Radiation dose reduction at multidetector CT with adaptive statistical iterative reconstruction for evaluation of urolithiasis: how low can we go?

PURPOSE To evaluate the performance of computed tomographic (CT) examinations at 80 and 100 kV with tube current-time products of 75-150 mA and the effect of adaptive statistical iterative reconstruction (ASIR) on CT image quality in patients with urinary stone disease. MATERIALS AND METHODS In this HIPAA-compliant institutional review board-approved study, verbal consent for prospective low-dose CT and waivers of consent for retrospective review of CT scans were obtained. Between November 2010 and April 2011, 25 patients (15 men, 10 women; mean age, 35 years) with urolithiasis underwent 64-section multidetector CT with 75-150 mA and noise index of 30. Modified protocol was based on body weight (<200 lb [90 kg], 80 kV; >200 lb [90 kg], 100 kV). Images of 5-mm section thickness were reconstructed with filtered back projection (FBP) and 60% and 80% ASIR techniques, with 3-mm coronal and sagittal reformations. Two readers independently reviewed FBP and ASIR data sets for image quality (scale, 1-5), noise (scale , 1-3), and calculi (number, size, location). Confidence levels for urolithiaisis and alternate diagnoses were rated (scale, 1-3). In 13 patients, FBP CT images acquired with the reference standard departmental protocol were available for comparison. Radiation dose was compared between imaging series. Statistical analysis was performed with Wilcoxon signed rank and paired t tests. RESULTS Modified-protocol FBP images showed low image quality (score, 2.5), with improvement on modified-protocol ASIR images (score, 3.4) (P=.03). All 33 stones (mean diameter, 6.1 mm; range, 2-28 mm) at modified-protocol CT were diagnosed by both readers. In 20 of 25 patients (80%), ASIR images were rated adequate for rendering other diagnoses in the abdomen (score, 2.0), as opposed to FBP images (score, 1.3). Mean radiation dose for modified-protocol CT was 1.8 mGy (1.3 mGy for patients<200 lb; 2.3 mGy for patients>200 lb) in comparison with 9.9 mGy for reference-protocol CT (P=.001). CONCLUSION Image quality improvements with ASIR at reduced radiation dose of 1.8 mGy enabled effective evaluation of urinary calculi without substantially affecting diagnostic confidence. © RSNA, 2012.

[1]  J R Fielding,et al.  Unenhanced helical CT of ureteral stones: a replacement for excretory urography in planning treatment. , 1998, AJR. American journal of roentgenology.

[2]  J. Teichman.  Acute Renal Colic from Ureteral Calculus , 2004 .

[3]  F. G. Sommer,et al.  Unenhanced helical CT for suspected renal colic. , 1999, AJR. American journal of roentgenology.

[4]  Epidemiology of stone disease. , 2007, The Urologic clinics of North America.

[5]  R C Smith,et al.  The value of unenhanced helical computerized tomography in the management of acute flank pain. , 1998, The Journal of urology.

[6]  Alvin C. Silva,et al.  Innovations in CT dose reduction strategy: application of the adaptive statistical iterative reconstruction algorithm. , 2010, AJR. American journal of roentgenology.

[7]  B. Finlayson,et al.  The frequency of urolithiasis in hospital discharge diagnoses in the United States. , 1978, Investigative urology.

[8]  R C Smith,et al.  Acute flank pain: comparison of non-contrast-enhanced CT and intravenous urography. , 1995, Radiology.

[9]  D. Katz,et al.  Alternative or additional diagnoses on unenhanced helical computed tomography for suspected renal colic: experience with 1000 consecutive examinations. , 2000, Urology.

[10]  F. G. Sommer,et al.  Unenhanced helical CT of ureteral stones: incidence of associated urinary tract findings. , 1996, AJR. American journal of roentgenology.

[11]  Naveen M. Kulkarni,et al.  Low-dose MDCT and CT enterography of patients with Crohn disease: feasibility of adaptive statistical iterative reconstruction. , 2011, AJR. American journal of roentgenology.

[12]  Rebecca S Lewis,et al.  Projected cancer risks from computed tomographic scans performed in the United States in 2007. , 2009, Archives of internal medicine.

[13]  G. Preminger,et al.  Unenhanced helical computerized tomography for the evaluation of patients with acute flank pain. , 1998, The Journal of urology.

[14]  D. Sahani,et al.  Computerized tomography magnified bone windows are superior to standard soft tissue windows for accurate measurement of stone size: an in vitro and clinical study. , 2009, The Journal of urology.

[15]  W D Foley,et al.  Ureteral calculi: diagnostic efficacy of helical CT and implications for treatment of patients. , 1999, AJR. American journal of roentgenology.

[16]  D. Sahani,et al.  Reducing Abdominal CT Radiation Dose With Adaptive Statistical Iterative Reconstruction Technique , 2010, Investigative radiology.

[17]  S. Yilmaz,et al.  Renal colic: comparison of spiral CT, US and IVU in the detection of ureteral calculi , 1999, European Radiology.

[18]  T. Meagher,et al.  Low dose computed tomography in suspected acute renal colic. , 2001, Clinical radiology.

[19]  K. Bohndorf,et al.  [CT in ureterolithiasis with a radiation dose equal to intravenous urography: results in 209 patients]. , 2003, RoFo : Fortschritte auf dem Gebiete der Rontgenstrahlen und der Nuklearmedizin.

[20]  D. Brenner,et al.  Computed tomography--an increasing source of radiation exposure. , 2007, The New England journal of medicine.

[21]  A. Sodickson,et al.  Recurrent CT, cumulative radiation exposure, and associated radiation-induced cancer risks from CT of adults. , 2009, Radiology.

[22]  E Godehardt,et al.  [Dose reduction and image quality in MDCT of the upper abdomen: potential of an adaptive post-processing filter]. , 2010, RoFo : Fortschritte auf dem Gebiete der Rontgenstrahlen und der Nuklearmedizin.

[23]  N. Mondaini,et al.  Epidemiology and Risk Factors in Urolithiasis , 2007, Urologia Internationalis.

[24]  Patrik Rogalla,et al.  Does Ultra-Low-Dose CT With a Radiation Dose Equivalent to That of KUB Suffice to Detect Renal and Ureteral Calculi? , 2006, Journal of computer assisted tomography.

[25]  M. Taupitz,et al.  Ultra-Niedrigdosis-CT zur Steinsuche in Nieren und ableitenden Harnwegen , 2004 .

[26]  D. Miglioretti,et al.  Radiation dose associated with common computed tomography examinations and the associated lifetime attributable risk of cancer. , 2009, Archives of internal medicine.

[27]  G. Stevenson,et al.  Low-dose nonenhanced helical CT of renal colic: assessment of ureteric stone detection and measurement of effective dose equivalent. , 2000, Radiology.

[28]  Alvin C. Silva,et al.  Iterative Reconstruction Technique for Reducing Body Radiation Dose at Ct: Feasibility Study Hara Et Al. Ct Iterative Reconstruction Technique Gastrointestinal Imaging Original Research , 2022 .

[29]  S. Park,et al.  A prospective comparison of standard-dose CT enterography and 50% reduced-dose CT enterography with and without noise reduction for evaluating Crohn disease. , 2011, AJR. American journal of roentgenology.