The Added Value of Virtual Unenhanced Images Obtained From Dual-energy CT Urography in the Detection and Measurement of Urinary Stone



      To evaluate the detection and quantification of urinary stones using virtual unenhanced images (VUE) at different phases and slice thickness in contrast-enhanced dual-energy CT Urography (DECTU) in comparison with true unenhanced images (TUE).


      One hundred and twelve urinary stone patients who required triphasic DECTU were analyzed. Data were reconstructed as the followings: TUE images with 1.25 mm thickness (TUE portal venous phase VUE images with 1.25 and 5-mm thickness (VUE(VP)_1.25 mm and VUE(VP)_5 mm) and excretory phase VUE images with 1.25 and 5-mm thickness (VUE(EP)_1.25mm and VUE(EP)_5mm). The. The stones were divided into large (≥5 mm) and small stones. The detection rate, size and CT value of stones were assessed by 2 radiologists and statistically compared among the above groups.


      Two hundred and thirty urinary stones (163 large and 67 small stones) were detected on TUE_1.25 mm images. For large stones, the detection rate on VUE(VP)_1.25 mm, VUE(VP)_5 mm, VUE(EP)_1.25 mm and VUE(EP)_5 mm was 100%, 96.9%, 85.9%, and 80.4%; while for small stones, the rate was 77.6%, 37.3%, 46.3%, and 23.9%, respectively. VUE(VP) images significantly improved the stone detection rate compared with VUE(EP) images at both slice thicknesses. In general, VUE images identified stones with smaller sizes and lower Hounsfield units, but thinner slice thickness images reduced the inaccuracy. Inter-reader agreement of the stone detection revealed a k value range from 0.85 to 0.94 for TUE and VUE images.


      Large stones (≥5 mm) can reliably be detected on thin section VUE(VP) images with 33% radiation dose reduction. However, for small stones TUE remains superior. Stone size is underestimated on VUE images.
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        • Joffe SA
        • Servaes S
        • Okon S
        • Horowitz M.
        Multi-detector row CT urography in the evaluation of hematuria.
        Radiographics. 2003; 23: 1441-1456
        • Kawashima A
        • Vrtiska TJ
        • LeRoy AJ
        • Hartman RP
        • McCollough CH
        • King Jr., BF
        CT urography.
        Radiographics. 2004; 24: 35-58
        • Silverman SG
        • Leyendecker JR
        • Amis Jr., ES
        What is the current role of CT urography and MR urography in the evaluation of the urinary tract?.
        Radiology. 2009; 250: 309-323
        • Raman SP
        • Horton KM
        • Fishman EK.
        MDCT evaluation of ureteral tumors: advantages of 3D reconstruction and volume visualization.
        AJR Am J Roentgenol. 2013; 201: 1239-1247
        • Sudakoff GS
        • Guralnick M
        • Langenstroer P
        • et al.
        CT urography of urinary diversions with enhanced CT digital radiography: preliminary experience.
        AJR Am J Roentgenol. 2005; 184: 131-138
        • Potenta SE
        • D'Agostino R
        • Sternberg KM
        • Tatsumi K
        • Perusse K
        CT urography for evaluation of the ureter.
        Radiographics. 2015; 35: 709-726
        • Van Der Molen AJ
        • Cowan NC
        • Mueller-Lisse UG
        • et al.
        CT urography: definition, indications and techniques. A guideline for clinical practice.
        Eur Radiol. 2008; 18: 4-17
        • Karçaaltıncaba M
        • Aktaş A.
        Dual-energy CT revisited with multidetector CT: review of principles and clinical applications.
        Diagn Interv Radiol. 2011; 17: 181-194
        • McCollough CH
        • Leng S
        • Yu L
        • Fletcher JG.
        Dual- and multi-energy CT: principles, technical approaches, and clinical applications.
        Radiology. 2015; 276: 637-653
        • Scheffel H
        • Stolzmann P
        • Frauenfelder T
        • et al.
        Dual-energy contrast-enhanced computed tomography for the detection of urinary stone disease.
        Invest Radiol. 2007; 42: 823-829
        • Takahashi N
        • Hartman RP
        • Vrtiska TJ
        • et al.
        Dual-energy CT iodine-subtraction virtual unenhanced technique to detect urinary stones in an iodine-filled collecting system: a phantom study.
        AJR Am J Roentgenol. 2008; 190: 1169-1173
        • Takahashi N
        • Vrtiska TJ
        • Kawashima A
        • et al.
        Detectability of urinary stones on virtual nonenhanced images generated at pyelographic-phase dual-energy CT.
        Radiology. 2010; 256: 184-190
        • Wang J
        • Qu M
        • Duan X
        • et al.
        Characterisation of urinary stones in the presence of iodinated contrast medium using dual-energy CT: a phantom study.
        Eur Radiol. 2012; 22: 2589-2596
        • Moon JW
        • Park BK
        • Kim CK
        • Park SY.
        Evaluation of virtual unenhanced CT obtained from dual-energy CT urography for detecting urinary stones.
        Br J Radiol. 2012; 85: e176-e181
        • Mangold S
        • Thomas C
        • Fenchel M
        • et al.
        Virtual nonenhanced dual-energy CT urography with tin-filter technology: determinants of detection of urinary calculi in the renal collecting system.
        Radiology. 2012; 264: 119-125
        • Gücük A
        • Uyetürk U
        • Oztürk U
        • Kemahli E
        • Yildiz M
        • Metin A.
        Does the Hounsfield unit value determined by computed tomography predict the outcome of percutaneous nephrolithotomy?.
        J Endourol. 2012; 26: 792-796
        • Gallioli A
        • De Lorenzis E
        • Boeri L
        • et al.
        Clinical utility of computed tomography Hounsfield characterization for percutaneous nephrolithotomy: a cross-sectional study.
        BMC Urol. 2017; 17: 104
      1. American Association of Physicists in Medicine. The measurement, reporting, and management of radiation dose in CT. 2008.

