Strategies For KVCBCT-Guided Patient Setup of Stereotactic Radiotherapy and Assessments of their Dose Consequences

Date(s) - 06/24/2013
4:00 pm

Bo Lu - BME PhD Student


Stereotactic radiotherapy (SRT) technique has been widely utilized for various treatments sites over the past two decades. To be able to escalate target dose while keeping normal tissue dose under toxicity threshold during every session of the entire treatment course, high accuracy and reproducibility of patient positioning were required.  

Until recent, Kilo-Voltage (kV) CBCT systems integrated into the gantries of linear accelerators have been pervasively employed as an advanced image-guided radiotherapy (IGRT) modality to acquire high-resolution volumetric images of patients for treatment localization purposes. However, in the current research regime, it lacks specific strategies for various sites on how to achieve the optimal patient setup and pertinent assessment of their dose consequence.

Most of the registration strategies are based upon the methodology of intensity matching between reference and localization images for 6 degree freedom shift, which is not always practical for all the clinical scenarios and even possess intrinsic flaws for some specific site. Meanwhile the relationship between the patient’s dose received from the treatment (beam delivery and CBCT scan itself) and setup alignment strategies had not been sufficiently addressed.

This work provided specific strategies for CBCT-guided setup procedures to achieve optimal dose effects for various sites as well as assess the dose consequence of those strategies. It includes the following works: 1.the assessment of the patient’s dose generated by CBCT scan itself, which involved with the investigation of the effect of CBCT on registration accuracy and image qualities with a reduced number of planar projections used in volumetric imaging reconstruction, 2. the investigation of the impact of small rotational errors on the magnitudes and distributions of spatial dose variations for intracranial stereotactic radiotherapy (SRT) treatment setups, 3. the development of a quick online evaluation method to assess the dose consequence due to small rotational error, 4. the invention of a novel method (centroid-to-centroid (CTC)) to facilitate the lung SBRT setup for translational-only scenarios in order to achieve optimal tumor dose coverage, 5. the assessment of CTC method’s performance on breathing variation scenarios using a phantom study.