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1.
Adv Radiat Oncol ; 9(3): 101425, 2024 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-38379895

RESUMO

Purpose: Animal studies with ultrahigh dose-rate radiation therapy (FLASH, >40 Gy/s) preferentially spare normal tissues without sacrificing antitumor efficacy compared with conventional dose-rate radiation therapy (CONV). At the University of Washington, we developed a cyclotron-generated preclinical scattered proton beam with FLASH dose rates. We present the technical details of our FLASH radiation system and preliminary biologic results from whole pelvis radiation. Methods and Materials: A Scanditronix MC50 compact cyclotron beamline has been modified to produce a 48.7 MeV proton beam at dose rates between 0.1 and 150 Gy/s. The system produces a 6 cm diameter scattered proton beam (flat to ± 3%) at the target location. Female C57BL/6 mice 5 to 6 weeks old were used for all experiments. To study normal tissue effects in the distal colon, mice were irradiated using the entrance region of the proton beam to the whole pelvis, 18.5 Gy at different dose rates: control, CONV (0.6-1 Gy/s) and FLASH (50-80 Gy/s). Survival was monitored daily and EdU (5-ethynyl-2´-deoxyuridine) staining was performed at 24- and 96-hours postradiation. Cleaved caspase-3 staining was performed 24-hours postradiation. To study tumor control, allograft B16F10 tumors were implanted in the right flank and received 18 Gy CONV or FLASH proton radiation. Tumor growth and survival were monitored. Results: After 18.5 Gy whole pelvis radiation, survival was 100% in the control group, 0% in the CONV group, and 44% in the FLASH group (P < .01). EdU staining showed cell proliferation was significantly higher in the FLASH versus CONV group at both 24-hours and 96-hours postradiation in the distal colon, although both radiation groups showed decreased proliferation compared with controls (P < .05). Lower cleaved caspase-3 staining was seen in the FLASH versus conventional group postradiation (P < .05). Comparable flank tumor control was observed in the CONV and FLASH groups. Conclusions: We present our preclinical FLASH proton radiation system and biologic results showing improved survival after whole pelvis radiation, with equivalent tumor control.

2.
Phys Med ; 107: 102551, 2023 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-36867911

RESUMO

PURPOSE: An ocular applicator that fits a commercial proton snout with an upstream range shifter to allow for treatments with sharp lateral penumbra is described. MATERIALS AND METHODS: The validation of the ocular applicator consisted of a comparison of range, depth doses (Bragg peaks and spread out Bragg peaks), point doses, and 2-D lateral profiles. Measurements were made for three field sizes, 1.5, 2, and 3 cm, resulting in 15 beams. Distal and lateral penumbras were simulated in the treatment planning system for seven range-modulation combinations for beams typical of ocular treatments and a field size of 1.5 cm, and penumbra values were compared to published literature. RESULTS: All the range errors were within 0.5 mm. The maximum averaged local dose differences for Bragg peaks and SOBPs were 2.6% and 1.1%, respectively. All the 30 measured point doses were within +/-3% of the calculated. The measured lateral profiles, analyzed through gamma index analysis and compared to the simulated, had pass rates greater than 96% for all the planes. The lateral penumbra increased linearly with depth, from 1.4 mm at 1 cm depth to 2.5 mm at 4 cm depth. The distal penumbra ranged from 3.6 to 4.4 mm and increased linearly with the range. The treatment time for a single 10 Gy (RBE) fractional dose ranged from 30 to 120 s, depending on the shape and size of the target. CONCLUSIONS: The ocular applicator's modified design allows lateral penumbra similar to dedicated ocular beamlines while enabling planners to use modern treatment tools such as Monte Carlo and full CT-based planning with increased flexibility in beam placement.


