title: A pilot study of patient-specific cardiovascular MDCT dose maps and their utility in estimating patient-specific organ and effective doses in obese patients.
abstract: BACKGROUND
  Estimates of effective dose (E) for cardiovascular CT are obtained from a scanner-provided dose metric, the dose-length product (DLP), and a conversion factor. These estimates may not adequately represent the risk of a specific scan to obese adults.
  
  
  OBJECTIVE
  Our objective was to create dose maps sensitive to patient size and anatomy in the irradiated region from a patient's own CT images and compare measured E (EDoseMap) to doses determined from standard DLP conversion (EDLP) in obese adults.
  
  
  METHODS
  21 obese patients (mean body mass index, 39 kg/m(2)) underwent CT of the pulmonary veins, thoracic aorta, or coronary arteries. DLP values were converted to E. A Monte Carlo tool was used to simulate X-ray photon interaction with virtual phantoms created from each patient's image set. Organ doses were determined from dose maps. EDoseMap was computed as a weighted sum of organ doses multiplied by tissue-weighting factors.
  
  
  RESULTS
  EDLP (mean ± SD, 5.7 ± 3.3 mSv) was larger than EDoseMap (3.4 ± 2.4 mSv) (difference = 2.3; P < .001).
  
  
  CONCLUSIONS
  Dose maps derived from patient CT images yielded lower effective doses than DLP conversion methods. Considering over all patient size, organ size, and tissue composition could lead to better dose metrics for obese patients.
authors: Cardiovascular Imaging, Imaging Institute, Cleveland Clinic, Cleveland, OH, USA; Department of Chemical and Biomedical Engineering, Cleveland State University, Cleveland, OH, USA; Department of Biomedical Engineering, Lerner Research Institute Cleveland Clinic, Cleveland, OH, USA. Electronic address: carla.m.thompson@vanderbilt.edu.
authors: Carla M
authors: CM
authors: Thompson
authors: Philips Healthcare, Cleveland, OH, USA.
authors: Jeffrey H
authors: JH
authors: Yanof
authors: Philips Research, Munich, Germany.
authors: Jens
authors: J
authors: Wiegert
authors: Quantitative Health Sciences, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, USA.
authors: Jennifer
authors: J
authors: Bullen
authors: Quantitative Health Sciences, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, USA.
authors: Nancy
authors: N
authors: Obuchowski
authors: Cardiovascular Imaging, Imaging Institute, Cleveland Clinic, Cleveland, OH, USA.
authors: Kavitha
authors: K
authors: Yaddanapudi
authors: Cardiovascular Imaging, Imaging Institute, Cleveland Clinic, Cleveland, OH, USA; Department of Chemical and Biomedical Engineering, Cleveland State University, Cleveland, OH, USA; Department of Biomedical Engineering, Lerner Research Institute Cleveland Clinic, Cleveland, OH, USA; Department of Cardiovascular Medicine, Heart and Vascular Institute, Cleveland Clinic, Cleveland, OH, USA.
authors: Sandra S
authors: SS
authors: Halliburton
mesh_terms: D001013:Aorta, Thoracic / Q000000981:diagnostic imaging; D001027:Aortography / Q000379:methods*; D015992:Body Mass Index; D002318:Cardiovascular Diseases / Q000150:complications / Q000000981:diagnostic imaging*; D000072226:Computed Tomography Angiography / Q000295:instrumentation; D017023:Coronary Angiography / Q000295:instrumentation / Q000379:methods*; D003331:Coronary Vessels / Q000000981:diagnostic imaging; D006801:Humans; D009010:Monte Carlo Method; D061330:Multidetector Computed Tomography / Q000295:instrumentation; D009765:Obesity / Q000150:complications* / Q000175:diagnosis; D066230:Patient-Specific Modeling; D019047:Phantoms, Imaging; D010690:Phlebography / Q000295:instrumentation / Q000379:methods*; D010865:Pilot Projects; D011237:Predictive Value of Tests; D011667:Pulmonary Veins / Q000000981:diagnostic imaging; D011829:Radiation Dosage; D012189:Retrospective Studies
keywords: Dose-length product; Effective dose; Monte Carlo; Organ dose