A novel method for radiotherapy patient identification using surface imaging.
Abstract Performing a procedure on the wrong patient or site is one of the greatest errors that can occur in medicine. The addition of automation has been shown to reduce errors in many processes. In this work we explore the use of an automated patient identification process using optical surface imaging for radiotherapy treatments. Surface imaging uses visible light to align the patient to a reference surface in the treatment room. It is possible to evaluate the similarity between a daily set-up surface image and the reference image using distance to agreement between the points on the two surfaces. The higher th...
Source: Journal of Applied Clinical Medical Physics - April 15, 2016 Category: Physics Authors: Wiant DB, Verchick Q, Gates P, Vanderstraeten CL, Maurer JM, Hayes TL, Liu H, Sintay BJ Tags: J Appl Clin Med Phys Source Type: research

In vivo 1H MR spectroscopy using 3 Tesla to investigate the metabolic profiles of joint fluids in different types of knee diseases.
The objective of this study, therefore, was to assess the ability of proton MRS to identify the apparent heterogeneous characteristics of metabolic spectra in the joint fluid regions in human knees using a high-field MRI system. Eighty-four patients with effusion lesions who were referred for routine knee MR imaging underwent proton MRS with point-resolved, single-voxel MR spectroscopy using a clinical 3.0 Tesla MRI system. Thirty-eight patients were confirmed to have the following: degenerative osteoarthritis, 21 patients (Group 1); traumatic diseases, 12 patients (Group 2); infectious diseases, 4 patients and an inflamma...
Source: Journal of Applied Clinical Medical Physics - April 15, 2016 Category: Physics Authors: Jin W, Woo DC, Jahng GH Tags: J Appl Clin Med Phys Source Type: research

A time of transition for the JACMP.
PMID: 27074492 [PubMed - in process] (Source: Journal of Applied Clinical Medical Physics)
Source: Journal of Applied Clinical Medical Physics - April 15, 2016 Category: Physics Authors: Mills MD, Halvorsen PH, Solberg TD Tags: J Appl Clin Med Phys Source Type: research

A time of transition for the JACMP
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Source: Journal of Applied Clinical Medical Physics - March 15, 2016 Category: Physics Source Type: research

Development of a residency program in radiation oncology physics: an inverse planning approach
In this report, we identify and discuss the implementation of, and the essential components of, a radia­tion oncology physics residency designed to produce knowledgeable and effective clinical physicists for today’s safety-conscious and collaborative work environment. Our approach is that of inverse planning, by now familiar to all radiation oncology physicists, in which objectives and constraints are identified prior to the design of the program. Our inverse planning objectives not only include those associated with traditional residencies (i.e., clinical physics knowledge and critical clinical skills), but also...
Source: Journal of Applied Clinical Medical Physics - March 8, 2016 Category: Physics Source Type: research

In vivo 1H MR spectroscopy using 3 Tesla to investigate the metabolic profiles of joint fluids in different types of knee diseases
The objective of this study, therefore, was to assess the ability of proton MRS to identify the apparent heterogeneous characteristics of metabolic spectra in the joint fluid regions in human knees using a high-field MRI system. Eighty-four patients with effusion lesions who were referred for routine knee MR imaging underwent proton MRS with point-resolved, single-voxel MR spectroscopy using a clinical 3.0 Tesla MRI system. Thirty-eight patients were confirmed to have the following: degenerative osteoarthritis, 21 patients (Group 1); traumatic diseases, 12 patients (Group 2); infectious diseases, 4 patients and an inflamma...
Source: Journal of Applied Clinical Medical Physics - March 8, 2016 Category: Physics Source Type: research

Evaluation of the ΔV 4D CT ventilation calculation method using in vivo xenon CT ventilation data and comparison to other methods
In conclusion, ventilation distributions generated using ΔV-4D CT and deformable image registration are in reasonably agreement with the in vivo XeCT measured ventilation distribution. (Source: Journal of Applied Clinical Medical Physics)
Source: Journal of Applied Clinical Medical Physics - March 8, 2016 Category: Physics Source Type: research

