title: Quarter regular dose non-enhanced CT for urinary stone: added value of adaptive statistical iterative reconstruction.
abstract: BACKGROUND
  As urinary stone diseases are common in young adults and have a high recurrence rate, repetitive computed tomography (CT) scans would increase the radiation hazard. Therefore, CT radiation dose reduction is needed in the diagnosis of urinary stones.
  
  
  OBJECTIVE
  To prospectively evaluate the added value of adaptive statistical iterative reconstruction (ASIR) applied to half-dose (HDCT) and quarter regular dose non-enhanced CT (QDCT) for the detection of urinary stones.
  
  
  METHODS
  One hundred and twelve consecutive patients who presented with acute flank pain and had clinically suspected urinary stones were initially eligible. All patients underwent non-enhanced CT that consisted of HDCT (120 kVp, 100 mAs) and QDCT (120 kVp, 40 mAs). The images were reconstructed separately with a 50% ASIR blending ratio. Two radiologists independently performed a 2-week interval reading to detect urinary stones on a per stone basis (size ≥1 mm) from the QDCT images to the ASIR applied images. Two weeks later, the HDCT images were analyzed in the same manner. The CT image noise was measured for each image set. The sensitivity for urinary stone detection for each set was compared using the McNemar test.
  
  
  RESULTS
  A total of 114 urinary stones were found in 48 patients (37 men, 11 women; mean age, 46 years; range, 19-71 years). After applying ASIR to the QDCT images, the sensitivity increased from 70% to 80% for reader 1 and from 69% to 82% for reader 2 (P = 0.001, respectively). However, in the HDCT images, the sensitivity was unchanged for both readers (reader 1, 87%; reader 2, 89%). The measured noise significantly decreased from 40.2 to 27.7 after applying ASIR to the QDCT images and from 25.1 to 17.6 after applying ASIR to the HDCT images (P = 0.001 for both).
  
  
  CONCLUSIONS
  Although ASIR showed no added diagnostic value for HDCT images, it improved the sensitivity for the detection of urinary stones based on QDCT images.
authors.affiliation: Department of Radiology, Inje University College of Medicine, Haeundae Paik Hospital, Busan, Republic of Korea radiresi@gmail.com.
authors.forename: Seung Ho
authors.initials: SH
authors.lastname: Kim
authors.affiliation: Department of Radiology, Inje University College of Medicine, Haeundae Paik Hospital, Busan, Republic of Korea.
authors.forename: Soo Heui
authors.initials: SH
authors.lastname: Baek
authors.affiliation: Department of Radiology, Inje University College of Medicine, Haeundae Paik Hospital, Busan, Republic of Korea.
authors.forename: Jung-Hee
authors.initials: JH
authors.lastname: Yoon
authors.affiliation: Department of Radiology, Inje University College of Medicine, Haeundae Paik Hospital, Busan, Republic of Korea.
authors.forename: Yun-Jung
authors.initials: YJ
authors.lastname: Lim
authors.affiliation: Department of Radiology, Inje University College of Medicine, Haeundae Paik Hospital, Busan, Republic of Korea.
authors.forename: Hye Jin
authors.initials: HJ
authors.lastname: Baek
authors.affiliation: Department of Radiology, Inje University College of Medicine, Haeundae Paik Hospital, Busan, Republic of Korea.
authors.forename: Seon-Jeong
authors.initials: SJ
authors.lastname: Kim
authors.affiliation: Department of Radiology, Inje University College of Medicine, Haeundae Paik Hospital, Busan, Republic of Korea.
authors.forename: Choong Ki
authors.initials: CK
authors.lastname: Eun
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011829:Radiation Dosage; D011857:Radiographic Image Interpretation, Computer-Assisted; D014057:Tomography, X-Ray Computed / Q000379:methods*; D014545:Urinary Calculi / Q000000981:diagnostic imaging*
keywords: Iterative reconstruction; computed tomography; image reconstruction; radiation dosage; urinary stone