Abstract

Introduction:A retrospective review of patients who underwent preoperative Computed Tomographic Angiography (CTA) prior to living laparoscopic renal donation was performed. Image quality and accuracy were compared at 120 and 100 kVp tube energies with respect to quantitative image parameters and prediction of surgical findings. Material and methods:A total of 193 patients were reviewed, all of whom underwent laparoscopic donor nephrectomy with preceding CTA evaluation over a 5.5 year period. Eighty-four patients had CTA performed at 120 kVp and 109 at 100 kVp. Images were evaluated using several quantitative parameters, including mean aortic contrast attenuation, noise level, and calculated signal-to-noise (SNR) and contrast-to-noise (CNR) ratios. Comparison was made between accuracy in predicting surgical findings between the two groups. Dosimetry was also compared using the volume CT dose index (CTDIvol). Results:All CTA evaluations were diagnostically acceptable regardless of tube energy. Mean post-contrast attenuation values were greater in both the aorta and the renal arteries at 100 versus 120 kVp (357.4 and 327.2 versus 270.8 and 239.6 HU), respectively. Correspondingly increased mean noise was also noted: 34.2 versus 24.3 HU, respectively. Both SNR and CNR were slightly increased at lower tube energy but without statistical significance. Per-patient accuracy in predicting surgical vascular anatomy was similar at both energies, 96%. There was a mean CTDIvol reduction of 44.5% at lower tube energy. Conclusion:Decreasing tube energy from 120 to 100 kVp is a consistently viable method of accurately predicting surgical anatomy at donor nephrectomy with improved vascular enhancement and significant dose reduction.

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