An inexpensive microprocessor-controlled multichannel scaling system for in vivo radiotracer studies

A multichannel scaling (MCS) system has been developed to monitor the biological distribution of radiotracers in vivo. The design of this system permits the simultaneous collection of data from up to four radiation detectors. The evolution of detected count rates is displayed in real time as a histogram with a minimum channel width of 1 s. Each point in the data arrays can accommodate more than 16 million counts. The low-power Schottky integrated circuits used can readily process the maximum count rates that sodium iodide detectors can produce. The four counting units together with control circuitry were constructed on a single custom IBM PC expansion board.