Encrypted login | home

Program Information

Clinical Implementation of the New Dosimetry System for TomoTherapy Patient Delivery Quality Assurance (DQA)

E Chung

E Chung*, D Kwon , T Park , H Kang , Y Chung , Samsung Medical Center, Seoul, KR


SU-I-GPD-T-288 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: The delivery quality assurance (DQA) of intensity-modulated radiotherapy (IMRT) plans is a pre-requisite for ensuring patient treatments. This work investigated the clinical usefulness of a new DQA system, Dosimetry Check™ (DC), on tomotherapy-based IMRT plans.

Methods: The DQA was performed for 14 different TomoTherapy®-based clinical treatment plans. In treatment machines, a couch position was set to a 400 mm height and the plan was delivered using QA-Treatment mode. For each treatment plan, the treatment plan data and the measured beam fluence using the TomoTherapy® detector were transferred to a DC-installed computer. Then, the DC reconstructed the 3-D dose distribution to the patient CT images. The recalculated dose distribution was compared with the TomoTherapy® treatment planning system-calculated one in an absolute dose, 2-D plane and 3-D volume. The DQA results were compared with those performed using the cheese phantom with ion chamber and film.

Results: For 11 out of 14 treatment plans, for the both DQA methods, the absolute dose difference between the measurement and calculation was less than 3% and the gamma pass rate with the 3%/3mm criteria was greater than 95%. The p-value calculated using Wilcoxon signed-rank test was 0.177, which implies no statistically significant difference between the two methods in determining the absolute dose difference. For treatment plans presenting the complexity or having the target positioned inside or near bone, the dose difference was greater than 3% or the gamma pass rate was less than 95% with the DC, while the DQA results with the cheese phantom passed our tolerance.

Conclusion: We have clinically implemented the DC for the DQA of TomoTherapy® treatment plans. The DC carried out the accurate DQA results as performed with the cheese phantom. This new DQA system provided more information in verifying the dose delivery to patients, while simplifying the DQA process.

Contact Email: