Assessment of 4D-CBCT imaging performance and strategies for 4D-CBCT guided IGRT Project

Date(s) - 03/10/2014
1:00 pm

Soyoung Lee, PhD student

Lung cancer is the leading cause of cancer related mortality in the United States. Only 15% of lung cancers are detected at early stage. The 5-year survival rate for all stage combined is only 16% (American Cancer Society, Cancer Facts and Figures 2013).17% and 35% of lung cancer patients undergo radiation therapy alone and radiation therapy combined treatment. For the patient, advanced treatment techniques and tools accounting for respiratory motion are urgent to improve treatment outcomes.

One promising solution to improved treatment quality is high-precision image-guided radiotherapy (IGRT), which has been used to raise tumor dose while minimizing the dose to healthy tissue.  The use of four-dimensional (4D) imaging has shown continued increase in the demands on high quality treatment when there is respiratory motion of patients. In recent, 4D cone-beam computed tomography (4D-CBCT) guided imaging is one of potential imaging techniques, which have brought benefits to lung patients, allowing accurate tumor localization in patient setup process and reliable treatment delivery with adequate coverage. The implementation of 4D-CBCT imaging correlated to respiration needs to be optimized for individual patient’s breathing and a specific treatment site. In order for the efficient use of 4D-CBCT image guidance tool in treatment process, this study will extensively assess the imaging performance of 4D-CBCT system and investigate suitable clinical implementation for 4D-CBCT imaging.

The 4D-CBCT based IGRT techniques leads to increasing need for monitoring and optimizing of the treatment plan in 4D nature. We will provide a rigorous study of 4D-CBCT imaging for wide use of clinical condition. (1) Image quality of CBCT systems will be carried out using fundamental metrics such as MTF, NPS, and cDQE. (2) Then, these metrics will be applied to quantitatively assesse the image quality in 4D-CBCT. This will include assessing image quality for a variety of respiratory motions to ultimately predict the treatment outcomes based on baseline estimation using a phantom. (3) Utilizing image registration methods, tumor motion trajectories extracted from the 4D-CBCT images will be evaluated with respect to simulated motions. An uncertainty analysis will be carried out to better understand the limits of IGRT.

Through an investigation of the above strategies, this research will provide guidance to the efficient use of 4D-CBCT system in IGRT. Ultimately, the proposed study will allows physicians to be confident on radiation dose delivery to the tumor during treatments.