Introduction to SPECT Image Processing

Our project is based on data collected using Single-Photon Emission Computed Tomography or what the medical world refers to as SPECT. This technology is used in nuclear medicine where the patient is injected with a radiopharmeceutical (a harmless tracer chemical of some sort) which will emit gamma rays. The radioactivity is collected by an instrument called a gamma camera.

The gamma camera is made up two massive cameras opposite each other which rotate around a center axis 180 degrees. Each one is lead-encased and weighs about 500 pounds. The camera has three basic layers - the collimator (which only allows the gamma rays which are perpendicular to the plane of the camera to enter), the crystal, and the detectors. The collimation of the rays faciliates the reconstruction since we will be dealing with data that comes in only perpendicularly. At each angle of projection, the data will be back projected only in one direction.

When the Gamma Camera rotates around the supine body, it stops at interval angles to collect data. Since it has two heads, it needs to only rotate 180 degrees to collect data around the entire body. The collected data is planar. Each of the cameras collects a matrix of values which correspond to the number of gamma COUNTS detected in that one direction at the one angle.

There are some errors due to the characteristics of the camera and the procedure of data acquisition such as Center of Rotation and Attenuation. To simplify our research, we have saved these corrections for further developments.

Applications in the Real World