Diagnostic reference level quantities for adult chest and abdomen-pelvis CT examinations: correlation with organ doses

Abstract

Objectives: To evaluate correlations between DRL quantities (DRLq) stratified into patient size groups for non-contrast chest and abdomen-pelvis CT examinations in adult patients and the corresponding organ doses.

Methods: This study presents correlations between DRLq (CTDI_vol, DLP and SSDE) stratified into patient size ranges and corresponding organ doses shared in four groups: inside, peripheral, distributed and outside. The demographic, technical and dosimetric parameters were used to identify the influence of these quantities in organ doses. A robust statistical method was implemented in order to establish these correlations and its statistical significance.

Results: Median values of the grouped organ doses are presented according to the effective diameter ranges. Organ doses in the regions inside the imaged area are higher than the organ doses in peripheral, distributed and outside regions, excepted to the peripheral doses associated with chest examinations. Different levels of statistical significance between organ doses and the DRLq were presented.

Conclusions: Correlations between DRLq and target-organ doses associated with clinical practice can support guidance's to the establishment of optimization criteria. SSDE demonstrated to be significant in the evaluation of organ doses is also highlighted. The proposed model allows the design of optimization actions with specific risk-reduction results.

Keywords: Abdomen-pelvis; Chest; Computed tomography; Organ doses; Statistics.

Fig. 1

Box-plots representing the distributions of the organ dose groups: a IO, b PO, c DO and d OO, according to the effective diameter group ranges for abdomen-pelvis examinations

Fig. 2

Box-plots representing the distributions of the organ dose groups: a IO, b PO, c DO and d OO, according to the effective diameter group ranges for chest examinations

Fig. 3

Abdomen-pelvis organ dose groups as functions of the SSDE ((a) Inside, (c) Periphery, (e) Outside and (g) Distributed) and d  ((b) Inside, (d) Periphery, (f) Outside and (h) Distributed). The magenta lines correspond to the fittings using Eq. (2) considering the contributions of patients imaged in all CT scanners. The blue band refers to a range of ± 20% around this average line. The dots identify each CT scanner used in the study

Fig. 4

Chest organ dose groups as functions of the SSDE ((a) Inside, (c) Periphery, (e) Outside and (g) Distributed) and d ((b) Inside, (d) Periphery, (f) Outside and (h) Distributed). The magenta lines correspond to the fittings using Eq. 2 considering the contributions of patients imaged in all CT scanners. The blue band refers to a range of ± 20% around this average line. The dots identify each CT scanner used in the study