title: Effect of edge-preserving adaptive image filter on low-contrast detectability in CT systems: application of ROC analysis.
abstract: OBJECTIVE
  For the multislice CT (MSCT) systems with a larger number of detector rows, it is essential to employ dose-reduction techniques. As reported in previous studies, edge-preserving adaptive image filters, which selectively eliminate only the noise elements that are increased when the radiation dose is reduced without affecting the sharpness of images, have been developed. In the present study, we employed receiver operating characteristic (ROC) analysis to assess the effects of the quantum denoising system (QDS), which is an edge-preserving adaptive filter that we have developed, on low-contrast resolution, and to evaluate to what degree the radiation dose can be reduced while maintaining acceptable low-contrast resolution.
  
  
  METHODS
  The low-contrast phantoms (Catphan 412) were scanned at various tube current settings, and ROC analysis was then performed for the groups of images obtained with/without the use of QDS at each tube current to determine whether or not a target could be identified. The tube current settings for which the area under the ROC curve (Az value) was approximately 0.7 were determined for both groups of images with/without the use of QDS. Then, the radiation dose reduction ratio when QDS was used was calculated by converting the determined tube current to the radiation dose.
  
  
  RESULTS
  The use of the QDS edge-preserving adaptive image filter allowed the radiation dose to be reduced by up to 38%.
  
  
  CONCLUSIONS
  The QDS was found to be useful for reducing the radiation dose without affecting the low-contrast resolution in MSCT studies.
authors.affiliation: CT Systems Development Department, Toshiba Medical Systems Corporation, 1385 Shimoishigami, Otawara-Shi, Tochigi 324-8550, Japan.
authors.forename: Miwa
authors.initials: M
authors.lastname: Okumura
authors.forename: Takamasa
authors.initials: T
authors.lastname: Ota
authors.forename: Kazuhisa
authors.initials: K
authors.lastname: Kainuma
authors.forename: James W
authors.initials: JW
authors.lastname: Sayre
authors.forename: Michael
authors.initials: M
authors.lastname: McNitt-Gray
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Katada