To evaluate the best collimation used in wide volume (WV) mode to cover the abdomen in computed tomography (CT) urography in terms of radiation dose and image quality.

This study was performed on a 320×0.5mm detector row CT unit. The first part identified the lowest volume CT dose index (CTDIvol) by using the topograms data of 25 medium size patients (13 men and 12 women; mean age: 52±9 [SD] years; age range: 46–68 years) using different collimations on WV from 6cm to 16cm and the one of the helical mode for the same coverage length. The second part consisted of a clinical evaluation of this result including 45 medium size patients (32 men and 13 women; mean age: 68±14 [SD] years; age range: 45–72 years). The qualitative evaluation included several items based on a 5-point Likert scale.

The first part of the study indicated that a collimation of 10cm (200×0.5mm) in WV mode with 5 volumes had the lowest CTDIvol (2.78±0.35mGy; range: 2.35–3.21mGy) compared to helical mode (4.38±0.48mGy, range: 3.75–4.95mGy). In the second part, the mean radiation dose reduction by comparison with helical mode was 44.03%±0.36% (P<0.001) and 51.16%±1.22% (P<0.005) for CTDIvol and DLP, respectively.

Wide volume mode of the abdomen can be performed with a significant radiation dose reduction with a collimation of 10cm (200×0.5mm) and five volumes.