Quantitative outcome of registration methods for correcting cardiac drift in cardiac PET/CT imaging
This study evaluates three postimaging registration techniques to correct PET/CT misalignment by altering the transmission map to match myo­cardial uptake. Simulated misalignment studies were performed with a cardiac torso phantom filled with [18F]FDG at 10:1 myocardium/background. An air-filled saline bag affixed to the medial left lung surface served as a distensible lung. An initial CT acquisition was followed by successive PET acquisitions consisting of small displacements of the cardiac insert into the left lung. Phantom transmission scans were aligned to the myocardial uptake in the emission scans by applying 1) ...
Source: Journal of Applied Clinical Medical Physics - March 8, 2016 Category: Physics Source Type: research

Asymmetric breast dose in coronary angiography
The purpose of this study was to demonstrate asymmetric radiation dose distribution to the breasts in coronary angiography. Gafchromic XR-QA2 film was used as an area dosimeter to capture the asymmetric dose distribution to the breasts at vari­ous tissue depths in an anthropomorphic phantom. A selection of tube angulations were used under a controlled experiment and during a mock coronary angiography procedure. The Gafchromic XR-QA2 film was able to confirm the asymmetric distribution of radiation dose to the breast and provide a normalized breast dose value. The right breast received the majority of dose for most of t...
Source: Journal of Applied Clinical Medical Physics - March 8, 2016 Category: Physics Source Type: research

Performance evaluation of iterative reconstruction algorithms for achieving CT radiation dose reduction — a phantom study
The purpose of this study was to characterize image quality and dose performance with GE CT iterative reconstruction techniques, adaptive statistical iterative recon­struction (ASiR), and model-based iterative reconstruction (MBIR), over a range of typical to low-dose intervals using the Catphan 600 and the anthropomorphic Kyoto Kagaku abdomen phantoms. The scope of the project was to quantitatively describe the advantages and limitations of these approaches. The Catphan 600 phantom, supplemented with a fat-equivalent oval ring, was scanned using a GE Discovery HD750 scanner at 120 kVp, 0.8 s rotation time, and pitch f...
Source: Journal of Applied Clinical Medical Physics - March 8, 2016 Category: Physics Source Type: research

Development and evaluation of an end-to-end test for head and neck IMRT with a novel multiple-dosimetric modality phantom
A comprehensive end-to-end test for head and neck IMRT treatments was developed using a custom phantom designed to utilize multiple dosimetry devices. Initial end-to-end test and custom H&N phantom were designed to yield maximum informa­tion in anatomical regions significant to H&N plans with respect to: (i) geometric accuracy, (ii) dosimetric accuracy, and (iii) treatment reproducibility. The phantom was designed in collaboration with Integrated Medical Technologies. The phantom was imaged on a CT simulator and the CT was reconstructed with 1 mm slice thick­ness and imported into Varian’s Eclipse tre...
Source: Journal of Applied Clinical Medical Physics - March 8, 2016 Category: Physics Source Type: research

Inter- and intrafractional dose uncertainty in hypofractionated Gamma Knife radiosurgery
The purpose of this study is to evaluate inter- and intrafractional dose variations resulting from head position deviations for patients treated with the Extend relo­catable frame system utilized in hypofractionated Gamma Knife radiosurgery (GKRS). While previous reports characterized the residual setup and intrafraction uncertainties of the system, the dosimetric consequences have not been investigated. A digital gauge was used to measure the head position of 16 consecutive Extend patients (62 fractions) at the time of simulation, before each fraction, and imme­diately following each fraction. Vector interfraction...
Source: Journal of Applied Clinical Medical Physics - March 8, 2016 Category: Physics Source Type: research

Simultaneous MV-kV imaging for intrafractional motion management during volumetric-modulated arc therapy delivery*
The purpose of this study was to evaluate the accuracy and clinical feasibility of a motion monitoring method employing simultaneously acquired MV and kV images during volumetric-modulated arc therapy (VMAT). Short-arc digital tomosynthesis (SA-DTS) is used to improve the quality of the MV images that are then combined with orthogonally acquired kV images to assess 3D motion. An anthropomorphic phantom with implanted gold seeds was used to assess accuracy of the method under static, typical prostatic, and respiratory motion scenarios. Automatic registra­tion of kV images and single MV frames or MV SA-DTS reconstructed ...
Source: Journal of Applied Clinical Medical Physics - March 8, 2016 Category: Physics Source Type: research

