Mark Oldham

Overview:

Dr Oldham is Professor in the Department of Radiation Oncology (primary) and Biomedical Engineering (Secondary). He is the Director of the Optical Biophysics and 3D Dosimetry Lab. The lab has received NIH R01 funding to develop optical imaging techniques for 3D dosimetry. We are also developing a new optical imaging technique for high-resolution 3D imaging of vascular networks and gene expression in unsectioned tissue samples. A range of applications are being explored through collaborations with the Dept of Radiobiology (Prof Mark Dewhirst).  In addition to these efforts, the Lab is heavily involved in several research projects aimed at modifying radiation treatments in order to stimulate a long term anti-cancer immune response: radiation and immunotherapy. 

Dr Oldham is the Director of the Radiation Therapy Track of the Duke Medical Physics MS/PhD program.

Positions:

Professor of Radiation Oncology

Radiation Oncology
School of Medicine

Member of the Duke Cancer Institute

Duke Cancer Institute
School of Medicine

Education:

Ph.D. 1991

Newcastle University (United Kingdom)

Grants:

A practical and versatile high-resolution 3D dosimetry system for clinical use

Administered By
Radiation Oncology
Awarded By
Heuris, Inc.
Role
Principal Investigator
Start Date
End Date

An investigation of the dosimetry of the ViewRay radiation therapy system

Administered By
Radiation Oncology
Awarded By
Washington University in St. Louis
Role
Principal Investigator
Start Date
End Date

Publications:

A method for generating intensity-modulated radiation therapy fields for small animal irradiators utilizing 3D-printed compensator molds.

PURPOSE: The purpose of this study was to investigate the feasibility of using fused deposition modeling (FDM) three-dimensional (3D) printer to generate radiation compensators for high-resolution (~1 mm) intensity-modulated radiation therapy (IMRT) for small animal radiation treatment. We propose a novel method incorporating 3D-printed compensator molds filled with NaI powder. METHODS: The inverse planning module of the computational environment for radiotherapy research (CERR) software was adapted to simulate the XRAD-225Cx irradiator, both geometry and kV beam quality (the latter using a phase space file provided for XRAD-225Cx). A nine-field IMRT treatment was created for a scaled-down version of the imaging and radiation oncology core (IROC) Head and Neck IMRT credentialing test, recreated on a 2.2-cm-diameter cylindrical phantom. Optimized fluence maps comprising nine fields and a total of 2564 beamlets were calculated at resolution of 1.25 × 1.25 mm2 . A hollow compensator mold was created (using in-house software and algorithm) for each field using 3D printing with polylactic acid (PLA) filaments. The molds were then packed with sodium iodide powder (NaI, measured density ρNaI  = 2.062 g/cm3 ). The mounted compensator mold thickness was limited to 13.8 mm due to clearance issues with couch collision. At treatment delivery, each compensator was manually mounted to a customized block tray attached to the reference 40 × 40 mm2 collimator. Compensator reproducibility among three repeated 3D-printed molds was measured with Radiochromic EBT2 film. The two-dimensional (2D) dose distributions of the nine fields were compared to calculated 2D doses from CERR using gamma comparisons with distance-to-agreement criteria of 0.5-0.25 mm and dose difference criteria of 3-5%. RESULTS: Good reproducibility of 3D-printed compensator manufacture was observed with mean error of ±0.024 Gy and relative dose error of ±4.2% within the modulated part of the beam. Within the limit of 13.8 mm compensator height, a maximum radiation blocking efficiency of 91.5% was achieved. Per field, about 45.5 g of NaI powder was used. Gamma analysis on each of the nine delivered IMRT fields using radiochromic films resulted in eight of nine treatment fields with >90% pass rate with 5%/0.5 mm tolerances. However, low gamma passing rate of 49-66% (3%/0.25 mm to 5%/0.5 mm) was noted in one field, attributed to fabrication errors resulting in over-filling the mold. The nine-field treatment plan was delivered in under 30 min with no mechanical or collisional issues. CONCLUSIONS: We show the feasibility of high spatial resolution IMRT treatment on a small animal irradiator utilizing 3D-printed compensator shells packed with NaI powder. Using the PLA mold with NaI powder was attractive due to the ease of 3D printing a PLA mold at high geometric resolution and the well-balanced attenuation properties of NaI powders that prevented the mold from becoming too bulky. IMRT fields with 1.25-mm resolution are capable with significant fluence modulation with relative dose accuracy of ±4.2%.
Authors
Yoon, SW; Kodra, J; Miles, DA; Kirsch, DG; Oldham, M
MLA Citation
URI
https://scholars.duke.edu/individual/pub1437206
PMID
32281657
Source
pubmed
Published In
Med Phys
Published Date
DOI
10.1002/mp.14175

Comprehensive radiation and imaging isocenter verification using NIPAM kV-CBCT dosimetry.

