Journal of Medical Physics / Association of Medical Physicists of India最新文献

{"title":"In regard to “Setup error analysis in helical tomotherapy based image-guided radiation therapy treatments”","authors":"S. Yartsev","doi":"10.4103/0971-6203.177275","DOIUrl":"https://doi.org/10.4103/0971-6203.177275","url":null,"abstract":"Sir, I read with interest the paper of Dr. Thondykandy et al. in the latest issue of your journal.[1] The current rapid introduction of pretreatment (tomotherapy megavoltage computed tomography (CT) and cone-beam CT on Varian and Elekta linacs) and in-treatment (CyberKnife, ViewRay) image guidance (IG) needs a careful assessment of these technologies in order to establish their optimal usage. The authors investigated the position correction shifts for 102 patients treated with helical tomotherapy using megavoltage CT for matching the patient position of the day to the planning CT study. There is no information on how planning CT studies were obtained, but for patients with a significant target motion, the usage of fast helical CT studies for planning may be suboptimal for IG purpose, and untagged average studies should be recommended. Systematic and random errors were evaluated and used for treatment margin calculation as per van Herk et al.[2] However, the authors’ concluded that the clinical margins used in their hospital were adequate enough for the brain, head and neck, and lung cancer patients while being out of clinical margins for the pelvis and cervical spine injury patients, may be confusing. The margins calculated by Thondykandy et al.[1] correspond only to a part of the total planning target volume (PTV) construction accounting for interfraction motion as explained in BIR publication.[3] These margin values can be used to account for positioning errors if no pretreatment IG is performed.","PeriodicalId":143694,"journal":{"name":"Journal of Medical Physics / Association of Medical Physicists of India","volume":"155 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123176908","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":"Dosimetric comparison of three-dimensional conformal radiotherapy, intensity modulated radiotherapy, and helical tomotherapy for lung stereotactic body radiotherapy","authors":"R. Kinhikar, Y. Ghadi, P. Sahoo, S. Laskar, D. Deshpande, S. Shrivastava, J. Agarwal","doi":"10.4103/0971-6203.170792","DOIUrl":"https://doi.org/10.4103/0971-6203.170792","url":null,"abstract":"To compare the treatment plans generated with three-dimensional conformal radiation therapy (3DCRT), intensity modulated radiotherapy (IMRT), and helical tomotherapy (HT) for stereotactic body radiotherapy of lung, twenty patients with medically inoperable (early nonsmall cell lung cancer) were retrospectively reviewed for dosimetric evaluation of treatment delivery techniques (3DCRT, IMRT, and HT). A dose of 6 Gy per fraction in 8 fractions was prescribed to deliver 95% of the prescription dose to 95% volume of planning target volume (PTV). Plan quality was assessed using conformity index (CI) and homogeneity index (HI). Doses to critical organs were assessed. Mean CI with 3DCRT, IMRT, and HT was 1.19 (standard deviation [SD] 0.13), 1.18 (SD 0.11), and 1.08 (SD 0.04), respectively. Mean HI with 3DCRT, IMRT, and HT was 1.14 (SD 0.05), 1.08 (SD 0.02), and 1.07 (SD 0.04), respectively. Mean R50% values for 3DCRT, IMRT, and HT was 8.5 (SD 0.35), 7.04 (SD 0.45), and 5.43 (SD 0.29), respectively. D2cmwas found superior with IMRT and HT. Significant sparing of critical organs can be achieved with highly conformal techniques (IMRT and HT) without compromising the PTV conformity and homogeneity.","PeriodicalId":143694,"journal":{"name":"Journal of Medical Physics / Association of Medical Physicists of India","volume":"40 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128986201","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":"Expanding horizons in medical physics: Standardization to visualization and quantitative assessment based personalized treatments","authors":"B. Paliwal","doi":"10.4103/0971-6203.170795","DOIUrl":"https://doi.org/10.4103/0971-6203.170795","url":null,"abstract":"","PeriodicalId":143694,"journal":{"name":"Journal of Medical Physics / Association of Medical Physicists of India","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128713258","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":"Impact of dose rate