International Journal of Medical Physics, Clinical Engineering and Radiation Oncology最新文献

{"title":"Quality Control of Dual Energy X-Ray Absorptiometry","authors":"M. A. Reza, A. Paul, H. R. Khan, M. R. Rahman","doi":"10.4236/IJMPCERO.2018.73026","DOIUrl":"https://doi.org/10.4236/IJMPCERO.2018.73026","url":null,"abstract":"Dual energy X-ray absorptiometry (DXA) is a dominant technique for the measurement of bone mineral density (BMD). Quality control (QC) of DXA is very important for the accuracy of results and correct interpretation made by the physician. We have performed the quality control procedures of Lunar DPX Pro bone densitometer according to the manufacturer’s recommendations and current clinical guidelines at the Institute of Nuclear Medicine & Allied Sciences (INMAS), Khulna. The objective of this study is to maximize the performance of the technologist as well as the reliability of the equipment (Linearity, X-ray tube output, Half value layer, Kerma-area product, Radiation field size, Fan angle, Spatial resolution, Room safety). The study result shows that the mean BMD reading is 1.004 g/cm2 with a standard deviation of 0.0035 and co-efficient of variation 0.34%. It also shows that the precision of the technologist is good and there is no malfunctioning in the DXA bone densitometer.","PeriodicalId":14028,"journal":{"name":"International Journal of Medical Physics, Clinical Engineering and Radiation Oncology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2018-08-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82660670","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Technical Note: Identification of CT Texture Features Robust to Tumor Size Variations for Normal Lung Texture Analysis.","authors":"Wookjin Choi,&nbsp;Sadegh Riyahi,&nbsp;Seth J Kligerman,&nbsp;Chia-Ju Liu,&nbsp;James G Mechalakos,&nbsp;Wei Lu","doi":"10.4236/ijmpcero.2018.73027","DOIUrl":"https://doi.org/10.4236/ijmpcero.2018.73027","url":null,"abstract":"<p><p>Normal lung CT texture features have been used for the prediction of radiation-induced lung disease (RILD). For these features to be clinically useful, they should be robust to tumor size variations and not correlated with the normal lung volume of interest, i.e., the volume of the peri-tumoral region (PTR). CT images of 14 lung cancer patients were studied. Different sizes of gross tumor volumes (GTVs) were simulated and placed in the lung contralateral to the tumor. 27 texture features [nine from intensity histogram, eight from the gray-level co-occurrence matrix (GLCM) and ten from the gray-level run-length matrix (GLRM)] were extracted from the PTR. The Bland-Altman analysis was applied to measure the normalized range of agreement (nRoA) for each feature when GTV size varied. A feature was considered as robust when its nRoA was less than the threshold (100%). Sixteen texture features were identified as robust. None of the robust features was correlated with the volume of the PTR. No feature showed statistically significant differences (P<0.05) on GTV locations. We identified 16 robust normal lung CT texture features that can be further examined for the prediction of RILD.</p>","PeriodicalId":14028,"journal":{"name":"International Journal of Medical Physics, Clinical Engineering and Radiation Oncology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2018-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6530926/pdf/nihms-996498.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"37275329","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Enhanced K-Edge Radiography Using a High-Spatial-Resolution Cadmium Telluride Array Detector","authors":"Manabu Watanabe, E. Sato, Yasuyuki Oda, Hodaka Moriyama, Osahiko Hagiwara, H. Matsukiyo, T. Enomoto, S. Kusachi","doi":"10.4236/ijmpcero.2018.73024","DOIUrl":"https://doi.org/10.4236/ijmpcero.2018.73024","url":null,"abstract":"To confirm the imaging effect of a dual-energy (DE) cadmium telluride (CdTe) array detector (XCounter, Actaeon) and to perform fundamental studies on DE computed tomography, we performed enhanced K-edge radiography using iodine (I) and gadolinium (Gd) media. DE radiography was performed using an X-ray generator with a 0.1-mm-diam-focus tube and a 0.5-mm-thick beryllium window, a 1.0-mm-thick aluminum filter for absorbing extremely low-energy photons, and the CdTe array detector with pixel dimensions of 0.1 × 0.1 mm2. Each pixel has a charge-sensitive amplifier and a dual-energy counter, and the event pulses from the amplifier are sent to the counter to determine two threshold energies. The tube current was a maximum value of 0.50 mA, and the tube voltages for I- and Gd-K-edge radiograms were 60 and 80 kV, respectively. In the I-K-edge radiography of a dog-heart phantom at