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Journal of Medical Physics

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[This corrects the article on p. 242 in vol. 31, PMID: 21206640.].
April 2018: Journal of Medical Physics
Vassilis Kouloulias, Aggeliki Nikolakopoulou, Irene Karanasiou, Christos Antypas, Christina Armpilia, Nikolaos Uzunoglou
Concerning clinical trials, intracavitary hyperthermia has already shown antitumor activity and has a potential role in the treatment of prostate cancer. The aim of this study was to document a new intracavitary applicator operating at 433 MHz, designed for transrectal hyperthermia, as well as to assess the specific absorption rate (SAR) distributions in terms of temperature measurements in a soft-tissue phantom. The microwave applicator consists of a dipole-type λ/2, a reflector, and the cooling system. The applicator was placed into a soft-tissue gel-phantom box that was mimicking the dielectric properties of the normal tissue...
April 2018: Journal of Medical Physics
Neelam Sharma, Manoj K Semwal, Abhishek Purkayastha
Purpose: Dose received by organs at risk (OAR) in high-dose-rate (HDR) intracavitary brachytherapy (ICBT) for locally advanced cervical cancer impacts the late toxicity profile of the treatment. In the present study, we analyzed the inter-fraction variations of the minimum dose received by the most irradiated 2cc volumes (D2cc ) of the OARs in ICBT. Methods and Materials: This prospective study included 40 patients with cervical cancer stage FIGO IIB-IVA treated with HDR ICBT and concomitant chemoradiotherapy with Computerized tomography (CT)- based three-dimensional planning...
April 2018: Journal of Medical Physics
Jalil Ur Rehman, Muhammad Isa, Nisar Ahmad, Gulfam Nasar, H M Noor Ul Huda Khan Asghar, Zaheer Abbas Gilani, James C L Chow, Muhammad Afzal, Geoffrey S Ibbott
This analysis estimated secondary cancer risks after volumetric modulated arc therapy (VMAT) and compared those risks to the risks associated with other modalities of head-and-neck (H&N) radiotherapy. Images of H&N anthropomorphic phantom were acquired with a computed tomography scanner and exported via digital imaging and communications in medicine (DICOM) standards to a treatment planning system. Treatment plans were performed using a VMAT dual-arc technique, a nine-field intensity-modulated radiation therapy (IMRT) technique, and a four-field three-dimensional conformal therapy (3DCRT) technique...
April 2018: Journal of Medical Physics
Wui Ann Woon, Paul B Ravindran, Piyasiri Ekayanake, Yivonne Yih Fang Lim
The delivery consistency of a Varian Edge linear accelerator over the entire course of treatment for nasopharynx carcinoma (NPC) and prostate cancer intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT) treatment plans was investigated using four different approaches. Three NPCs and three prostate plans were delivered in 34 and 29 consecutive days, respectively, using a Varian Edge equipped with a 120 high-definition (HD) multileaf collimator (MLC). All deliveries were measured with an electronic portal imaging device (EPID), and MapCheck2 and ArcCheck commercial systems with gamma analysis used to compare the results of all daily measurements against the pretreatment patient-specific quality assurance...
April 2018: Journal of Medical Physics
Christopher Low, Warren Toye, Peter Phung, Christopher Huston
A retrospective study was performed to explore the use of dose volume histogram (DVH) metrics in a patient-specific quality assurance protocol for volumetric modulated arc therapy (VMAT). Fourteen head and neck (HN) and ten brain patients treated with VMAT at the Launceston General Hospital were retrospectively analyzed using the new protocol to identify cases where patient dose errors exceed the established action levels that were not originally detected by either point dose and/or gamma index methods. The Sun Nuclear 3DVH software was used to estimate the dose delivered to the patient volume in terms of DVH dose errors...
April 2018: Journal of Medical Physics
Jinyu Xue, Hesheng Wang, David Barbee, Matthew Schmidt, Indra J Das
Dosimetric accuracy of a volumetric modulated arc therapy (VMAT) plan is directly related to the beam model, particularly with multileaf collimator characterization. Inappropriate dosimetric leaf gap (DLG) value can lead to a suboptimal beam model, with significant failure in patient-specific quality assurance (PSQA) of VMAT plans. This study addressed the systematic issue of beam modeling and developed a practical method to determine the optimal DLG value for a beam model. Several complex VMAT plans were selected for the quality assurance analysis using the variable DLG values...