Evaluation of interfractional variation of the centroid position and volume of internal target volume during stereotactic body radiotherapy of lung cancer using cone-beam computed tomography
The purpose of this study was to determine interfractional variation of the centroid position and volume of internal target volume (ITV) during stereotactic body radiation therapy (SBRT) of lung cancer. From January 2014 to August 2014, a total of 32 patients with 37 primary or metastatic lung tumors were enrolled in our study. All patients received SBRT treatment in 4–5 fractions to a median dose of 48 Gy. Both 3D CT and 4D CT scans were used for radiotherapy treatment planning. 3D CBCT was acquired prior to treatment delivery to verify patient positioning. A total of 163 3D CBCT images were available for evaluation...
Source: Journal of Applied Clinical Medical Physics - March 8, 2016 Category: Physics Source Type: research

A comparative study of automatic image segmentation algorithms for target tracking in MR-IGRT
On-board magnetic resonance (MR) image guidance during radiation therapy offers the potential for more accurate treatment delivery. To utilize the real-time image information, a crucial prerequisite is the ability to successfully segment and track regions of interest (ROI). The purpose of this work is to evaluate the performance of different segmentation algorithms using motion images (4 frames per second) acquired using a MR image-guided radiotherapy (MR-IGRT) system. Manual con­tours of the kidney, bladder, duodenum, and a liver tumor by an experienced radia­tion oncologist were used as the ground truth for perfo...
Source: Journal of Applied Clinical Medical Physics - March 8, 2016 Category: Physics Source Type: research

Quantitative assessment of anatomical change using a virtual proton depth radiograph for adaptive head and neck proton therapy
The aim of this work is to demonstrate the feasibility of using water-equivalent thickness (WET) and virtual proton depth radiographs (PDRs) of intensity corrected cone-beam computed tomography (CBCT) to detect anatomical change and patient setup error to trigger adaptive head and neck proton therapy. The planning CT (pCT) and linear accelerator (linac) equipped CBCTs acquired weekly during treatment of a head and neck patient were used in this study. Deformable image registration (DIR) was used to register each CBCT with the pCT and map Hounsfield units (HUs) from the planning CT (pCT) onto the daily CBCT. The deformed pC...
Source: Journal of Applied Clinical Medical Physics - March 8, 2016 Category: Physics Source Type: research

Commissioning of a 3D image-based treatment planning system for high-dose-rate brachytherapy of cervical cancer
The objective of this work is to present commissioning procedures to clinically implement a three-dimensional (3D), image-based, treatment-planning system (TPS) for high-dose-rate (HDR) brachytherapy (BT) for gynecological (GYN) cancer. The physical dimensions of the GYN applicators and their values in the virtual applicator library were varied by 0.4 mm of their nominal values. Reconstruction uncertainties of the titanium tandem and ovoids (T&O) were less than 0.4 mm on CT phantom studies and on average between 0.8–1.0 mm on MRI when compared with X-rays. In-house software, HDRCalculator, was developed to check ...
Source: Journal of Applied Clinical Medical Physics - March 8, 2016 Category: Physics Source Type: research

Evaluation of the range shifter model for proton pencil-beam scanning for the Eclipse v.11 treatment planning system
Existing proton therapy pencil-beam scanning (PBS) systems have limitations on the minimum range to which a patient can be treated. This limitation arises from practical considerations, such as beam current intensity, layer spacing, and delivery time. The range shifter (RS) — a slab of stopping material inserted between the nozzle and the patient — is used to reduce the residual range of the incident beam so that the treatment ranges can be extended to shallow depths. Accurate modeling of the RS allows one to calculate the beam spot size entering the patient, given the proton energy, for arbitrary positions and...
Source: Journal of Applied Clinical Medical Physics - March 8, 2016 Category: Physics Source Type: research

Comparison of TG-43 dosimetric parameters of brachytherapy sources obtained by three different versions of MCNP codes
Monte Carlo simulations are widely used for calculation of the dosimetric param­eters of brachytherapy sources. MCNP4C2, MCNP5, MCNPX, EGS4, EGSnrc, PTRAN, and GEANT4 are among the most commonly used codes in this field. Each of these codes utilizes a cross-sectional library for the purpose of simulat­ing different elements and materials with complex chemical compositions. The accuracies of the final outcomes of these simulations are very sensitive to the accuracies of the cross-sectional libraries. Several investigators have shown that inaccuracies of some of the cross section files have led to errors in 125I and ...
Source: Journal of Applied Clinical Medical Physics - March 8, 2016 Category: Physics Source Type: research