Assuntos
Terapia com Prótons , Prótons , Terapia com Prótons/métodos , Imagens de Fantasmas , Dosagem Radioterapêutica , Síncrotrons , Método de Monte Carlo , Planejamento da Radioterapia Assistida por Computador/métodos
3.
Med Phys ; 49(9): 6209-6220, 2022 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-35760763

RESUMO

BACKGROUND: With the emergence of more complex and novel proton delivery techniques, there is a need for quality assurance tools with high spatiotemporal resolution to conveniently measure the spatial and temporal properties of the beam. In this context, scintillation-based dosimeters, if synchronized with the radiation beam and corrected for ionization quenching, are appealing. PURPOSE: To develop a synchronized high-speed scintillation imaging system for characterization and verification of the proton therapy beams on a pulse-by-pulse basis. MATERIALS AND METHODS: A 30 cm × 30 cm × 5 cm block of BC-408 plastic scintillator placed in a light-tight housing was irradiated by proton beams generated by a Mevion S250 proton therapy synchrocyclotron. A high-speed camera system, placed perpendicular to the beam direction and facing the scintillator, was synchronized to the accelerator's pulses to capture images. Opening and closing of the camera's shutter was controlled by setting a proper time delay and exposure time, respectively. The scintillation signal was recorded as a set of two-dimensional (2D) images. Empirical correction factors were applied to the images to correct for the nonuniformity of the pixel sensitivity and quenching of the scintillator. Proton range and modulation were obtained from the corrected images. RESULTS: The camera system was able to capture all data on a pulse-by-pulse basis at a rate of ∼504 frames per second. The applied empirical correction method for ionization quenching was effective and the corrected composite image provided a 2D map of dose distribution. The measured range (depth of distal 90%) through scintillation imaging agreed within 1.2 mm with that obtained from ionization chamber measurement. CONCLUSION: A high-speed camera system capable of capturing scintillation signals from individual proton pulses was developed. The scintillation imaging system is promising for rapid proton beam characterization and verification.


Assuntos
Terapia com Prótons , Contagem de Cintilação , Ciclotrons , Método de Monte Carlo , Prótons , Radiometria , Dosagem Radioterapêutica , Contagem de Cintilação/métodos
4.
Sci Rep ; 12(1): 4648, 2022 03 17.
Artigo em Inglês | MEDLINE | ID: mdl-35301371

RESUMO

Treatment of ocular tumors on dedicated scattering-based proton therapy systems is standard afforded due to sharp lateral and distal penumbras. However, most newer proton therapy centers provide pencil beam scanning treatments. In this paper, we present a pencil beam scanning (PBS)-based ocular treatment solution. The design, commissioning, and validation of an applicator mount for a conventional PBS snout to allow for ocular treatments are given. In contrast to scattering techniques, PBS-based ocular therapy allows for inverse planning, providing planners with additional flexibility to shape the radiation field, potentially sparing healthy tissues. PBS enables the use of commercial Monte Carlo algorithms resulting in accurate dose calculations in the presence of heterogeneities and fiducials. The validation consisted of small field dosimetry measurements of point doses, depth doses, and lateral profiles relevant to ocular therapy. A comparison of beam properties achieved through the applicator against published literature is presented. We successfully showed the feasibility of PBS-based ocular treatments.


Assuntos
Neoplasias Oculares , Terapia com Prótons , Algoritmos , Neoplasias Oculares/radioterapia , Humanos , Método de Monte Carlo , Imagens de Fantasmas , Terapia com Prótons/métodos , Prótons , Dosagem Radioterapêutica , Planejamento da Radioterapia Assistida por Computador/métodos
5.
Med Phys ; 48(6): e86-e114, 2021 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-33780010

RESUMO

With the advancement of data-intensive technologies, such as image-guided radiation therapy (IGRT) and intensity-modulated radiation therapy (IMRT), the amount and complexity of data to be transferred between clinical subsystems have increased beyond the reach of manual checking. As a result, unintended treatment deviations (e.g., dose errors) may occur if the treatment system is not closely monitored by a comprehensive data transfer quality management program (QM). This report summarizes the findings and recommendations from the task group (TG) on quality assurance (QA) of external beam treatment data transfer (TG-201), with the aim to assist medical physicists in designing their own data transfer QM. As a background, a section of this report describes various models of data flow (distributed data repositories and single data base systems) and general data test characteristics (data integrity, interpretation, and consistency). Recommended tests are suggested based on the collective experience of TG-201 members. These tests are for the acceptance of, commissioning of, and upgrades to subsystems that store and/or modify clinical treatment data. As treatment complexity continues to evolve, we will need to do and know more about ensuring the quality of data transfers. The report concludes with the recommendation to move toward data transfer open standards compatibility and to develop tools that automate data transfer QA.


