I am a clinical professor in the Department of Human Oncology. My work focuses on treatment planning and quality assurance, areas in which I have made significant clinical academic and service accomplishments. I am currently the lead clinical TomoTherapy physicist and principle physicist on the UW Radixact research system, working on motion management strategies. In 2016 my teaching was recognized with a UW Alliant Energy Underkofler Excellence in Teaching Award. I developed a graduate treatment planning course and laboratory in 2002 and expanded it to include physics and MD residents. In 2015 and 2017, I traveled to China for the UW Top Physicist Development Project to teach for the collaborative UW–Madison and Tianjin University Medical Physics Master’s Degree program. I serve on PhD candidate and junior faculty mentoring committees and act as a liaison between the clinic and the graduate education program, promoting student clinical volunteer opportunities. I am also committed to physician, resident and dosimetry education. I have served as Physics Exam Section Chair for the ACR In-Training Radiation Oncology Exam. I served as the dosimetry supervisor and developed the clinical practicum for the UW–La Crosse Dosimetry Program at the UW Hospital, which began in 2014. In 2015, I was awarded a JCERT Certificate of Excellence Award for Clinical Educators. My interests are reflected in my AAPM involvement, serving on and chairing subcommittees under both education and professional councils. I am the AAPM liaison to the Medical Dosimetry Certification Board. I served as Chair of the AAPM SUFP and chaired MPPG #5a and currently serve on the Board of Directors and the Audit Committee. I am also an active member of the NC Chapter and served as treasurer/secretary.
PhD, University of Wisconsin–Madison, Medical Physics (2002)
MS, University of Wisconsin–Madison, Medical Physics (1999)
BS, University of Wyoming, Physics (1997)
BA, University of Vermont, Political Science (1992)
Director of Faculty Development and Academic Affairs, Human Oncology (2018)
Clinical Professor, Human Oncology (2018-pres.)
Clinical Associate Professor, Human Oncology, Medical Physics (2012–2018)
Clinical Assistant Professor, Human Oncology, Physics (2005–2012)
Selected Honors and Awards
University of Wisconsin Alliant Energy Underkofler Excellence in Teaching Award (2016)
Certificate of Excellence Award for Clinical Educators, JCERT (Joint Review Committee on Education in Radiologic Technology) (2015)
UW Academic Staff Professional Development Grant (2011)
UW Medical Education Development and Leadership (MEDAL) Teaching Faculty Development Program (2008)
UW Vilas Travel Grant (2001)
Student Travel Grant, Council on Ionizing Radiation Measurements and Standards (CIRMS) (1999)
Boards, Advisory Committees and Professional Organizations
Board of Directors, American Association of Physicists in Medicine (2017–present)
Member, Medical Dosimetry Certification Board (2015–present)
Member, American Association of Physicists in Medicine (1999–present)
Clinical Operations, Motion Management, MR-Guided Radiotherapy, TomoTherapy, Treatment Planning Systems
Effects of variable-width jaw motion on beam characteristics for Radixact Synchrony® Journal of applied clinical medical physics
Ferris WS, Culberson WS, Smilowitz JB, Bayouth JE
2021 May;22(5):175-181. doi: 10.1002/acm2.13234. Epub 2021 Mar 29.
PURPOSE: Radixact Synchrony corrects for target motion during treatment by adjusting the jaw and MLC positions in real time. As the jaws move off axis, Synchrony attempts to adjust for a loss in output due to the un-flattened 6 MV beam by increasing the jaw aperture width. The purpose of this work was to assess the impact of the variable-width aperture on delivered dose using measurements and simulations.
METHODS: Longitudinal beam profile measurements were acquired using an Edge diode with static gantry. Jaw-offset peak, width, and integral factors were calculated for profiles with the jaws in the extreme positions using both variable-width (Synchrony) and fixed-width apertures. Treatment plans with target motion and compensation were compared to planned doses to study the impact of the variable aperture on volumetric dose.
