Christoph Karl Thomas MD, Presenter: Nothing to Disclose

David Schilling, Abstract Co-Author: Nothing to Disclose

Ilias Tsiflikas MD, Abstract Co-Author: Nothing to Disclose

Martin Heuschmid MD, Abstract Co-Author: Nothing to Disclose

Claus Detlef Claussen MD, Abstract Co-Author: Nothing to Disclose

Heinz-Peter Wilhelm Schlemmer MD, PhD, Abstract Co-Author: Nothing to Disclose

Dominik Ketelsen MD, Abstract Co-Author: Nothing to Disclose

Anja Judith Reimann MD, Abstract Co-Author: Nothing to Disclose

00030490-DMT et al, Abstract Co-Author: Nothing to Disclose

To evaluate the performance of a low dose dual energy CT (DECT) protocol for the evaluation of urinary calculus disease.

A low dose DECT protocol (Dual source CT system, Somatom Definition, Siemens, Forchheim, Germany; 140 kV and 80 kV, effective reference mAs 23 mAs and 105 mAs) was used in our institution for six months for the assessment of urinary calculi disease. 60 unselected patients with known or suspected calculi were examined. Commercially available postprocessing software (syngo, Siemens) was used to grade the calculi in calcified, cystine and uric acid stones. Additionally, the dual energy ratio (DE ratio = HU80 kV/HU140 kV) was assessed using a density-based individual threshold method (MATLAB, The MathWorks, Natick, MA). Diameters of the calculi were measured. Whenever clinically indicated, the calculi were removed by ureterorenoscopy and analyzed using infrared spectroscopy. Dose indicators were recorded in all patients and compared to typical exposure in intravenous pyelography (IVP).

All examinations were performed successfully. Urinary calculi were detected in 44 patients. Calculi ranged between 2 and 17 mm in size. In 32 patients, calculi were removed and analyzed. 15 calcium-monooxalate calculi, 3 carbonatapatite calculi, 7 mixed calcified calculi, 4 uric acid calculi and 3 cystine calculi were identified using infrared spectroscopy. Calculated DE ratios ranged from 1.32 to 1.58 for calcified calculi, from 1.34 to 1.37 for cystine and from 1.09 to 1.13 for uric acid calculi. Although there was an overlap between the measured DE ratios, the postprocessing software was able to correctly classify all calcified, cystine and uric acid stones. A mean volume computed tomography dose index of 3.8 mGy (range 2.3 to 6.9 mGy) and a mean dose length product of 152 mGy*cm (range 70 to 285 mGy*cm) were applied, leading to a calculated mean effective dose of 2.7 mSv (range 1.3 to 5.1 mSv). The typical mean exposure of IVP was estimated around 2.5 mSv in the literature.  

Unenhanced low dose DECT in urinary calculus disease allows a reliable differentiation of calcified, cystine and uric acid calculi at a radiation dose comparable to IVP.

A technique for non-invasive differentiation of urinary calculi could be useful for the selection of the optimal treatment path (ESWL vs. extraction vs. medical solution) in urinary calculus disease.

Thomas, C, Schilling, D, Tsiflikas, I, Heuschmid, M, Claussen, C, Schlemmer, H, Ketelsen, D, Reimann, A, et al, 0, Dual-Energy CT Can Differentiate Urinary Calculi at a Radiation Dose Comparable to Intravenous Pyelography.  Radiological Society of North America 2009 Scientific Assembly and Annual Meeting, November 29 - December 4, 2009 ,Chicago IL. http://archive.rsna.org/2009/8012735.html