Assuntos
Radioterapia Guiada por Imagem , Radioterapia de Intensidade Modulada , Dosagem Radioterapêutica , Planejamento da Radioterapia Assistida por Computador , Relatório de Pesquisa , Estados Unidos
6.
Phys Med ; 80: 175-185, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-33189048

RESUMO

PURPOSE: This work aims to validate new 6D couch features and their implementation for seated radiotherapy in RayStation (RS) treatment planning system (TPS). MATERIALS AND METHODS: In RS TPS, new 6D couch features are (i) chair support device, (ii) patient treatment option of "Sitting: face towards the front of the chair", and (iii) patient support pitch and roll capabilities. The validation of pitch and roll was performed by comparing TPS generated DRRs with planar x-rays. Dosimetric tests through measurement by 2D ion chamber array were performed for beams created with varied scanning and treatment orientation and 6D couch rotations. For the implementation of 6D couch features for treatments in a seated position, the TPS and oncology information system (Mosaiq) settings are described for a commercial chair. An end-to-end test using an anthropomorphic phantom was performed to test the complete workflow from simulation to treatment delivery. RESULTS: The 6D couch features were found to have a consistent implementation that met IEC 61712 standard. The DRRs were found to have an acceptable agreement with planar x-rays based on visual inspection. For dose map comparison between measured and calculated, the gamma index analysis for all the beams was >95% at a 3% dose-difference and 3 mm distance-to-agreement tolerances. For an end-to end-testing, the phantom was successfully set up at isocenter in the seated position and treatment was delivered. CONCLUSIONS: Chair-based treatments in a seated position can be implemented in RayStation through the use of newly released 6D couch features.


Assuntos
Terapia com Prótons , Planejamento da Radioterapia Assistida por Computador , Radioterapia de Intensidade Modulada , Humanos , Imagens de Fantasmas , Dosagem Radioterapêutica , Postura Sentada
7.
Phys Med ; 78: 179-186, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-33038643

RESUMO

PURPOSE: This study aims to investigate the use of machine learning models for delivery error prediction in proton pencil beam scanning (PBS) delivery. METHODS: A dataset of planned and delivered PBS spot parameters was generated from a set of 20 prostate patient treatments. Planned spot parameters (spot position, MU and energy) were extracted from the treatment planning system (TPS) for each beam. Delivered spot parameters were extracted from irradiation log-files for each beam delivery following treatment. The dataset was used as a training dataset for three machine learning models which were trained to predict delivered spot parameters based on planned parameters. K-fold cross validation was employed for hyper-parameter tuning and model selection where the mean absolute error (MAE) was used as the model evaluation metric. The model with lowest MAE was then selected to generate a predicted dose distribution for a test prostate patient within a commercial TPS. RESULTS: Analysis of the spot position delivery error between planned and delivered values resulted in standard deviations of 0.39 mm and 0.44 mm for x and y spot positions respectively. Prediction error standard deviation values of spot positions using the selected model were 0.22 mm and 0.11 mm for x and y spot positions respectively. Finally, a three-way comparison of dose distributions and DVH values for select OARs indicates that the random-forest-predicted dose distribution within the test prostate patient was in closer agreement to the delivered dose distribution than the planned distribution. CONCLUSIONS: PBS delivery error can be accurately predicted using machine learning techniques.


Assuntos
Terapia com Prótons , Prótons , Humanos , Aprendizado de Máquina , Dosagem Radioterapêutica , Planejamento da Radioterapia Assistida por Computador
9.
Int J Radiat Oncol Biol Phys ; 104(2): 374-382, 2019 06 01.
Artigo em Inglês | MEDLINE | ID: mdl-30763658