        • Botsikas D
        • Hansen C
        • Stefanelli S
        • Becker CD
        • Montet X.
        Urinary stone detection and characterisation with dual-energy CT urography after furosemide intravenous injection: preliminary results.
        Eur Radiol. 2014; 24: 709-714
        • Toepker M
        • Kuehas F
        • Kienzl D
        • et al.
        Dual energy computerized tomography with a split bolus-a 1-stop shop for patients with suspected urinary stones?.
        J Urol. 2014; 191: 792-797
        • Segura JW
        • Preminger GM
        • Assimos DG
        • et al.
        Ureteral stones clinical guidelines panel summary report on the management of ureteral calculi. The American Urological Association.
        J Urol. 1997; 158: 1915-1921
        • Graser A
        • Johnson TR
        • Hecht EM
        • et al.
        Dual-energy CT in patients suspected of having renal masses: can virtual nonenhanced images replace true nonenhanced images?.
        Radiology. 2009; 252: 433-440
        • Zhang LJ
        • Peng J
        • Wu SY
        • et al.
        Liver virtual non-enhanced CT with dual-source, dual-energy CT: a preliminary study.
        Eur Radiol. 2010; 20: 2257-2264
        • Kaufmann S
        • Sauter A
        • Spira D
        • et al.
        Tin-filter enhanced dual-energy-CT: image quality and accuracy of CT values in virtual noncontrast imaging.
        Acad Radiol. 2013; 20: 596-603
        • De Cecco CN
        • Muscogiuri G
        • Schoepf UJ
        • et al.
        Virtual unenhanced imaging of the liver with third-generation dual-source dual-energy CT and advanced modeled iterative reconstruction.
        Eur J Radiol. 2016; 85: 1257-1264
        • Sahni VA
        • Shinagare AB
        • Silverman SG.
        Virtual unenhanced CT images acquired from dual-energy CT urography: accuracy of attenuation values and variation with contrast material phase.
        Clin Radiol. 2013; 68: 264-271
        • Yamada Y
        • Jinzaki M
        • Hosokawa T
        • Tanami Y
        • Abe T
        • Kuribayashi S.
        Abdominal CT: an intra-individual comparison between virtual monochromatic spectral and polychromatic 120-kVp images obtained during the same examination.
        Eur J Radiol. 2014; 83: 1715-1722
        • Chai Y
        • Xing J
        • Gao J
        • et al.
        Feasibility of virtual nonenhanced images derived from single-source fast kVp-switching dual-energy CT in evaluating gastric tumors.
        Eur J Radiol. 2016; 85: 366-372
        • Li Y
        • Li Y
        • Jackson A
        • et al.
        Comparison of virtual unenhanced CT images of the abdomen under different iodine flow rates.
        Abdom Radiol (NY). 2017; 42: 312-321