an energy range of 33 - 60 keV, the muscle density increased, and fine coronary arteries were visible. Utilizing Gd-K-edge radiography of a rabbit head phantom at an energy range of 50 - 80 keV, the muscle density increased, and fine blood vessels in the nose were observed at high contrasts. Using the DE array detector, we confirmed the image-contrast variations with changes in the threshold energy.","PeriodicalId":14028,"journal":{"name":"International Journal of Medical Physics, Clinical Engineering and Radiation Oncology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2018-07-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79006775","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Robustness Evaluation of a Novel Proton Beam Geometry for Head and Neck Patients Treated with Pencil Beam Scanning Therapy","authors":"Sheng Huang, Haoyang Liu, Jiajian Shen, H. Zhai, M. Kirk, B. Hartl, A. Lin, J. Mcdonough, S. Both, H. Lin","doi":"10.4236/ijmpcero.2018.73025","DOIUrl":"https://doi.org/10.4236/ijmpcero.2018.73025","url":null,"abstract":"Background: To evaluate the robustness of \u0000head and neck treatment using proton pencil beam scanning (PBS) technique with \u0000respect to range uncertainty (RU) and setup errors (SE), and to establish a \u0000robust PBS planning strategy for future \u0000treatment. Methods and Materials: Ten consecutive patients were planned \u0000with a novel proton field geometry (combination of two posterior oblique fields \u0000and one anterior field with gradient dose match) using single-field uniform \u0000dose (SFUD) planning technique and the proton plans were dosimetrically \u0000compared to two coplanar arc VMAT plans. Robustness of the plans, with \u0000respect to range uncertainties (RU = ± 3% for proton) and setup errors (SE = \u00002.25 mm for proton and VMAT), in terms of deviations to target coverage (CTV \u0000D98%) and OAR doses (max/mean), were evaluated and compared for each patient \u0000under worst case scenarios. Results: Dosimetrically, PBS plans \u0000provided better sparing to larynx (p = 0.005), oral cavity (p -1.1% ± \u00001.3 % vs -0.4% ± 0.7% for nodal CTV and -1.4% ± \u00001.2 vs -0.4% ± 0.5% % for boost CTV). Overall, the \u0000magnitudes of variation of CTV D98% to combined SE and RU were found to be \u0000similar to the impact of the SE on the VMAT plans (-1.6% ± \u00001.9% vs -1.7% ± 1.4% for nodal CTV and -1.9% ± \u00001.6% vs -1.3% ± 1.5% for boost CTV). Compared to VMAT, a \u0000larger range of relative dose deviations were found for OARs in proton plans, \u0000but safe doses were maintained for cord (41.8 ± 3.6 Gy for PBS and 41.7 ± 3.9 \u0000Gy for VMAT) and brainstem (35.2 ± 8.4 Gy for PBS and 36.2 ± 5.1 Gy for VMAT) \u0000in worst case scenarios. Conclusions: Compared to VMAT, proton plans \u0000containing three SFUD fields with superior-inferior gradient dose matching had \u0000improved sparing to larynx, contralateral parotid and oral cavity, while \u0000providing similar robustness of target coverage. Evaluation of OAR dose \u0000robustness showed higher sensitivities to uncertainties for proton plans, but \u0000safe dose levels were maintained for cord and brainstem.","PeriodicalId":14028,"journal":{"name":"International Journal of Medical Physics, Clinical Engineering and Radiation Oncology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2018-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88479638","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Investigation of Hot-Spots in TomoDirect 3DCRT Breast Treatment","authors":"Quan Chen, M. Mallory, E. Crandley, S. Khandelwal","doi":"10.4236/ijmpcero.2018.73031","DOIUrl":"https://doi.org/10.4236/ijmpcero.2018.73031","url":null,"abstract":"Background: Conventional tomotherapy platforms only allow for the delivery of helical IMRT. However the use of IMRT and helical delivery in breast cancer treatment is non-standard. Newer tomotherapy units are equipped with a static-beam mode with 3DCRT capabilities. During the clinical use, we frequently observe hot-spots in the plan that renders the plan clinically unacceptable. The purpose of this study is to investigate the underlying cause of the hot-spots in tomotherapy static-beam breast treatment and possible solutions. Materials/Methods: Theories about the formation of the hot-spot were developed. Eight lumpectomy patients contoured according to RTOG-1005 specifications were also used to illustrate the magnitude of hot-spots under various planning strategies. Two tangential beams were used for the whole breast irradiation plan with prescription dose of 40 Gy in 15 fractions. Results: The hot-spot was identified as the behavior of the optimization engine when part of the target region was blocked. With the current