Perturbation of water-equivalent thickness as a surrogate for respiratory motion in proton therapy
Respiratory motion is traditionally assessed using tumor motion magnitude. In proton therapy, respiratory motion causes density variations along the beam path that result in uncertainties of proton range. This work has investigated the use of water-equivalent thickness (WET) to quantitatively assess the effects of respiratory motion on calculated dose in passively scattered proton therapy (PSPT). A cohort of 29 locally advanced non-small cell lung cancer patients treated with 87 PSPT treatment fields were selected for analysis. The variation in WET (ΔWET) along each field was calculated between exhale and inhale phas...
Source: Journal of Applied Clinical Medical Physics - March 8, 2016 Category: Physics Source Type: research

Assessment of radiobiological metrics applied to patient-specific QA process of VMAT prostate treatments
VMAT is a powerful technique to deliver hypofractionated prostate treatments. The lack of correlations between usual 2D pretreatment QA results and the clini­cal impact of possible mistakes has allowed the development of 3D verification systems. Dose determination on patient anatomy has provided clinical predictive capability to patient-specific QA process. Dose-volume metrics, as evaluation crite­ria, should be replaced or complemented by radiobiological indices. These metrics can be incorporated into individualized QA extracting the information for response parameters (gEUD, TCP, NTCP) from DVHs. The aim of this ...
Source: Journal of Applied Clinical Medical Physics - March 8, 2016 Category: Physics Source Type: research

Performance variations among clinically available deformable image registration tools in adaptive radiotherapy — how should we evaluate and interpret the result?
The purpose of this study is to evaluate the performance variations in commercial deformable image registration (DIR) tools for adaptive radiation therapy and further to interpret the differences using clinically available terms. Three clinical examples (prostate, head and neck (HN), and cranial spinal irradiation (CSI) with L-spine boost) were evaluated in this study. Firstly, computerized deformed CT images were generated using simulation QA software with virtual deformations of bladder filling (prostate), neck flexion/bite-block repositioning/tumor shrinkage (HN), and vertebral body rotation (CSI). The corresponding tra...
Source: Journal of Applied Clinical Medical Physics - March 8, 2016 Category: Physics Source Type: research

Application of dose kernel calculation using a simplified Monte Carlo method to treatment plan for scanned proton beams
Full Monte Carlo (FMC) calculation of dose distribution has been recognized to have superior accuracy, compared with the pencil beam algorithm (PBA). However, since the FMC methods require long calculation time, it is difficult to apply them to routine treatment planning at present. In order to improve the situation, a simplified Monte Carlo (SMC) method has been introduced to the dose kernel calculation applicable to dose optimization procedure for the proton pencil beam scanning. We have evaluated accuracy of the SMC calculation by comparing a result of the dose kernel calculation using the SMC method with that using the...
Source: Journal of Applied Clinical Medical Physics - March 8, 2016 Category: Physics Source Type: research

Diamond detector in absorbed dose measurements in high-energy linear accelerator photon and electron beams
Diamond detectors (DD) are preferred in small field dosimetry of radiation beams because of small dose profile penumbras, better spatial resolution, and tissue-equivalent properties. We investigated a commercially available ‘microdiamond’ detector in realizing absorbed dose from first principles. A microdiamond detector, type TM 60019 with tandem electrometer is used to measure absorbed doses in water, nylon, and PMMA phantoms. With sensitive volume 0.004 mm3, radius 1.1mm, thickness 1 x10-3 mm, the nominal response is 1 nC/Gy. It is assumed that the dia­mond detector could collect total electric charge (nC...
Source: Journal of Applied Clinical Medical Physics - March 8, 2016 Category: Physics Source Type: research

Assessment of image quality and dose calculation accuracy on kV CBCT, MV CBCT, and MV CT images for urgent palliative radiotherapy treatments
A clinical workflow was developed for urgent palliative radiotherapy treatments that integrates patient simulation, planning, quality assurance, and treatment in one 30-minute session. This has been successfully tested and implemented clinically on a linac with MV CBCT capabilities. To make this approach available to all clin­ics equipped with common imaging systems, dose calculation accuracy based on treatment sites was assessed for other imaging units. We evaluated the feasibility of palliative treatment planning using on-board imaging with respect to image qual­ity and technical challenges. The purpose was to te...
Source: Journal of Applied Clinical Medical Physics - March 8, 2016 Category: Physics Source Type: research

