Correction of megavoltage cone-beam CT images for dose calculation in the head and neck region.
Megavoltage cone-beam computed tomography (MVCBCT) imaging systems are now available for image-guided radiation therapy delivery and verification. In order to use the three-dimensional anatomical information for dose calculation, the MVCBCT image must provide accurate electron density. This work proposes a new method that has been developed to correct for the cupping and missing data artifacts seen on MVCBCT images of the head and neck region. It uses a conventional kilovoltage CT (kVCT) image as a reference for electron density and rigid registration with a MVCBCT image to obtain correction factors. Dose calculations performed on MVCBCT images corrected with the proposed method agree with calculations done on kVCT images within +/- 1% on phantoms. With patients images the agreement is within +/- 13% above the shoulders and +/- 5% below the shoulder line. This level of dose calculation accuracy allows the use of MVCBCT images for dose verification purposes.
Aubry
Jean-François
JF
Department of Radiation Oncology, University of California San Francisco, 1600 Divisadero Street, Suite H1031, San Francisco, California 94143, USA. ambryjt@rodone.usef.edu
Pouliot
Jean
J
Beaulieu
Luc
L
D000465:Algorithms; D054893:Cone-Beam Computed Tomography / Q000379:methods*; D006257:Head / Q000000981:diagnostic imaging*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D009333:Neck / Q000000981:diagnostic imaging*; D011829:Radiation Dosage; D012680:Sensitivity and Specificity