Intensity-modulated radiation therapy administered to a previously irradiated spine is effective and well-tolerated

Purpose This study sought to discern the clinical outcomes of intensity-modulated radiation therapy (IMRT) administered to the spine in patients who had undergone previous radiotherapy. Methods A total of 81 sites of 74 patients who underwent previous radiotherapy administered to the spine or peri-spine and subsequently received IMRT for the spine were analyzed in this study. The prescribed dose of 80 Gy in a biologically effective dose (BED) of α/β = 10 (BED10) was set as the planning target volume. The constraint for the spinal cord and cauda equine was D0.1 cc ≤ 100 Gy and ≤ 150 Gy of BED for re-irradiation alone and the total irradiation dose, respectively. Results The median follow-up period was 10.1 (0.9–92.1) months after re-irradiation, while the median interval from the last day of the previous radiotherapy to the time of re-irradiation was 15.6 (0.4–210.1) months. Separately, the median prescript dose of re-irradiation was 78.0 (28.0–104.9) of BED10. The median survival time in this study was 13.9 months, with 1-, 3-, and 5-year overall survival rates of 53.7%, 29.3%, and 26.6%, respectively. The 1-, 3-, and 5-year local control rates were 90.8%, 84.0%, and 84.0%, respectively. Neurotoxicity was observed in two of 72 treatments (2.8%) assessed after re-irradiation. Conclusion Re-irradiation for the spine using IMRT seems well-tolerated. Definitive re-irradiation can be a feasible treatment option in patients with the potential for a good prognosis (AU)

Intensity-modulated radiation therapy administered to a previously irradiated spine is effective and well-tolerated.

PURPOSE: This study sought to discern the clinical outcomes of intensity-modulated radiation therapy (IMRT) administered to the spine in patients who had undergone previous radiotherapy. METHODS: A total of 81 sites of 74 patients who underwent previous radiotherapy administered to the spine or peri-spine and subsequently received IMRT for the spine were analyzed in this study. The prescribed dose of 80 Gy in a biologically effective dose (BED) of α/ß = 10 (BED10) was set as the planning target volume. The constraint for the spinal cord and cauda equine was D0.1 cc ≤ 100 Gy and ≤ 150 Gy of BED for re-irradiation alone and the total irradiation dose, respectively. RESULTS: The median follow-up period was 10.1 (0.9-92.1) months after re-irradiation, while the median interval from the last day of the previous radiotherapy to the time of re-irradiation was 15.6 (0.4-210.1) months. Separately, the median prescript dose of re-irradiation was 78.0 (28.0-104.9) of BED10. The median survival time in this study was 13.9 months, with 1-, 3-, and 5-year overall survival rates of 53.7%, 29.3%, and 26.6%, respectively. The 1-, 3-, and 5-year local control rates were 90.8%, 84.0%, and 84.0%, respectively. Neurotoxicity was observed in two of 72 treatments (2.8%) assessed after re-irradiation. CONCLUSION: Re-irradiation for the spine using IMRT seems well-tolerated. Definitive re-irradiation can be a feasible treatment option in patients with the potential for a good prognosis.

Direct impact analysis of multi-leaf collimator leaf position errors on dose distributions in volumetric modulated arc therapy: a pass rate calculation between measured planar doses with and without the position errors.

We propose a new method for analyzing the direct impact of multi-leaf collimator (MLC) leaf position errors on dose distributions in volumetric modulated arc therapy (VMAT). The technique makes use of the following processes. Systematic leaf position errors are generated by directly changing a leaf offset in a linac controller; dose distributions are measured by a two-dimensional diode array; pass rates of the dose difference between measured planar doses with and without the position errors are calculated as a function of the leaf position error. Three different treatment planning systems (TPSs) were employed to create VMAT plans for five prostate cancer cases and the pass rates were compared between the TPSs under various leaf position errors. The impact of the leaf position errors on dose distributions depended upon the final optimization result from each TPS, which was explained by the correlation between the dose error and the average leaf gap width. The presented method determines leaf position tolerances for VMAT delivery for each TPS, which may facilitate establishing a VMAT quality assurance program in a radiotherapy facility.

Stable operation of a 300-m laser interferometer with sufficient sensitivity to detect gravitational-wave events within our galaxy.

TAMA300, an interferometric gravitational-wave detector with 300-m baseline length, has been developed and operated with sufficient sensitivity to detect gravitational-wave events within our galaxy and sufficient stability for observations; the interferometer was operated for over 10 hours stably and continuously. With a strain-equivalent noise level of h approximately 5x10(-21)/sqrt[Hz], a signal-to-noise ratio of 30 is expected for gravitational waves generated by a coalescence of 1.4M-1.4M binary neutron stars at 10 kpc distance. We evaluated the stability of the detector sensitivity with a 2-week data-taking run, collecting 160 hours of data to be analyzed in the search for gravitational waves.

Absolute-length determination of a long-baseline Fabry-Perot cavity by means of resonating modulation sidebands.

A new method has been demonstrated for absolute-length measurements of a long-baseline Fabry-Perot cavity by use of phase-modulated light. This method is based on determination of a free spectral range (FSR) of the cavity from the frequency difference between a carrier and phase-modulation sidebands, both of which resonate in the cavity. Sensitive response of the Fabry-Perot cavity near resonant frequencies ensures accurate determination of the FSR and thus of the absolute length of the cavity. This method was applied to a 300-m Fabry-Perot cavity of the TAMA gravitational wave detector that is being developed at the National Astronomical Observatory, Tokyo. With a modulation frequency of approximately 12 MHz, we successfully determined the absolute cavity length with resolution of 1 microm (3 x 10(-9) in strain) and observed local ground strain variations of 6 x 10(-8).