April 2018: Journal of Medical Physics
Manikandan Arjunan, Sureka Chandra Sekaran, Biplab Sarkar, Sujatha Manikandan
Water is treated as radiological equivalent to human tissue. While this seems justified, there is neither mathematical proof nor sufficient experimental evidence that a water phantom can be treated as equivalent to human tissue. The aim of this work is to simulate and validate a water phantom that is tissue equivalent in terms of the dosimetric characteristics of both water and human tissue Dynamic, intensity-modulated radiotherapy plans for two head and neck, one brain, one pelvis, and three lung/mediastinum cases were chosen for this study...
April 2018: Journal of Medical Physics
P Mohandass, D Khanna, D Manigandan, Narendra Kumar Bhalla, Abhishek Puri
Purpose: Validation of a new software version of a Monte Carlo treatment planning system through comparing plans generated by two software versions in volumetric-modulated arc therapy (VMAT) for lung cancer. Materials and Methods: Three patients who were treated with 60 Gy/30 fractions in Elekta Synergy™ linear accelerator by VMAT technique with 2% statistical uncertainty (SU) were chosen for the study. Multiple VMAT plans were generated using two different software versions of Monaco treatment planning system TPS (V5...
April 2018: Journal of Medical Physics
Victor J Weir, Jie Zhang
Purpose: The purpose of this study is to compare computed tomography (CT) radiation dose measurement methods proposed by TG111, International Electrotechnical Commission (IEC), and a direct dose profile integral (DPI) measurement method. Methods: Pencil and Farmer ion chambers are used for integrating dose profiles at different beam widths in a 60 cm long body phantom. Resulting DPI is used to calculate CT dose index (CTDI) at each beam width. Measurements are also done for a pencil chamber inserted into a 15 cm body phantom at the reference beam width...
April 2018: Journal of Medical Physics
Nao Kuwahata, Hideki Fujita, Hideaki Yamanishi, Eiichiro Okazaki, Haruyuki Fukuda
Purpose: The purpose of the present study was to evaluate the dosimetric benefits of the irregular surface compensator (ISC) technique for whole breast radiotherapy compared with the field-in-field (FIF) technique. Materials and Methods: Radiotherapy was planned using both techniques in 50 breast cancer patients (25 left sided and 25 right sided). The Eclipse treatment planning system (Varian Medical Systems) was used for dose calculations. For the FIF technique, subfields were added to the main fields to reduce hot and cold regions; for the ISC technique, the fluence editor application was used to extend the optimal fluence...
April 2018: Journal of Medical Physics
Parinaz Mehnati, Mehran Arash, Parisa Akhlaghi
The article aims at constructing protective composite shields for breasts in chest computed tomography and investigating the effects of applying these new bismuth composites on dose and image quality. Polyurethane and silicon with 5% of bismuth were fabricated as a protective shield. At first, their efficiency in attenuating the X-ray beam was investigated by calculating the total attenuation coefficients at diagnostic energy range. Then, a physical chest phantom was scanned without and with these shields at tube voltage of 120 kVp, and image parameters together with dose values were studied...
January 2018: Journal of Medical Physics
Ramamoorthy Ravichandran, Bandana Barman, Purnendu Deb Roy, Gopal Datta, Ravi Kannan
With conventional diagnostic X-ray machines with over couch X-ray tubes, it is not possible to obtain anteroposterior (AP) and lateral (Lat) radiographs without changing the posture of the patients. In an old 300 mA X-ray machine with a fluoroscopy screen (12.4 kg) (1995 model), by substituting the screen with suitable counterweight and making provision to take the hoist pillar up to the edge of the wall, we could get isocentric setup for a hospital stretcher kept near the chest stand. This setup provided acceptable AP-Lat radiographs for brachytherapy localization using "Perspex jig" (Nucletron, Netherlands) and field check radiographs in head and neck, esophagus patients for treatment planning...