A novel method for radiotherapy patient identification using surface imaging
Performing a procedure on the wrong patient or site is one of the greatest errors that can occur in medicine. The addition of automation has been shown to reduce errors in many processes. In this work we explore the use of an automated patient identification process using optical surface imaging for radiotherapy treatments. Surface imaging uses visible light to align the patient to a reference surface in the treatment room. It is possible to evaluate the similarity between a daily set-up surface image and the reference image using distance to agreement between the points on the two surfaces. The higher the percentage overl...
Source: Journal of Applied Clinical Medical Physics - March 8, 2016 Category: Physics Source Type: research

Monte Carlo evaluation of tissue heterogeneities corrections in the treatment of head and neck cancer patients using stereotactic radiotherapy
This study includes 10 head and neck cancer patients who underwent SRT re-irradiation using heterogene­ity corrected pencil-beam (PB-hete) algorithm for dose calculation. Prescription dose was 24–40 Gy in 3–5 fractions (treated 3–5 fractions per week) with at least 95% of the PTV volume receiving 100% of the prescription dose. A stereotactic head and neck localization box was attached to the base of the thermoplastic mask fixation for target localization. The gross tumor volume (GTV) and organs-at-risk (OARs) were contoured on the 3D CT images. The planning target volume (PTV) was generated from the G...
Source: Journal of Applied Clinical Medical Physics - March 8, 2016 Category: Physics Source Type: research

Electron beam energy QA — a note on measurement tolerances
Monthly QA is recommended to verify the constancy of high-energy electron beams generated for clinical use by linear accelerators. The tolerances are defined as 2%/2 mm in beam penetration according to AAPM task group report 142. The practical implementation is typically achieved by measuring the ratio of readings at two different depths, preferably near the depth of maximum dose and at the depth corresponding to half the dose maximum. Based on beam commissioning data, we show that the relationship between the ranges of energy ratios for different electron energies is highly nonlinear. We provide a formalism that translate...
Source: Journal of Applied Clinical Medical Physics - March 8, 2016 Category: Physics Source Type: research

Varian HDR surface applicators — commissioning and clinical implementation
The purpose of this study was to validate the dosimetric performance of Varian surface applicators with the source vertically positioned and develop procedures for clinical implementation. The Varian surface applicators with the source verti­cally positioned provide a wide range of apertures making them clinically advanta­geous, though the steep dose gradient in the region of 3–4 mm prescription depth presents multiple challenges. The following commissioning tests were performed: 1) verification of functional integrity and physical dimensions; and 2) dosimetric measurements to validate data provided by Varian...
Source: Journal of Applied Clinical Medical Physics - March 8, 2016 Category: Physics Source Type: research

Time-resolved beam symmetry measurement for VMAT commissioning and quality assurance
This study aims to test this assump­tion and present a method of measuring time-resolved beam symmetry measure­ment during a VMAT delivery that includes extreme variations of dose rate and gantry speed. The Sun Nuclear IC Profiler in gantry mount was used to measure time-resolved in-plane and cross-plane profiles during plan delivery from which symmetry could be determined. Time-resolved symmetry measurements were performed throughout static field exposures at cardinal gantry angles, conformal arcs with constant dose rate and gantry speed, and during a VMAT test plan with gantry speed and dose rate modulation. Meas...
Source: Journal of Applied Clinical Medical Physics - March 8, 2016 Category: Physics Source Type: research

Is grid therapy useful for all tumors and every grid block design?
Grid therapy is a treatment technique that has been introduced for patients with advanced bulky tumors. The purpose of this study is to investigate the effect of the radia­tion sensitivity of the tumors and the design of the grid blocks on the clinical response of grid therapy. The Monte Carlo simulation technique is used to determine the dose distribution through a grid block that was used for a Varian 2100C linear accelerator. From the simulated dose profiles, the therapeutic ratio (TR) and the equivalent uniform dose (EUD) for different types of tumors with respect to their radiation sensitivities were calculated. T...
Source: Journal of Applied Clinical Medical Physics - March 8, 2016 Category: Physics Source Type: research

Gafchromic film dosimetry of a new HDR 192Ir brachytherapy source
High-dose-rate (HDR) brachytherapy is a popular modality for treating cancers of the prostate, cervix, endometrium, breast, skin, bronchus, esophagus, and head and neck as well as soft-tissue sarcomas. Because of different source designs and licensing issues, there is a need for specific dosimetry dataset for each HDR source model. The main objective of the present work is to measure 2D relative dose distribution around a new prototype 192Ir source, referred to as IRAsource-HDR, in PMMA phantom in the framework of AAPM TG-43 and TG-55 recommendations for radial distances of 0.5cm to 4 cm. Radiochromic films (RCFs) Gafchrom...
Source: Journal of Applied Clinical Medical Physics - March 8, 2016 Category: Physics Source Type: research

