Midwest Proton Radiotherapy Institute

Bloomington, IN, United States

Midwest Proton Radiotherapy Institute

Bloomington, IN, United States
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Perez-Andujar A.,University of Wisconsin - Madison | Perez-Andujar A.,University of California at San Francisco | Deluca P.M.,University of Wisconsin - Madison | Thornton A.F.,Midwest Proton Radiotherapy Institute | And 5 more authors.
Radiation Protection Dosimetry | Year: 2012

This work presents microdosimetric measurements performed at the Midwest Proton Radiotherapy Institute in Bloomington, Indiana, USA. The measurements were done simulating clinical setups with a water phantom and for a variety of stopping targets. The water phantom was irradiated by a proton spread out Bragg peak (SOBP) and by a proton pencil beam. Stopping target measurements were performed only for the pencil beam. The targets used were made of polyethylene, brass and lead. The objective of this work was to determine the neutron-absorbed dose for a passive and active proton therapy delivery, and for the interactions of the proton beam with materials typically in the beam line of a proton therapy treatment nozzle. Neutron doses were found to be higher at 45° and 90° from the beam direction for the SOBP configuration by a factor of 1.1 and 1.3, respectively, compared with the pencil beam. Meanwhile, the pencil beam configuration produced neutron-absorbed doses 2.2 times higher at 0° than the SOBP. For stopping targets, lead was found to dominate the neutron-absorbed dose for most angles due to a large production of low-energy neutrons emitted isotropically. © The Author 2012. Published by Oxford University Press. All rights reserved.


Zhao Q.,Midwest Proton Radiotherapy Institute | Zhao Q.,Purdue University | Wu H.,Indiana University – Purdue University Indianapolis | Wolanski M.,Midwest Proton Radiotherapy Institute | And 5 more authors.
Physics in Medicine and Biology | Year: 2010

An accurate, simple and time-saving sector integration method for calculating the proton output (dose/monitor unit, MU) is presented based on the following treatment field parameters: aperture shape, aperture size, measuring position, beam range and beam modulation. The model is validated with dose/MU values for 431 fields previously measured at our center. The measurements were obtained in a uniform scanning proton beam with a parallel plate ionization chamber in a water phantom. For beam penetration depths of clinical interest (6-27 cm water), dose/MU values were measured as a function of spread-out Bragg peak (SOBP) extent and aperture diameter. First, 90 randomly selected fields were used to derive the model parameters, which were used to compute the dose/MU values for the remaining 341 fields. The min, max, average and the standard deviation of the difference between the calculated and the measured dose/MU values of the 341 fields were used to evaluate the accuracy and stability, for different energy ranges, aperture sizes, measurement positions and SOBP values. The experimental results of the five different functional sets showed that the calculation model is accurate with calculation errors ranging from -2.4% to 3.3%, and 99% of the errors are less than 2%. The accuracy increases with higher energy, larger SOBP and bigger aperture size. The average error in the dose/MU calculation for small fields (field size <25 cm2) is 0.31 0.96 (%). © 2010 Institute of Physics and Engineering in Medicine.


Zhang R.,University of Houston | Taddei P.J.,University of Houston | Fitzek M.M.,Midwest Proton Radiotherapy Institute | Fitzek M.M.,Indiana University | Newhauser W.D.,University of Houston
Physics in Medicine and Biology | Year: 2010

Heavy charged particle beam radiotherapy for cancer is of increasing interest because it delivers a highly conformal radiation dose to the target volume. Accurate knowledge of the range of a heavy charged particle beam after it penetrates a patient's body or other materials in the beam line is very important and is usually stated in terms of the water equivalent thickness (WET). However, methods of calculating WET for heavy charged particle beams are lacking. Our objective was to test several simple analytical formulas previously developed for proton beams for their ability to calculate WET values for materials exposed to beams of protons, helium, carbon and iron ions. Experimentally measured heavy charged particle beam ranges and WET values from an iterative numerical method were compared with the WET values calculated by the analytical formulas. In most cases, the deviations were within 1 mm. We conclude that the analytical formulas originally developed for proton beams can also be used to calculate WET values for helium, carbon and iron ion beams with good accuracy. © 2010 Institute of Physics and Engineering in Medicine.


Zhao L.,Midwest Proton Radiotherapy Institute | Zhao L.,Indiana University | Das I.J.,Midwest Proton Radiotherapy Institute | Das I.J.,Indiana University | And 4 more authors.
Journal of Physics: Conference Series | Year: 2010

PRESAGE™ dosimeter dosimeter has been proved useful for 3D dosimetry in conventional photon therapy and IMRT [1-5]. Our objective is to examine the use of PRESAGE™ dosimeter for verification of depth dose distribution in proton beam therapy. Three PRESAGE™ samples were irradiated with a 79 MeV un-modulated proton beam. Percent depth dose profile measured from the PRESAGE™ dosimeter is compared with data obtained in a water phantom using a parallel plate Advanced Markus chamber. The Bragg-peak position determined from the PRESAGE™ is within 2 mm compared to measurements in water. PRESAGE™ shows a highly linear response to proton dose. However, PRESAGE™ also reveals an underdosage around the Bragg peak position due to LET effects. Depth scaling factor and quenching correction factor need further investigation. Our initial result shows that PRESAGE™ has promising dosimetric characteristics that could be suitable for proton beam dosimetry. © 2010 IOP Publishing Ltd.


