Absorbed dose, effective dose and lifetime attributable risk of breast and thyroid cancers in coronary CT angiography: A comparison between 64 and 128 slice CT scanners

The attentive consideration of absorbed dose impact on the breast, a radiosensitive organ, remains pivotal in coronary computed tomography angiography (CCTA). Additionally, the thyroid is subjected to scatter radiation during this diagnostic procedure. The primary objective of this study was to comprehensively investigate and quantify the absorbed dose, effective dose, and lifetime attributable risks (LARs) associated with breast and thyroid cancers in the context of CCTA. This investigation enrolled a cohort of 180 patients (90 men and 90 women) who underwent CCTA utilizing three distinct CT scanners: the SOMATOM Definition AS 128 slice (Siemens 128), the Lightspeed VCT 64 Slice (GE 64), and the Brilliance 64 Slice (Philips 64). The precise quantification of absorbed doses to the breast and thyroid was achieved through the utilization of a thermoluminescence dosimeter (TLD). LAR for breast and thyroid cancers was evaluated in accordance with the BEIR VII report. Kruskal-Wallis test was employed to compare the means of absorbed doses and LARs. The average absorbed doses to the breast during CCTA with Siemens 128, GE 64, and Philips 64 scanners were 116.32 +/- 39.02, 82.88 +/- 18.33, and 84.11 +/- 15.18 mGy, respectively (P < 0.05). Correspondingly, the average LAR for breast cancer was found to be 84, 68, and 52 cases per 100,000 persons, respectively. Notably, a significant discrepancy in breast cancer LARs was observed among different age groups (P < 0.05). Regarding thyroid doses with Siemens 128, GE 64, and Philips 64 scanners, average values were 11.82 +/- 7.51, 12.20 +/- 10.87, and 14.49 +/- 5.43 mGy, respectively (P > 0.05). Additionally, the average LAR for thyroid cancer was determined as 0.32, 0.56, and 0.22 cases per 100,000 persons, respectively. Across all age groups, the LAR for thyroid cancer exhibited higher values among women compared to men. However, these differences did not achieve statistical significance (P > 0.05), indicating a need for further investigation. The findings prominently indicated high absorbed doses to the breast in CCTA using protocols investigated in this study (with an average of 93.7 +/- 30.26 mGy). Particularly, the LAR for breast cancer was higher among younger women, specifically those aged between 20 and 40 years (249 cases per 100,000). These results underscore the necessity for further justification and optimization of CCTA protocols.