SPECT

TECHNOLOGY

-NIKITA JAVIA

-GURUNATH APTE

INTRODUCTION

• Emission Computed Tomography is a technique where by multicross sectional images of tissue function can be produced

• The technique of SPECT is generally considered as two separatemodalities. SINGLE PHOTON Emission Computed Tomographyinvolves the use single gamma ray emitted per nucleardisintegration.

• Positron Emission Tomography makes use of radio isotopes such asgallium-68, when two gamma rays each of 511KeV, are emittedsimultaneously.

SPECT

• What is SPECT?

SPECT is short for single photon emissioncomputed tomography. As its name suggests (single photonemission) gamma rays are the sources of the informationrather than X-ray emission in the conventional CT scan.

• Why SPECT?

Similar to X-ray, CT, MRI, etc SPECT allows us tovisualize functional information about patient’s specificorgan or body system.

How does a SPECT scan work?

• A SPECT scan integrates two technologies to view your body: computed tomography (CT) and a radioactive material (tracer). The tracer is what allows doctors to see how blood flows to tissues and organs.

• Before the SPECT scan, you are injected with a chemical that is radiolabled, meaning it emits gamma rays that can be detected by the scanner.

• The computer collects the information emitted by the gamma rays and translates them into two-dimensional cross-sections. These cross-sections can be added back together to form a 3D image of your brain.

• A SPECT scan is primarily used to view how blood flows through arteries and veins in the brain. Tests have shown that it might be more sensitive to brain injury than either MRI or CT scanning because it can detect reduced blood flow to injured sites.

• SPECT scanning is also useful for presurgical evaluation of medically uncontrolled seizures (Fig. 1).

What does a SPECT scan show?

GAMMA CAMERA• The instrument used in nuclear medicine for the

detection of gamma rays is known as gamma Camera

• The components making up the gamma camera are

1. Camera Collimator

2. Scintillation Detector

3. Photomultiplier Tube

4. Positron Circuitry

5. Data Analysis Computer

Reconstruction

• Reconstructed images typically have resolutions of

64×64 or 128×128 pixels, with the pixel sizes ranging

from 3–6 mm. The number of projections acquired is

chosen to be approximately equal to the width of the

resulting images

• Scanning is time consuming, and it is essential that

there is no patient movement during the scan time.

Movement can cause significant degradation of the

reconstructed images.

ADVANTAGES

• Localization of defects is more precise and more

clearly seen by the inexperienced eye.

• Extend and size of defects is better defined.

• Images free of background.

SPECT APPLICATIONS

• Heart imaging

• Brain Imaging

• Tumor detection

• Bone Scans

A SPECT scan of a patient with uncontrolled complex partial seizures.

• This type of scanning is also useful in diagnosing stress fractures in the spine (spondylolysis), blood deprived (ischemic) areas of brain following a stroke, and tumors.

COMPARISON OF PET AND SPECT

• SPECT imaging is inferior to PET because of

attainable resolution and sensitivity. Different

radionuclide is used for SPECT imaging that emits a

single photon rather than positron emission as in PET.

• The use of collimator results in a tremendous

decrease in the detection efficiency as compared to

PET.

QUALITY CONTROL

• A comprehensive set of acceptance tests is the basis for an effective quality control program.

• Acceptance tests indicate whether the scintillation camera meets published specifications

• Flood field images must be acquired and evaluated daily• spatial resolution must be tested once each week.• parameters such as multiple-window spatial registration, collimator

uniformity, system sensitivity, should be evaluated.• Pixel size must be calibrated to avoid errors in attenuation

correction and distortion when cardiac and brain reorientation software is used.

• A quality control program may be time-consuming, but, from the standpoint of maximum benefit to patients and confidence in clinical interpretations

CONCLUSION

• SPECT being a nuclear medicine imaging modality ,

it has all the advantages and disadvantages of nuclear

medicine can be highly beneficial or dangerous on the

application

• In spite of this , Today , nearly all cardiac patients

receive a planar ECT or SPECT as part of their work-

up to detect and stage coronary artery disease.