ScintigraphyScintigraphy

Presented by M.A. Kaeser, D.CPresented by M.A. Kaeser, D.CSpring 2009Spring 2009

DefinitionDefinition A nuclear medicine procedure, such A nuclear medicine procedure, such

as a bone scan. The term is derived as a bone scan. The term is derived from the decay of the radionuclide from the decay of the radionuclide and its resultant gamma radiation or and its resultant gamma radiation or scintillations. The number of scintillations. The number of scintillations corresponds to the scintillations corresponds to the concentration of the isotope.concentration of the isotope.

Nuclear MedicineNuclear Medicine Images are generated as the uptake and Images are generated as the uptake and

distribution of administered distribution of administered radiopharmaceuticals are detectedradiopharmaceuticals are detected

Provides vital information regarding tissue Provides vital information regarding tissue perfusion, physiology, and biochemistryperfusion, physiology, and biochemistry

Physiologic and metabolic changes often Physiologic and metabolic changes often precede gross structural alteration of precede gross structural alteration of diseased tissue by hours, days or even diseased tissue by hours, days or even weeksweeks

Key factor in determining early diagnosis Key factor in determining early diagnosis and proper treatment protocols and in and proper treatment protocols and in establishing an accurate prognosisestablishing an accurate prognosis

Radionuclide Bone ScanningRadionuclide Bone Scanning Most frequently performed nuclear Most frequently performed nuclear

medicine technique (50%)medicine technique (50%) Used to evaluate soft tissue, bone Used to evaluate soft tissue, bone

and joint disordersand joint disorders• Fractures, infections, arthritides, tumors Fractures, infections, arthritides, tumors

and osteonecrosisand osteonecrosis

HistoryHistory

Skeletal scintigraphy Skeletal scintigraphy radiopharmaceuticals were first radiopharmaceuticals were first introduced in the early 1960sintroduced in the early 1960s

1971 Technitium 99-MDP polyphosphate 1971 Technitium 99-MDP polyphosphate compounds were introducedcompounds were introduced

Today we use diphosphonates which Today we use diphosphonates which have faster blood clearance and higher have faster blood clearance and higher skeletal uptakeskeletal uptake

Examination ProcedureExamination Procedure Three phases which represent the Three phases which represent the

distribution of the tracer over the course of distribution of the tracer over the course of timetime• Phase 1 – Flow phase or radionuclide angiogram - Phase 1 – Flow phase or radionuclide angiogram -

tracer is intravascular – images are obtained tracer is intravascular – images are obtained every 2-3 seconds for 30 secondsevery 2-3 seconds for 30 seconds

• Phase 2 – Blood pool phase – the tracer is located Phase 2 – Blood pool phase – the tracer is located in the extravascular space – the body is imaged 5 in the extravascular space – the body is imaged 5 minutes after injectionminutes after injection

• Phase 3 – Bone scan phase – 2-4 hours after Phase 3 – Bone scan phase – 2-4 hours after injection – represents clearance of the tracer from injection – represents clearance of the tracer from the vessels and soft tissues and concentration the vessels and soft tissues and concentration into the skeletoninto the skeleton

Blood Flow PhaseBlood Flow Phase Show radionuclide in the arterial, Show radionuclide in the arterial,

capillary, and venous phasescapillary, and venous phases Variations may occur in the blood Variations may occur in the blood

flow to the extremities depending on flow to the extremities depending on the vascular status and activitythe vascular status and activity

Blood Pool PhaseBlood Pool Phase Shows radionuclide in the Shows radionuclide in the

extravascular spaceextravascular space Vascular structures such as kidneys, Vascular structures such as kidneys,

liver, spleen and uterus are seen and liver, spleen and uterus are seen and should not be mistaken for sites of should not be mistaken for sites of abnormalityabnormality

Bone Scan PhaseBone Scan Phase Show radionuclide in the skeleton and soft Show radionuclide in the skeleton and soft

tissuetissue Metaphyseal regions of long bones show Metaphyseal regions of long bones show

higher uptake than diaphyses – due to higher uptake than diaphyses – due to higher bone turnover rate in the metaphyseshigher bone turnover rate in the metaphyses

Areas of highest uptake are the sternum and Areas of highest uptake are the sternum and SI jointsSI joints

The anterior wings of the iliac bones and the The anterior wings of the iliac bones and the coracoid processes normally show coracoid processes normally show considerable uptake of the radionuclideconsiderable uptake of the radionuclide

Scoliosis – the concave side of the spine Scoliosis – the concave side of the spine appears hotter than the convexappears hotter than the convex

Patient PresentationPatient Presentation Children have high diffuse bone uptake and Children have high diffuse bone uptake and

prominent uptake around the growth platesprominent uptake around the growth plates Elderly patients tend to have poor-quality bone Elderly patients tend to have poor-quality bone

scansscans Heavy patients have poor quality bone scans Heavy patients have poor quality bone scans

owing to the greater amount of soft tissue, which owing to the greater amount of soft tissue, which causes more scatter and higher attenuation of the causes more scatter and higher attenuation of the photons in the soft tissues because of the greater photons in the soft tissues because of the greater distance of the detectors from the skeletondistance of the detectors from the skeleton

