Split-Bolus Portal Venous Phase Dual-Energy CT Urography: Protocol Design, Image Quality, and Dose Reduction.
OBJECTIVE
The purpose of this study is to evaluate the image quality of split-bolus portal venous phase urography and the potential reduction of radiation dose by using a second-generation dual-source dual-energy CT (DECT) scanner.


METHODS
DECT urography was performed in 84 patients. Unenhanced CT was performed 20 minutes after drinking 800 mL of water. The split-bolus protocol consisted of a sequence of injections, as follows: 200 mL of normal saline (2.0 mL/s), 50 mL of contrast medium (2.5 mL/s) at 0 second, 70 mL of contrast medium (2.5 mL/s) at 360 seconds, and a saline flush of 25 mL. The scan was started at 420 seconds. Virtual unenhanced images were reconstructed from contrast-enhanced images. The mean CT density and signal-to-noise ratio (SNR) of the renal parenchyma, vessels, upper urinary tract, normal reference tissues, and tumors were measured for image quantitative analysis. Image quality and opacification of the collecting systems were rated by two radiologists using 3- or 4-point scales.


RESULTS
The SNR of all measured sites, except the renal pelvis, showed a statistically significant correlation (p < 0.001) between the true unenhanced and virtual unenhanced images. The overall sensitivity of stone detection was 87.5% (28/32) in virtual unenhanced images. Image quality of the renal parenchyma, arteries, and veins was excellent in 59.5%, 75.0%, and 97.6% of cases, respectively. Opacification of the intrarenal collecting systems, proximal, middle, and distal ureters, and bladder was complete in 92.9%, 83.9%, 78.6%, 77.4%, and 26.2% of patients, respectively. Omitting the unenhanced scan can reduce the mean radiation dose from 15.6 to 6.7 mSv.


CONCLUSIONS
Portal venous phase split-bolus DECT urography provides sufficient image quality with potential to reduce radiation exposure.
1 Graduate Institute of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan.|2 Department of Radiology, Faculty of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan.|3 Department of Medical Imaging, Kaohsiung Medical University Hospital, 100 Tz You First Rd, Kaohsiung 807, Taiwan.
Chiao-Yun
CY
Chen
1 Graduate Institute of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan.|3 Department of Medical Imaging, Kaohsiung Medical University Hospital, 100 Tz You First Rd, Kaohsiung 807, Taiwan.
Jui-Sheng
JS
Hsu
2 Department of Radiology, Faculty of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan.|3 Department of Medical Imaging, Kaohsiung Medical University Hospital, 100 Tz You First Rd, Kaohsiung 807, Taiwan.
Twei-Shiun
TS
Jaw
2 Department of Radiology, Faculty of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan.|4 Department of Medical Imaging, Kaohsiung Municipal Hsiao-Kang Hospital, Kaohsiung, Taiwan.
Ming-Chen Paul
MC
Shih
3 Department of Medical Imaging, Kaohsiung Medical University Hospital, 100 Tz You First Rd, Kaohsiung 807, Taiwan.
Lo-Jeh
LJ
Lee
3 Department of Medical Imaging, Kaohsiung Medical University Hospital, 100 Tz You First Rd, Kaohsiung 807, Taiwan.
Tzu-Hsueh
TH
Tsai
1 Graduate Institute of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan.|2 Department of Radiology, Faculty of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan.|3 Department of Medical Imaging, Kaohsiung Medical University Hospital, 100 Tz You First Rd, Kaohsiung 807, Taiwan.
Gin-Chung
GC
Liu
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003287:Contrast Media / Q000008:administration & dosage; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011169:Portal Vein; D011829:Radiation Dosage; D011835:Radiation Protection / Q000379:methods*; D011857:Radiographic Image Interpretation, Computer-Assisted; D015900:Radiography, Dual-Energy Scanned Projection / Q000379:methods*; D012189:Retrospective Studies; D059629:Signal-To-Noise Ratio; D014057:Tomography, X-Ray Computed / Q000379:methods*; D014567:Urography
D003287:Contrast Media
CT urography; abdomen; dual-energy CT; portal venous phase; radiation dose; urolithiasis; virtual unenhanced imaging