The Nuclear Medicine Department (NMD) of the Clinical Center has developed a small field-of-view (FOV) gamma camera which has great promise for practical, high-resolution imaging of small animals. The system is based on a novel position-sensitive photomultiplier tube (PMT), instead of multiple non-position-sensitive PMTs used in standard, large FOV gamma cameras. Unfortunately, the position-sensitive PMT does not possess either a linear voltage analog of event position, or a uniform energy response across the tube face. Previous collaborative efforts between the NMD and our laboratory have, independently, demonstrated the need for methods to correct for motion artifact during planar gamma camera studies of the brain. A technique was developed, utilizing a Polhemus position/orientation measurement subsystem, to perform the necessary corrections. We are currently developing an Intel Multibus II computer system that will allow geometric, energy, and motion corrections to be performed sequentially, in real time on data from the small FOV gamma camera. This image correction system will be interposed between the gamma camera and its data acquisition computer intercepting and processing the data as they are transmitted from the camera to the computer. Three coupled 386/486 processors comprise the Multibus II system. These processors are dedicated to input (analog-to-digital conversion), computation (geometric, energy and motion correction), and output (digital-to-analog conversion or digital transmission), respectively. System control software has been developed, as well as programs to acquire data from the analog-to-digital converter modules and to display both uncorrected and corrected data arrays. All geometric and energy correction software has been completed. Software development is continuing with the completion and testing of output routines for the digital-to-analog converter modules, and the integration of real-time data from an independent PC-based position/orientation measurement system.