Farr J.B.,Midwest Proton Radiotherapy Institute
Journal of applied clinical medical physics / American College of Medical Physics | Year: 2010

Large area, shallow fields are well suited to proton therapy. However, due to beam production limitations, such volumes typically require multiple matched fields. This is problematic due to the relatively narrow beam penumbra at shallow depths compared to electron and photon beams. Therefore, highly accurate dose planning and delivery is required. As the dose delivery includes shifting the patient for matched fields, accuracy at the 1-2 millimeter level in patient positioning is also required. This study investigates the dosimetric accuracy of such proton field matching by an innovative robotic patient positioner system (RPPS). The dosimetric comparisons were made between treatment planning system calculations, radiographic film and ionization chamber measurements. The results indicated good agreement amongst the methods and suggest that proton field matching by a RPPS is accurate and efficient.


Zhao L.,Midwest Proton Radiotherapy Institute | Zhao L.,Indiana University | Das I.J.,Midwest Proton Radiotherapy Institute | Das I.J.,Indiana University
Physics in Medicine and Biology | Year: 2010

The depth dose verification of active scanning proton beams is extremely time consuming with ion chamber measurements for beam data commissioning and patient specific measurements. With widespread use of Gafchromic EBT films, two-dimensional high-resolution dosimetry is explored in a uniform scanning proton beam. The EBT films were exposed parallel to the beam axis in a solid water phantom in order to obtain the depth-dose curve in a single measurement and compared with the gold standard measurement with a parallel plate ion chamber in water. Our results demonstrate that EBT films perform well in determining the proton beam range, with uncertainty of 0.5 mm. It is also found that EBT film response is a function of energy over the effective energy of 50-160 MeV proton beams with the variations less than 10%. However, an under-dosage of up to 20% was observed at the peak of the Bragg curve. An empirically derived correction factor is proposed to account for the EBT energy dependence. With corrections, EBT films can be a useful tool for the depth dose verification of active scanning proton beams, thus saving valuable proton beam time. © 2010 Institute of Physics and Engineering in Medicine.


Andolino D.L.,Indiana University | Hoene T.,Midwest Proton Radiotherapy Institute | Xiao L.,Indiana University | Buchsbaum J.,Indiana University | And 3 more authors.
International Journal of Radiation Oncology Biology Physics | Year: 2011

Purpose: To assess the potential reduction in breast dose for young girls with Hodgkin's lymphoma (HL) treated with breast-sparing proton therapy (BS-PT) as compared with three-dimensional conformal involved-field photon radiotherapy (3D-CRT). Methods and Materials: The Clarian Health Cancer Registry was queried for female pediatric patients with the diagnosis of HL who received radiotherapy at the Indiana University Simon Cancer Center during 2006-2009. The original CT simulation images were obtained, and 3D-CRT and BS-PT plans delivering 21 Gy or cobalt gray equivalent (CGE) in 14 fractions were created for each patient. Dose-volume histogram data were collected for both 3D-CRT and BS-PT plans and compared by paired t test for correlated samples. Results: The cancer registry provided 10 female patients with Ann Arbor Stage II HL, aged 10-18 years at the time of treatment. Both mean and maximum breast dose were significantly less with BS-PT compared with 3D-CRT: 0.95 CGE vs. 4.70 Gy (p < 0.001) and 21.07 CGE vs. 23.11 Gy (p < 0.001), respectively. The volume of breast receiving 1.0 Gy/CGE and 5.0 Gy/CGE was also significantly less with BS-PT, 194 cm 3 and 93 cm 3, respectively, compared with 790 cm 3 and 360 cm 3 with 3D-CRT (p = 0.009, 0.013). Conclusion: Breast-sparing proton therapy has the potential to reduce unnecessary breast dose in young girls with HL by as much as 80% relative to involved-field 3D-CRT. © 2011 Elsevier Inc.


