Combined magnetic resonance urography and targeted helical CT in patients with renal colic: a new approach to reduce delivered dose.
OBJECTIVE
To determine whether magnetic resonance urography (MRU), obtained before helical computed tomography (CT) in patients with acute renal colic, can help delimit the obstructed area to be subsequently examined by a targeted CT scan, thus reducing the dose of radiation.


METHODS
Patients (51) with symptoms of acute renal colic underwent MRU and a total urinary tract helical CT. CT images from the 5 cm below the level of ureteral obstruction as demonstrated by MRU were selected out. Combined interpretation of MRU and selected CT images constituted protocol A. Protocol B consisted of the entire unenhanced helical CT of the urinary tract. The two protocols were compared regarding the following points: 1) sensitivity in diagnosing the presence of obstructing urinary stones, and 2) the delivered radiation dose.


RESULTS
Protocol A and protocol B had, respectively, 98% and 100% sensitivity in demonstrating ureteral stone as a cause of renal colic. Estimated average dose calculated from phantom study was 0.52 mSv for protocol A and 2.83 mSv for protocol B. Therefore, the effective radiation dose was 5.4 times lower in protocol A compared to protocol B.


CONCLUSIONS
Combined MRU and short helical CT has a high sensitivity in detecting ureteral calculi with a reduced radiation dose.
Department of Radiologic Sciences, University of Messina, Policlinico G. Martino, Contrada Gazzi, Messina 98125, Italy.
Alfredo
A
Blandino
Fabio
F
Minutoli
Emanuele
E
Scribano
Sergio
S
Vinci
Carlo
C
Magno
Stefano
S
Pergolizzi
Nicola
N
Settineri
Ignazio
I
Pandolfo
Michele
M
Gaeta
D000293:Adolescent; D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D007669:Kidney Calculi / Q000175:diagnosis* / Q000000981:diagnostic imaging; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011829:Radiation Dosage; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed; D014567:Urography / Q000379:methods*