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Search Results: 1 - 10 of 13089 matches for " Proton Therapy "
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Preliminary Result of Hyperfractionated High-Dose Proton Beam Radiotherapy for Pediatric Skull Base Chordomas  [PDF]
Masashi Mizumoto, Hiroyoshi Akutsu, Tetsuya Yamamoto, Takashi Fukushima, Yoshiko Oshiro, Daichi Takizawa, Keiichi Tanaka, Masaaki Goto, Toshiyuki Okumura, Akira Matsumura, Koji Tsuboi, Hideyuki Sakurai
Journal of Cancer Therapy (JCT) , 2017, DOI: 10.4236/jct.2017.84028
Abstract: Objective: Proton beam therapy (PBT) may provide good local control for skull base chordoma and reduced toxicities, especially for pediatric patients. Methods: We evaluated the efficacy and safety of hyperfractionated high-dose PBT in6 pediatric patients with newly-diagnosed skull basechordoma who were treated with PBT at our institute from 2011 to 2015. The patients were 5 males and one female, and the median age was 9 years old (range: 5 - 13). All patients received surgery before PBT. The median period between surgery and PBT was 57 days (range: 34 - 129 days). The treatment dose was 78.4 GyE in 56 fractions (twice per day). Results: All patients received PBT without severe acute toxicity. The median follow-up period was 27 months (range: 21 - 71 months). At the last follow-up, all patients were alive and all tumors were well controlled. Acute and late toxicities were generally acceptable, with only grade 1 and 2 events. Late toxicities included growth hormone abnormality and cortical hormone abnormality. One patient needed growth hormone and cortical hormone replacement therapy. Conclusion: Although the number of pediatric patients was small, our overall findings in the 6 cases indicate that hyperfractionated high-dose PBT is safe and effective for pediatric patients with skull base chordoma.
Technological Progress in Radiation Therapy for Brain Tumors  [PDF]
Frederik Jozef Vernimmen, Kathy Rock
Journal of Cancer Therapy (JCT) , 2014, DOI: 10.4236/jct.2014.51005
Abstract:

To achieve a good therapeutic ratio the radiation dose to the tumor should be as high as possible with the lowest possible dose to the surrounding normal tissue. This is especially the case for brain tumors. Technological advancements in diagnostic imaging, dose calculations, and radiation delivery systems, combined with a better understanding of the pathophysiology of brain tumors have led to improvements in the therapeutic results. The widely used technology of delivering 3-D conformal therapy with photon beams (gamma rays) produced by Linear Accelerators has progressed into the use of Intensity modulated radiation therapy (IMRT). Particle beams have been used for several decades for radiotherapy because of their favorable depth dose characteristics. The introduction of clinically dedicated proton beam therapy facilities has improved the access for cancer patients to this treatment. Proton therapy is of particular interest for pediatric malignancies. These technical improvements are further enhanced by the evolution in tumor physiology imaging which allows for improved delineation of the tumor. This in turn opens the potential to adjust the radiation dose to maximize the radiobiological effects. The advances in both imaging and radiation therapy delivery will be discussed.

Proton Therapy Results in the Treatment of Hepatocellular Carcinoma According to the Barcelona-Clinic Liver Cancer (BCLC) Staging System  [PDF]
Francesco Dionisi, Maurizio Amichetti
International Journal of Medical Physics,Clinical Engineering and Radiation Oncology (IJMPCERO) , 2015, DOI: 10.4236/ijmpcero.2015.42013
Abstract:
Proton therapy represents the most advanced form of radiotherapy currently available. Hepato-cellular carcinoma (HCC) has been extensively treated with proton therapy since 1983 with en-couraging results in terms of effectiveness and safety, as reported in recent research articles, systematic reviews and meta-analyses. In this report, we summarized for the first time the results of proton therapy treatment for HCC according with respect to the Barcelona Clinic Liver Cancer Staging System, the most adopted classification system for HCC which provides information on both prognostic prediction and treatment allocation.