on accuracy of intensity modulated radiation therapy plan delivery using the pretreatment portal dosimetry quality assurance and setting up the workflow at hospital levels","authors":"K. Kaviarasu, N. A. N. Raj, K. Murthy, A. G. Babu, B. D. Prasad","doi":"10.4103/0971-6203.170786","DOIUrl":"https://doi.org/10.4103/0971-6203.170786","url":null,"abstract":"The aim of this study was to examine the impact of dose rate on accuracy of intensity modulated radiation therapy (IMRT) plan delivery by comparing the gamma agreement between the calculated and measured portal doses by pretreatment quality assurance (QA) using electronic portal imaging device dosimetry and creating a workflow for the pretreatment IMRT QA at hospital levels. As the improvement in gamma agreement leads to increase in the quality of IMRT treatment delivery, gamma evaluation was carried out for the calculated and the measured portal images for the criteria of 3% dose difference and 3 mm distance-to-agreement (DTA). Three gamma parameters: Maximum gamma, average gamma, and percentage of the field area with a gamma value>1 .0 were analyzed. Three gamma index parameters were evaluated for 40 IMRT plans (315 IMRT fields) which were calculated for 400 monitor units (MU)/min dose rate and maximum multileaf collimator (MLC) speed of 2.5 cm/s. Gamma parameters for all 315 fields are within acceptable limits set at our center. Further, to improve the gamma results, we set an action level for this study using the mean and standard deviation (SD) values from the 315 fields studied. Forty out of 315 IMRT fields showed low gamma agreement (gamma parameters>2 SD as per action level of the study). The parameters were recalculated and reanalyzed for the dose rates of 300, 400 and 500 MU/min. Lowering the dose rate helped in getting an enhanced gamma agreement between the calculated and measured portal doses of complicated fields. This may be attributed to the less complex motion of MLC over time and the MU of the field/segment. An IMRT QA work flow was prepared which will help in improving the quality of IMRT delivery.","PeriodicalId":143694,"journal":{"name":"Journal of Medical Physics / Association of Medical Physicists of India","volume":"229 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122508848","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":"Reply to the comment of S. VanDyk and K. Narayan on the editorial “IMRT, IGRT and other high technology become standard in external beam radiotherapy: But is image-guided brachytherapy for cervical cancer too expensive?” J Med Phys 2015;40:1-4","authors":"S. Jamema, C. Kirisits","doi":"10.4103/0971-6203.170794","DOIUrl":"https://doi.org/10.4103/0971-6203.170794","url":null,"abstract":"Sir, To begin with, the core point of the editorial (even the title) is about the general issue of the treatment of cervix cancer patients, where the main priority is to establish simple methods, while for other disease sites, the state of the art is constantly improving, especially with external beam methods. The short paragraph that was dedicated to the ultrasound (US) is well deserving, considering that the editorial is not about the US alone, but about the various other issues associated with the image‐based brachytherapy (IGABT) of cervical cancer.","PeriodicalId":143694,"journal":{"name":"Journal of Medical Physics / Association of Medical Physicists of India","volume":"2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115295462","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":"Evaluation of external beam hardening filters on image quality of computed tomography and single photon emission computed tomography/computed tomography","authors":"Nivedita Rana, D. Rawat, Madan Parmar, D. Dhawan, A. K. Bhati, B. Mittal","doi":"10.4103/0971-6203.170790","DOIUrl":"https://doi.org/10.4103/0971-6203.170790","url":null,"abstract":"This study was undertaken to evaluate the effect of external metal filters on the image quality of computed tomography (CT) and single photon emission computed tomography (SPECT)/CT images. Images of Jaszack phantom filled with water and containing iodine contrast filled syringes were acquired using CT (120 kV, 2.5 mA) component of SPECT/CT system, ensuring fixation of filter on X-ray collimator. Different thickness of filters of Al and Cu (1 mm, 2 mm, 3 mm, and 4 mm) and filter combinations Cu 1 mm, Cu 2 mm, Cu 3 mm each in combination with