Cheng C.-W.,Midwest Proton Radiotherapy Institute | Cheng C.-W.,Indiana University | Wolanski M.,Midwest Proton Radiotherapy Institute | Wolanski M.,Indiana University | And 6 more authors.
Medical Physics | Year: 2010

Purpose: Entrance dose (or skin dose) is an important part of patient quality assurance in external beam radiation therapy. However, entrance dose verification in proton beam is not routinely performed. In this study, the OneDose single use MOSFET detector system for in vivo dosimetry measurement in proton therapy is investigated. Methods: Using a solid water phantom, several fundamental dosimetric characteristics of the OneDose system are studied with a proton beam: The reproducibility (consistency) of the dosimeter, the linearity with dose and dose rate, energy dependence, directional dependence, LET dependence, and fading (delay readout with time) is studied. Results: OneDose detectors show dose and dose rate linearity but exhibit pronounced energy dependence at depth and a large variation in dose response with LET. On the other hand, the detector response remain relatively constant (within 3%) at surface over a wide range of energies. There is also a slight angular dependence (about 2%) up to 60° angle of incidence. However, detector orientation such that incidence along the long axis of the detector should be avoided as the proton beam will have to traverse a large amount of the copper backing. Since most in vivo dosimetry involves entrance dose measurement, the OneDose at surface appears to be well suited for such application. OneDose exhibits small intrabatch variation (≤2% at one SD) indicating that it is only necessary to calibration a few detectors from each batch. The interbatch variation is generally within 3%. Conclusions: The small detector size and its relatively flexible design of OneDose allow dose measurement to be performed on a curved surface or in small cavities that is otherwise difficult with the conventional diode detectors. The slight drawback in its angular dependence can be easily handled by angular dependence table. However, since OneDose is a single use detector, the intrabatch consistency must be verified before the remaining detectors from the same batch could be used for in vivo dosimetry. It is advisable that the detectors from the same batch be taken for the same application to reduce the dosimetric uncertainty. For detectors from different batches, interbatch consistency should also be verified to obtain reliable results. OneDose provides an opportunity to measure in vivo dose with proton beam within acceptable clinical criterion of ±(5.0%-6.5%). © 2010 American Association of Physicists in Medicine.


Nichiporov D.F.,Indiana University | Klyachko A.V.,Indiana University | Solberg K.A.,Indiana University | Zhao Q.,Midwest Proton Radiotherapy Institute
Radiation Measurements | Year: 2011

A monitor for a uniformly scanned beam was designed and constructed by the Indiana University Cyclotron Facility for use in a clinical proton gantry at the Midwest Proton Radiotherapy Institute. The beam monitor is a thin-walled, wide-aperture ionization chamber, which provides information about dose, beam size, symmetry, flatness, and position. Several characteristics of the monitor's performance were studied, including linearity in dose rate, reproducibility, recombination correction, and dependence on both radiation field size and gantry angle. Additionally, stability of the detector output was analyzed using daily monitor calibrations performed over a period of 21 months. The beam monitor was found to meet design requirements for linearity (±1%), calibration stability (±2%), and stability of response as a function of gantry angle (±1%). Beam monitor calibration statistics also revealed a sine-like yearly trend with a ±2% maximum deviation from the average. These and other beam monitor test results are presented and discussed in the context of the detector design. Design changes aimed at further improving the detector's performance characteristics are proposed. © 2010 Elsevier Ltd. All rights reserved.


PubMed | Midwest Proton Radiotherapy Institute
Type: Journal Article | Journal: Medical physics | Year: 2010

Entrance dose (or skin dose) is an important part of patient quality assurance in external beam radiation therapy. However, entrance dose verification in proton beam is not routinely performed. In this study, the OneDose single use MOSFET detector system for in vivo dosimetry measurement in proton therapy is investigated.Using a solid water phantom, several fundamental dosimetric characteristics of the OneDose system are studied with a proton beam: The reproducibility (consistency) of the dosimeter, the linearity with dose and dose rate, energy dependence, directional dependence, LET dependence, and fading (delay readout with time) is studied.OneDose detectors show dose and dose rate linearity but exhibit pronounced energy dependence at depth and a large variation in dose response with LET. On the other hand, the detector response remain relatively constant (within 3%) at surface over a wide range of energies. There is also a slight angular dependence (about 2%) up to 60 degrees angle of incidence. However, detector orientation such that incidence along the long axis of the detector should be avoided as the proton beam will have to traverse a large amount of the copper backing. Since most in vivo dosimetry involves entrance dose measurement, the OneDose at surface appears to be well suited for such application. OneDose exhibits small intrabatch variation (< or = 2% at one SD) indicating that it is only necessary to calibration a few detectors from each batch. The interbatch variation is generally within 3%.The small detector size and its relatively flexible design of OneDose allow dose measurement to be performed on a curved surface or in small cavities that is otherwise difficult with the conventional diode detectors. The slight drawback in its angular dependence can be easily handled by angular dependence table. However, since OneDose is a single use detector, the intra-batch consistency must be verified before the remaining detectors from the same batch could be used for in vivo dosimetry. It is advisable that the detectors from the same batch be taken for the same application to reduce the dosimetric uncertainty. For detectors from different batches, inter-batch consistency should also be verified to obtain reliable results. OneDose provides an opportunity to measure in vivo dose with proton beam within acceptable clinical criterion of +/- (5.0%-6.5%).

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