title: Variability of MDCT dose due to technologist performance: impact of posteroanterior versus anteroposterior localizer image and table height with use of automated tube current modulation.
abstract: OBJECTIVE
  The purpose of this study was to determine MDCT dose variability due to technologist variability in performing CT studies.
  
  
  METHODS
  Fifty consecutive adult patients who underwent two portal venous phase CT examinations of the abdomen and pelvis on the same 64-MDCT scanner between January and December 2011 were retrospectively identified. Tube voltage (kVp), tube current (mA), use of automated tube current modulation (ATCM), dose-length product (DLP), volume CT dose index (CTDIvol), table height, whether the localizer image was obtained using the posteroanterior or the anteroposterior technique, arm position, and number of overscanned slices were recorded.
  
  
  RESULTS
  For a given patient, the total examination DLP difference comparing the two MDCT studies ranged from 0.1% to 238.0%. For the same patient, total examination DLP was always higher when the localizer image was obtained with the posteroanterior compared with the anteroposterior technique. When table position was closer to the x-ray source, patients appeared magnified in the posteroanterior localizer image (8-29%; average, 14%) and higher tube currents were selected with ATCM. Localizer technique, table height, arm position, number of overscanned slices, and technologist were all significant predictors of dose.
  
  
  CONCLUSIONS
  Patient off-centering closer to the x-ray source resulted in patient magnification in the posteroanterior localizer image, leading to higher tube currents with ATCM and increased DLP. Differences in technologist, arm position, and overscanning also resulted in dose variability.
authors: 1 Department of Radiology and Imaging Sciences, Emory University School of Medicine, 1364 Clifton Rd NE, Atlanta, GA 30322.
authors: Peter A
authors: PA
authors: Harri
authors: Courtney C
authors: CC
authors: Moreno
authors: Rendon C
authors: RC
authors: Nelson
authors: Negar
authors: N
authors: Fani
authors: William C
authors: WC
authors: Small
authors: Phuong-Anh T
authors: PA
authors: Duong
authors: Anh
authors: A
authors: Duong
authors: Xiangyang
authors: X
authors: Tang
authors: Kimberly E
authors: KE
authors: Applegate
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002983:Clinical Competence; D003287:Contrast Media; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D061330:Multidetector Computed Tomography; D056888:Patient Positioning; D011829:Radiation Dosage; D011860:Radiography, Abdominal
chemical_list: D003287:Contrast Media
keywords: CT; automated tube current modulation; radiation dose