title: Subcutaneous tissue thickness is an independent predictor of image noise in cardiac CT.
abstract: BACKGROUND
  Few data on the definition of simple robust parameters to predict image noise in cardiac computed tomography (CT) exist.
  
  
  OBJECTIVE
  To evaluate the value of a simple measure of subcutaneous tissue as a predictor of image noise in cardiac CT.
  
  
  METHODS
  86 patients underwent prospective ECG-gated coronary computed tomographic angiography (CTA) and coronary calcium scoring (CAC) with 120 kV and 150 mA. The image quality was objectively measured by the image noise in the aorta in the cardiac CTA, and low noise was defined as noise < 30 HU. The chest anteroposterior diameter and lateral width, the image noise in the aorta and the skin-sternum (SS) thickness were measured as predictors of cardiac CTA noise. The association of the predictors and image noise was performed by using Pearson correlation.
  
  
  RESULTS
  The mean radiation dose was 3.5 ± 1.5 mSv. The mean image noise in CT was 36.3 ± 8.5 HU, and the mean image noise in non-contrast scan was 17.7 ± 4.4 HU. All predictors were independently associated with cardiac CTA noise. The best predictors were SS thickness, with a correlation of 0.70 (p < 0.001), and noise in the non-contrast images, with a correlation of 0.73 (p < 0.001). When evaluating the ability to predict low image noise, the areas under the ROC curve for the non-contrast noise and for the SS thickness were 0.837 and 0.864, respectively.
  
  
  CONCLUSIONS
  Both SS thickness and CAC noise are simple accurate predictors of cardiac CTA image noise. Those parameters can be incorporated in standard CT protocols to adequately adjust radiation exposure.
authors.affiliation: Universidade de São Paulo, Hospital Universitário, São PauloSP, Brasil.
authors.forename: Henrique Lane
authors.initials: HL
authors.lastname: Staniak
authors.affiliation: Universidade de São Paulo, Hospital Universitário, São PauloSP, Brasil.
authors.forename: Rodolfo
authors.initials: R
authors.lastname: Sharovsky
authors.affiliation: Universidade de São Paulo, Hospital das Clínicas, São PauloSP, Brasil.
authors.forename: Alexandre Costa
authors.initials: AC
authors.lastname: Pereira
authors.affiliation: Universidade de São Paulo, Hospital Universitário, São PauloSP, Brasil.
authors.forename: Cláudio Campi de
authors.initials: CC
authors.lastname: Castro
authors.affiliation: Universidade de São Paulo, Hospital Universitário, São PauloSP, Brasil.
authors.forename: Isabela M
authors.initials: IM
authors.lastname: Benseñor
authors.affiliation: Universidade de São Paulo, Hospital Universitário, São PauloSP, Brasil.
authors.forename: Paulo A
authors.initials: PA
authors.lastname: Lotufo
authors.affiliation: Universidade de São Paulo, Hospital Universitário, São PauloSP, Brasil.
authors.forename: Márcio Sommer
authors.initials: MS
authors.lastname: Bittencourt
mesh_terms: D000368:Aged; D001027:Aortography / Q000379:methods*; D016477:Artifacts; D015992:Body Mass Index; D017023:Coronary Angiography / Q000379:methods*; D005260:Female; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011829:Radiation Dosage; D012016:Reference Values; D012680:Sensitivity and Specificity; D040521:Subcutaneous Tissue / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed / Q000379:methods*