NormalHighNondiagnosticVery-low probability

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Uniform distribution of the radioactivityNo V/Q defectNormal Q scan is virtually exclude PE !No extrapulmonaryaccumulation

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Nonuniform distributionPerfusion and/ or ventilation defect

Segmental or nonsegmental defect

Extrapulm accumulation

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Clinicals : Unreliable- dyspnea, pleuritic chest pain, hemoptysisLAB: D-dimer > 500 ng/ml ABG: HypoxemiaECG: tachycardia, nonspecific ST-T change,S1Q3T3 (rare)CXR: Normal*, oligemia, othersVQ lung scan: VQ defectPulmonary CTA : clotPumonary angiography: clot (gold standard)

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Typical scintigraphic findingsSegmental perfusion defects Normal V scan No corresponding abnormal radiographic findings

V/Q mismatched defects

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Ant Post LPO RPO

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Tc-99m MAA perfusion lung scanPresence of radiotracer in the brain and kidneysPrecaution: Limited MAA particles.

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Introduction to Nuclear MedicineBone scanKUB system

• Renal scan-renogram• Testicular scan• Radionuclide cystographyLung scanRadionuclide venography

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http://www.nhlbi.nih.gov/health/dci/Diseases/pe/pe_causes.htm

http://www.youtube.com/watch?v=I0yJTkW9y9s

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Clinicals : UnreliableLab tests : D-dimerColor Doppler ultrasonographyRadionuclide Venography (RNV)In-111 labeled plateletIn-111 labeled antifibrin AbTc-99m labeled peptides (Acutect)CT/MR venographyContrast Venography *** [Gold standard]

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DVT, Compression, Doppler Lower Extremity. This image shows a side by side, of the common femoral vein with and without compression. Since the vein does not fully collapse, this is an evidence of a DVT.Clot is also seen, as well as a filling defect in the vessel of the noncompressed vein with color Doppler. (Photo contributor: Stephen J. Leech, MD,RDMS.)

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Tc-99m RBC Venography

Ascending Rdn Venography: Tc-99m SC, Tc-99m phytate, Tc-99m MAA***

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Tracers : Tc-99m MAA, Tc-99m phytateUses : Venous occlusion (DVT)-proximal deep veins**Technique

IV. injection of the tracer into pedal veins of both feetImaging: during on and off tourniquet over both anklesMultiple overlapping static or whole-body images upto IVC level

* If MAA RNV + Q lung scan (same setting)

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Inject a tracer via (bilateral) foot veinsOn tourniquets above ankles to visualize deep veins and off tourniquets for superficial veinsMultiple overlapping static images upto IVC level or whole-body image

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Abrupt termination of the flowPresence of filling defectIrregular or asymmetric flowAbnormal colaterallsNonfilling of the deep veins, with +ve other signs

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Most reliable for Dx (gold std.)Need skilled teamGood anatomic visualization (calf iliac veins & IVC)More InvasivePotential risksNot suitable for frequent F/UNot provide information about associated PE

Reliable results esp. proximal v SimplerPoorer anatomic details (Good for proximal veins)Less invasiveSafe More suitable for frequent F/UProvide information about associated PE (Tc-99m MAA)

Contrast Venography Radionuclide Venography

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Or blood-pool radionuclide venographyequilibrium stageInject the radiotracer via any veinNeed high-resolution collimatorImage quality depends on labeling efficiency

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ADVANTAGESDo not need foot vein access, easierPossible less painful

DISADVANTAGESImage quality depends on labeling efficiencyNot direct evaluation of venous flowLess anatomical detailsConcomitant Q lung scan is impossible.

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SUMMARY

What is Nuclear Medicine?PrincipleAdvantages & Disadvantages

Bone scanKUB systemV/Q lung scanRadionuclide venography