INTRODUCTION Emission Computed Tomography is a technique where by multi cross sectional images of tissue function can be produced The technique of SPECT is generally considered as two separate modalities.SINGLE PHOTON Emission Computed Tomography involves the use single gamma ray emitted per nuclear disintegration. Positron Emission Tomography makes use of radio isotopes such as gallium-68, when two gamma rays each of 511KeV, are emitted simultaneously.
SPECT What is SPECT? SPECT is short for single photon emission computed tomography. As its name suggests (single photon emission) gamma rays are the sources of the information rather than X-ray emission in the conventional CT scan. Why SPECT? Similar to X-ray, CT, MRI, etc SPECT allows us to visualize functional information about patient’s specific organ or body system.
THEORY AND INSTRUMENTATION SPECT is a technology used in nuclear medicine where the patient is injected with a radiopharmaceutical which will emit gamma rays. We seek the position and concentration of radionuclide distribution by the rotation of a photon detector array around the body which acquires data from multiple angles.
CONT… Each of the cameras collects a matrix of values which correspond to the number of gamma counts detected in that direction at the one angle. Images can be reprojected into a three dimensional one that can be viewed in a dynamic rotating format on computer monitors, facilitating the demonstration of pertinent findings to the referring physicians
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
Cont… 2. Improvement in these parameters is a constant goal of the SPECT researcher. Improvement in both of these parameters simultaneously is rarely achieved in practice. Collimation Computers in radiology and nuclear medicine Image acquisition
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.
POSITRON EMISSION TOMOGRAPHY In the simplest PET camera two modified sophisticated cameras called Anger cameras are placed on opposite sides of the patient. This increases the collection angle and reduces the collection times which are the limitations of SPECT In PET, radiopharmaceuticals are labeled with positron emitting isotopes.
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.
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 , so is SPECT . 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.