A software tool of digital tomosynthesis application for patient positioning in radiotherapy
Digital Tomosynthesis (DTS) is an image modality in reconstructing tomographic images from two-dimensional kV projections covering a narrow scan angles. Comparing with conventional cone-beam CT (CBCT), it requires less time and radiation dose in data acquisition. It is feasible to apply this technique in patient positioning in radiotherapy. To facilitate its clinical application, a software tool was developed and the reconstruction processes were accelerated by graphic process­ing unit (GPU). Two reconstruction and two registration processes are required for DTS application which is different from conventional CBCT app...
Source: Journal of Applied Clinical Medical Physics - March 8, 2016 Category: Physics Source Type: research

The MapCHECK Measurement Uncertainty function and its effect on planar dose pass rates
Our study aimed to quantify the effect of the Measurement Uncertainty function on planar dosimetry pass rates, as measured and analyzed with the Sun Nuclear Corporation MapCHECK 2 array and its associated software. This optional func­tion is toggled in the program preferences of the software (though turned on by default upon installation), and automatically increases the dose difference toler­ance defined by the user for each planar dose comparison. Dose planes from 109 static-gantry IMRT fields and 40 VMAT arcs, of varying modulation complexity, were measured at 5 cm water-equivalent depth in the MapCHECK 2 diode ...
Source: Journal of Applied Clinical Medical Physics - March 8, 2016 Category: Physics Source Type: research

Implementation of full/half bowtie filter models in a commercial treatment planning system for kilovoltage cone-beam CT dose estimations
This study demonstrated that the established full/half bowtie filter beam models can produce reasonable dose calculation results. Further study is to be performed to evaluate the models in clinical situations. (Source: Journal of Applied Clinical Medical Physics)
Source: Journal of Applied Clinical Medical Physics - March 8, 2016 Category: Physics Source Type: research

Assessment of national dosimetry quality audits results for teletherapy machines from 1989 to 2015
The purpose of this study was to ensure accuracy in radiation dose delivery, external dosimetry quality audit has an equal importance with routine dosimetry performed at clinics. To do so, dosimetry quality audit was organized by the Secondary Standard Dosimetry Laboratory (SSDL) of Pakistan Institute of Nuclear Science and Technology (PINSTECH) at the national level to investigate and minimize uncertainties involved in the measurement of absorbed dose, and to improve the accuracy of dose measurement at different radiotherapy hospitals. A total of 181 dosimetry quality audits (i.e., 102 of Co-60 and 79 of linear accelerato...
Source: Journal of Applied Clinical Medical Physics - March 8, 2016 Category: Physics Source Type: research

A pilot study of volumetric-modulated arc therapy for malignant pleural mesothelioma
Malignant pleural mesothelioma (MPM) is an extremely difficult disease to treat. This pilot study investigates the feasibility of using volumetric-modulated arc ther­apy (VMAT) for malignant pleural mesothelioma (MPM), and compares VMAT to static field intensity-modulated radiotherapy (IMRT) for five patients. To identify the best treatment technique for MPM, in five patients, we made a representative comparative analysis of two kinds of techniques for radiation therapy planning: IMRT and VMAT. The plans were created for an Elekta Synergy linear accelerator with 6 MV photons using Oncentra version 4.3 treatment plannin...
Source: Journal of Applied Clinical Medical Physics - March 8, 2016 Category: Physics Source Type: research

Translating bed total body irradiation lung shielding and dose optimization using asymmetric MLC apertures
We present a dosimetric comparison of this technique with a previously developed symmetric MLC-based TBI technique. An anthropomor­phic RANDO phantom is CT scanned with 3 mm slice thickness. Radiological depths (RD) are calculated on individual CT slices along the divergent ray lines. Asymmetric MLC apertures are defined every 9 mm over the phantom length in the craniocaudal direction. Individual asymmetric MLC leaf positions are optimized based on RD values of all slices for uniform dose distributions. Dose calculations are performed in the Eclipse treatment planning system over these optimized MLC apertures. Dose uni...
Source: Journal of Applied Clinical Medical Physics - March 8, 2016 Category: Physics Source Type: research

