Naoki Takahashi MD, Presenter: In-kind support, ChiRhoClin, Inc

Robert Perry Hartman MD, Abstract Co-Author: Committee member, American Medical Systems Consultant, Siemens AG

Akira Kawashima MD, Abstract Co-Author: Nothing to Disclose

Christian Eusemann PhD, Abstract Co-Author: Employee, Siemens AG

Vanessa A. Zavaletta PhD, Abstract Co-Author: Nothing to Disclose

Alisa Ingrid Walz-Flannigan PhD, Abstract Co-Author: Nothing to Disclose

Anja Apel, Abstract Co-Author: Intern, Siemens AG

Matthew Howe MD, Abstract Co-Author: Nothing to Disclose

Joel Garland Fletcher MD, Abstract Co-Author: Research grant, Siemens AG Grant, E-Z-EM, Inc License agreement, General Electric Company

Cynthia H. McCollough PhD, Abstract Co-Author: Research grant, Siemens AG Research grant, RTI Electronics AB Research grant, Bayer AG

et al, Abstract Co-Author: Nothing to Disclose

In a phantom study, to optimize blending of 80kV and 140kV dual-energy CT (DECT) images to maximize ureteral tumor conspicuity.

Three ureteral phantoms (3, 5, 10mm-diameter-cylindrical rods) each containing 4 acrylic “tumor” (occluding 20%/40%/60%/80% of ureteral diameter; size: 0.7-8.0mm, 120HU at 120kVp). Ureteral phantoms were consecutively filled with iodine solutions (250, 500, and 1,000HU at 120kV) and were placed in 30cm water tank surrounded by two 5-cm oil-gel. The phantoms were scanned using dual-source CT DECT technique with collimation of 1.2mm. Images were reconstructed for both 80kV and 140kV scan data and combined using linear blending (3:7 weighted average of 80kV and 140kV) and non-linear sigmoidal blending, which uses variable mixing ratio determined by the CT attenuation of each pixel; sigmoidal center 150HU, width 200HU). CNR and subjective conspicuity of the lesions were compared between two blending techniques.

CNR values were 1.7, 3.0 and 5.5 using linear blending and 2.3, 3.2 and 6.0 for non-linear blending for urine densities of 250HU, 500HU and 1000HU, respectively. CNR improvement from linear to non-linear blending was highest at 250HU urine attenuation. Lesion conspicuity was higher with non-linear blending in 9/12 lesions at 250HU urine attenuation, whereas the rest of lesions were equally conspicuous.

Non-linear sigmoidal blending improves ureteral lesion conspicuity when urine attenuation is relatively low in a phantom study.

CT urography with DECT non-linear sigmoidal blending may be useful when attenuation of ureter in pyelographic phase is expected to be low (diminished renal function or furosemide is used)

Takahashi, N, Hartman, R, Kawashima, A, Eusemann, C, Zavaletta, V, Walz-Flannigan, A, Apel, A, Howe, M, Fletcher, J, McCollough, C, et al, , Dual-energy CT for the Detection of Tumor in Iodine-filled Ureter: Lesion Conspicuity Using Different Blending Methods in a Phantom Study.  Radiological Society of North America 2008 Scientific Assembly and Annual Meeting, February 18 - February 20, 2008 ,Chicago IL. http://archive.rsna.org/2008/6021141.html