RESULTS: The jaw offset peak factor (JOPF) for the Synchrony jaw settings were 0.964 and 0.983 for the 1.0- and 2.5-cm jaw settings, respectively. These values decreased to 0.925 and 0.982 for the fixed-width settings, indicating that the peak value of the profile would decrease by 7.5% compared to centered if the aperture width was held constant. The IMRT dose distributions reveal similar results, where gamma pass rates are above tolerance for the Synchrony jaw settings but fall significantly for the fixed-width 1-cm jaws.
CONCLUSIONS: The variable-width behavior of Synchrony jaws provides a larger output correction for the 1-cm jaw setting. Without the variable-aperture correction, plans with the 1-cm jaw setting would underdose the target if the jaws spend a significant amount of time in the extreme positions. This work investigated the change in delivered dose with jaws in the extreme positions, therefore overall changes in dose due to offset jaws are expected to be less for composite treatment deliveries.
PMID:33779041 | PMC:PMC8130229 | DOI:10.1002/acm2.13234
View details for PubMedID 33779041
Evaluation of radixact motion synchrony for 3D respiratory motion: Modeling accuracy and dosimetric fidelity Journal of applied clinical medical physics
Ferris WS, Kissick MW, Bayouth JE, Culberson WS, Smilowitz JB
2020 Sep;21(9):96-106. doi: 10.1002/acm2.12978. Epub 2020 Jul 21.
The Radixact® linear accelerator contains the motion Synchrony system, which tracks and compensates for intrafraction patient motion. For respiratory motion, the system models the motion of the target and synchronizes the delivery of radiation with this motion using the jaws and multi-leaf collimators (MLCs). It was the purpose of this work to determine the ability of the Synchrony system to track and compensate for different phantom motions using a delivery quality assurance (DQA) workflow. Thirteen helical plans were created on static datasets from liver, lung, and pancreas subjects. Dose distributions were measured using a Delta4® Phantom+ mounted on a Hexamotion® stage for the following three case scenarios for each plan: (a) no phantom motion and no Synchrony (M0S0), (b) phantom motion and no Synchrony (M1S0), and (c) phantom motion with Synchrony (M1S1). The LEDs were placed on the Phantom+ for the 13 patient cases and were placed on a separate one-dimensional surrogate stage for additional studies to investigate the effect of separate target and surrogate motion. The root-mean-square (RMS) error between the Synchrony-modeled positions and the programmed phantom positions was <1.5 mm for all Synchrony deliveries with the LEDs on the Phantom+. The tracking errors increased slightly when the LEDs were placed on the surrogate stage but were similar to tracking errors observed for other motion tracking systems such as CyberKnife Synchrony. One-dimensional profiles indicate the effects of motion interplay and dose blurring present in several of the M1S0 plans that are not present in the M1S1 plans. All 13 of the M1S1 measured doses had gamma pass rates (3%/2 mm/10%T) compared to the planned dose > 90%. Only two of the M1S0 measured doses had gamma pass rates > 90%. Motion Synchrony offers a potential alternative to the current, ITV-based motion management strategy for helical tomotherapy deliveries.
PMID:32691973 | PMC:PMC7497925 | DOI:10.1002/acm2.12978
View details for PubMedID 32691973
Evaluation of a commercial Monte Carlo dose calculation algorithm for electron treatment planning Journal of applied clinical medical physics
