Room: Exhibit Hall | Forum 9
Purpose: The purpose of this study was to evaluate the image quality of a commercially available cone beam computed tomography based on iterative reconstruction for image guided radiation therapy (IGRT)
Methods: All image sets for Catphan 604 phantom were acquired on VitalBeam linear accelerator (Varian Medical Systems, Palo Alto, CA) kV imaging system using full-fan half rotation head mode both Standard CBCT reconstruction using the Feldkamp-Davis-Kress (FDK) algorithm and iterative CBCT reconstruction (iCBCT). Image acquisition parameters were set at 125 kVp, 60 mAs, and 18.5 cm of scan range. Standard smoothing filter and medium ring correction factor were applied to image set acquired with FDK reconstruction algorithm. In the case of iCBCT, standard smoothing filter was used, and each image set was acquired by applying 5 available noise reduction factor. We have quantitatively analyzed the reconstructed CBCT image quality in terms of uniformity, HU constancy, spatial resolution, low contrast, noise level, and contrast-to-noise ratio (CNR). Furthermore, in-house developed teeth and implant inserted head & neck phantom was scanned for evaluation of improvement for image quality.
Results: The results of imaging analysis for Catphan phantom show that noises of iCBCT was reduced at all noise reduction factor compared with those of FDK reconstruction method. The noise using the FDK reconstruction was reduced from 32.0 to a range between 20.1 and 10.8. The CNR was improved from 0.4 to a range between 0.5 and 2.3 for iCBCT. The metal artifacts caused by in-house developed H&N phantom were reduced in image set using iCBCT compared with FDK reconstruction.
Conclusion: We analyzed the image quality of iCBCT with various noise suppressions for Catphan phantom and in-house developed H&N phantom. Compared with the conventional FDK algorithm, the improvement of CNR and the reduction of noise could be achieved by applying appropriate noise suppression and filter.
Not Applicable / None Entered.