RESUMO

PURPOSE: This study examines the relationship between dose to corneal substructures and incidence of corneal toxicity within 6 months of proton beam therapy (PBT) for uveal melanoma. We aim to develop clinically meaningful dose constraints that can be used to mitigate corneal toxicity. METHODS AND MATERIALS: Ninety-two patients were treated with PBT between 2015 and 2017 and evaluated for grade 2+ (GR2+) intervention-requiring corneal toxicity in our prospectively maintained database. Most patients were treated with 50 Gy (relative biological effectiveness [RBE]) in 5 fractions, and all had complete six-month follow-up. Analyses included Mann-Whitney, χ2, Fisher exact, and receiver operating curve tests to identify risk factors for GR2+ toxicity. Bivariate logistic regression was used to identify independent dose-volume histogram (DVH) predictors of toxicity after adjustment for the most important clinical risk factor. RESULTS: The 6-month PBT GR2+ corneal toxicity rate was 10.9%, with half of patients experiencing grade 2 toxicity and half experiencing grade 3 toxicity, with no grade 4 events. Patients with anterior chamber tumors had a higher risk (58.3%) for toxicity than those with posterior tumors (0%) or posterior tumors extending past the equator (25%, P < .0001). On univariate analysis, larger size according to Collaborative Ocular Melanoma Studies was associated with increased toxicity rate (P < .004). DVH analysis revealed that cutoffs of 58% for V25, 32% for V45, 51.8 Gy (RBE) for maximum dose, and 32 Gy (RBE) for mean dose to the cornea separated patients into groups experiencing and not experiencing toxicity with 90% sensitivity and ≥96% specificity. Bivariate logistic regression indicated that corneal V25, V45, and mean dose independently predicted for toxicity after adjusting for tumor location. CONCLUSIONS: Patients receiving PBT for anterior uveal melanomas experience a high rate of GR2+ corneal toxicity because of increased corneal dose. Anterior location and corneal DVH parameters independently predict toxicity risk. We propose dosimetric constraints to facilitate treatment planning and toxicity mitigation.


Assuntos
Córnea/efeitos da radiação , Melanoma/radioterapia , Terapia com Prótons/efeitos adversos , Lesões por Radiação/etiologia , Neoplasias Uveais/radioterapia , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Fracionamento da Dose de Radiação , Feminino , Humanos , Incidência , Limbo da Córnea/efeitos da radiação , Masculino , Melanoma/patologia , Pessoa de Meia-Idade , Doses de Radiação , Lesões por Radiação/epidemiologia , Lesões por Radiação/patologia , Radioterapia Guiada por Imagem , Eficiência Biológica Relativa , Fatores de Risco , Fatores de Tempo , Neoplasias Uveais/patologia , Adulto Jovem
10.
Transl Lung Cancer Res ; 7(2): 171-179, 2018 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-29876316

RESUMO

The accuracy of dose calculation is vital to the quality of care for patients undergoing proton beam therapy (PBT). Currently, the dose calculation algorithms available in commercial treatment planning systems (TPS) in PBT are classified into two classes: pencil beam (PB) and Monte-Carlo (MC) algorithms. PB algorithms are still regarded as the standard of practice in PBT, but they are analytical approximations whereas MC algorithms use random sampling of interaction cross-sections that represent the underlying physics to simulate individual particles trajectories. This article provides a brief review of PB and MC dose calculation algorithms employed in commercial treatment planning systems and their performance comparison in phantoms through simulations and measurements. Deficiencies of PB algorithms are first highlighted by a simplified simulation demonstrating the transport of a single sub-spot of proton beam that is incident at an oblique angle in a water phantom. Next, more typical cases of clinical beams in water phantom are presented and compared to measurements. The inability of PB to correctly predict the range and subsequently distal fall-off is emphasized. Through the presented examples, it is shown how dose errors as high as 30% can result with use of a PB algorithm. These dose errors can be minimized to clinically acceptable levels of less than 5%, if MC algorithm is employed in TPS. As a final illustration, comparison between PB and MC algorithm is made for a clinical beam that is use to deliver uniform dose to a target in a lung section of an anthropomorphic phantom. It is shown that MC algorithm is able to correctly predict the dose at all depths and matched with measurements. For PB algorithm, there is an increasing mismatch with the measured doses with increasing tissue heterogeneity. The findings of this article provide a foundation for the second article of this series to compare MC vs. PB based lung cancer treatment planning.

11.
Phys Med Biol ; 63(2): 02NT03, 2018 01 18.
Artigo em Inglês | MEDLINE | ID: mdl-29346116

RESUMO

Four dimensional computed tomography (4DCT) scans are routinely used in radiation therapy to determine the internal treatment volume for targets that are moving (e.g. lung tumors). The use of these studies has allowed clinicians to create target volumes based upon the motion of the tumor during the imaging study. The purpose of this work is to determine if a target volume based on a single 4DCT scan at simulation is sufficient to capture thoracic motion. Phantom studies were performed to determine expected differences between volumes contoured on 4DCT scans and those on the evaluation CT scans (slow scans). Evaluation CT scans acquired during treatment of 11 patients were compared to the 4DCT scans used for treatment planning. The images were assessed to determine if the target remained within the target volume determined during the first 4DCT scan. A total of 55 slow scans were compared to the 11 planning 4DCT scans. Small differences were observed in phantom between the 4DCT volumes and the slow scan volumes, with a maximum of 2.9%, that can be attributed to minor differences in contouring and the ability of the 4DCT scan to adequately capture motion at the apex and base of the motion trajectory. Larger differences were observed in the patients studied, up to a maximum volume difference of 33.4%. These results demonstrate that a single 4DCT scan is not adequate to capture all thoracic motion throughout treatment.