PURPOSE: To develop and demonstrate a comprehensive method to directly measure radiation isocenter uncertainty and coincidence with the cone-beam computed tomography (kV-CBCT) imaging coordinate system that can be carried out within a typical quality assurance (QA) time slot. METHODS: An N-isopropylacrylamide (NIPAM) three-dimensional (3D) dosimeter for which dose is observed as increased electron density in kV-CBCT is irradiated at eight couch/gantry combinations which enter the dosimeter at unique orientations. One to three CBCTs are immediately acquired, radiation profile is detected per beam, and displacement from imaging isocenter is quantified. We performed this test using a 5 mm diameter MLC field, and 7.5 and 4 mm diameter cones, delivering approximately 16 Gy per beam. CBCT settings were 1035-4050 mAs, 80-125 kVs, smooth filter, 1 mm slice thickness. The two-dimensional (2D) displacement of each beam from the imaging isocenter was measured within the planning system, and Matlab code developed in house was used to quantify relevant parameters based on the actual beam geometry. Detectability of the dose profile in the CBCT was quantified as the contrast-to-noise ratio (CNR) of the irradiated high-dose regions relative to the surrounding background signal. Our results were compared to results determined by the traditional Winston-Lutz test, film-based "star shots," and the vendor provided machine performance check (MPC). The ability to detect alignment errors was demonstrated by repeating the test after applying a 0.5 mm shift to the MLCs in the direction of leaf travel. In addition to radiation isocenter and coincidence with CBCT origin, the analysis also calculated the actual gantry and couch angles per beam. RESULTS: Setup, MV irradiation, and CBCT readout were carried out within 38 min. After subtracting the background signal from the pre-CBCT, the CNR of the dosimeter signal from the irradiation with the MLCs (125 kVp, 1035 mAs, n = 3), 7.5 mm cone (125 kVp, 1035 mAs, n = 3), and 4 mm cone (80 kVp, 4050 mAs, n = 1) was 5.4, 5.9, and 2.9, respectively. The minimum radius that encompassed all beams calculated using the automated analysis was 0.38, 0.48, and 0.44 mm for the MLCs, 7.5 mm cone, and 4 mm cone, respectively. When determined manually, these values were slightly decreased at 0.28, 0.41, and 0.40 mm. For comparison, traditional Winston-Lutz test with MLCs and MPC measured the 3D isocenter radius to be 0.24 mm. Lastly, when a 0.5 mm shift to the MLCs was applied, the smallest radius that intersected all beams increased from 0.38 to 0.90 mm. The mean difference from expected value for gantry angle was 0.19 ± 0.29°, 0.17 ± 0.23°, and 0.12 ± 0.14° for the MLCs, 7.5 mm cone, and 4 mm cone, respectively. The mean difference from expected for couch angle was -0.07 ± 0.28°, -0.08 ± 0.66°, and 0.04 ± 0.25°. CONCLUSIONS: This work demonstrated the feasibility of a comprehensive isocenter verification using a NIPAM dosimeter with sub-mm accuracy which incorporates evaluation of coincidence with imaging coordinate system, and may be applicable to all SRS cones as well as MLCs.
Authors
Pant, K; Umeh, C; Oldham, M; Floyd, S; Giles, W; Adamson, J
MLA Citation
Pant, Kiran, et al. “Comprehensive radiation and imaging isocenter verification using NIPAM kV-CBCT dosimetry.Med Phys, vol. 47, no. 3, Mar. 2020, pp. 927–36. Pubmed, doi:10.1002/mp.14008.
URI
https://scholars.duke.edu/individual/pub1427239
PMID
31899806
Source
pubmed
Published In
Med Phys
Volume
47
Published Date
Start Page
927
End Page
936
DOI
10.1002/mp.14008

Evaluation of UVA emission from x-ray megavoltage-irradiated tissues and phantoms.

