An improved hand-held four-detector gamma-probe for radioassisted oncological surgery

The performance of an improved intraoperative gamma-probe for radioassisted oncological surgery is presented and discussed. The probe is based on a sq uare array of four 5 x 5 mm(2) coplanar CdTe room temperature semiconductor detectors and each detector has an independent read out electronic chain, allowing an original handling of the signal. Therefore, the search for gamm a-emission hot points may be carried out in two different, independent ways : (1) Finding out the position of the probe corresponding to the maximum valu e of the total counting rate, on the basis of a trial and error procedure ( typical for the conventional probe); (2) Finding out the position of the probe where both the differences betwee n the counting rate performed by orthogonal, adjacent halves of the array v anish (differential method). This makes the new probe sensitive to the bidimensional gradient of the gam ma-ray flux, measured on the scanned plane. Furthermore, the algebraic sign of the difference indicates in which direction the probe should be moved t o best locate the gamma-source. Due to these characteristics. both the erro rs in the localization of a single, small size gamma-source and the average measuring time are practically halved with respect to those obtained with a conventional single detector probe. In addition, a computer analysis is p erformed in order to evaluate the performances of different types of collim ators in reducing the contribution of a second source close to the source u nder examination. This situation occurs, for example, when the probe is use d in the framework of the sentinel-node surgical technique. (C) 2000 Elsevi er Science B.V. All rights reserved.