design of tomotherapy’s 3DCRT planning where user adjustment was greatly limited, none of the planning strategies were able to reduce the hot-spots to acceptable levels in the eight patients studied. The best strategy still produced an average of 48.5 Gy (121% of prescription dose) hot-spot dose and 30.4 cc hot-spot volume (volume receiving > 110% prescription dose). It is also shown that the hot-spot was not a result of energy or other physical limitation of the radiation device. By manually adjusting the plan sinogram, the maximum hot-spot dose drops from 121% to 111% and the hot-spot volume drops from 30 cc to 6 cc on average. Conclusions: While TomoDirect 3DCRT showed great promise in breast treatment, treatment planning software improvements may be needed in order to improve the clinical acceptability by reducing hot-spots in normal tissue.","PeriodicalId":14028,"journal":{"name":"International Journal of Medical Physics, Clinical Engineering and Radiation Oncology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2018-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75871701","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Proton Beam Ocular Treatment in Eyes with Intraocular Silicone Oil: Effects on Physical Beam Parameters and Clinical Relevance of Silicone Oil in EYEPLAN Dose-Volume Histograms","authors":"I. Daftari, K. Mishra, Michael I. Seider, B. Damato","doi":"10.4236/IJMPCERO.2018.73029","DOIUrl":"https://doi.org/10.4236/IJMPCERO.2018.73029","url":null,"abstract":"Proton \u0000beam therapy (PBRT) is an essential tool in the treatment of certain ocular \u0000tumors due to its characteristic fall-off and sharp beam parameters at critical \u0000structures. Review of clinical cases in our ocular PBRT program identified \u0000patients with silicone oil used as an intraocular tamponade following pars \u0000plana vitrectomy for repair of retinal detachment. Patient’s eye may be filled \u0000with silicone oil prior to PBRT for an ocular tumor. The objective of this \u0000study was to extend our knowledge of the physical characteristics of proton \u0000beams in silicone oil by measuring dose within a silicone tank itself, hence \u0000better representing the surgical eye, as well as applying the range changes to \u0000EYEPLAN software to estimate clinical impact. The relevant proton beam physical \u0000parameters in silicone oil were studied using a 67.5 MeV un-modulated proton \u0000beam. The beam parameters being defined included: 1) residual range; 2) \u0000peak/plateau ratio; 3) full width at half maximum (FWHM) of the Bragg peak; and \u00004) distal penumbra. Initially, the dose uniformity of the proton beam was \u0000confirmed at 10 mm and 28 mm depth, corresponding to plateau and peak region of \u0000the Bragg peak using Gefchromic film. Once the beam was established as expected, \u0000three sets of measurements of the beam parameters were taken in: a) water (control); b) silicone-1000 oil and water; \u0000and c) silicone-1000 oil only. Central-axis depth-ionization measurements were \u0000performed in a tank (“main tank”) with a 0.1cc ionization chamber (Model IC-18, \u0000Far west) having walls made of Shonka A150 plastic. The tank was 92 mm (length) × 40 mm (height) × 40 mm (depth). The tank had a 0.13 mm thick \u0000kapton entrance window through which the proton beam was incident. The \u0000ionization chamber was always positioned in the center of the circular field of \u0000diameter 30 mm with the phantom surface at isocenter. The ionization chamber \u0000measurements were taken at defined depths in increments of 2 mm, from 0 to 35 \u0000mm. To define the effect of silicone oil on the physical characteristics of \u0000proton beam, the above-defined three sets of measurements were made. In the \u0000first run (a), the Bragg-peak measurements were made in the main tank filled \u0000with water. In the second run (b), a second smaller tank filled with 10 mm \u0000depth silicone oil was placed in front of the water tank and the measurements \u0000were repeated in water. In the third run (c), the water in the main tank was \u0000replaced with silicone oil and the measurements were repeated in silicone \u0000directly (no second tank in runs “a” and “c”). Finally, the effects of change in range on dose distribution based on \u0000the EYEPLAN® treatment planning software of patients with lesions in \u0000close proximity to the disc/macula as well as ciliary body tumors were studied. \u0000The uniformity of the radiation across the treatment volume shows that the \u0000radiation field was uniform within ± 3% at 10 mm depth and within ±4% at 28 mm \u0000depth. Parameters evaluated for the three ","PeriodicalId":14028,"journal":{"name":"International Journal of Medical Physics, Clinical