Body CT examinations in oncologic patients: the impact of subspecialty radiology on radiation exposure in the clinical practice. A quality care study

Abstract

Purposes: The primary objective of this retrospective study was to assess whether the CT dose delivered to oncologic patients was different in a subspecialty radiology department, compared to a general radiology department. The secondary explorative objective was to assess whether the objective image quality of CT examinations was different in the two settings.

Materials and methods: Chest and abdomen CT scans performed for oncologic indications were selected from a general radiology department and a subspecialty radiology department. By using a radiation dose management platform, we extracted and compared CT dose index (CTDI_vol) and dose length product (DLP) both for each phase and for the entire CT exams. For objective image quality evaluation, we calculated the signal-to-noise ratio (SNR) and the contrast-to-noise ratio (CNR) at the level of the liver and of the aorta. A P-value < 0.05 was considered significant.

Results: A total of 7098 CT examinations were included. CTDI_vol was evaluated in 12,804 phases; DLP in 10,713 phases and in 6714 examinations. The CTDI_vol and DLP overall were significantly lower in the subspecialty radiology department compared to the general radiology department CTDI median (IQR) 5.19 (3.91-7.00) and 5.51 (4.17-7.72), DLP median and IQR of 490.0 (342.4-710.6) and 503.4 (359.9-728.8), p < 0.001 and p = 0.01, respectively. The objective image quality showed no significant difference in the general and subspecialty radiology departments, with median and IQR of 4.03 (2.82-5.51) and 3.84 (3.09-4.94) for SNR_Liv (p = 0.58); 4.81 (2.70-7.62) and 4.34 (3.05-6.25) for SNR_Ao (p = 0.30); 0.83 (0.20-1.89) and 1.00 (0.35-1.57) for CNR_Liv (p = 0.99); 2.23 (0.09-3.83) and 1.01 (0.15-2.84) for CNR_Ao (p = 0.24) with SNR_Liv (p = 0.58), SNR_Ao (p = 0.30), CNR_Liv (p = 0.99) and CNR_Ao (p = 0.24).

Conclusion: In a subspecialty radiology department, CT protocols are optimized compared to a general radiology department leading to lower doses to oncologic patients without significant objective image quality degradation.

Keywords: CT dose index; Dose length product; Objective image quality; Oncology; Radiology subspecialty.