title: Low-dose and standard computed tomography scans yield equivalent stone measurements.
abstract: OBJECTIVE
  To ascertain the reliability of low-dose computed tomography (CT) compared with standard CT in the determination of stone size, density, and skin-to-stone distance (SSD).
  
  
  METHODS
  A total of 10 patients seen in the emergency room within a mean of 23 days (range 0-51) underwent both conventional CT and low-dose CT for the same stone. The radiation dose reduction was calculated according to the patient's body mass index. The CT scans were performed with 2-mm section cuts, and 3-dimensional reconstruction was performed to obtain the coronal views. The stone size was measured (ie, height, width, and length), and the Hounsfield units were calculated. In addition, the SSD was calculated for the nonmoving renal stones.
  
  
  RESULTS
  No difference was found in stone size between the 2 dosage levels, as measured by the height, width, length, and volume of the stone (P = .9, P = .7, P = .8, and P = .8 respectively). In addition, no difference in Hounsfield units was appreciated between the 2 scan types (P = .6). Finally, no significant difference was found in the SSD (P = .5). Between the 2 scans, the average effective dose reduction was 73%, from 23 to 6 mSv (P = .002).
  
  
  CONCLUSIONS
  No significant difference was found in the measurement of stone size, Hounsfield units, or SSD between the low-dose and conventional-dose CT scans. However, the low-dose CT scans resulted in a marked reduction in the radiation dose to the patient.
authors: Department of Urology, University of California, Irvine, School of Medicine, Orange, CA 92868, USA. wsohn@uci.edu
authors: William
authors: W
authors: Sohn
authors: Ralph V
authors: RV
authors: Clayman
authors: Jason Y
authors: JY
authors: Lee
authors: Allen
authors: A
authors: Cohen
authors: Phillip
authors: P
authors: Mucksavage
mesh_terms: D015992:Body Mass Index; D005260:Female; D006801:Humans; D007669:Kidney Calculi / Q000000981:diagnostic imaging* / Q000473:pathology; D008297:Male; D011829:Radiation Dosage; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed / Q000379:methods*; D014514:Ureteral Calculi / Q000000981:diagnostic imaging* / Q000473:pathology