RECA (Radiotherapy enhanced with Cherenkov photo-activation) is a proposed treatment where the anti-cancer drug psoralen is photo-activated in situ by UVA (Ultraviolet A, 320-400 nm) Cherenkov light (CL) produced directly by the treatment beam itself. In this study, we develop a UVA-imaging technique to quantify relative UVA CL produced by bulk tissues and other phantoms upon clinical x-ray megavoltage irradiation. UVA CL emission (320-400 nm) was quantified in tissue samples of porcine and poultry and in two kinds of solid waters (SW): brown (Virtual Waters, Standard Imaging, WI) and white (Diagnostic Therapy, CIRS, VA), and in 1% agarose gels variously doped with absorbing dye. Quantification was achieved through cumulative imaging of the samples placed in a dark, light-blocking chamber during irradiation on a Varian 21 EX accelerator. UVA imaging required a specialized high-sensitivity cooled camera equipped with UVA lenses and a filter. At 15 MV, white SW emitted [Formula: see text], [Formula: see text] and [Formula: see text] less UVA than chicken breast, pork loin and pork belly, respectively. Similar under-response was observed at 6 MV. Brown SW had [Formula: see text] less UVA emission than white SW at 15 MV, and negligible emission at 6 MV. Agarose samples (1% by weight) doped with 250 ppm India ink exhibited equivalent UVA CL emission to chicken breast (within 8%). The results confirm that for the same absorbed dose, SW emits less UVA light than the tissue samples, indicating that prior in vitro studies utilizing SW as the CL-generating source may have underestimated the RECA therapeutic effect. Agarose doped with 250 ppm India ink is a convenient tissue-equivalent phantom for further work.
Authors
Jain, S; Yoon, SW; Zhang, X; Adamson, J; Floyd, S; Oldham, M
MLA Citation
Jain, Sagarika, et al. “Evaluation of UVA emission from x-ray megavoltage-irradiated tissues and phantoms.Phys Med Biol, vol. 64, no. 22, Nov. 2019, p. 225017. Pubmed, doi:10.1088/1361-6560/ab4333.
URI
https://scholars.duke.edu/individual/pub1409900
PMID
31505474
Source
pubmed
Published In
Phys Med Biol
Volume
64
Published Date
Start Page
225017
DOI
10.1088/1361-6560/ab4333

An investigation of a novel reusable radiochromic sheet for 2D dose measurement.