Huang JY, Dunkerley D, Smilowitz JB
2019 Jun;20(6):184-193. doi: 10.1002/acm2.12622. Epub 2019 May 23.
The RayStation treatment planning system implements a Monte Carlo (MC) algorithm for electron dose calculations. For a TrueBeam accelerator, beam modeling was performed for four electron energies (6, 9, 12, and 15 MeV), and the dose calculation accuracy was tested for a range of geometries. The suite of validation tests included those tests recommended by AAPM's Medical Physics Practice Guideline 5.a, but extended beyond these tests in order to validate the MC algorithm in more challenging geometries. For MPPG 5.a testing, calculation accuracy was evaluated for square cutouts of various sizes, two custom cutout shapes, oblique incidence, and heterogenous media (cork). In general, agreement between ion chamber measurements and RayStation dose calculations was excellent and well within suggested tolerance limits. However, this testing did reveal calculation errors for the output of small cutouts. Of the 312 output factors evaluated for square cutouts, 20 (6.4%) were outside of 3% and 5 (1.6%) were outside of 5%, with these larger errors generally being for the smallest cutout sizes within a given applicator. Adjustment of beam modeling parameters did not fix these calculation errors, nor does the planning software allow the user to input correction factors as a function of field size. Additional validation tests included several complex phantom geometries (triangular nose phantom, lung phantom, curved breast phantom, and cortical bone phantom), designed to test the ability of the algorithm to handle high density heterogeneities and irregular surface contours. In comparison to measurements with radiochromic film, RayStation showed good agreement, with an average of 89.3% pixels passing for gamma analysis (3%/3mm) across four phantom geometries. The MC algorithm was able to accurately handle the presence of irregular surface contours (curved cylindrical phantom and a triangular nose phantom), as well as heterogeneities (cork and cortical bone).
PMID:31120615 | PMC:PMC6560228 | DOI:10.1002/acm2.12622
View details for PubMedID 31120615
Long-term dosimetric stability of multiple TomoTherapy delivery systems Journal of applied clinical medical physics
Smilowitz JB, Dunkerley D, Hill PM, Yadav P, Geurts MW
2017 May;18(3):137-143. doi: 10.1002/acm2.12085. Epub 2017 May 2.
The dosimetric stability of six TomoTherapy units was analyzed to investigate changes in performance over time and with system upgrades. Energy and output were tracked using monitor chamber signal, onboard megavoltage computed tomography (MVCT) detector profile, and external ion chamber measurements. The systems (and monitoring periods) include three Hi-Art (67, 61, and 65 mos.), two TomoHDA (31 and 26 mos.), and one Radixact unit (11 mos.), representing approximately 10 years of clinical use. The four newest systems use the Dose Control Stability (DCS) system and Fixed Target Linear Accelerator (linac) (FTL). The output stability is reported as deviation from reference monitor chamber signal for all systems and/or from an external chamber signal. The energy stability was monitored using relative (center versus off-axis) MVCT detector signal (beam profile) and/or the ratio of chamber measurements at 2 depths. The clinical TomoHDA data were used to benchmark the Radixact stability, which has the same FTL but runs at a higher dose rate. The output based on monitor chamber data of all systems is very stable. The standard deviation of daily output on the non-DCS systems was 0.94-1.52%. As expected, the DCS systems had improved standard deviation: 0.004-0.06%. The beam energy was also very stable for all units. The standard deviation in profile flatness was 0.23-0.62% for rotating target systems and 0.04-0.09% for FTL. Ion chamber output and PDD ratios supported these results. The output stability on the Radixact system during extended treatment delivery (20, 30, and 40 min) was comparable to a clinical TomoHDA system. For each system, results are consistent between different measurement tools and techniques, proving not only the dosimetric stability, but also these quality parameters can be confirmed with various metrics. The replacement history over extended time periods of the major dosimetric components of the different delivery systems (target, linac, and magnetron) is also reported.
PMID:28464517 | PMC:PMC5689853 | DOI:10.1002/acm2.12085
View details for PubMedID 28464517
Implementation of the validation testing in MPPG 5.a "Commissioning and QA of treatment planning dose calculations-megavoltage photon and electron beams" Journal of applied clinical medical physics
Jacqmin DJ, Bredfeldt JS, Frigo SP, Smilowitz JB
2017 Jan;18(1):115-127. doi: 10.1002/acm2.12015. Epub 2016 Dec 5.
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.
