We developed a new device for isocenter detection and verification for use in proton therapy. This device can be used to confirm the isocenters of a room laser, a digital radiography system, and a ...rotational gantry. Agreement between the isocenters of a room laser and a digital radiography system was examined visually. We used the star-shots method for detecting and verifying the rotational gantry isocenter. The gafchromic film could be irradiated with this method using a 2 mm slitted 200 MeV proton beam. The isocenters of a room laser and digital radiography system were in good agreement. The size distribution of the isocenter by the star-shots method was <2 mm, which is the value recommended by the American Association of Physicists in Medicine Task Group 142. This new device can be used to evaluate comprehensive isocenter detection and verification for related equipment. Subsequent checking using this new device will decrease the uncertainty in measuring an isocenter. When using this device, the working time was significantly reduced to about 30 min, including preparation. These measurements should be useful for high accuracy daily treatments.
The purpose of this study was to compare the parameters of the dose-volume histogram (DVH) between proton beam therapy (PBT) and X-ray conformal radiotherapy (XCRT) for locally advanced ...non-small-cell lung cancer (NSCLC), according to the tumor conditions. A total of 35 patients having NSCLC treated with PBT were enrolled in this analysis. The numbers of TNM stage and lymph node status were IIB (n = 3), IIIA (n = 15) and IIIB (n = 17), and N0 (n = 2), N1 (n = 4), N2 (n = 17) and N3 (n = 12), respectively. Plans for XCRT were simulated based on the same CT, and the same clinical target volume (CTV) was used based on the actual PBT plan. The treatment dose was 74 Gy-equivalent dose (GyE) for the primary site and 66 GyE for positive lymph nodes. The parameters were then calculated according to the normal lung dose, and the irradiation volumes of the doses (Vx) were compared. We also evaluated the feasibility of both plans according to criteria: V5 ≥ 42%, V20 ≥ 25%, mean lung dose ≥ 20 Gy. The mean normal lung dose and V5 to V50 were significantly lower in PBT than in XCRT. The differences were greater with the more advanced nodal status and with the larger CTV. Furthermore, 45.7% of the X-ray plans were classified as inadequate according to the criteria, whereas 17.1% of the proton plans were considered unsuitable. The number of inadequate X-ray plans increased in cases with advanced nodal stage. This study indicated that some patients who cannot receive photon radiotherapy may be able to be treated using PBT.
There are few reports on the biological homogeneity within the spread-out Bragg peak (SOBP) of proton beams. Therefore, to evaluate the relative biological effectiveness (RBE) and the oxygen ...enhancement ratio (OER), human salivary gland tumor (HSG) cells were irradiated at the plateau position (position A) and three different positions within a 6-cm-wide SOBP (position B, 26 mm proximal to the middle; position C, middle; position D, 26 mm distal to the middle) using 155-MeV/n proton beams under both normoxic and hypoxic conditions at the Proton Medical Research Center, University of Tsukuba, Japan. The RBE to the plateau region (RBEplateau) and the OER value were calculated from the doses corresponding to 10% survival data. Under the normoxic condition, the RBEplateau was 1.00, 0.99 and 1.09 for positions B, C and D, respectively. Under the hypoxic condition, the RBEplateau was 1.10, 1.06 and 1.12 for positions B, C and D, respectively. The OER was 2.84, 2.60, 2.63 and 2.76 for positions A, B, C and D, respectively. There were no significant differences in either the RBEplateau or the OER between these three positions within the SOBP. In conclusion, biological homogeneity need not necessarily be taken into account for treatment planning for proton beam therapy at the University of Tsukuba.
It is difficult to obtain images of thin slices from measurement of spin–spin relaxation (R2) with magnetic resonance imaging (MRI) using the traditional dose reading method of polymer gel dosimetry. ...In this study, the dose reading method was performed using X-ray computed tomography (CT) for proton beam measurements in order to enable collection of thin slices. In addition, three-dimensional (3D) images of polymer gels were constructed using volume rendering. As a result of acquisition of thin slices, more detailed 3D data consisting of smaller voxel sizes compared to R2 were acquired. However, it was found that with thin slice thicknesses and small voxels, the signal-to-noise ratio around the voxels deteriorated. In addition, the coefficient of variation of non-irradiated gels with CT was smaller than that with R2 MRI.
► Polymer gel dosimetry for proton beam using an X-ray CT scanner was performed.► It is possible to acquire images which data collection of thin slices using CT.► The results which reconstructed 3D images using VR was shown.► Reading method of gel using CT was available to measure 3D dose distribution.► However, we found that at thin small voxel, the SNR around voxels deteriorated.
