A computerized framework for monitoring four-dimensional dose distributions during stereotactic body radiation therapy using a portal dose image-based 2D/3D registration approach

作者：Nakamoto Takahiro; Arimura Hidetaka^*; Nakamura Katsumasa; Shioyama Yoshiyuki; Mizoguchi Asumi; Hirose Taka aki; Honda Hiroshi; Umezu Yoshiyuki; Nakamura Yasuhiko; Hirata Hideki

来源：Computerized Medical Imaging and Graphics, 2015, 40: 1-12.

DOI：10.1016/j.compmedimag.2014.12.003

• Stereotactic body radiation therapy
• Four-dimensional dose distribution
• 2D/3D registration
• Optimization

A computerized framework for monitoring four-dimensional (4D) dose distributions during stereotactic body radiation therapy based on a portal dose image (PDI)-based 2D/3D registration approach has been proposed in this study. Using the PDI-based registration approach, simulated 4D "treatment" CT images were derived from the deformation of 3D planning CT images so that a 2D planning PDI could be similar to a 2D dynamic clinical PDI at a breathing phase. The planning PDI was calculated by applying a dose calculation algorithm (a pencil beam convolution algorithm) to the geometry of the planning CT image and a virtual water equivalent phantom. The dynamic clinical PDIs were estimated from electronic portal imaging device (EPID) dynamic images including breathing phase data obtained during a treatment. The parameters of the affine transformation matrix were optimized based on an objective function and a gamma pass rate using a Levenberg-Marquardt (LM) algorithm. The proposed framework was applied to the EPID dynamic images of ten lung cancer patients, which included 183 frames (mean: 18.3 per patient). The 4D dose distributions during the treatment time were successfully obtained by applying the dose calculation algorithm to the simulated 4D "treatment" CT images. The mean +/- standard deviation (SD) of the percentage errors between the prescribed dose and the estimated dose at an isocenter for all cases was 3.25 +/- 4.43%. The maximum error for the ten cases was 14.67% (prescribed dose: 1.50 Gy, estimated dose: 1.72 Gy), and the minimum error was 0.00%. The proposed framework could be feasible for monitoring the 4D dose distribution and dose errors within a patient's body during treatment.

• 出版日期2015-3