Al (1 mm, 2 mm, 3 mm, and 4 mm), respectively, were used. All image sets were visually analyzed for streak artifacts and contrast to noise ratio (CNR) was derived. Similar acquisition was done using Philips CT quality control (QC) phantom and CNR were calculated for its lexan, perspex, and teflon inserts. Attenuation corrected SPECT/CT images of Jaszack phantom filled with 444–555 MBq (12–15 mCi) of 99mTc were obtained by applying attenuation correction map generated by hardened X-ray beam for different filter combination, on SPECT data. Uniformity, root mean square (rms) and contrast were calculated in all image sets. Less streak artifacts at iodine water interface were observed in images acquired using external filters as compared to those without a filter. CNR for syringes, spheres, and inserts of Philips CT QC phantom was almost similar to Al 2 mm, Al 3 mm, and without the use of filters. CNR decreased with increasing copper thickness and other filter combinations. Uniformity and rms were lower, and value of contrast was higher for SPECT/CT images when CT was acquired with Al 2 mm and 3 mm filter than for images acquired without a filter. The study suggests that for Infinia Hawkeye 4, SPECT/CT system, Al 2 mm, and 3 mm are the optimum filters for improving image quality of SPECT/CT images of Jaszack or Philips CT QC phantom keeping other parameters of CT constant.","PeriodicalId":143694,"journal":{"name":"Journal of Medical Physics / Association of Medical Physicists of India","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134040068","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":"Inter-departmental dosimetry audits – development of methods and lessons learned","authors":"D. Eaton, S. Bolton, R. Thomas, C. Clark","doi":"10.4103/0971-6203.170791","DOIUrl":"https://doi.org/10.4103/0971-6203.170791","url":null,"abstract":"External dosimetry audits give confidence in the safe and accurate delivery of radiotherapy. In the United Kingdom, such audits have been performed for almost 30 years. From the start, they included clinically relevant conditions, as well as reference machine output. Recently, national audits have tested new or complex techniques, but these methods are then used in regional audits by a peer-to-peer approach. This local approach builds up the radiotherapy community, facilitates communication, and brings synergy to medical physics.","PeriodicalId":143694,"journal":{"name":"Journal of Medical Physics / Association of Medical Physicists of India","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131550201","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":"Use of image guided radiation therapy techniques and imaging dose measurement at Indian hospitals: A survey","authors":"S. Deshpande, D. Dhote, R. Kumar, S. Naidu, A. Sutar, V. Kannan","doi":"10.4103/0971-6203.170788","DOIUrl":"https://doi.org/10.4103/0971-6203.170788","url":null,"abstract":"A national survey was conducted to obtain information about the use of image-guided radiotherapy (IGRT) techniques and IGRT dose measurement methods being followed at Indian radiotherapy centers. A questionnaire containing parameters relevant to use of IGRT was prepared to collect the information pertaining to (i) availability and type of IGRT delivery system, (ii) frequency of image acquisition protocol and utilization of these images for different purpose, and (iii) imaging dose measurement. The questionnaire was circulated to 75 hospitals in the country having IGRT facility, and responses of 51 centers were received. Su rvey results showed that among surveyed hospitals, 86% centers have IGRT facility, 78% centers have kilo voltage three-dimensional volumetric imaging. 75% of hospitals in our study do not perform computed tomography dose index measurements and 89% of centers do not perform patient dose measurements. Moreover, only 29% physicists believe IGRT dose is additional radiation burden to patient. This study has brought into focus the need to design a national protocol for IGRT dose measurement and development of indigenous tools to perform IGRT dose measurements.","PeriodicalId":143694,"journal":{"name":"Journal of Medical Physics / Association of Medical Physicists of India","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122784210","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":"Derivative based sensitivity analysis of gamma