The purpose of this study is to investigate gel dosimetry for a small irradiation field in stereotactic radiotherapy. Treatment plans were generated by the Pinnacle3 treatment plan system (TPS) for ...three different circular irradiated fields: 10 mm, 15 mm, and 20 mm. The polymer gels were irradiated to 6 Gy with 10-, 15-, and 20-mm-diameter collimators in 4 MV photon beams for stereotactic irradiation following TPS. Irradiated gels were evaluated with MRI at 1.5 T with R2 images. Firstly, the line profile of the irradiated center between TPS plan and the R2 image was compared. In the center profile at a dose calculated from the treatment plan, the full width at half maximum (FWHM) of 10-mm, 15-mm, and 20-mm collimators, were 13 mm, 19 mm, and 25 mm, respectively. In the center profile at R2 from the gel dosimetry, the FWHM were 13 mm, 20 mm, and 23 mm, respectively. Secondly, R2 images were converted to dosimetric maps to apply the gamma evaluation method. Comparison using gamma evaluation in the center of the irradiated plane between TPS plan and the dose map from the R2 image was performed. In gamma evaluation, when 3% and 3 mm criteria were used for comparison of the center plane of dose image from TPS and gel dosimetry, the pass ratio of the gamma criterion between calculated dose from the TPS and the dose map of irradiated gels in stereotactic irradiation was 98.6%. In comparison of the center profile and center plane, results of gel dosimetry were shown to have good agreement with the generated treatment plan dosimetric map for stereotactic irradiation.
As part of the positron source R&D for future e super(+) -- e super(-) colliders and Compton based compact light sources, a high finesse non-planar four-mirror Fabry-Perot cavity has recently been ...installed at the ATF (KEK, Tsukuba, Japan) 1. The first measurements of the gamma ray flux produced with a such cavity using a pulsed laser is presented here. We demonstrate the production of a flux of 2.7 plus or minus 0.2 gamma rays per bunch crossing ( similar to 3 x 10 super(6) gammas per second) during the commissioning.
To assist volcanic hazard mitigation, detection of traces of pyroclastic flows and lahars were attempted by using satellite synthetic aperture radars (SAR). If such information can be obtained ...rapidly, it can help early warnings of the next pyroclastic flows and lahars because these flows often occur repeatedly at similar locations. Using three analytical approaches, two satellite SAR data, namely, the L-band SAR of the Japanese Earth Resource Satellite (JERS-1) and the C-band SAR of the European Remote Sensing Satellite (ERS-1), were tested. These approaches include subtraction of SAR backscatter coefficients, SAR coherence, and SAR interferometry (InSAR). These approaches were validated in the Unzen Volcano with digital elevation model (DEM) subtraction images created from aerial photographs. As a result, it was found that the coherence approach with JERS-1 SAR was highly capable of detecting the traces of the pyroclastic flows and lahars. The traces appeared as either one of two characteristics on the coherence images: low coherence caused by the new traces formed in between a pair of observations or high coherence caused by the recent traces formed before a pair of observations. In contrast, we could not validate applicability of the backscatter approach or the InSAR approach.
In current radiotherapy, neutrons are produced in a photonuclear reaction when incident photon energy is higher than the threshold. In the present study, a method of discriminating the neutron ...component was investigated using an imaging plate (IP) in the neutron-gamma-ray mixed field. Two types of IP were used: a conventional IP for beta- and gamma rays, and an IP doped with Gd for detecting neutrons. IPs were irradiated in the mixed field, and the photo-stimulated luminescence (PSL) intensity of the thermal neutron component was discriminated using an expression proposed herein. The PSL intensity of the thermal neutron component was proportional to thermal neutron fluence. When additional irradiation of photons was added to constant neutron irradiation, the PSL intensity of the thermal neutron component was not affected. The uncertainty of PSL intensities was approximately 11.4 %. This method provides a simple and effective means of discriminating the neutron component in a mixed field.
Measurement of depth-dose distribution of protons by an imaging plate Nohtomi, A; Sakae, T; Terunuma, T ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
10/2003, Letnik:
511, Številka:
3
Journal Article
Recenzirano
By using an imaging plate (IP), we have developed a novel, simple method for depth-dose distribution measurement of clinical proton beams. When protons are obliquely incident upon the IP, the energy ...is deposited closer to the surface of the photo-stimulated luminescence (PSL) material than in the case of normal incidence. On the other hand, the spatial distribution of deposited energy varies considerably with variations in proton energy and results in a dependence of the IP response on linear-energy transfer (LET). Through a combination of these factors, for the oblique incidence, IP response to protons may be relatively enhanced around the Bragg peak because the observed PSL intensity depends on the position (depth) at which the energy is deposited. To examine this geometrical enhancement, a simple calculation is performed. The effect is thought to reduce the dependence of IP response on LET so that the response of an IP may approach that of a parallel-plate ionization chamber. Experimental results are given for protons of various angles of incidence (
θ) on the IP. The proposed method may be useful for conducting quick checks of depth-dose distributions in proton-therapy facilities.
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