PURPOSE: Radiochromic film remains a useful and versatile clinical dosimetry tool. Current film options are single use. Here, we introduce a novel prototype two-dimensional (2D) radiochromic sheet, which optically clears naturally at room temperature after irradiation and can be reused. We evaluate the sheets for potential as a 2D dosimeter and as a radiochromic bolus with capability for dose measurement. METHODS: A novel derivative of reusable Presage® was manufactured into thin sheets of 5 mm thickness. The sheets contained 2% cumin-leucomalachitegreen-diethylamine (LMG-DEA) and plasticizer (up to 25% by weight). Irradiation experiments were performed to characterize the response to megavoltage radiation, including dose sensitivity, temporal decay rate, consistency of repeat irradiations, intra and inter-sheet reproducibility, multi-modality response (electrons and photons), and temperature sensitivity (22°C to 36°C). The local change in optical-density (ΔOD), before and after radiation, was obtained with a flat-bed film scanner and extracting the red channel. Repeat scanning enabled investigation of the temporal decay of ΔOD. Additional studies investigated clinical utility of the sheets through application to IMRT treatment plans (prostate and a TG119 commissioning plan), and a chest wall electron boost treatment. In the latter test, the sheet performed as a radiochromic bolus. RESULTS: The radiation induced OD change in the sheets was found to be proportional to dose and to exponentially decay to baseline in ~24 h (R2 = 0.9986). The sheet could be reused and had similar sensitivity (within 1% after the first irradiation) for at least eight irradiations. Importantly, no memory of previous irradiations was observed within measurement uncertainty. The consistency of dose response from photons (6 and 15 MV) and electrons (6-20 MeV) was found to be within calibration uncertainty (~1%). The dose sensitivity of the sheets had a temperature dependence of 0.0012 ΔOD/°C. For the short (1 min) single field IMRT QA verification, good agreement was observed between the Presage sheet and EBT film (gamma pass rate 97% at 3% 3 mm dose-difference and distance-to-agreement tolerance, with a 10% threshold). For the longer (~13 min) TG-119 9-field IMRT verification the gamma agreement was lower at 93% pass rate at 5% 3 mm, 10% threshold, when compared with Eclipse. The lower rate is attributed to uncertainty arising from signal decay during irradiation and indicates a current limitation. For the electron cutout treatment, both Presage and EBT agreed well (within 2% RMS difference) but differed from the Eclipse treatment plan (~7% RMS difference) indicating some limitations to the Eclipse modeling in this case. The worst case estimates of uncertainty introduced by the signal decay for deliveries of 2, 5, and 10 min are 0.6%, 1.4%, and 2.8% respectively. CONCLUSIONS: Reusable Presage sheets show promise for 2D dose measurement and as a radiochromic bolus for in vivo dose measurement. The current prototype is suitable for deliveries of length up to 5 min, where the uncertainty introduced by signal decay is anticipated to be ~1% (worst case 1.4%), or for longer deliveries where there is no temporal modulation (e.g. physical compensators, or open beams). Additionally, spatial resolution is limited by sheet thickness and scanner resolution, resulting in a practical resolution of 0.8 mm.
Authors
Collins, C; Yoon, SW; Kodra, J; Coakley, R; Subashi, E; Sidhu, K; Adamovics, J; Oldham, M
MLA Citation
Collins, Cielle, et al. “An investigation of a novel reusable radiochromic sheet for 2D dose measurement.Med Phys, vol. 46, no. 12, Dec. 2019, pp. 5758–69. Pubmed, doi:10.1002/mp.13798.
URI
https://scholars.duke.edu/individual/pub1409899
PMID
31479518
Source
pubmed
Published In
Med Phys
Volume
46
Published Date
Start Page
5758
End Page
5769
DOI
10.1002/mp.13798

Feasibility of radiosurgery dosimetry using NIPAM 3D dosimeters and x-ray CT

© Published under licence by IOP Publishing Ltd. We investigated the feasibility of using N-isopropylacrylamide (NIPAM) dosimeters with x-ray CT to verify radiosurgery dose. Dosimeters were prepared at one facility and shipped to a second facility for irradiation. A simulation CT was acquired and plans prepared for a 4 field box, and a 4 arc VMAT radiosurgery plan to 6 targets with 1cm diameter. Each dosimeter was aligned via CBCT and irradiated, followed by 5 diagnostic CTs acquired after >24 hours, which were averaged for analysis. Absolute dose calibration was applied and dose evaluated for both plans. Hounsfield Units were proportional to dose above 10-12Gy. For the 4-field box, mean difference between measured and predicted dose >10Gy was -0.13Gy -1.69Gy and gamma index was <1 for 72% and 65% of voxels using a 5% / 1mm and 3% / 2mm criteria, respectively (threshold = 15Gy, global dose criteria). For the multifocal SRS case, mean dose within each target was within -0.14Gy- 0.55Gy of the expected value, and gamma index was < 1 for 94.0% and 99.5% of voxels, respectively (threshold = 15Gy). NIPAM based 3D dosimetry with x-ray CT is well suited for validating radiosurgery spatial alignment, as well as dose distributions when dose is above 10-12Gy.
Authors
Adamson, J; Carroll, J; Trager, M; Yoon, P; Kodra, J; Yin, FF; Maynard, E; Hilts, M; Oldham, M; Jirasik, A
MLA Citation
Adamson, J., et al. “Feasibility of radiosurgery dosimetry using NIPAM 3D dosimeters and x-ray CT.” Journal of Physics: Conference Series, vol. 1305, no. 1, 2019. Scopus, doi:10.1088/1742-6596/1305/1/012004.
URI
https://scholars.duke.edu/individual/pub1417159
Source
scopus
Published In
Journal of Physics: Conference Series
Volume
1305
Published Date
DOI
10.1088/1742-6596/1305/1/012004