title: Coronary artery calcium measurement with multi-detector row CT and low radiation dose: comparison between 55 and 165 mAs.
abstract: OBJECTIVE
  To prospectively compare the results of coronary artery calcium (CAC) measurements obtained with 55- and 165-mAs electrocardiographically gated multi-detector row computed tomography (CT).
  
  
  METHODS
  Institutional clinical study review board approval and written informed consent were obtained. Fifty-one consecutive subjects (mean age, 59 years +/- 10) were scanned consecutively by using 165 and 55 mAs. For each examination, the number of lesions, total calcium score (TCS) calculated with Agatston algorithm (130-HU threshold), and calcium mass (in milligrams) were measured. Noise was measured by averaging 1 standard deviation of the CT attenuation values in five consecutive transverse sections of the ascending aorta. Paired t test and Pearson correlation were used to compare measurements between the examinations.
  
  
  RESULTS
  By using 55 mAs, CAC was detected (TCS > 0) in all 33 subjects in whom CAC was initially detected with 165 mAs. The mean values of CAC measures with 165 and 55 mAs, respectively, were as follows: number of lesions, 6.2 +/- 9.6 and 6.1 +/- 9.4; TCS, 123 +/- 223 and 126 +/- 225; and calcium mass, 23.25 mg +/- 43 and 24.25 mg +/- 44 (P value was not significant for all parameters). Significant high correlation was found between the two methods for all measures (r > 0.90, P < .01). Similar results were obtained with analysis by coronary vessel. Image noise was 9.3 HU +/- 2.1 with 165 mAs and 14.7 HU +/- 3.9 with 55 mAs (P < .001), with a parallel decrease in the volume CT dose index from 12 to 4 mGy.
  
  
  CONCLUSIONS
  Radiation dose can be reduced (eg, 55 mAs) for CAC detection and measurement at multi-detector row CT and provides results comparable to those obtained with 165 mAs.
authors.affiliation: Grace Ballas Research Unit of the Cardiac Rehabilitation Institute, Chaim Sheba Medical Center, Sackler School of Medicine and Division of Epidemiology and Preventive Medicine, Tel-Aviv University, Tel-Hashomer 52621, Israel. dshemesh@netvision.net.il
authors.forename: Joseph
authors.initials: J
authors.lastname: Shemesh
authors.forename: Rami
authors.initials: R
authors.lastname: Evron
authors.forename: Nira
authors.initials: N
authors.lastname: Koren-Morag
authors.forename: Sara
authors.initials: S
authors.lastname: Apter
authors.forename: Judith
authors.initials: J
authors.lastname: Rozenman
authors.forename: Dorith
authors.initials: D
authors.lastname: Shaham
authors.forename: Yacov
authors.initials: Y
authors.lastname: Itzchak
authors.forename: Michael
authors.initials: M
authors.lastname: Motro
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002114:Calcinosis / Q000000981:diagnostic imaging*; D003327:Coronary Disease / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011829:Radiation Dosage; D011857:Radiographic Image Interpretation, Computer-Assisted; D014057:Tomography, X-Ray Computed / Q000379:methods*