Engineering and Radiation Oncology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2018-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76998322","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Laser Pulse Duration Optimization for Photothermal Therapy with Gold Nanostars","authors":"Juntao Cao","doi":"10.4236/IJMPCERO.2018.73032","DOIUrl":"https://doi.org/10.4236/IJMPCERO.2018.73032","url":null,"abstract":"Photothermal \u0000therapy (PTT), which utilizes light radiation to create localized heating \u0000effect in the targeted areas, is a promising solution for highly specific yet \u0000minimally invasive cancer therapy. PTT uses photothermal agents, which are \u0000usually nanoparticles that absorb strongly in the near-infrared optical window \u0000where minimal tissue absorption occurs. Photothermal agents are also highly \u0000functionalized to target at specific tumor sites. Gold nanostar is an ideal \u0000candidate for photothermal agents, because it not only has a Surface Plasmon \u0000Resonance in the near-infrared, but also can be easily produced and purified, \u0000and is extremely versatile in the drug delivery process. In order to achieve \u0000maximum amount of localized heating, pulse lasers are usually used in laser \u0000ablation processes like photothermal therapy. However, intensive laser radiation \u0000can cause damage to regular tissues as well the nanostructures themselves. \u0000Therefore, identifying the optimal pulse duration to effectively generate localized \u0000heating in the tumorous tissues while keeping the normal tissues and the \u0000nanostructures intact is important to achieving optimal photo-therapeutic results. \u0000This manuscript provides a numerical calculation method with Comsol \u0000Multiphysics to optimize the pulse condition of the gold nanostars under photothermal \u0000therapy settings. Based on results, gold nanostar displays significant \u0000temperature heterogeneity under femtosecond and picosecond laser radiation, \u0000while nanosecond laser only induces rather uniform heating effects across the \u0000entire gold nanostar particle. This finding indicates that femtosecond laser, \u0000which is the most common type of laser used for ablation, is likely to melt the \u0000tip of the gold nanostar before the nanostar body reaches a reasonably high \u0000temperature. Picosecond and nanosecond lasers are much less likely to induce \u0000such dramatic morphology change. This study offers important insight into \u0000finding the optimal condition for photothermal therapy with maximal efficacy \u0000and minimal damage.","PeriodicalId":14028,"journal":{"name":"International Journal of Medical Physics, Clinical Engineering and Radiation Oncology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2018-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88923512","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"An Investigation of the Required MR Bone Attenuation Correction for Quantitative Whole-Body PET/MR Imaging Using Clinical NaF PET/CT Studies","authors":"H. Ai, O. Mawlawi, R. Stafford, J. Bankson, Y. Shao, M. Guindani, R. Wendt","doi":"10.4236/IJMPCERO.2018.73023","DOIUrl":"https://doi.org/10.4236/IJMPCERO.2018.73023","url":null,"abstract":"Tissue-classification-based \u0000attenuation correction strategies have been previously proposed to correct for \u0000bone attenuation in PET/MR imaging and simulated using computed tomography. \u0000However, the complication of voxel averaging uniquely associated with bone has \u0000not been considered explicitly in the past. This study investigated the effect \u0000of voxel averaging between bone and soft tissue in attenuation images and \u0000determined how accurately bone must be detected in MR images in order to \u0000perform acceptable attenuation correction of PET data by using CT-simulated \u0000attenuation correction. We found out that treating bone as soft tissue caused a \u0000mean quantification difference of -9.9% ± 5.5% in all 119 bone lesions. There were no significant \u0000differences between lesions in the pelvis and the vertebrae. The nominal \u0000difference in lesions in the ribs was significantly lower, likely due to the \u0000spatial misregistration between the emission and attenuation images. \u0000Interestingly, a non-monotonic relationship between the bone imaging ability \u0000and the absolute PET quantification accuracy was observed, with the minimal \u0000quantification difference achieved at a BVF around 40% for skull lesions (2.6% \u0000± 2.1%), and 30% for non-skull lesions (1.4% ± 1.1%) and all lesions (1.5% ± \u00001.3%). This study established that a bone classification sensitivity of \u0000approximately 30% BVF is required in order for MR-based