PMID:28291929 | PMC:PMC5689890 | DOI:10.1002/acm2.12015
View details for PubMedID 28291929
AAPM Medical Physics Practice Guideline 5.a.: Commissioning and QA of Treatment Planning Dose Calculations - Megavoltage Photon and Electron Beams Journal of applied clinical medical physics
Smilowitz JB, Das IJ, Feygelman V, Fraass BA, Kry SF, Marshall IR, Mihailidis DN, Ouhib Z, Ritter T, Snyder MG, Fairobent L, Group GT
2015 Sep 8;16(5):14–34. doi: 10.1120/jacmp.v16i5.5768.
The American Association of Physicists in Medicine (AAPM) is a nonprofit professional society whose primary purposes are to advance the science, education and professional practice of medical physics. The AAPM has more than 8,000 members and is the principal organization of medical physicists in the United States. The AAPM will periodically define new practice guidelines for medical physics practice to help advance the science of medical physics and to improve the quality of service to patients throughout the United States. Existing medical physics practice guidelines will be reviewed for the purpose of revision or renewal, as appropriate, on their fifth anniversary or sooner. Each medical physics practice guideline represents a policy statement by the AAPM, has undergone a thorough consensus process in which it has been subjected to extensive review, and requires the approval of the Professional Council. The medical physics practice guidelines recognize that the safe and effective use of diagnostic and therapeutic radiology requires specific training, skills, and techniques, as described in each document. Reproduction or modification of the published practice guidelines and technical standards by those entities not providing these services is not authorized. The following terms are used in the AAPM practice guidelines:• Must and Must Not: Used to indicate that adherence to the recommendation is considered necessary to conform to this practice guideline.• Should and Should Not: Used to indicate a prudent practice to which exceptions may occasionally be made in appropriate circumstances.
PMID:26699330 | PMC:PMC5690154 | DOI:10.1120/jacmp.v16i5.5768
View details for PubMedID 26699330
Monte Carlo simulations of patient dose perturbations in rotational-type radiotherapy due to a transverse magnetic field: a tomotherapy investigation Medical physics
Yang YM, Geurts M, Smilowitz JB, Sterpin E, Bednarz BP
2015 Feb;42(2):715-25. doi: 10.1118/1.4905168.
PURPOSE: Several groups are exploring the integration of magnetic resonance (MR) image guidance with radiotherapy to reduce tumor position uncertainty during photon radiotherapy. The therapeutic gain from reducing tumor position uncertainty using intrafraction MR imaging during radiotherapy could be partially offset if the negative effects of magnetic field-induced dose perturbations are not appreciated or accounted for. The authors hypothesize that a more rotationally symmetric modality such as helical tomotherapy will permit a systematic mediation of these dose perturbations. This investigation offers a unique look at the dose perturbations due to homogeneous transverse magnetic field during the delivery of Tomotherapy(®) Treatment System plans under varying degrees of rotational beamlet symmetry.
METHODS: The authors accurately reproduced treatment plan beamlet and patient configurations using the Monte Carlo code geant4. This code has a thoroughly benchmarked electromagnetic particle transport physics package well-suited for the radiotherapy energy regime. The three approved clinical treatment plans for this study were for a prostate, head and neck, and lung treatment. The dose heterogeneity index metric was used to quantify the effect of the dose perturbations to the target volumes.
RESULTS: The authors demonstrate the ability to reproduce the clinical dose-volume histograms (DVH) to within 4% dose agreement at each DVH point for the target volumes and most planning structures, and therefore, are able to confidently examine the effects of transverse magnetic fields on the plans. The authors investigated field strengths of 0.35, 0.7, 1, 1.5, and 3 T. Changes to the dose heterogeneity index of 0.1% were seen in the prostate and head and neck case, reflecting negligible dose perturbations to the target volumes, a change from 5.5% to 20.1% was observed with the lung case.
CONCLUSIONS: This study demonstrated that the effect of external magnetic fields can be mitigated by exploiting a more rotationally symmetric treatment modality.
PMID:25652485 | PMC:PMC4297282 | DOI:10.1118/1.4905168
View details for PubMedID 25652485
AAPM Medical Physics Practice Guideline 2.a: Commissioning and quality assurance of X-ray-based image-guided radiotherapy systems Journal of applied clinical medical physics
Fontenot JD, Alkhatib H, Garrett JA, Jensen AR, McCullough SP, Olch AJ, Parker BC, Yang CJ, Fairobent LA, Staff A
2014 Jan 6;15(1):4528. doi: 10.1120/jacmp.v15i1.4528.
The American Association of Physicists in Medicine (AAPM) is a nonprofit professional society whose primary purposes are to advance the science, education, and professional practice of medical physics. The AAPM has more than 8,000 members and is the principal organization of medical physicists in the United States.
