title: Relationship between chest lateral width, tube current, image noise, and radiation exposure associated with coronary artery calcium scanning on 320-detector row CT.
abstract: BACKGROUND
  The relationship between chest lateral width, tube current, image noise, and radiation exposure on 320-detector row CT has not been reported.
  
  
  OBJECTIVE
  We investigated the relationships between chest lateral width, estimated radiation exposure (DLPe), and image noise in 300 patients undergoing clinical coronary calcium scanning.
  
  
  METHODS
  Patients undergoing coronary calcium scanning with 320-detector row CT (prospective, volumetric mode, 120 kV of tube voltage, 100-550 mA of tube current, 0.5-mm detector width) were grouped by chest lateral width (small, medium, and large) from anteroposterior topograms and 100 consecutive patients were selected from each group (n = 300). Tube current, DLPe, and noise were compared among groups with Kruskal-Wallis or one-way ANOVA. Phantom experiments were performed to evaluate the accuracy of calcium quantification as a function of size and tube current.
  
  
  RESULTS
  Median tube current in small, medium, and large patients was 130, 200, and 250 mA, respectively (P < 0.0001). Despite the use of higher tube current settings, noise levels also increased with size (20.2 ± 4.5 HU, 22.0 ± 3.9 HU, and 25.1 ± 4.9 HU, respectively; global P < 0.001). DLPe was significantly higher with increasing size (54, 83, and 104 mGy · cm, respectively; P < 0.0001). Phantom experiments showed that 50-100 mA, 150-200 mA, and approximately 300 mA in small, medium, and large phantoms were associated with stable estimate of calcium.
  
  
  CONCLUSIONS
  Increasing chest lateral width is associated with increasing radiation exposure and image noise. The use of 50-100 mA in small and 150-200 mA in medium patients is associated with acceptable noise and stable estimate of coronary artery calcium. In large patients, precise identification of individual calcified lesions remains difficult despite increasing tube current and radiation exposure.
authors: Piedmont Heart Institute, 1968 Peachtree Rd, NW, Atlanta, GA 30309, USA.
authors: Zhen
authors: Z
authors: Qian
authors: Parag H
authors: PH
authors: Joshi
authors: Ayesha F
authors: AF
authors: Shaukat
authors: Torrance
authors: T
authors: Laury
authors: Ben
authors: B
authors: Kirkland
authors: Lori
authors: L
authors: Meyers
authors: Allison
authors: A
authors: Drew
authors: Erin
authors: E
authors: Angel
authors: Eric
authors: E
authors: Krivitsky
authors: Ambar
authors: A
authors: Bajpai
authors: Gustavo
authors: G
authors: Vazquez
authors: Christian
authors: C
authors: O'Rourke
authors: J Jeffrey
authors: JJ
authors: Carr
authors: Sarah
authors: S
authors: Rinehart
authors: Szilard
authors: S
authors: Voros
mesh_terms: D000368:Aged; D000465:Algorithms; D000704:Analysis of Variance; D000886:Anthropometry; D016477:Artifacts; D002114:Calcinosis / Q000000981:diagnostic imaging*; D016009:Chi-Square Distribution; D017023:Coronary Angiography / Q000295:instrumentation*; D003324:Coronary Artery Disease / Q000000981:diagnostic imaging*; D004867:Equipment Design; D005260:Female; D005845:Georgia; D006801:Humans; D008297:Male; D008875:Middle Aged; D019047:Phantoms, Imaging; D011237:Predictive Value of Tests; D011829:Radiation Dosage; D011857:Radiographic Image Interpretation, Computer-Assisted; D012189:Retrospective Studies; D012720:Severity of Illness Index; D013909:Thorax / Q000033:anatomy & histology*; D014057:Tomography, X-Ray Computed / Q000295:instrumentation*