title: Low kilovoltage peak (kVp) with an adaptive statistical iterative reconstruction algorithm in computed tomography urography: evaluation of image quality and radiation dose.
abstract: OBJECTIVE
  The purpose of this study was to evaluate the image quality and radiation dose in computed tomography urography (CTU) images acquired with a low kilovoltage peak (kVp) in combination with an adaptive statistical iterative reconstruction (ASiR) algorithm.
  
  
  METHODS
  A total of 45 subjects (18 women, 27 men) who underwent CTU with kV assist software for automatic selection of the optimal kVp were included and divided into two groups (A and B) based on the kVp and image reconstruction algorithm: group A consisted of patients who underwent CTU with a 80 or 100 kVp and whose images were reconstructed with the 50% ASiR algorithm (n=32); group B consisted of patients who underwent CTU with a 120 kVp and whose images were reconstructed with the filtered back projection (FBP) algorithm (n=13). The images were separately reconstructed with volume rendering (VR) and maximum intensity projection (MIP). Finally, the image quality was evaluated using an image score, CT attenuation, image noise, the contrast-to-noise ratio (CNR) of the renal pelvis-to-abdominal visceral fat and the signal-to-noise ratio (SNR) of the renal pelvis. The radiation dose was assessed using volume CT dose index (CTDIvol), dose-length product (DLP) and effective dose (ED).
  
  
  RESULTS
  For groups A and B, the subjective image scores for the VR reconstruction images were 3.9±0.4 and 3.8±0.4, respectively, while those for the MIP reconstruction images were 3.8±0.4 and 3.6±0.6, respectively. No significant difference was found (p>0.05) between the two groups' image scores for either the VR or MIP reconstruction images. Additionally, the inter-reviewer image scores did not significantly differ (p>0.05). The mean attenuation of the bilateral renal pelvis in group A was significantly higher than that in group B (271.4±57.6 vs. 221.8±35.3 HU, p<0.05), whereas the image noise in group A was significantly lower than that in group B (7.9±2.1 vs. 10.5±2.3 HU, p<0.05). The CNR and SNR in group A were both significantly higher than those in group B (53.61±24.74 vs. 32.30±6.52 for CNR; 38.13±19.86 vs. 21.76±4.85 for SNR; all p<0.05). The CTDIvol, DLP and ED in group A were significantly lower than those in group B (9.26±2.77 vs. 16.19±5.60 mGy for CTDIvol; 368.86±119.38 vs. 674.38±239.37 mGy×cm-1for DLP; 5.53±1.79 vs. 10.12±3.59 mSv for ED; all p<0.05).
  
  
  CONCLUSIONS
  The low kVp CTU images with 50% ASiR reconstruction exhibit sufficient image quality and facilitate up to a 44% radiation dose reduction.
authors.affiliation: Department of Radiology, Shanghai General Hospital, Shanghai Jiao Tong University Shanghai 200080, China.
authors.forename: Zhiguo
authors.initials: Z
authors.lastname: Zhou
authors.affiliation: Department of Radiology, Shanghai General Hospital, Shanghai Jiao Tong University Shanghai 200080, China.
authors.forename: Haixi
authors.initials: H
authors.lastname: Chen
authors.affiliation: Department of Surgery, Xiangya Hospital, Central South University Changsha 410008, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Wei
authors.affiliation: Department of Oral and Maxillofacial-Head and Neck Oncology, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine Shanghai, China.
authors.forename: Shanghui
authors.initials: S
authors.lastname: Zhou
authors.affiliation: Department of Radiology, Shanghai General Hospital, Shanghai Jiao Tong University Shanghai 200080, China.
authors.forename: Jingbo
authors.initials: J
authors.lastname: Xu
authors.affiliation: Department of Radiology, Shanghai General Hospital, Shanghai Jiao Tong University Shanghai 200080, China.
authors.forename: Xifu
authors.initials: X
authors.lastname: Wang
authors.affiliation: Department of Radiology, Shanghai General Hospital, Shanghai Jiao Tong University Shanghai 200080, China.
authors.forename: Qingguo
authors.initials: Q
authors.lastname: Wang
authors.affiliation: Department of Radiology, Shanghai General Hospital, Shanghai Jiao Tong University Shanghai 200080, China.
authors.forename: Guixiang
authors.initials: G
authors.lastname: Zhang
authors.affiliation: Department of Radiology, Feinberg School of Medicine, Northwestern University Chicago, IL 60611, USA.
authors.forename: Zhuoli
authors.initials: Z
authors.lastname: Zhang
authors.affiliation: Department of Radiology, Shanghai General Hospital, Shanghai Jiao Tong UniversityShanghai 200080, China; Department of Radiology, Feinberg School of Medicine, Northwestern UniversityChicago, IL 60611, USA.
authors.forename: Linfeng
authors.initials: L
authors.lastname: Zheng
keywords: Computed tomography urography; adaptive statistical iterative reconstruction (ASiR) algorithm; low kilovoltage peak