January 2018: Journal of Medical Physics
Sangutid Thongsawad, Chirasak Khamfongkhruea, Chirapha Tannanonta
The aim of this study was to investigate the potential of jaw tracking with the volumetric-modulated arc therapy (VMAT) to reduce the normal tissue dose. Plans of nasopharynx, lung, and prostate cancers (10 plans for each) were used to perform VMAT with and without jaw tracking. The dose reduction was evaluated in terms of organ doses and integral doses. Organ-dose reduction with jaw tracking was statistically significant in the volume receiving a dose of 5 Gy (V5 ) of bladder, rectum, and lung, the volume receiving a dose of 10 Gy (V10 ) of bladder, rectum, and lung, and the mean dose of lung ( P < 0...
January 2018: Journal of Medical Physics
Zhenia Gopalakrishnan, Raghuram K Nair, P Raghukumar, B Sarin
The aim of this study is to compare the physical wedge (PW) with enhanced dynamic wedge (EDW) to determine the difference in the dose distribution affecting the treated breast and the contralateral breast, lungs, heart, esophagus, spine, and surrounding skin in the radiotherapy of breast cancer. Computed tomography (CT) data sets of 30 breast cancer patients were selected from the database for the study. The treatment plans which were executed with PW were re-planned with EDW without changing the beam parameters...
January 2018: Journal of Medical Physics
Zari Hamivand, Gholamhassan Haddadi, Reza Fardid
Context: Thyroid cancer is the most common endocrine malignancy worldwide. Iodine-131 is used in the treatment of thyroid cancer with dosage of 100 mCi. In the medical applications of ionizing radiation besides the advantages such as diagnosis and treatment of diseases, the risks arising from exposure should be considered as well. Aims: The present study aimed to evaluate the changes in expression levels of apoptotic Bax and Bcl-2 and the ratio of Bax/Bcl-2, in the peripheral blood lymphocytes (PBLs) of patients with differentiated thyroid cancer (DTC)...
January 2018: Journal of Medical Physics
Ines-Ana Jurkovic, Esengul Kocak-Uzel, Abdallah Sherif Radwan Mohamed, Eleftherios Lavdas, Sotirios Stathakis, Nikos Papanikolaou, David C Fuller, Panayiotis Mavroidis
Introduction: This study evaluates treatment plans aiming at determining the expected impact of daily patient setup corrections on the delivered dose distribution and plan parameters in head-and-neck radiotherapy. Materials and Methods: In this study, 10 head-and-neck cancer patients are evaluated. For the evaluation of daily changes of the patient internal anatomy, image-guided radiation therapy based on computed tomography (CT)-on-rails was used. The daily-acquired CT-on-rails images were deformedly registered to the CT scan that was used during treatment planning...
January 2018: Journal of Medical Physics
Ramya Rangarajan
Aim: Since anatomical and geometric variations occur with every fraction, planning, and dose optimization is necessary for every fraction of high-dose rate intracavitary brachytherapy of carcinoma cervix. In this study, we have tried to quantify the differences in doses to organs at risk (OAR) for each fraction of brachytherapy. Methods and Materials: One hundred and seventy computed tomography datasets of cervical cancer patients receiving intracavitary brachytherapy at our institution between January and April 2015 were analyzed...
January 2018: Journal of Medical Physics
Ethan Kendall, Ozer Algan, Salahuddin Ahmad
Introduction: In this article, we report the results of our investigation on comparison of radiobiological aspects of treatment plans with linear accelerator-based intensity-modulated radiation therapy and volumetric-modulated arc therapy for patients having hippocampal avoidance whole-brain radiation therapy. Materials and Methods: In this retrospective study using the dose-volume histogram, we calculated and compared biophysical indices of equivalent uniform dose, tumor control probability, and normal tissue complication probability (NTCP) for 15 whole-brain radiotherapy patients...
January 2018: Journal of Medical Physics
Hao Howard Zhang, Warren D D'Souza
Purpose/Aim: To describe a two-phase intensity-modulated radiation therapy (IMRT) treatment planning approach, that is, promising for reduction of oral mucositis risk in locally advanced head-and-neck cancer. Materials and Methods: Ten locally advanced head-and-neck cancer patients who underwent RT were retrospectively collected. Conventional IMRT and volumetric-modulated arc therapy (VMAT) plans were generated for these patients following clinical protocol. Following the first phase of generating conventional IMRT plans, our approach utilized data from Monte Carlo-based kernel superposition dose calculations corresponding to beam apertures (generated from the conventional IMRT plans) and used an exact mathematical programming-based optimization approach applying linear programming (LP) to dose optimization in the second phase...
January 2018: Journal of Medical Physics
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