Adaptive Radiotherapy for Lung Cancer Using Uniform Scanning Proton Beams

Lung cancer remains the leading cause of cancer death in North America and is one of the major indications for proton therapy. Proton beams provide a superior dose distribution due to their finite ranges, but where they stop in the tissue is very sensitive to anatomical change. To ensure optimal target coverage and normal tissue sparing in the presence of geometrical variations, such as tumor shrinkage and other anatomical changes, adaptive planning is necessary in proton therapy of lung cancer. The objective of the chapter is to illustrate the rationale, process, and strategies in adaptive lung cancer treatment using uniform scanning proton beams. In addition, practical considerations for adaptive proton planning are discussed, such as software limitations, the associated costs and risks, and the criteria on whether and how to adapt a plan

Information Systems and Health Care IV: Real-Time ROC Analysis to Evaluate Radiologists\u27 Performanceof Interpreting Mammograpny

This paper describes how to use Receiver Operator Characteristic (ROC) analysis to evaluate radiologists\u27 performance of interpreting digital mammograms in real-time. We developed an experimental testing system, which implemented a set of clinical lesion-matching rules to prepare raw ROC data. The system can automatically provide detailed evaluations of the performance, such as sensitivity, specificity, positive predictive value, negative predictive value, diagnostic accuracy, ROC curve, and area under the curve (Az). Based on a preliminary evaluation of the system, we found that ROC analysis is appropriate for a real-time computer application, directly using the raw data from a database, to evaluate the performance of radiology residents

Inter-Observer Variability of a Commercial Patient Positioning and Verifi cation System in Proton Therapy

ABSTRACT Purpose: Accurate patient positioning is crucial in radiation therapy. To fully benefi t from the preciseness of proton therapy, image guided patient positioning and verifi cation system is typically utilized in proton therapy. The purpose of this study is to evaluate the inter-observer variability of image alignment using a commercially available patient positioning and verifi cation system in proton therapy. Methods: The VeriSuite patient positioning and verifi cation system (MedCom GmbH, Darmstadt, Germany) provides a six degrees of freedom correction vector by registering two orthogonal x-ray images to digitally reconstructed radiograph (DRR) images that are rendered in real time from the planning computed tomography (CT) images. Six cases of various disease sites, including brain, head & neck, lung, prostate, pelvis, and bladder, were used in this study. For each case, the planning CT images and a daily orthogonal x-ray portal image pair were loaded into the VeriSuite system. The same set of x-ray images and CT images for each case were reviewed and aligned separately by each of the 10 radiation therapist, following the clinical procedure for the corresponding disease site. The resulting correction vectors were then recorded and analyzed. Results: Our study shows that the inter-observer variation (One standard deviation) in image alignment using the VeriSuite system ranged from 1.2 to 2.0 mm for translational correction and from 0.6 to 1.3 degrees for rotational correction for the six cases. The use of fi ducial markers for prostate patient alignment achieved the least inter-observer variation while the bladder case produced the largest. Conclusions: Inter-observer variation in image alignment could be relatively large, depending on the complexity of patient anatomy, image alignment approach, and user experience and software limitations. Automatic registration and fi ducial markers could potentially be used to align patient more accurately and consistently. To ensure adequate tumor coverage in proton therapy, inter-observer variability in patient alignment should be carefully evaluated and accounted for in patient setup uncertainty analysis and treatment planning margin determination

Monte Carlo study of secondary electron production from gold nanoparticle in proton beam irradiation

Purpose: In this study, we examined some characteristics of secondary electrons produced by gold nanoparticle (NP) during proton beam irradiation.Method: By using the Geant4 Monte Carlo simulation toolkit, we simulated the NP at the range from radius (r) of 17.5 nm, 25 nm, 35 nm to r = 50 nm. The proton beam energies used were 20MeV, 50MeV, and 100MeV. Findings on secondary electron production and their average kinetic energy  are presented in this paper. Results: Firstly, for NP with a finite size, the secondary electron production increase with decreasing incident proton beam energy and secondary buildup existed outside NP. Secondly, the average kinetic energy of secondary electrons produced by a gold NP increased with incident proton beam energy. Thirdly, the larger the NP size, the more the secondary electron production.Conclusion: Collectively, our results suggest that apart from biological uptake efficiency, we should take the secondary electron production effect into   account when considering the potential use of NPs in proton beam irradiation.-----------------------------------------------Cite this article as: Gao J, Zheng Y. Monte Carlo study of secondary electron production from gold nanoparticle in proton beam irradiation. Int J  Cancer Ther Oncol 2014; 2(2):02025.DOI: http://dx.doi.org/10.14319/ijcto.0202.