Assuntos
Tomografia Computadorizada Quadridimensional/métodos , Processamento de Imagem Assistida por Computador/métodos , Movimento , Imagens de Fantasmas , Planejamento da Radioterapia Assistida por Computador/métodos , Neoplasias Torácicas/diagnóstico por imagem , Neoplasias Torácicas/radioterapia , Humanos , Terapia com Prótons , Dosagem Radioterapêutica , Radioterapia Conformacional , Respiração , Estudos Retrospectivos
12.
Phys Med Biol ; 62(19): 7659-7681, 2017 Sep 12.
Artigo em Inglês | MEDLINE | ID: mdl-28749373

RESUMO

RaySearch Americas Inc. (NY) has introduced a commercial Monte Carlo dose algorithm (RS-MC) for routine clinical use in proton spot scanning. In this report, we provide a validation of this algorithm against phantom measurements and simulations in the GATE software package. We also compared the performance of the RayStation analytical algorithm (RS-PBA) against the RS-MC algorithm. A beam model (G-MC) for a spot scanning gantry at our proton center was implemented in the GATE software package. The model was validated against measurements in a water phantom and was used for benchmarking the RS-MC. Validation of the RS-MC was performed in a water phantom by measuring depth doses and profiles for three spread-out Bragg peak (SOBP) beams with normal incidence, an SOBP with oblique incidence, and an SOBP with a range shifter and large air gap. The RS-MC was also validated against measurements and simulations in heterogeneous phantoms created by placing lung or bone slabs in a water phantom. Lateral dose profiles near the distal end of the beam were measured with a microDiamond detector and compared to the G-MC simulations, RS-MC and RS-PBA. Finally, the RS-MC and RS-PBA were validated against measured dose distributions in an Alderson-Rando (AR) phantom. Measurements were made using Gafchromic film in the AR phantom and compared to doses using the RS-PBA and RS-MC algorithms. For SOBP depth doses in a water phantom, all three algorithms matched the measurements to within ±3% at all points and a range within 1 mm. The RS-PBA algorithm showed up to a 10% difference in dose at the entrance for the beam with a range shifter and >30 cm air gap, while the RS-MC and G-MC were always within 3% of the measurement. For an oblique beam incident at 45°, the RS-PBA algorithm showed up to 6% local dose differences and broadening of distal fall-off by 5 mm. Both the RS-MC and G-MC accurately predicted the depth dose to within ±3% and distal fall-off to within 2 mm. In an anthropomorphic phantom, the gamma index (dose tolerance = 3%, distance-to-agreement = 3 mm) was greater than 90% for six out of seven planes using the RS-MC, and three out seven for the RS-PBA. The RS-MC algorithm demonstrated improved dosimetric accuracy over the RS-PBA in the presence of homogenous, heterogeneous and anthropomorphic phantoms. The computation performance of the RS-MC was similar to the RS-PBA algorithm. For complex disease sites like breast, head and neck, and lung cancer, the RS-MC algorithm will provide significantly more accurate treatment planning.


Assuntos
Algoritmos , Simulação por Computador , Método de Monte Carlo , Prótons , Planejamento da Radioterapia Assistida por Computador/métodos , Humanos , Imagens de Fantasmas , Radiometria , Dosagem Radioterapêutica
13.
Int J Part Ther ; 3(1): 51-60, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-31772975