Determination of Gamma Angular Distribution from the Shape of Spectral Line for the First Excited State of Carbon Nucleus  [PDF]
K. Rusiecka, A. Wrońska, P. Bednarczyk, D. B?ckenhoff, A. Bubak, S. Feyen, L. Kelleter, A. Konefa?, K. Laihem, J. Leidner, A. Magiera, G. Obrzud, A. Stahl, M. Zi?bliński
World Journal of Nuclear Science and Technology (WJNST) , 2016, DOI: 10.4236/wjnst.2016.61006
Abstract: An experiment investigating gamma emission in hadron therapy was performed at Cyclotron Centre Bronowice (CCB), Cracow, Poland, using two different phantom materials—carbon and poly(methyl methacrylate) PMMA. The measurements were carried out at 70 MeV proton beam energy and the gamma quanta were registered with the use of HP Ge detector with scintillation anti-Compton shielding. Although the primary aim was to establish a solid experimental data base for future applications in prompt gamma imaging, the data have also been analyzed with regards to the position and shape of the spectral line stemming from deexcitation of the carbon excited state 4.44 MeV. Measurements potentially useful to determine the cross section were performed only at 90° laboratory polar angle. However, benefiting from the very good energy resolution it turned out possible to extract information on angular distribution of the C* (4.44 MeV) deexcitation by analyzing the associated line shape. This paper presents the scheme of model calculations assuming the whole process can be divided into two stages: excitation of carbon nuclei by impinging protons and deexcitation of the C* (4.44 MeV) state.
Enhancement of Tumor Regression by Coulomb Nanoradiator Effect in Proton Treatment of Iron-Oxide Nanoparticle-Loaded Orthotopic Rat Glioma Model: Implication of Novel Particle Induced Radiation Therapy  [PDF]
Seung-Jun Seo, Jae-Kun Jeon, Eun-Ju Jeong, Won-Seok Chang, Gi-Hwan Choi, Jong-Ki Kim
Journal of Cancer Therapy (JCT) , 2013, DOI: 10.4236/jct.2013.411A004
Abstract:

Background: Proton-impact metallic nanoparticles, inducing low-energy electrons emission and characteristic X-rays termed as Coulomb nanoradiator effect (CNR), are known to produce therapeutic enhancement in proton treatment on experimental tumors. The purpose of this pilot study was to investigate the effect of CNR-based dose enhancement on tumor growth inhibition in an iron-oxide nanoparticle (FeONP)-loaded orthotopic rat glioma model. Methods: Proton-induced CNR was exploited to treat glioma-bearing SD rat loaded with FeONP by either fully-absorbed single pristine Bragg peak (APBP) or spread-out Bragg peak (SOBP) 45-MeV proton beam. A selected number of rats were examined by MRI before and after treatment to obtain the size and position information for adjusting irradiation field. Tumor regression assay was performed by histological analysis of residual tumor in the sacrificed rats 7 days after treatment. The results of CNR-treated groups were compared with the proton alone control. Results: Intravenous injection of FeONP (300 mg/kg) elevated the tumor concentration of iron up to 37 μg of Fe/g tissue, with a tumor-to-normal ratio of 5, 24 hours after injection. The group receiving FeONP and proton beam showed 65% - 79% smaller tumor volume dose-dependently compared with the proton alone group. The rats receiving FeONP and controlled irradiation field by MR imaging demonstrated more than 95% -

Patient-Specific and Generic Immobilization Devices for Prostate Radiotherapy  [PDF]
Adam D. Melancon, Rajat J. Kudchadker, Richard Amos, Jennifer L. Johnson, Yongbin Zhang, Zhiqian H. Yu, Lifei Zhang, Lei Dong, Andrew K. Lee
International Journal of Medical Physics,Clinical Engineering and Radiation Oncology (IJMPCERO) , 2013, DOI: 10.4236/ijmpcero.2013.24017
Abstract: The purpose of our study was to compare interfractional bony setup variations in pelvic anatomy with two immobilization devices, the patient-specific Vac-Lok and the generic Dual Leg Positioner system (both Civco Medical Solutions, Kalona, IA), for bilateral proton radiotherapy of the prostate. Two groups of 10 patients were studied. Computed tomography (CT) was performed three times a week, yielding 233 CT image sets for the vacuum system group and 252 for the other group. The translational shifts of the pelvic bone and prostate and rotation of the upper femurs of the femoral heads with respect to the simulation CT images were analyzed. Along the anterior-posterior and lateral axes, mean and systematic translational variations of the pelvic bone and prostate, relative to skin fiducials, were significantly lower in the Vac-Lok group (all p < 0.01) than in the Dual Leg Positioner group. Abduction of the upper femur, the dominant rotation, had random rotational variations of 1.9° and 2.0° and systematic rotations of 3.1° and 2.9° for the vacuum and generic system groups, respectively. Femoral abduction was highly correlated with anterior prostate displacement for both femurs in both groups (p < 0.01). We conclude that image guidance may be needed to correct systematic translation introduced during simulation CT, particularly with the generic immobilization system. High degrees of femoral rotation may introduce prostate translation and distal misalignment of lateral proton beams with the prostate.