Monte Carlo simulation of the neutron spectral fluence and dose equivalent for use in shielding a proton therapy vault

Neutron production is of principal concern when designing proton therapy vault shielding. Conventionally, neutron calculations are based on analytical methods, which do not accurately consider beam shaping components and nozzle shielding. The goal of this study was to calculate, using Monte Carlo modeling, the neutron spectral fluence and neutron dose equivalent generated by a realistic proton therapy nozzle and evaluate how these data could be used in shielding calculations. We modeled a contemporary passive scattering proton therapy nozzle in detail with the MCNPX simulation code. The neutron spectral fluence and dose equivalent at various locations in the treatment room were calculated and compared to those obtained from a thick iron target bombarded by parallel proton beams, the simplified geometry on which analytical methods are based. The neutron spectral fluence distributions were similar for both methods, with deeply penetrating high-energy neutrons (E \u3e 10 MeV) being most prevalent along the beam central axis, and low-energy neutrons predominating the neutron spectral fluence in the lateral region. However, unlike the inverse square falloff used in conventional analytical methods, this study shows that the neutron dose equivalent per therapeutic dose in the treatment room decreased with distance approximately following a power law, with an exponent of about -1.63 in the lateral region and -1.73 in the downstream region. Based on the simulated data according to the detailed nozzle modeling, we developed an empirical equation to estimate the neutron dose equivalent at any location and distance in the treatment vault, e.g. for cases in which detailed Monte Carlo modeling is not feasible. We applied the simulated neutron spectral fluence and dose equivalent to a shielding calculation as an example. © 2009 Institute of Physics and Engineering in Medicine

Ambient dose equivalent versus effective dose for quantifying stray radiation exposures to a patient receiving proton therapy for prostate cancer

The purpose of this study was to evaluate the suitability of the quantity ambient dose equivalent H*(10) as a conservative estimate of effective dose E for estimating stray radiation exposures to patients receiving passively scattered proton radiotherapy for cancer of the prostate. H*(10), which is determined from fluence free-in-air, is potentially useful because it is simpler to measure or calculate because it avoids the complexities associated with phantoms or patient anatomy. However, the suitability of H*(10) as a surrogate for E has not been demonstrated for exposures to high-energy neutrons emanating from radiation treatments with proton beams. The suitability was tested by calculating H*(10) and E for a proton treatment using a Monte Carlo model of a double-scattering treatment machine and a computerized anthropomorphic phantom. The calculated E for the simulated treatment was 5.5 mSv/Gy, while the calculated H*(10) at the isocenter was 10 mSv/Gy. A sensitivity analysis revealed that H*(10) conservatively estimated E for the interval of treatment parameters common in proton therapy for prostate cancer. However, sensitivity analysis of a broader interval of parameters suggested that H*(10) may underestimate E for treatments of other sites, particularly those that require large field sizes. Simulations revealed that while E was predominated by neutrons generated in the nozzle, neutrons produced in the patient contributed up to 40% to dose equivalent in near-field organs

Investigating dosimetric effect of rotational setup errors in IMPT planning of synchronous bilateral lung cancer

Purpose: The purpose of this study is to evaluate the dosimetric effect of rotational setup errors on the synchronous bi-lateral lung cancer plans generated by the intensity modulated proton therapy (IMPT) technique.Methods: The original IMPT plans were generated in for the left planning target volume (PTV) and right PTV of the left lung and right lung, respectively. Each plan was generated using two beams (lateral and posterior-anterior) with an isocenter placed at the center of the corresponding PTV. The IMPT plans were optimized for a total dose of 74 Gy[RBE] prescribed to each PTV with 2 Gy(RBE) per fraction. Original plans were recalculated by introducing simulated rotational errors. For each PTV, 18 rotational plans (±1⁰, ±2⁰, and ±3⁰) for each of the yaw, roll, and pitch rotations were generated. Results: Rotational errors caused the reduction in the clinical target volume (CTV) and PTV coverage in new rotational IMPT plans when compared to the original IMPT lung plans. The CTV D99 was reduced by up to 13.3%, 9.1%, and 5.9% for the yaw (+3⁰), roll (-3⁰), and pitch (+3⁰), respectively. The PTV D95 was reduced by up to 8.7%, 7.3%, and 4.6% for the yaw (+3⁰), roll (-3⁰), and pitch (+3⁰), respectively. The PTV V100 showed the highest deviation with a reduction of dose coverage by up to 40.1%, 31.8%, and 33.9% for the yaw (-3⁰), roll (-3⁰), and pitch (+3⁰) respectively. Conclusion: The rotational setup errors with magnitude of ≥2⁰ can produce a significant loss of dose coverage to the target volume in the IMPT of a synchronous bi-lateral lung cancer. The yaw had the most severe impact on the dosimetric results when compared to other two rotational errors (roll and pitch)