RESUMO

PURPOSE: In this report, we present the commissioning and validation results for a commercial proton pencil beam scanning RayStation treatment planning system. MATERIALS AND METHODS: The commissioning data requirements are (1) integrated depth dose curves, (2) spot profiles, (3) absolute dose/monitor unit calibration, and (4) virtual source position. An 8-cm parallel plate chamber was used to measure the integrated depth dose curves by scanning a beam composed of a single spot in a water phantom. The spot profiles were measured at 5 different planes using a 2-dimensional scintillation detector. The absolute dose/monitor unit calibration was based on dose measurements in single-layer fields of size 10 × 10 cm2. The virtual-source position was calculated from the change in spot spacing with the distance from the isocenter. The beam model validation consisted of a comparison against commissioning data as well as a new set of verification measurements. For end-to-end testing, a series of phantom plans were created. These plans were measured at 1 to 3 depths using a 2-dimensional ion chamber array and evaluated for gamma index using the 3% and 3 mm criteria. RESULTS: The maximum deviation for spot sigma measured versus calculated was -0.2 mm. The point-dose measurements for single-layer beams were within ± 3%, except for the largest field size (29 × 29 cm2) and the highest energy (226 MeV). The point doses in the spread-out Bragg peak plans showed a trend in which differences > 3% were seen for ranges > 30 cm, field sizes > 15 × 15 cm2, and depths > 25 cm. For end-to-end testing, 34 planes corresponding to 13 beams were analyzed for gamma index with a minimum pass rate of 92.8%. CONCLUSION: The acceptable verification results and successful end-to-end testing ensured that all components of the treatment planning system were functional and the system was ready for clinical use.

14.
Phys Med Biol ; 58(24): 8709-23, 2013 Dec 21.
Artigo em Inglês | MEDLINE | ID: mdl-24301001

RESUMO

Neutron production is of concern for proton therapy, especially for passive scattering proton beam delivery methods. The levels of neutron dose equivalent vary significantly with system design and treatment parameters. The purpose of this study was to examine neutron dose equivalent per therapeutic dose (H/D) around the Mevion S250 proton therapy system, a novel design of proton therapy systems. The benchmark comparisons between measurement and simulation were found to be within a factor of 2 for most cases. The H/D values were evaluated as a function of various parameters. The results showed that, at a standard reference condition (10 × 10 cm(2) field size, distance 1 m detector-to-isocenter lateral to the primary proton beam direction), the H/D values range from 0.72 to 3.37 mSv Gy(-1) for all configurations studied. The H/D values generally (1) decreased as the neutron detectors moved away from the isocenter, (2) decreased with increasing aperture field sizes, (3) increased with increasing angle from the initial beam axis and (4) were independent of treatment nozzle position. The H/D trends were consistent with other existing passive scattering proton accelerators reported in the literature.


Assuntos
Método de Monte Carlo , Nêutrons , Aceleradores de Partículas , Prótons/efeitos adversos , Doses de Radiação , Exposição Ambiental/análise , Humanos , Terapia com Prótons/efeitos adversos , Radiometria
15.
Phys Med Biol ; 58(16): 5527-39, 2013 Aug 21.
Artigo em Inglês | MEDLINE | ID: mdl-23880635

RESUMO

Treatment plans for patched-field proton therapy may not be clinically acceptable due to the dose heterogeneity introduced in the target when combining the dose distributions from two separate fields. MCNPX simulations were performed for various configurations of the Mevion S250 beamline to determine spread-out Bragg peak dose distributions and patched-field treatment plans delivered using a rotating modulator wheel to depths in the clinically relevant range between 5.0 and 30.0 cm. The dose non-uniformity (DNU) metric was defined as the difference between the maximum and minimum dose relative to the prescription observed in a patched dose distribution. The DNU was first evaluated for dose distributions from a standard delivery using constant beam current and combining through-field lateral dose profiles and with patch-field distal dose profiles. Patch-field distal dose profiles were then optimized using beam current modulation in an attempt to better complement the through-field lateral dose profiles when combined into a patched dose distribution. Using standard deliveries, DNU was 10% or less only when patching lateral profiles 12.5-17.5 cm deep. Significantly greater DNU was observed for patches outside of this range, at times exceeding 35%. Using optimized distal profiles, DNU was reduced to 10% or less for all lateral profiles deeper than 15.0 cm. Optimizing beam current modulation was found to create distal profiles with more gradual dose falloff than found in a standard delivery, allowing optimized distal dose distributions to sum more homogeneously with lateral dose distributions. The hot or cold spots that often appear in patched dose distributions from standard deliveries may therefore be mitigated by optimizing beam current. This method may also be applied to systems other than the Mevion system to further improve patched-field dose homogeneity.


