Toepker M et al, 2014: Dual Energy Computerized Tomography with a Split Bolus: A 1-Stop Shop for Patients with Suspected Urinary Stones?
Toepker M, Kuehas F, Kienzl D, Herwig R, Spazierer E, Krauss B, Weber M, Seitz C, Ringl H
Department of Radiology, Medical University Vienna, Vienna General Hospital, Vienna, Austria
Department of Urology, Medical University Vienna, Vienna General Hospital, Vienna, Austria
Healthcare Sector, Siemens AG, Forchheim, Germany
Abstract
PURPOSE: We evaluated a dual energy, split bolus computerized tomography protocol that provides virtual noncontrast, parenchymal and urographic phases in a single scan. We assessed the sensitivity of the virtual noncontrast phase using this protocol to detect urinary stones compared to the gold standard of the true noncontrast phase.
MATERIALS AND METHODS: We prospectively enrolled in the study 81 patients who underwent unenhanced single energy computerized tomography at 120 kV/200 mA as well as contrast enhanced dual energy computerized tomography on a Somatom® Definition Flash-CT (tube A 80 kV/233 mA and tube B SN 140 kV/180 mA with 1/0.8 mm slice thickness). For the split bolus protocol 400 mg/ml Iomeron® were injected at 2 time points, that is 15 ml 10 minutes before the scan and 80 ml 65 seconds before the scan. In a consensus reading 2 readers evaluated the presence and diameter of stones on the true and virtual noncontrast phases.
RESULTS: Of the 350 stones noted on the true noncontrast phase we found 289 on the virtual noncontrast phase as well as 13 false-positive and 66 false-negative stones. Sensitivity was 98.4%, 89.8% and 82.6% per patient, segment and stone, respectively. The diameter measured on the virtual noncontrast phase corresponded to a mean ± SD 92.5% ± 31.6% of the diameter on the true noncontrast phase. The mean effective dose was 4.8 ± 1.8 and 10.5 ± 3.7 mSv for the true and virtual noncontrast phases, respectively.
CONCLUSIONS: The proposed protocol allows for combining 3 phases in a single scan while still enabling the detection of urinary stones at high sensitivity. This technique halves the radiation dose and provides the surgeon with better anatomical information on the calyceal system. Therefore, it is a valuable diagnostic tool for kidney stone treatment planning and follow up.
J Urol. 2014 Mar;191(3):792-7. doi: 10.1016/j.juro.2013.10.057. Epub 2013 Oct 17.
PMID:24140845[PubMed - in process]
Comments 1
This article is not directly related to SWL, but describes an important improvement of the radiological examination. Although most stones can be accurately diagnosed by non-contrast CT, there are situations when more details of the anatomy of the renal collecting system and the stone situation are desirable. If contrast medium is injected before the CT scan the stones might be obscured. If two successive CT scans are carried out, one without and one with contrast medium, the radiation dose will be higher than desirable. In the method described in this article the authors used dual-energy CT with a split bolus. This means that two doses of contrast medium were injected before the scanning. In that way it was possible to get three different phases from one single scanning procedure. The characteristics of the stone(s) were shown by contrast subtraction. This method might be a useful alternative in order to get more information out of fewer CT-examinations with reduced radiation.
Hans-Göran Tiselius