A design of a DICOM-RT-based tool box for nonrigid 4D dose calculation
The study was aimed to introduce a design of a DICOM-RT-based tool box to facilitate 4D dose calculation based on deformable voxel-dose registration. The computational structure and the calculation algorithm of the tool box were explicitly discussed in the study. The tool box was written in MATLAB in conjunction with CERR. It consists of five main functions which allow a) importation of DICOM-RT-based 3D dose plan, b) deformable image registration, c) tracking voxel doses along breathing cycle, d) presentation of temporal dose distribution at different time phase, and e) derivation of 4D dose. The efficacy of using the too...
Source: Journal of Applied Clinical Medical Physics - March 8, 2016 Category: Physics Source Type: research

Beam perturbation characteristics of a 2D transmission silicon diode array, Magic Plate
The main objective of this study is to demonstrate the performance characteristics of the Magic Plate (MP) system when operated upstream of the patient in trans­mission mode (MPTM). The MPTM is an essential component of a real-time QA system designed for operation during radiotherapy treatment. Of particular interest is a quantitative study into the influence of the MP on the radiation beam quality at several field sizes and linear accelerator potential differences. The impact is measured through beam perturbation effects such as changes in the skin dose and/or percentage depth dose (PDD) (both in and out of field). Th...
Source: Journal of Applied Clinical Medical Physics - March 8, 2016 Category: Physics Source Type: research

Evaluation of tracking accuracy of the CyberKnife system using a webcam and printed calibrated grid
Tracking accuracy for the CyberKnife’s Synchrony system is commonly evaluated using a film-based verification method. We have evaluated a verification system that uses a webcam and a printed calibrated grid to verify tracking accuracy over three different motion patterns. A box with an attached printed calibrated grid and four fiducial markers was attached to the motion phantom. A target marker was positioned at the grid’s center. The box was set up using the other three markers. Target tracking accuracy was evaluated under three conditions: 1) stationary; 2) sinusoidal motion with different amplitudes of 5, 10...
Source: Journal of Applied Clinical Medical Physics - March 8, 2016 Category: Physics Source Type: research

Going the distance: validation of Acuros and AAA at an extended SSD of 400 cm
Accurate dose calculation and treatment delivery is essential for total body irradia­tion (TBI). In an effort to verify the accuracy of TBI dose calculation at our institu­tion, we evaluated both the Varian Eclipse AAA and Acuros algorithms to predict dose distributions at an extended source-to-surface distance (SSD) of 400 cm. Measurements were compared to calculated values for a 6 MV beam in physical and virtual phantoms at 400 cm SSD using open beams for both 5 × 5 and 40 × 40cm2 field sizes. Inline and crossline profiles were acquired at equivalent depths of 5 cm, 10 cm, and 20 cm. Depth-dose curves...
Source: Journal of Applied Clinical Medical Physics - March 8, 2016 Category: Physics Source Type: research

Methods to model and predict the ViewRay treatment deliveries to aid patient scheduling and treatment planning
A software tool is developed, given a new treatment plan, to predict treatment delivery time for radiation therapy (RT) treatments of patients on ViewRay magnetic resonance image-guided radiation therapy (MR-IGRT) delivery system. This tool is necessary for managing patient treatment scheduling in our clinic. The predicted treatment delivery time and the assessment of plan complexities could also be useful to aid treatment planning. A patient’s total treatment delivery time, not including time required for localization, is modeled as the sum of four components: 1) the treatment initialization time; 2) the total beam-...
Source: Journal of Applied Clinical Medical Physics - March 8, 2016 Category: Physics Source Type: research

The suitability of common metrics for assessing parotid and larynx autosegmentation accuracy
This study investigated whether geometric accuracy (as quantified by several commonly used metrics) was associated with dosimetric differences for the parotid and larynx, comparing automatically generated contours against manually drawn ground truth contours. This enabled the suitability of different commonly used metrics to be assessed for measuring automatic segmentation accuracy of the parotid and larynx. Parotid and larynx structures for 10 head and neck patients were outlined by five clinicians to create ground truth structures. An automatic segmentation algorithm was used to create automatically generated normal stru...
Source: Journal of Applied Clinical Medical Physics - March 8, 2016 Category: Physics Source Type: research

