I am an assistant professor in the Department of Human Oncology with roles in the clinic, research and teaching. In the clinic, I focus primarily on the clinical applications of the TrueBeam radiotherapy platform. This includes preparation of the treatment machine for clinical use, ongoing quality assurance, involvement in the radiosurgery program and implementation of motion management techniques, such as respiratory gating and optical surface imaging.
My research has focused on the TrueBeam radiotherapy platform as well. This has included studying the commissioning and validation of treatment planning dose calculations for a TrueBeam radiotherapy accelerator. I have also studied performance of the TrueBeam system for low-dose-rate delivery. I am also interested in quantifying the performance of optical surface imaging systems used for patient positioning. The goal of all of this work is to make treatment delivery on the TrueBeam radiotherapy platform as versatile and accurate as possible.
In addition to my clinical and research roles, I teach graduate students, medical students and residents. My goal is to create an environment in which students can develop a more concrete understanding of the fundamental physics that underlie the radiation therapy process while also developing the interpersonal skills needed to succeed in a dynamic, multi-disciplinary clinical environment.
Fellowship, Medical University of South Carolina, Radiation Oncology Physics (2015)
Resident, Medical University of South Carolina, Radiation Oncology Physics (2014)
PhD, University of Wisconsin–Madison, Medical Physics (2012)
MS, University of Wisconsin–Madison, Medical Physics (2008)
BS, University of Wisconsin–Madison, Nuclear Engineering and Engineering Physics (2007)
Assistant Professor, Human Oncology (2015)
Selected Honors and Awards
2nd Place–Young Investigator Symposium at AAPM Spring Clinical Meeting (2014)
Graduate Fellowship, American Association of Physicists in Medicine (2008)
Fred W. and Josephine H. Colbeck Scholarship Award (2006)
Max W. Carbon Scholarship in Nuclear Technology (2005)
Kurt F. Wendt Junior Scholarship (2005)
Department of Engineering Physics Nuclear Engineering Scholarship (2004)
Ernest J. Laine Outstanding Sophomore Engineering Student Scholarship (2004)
Boards, Advisory Committees and Professional Organizations
American Association of Physicists in Medicine (2007-pres.)
American College of Radiology (2013-pres.)
Medical Physics Residency Program Oversight Committee (2016-pres.)
Equipment Donation Sub-Committee of the AAPM/IOMP (2016-pres.)
Motion Management, Radiation Measurements, Radiosurgery, Treatment Planning Systems
Continuous improvement is the cornerstone of high-quality radiation therapy.
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.
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.
Validation of a modern second-check dosimetry system using a novel verification phantom. J Appl Clin Med Phys
McDonald DG, Jacqmin DJ, Mart CJ, Koch NC, Peng JL, Ashenafi MS, Fugal MA, Vanek KN
2017 Jan; 18 (1): 170-177
PURPOSE: To evaluate the Mobius second-check dosimetry system by comparing it to ionization-chamber dose measurements collected in the recently released Mobius Verification Phantom™ (MVP). For reference, a comparison of these measurements to dose calculated in the primary treatment planning system (TPS), Varian Eclipse with the AcurosXB dose algorithm, is also provided. Finally, patient dose calculated in Mobius is compared directly to Eclipse to demonstrate typical expected results during clinical use of the Mobius system.
METHODS: Seventeen anonymized intensity-modulated clinical treatment plans were selected for analysis. Dose was recalculated on the MVP in both Eclipse and Mobius. These calculated doses were compared to doses measured using an A1SL ionization-chamber in the MVP. Dose was measured and analyzed at two different chamber positions for each treatment plan. Mobius calculated dose was then compared directly to Eclipse using the following metrics; target mean dose, target D95%, global 3D gamma pass rate, and target gamma pass rate. Finally, these same metrics were used to analyze the first 36 intensity modulated cases, following clinical implementation of the Mobius system.
RESULTS: The average difference between Mobius and measurement was 0.3 ± 1.3%. Differences ranged from -3.3 to + 2.2%. The average difference between Eclipse and measurement was -1.2 ± 0.7%. Eclipse vs. measurement differences ranged from -3.0 to -0.1%. For the 17 anonymized pre-clinical cases, the average target mean dose difference between Mobius and Eclipse was 1.0 ± 1.1%. Average target D95% difference was -0.9 ± 2.0%. Average global gamma pass rate, using a criteria of 3%, 2 mm, was 94.4 ± 3.3%, and average gamma pass rate for the target volume only was 80.2 ± 12.3%. Results of the first 36 intensity-modulated cases, post-clinical implementation of Mobius, were similar to those seen for the 17 pre-clinical test cases.