Assuntos
Terapia com Prótons/métodos , Planejamento da Radioterapia Assistida por Computador/métodos , Espalhamento de Radiação , Humanos , Dosagem Radioterapêutica
16.
Radiother Oncol ; 104(1): 23-7, 2012 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-22385795

RESUMO

PURPOSE: To identify risk factors for the development of chest wall (CW) pain after thoracic stereotactic body radiotherapy (SBRT). METHODS AND MATERIALS: A registry of patients with lung lesions treated with lung SBRT was explored to identify patients treated with 54 Gy in three fractions or 50 Gy in five fractions. One hundred and forty-six lesions in 140 patients were identified; complete electronic treatment plans were available on 86 CWs. The CW was contoured as a 3 cm outward expansion from the involved lung. Univariate and multivariate analyses were used to correlate patient, tumor, and dosimetric factors to the development of CW toxicity. RESULTS: CW pain occurred in 22 patients (15.7%). The Kaplan-Meier estimated risk of CW pain at 2 years was 20.1% (95% C.I., 13.2-28.8%). On univariate analysis of patient factors, elevated BMI (p=0.026) and connective tissue disease (p=0.036) correlated with CW pain. The percent of CW receiving 30, 35, or 40 Gy was most predictive of CW pain on multivariate analysis using logistic regression, while V40 alone was predictive using Cox regression. A V30 threshold of 0.7% and V40 threshold of 0.19% was correlated with a 15% risk of CW pain. CONCLUSIONS: We have described patient and dosimetric parameters that correlate with CW pain after lung SBRT. The risk of CW pain may be mitigated by attempting to reduce the relative proportion of CW receiving 30-40 Gy during treatment planning.


Assuntos
Neoplasias Pulmonares/cirurgia , Dor/etiologia , Radiocirurgia/efeitos adversos , Parede Torácica/efeitos da radiação , Adulto , Idoso , Idoso de 80 Anos ou mais , Feminino , Humanos , Modelos Logísticos , Masculino , Pessoa de Meia-Idade , Dosagem Radioterapêutica
17.
Int J Radiat Oncol Biol Phys ; 81(4): e299-303, 2011 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-21477948

RESUMO

PURPOSE: To compare the efficacy of three lung stereotactic body radiotherapy (SBRT) regimens in a large institutional cohort. METHODS: Between 2004 and 2009, 130 patients underwent definitive lung cancer SBRT to a single lesion at the Mallinckrodt Institute of Radiology. We delivered 18 Gy × 3 fractions for peripheral tumors (n = 111) and either 9 Gy × 5 fractions (n = 8) or 10 Gy × 5 fractions (n = 11) for tumors that were central or near critical structures. Univariate and multivariate analysis of prognostic factors was performed using the Cox proportional hazard model. RESULTS: Median follow-up was 11, 16, and 13 months for the 9 Gy × 5, 10 Gy × 5, and 18 Gy × 3 groups, respectively. Local control statistics for Years 1 and 2 were, respectively, 75% and 50% for 9 Gy × 5, 100% and 100% for 10 Gy × 5, and 99% and 91% for 18 Gy × 3. Median overall survival was 14 months, not reached, and 34 months for the 9 Gy × 5, 10 Gy × 5, and 18 Gy × 3 treatments, respectively. No difference in local control or overall survival was found between the 10 Gy × 5 and 18 Gy × 3 groups on log-rank test, but both groups had improved local control and overall survival compared with 9 Gy × 5. Treatment with 9 Gy × 5 was the only independent prognostic factor for reduced local control on multivariate analysis, and increasing age, increasing tumor volume, and poor performance status predicted independently for reduced overall survival. CONCLUSION: Treatment regimens of 10 Gy × 5 and 18 Gy × 3 seem to be efficacious for lung cancer SBRT and provide superior local control and overall survival compared with 9 Gy × 5.