Reducing stray radiation dose to patients receiving passively scattered proton radiotherapy for prostate cancer

Proton beam radiotherapy exposes healthy tissue to stray radiation emanating from the treatment unit and secondary radiation produced within the patient. These exposures provide no known benefit and may increase a patient\u27s risk of developing a radiogenic second cancer. The aim of this study was to explore strategies to reduce stray radiation dose to a patient receiving a 76 Gy proton beam treatment for cancer of the prostate. The whole-body effective dose from stray radiation, E, was estimated using detailed Monte Carlo simulations of a passively scattered proton treatment unit and an anthropomorphic phantom. The predicted value of E was 567 mSv, of which 320 mSv was attributed to leakage from the treatment unit; the remainder arose from scattered radiation that originated within the patient. Modest modifications of the treatment unit reduced E by 212 mSv. Surprisingly, E from a modified passive-scattering device was only slightly higher (109 mSv) than from a nozzle with no leakage, e.g., that which may be approached with a spot-scanning technique. These results add to the body of evidence supporting the suitability of passively scattered proton beams for the treatment of prostate cancer, confirm that the effective dose from stray radiation was not excessive, and, importantly, show that it can be substantially reduced by modest enhancements to the treatment unit. © 2008 Institute of Physics and Engineering in Medicine

Stray radiation dose and second cancer risk for a pediatric patient receiving craniospinal irradiation with proton beams

Proton beam radiotherapy unavoidably exposes healthy tissue to stray radiation emanating from the treatment unit and secondary radiation produced within the patient. These exposures provide no known benefit and may increase a patient\u27s risk of developing a radiogenic cancer. The aims of this study were to calculate doses to major organs and tissues and to estimate second cancer risk from stray radiation following craniospinal irradiation (CSI) with proton therapy. This was accomplished using detailed Monte Carlo simulations of a passive-scattering proton treatment unit and a voxelized phantom to represent the patient. Equivalent doses, effective dose and corresponding risk for developing a fatal second cancer were calculated for a 10-year-old boy who received proton therapy. The proton treatment comprised CSI at 30.6 Gy plus a boost of 23.4 Gy to the clinical target volume. The predicted effective dose from stray radiation was 418 mSv, of which 344 mSv was from neutrons originating outside the patient; the remaining 74 mSv was caused by neutrons originating within the patient. This effective dose corresponds to an attributable lifetime risk of a fatal second cancer of 3.4%. The equivalent doses that predominated the effective dose from stray radiation were in the lungs, stomach and colon. These results establish a baseline estimate of the stray radiation dose and corresponding risk for a pediatric patient undergoing proton CSI and support the suitability of passively-scattered proton beams for the treatment of central nervous system tumors in pediatric patients. © 2009 Institute of Physics and Engineering in Medicine

The risk of developing a second cancer after receiving craniospinal proton irradiation

The purpose of this work was to compare the risk of developing a second cancer after craniospinal irradiation using photon versus proton radiotherapy by means of simulation studies designed to account for the effects of neutron exposures. Craniospinal irradiation of a male phantom was calculated for passively-scattered and scanned-beam proton treatment units. Organ doses were estimated from treatment plans; for the proton treatments, the amount of stray radiation was calculated separately using the Monte Carlo method. The organ doses were converted to risk of cancer incidence using a standard formalism developed for radiation protection purposes. The total lifetime risk of second cancer due exclusively to stray radiation was 1.5% for the passively scattered treatment versus 0.8% for the scanned proton beam treatment. Taking into account the therapeutic and stray radiation fields, the risk of second cancer from intensity-modulated radiation therapy and conventional radiotherapy photon treatments were 7 and 12 times higher than the risk associated with scanned-beam proton therapy, respectively, and 6 and 11 times higher than with passively scattered proton therapy, respectively. Simulations revealed that both passively scattered and scanned-beam proton therapies confer significantly lower risks of second cancers than 6 MV conventional and intensity-modulated photon therapies. © 2009 Institute of Physics and Engineering in Medicine