Iterative Reconstruction for Head CT: Effects on Radiation Dose and Image Quality.
BACKGROUND
Iterative reconstruction has been reported to reduce radiation dose in CT, while preserving and even improving image quality. The purpose of this study was to evaluate the effects of sinogram-affirmed iterative reconstruction (SAFIRE) on radiation dose reduction and image quality for noncontrast adult head CT and to compare SAFIRE with conventional filtered back-projection (FBP) reconstruction.


METHODS
Institutional review board approval was obtained for this retrospective analysis of head CT scans reconstructed with SAFIRE and/or FBP for 107 patients. Radiation dose parameters were recorded from scanner-generated CT dose reports. Signal-to-noise and contrast-to-noise ratios (SNR, CNR) were calculated from gray and white matter (GM, WM) attenuation measurements. Image noise, artifacts, GM-WM differentiation, small structure visibility, and sharpness were graded by two readers. Statistical analysis included the independent-samples t test for quantitative data, the related samples Wilcoxon signed-rank test for qualitative data, the coefficient of repeatability for intraobserver variation, and κ statistics for interobserver agreement.


RESULTS
Mean effective dose was significantly reduced with SAFIRE from 2.0 to 1.7 mSv (p<0.0001). SAFIRE also significantly improved GM SNR, WM SNR, and GM-WM CNR (p<0.0001). Significant reductions in image noise and posterior fossa artifact as well as improvements in GM-WM differentiation, small structure visibility, and sharpness were noted with SAFIRE (P<0.005).


CONCLUSIONS
SAFIRE for noncontrast adult head CT reduces patient radiation dose by 15% for the settings employed at our institution, while significantly improving multiple quantitative and qualitative measures of image quality.
1Residency Training Program,Halifax,NS,Canada.
Michael D
MD
Rivers-Bowerman
2Division of Neuroradiology,Department of Diagnostic Radiology,Queen Elizabeth II Health Sciences Centre and Dalhousie University,Halifax,NS,Canada.
Jai Jai Shiva
JJ
Shankar
D000328:Adult; D000368:Aged; D005260:Female; D006257:Head / Q000000981:diagnostic imaging*; D006801:Humans; D007089:Image Enhancement / Q000379:methods / Q000592:standards*; D007091:Image Processing, Computer-Assisted / Q000379:methods / Q000592:standards*; D008297:Male; D008875:Middle Aged; D011829:Radiation Dosage; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed / Q000379:methods / Q000592:standards*