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 (BED
10
) was set as the planning target volume. The constraint for the spinal cord and cauda equine was
D
0.1 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 BED
10
. 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.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
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.
Purpose: The impact of the add‐on micro MLC (mMLC) on the MV and kV isocenters was investigated. Methods: Winston‐Lutz tests was performed with an add‐on mMLC, and a ball bearing (BB) was placed at ...the isocenter given by localization lasers. A square MV field was shaped by the mMLC, and the MV field center position relative to the BB position were measured by a portal imager with different gantry angles. A desirable BB position that minimizes the maximum deviation was obtained as an MV isocenter, and the BB center was aligned onto the revised MV isocenter. Using an on‐board kV imaging system, two‐dimensional BB image was acquired during gantry rotation. The displacement of the kV projection image center from the BB for each gantry angle was recorded as ‘flexmap’. After unmounting the mMLC, Winston‐Lutz test and the flexmap measurement were performed again. A phantom was placed on a couch and cone‐beam CT (CBCT) images were acquired with the two different flexmap data. The set‐up errors were calculated and the differences of required couch translations with each of the flexmap data were obtained. Results: After unmounting the mMLC, the MV field center and the kV image center were shifted approximately 0.4 mm and 0.05 mm upward, respectively. Assuming a perfect MV and kV isocenter coincidence with mMLC using the flexmap for CBCT reconstruction, the MV/kV isocenter discrepancy without the mMLC could be calculated by the difference of the above two values, 0.35 mm which satisfies AAPM TG179 guideline of 1 mm. The largest difference of required couch translations between the two flexmap data was 0.07 mm toward the vertical direction, which agreed well with the kV image center shift of 0.05 mm. Conclusion: The MV and kV isocenters defined with the add‐on mMLC are also applicable to image‐guided VMAT without the mMLC.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
The Large-scale Cryogenic Gravitational wave Telescope (LCGT) is planned as a future Japanese project for gravitational wave detection. A 3 km interferometer will be built in an underground mine at ...Kamioka. Cryogenic sapphire mirrors are going to be employed for the test masses. For the demonstration of LCGT technologies, two prototype interferometers, TAMA300 and CLIO, are being developed. This paper describes the current status of the LCGT project and the two prototype interferometers.
TAMA300 interferometer development Tatsumi, D; Collaboration, the TAMA
Journal of physics. Conference series,
07/2008, Volume:
120, Issue:
3
Journal Article
Peer reviewed
Open access
In recent years, a gravitational wave detector TAMA300 has been upgraded for low frequency noise reduction. Its main subject is to install new seismic attenuation system TAMA SAS for all of four test ...mass mirrors. To benefit from the excellent performance of TAMA SAS, digital control systems are necessary to damp low frequency resonances. However, the digital control system has a demerit of large ADC and DAC noises. To reduce such digital control noises, pre-emphasis and de-emphasis filters are introduced. By applying these systems, the detector noise reduction below 100 Hz was realized. In this paper, I would like to present the current status of the digital control system and of the new analog filters to reduce digital control noises.
Purpose: Due to the weight of the accelerator head and the additional weight of the kV x‐ray tube along with its flat panel detector, flex compensation is required to match the kV cone beam CT image ...center to the MV isocenter. However, the flex compensation has not been compared with and without an add‐on micro multi‐leaf collimator. The purpose of this study is to evaluate the impact of the add‐on micro multi‐leaf collimator on the flex compensation or flex map calculation. Methods: Before attaching an add‐on micro multi‐leaf collimator to Elekta Synergy, MV radiation center was determined by a ball bearing and the flex map was obtained. Subsequently, a micro multi‐leaf collimator was attached to the Synergy head and Winston‐Lutz test was performed to locate the most reasonable MV isocenter. Then a ball bearing was positioned at the MV isocenter., and another flex map was obtained and compared to the previously obtained one acquired before attaching the micro multi‐leaf collimator. Results: MV isocenter discrepancy with and without the micro multi‐leaf collimator was 0.5 mm in GT direction which is less than our tolerance limit. The flex map discrepancy with and without the micro multi‐leaf collimator was not significant, either. Conclusions: We could not detect significant flex map discrepancy with and without the micro multi‐leaf collimator. However, flex map measurement needs to be repeated after fully unifying the method for determining the MV isocenter between the two configurations.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
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