attenuation correction \u0000methods to achieve optimal quantification in whole-body PET/MR studies. For \u0000this purpose, higher bone imaging ability of MR may not be necessary.","PeriodicalId":14028,"journal":{"name":"International Journal of Medical Physics, Clinical Engineering and Radiation Oncology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2018-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78322006","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Denoising Projection Data with a Robust Adaptive Bilateral Filter in Low-Count SPECT","authors":"S. Nakabayashi, Takashi Chikamatsu, Takao Okamoto, T. Kaminaga, N. Arai, S. Kumagai, K. Shiraishi, T. Okamoto, Takenori Kobayashi, J. Kotoku","doi":"10.4236/ijmpcero.2018.73030","DOIUrl":"https://doi.org/10.4236/ijmpcero.2018.73030","url":null,"abstract":"Low-count SPECT images are \u0000well known to be smoothed strongly by a Butterworth filter for statistical \u0000noise reduction. Reconstructed images have a low signal-to-noise ratio (SNR) \u0000and spatial resolution because of the removal of high-frequency signal \u0000components. Using the developed robust adaptive bilateral filter (RABF), which \u0000was designed as a pre-stage filter of the Butterworth filter, this study was \u0000conducted to improve SNR without degrading the spatial resolution for low-count \u0000SPECT imaging. The filter can remove noise while preserving spatial resolution. \u0000To evaluate the proposed method, we extracted SNR and spatial resolution in a \u0000phantom study. We also conducted paired comparison for \u0000visual image quality evaluation in a clinical study. Results show that SNR \u0000was increased 1.4 times without degrading the spatial resolution. Visual image \u0000quality was improved significantly (p < 0.01) for clinical low-count data. \u0000Moreover, the accumulation structure became sharper. A structure embedded in \u0000noise emerged. Our method, which denoises without degrading the spatial \u0000resolution for low-count SPECT images, is expected to increase the \u0000effectiveness of diagnosis for low-dose scanning and short acquisition time \u0000scanning.","PeriodicalId":14028,"journal":{"name":"International Journal of Medical Physics, Clinical Engineering and Radiation Oncology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2018-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81621403","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Investigation of Temperature Dependence of Polymer Gels for Use with Scanning Magnetic Resonance Imaging","authors":"H. Kawamura, K. Shinoda, H. Fuse, T. Takanashi, Y. Shimada, Y. Ishimori, M. Monma, K. Miyamoto, H. Sato, T. Fujisaki, T. Sakae, A. Matsumura","doi":"10.4236/ijmpcero.2018.72022","DOIUrl":"https://doi.org/10.4236/ijmpcero.2018.72022","url":null,"abstract":"Polymer gels are three-dimensional dosimetric tools. The purpose of the present study was to investigate the temperature dependence of polymer gels during scanning Magnetic Resonance Imaging. Prepared gels were irradiated with a 6MV X-ray beam at intensities ranging from 0 to 20 Gy in order to investigate their dose-R2 and dose-R1 responses. Irradiated gels were evaluated from 1.5-T magnetic resonance R2 and R1 images for each 5°C change in temperature from 5°C to 41°C, and then the four-field box technique irradiation plan was used to deliver a total dose of 4 Gy using the same beam weight in each direction to the prepared gels. The profile of the dose map generated from the four-field irradiated gel data at 20°C was then compared with the planned data. The dose-R2 response curve was linear up to 20 Gy at 20°C, with a slope of 1.17 Gy-1ds-1. The slopes of the fitted curves of the dose-R2 decreased as gel temperature increased. The slopes of the dose-R1 curves were more parallel than the slopes of the dose-R2 curves between 5 and 41°C. The difference in the full width of half maximum of the gel profile data obtained using the four-field box technique at 20°C and the planned data were below 5% on average. The dose map from the irradiated gels obtained using the dose-R2 curve was the same as that from the planned data under the same temperature conditions. Measurement of difference between various temperatures is significant with dose accuracy. It is suitable to evaluate the gel dosimeter under the thermal equilibrium condition, MRI room temperature from the point of view of the stability of the irradiated gels.","PeriodicalId":14028,"journal":{"name":"International Journal of Medical Physics, Clinical Engineering and Radiation Oncology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2018-05-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80232219","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}