By: Katie M.

PET Scans

Positron Emission Tomography Scan

Creates a 3-D image of the body process

Ionizing radiation - gamma rays emitted

Radiation dose for one PET scan: 7 mSv

PET Scans: UsesSearches for cancer

Diagnoses Alzheimer's disease years before any symptoms occur

Works to see if bypass surgery would be effective

Detects tumors

Registers brain functions

PET Scan ProcessDetects emitted pairs of gamma

rays/photons from a positron-emitting tracer

Tracer is (radionuclide) - positive beta decay

Tracer is only radioactive for a short period of time

Tracer is injected into blood circulationTracer isotopes used: Carbon 11, Nitrogen

13 and 150, and Fluorine 18

PET Scan Process Burst of light when annihilated particles

come in contact with the scintillator in the machine

Annihilate: collision of electron and positron = gamma ray photons

Scintillator: a material that illuminates when struck by incoming particles/photons

Flashes are all connected in the same process as the CT scan, but is more difficult because the data set collected is poorer than the CT’s data collected

PET Scan Side Effects

Possible allergic reaction to tracer

Pregnant women may not be allowed to have this scan due to the radiation

Injection sight of the tracer may become sore and red

PET Scanner

PET Scan

Annihilation Process

SPECT ScanSingle Photon Emission Computed Tomography

Shows how blood flows through arteries and veins in the brain

Differs from PET scan: tracer remains in blood stream instead of being absorbed by tissues

Can detect reduced blood flow in the brain

SPECT Scan UsesPre-surgical evaluations of uncontrolled

seizures

Finding stress fractures in spine (Spondylolysis)

Blood deprived areas of the brain after a stroke

Detects tumors

SPECT Scans Process

Radiolabled (emits Gamma rays) chemical tracer is injected into the blood stream

Radioactive Tracers: Iodine 123, Technetium 99, Xenon 133, Thallium 201, and Fluorine 18

Gamma rays are emitted by the tracer, which are detected by the scanner

Scanner collects emitted gamma rays and translates them as an image

SPECT ScanLimited areas of images are shown because it

stays only in the blood stream

SPECT scans are cheaper and more readily available than PET scans

1 scan = .7 - 1 rem of radiation

Average yearly radiation = about 360 milli-rems

SPECT Scans Side Effects

Typically no allergic reaction to tracer because there is no dye injected

Considered a safe and standard medical procedure

Less radiation is given off by SPECT scans than in a CT scan or X-ray

SPECT Brain Scan

SPECT Scanner