PORTABLE GAMMA-SPECTROMETRY SYSTEM FOR SIMULTANEOUS MONITORING OF RADIOTRACERS IN-VIVO USING CDTE AND CDZNTE RADIATION DETECTOR PROBES

A portable gamma spectrometry system has been designed to simultaneous ly monitor various radiotracers in vivo. This system includes a portab le IBM(R) compatible personal computer and miniaturized gamma radiatio n detector probes based on the semiconductor materials CdTe and CdZnTe . The computer has been expanded with pulse processing and analyzing e lectronics for three independent inputs and a software package. A port able NIM Bin cabinet, equipped with charge loss correction electronics , is an optional addition. This can be used to improve the peak to val ley ratio, the spectral resolution and the peak efficiency of the CdTe detectors. Two different probe housings have been developed, a rectan gular and a cylindrical shaped housing. The rectangular probe is desig ned for clinical use. This device contains one CdTe or CdZnTe crystal with a sensitive area of 10 X 2 mm (2 mm thick) or 10 X 3 mm (3 mm thi ck) and a preamplifier circuit. The probes can be attached to each oth er, in order to form a linear array. The cylindrical detector probe is developed for implantation in animals and contains two parallel switc hed CdTe crystals with a sensitive area of 5 x 5 mm (2 mm thick) and a preamplifier circuit. Both probe housings were made from a tungsten a lloy (2 mm thick), which provides good shielding for low-energy gamma radiation isotopes frequently used in Clinical settings (In-111, I-123 , Tc-99m, I-125). The detection sensitivity of the probes was very sim ilar to the sensitivity of a standard gamma camera when comparing meas urements in different in vitro models and in patients. In addition, th e detector probes more accurately measured small, local radiation sour ces as compared to the gamma camera. This gamma spectrometry,system ha s also been used to simultaneously measure the accumulation of Tc-99m- labelled platelets and I-123-labelled fibrin after arterial injury in rabbits. This has allowed the in vivo monitoring of different doses of antithrombotic therapies in animals by observing the dynamic growth a nd interactions between different blood components during thrombotic p rocesses.