Dose Distribution of Electrons from Gold Nanoparticles by Proton Beam Irradiation  [PDF]
Jihun Kwon, Kenneth Sutherland, Takayuki Hashimoto, Hiroyuki Date
International Journal of Medical Physics,Clinical Engineering and Radiation Oncology (IJMPCERO) , 2015, DOI: 10.4236/ijmpcero.2015.41007
Abstract:
Purpose: In radiation therapy, gold nanoparticles (GNPs) are regarded as a promising radiosensitizer candidate. Several studies have revealed a dose enhancement by GNPs in X-ray and even proton irradiation. However, these studies have been limited to the depth direction. The dose distribution in both depth and lateral directions is crucial to evaluate the full radio sensitizing effect. The purpose of this study is to estimate the dose distribution around a GNP in terms of ejected electrons. Methods: The Geant4 Monte Carlo simulation toolkit was used to evaluate the energy deposition of electrons produced by a GNP. A 20 nm diameter spherical GNP was located in a water box and proton beams were incident unidirectionally. The energy deposition and location of produced electrons were tallied by 5 nm width water slabs at a variety of depths behind the GNP. The radial dose distribution was obtained in each slab. Results: The largest radial dose was observed in the slab closest to the GNP. At the slabs deeper than 90 nm, the dose in the radial direction within 10 nm from the beam direction was found to be smaller than that without GNP. This is because the presence of a GNP decreases the dose behind the GNP, forming a dose shadow. The dose enhancement both in depth and lateral directions was shown in surrounding areas. The area of distribution became larger as the absorbed dose decreased. Conclusion: The dose distribution around a GNP was estimated by a simulation study. The dose enhancement was observed in both the lateral and depth directions. This study will enable us to make use of GNPs as a radiosensitizer in proton therapy.
Biological Dose Estimation Model for Proton Beam Therapy  [PDF]
Vladimir Anferov, Indra J. Das
International Journal of Medical Physics,Clinical Engineering and Radiation Oncology (IJMPCERO) , 2015, DOI: 10.4236/ijmpcero.2015.42019
Abstract:
Purpose: The recommended value for the relative biological effectiveness (RBE) of proton beams is currently assumed to be 1.1. However, there is increasing evidence that RBE increases towards the end of proton beam range that may increase the biological effect of proton beam in the distal regions of the dose deposition. Methods: A computational approach is presented for estimating the biological effect of the proton beam. It includes a method for calculating the dose averaged linear energy transfer (LET) along the measured Bragg peak and published LET to RBE conversion routine. To validate the proposed method, we have performed Monte Carlo simulations of the pristine Bragg peak at various beam energies and compared the analysis with the simulated results. A good agreement within 5% is observed between the LET analysis of the modeled Bragg peaks and Monte Carlo simulations. Results: Applying the method to the set of Bragg peaks measured at a proton therapy facility we have estimated LET and RBE values along each Bragg peak. Combining the individual RBE-weighted Bragg peaks with known energy modulation weights we have calculated the RBE-weighted dose in the modulated proton beam. The proposed computational method provides a tool for calculating dose averaged LET along the measured Bragg peak. Conclusions: Combined with a model to convert LET into RBE, this method enables calculation of RBE-weighted dose both in pristine Bragg peak and in modulated beam in proton therapy.
