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Journal of Medical Physics

Jibon Sharma, Jogesh Sarma, Sushant Agarwal
Radiological imaging is an important modality of today's overall practicum. Imaging can begin as early as the 1st day of life. Neonates are 3-4 times more sensitive to radiation than adults. The purpose of the work was to assess the diagnostic reference level (DRL), the radiation organ dose, and effective organ dose for both sexes from chest anteroposterior radiograph, which is the most common radiographic examination performed at the Neonatal Intensive Care Unit (NICU). The entrance air kerma was measured using a solid-state PIN type detector, and the value was used as the input factor to PCXMC-2...
July 2018: Journal of Medical Physics
Ferdos Albayedh, James C L Chow
This study focused on the imaging in radiotherapy by finding the relationship between the imaging contrast ratio and appropriate gold, iodine, iron oxide, silver, and platinum nanoparticle concentrations; the relationship between the imaging contrast ratio and different beam energies for the different nanoparticle concentrations; the relationship between the contrast ratio and various beam energies for gold nanoparticles; and the relationship between the contrast ratio and different thicknesses of the incident layer of the phantom including variety of gold nanoparticles (GNPs) concentration...
July 2018: Journal of Medical Physics
Sangeetha Shanmugasundaram, Sureka Chandrasekaran
Monte Carlo (MC) simulations are often used in calculations of radiation transport to enable accurate prediction of radiation-dose, even though the computation is relatively time-consuming. In a typical MC simulation, significant computation time is allocated to following non-important events. To address this issue, variance reduction techniques (VRTs) have been suggested for reducing the statistical variance for the same computation time. Among the available MC simulation codes, electron gamma shower (National Research Council of Canada) (EGSnrc) is a general-purpose coupled electron-photon transport code that also features an even-handed, rich set of VRTs...
July 2018: Journal of Medical Physics
Bojarajan Perumal, Harikrishna Etti Sundaresan, Ranganathan Vaitheeswaran
The objective of this work is to compare the planning target volume (PTV)-based intensity-modulated proton therapy (IMPT) plans with robustly optimized IMPT plans using the robust optimization tools available in Pinnacle Treatment Planning System. We performed the study in five cases of different anatomic sites (brain, head and neck, lung, pancreas, and prostate). Pinnacle IMPT nonclinical version was used for IMPT planning. Two types of IMPT plans were created for each case. One is PTV-based conventionally optimized IMPT plan and the other is robustly optimized plan considering setup uncertainties...
July 2018: Journal of Medical Physics
Navideh Aghaei-Amirkhizi, Sodeh Sadjadi, Leila Moghaddam-Banaem, Mitra Athari-Allaf, Fariba Johari-Deha
Purpose: This investigation focuses on biodistribution of irradiated dendrimer encapsulated ytterbium-175 (175 Yb) and to estimate the absorbed dose from intravenous injection of PAMAM encapsulated 175 Yb to human organs. Methods: A dendrimer compound containing an average of 55 Yb+3 ions per dendrimer was prepared and irradiated with neutrons for 2h at 3×1011 s-1 neutron flux. The resulting mixture was injected into a group of tumor bearing mice and the mice were excised, weighed and counted at certain times to study the biodistribution...
July 2018: Journal of Medical Physics
Ramya Rangarajan
Aim: With the advent of computed tomography (CT)-based brachytherapy, it is possible to view the appropriate placement of the applicator within the uterine canal and detect uterine perforation. In this study, the incidence of suboptimal placement of the intracavitary applicator and the resulting dosimetric impact were analyzed and compared with a similar set of ideal applicator placement. Materials and Methods: CT datasets of 282 (141 patients) high dose rate brachytherapy insertions between January and April 2016 were analyzed...
July 2018: Journal of Medical Physics
Bibekananda Mishra, Subhalaxmi Mishra, T Palani Selvam, S T Chavan, S N Pethe
Purpose: Monte Carlo simulation was carried out for a 6 MV flattening filter-free (FFF) indigenously developed linear accelerator (linac) using the BEAMnrc user-code of the EGSnrc code system. The model was benchmarked against the measurements. A Gaussian distributed electron beam of kinetic energy 6.2 MeV with full-width half maximum of 1 mm was used in this study. Methods: The simulation of indigenously developed linac unit has been carried out by using the Monte Carlo-based BEAMnrc user-code of the EGSnrc code system...
July 2018: Journal of Medical Physics
Gaganpreet Singh, Arun S Oinam, Rose Kamal, Bhumika Handa, Vivek Kumar, Bhavana Rai
Introduction: Three-dimensional (3D) treatment planning of patient undergoing radiotherapy uses complex and meticulous computational algorithms. These algorithms use 3D voxel data of the patient to calculate the radiation dose distribution and display it over the CT image dataset for treatment plan evaluation. Aims and Objective: The purpose of the present study is the development and implementation of radiobiological evaluation of the radiotherapy treatment plan incorporating the tissue-specific radiobiological parameters...
July 2018: Journal of Medical Physics
Ganesh Narayanasamy, Dharmin Desai, Sanjay Maraboyina, Jose Penagaricano, Robert Zwicker, Ellis Lee Johnson
Introduction: Radiation Therapy Oncology Group (RTOG) report #0813 and 0915 recommends using D2cm and R50% as plan quality metrics for evaluation of normal tissue sparing in stereotactic body radiation therapy (SBRT) of lung lesion. This study introduces dose falloff gradient (DFG) as a tool for analyzing the dose beyond the planning target volume (PTV) extending into normal tissue structures. In ascertaining the impact of PTV size and SBRT planning techniques in DFG, this study questions the independence of the RTOG recommended metrics...
July 2018: Journal of Medical Physics
(no author information available yet)
[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
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