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The performance of an improved intraoperative γ-probe for radioassisted oncological surgery is presented and discussed. The probe is based on a square array of four 5×5 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 γ-emission hot points may be carried out in two different, independent ways: (1) Finding out the position of the probe corresponding to the maximum value 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 between the counting rate performed by orthogonal, adjacent halves of the array vanish (differential method). This makes the new probe sensitive to the bidimensional gradient of the γ-ray flux, measured on the scanned plane. Furthermore, the algebraic sign of the difference indicates in which direction the probe should be moved to best locate the γ-source. Due to these characteristics, both the errors in the localization of a single, small size γ-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 performed in order to evaluate the performances of different types of collimators in reducing the contribution of a second source close to the source under examination. This situation occurs, for example, when the probe is used in the framework of the sentinel-node surgical technique. |
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