An Overview of the Control System for Dose Delivery at the UCSF Dedicated Ocular Proton Beam  [PDF]
Inder K. Daftari, Kavita K. Mishra, Rajinder P. Singh, Dan J. Shadoan, Theodore L. Phillips
International Journal of Medical Physics,Clinical Engineering and Radiation Oncology (IJMPCERO) , 2016, DOI: 10.4236/ijmpcero.2016.54025
Abstract: Since 1978, the University of California San Francisco (UCSF) Ocular Tumor Program has been using particle therapy for treating ocular patients with malignant as well as benign eye disease. Helium ion beams were used initially and were produced by two synchrotron-based systems: first by the 184-inch synchro-cyclotron and later by the Bevalac, at the Lawrence Berkeley National Laboratory (LBNL). Since 1994, protons, produced by a cyclotron-based system at the Crocker Nuclear Laboratory (CNL) Eye Treatment Facility (ETF), have been used for this purpose. The CNL cyclotron produces a 67.5 MeV beam, allowing for a uniquely homogeneous beam for eye treatment, without degradation of the beam or manipulation of the beam line. This paper describes, in detail, the control system for beam delivery, as implemented for measuring and delivering the radiation to ocular tumors at CNL. The control system allows for optimal delivery and rapid termination of the irradiation after the desired dose is achieved. In addition, several safeguard systems are discussed, as these are essential for such a system in the event of failure of software, electronics, or other hardware. The QA analysis shows that the total range of the proton beam is 30.7 ± 1.0 mm in water at iso-center. The beam distal penumbra (80% - 20%) is 1.1 mm for a range-modulated beam at a collimator to iso-center distance of 50 mm. Daily QA checks confirm that the range and modulation is within 0.1 mm. The beam flatness and symmetry in a 25 mm diameter beam are ±1% - 2%. Variation in the daily dosimetry system, as compared to standard dosimetry, is within ±3.5%, with a mean variation of 0.72(±1.9)% and 0.85(±2.3)% for segmented transmission ionization chambers IC1 (upstream) and IC2 (downstream), respectively. From May 1994 to the end of 2015, UCSF has treated 1838 proton ocular patients at the Davis ETF. During this period, no treatments were missed due to any cyclotron or control system failures. The overall performance, maintenance, and quality assurance of the cyclotron and the ocular control system have been excellent.
Robustness Evaluation of a Novel Proton Beam Geometry for Head and Neck Patients Treated with Pencil Beam Scanning Therapy  [PDF]
Sheng Huang, Haoyang Liu, Jiajian Shen, Huifang Zhai, Maura Kirk, Brett Hartl, Alexander Lin, James McDonough, Stefan Both, Haibo Lin
International Journal of Medical Physics,Clinical Engineering and Radiation Oncology (IJMPCERO) , 2018, DOI: 10.4236/ijmpcero.2018.73025
Abstract: Background: To evaluate the robustness of head and neck treatment using proton pencil beam scanning (PBS) technique with respect to range uncertainty (RU) and setup errors (SE), and to establish a robust PBS planning strategy for future treatment. Methods and Materials: Ten consecutive patients were planned with a novel proton field geometry (combination of two posterior oblique fields and one anterior field with gradient dose match) using single-field uniform dose (SFUD) planning technique and the proton plans were dosimetrically compared to two coplanar arc VMAT plans. Robustness of the plans, with respect to range uncertainties (RU = ± 3% for proton) and setup errors (SE = 2.25 mm for proton and VMAT), in terms of deviations to target coverage (CTV D98%) and OAR doses (max/mean), were evaluated and compared for each patient under worst case scenarios. Results: Dosimetrically, PBS plans provided better sparing to larynx (p = 0.005), oral cavity (p < 0.001) and contralateral parotid (p = 0.004) when compared to VMAT. CTV D98% variations were higher from SE than from RU for proton plans (-1.1% ± 1.3 % vs -0.4% ± 0.7% for nodal CTV and -
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