index","authors":"B. Sarkar, A. Pradhan, T. Ganesh","doi":"10.4103/0971-6203.170789","DOIUrl":"https://doi.org/10.4103/0971-6203.170789","url":null,"abstract":"Originally developed as a tool for patient-specific quality assurance in advanced treatment delivery methods to compare between measured and calculated dose distributions, the gamma index (γ) concept was later extended to compare between any two dose distributions. It takes into effect both the dose difference (DD) and distance-to-agreement (DTA) measurements in the comparison. Its strength lies in its capability to give a quantitative value for the analysis, unlike other methods. For every point on the reference curve, if there is at least one point in the evaluated curve that satisfies the pass criteria (e.g., δDD = 1%, δDTA = 1 mm), the point is included in the quantitative score as \"pass.\" Gamma analysis does not account for the gradient of the evaluated curve - it looks at only the minimum gamma value, and if it is <1, then the point passes, no matter what the gradient of evaluated curve is. In this work, an attempt has been made to present a derivative-based method for the identification of dose gradient. A mathematically derived reference profile (RP) representing the penumbral region of 6 MV 10 cm × 10 cm field was generated from an error function. A general test profile (GTP) was created from this RP by introducing 1 mm distance error and 1% dose error at each point. This was considered as the first of the two evaluated curves. By its nature, this curve is a smooth curve and would satisfy the pass criteria for all points in it. The second evaluated profile was generated as a sawtooth test profile (STTP) which again would satisfy the pass criteria for every point on the RP. However, being a sawtooth curve, it is not a smooth one and would be obviously poor when compared with the smooth profile. Considering the smooth GTP as an acceptable profile when it passed the gamma pass criteria (1% DD and 1 mm DTA) against the RP, the first and second order derivatives of the DDs (δD', δD\") between these two curves were derived and used as the boundary values for evaluating the STTP against the RP. Even though the STTP passed the simple gamma pass criteria, it was found failing at many locations when the derivatives were used as the boundary values. The proposed derivative-based method can identify a noisy curve and can prove to be a useful tool for improving the sensitivity of the gamma index.","PeriodicalId":143694,"journal":{"name":"Journal of Medical Physics / Association of Medical Physicists of India","volume":"2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129063238","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":"Dose and linear energy transfer distributions of primary and secondary particles in carbon ion radiation therapy: A Monte Carlo simulation study in water","authors":"Daniel A Johnson, Yong Chen, Salahuddin Ahmad","doi":"10.4103/0971-6203.170785","DOIUrl":"https://doi.org/10.4103/0971-6203.170785","url":null,"abstract":"The factors influencing carbon ion therapy can be predicted from accurate knowledge about the production of secondary particles from the interaction of carbon ions in water/tissue-like materials, and subsequently the interaction of the secondary particles in the same materials. The secondary particles may have linear energy transfer (LET) values that potentially increase the relative biological effectiveness of the beam. Our primary objective in this study was to classify and quantify the secondary particles produced, their dose averaged LETs, and their dose contributions in the absorbing material. A 1 mm diameter carbon ion pencil beam with energies per nucleon of 155, 262, and 369 MeV was used in a geometry and tracking 4 Monte Carlo simulation to interact in a 27 L water phantom containing 3000 rectangular detector voxels. The dose-averaged LET and the dose contributions of primary and secondary particles were calculated from the simulation. The results of the simulations show that the secondary particles that contributed a major dose component had LETs <100 keV/µm. The secondary particles with LETs >600 keV/µm contributed only <0.3% of the dose.","PeriodicalId":143694,"journal":{"name":"Journal of Medical Physics / Association of Medical Physicists of India","volume":"35 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128063879","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}