CONCLUSION: Mobius correctly calculated dose for each tested intensity modulated treatment plan, agreeing with measurement to within 3.5% for all cases analyzed. The dose calculation accuracy and independence of the Mobius system is sufficient to provide a rigorous second-check of a modern TPS.View details for PubMedID 28291938
Implementation of the validation testing in MPPG 5.a "Commissioning and QA of treatment planning dose calculations-megavoltage photon and electron beams". J Appl Clin Med Phys
Jacqmin DJ, Bredfeldt JS, Frigo SP, Smilowitz JB
2017 Jan; 18 (1): 115-127
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. This work discusses the implementation of the validation testing recommended in MPPG 5.a at two institutions. The two institutions worked collaboratively to create a common set of treatment fields and analysis tools to deliver and analyze the validation tests. 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). Overall, the validation testing recommended in MPPG 5.a took approximately 79 person-hours for a machine with four photon and five electron energies for a single TPS. Of the 79 person-hours, 26 person-hours required time on the machine, and the remainder involved preparation and analysis. The basic photon, electron, and heterogeneity correction tests were evaluated with the tolerances in MPPG 5.a, and the tolerances were met for all tests. The MPPG 5.a evaluation criteria were used to assess the small field and IMRT/VMAT validation tests. Both institutions found the use of MPPG 5.a to be a valuable resource during the commissioning process. The validation testing in MPPG 5.a showed the strengths and limitations of the TPS models. In addition, the data collected during the validation testing is useful for routine QA of the TPS, validation of software upgrades, and commissioning of new algorithms.View details for PubMedID 28291929
RIP1 and RIP3 complex regulates radiation-induced programmed necrosis in glioblastoma. Tumour Biol
Das A, McDonald DG, Dixon-Mah YN, Jacqmin DJ, Samant VN, Vandergrift WA, Lindhorst SM, Cachia D, Varma AK, Vanek KN, Banik NL, Jenrette JM, Raizer JJ, Giglio P, Patel SJ
2016 Jun; 37 (6): 7525-34
Radiation-induced necrosis (RN) is a relatively common side effect of radiation therapy for glioblastoma. However, the molecular mechanisms involved and the ways RN mechanisms differ from regulated cell death (apoptosis) are not well understood. Here, we compare the molecular mechanism of cell death (apoptosis or necrosis) of C6 glioma cells in both in vitro and in vivo (C6 othotopically allograft) models in response to low and high doses of X-ray radiation. Lower radiation doses were used to induce apoptosis, while high-dose levels were chosen to induce radiation necrosis. Our results demonstrate that active caspase-8 in this complex I induces apoptosis in response to low-dose radiation and inhibits necrosis by cleaving RIP1 and RI. When activation of caspase-8 was reduced at high doses of X-ray radiation, the RIP1/RIP3 necrosome complex II is formed. These complexes induce necrosis through the caspase-3-independent pathway mediated by calpain, cathepsin B/D, and apoptosis-inducing factor (AIF). AIF has a dual role in apoptosis and necrosis. At high doses, AIF promotes chromatinolysis and necrosis by interacting with histone H2AX. In addition, NF-κB, STAT-3, and HIF-1 play a crucial role in radiation-induced inflammatory responses embedded in a complex inflammatory network. Analysis of inflammatory markers in matched plasma and cerebrospinal fluid (CSF) isolated from in vivo specimens demonstrated the upregulation of chemokines and cytokines during the necrosis phase. Using RIP1/RIP3 kinase specific inhibitors (Nec-1, GSK'872), we also establish that the RIP1-RIP3 complex regulates programmed necrosis after either high-dose radiation or TNF-α-induced necrosis requires RIP1 and RIP3 kinases. Overall, our data shed new light on the relationship between RIP1/RIP3-mediated programmed necrosis and AIF-mediated caspase-independent programmed necrosis in glioblastoma.View details for PubMedID 26684801
Complement-dependent modulation of antitumor immunity following radiation therapy. Cell Rep
Elvington M, Scheiber M, Yang X, Lyons K, Jacqmin D, Wadsworth C, Marshall D, Vanek K, Tomlinson S
2014 Aug 07; 8 (3): 818-30
Complement is traditionally thought of as a proinflammatory effector mechanism of antitumor immunity. However, complement is also important for effective clearance of apoptotic cells, which can be an anti-inflammatory and tolerogenic process. We show that localized fractionated radiation therapy (RT) of subcutaneous murine lymphoma results in tumor cell apoptosis and local complement activation. Cotreatment of mice with tumor-targeted complement inhibition markedly improved therapeutic outcome of RT, an effect linked to early increases in apoptotic cell numbers and increased inflammation. Improved outcome was dependent on an early neutrophil influx and was characterized by increased numbers of mature dendritic cells and the subsequent modulation of T cell immunity. Appropriate complement inhibition may be a promising strategy to enhance a mainstay of treatment for cancer.View details for PubMedID 25066124
Dustin Jacqmin, PhD600 Highland Avenue,
Madison, WI 53792