A review of patients' doses in computed tomography and traditional urogram : a reflection of current practice

Abstract

Purpose: Traditional Urogram (IVU) and CT Urogram (CTU) are the common radiological examinations for the urinary system. However, with the advent of CT technology recently, the role of IVU is diminishing and being replaced by CTU as it shows better pathological delineation. Although the procedures for CTU are less time-consuming, there is one drawback that CTU deliver more effective dose to patients. Therefore, the objectives of the study are the followings: 1. To compare dose difference of Traditional Urogram and CTU across different hospital in clinical situation. 2. To compare our result with international studies and to look for any large dose difference with Asian subject. 3. To make suggestion on reducing CTU dose and standardizing Protocol.

Materials and Method: The dose data were collected retrospectively with Asian as the subject group. 15 IVU cases were performed in Hospital A with AGFA D-600 system and DAP were collected through the system. CTU were performed in Hospital A and B with four scanners (2 GE VCT64, 1 Toshiba Aquillion and 1 Toshiba Aquillion Prime) of different protocols. DLP of 20 cases from each scanner were collected through the console retrospectively. The DAP and DLP data were then converted to effective dose by applying a conversion factor k (0.18 for IVU and 0.015 for CTU). The estimated effective dose data was then used for comparison and correlate with AP thickness of patients.

Result: The estimated effective dose for IVU is 19.2 ± 7.1 mSv. For CTU, the estimated effective dose for CT 1 is 17.0 ± 8.7 mSv, CT 2 is 25.8 ± 9.2 mSv, CT 3 is 27.3 ± 6.2 mSv and for CT 4 is 17.5 ± 8.5 mSv. The dose to patients by IVU and CTU is comparable for CT 1 and CT 4. The doses among scanners are varied. CT 1, 2 and 4 show positive correlations between effective dose and AP thickness of patients. CT 3 has the least intra-scanner dose variation among the scanners. However, when compared to past studies, the dose for IVU has been increased while CTU remains similar. Although Asian was thought to be smaller in size, the dose does not have significance difference with Western.

Conclusion: This study draws our attention to the practice of Urograms. It shows that dose for IVU have been increased for some reasons and dose difference of CTU between scanners is present. We recommend that standardization of protocol is needed and thus dose can be more efficient by suggested method. This project arise the need of reflection on current practice on Urograms by the society.