title: Lowering radiation dose during dedicated colorectal cancer MDCT: comparison of low tube voltage and sinogram-affirmed iterative reconstruction at 80 kVp versus blended dual-energy images in a population of patients with low body mass index.
abstract: OBJECTIVE
  To assess the diagnostic accuracy, cancer staging, image quality, and radiation dose of 80-kVp computed tomography (CT) images for patients with colorectal cancers (CRCs) using sinogram-affirmed iterative reconstruction (SAFIRE).
  
  
  METHODS
  Sixty-four consecutive patients (mean weight 62.5  ±  11.3 kg, mean BMI 24.1  ±  3.3 kg/m(2)) with known CRC underwent dual-energy CT. Data were reconstructed as a weighted average (WA) 120-kVp dataset. Both filtered back projection (FBP) and SAFIRE were applied to reconstruct the WA 120-Kvp (Protocol A, B) and 80-kVp (Protocol C, D) image sets. The image noise, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) of the cancers, the normal reference tissues, and the effective dose for each protocol were assessed. The cancer detection, staging, and image quality were evaluated. Analysis of variance was used for statistical analysis.
  
  
  RESULTS
  Compared with the FBP datasets at WA 120-kVp (Protocol A) and 80-kVp (Protocol C), the SAFIRE-reconstructed images (Protocols B, D) demonstrated significantly lower image noise (P  <  0.0083). Protocol D yielded significantly higher CNRs and SNRs for the CRCs and normal reference tissues than did Protocols A and C (P  <  0.0083). Protocol D also exhibited a significantly higher CNR for the CRC and some normal reference tissues than did Protocol B (P  <  0.0083). For hypovascular liver metastases (n  =  10), Protocol D yielded better SNRs and significantly higher CNRs than did Protocol A (P  <  0.0083). Overall, accuracy for tumor staging and liver metastasis was 95.3% (61/64) and 100%, respectively, in all of the 4 protocols. The mean effective dose decreased 41% from the WA 120-kVp to the 80-kVp protocols (6.23 vs. 3.68 mSv).
  
  
  CONCLUSIONS
  The 80-kVp technique with SAFIRE provided high SNR, high CNR, and good accuracy for staging in nonobese patients with CRC. Our study results should be extrapolated to patient populations with a high BMI with caution. Further studies of high BMI patients are therefore warranted.
authors: Graduate Institute of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan.|Department of Radiology, Faculty of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan.|Department of Medical Imaging, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan.
authors: Chiao-Yun
authors: CY
authors: Chen
authors: Graduate Institute of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan.|Department of Medical Imaging, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan.
authors: Jui-Sheng
authors: JS
authors: Hsu
authors: Department of Radiology, Faculty of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan.|Department of Medical Imaging, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan.
authors: Twei-Shiun
authors: TS
authors: Jaw
authors: Department of Medical Imaging, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan.|Section of Abdominal Imaging, Department of Medical Imaging, Chi Mei Medical Center, Tainan City, Taiwan.
authors: Yu-Ting
authors: YT
authors: Kuo
authors: Graduate Institute of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan.|Division of Internal Medicine, Kaohsiung Municipal Hsiao-Kang Hospital, Kaohsiung, Taiwan.|Department of Medicine, Faculty of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan.|Division of Gastroenterology, Department of Internal Medicine, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan.
authors: Deng-Chyang
authors: DC
authors: Wu
authors: Department of Public Health, Kaohsiung Medical University, Kaohsiung, Taiwan.
authors: Chien-Hung
authors: CH
authors: Lee
authors: Department of Radiology, Faculty of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan.|Department of Medical Imaging, Kaohsiung Municipal Hsiao-Kang Hospital, Kaohsiung, Taiwan.
authors: Ming-Chen Paul
authors: MC
authors: Shih
authors: Department of Medical Imaging, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan.
authors: Tzu-Hsueh
authors: TH
authors: Tsai
authors: Department of Medicine, Faculty of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan.|Division of Gastroenterology, Department of Internal Medicine, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan.
authors: Chao-Hung
authors: CH
authors: Kuo
authors: Department of Pathology, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan.
authors: Yi-Ting
authors: YT
authors: Chen
authors: Department of Medical Imaging, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan.
authors: Li-Hwa
authors: LH
authors: Yang
authors: Graduate Institute of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan. gcliu@kmu.edu.tw.|Department of Radiology, Faculty of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan. gcliu@kmu.edu.tw.|Department of Medical Imaging, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan. gcliu@kmu.edu.tw.
authors: Gin-Chung
authors: GC
authors: Liu
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015992:Body Mass Index; D002985:Clinical Protocols; D015179:Colorectal Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D061330:Multidetector Computed Tomography / Q000295:instrumentation*; D009367:Neoplasm Staging; D011829:Radiation Dosage; D011857:Radiographic Image Interpretation, Computer-Assisted
keywords: Abdomen; Colorectal cancer; Dual-energy CT; Filtered back projection (FBP); Low-radiation-dose technique; Sinogram-affirmed iterative reconstruction (SAFIRE)