title: Comparison of Measured and Estimated CT Organ Doses for Modulated and Fixed Tube Current:: A Human Cadaver Study.
abstract: OBJECTIVE
  The aim of this study was to compare the directly measured and the estimated computed tomography (CT) organ doses obtained from commercial radiation dose-tracking (RDT) software for CT performed with modulated tube current or automatic exposure control (AEC) technique and fixed tube current (mAs).
  
  
  METHODS
  With the institutional review board (IRB) approval, the ionization chambers were surgically implanted in a human cadaver (88 years old, male, 68 kg) in six locations such as liver, stomach, colon, left kidney, small intestine, and urinary bladder. The cadaver was scanned with routine abdomen pelvis protocol on a 128-slice, dual-source multidetector computed tomography (MDCT) scanner using both AEC and fixed mAs. The effective and quality reference mAs of 100, 200, and 300 were used for AEC and fixed mAs, respectively. Scanning was repeated three times for each setting, and measured and estimated organ doses (from RDT software) were recorded (N = 3*3*2 = 18).
  
  
  RESULTS
  Mean CTDIvol for AEC and fixed mAs were 4, 8, 13 mGy and 7, 14, 21 mGy, respectively. The most estimated organ doses were significantly greater (P < 0.01) than the measured organ doses for both AEC and fixed mAs. At AEC, the mean estimated organ doses (for six organs) were 14.7 mGy compared to mean measured organ doses of 12.3 mGy. Similarly, at fixed mAs, the mean estimated organ doses (for six organs) were 24 mGy compared to measured organ doses of 22.3 mGy. The differences among the measured and estimated organ doses were higher for AEC technique compared to the fixed mAs for most organs (P < 0.01).
  
  
  CONCLUSIONS
  The most CT organ doses estimated from RDT software are greater compared to directly measured organ doses, particularly when AEC technique is used for CT scanning.
authors: Department of Radiology, Massachusetts General Hospital, 55 Fruit Street, Boston, MA 02114. Electronic address: apadole@mgh.harvard.edu.
authors: Atul
authors: A
authors: Padole
authors: Department of Radiology, Massachusetts General Hospital, 55 Fruit Street, Boston, MA 02114.
authors: Ranish
authors: R
authors: Deedar Ali Khawaja
authors: Department of Radiology, Massachusetts General Hospital, 55 Fruit Street, Boston, MA 02114.
authors: Alexi
authors: A
authors: Otrakji
authors: Department of Radiology, Massachusetts General Hospital, 55 Fruit Street, Boston, MA 02114.
authors: Da
authors: D
authors: Zhang
authors: Department of Radiology, Massachusetts General Hospital, 55 Fruit Street, Boston, MA 02114.
authors: Bob
authors: B
authors: Liu
authors: Department of Mechanical, Aerospace, and Nuclear Engineering, Rensselaer Polytechnic Institute, Troy, New York.
authors: X George
authors: XG
authors: Xu
authors: Department of Radiology, Massachusetts General Hospital, 55 Fruit Street, Boston, MA 02114.
authors: Mannudeep K
authors: MK
authors: Kalra
mesh_terms: D050153:Abdominal Fat / Q000528:radiation effects; D000369:Aged, 80 and over; D016477:Artifacts; D002102:Cadaver; D003106:Colon / Q000528:radiation effects; D006801:Humans; D007421:Intestine, Small / Q000528:radiation effects; D007668:Kidney / Q000528:radiation effects; D008099:Liver / Q000528:radiation effects; D008297:Male; D061330:Multidetector Computed Tomography / Q000379:methods*; D011829:Radiation Dosage; D000072232:Radiation Dosimeters; D012984:Software; D013270:Stomach / Q000528:radiation effects; D001743:Urinary Bladder / Q000528:radiation effects
keywords: AEC and fixed mAs; CT radiation organ doses; human cadaver dosimetry; measured vs estimated organ doses