DOSIMETRIC EVALUATION OF THE TWO-PHASE COMPUTED TOMOGRAPHY IN PARATHYROID GLANDS IMAGING.

Abstract

This study evaluates the patient radiation dose from the two-phase protocols of two different computed tomography (CT) systems and compares this with that delivered by the other similar protocols previously published. Two hundred and fourteen patients with primary hyperparathyroidism were included in the study with a two-phase CT scan between 2008 and 2020 by using a Toshiba Aquilion Prime 80 and a GE Light Speed 16. The standard 'neck' or a modified 'parathyroid' protocol was used. The patient dose was evaluated in terms of volumetric computed tomography dose index (CTDIvol), dose length product (DLP) and effective dose (ED) per acquisition protocol and CT system. CTDIvol and DLP were recorded retrospectively, while the ED was calculated based on DLP and an appropriate conversion coefficient. Comparisons of patient dose between the two protocols and two CT systems and the corresponding published values were established. A significantly lower patient dose (40.2-43.2%) than the GE system (p<0.0001) resulted from the Toshiba system. The 'parathyroid' protocol resulted in a 6.5-9.6% lower patient dose than the standard 'neck' protocol. Compared with the literature, the lowest ED value (3.6mSv) was observed since this protocol consists of a lowered tube voltage of 100 kVp, a reduced scan length for the pre-contrast phase and implementation of an iterative reconstruction algorithm.