International journal of radiation oncology, biology, physics
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Int. J. Radiat. Oncol. Biol. Phys. · Oct 2005
Reirradiation of recurrent high-grade gliomas using amino acid PET (SPECT)/CT/MRI image fusion to determine gross tumor volume for stereotactic fractionated radiotherapy.
To develop a valid treatment strategy for recurrent high-grade gliomas using stereotactic hypofractionated reirradiation based on biologic imaging and temozolomide. ⋯ This is the first study of biologic imaging optimized SFRT plus temozolomide in recurrent high-grade gliomas. It demonstrates the feasibility and safety of this approach. The most striking result of the trial is the statistically significant longer survival time in the univariate analysis for patients reirradiated using MET-PET or IMT-SPECT/CT/MRI image fusion in the treatment planning, in comparison to patients treated based on MRI/CT alone. Multivariate analysis confirmed a significant survival benefit from multimodal treatment (i.e., addition of temozolomide), despite the limited number of patients. Whether treatment planning with SPECT/PET independently influences survival has to be studied in a larger series of patients.
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Int. J. Radiat. Oncol. Biol. Phys. · Oct 2005
Comparative StudyTreatment planning with protons for pediatric retinoblastoma, medulloblastoma, and pelvic sarcoma: how do protons compare with other conformal techniques?
To calculate treatment plans and compare the dose distributions and dose-volume histograms (DVHs) for photon three-dimensional conformal radiation therapy (3D-CRT), electron therapy, intensity-modulated radiation therapy (IMRT), and standard (nonintensity modulated) proton therapy in three pediatric disease sites. ⋯ In the diseases studied, using various techniques of 3D-CRT, electrons, IMRT, and protons, protons are most optimal in treating retinoblastomas, medulloblastomas (posterior fossa and craniospinal), and pelvic sarcomas. Protons delivered superior target dose coverage and sparing of normal structures. As dose-volume parameters are expected to correlate with acute and late toxicity, proton therapy should receive serious consideration as the preferred technique for the treatment of pediatric tumors.
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Int. J. Radiat. Oncol. Biol. Phys. · Oct 2005
Acute genitourinary toxicity after high-dose-rate (HDR) brachytherapy combined with hypofractionated external-beam radiation therapy for localized prostate cancer: correlation between the urethral dose in HDR brachytherapy and the severity of acute genitourinary toxicity.
Several investigations have revealed that the alpha/beta ratio for prostate cancer is atypically low, and that hypofractionation or high-dose-rate (HDR) brachytherapy regimens using appropriate radiation doses may be expected to yield tumor control and late sequelae rates that are better or at least as favorable as those achieved with conventional radiation therapy. In this setting, we attempted treating localized prostate cancer patients with HDR brachytherapy combined with hypofractionated external beam radiation therapy (EBRT). The purpose of this study was to evaluate the feasibility of using this approach, with special emphasis on the relationship between the severity of acute genitourinary (GU) toxicity and the urethral dose calculated from the dose-volume histogram (DVH) of HDR brachytherapy. ⋯ It was concluded that HDR brachytherapy combined with hypofractionated EBRT is feasible for localized prostate cancer when considered from the viewpoint of acute toxicity. Increase in the fraction dose or reduction in the number of fractions in HDR brachytherapy did not affect the severity of acute GU toxicity, and the volume of urethra receiving an equal or lower radiation dose than the prescribed dose was more closely associated with the grade severity of acute GU toxicity than that receiving a higher than the prescribed dose.
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Int. J. Radiat. Oncol. Biol. Phys. · Oct 2005
Effect of patient setup errors on simultaneously integrated boost head and neck IMRT treatment plans.
The purpose of this study is to determine dose delivery errors that could result from random and systematic setup errors for head-and-neck patients treated using the simultaneous integrated boost (SIB)-intensity-modulated radiation therapy (IMRT) technique. ⋯ Head-and-neck SIB-IMRT dosimetric accuracy would benefit from methods to reduce patient systematic setup errors. When GTV, CTV, or nodal volumes are used for dose evaluation, plans simulated including the effects of random and systematic errors deviate substantially from the nominal plan. The use of PTVs for dose evaluation in the nominal plan improves agreement with evaluated GTV, CTV, and nodal dose values under simulated setup errors. PTV concepts should be used for SIB-IMRT head-and-neck squamous cell carcinoma patients, although the size of the margins may be less than those used with three-dimensional conformal radiation therapy.
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Int. J. Radiat. Oncol. Biol. Phys. · Oct 2005
Dose-volume based ranking of incident beam direction and its utility in facilitating IMRT beam placement.
Beam orientation optimization in intensity-modulated radiation therapy (IMRT) is computationally intensive, and various single beam ranking techniques have been proposed to reduce the search space. Up to this point, none of the existing ranking techniques considers the clinically important dose-volume effects of the involved structures, which may lead to clinically irrelevant angular ranking. The purpose of this work is to develop a clinically sensible angular ranking model with incorporation of dose-volume effects and to show its utility for IMRT beam placement. ⋯ The EUD-based function is a general approach for angular ranking and allows us to identify the potentially good and bad angles for clinically complicated cases. The ranking can be used either as a guidance to facilitate the manual beam placement or as prior information to speed up the computer search for the optimal beam configuration. Thus the proposed technique should have positive clinical impact in facilitating the IMRT planning process.