The AAPM will periodically define new practice guidelines for medical physics practice to help advance the science of medical physics and to improve the quality of service to patients throughout the United States. Existing medical physics practice guidelines will be reviewed for the purpose of revision or renewal, as appropriate, on their fifth anniversary or sooner.
Each medical physics practice guideline represents a policy statement by the AAPM, has undergone a thorough consensus process in which it has been subjected to extensive review, and requires the approval of the Professional Council. The medical physics practice guidelines recognize that the safe and effective use of diagnostic and therapeutic radiology requires specific training, skills, and techniques, as described in each document. Reproduction or modification of the published practice guidelines and technical standards by those entities not providing these services is not authorized.
PMID:24423852 | PMC:PMC5711227 | DOI:10.1120/jacmp.v15i1.4528
View details for PubMedID 24423852
Report on the American Association of Medical Physics Undergraduate Fellowship Programs Journal of applied clinical medical physics
Smilowitz JB, Avery S, Gueye P, Sandison GA
2013 Jan 7;14(1):4159. doi: 10.1120/jacmp.v14i1.4159.
The American Association of Physicists in Medicine (AAPM) sponsors two summer undergraduate research programs to attract top performing undergraduate students into graduate studies in medical physics: the Summer Undergraduate Fellowship Program (SUFP) and the Minority Undergraduate Summer Experience (MUSE). Undergraduate research experience (URE) is an effective tool to encourage students to pursue graduate degrees. The SUFP and MUSE are the only medical physics URE programs. From 2001 to 2012, 148 fellowships have been awarded and a total of $608,000 has been dispersed to fellows. This paper reports on the history, participation, and status of the programs. A review of surveys of past fellows is presented. Overall, the fellows and mentors are very satisfied with the program. The efficacy of the programs is assessed by four metrics: entry into a medical physics graduate program, board certification, publications, and AAPM involvement. Sixty-five percent of past fellow respondents decided to pursue a graduate degree in medical physics as a result of their participation in the program. Seventy percent of respondents are currently involved in some educational or professional aspect of medical physics. Suggestions for future enhancements to better track and maintain contact with past fellows, expand funding sources, and potentially combine the programs are presented.
PMID:23318397 | PMC:PMC5714055 | DOI:10.1120/jacmp.v14i1.4159
View details for PubMedID 23318397
A feasible method for clinical delivery verification and dose reconstruction in tomotherapy Medical physics
Kapatoes JM, Olivera GH, Ruchala KJ, Smilowitz JB, Reckwerdt PJ, Mackie TR
2001 Apr;28(4):528-42. doi: 10.1118/1.1352579.
Delivery verification is the process in which the energy fluence delivered during a treatment is verified. This verified energy fluence can be used in conjunction with an image in the treatment position to reconstruct the full three-dimensional dose deposited. A method for delivery verification that utilizes a measured database of detector signal is described in this work. This database is a function of two parameters, radiological path-length and detector-to-phantom distance, both of which are computed from a CT image taken at the time of delivery. Such a database was generated and used to perform delivery verification and dose reconstruction. Two experiments were conducted: a simulated prostate delivery on an inhomogeneous abdominal phantom, and a nasopharyngeal delivery on a dog cadaver. For both cases, it was found that the verified fluence and dose results using the database approach agreed very well with those using previously developed and proven techniques. Delivery verification with a measured database and CT image at the time of treatment is an accurate procedure for tomotherapy. The database eliminates the need for any patient-specific, pre- or post-treatment measurements. Moreover, such an approach creates an opportunity for accurate, real-time delivery verification and dose reconstruction given fast image reconstruction and dose computation tools.
PMID:11339750 | DOI:10.1118/1.1352579
View details for PubMedID 11339750
Jennifer Smilowitz, PhDClinical Science Center 600 Highland Avenue, K4/b51, 0600,
Madison, WI 53792