Commissioning and initial experience with the first clinical gantry-mounted proton therapy system
We present our commissioning process and initial clinical experience, including i) CT calibration; ii) beam data acquisition and machine characteristics; iii) dosimetric commissioning of the treatment planning system; iv) validation through the Imaging and Radiation Oncology Core credentialing process, includ­ing irradiations on the spine, prostate, brain, and lung phantoms; v) evaluation of localization accuracy of the image guidance system; and vi) initial clinical experi­ence. Clinically, the system operates well and has provided an excellent platform for the treatment of diseases with protons. (Source: Journal ...
Source: Journal of Applied Clinical Medical Physics - March 8, 2016 Category: Physics Source Type: research

Evaluation of MLC leaf positioning accuracy for static and dynamic IMRT treatments using DAVID in vivo dosimetric system*
This study aimed to inves­tigate the accuracy and repeatability of the MLC leaf positioning via the DAVID invivo dosimetric system for dynamic and static MLC systems. The DAVID system was designed as multiwire transmission ionization chamber which is placed in accessory holder of linear accelerators. Each wire of DAVID system corresponds to a MLC leaf-pair to verify the leaf positioning accuracy during IMRT treatment and QA. In this study, verifications of IMRT plans of five head and neck (H&N) and five prostate patients treated in a Varian DHX linear accelerator with 80-leaf MLC were performed using DAVID system. ...
Source: Journal of Applied Clinical Medical Physics - March 8, 2016 Category: Physics Source Type: research

Dose calculation for hypofractionated volumetric-modulated arc therapy: approximating continuous arc delivery and tongue-and-groove modeling*
This study explores methods to minimize the differences between in-house dose calculation and actual delivery of hypofractionated volumetric-modulated arc therapy (VMAT), by focusing on arc approximation and tongue-and-groove (TG) modeling. For dose calculation, the continuous delivery arc is typically approximated by a series of static beams with an angular spacing of 2°. This causes significant error when there is large MLC movement from one beam to the next. While increasing the number of beams will minimize the dose error, calculation time will increase significantly. We propose a solution by inserting two addition...
Source: Journal of Applied Clinical Medical Physics - March 8, 2016 Category: Physics Source Type: research

A neural network-based 2D/3D image registration quality evaluator for pediatric patient setup in external beam radiotherapy.
Abstract Our purpose was to develop a neural network-based registration quality evaluator (RQE) that can improve the 2D/3D image registration robustness for pediatric patient setup in external beam radiotherapy. Orthogonal daily setup X-ray images of six pediatric patients with brain tumors receiving proton therapy treatments were retrospectively registered with their treatment planning computed tomography (CT) images. A neural network-based pattern classifier was used to determine whether a registration solution was successful based on geometric features of the similarity measure values near the point-of-solution...
Source: Journal of Applied Clinical Medical Physics - February 20, 2016 Category: Physics Authors: Wu J, Su Z, Li Z Tags: J Appl Clin Med Phys Source Type: research

On the sensitivity of TG-119 and IROC credentialing to TPS commissioning errors.
Abstract We investigate the sensitivity of IMRT commissioning using the TG-119 C-shape phantom and credentialing with the IROC head and neck phantom to treatment planning system commissioning errors. We introduced errors into the various aspects of the commissioning process for a 6X photon energy modeled using the analytical anisotropic algorithm within a commercial treatment planning system. Errors were implemented into the various components of the dose calculation algorithm including primary photons, secondary photons, electron contamination, and MLC parameters. For each error we evaluated the probability that ...
Source: Journal of Applied Clinical Medical Physics - February 20, 2016 Category: Physics Authors: McVicker D, Yin FF, Adamson JD Tags: J Appl Clin Med Phys Source Type: research

A new method and device of aligning patient setup lasers in radiation therapy.
In this study, a new laser align-ment method was devised and evaluated successfully. The new method provided more accurate, more reproducible, and faster alignment of the lasers than the conventional method. PMID: 26894331 [PubMed - as supplied by publisher] (Source: Journal of Applied Clinical Medical Physics)
Source: Journal of Applied Clinical Medical Physics - February 20, 2016 Category: Physics Authors: Hwang UJ, Jo K, Lim YK, Kwak JW, Choi SH, Jeong C, Kim MY, Jeong JH, Shin D, Lee SB, Park JH, Park SY, Kim S Tags: J Appl Clin Med Phys Source Type: research