Assuntos
Carcinoma Pulmonar de Células não Pequenas/cirurgia , Neoplasias Pulmonares/cirurgia , Radiocirurgia/métodos , Adulto , Fatores Etários , Idoso , Idoso de 80 Anos ou mais , Análise de Variância , Carcinoma Pulmonar de Células não Pequenas/mortalidade , Carcinoma Pulmonar de Células não Pequenas/patologia , Relação Dose-Resposta à Radiação , Feminino , Seguimentos , Humanos , Avaliação de Estado de Karnofsky , Neoplasias Pulmonares/mortalidade , Neoplasias Pulmonares/patologia , Masculino , Pessoa de Meia-Idade , Radiocirurgia/mortalidade , Carga Tumoral
18.
Phys Med Biol ; 55(23): 6987-98, 2010 Dec 07.
Artigo em Inglês | MEDLINE | ID: mdl-21076196

RESUMO

Theoretical calculations have shown that proton therapy can reduce the incidence of radiation-induced secondary malignant neoplasms (SMN) compared with photon therapy for patients with prostate cancer. However, the uncertainties associated with calculations of SMN risk had not been assessed. The objective of this study was to quantify the uncertainties in projected risks of secondary cancer following contemporary proton and photon radiotherapies for prostate cancer. We performed a rigorous propagation of errors and several sensitivity tests to estimate the uncertainty in the ratio of relative risk (RRR) due to the largest contributors to the uncertainty: the radiation weighting factor for neutrons, the dose-response model for radiation carcinogenesis and interpatient variations in absorbed dose. The interval of values for the radiation weighting factor for neutrons and the dose-response model were derived from the literature, while interpatient variations in absorbed dose were taken from actual patient data. The influence of each parameter on a baseline RRR value was quantified. Our analysis revealed that the calculated RRR was insensitive to the largest contributors to the uncertainty. Uncertainties in the radiation weighting factor for neutrons, the shape of the dose-risk model and interpatient variations in therapeutic and stray doses introduced a total uncertainty of 33% to the baseline RRR calculation.


Assuntos
Neoplasias Induzidas por Radiação/etiologia , Fótons/efeitos adversos , Neoplasias da Próstata/radioterapia , Prótons/efeitos adversos , Radioterapia de Intensidade Modulada/efeitos adversos , Incerteza , Humanos , Masculino , Modelos Biológicos , Nêutrons/efeitos adversos , Fótons/uso terapêutico , Terapia com Prótons , Dosagem Radioterapêutica , Medição de Risco , Espalhamento de Radiação
19.
J Appl Clin Med Phys ; 12(1): 3479, 2010 Dec 04.
Artigo em Inglês | MEDLINE | ID: mdl-21330992

RESUMO

The transfer of radiation therapy data among the various subsystems required for external beam treatments is subject to error. Hence, the establishment and management of a data transfer quality assurance program is strongly recommended. It should cover the QA of data transfers of patient specific treatments, imaging data, manually handled data and historical treatment records. QA of the database state (logical consistency and information integrity) is also addressed to ensure that accurate data are transferred.


Assuntos
Bases de Dados Factuais , Radioterapia (Especialidade)/métodos , Radioterapia/métodos , Relatório de Pesquisa , Humanos , Imagens de Fantasmas , Controle de Qualidade , Radioterapia (Especialidade)/normas , Radioterapia/normas , Dosagem Radioterapêutica
20.
J Appl Clin Med Phys ; 10(4): 16-35, 2009 Sep 02.
Artigo em Inglês | MEDLINE | ID: mdl-19918239

RESUMO

The ever-increasing data demands in a radiation oncology (RO) clinic require medical physicists to have a clearer understanding of the information technology (IT) resource management issues. Clear lines of collaboration and communication among administrators, medical physicists, IT staff, equipment service engineers and vendors need to be established. In order to develop a better understanding of the clinical needs and responsibilities of these various groups, an overview of the role of IT in RO is provided. This is followed by a list of IT related tasks and a resource map. The skill set and knowledge required to implement these tasks are described for the various RO professionals. Finally, various models for assessing one's IT resource needs are described. The exposition of ideas in this white paper is intended to be broad, in order to raise the level of awareness of the RO community; the details behind these concepts will not be given here and are best left to future task group reports.


Assuntos
Sistemas de Apoio a Decisões Clínicas/organização & administração , Conhecimentos, Atitudes e Prática em Saúde , Física Médica , Necessidades e Demandas de Serviços de Saúde/organização & administração , Gestão da Informação/organização & administração , Gestão da Informação/estatística & dados numéricos , Radioterapia (Especialidade)/estatística & dados numéricos , Atitude do Pessoal de Saúde , Humanos , Modelos Teóricos
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