Poor hydration prevents optimal clearance of the Poor hydration prevents optimal clearance of the radionuclide from the soft tissuesradionuclide from the soft tissues

Renal failure prevents good soft tissue clearanceRenal failure prevents good soft tissue clearance Corticosteroids may produce generalized Corticosteroids may produce generalized

decreased skeletal uptakedecreased skeletal uptake

Absorbed Patient DoseAbsorbed Patient Dose Exact dose is difficult to determineExact dose is difficult to determine Influenced by:Influenced by:

• Tracer biodistributionTracer biodistribution• Organ pathologyOrgan pathology• Renal functionRenal function

DoseDose Approximately 50% of the injected dose is Approximately 50% of the injected dose is

taken up by the skeleton within 2-6 hourstaken up by the skeleton within 2-6 hours Normal renal excretion results in 50-60% Normal renal excretion results in 50-60%

of the tracer eliminated within 24 hours of of the tracer eliminated within 24 hours of injectioninjection

Bladder receives the highest doseBladder receives the highest dose May be reduced by pre-examination May be reduced by pre-examination

hydration and frequent voiding after examhydration and frequent voiding after exam Whole-body dose is approximately 0.13 Whole-body dose is approximately 0.13

rad (average dose for CT scan of the L/S is rad (average dose for CT scan of the L/S is 3-5 rad.3-5 rad.

ContraindicationsContraindications Pregnancy because transplacental Pregnancy because transplacental

transmission of radiopharmaceuticals transmission of radiopharmaceuticals is possibleis possible

Breast milk will carry isotope activity Breast milk will carry isotope activity for several days after the studyfor several days after the study

Image generationImage generation Radiopharmaceutical emits gamma Radiopharmaceutical emits gamma

rays that are detected by an rays that are detected by an instrument and transformed into instrument and transformed into electrical signals that ultimately electrical signals that ultimately generate a computer image of the generate a computer image of the tracer agent activity and tracer agent activity and concentrationconcentration

Radiopharmaceutical AgentsRadiopharmaceutical Agents Dozens are employedDozens are employed Most widely used – Technitium 99 – Most widely used – Technitium 99 –

MDPMDP• 6 hour half-life 6 hour half-life • Principal photon energy of 140 keVPrincipal photon energy of 140 keV

Several Bone Scan UsesSeveral Bone Scan Uses Insufficiency fractures in metabolic Insufficiency fractures in metabolic

diseasedisease TraumaTrauma Metastatic DiseaseMetastatic Disease Disuse osteoporosisDisuse osteoporosis OsteomalaciaOsteomalacia OsteonecrosisOsteonecrosis OsteomyelitisOsteomyelitis

Insufficiency fractures in metabolic Insufficiency fractures in metabolic diseasedisease

Pubic ramiPubic rami Femoral necksFemoral necks Femoral condylesFemoral condyles Metaphyses of the proximal and Metaphyses of the proximal and

distal portions of the tibias, sacrum distal portions of the tibias, sacrum and calcaneusand calcaneus

Tend to be bilaterally symmetric and Tend to be bilaterally symmetric and occur in the metaphyses of long occur in the metaphyses of long bones of the lower extremitiesbones of the lower extremities

TraumaTrauma Increased blood flow associated with bone Increased blood flow associated with bone

repair results in marked repair results in marked radiopharmaceutical accumulationradiopharmaceutical accumulation

Occult fractures demonstrate an increased Occult fractures demonstrate an increased perfusionperfusion

Important for follow up to assess for Important for follow up to assess for fracture non-unionfracture non-union

Compression fractures of the spine reveal Compression fractures of the spine reveal a horizontal band of increased tracer a horizontal band of increased tracer activity, typically affecting the superior activity, typically affecting the superior endplateendplate

Metastatic DiseaseMetastatic Disease Random pattern of areas of Random pattern of areas of

increased uptakeincreased uptake Predominantly in the axial and Predominantly in the axial and

proximal appendicular skeletonproximal appendicular skeleton

Disuse OsteoporosisDisuse Osteoporosis Increased bone turnover and Increased bone turnover and

increased uptake on a bone scanincreased uptake on a bone scan

OsteomalaciaOsteomalacia Hot spots in adjacent ribs on both Hot spots in adjacent ribs on both

sides with no history of traumasides with no history of trauma Hot spots in the inferior tips of the Hot spots in the inferior tips of the

scapulaescapulae

OsteonecrosisOsteonecrosis Early osteonecrosis shows decreased or Early osteonecrosis shows decreased or

absent uptakeabsent uptake When bone becomes revascularized and When bone becomes revascularized and

begins to remodel, increased radiotracer begins to remodel, increased radiotracer uptake is identifieduptake is identified

Necrotic process defined by collapse, Necrotic process defined by collapse, deformity and flattening of the joint is deformity and flattening of the joint is characterized by a rim of increaed characterized by a rim of increaed radiopharmaceutical uptake surrounding a radiopharmaceutical uptake surrounding a photopenic zone (double line sign)photopenic zone (double line sign)

Scintigraphy CasesScintigraphy Cases http://gamma.wustl.edu/home.htmlhttp://gamma.wustl.edu/home.html