research profile
Dr. Dustin Jacqmin’s Research
Patient safety and quality improvement, motion management, radiosurgery, small field dosimetry.
During my time at UW, I have worked with my colleagues to implement new treatment techniques and motion management technologies on the TrueBeam radiotherapy platform. The goal of my work is to improve the accuracy of treatment delivery and provide valuable new treatment modalities to my physician partners.
Last updated:
Introduction of 6 MV Flattening Filter Free Photon Beams
The physics team in the Department of Human Oncology has prepared a new treatment modality for fractionated stereotactic radiotherapy (FSRT) and stereotactic body radiotherapy (SBRT) on our Varian TrueBeam linear accelerators. This modality is a different kind of photon beam without a flattening filter—known as “flattening filter free” or FFF beams. Unlike the beams we have used in the past, these beams do not emerge from the machine with a uniform intensity throughout the field. This lack of uniform intensity, considered to be disadvantageous for conventional radiotherapy, is desirable for FSRT and SBRT. Even better: The removal of the flattening filter increases the dose rate up to a factor of four, allowing us to deliver these high-dose-per-fraction treatments in much less time. The physics team has worked hard to ensure that these beams are accurate for the small targets commonly treated with FSRT and SBRT.
Evaluating low-dose-rate performance of the TrueBeam radiotherapy system
During the commissioning of our new TrueBeam linear accelerator, we investigated the dose rate constancy, MU linearity and profile stability of the TrueBeam radiotherapy delivery system over its full range of available dose rates. The verification of dose-rate constancy, MU linearity and profile stability of the TrueBeam radiotherapy system has clinical relevance for a number of treatment delivery techniques. Dose-rate constancy is important for volumetric modulated arc therapy (VMAT), which modulates the dose rate over the range of available dose rates during arc delivery. Dose-rate constancy at very low dose rates (5-20 MU/min) allows pulsed reduced-dose-rate radiotherapy (PRDR) treatments to be delivered continuously rather than in pulses. Dose-rate constancy at very low dose rates also allows VMAT to be used for PRDR treatments. Finally, the verification of MU linearity down to 2 MU gives greater confidence that small MU segments can be used for intensity modulated radiation therapy (IMRT) and field-in-field delivery.
Evaluating the performance of the optical surface imaging systems
Optical surface imaging systems like AlignRT and the Varian Optical Surface Monitoring System (OSMS) are often used for monitoring patients during frameless stereotactic radiosurgery (SRS). This type of radiotherapy procedure demands sub-millimeter accuracy from the system in order to verify that the patient is within allowable treatment margins during treatment. Optical surface imaging systems are known to exhibit spatial drift during warm-up of the equipment. We investigated the spatial drift of the OSMS system, and our work shows that different warm-up scenarios produce different spatial drift behavior. As a result of this work, we know how to eliminate spatial drift so that it can be used for frameless SRS.
Implementation of the validation testing in MPPG 5.a
The AAPM Medical Physics Practice Guideline (MPPG) 5.a provides concise guidance on the commissioning and QA of beam modeling and dose calculation in radiotherapy treatment planning systems. We worked with physicists at multiple institutions to create a common set of treatment fields and analysis tools to deliver and analyze the validation tests in MPPG 5.a. This included the development of a novel, open-source software tool to compare scanning water tank measurements to 3D DICOM-RT Dose distributions. Dose calculation algorithms in both Pinnacle and Eclipse were tested with MPPG 5.a to validate the modeling of Varian TrueBeam linear accelerators. The validation process resulted in more than 200 water tank scans and more than 50 point measurements per institution, each of which was compared to a dose calculation from the institution’s treatment planning system (TPS). We found the use of MPPG 5.a to be a valuable resource during the commissioning process. We reported our findings in JACMP and have made our tools available to the wider physics community.
