Assessment of Monte Carlo algorithm for compliance with RTOG 0915 dosimetric criteria in peripheral lung cancer patients treated with stereotactic body radiotherapy.
This study evaluated 20 Stage I-II NSCLC patients with peripherally located lung tumors, who underwent MC-based SBRT with heterogeneity correction using X-ray Voxel Monte Carlo (XVMC) algorithm (Brainlab iPlan version 4.1.2). Total dose of 50 to 54 Gy in 3 to 5 fractions was delivered to the planning target vol-ume (PTV) with at least 95% of the PTV receiving 100% of the prescription dose (V100% ≥ 95%). The internal target volume (ITV) was delineated on maximum intensity projection (MIP) images of 4D CT scans. The PTV included the ITV plus 5 mm uniform margin applied to the ITV. The PTV ranged from 11.1 to 163.0 cc (mea...
Source: Journal of Applied Clinical Medical Physics - May 15, 2016 Category: Physics Authors: Pokhrel D, Sood S, Badkul R, Jiang H, McClinton C, Lominska C, Kumar P, Wang F Tags: J Appl Clin Med Phys Source Type: research

Comparison of manual and automatic MR-CT registration for radiotherapy of prostate cancer.
ard L Abstract In image-guided radiotherapy (IGRT) of prostate cancer, delineation of the clini-cal target volume (CTV) often relies on magnetic resonance (MR) because of its good soft-tissue visualization. Registration of MR and computed tomography (CT) is required in order to add this accurate delineation to the dose planning CT. An automatic approach for local MR-CT registration of the prostate has previously been developed using a voxel property-based registration as an alternative to a manual landmark-based registration. The aim of this study is to compare the two registration approaches and to investigate th...
Source: Journal of Applied Clinical Medical Physics - May 15, 2016 Category: Physics Authors: Korsager AS, Carl J, Riis Østergaard L Tags: J Appl Clin Med Phys Source Type: research

Quantification of the margin required for treating intraprostatic lesions.
Abstract Advances in magnetic resonance imaging (MRI) sequences allow physicians to define the dominant intraprostatic lesion (IPL) in prostate radiation therapy treat-ments allowing for dose escalation and potentially increased tumor control. This work quantifies the margin required around the MRI-defined IPL accounting for both prostate motion and deformation. Ten patients treated with a simultaneous integrated intraprostatic boost (SIIB) were retrospectively selected and replanned with incremental 1 mm margins from 0-5 mm around the IPL to determine if there were any significant differences in dosimetric parame...
Source: Journal of Applied Clinical Medical Physics - May 15, 2016 Category: Physics Authors: Studenski MT, Valenciaga Y, Abramowitz MC, Stoyanova R, Bossart E, Dogan N, Pollack A Tags: J Appl Clin Med Phys Source Type: research

Effect of fluoroscopic X-ray beam spectrum on air-kerma measurement accuracy: implications for establishing correction coefficients on interventional fluoroscopes with KAP meters.
Abstract The first goal of this study was to investigate the accuracy of the displayed reference plane air kerma (Ka,r) or air kerma-area product (Pk,a) over a broad spectrum of X-ray beam qualities on clinically used interventional fluoroscopes incorporating air kerma-area product meters (KAP meters) to measure X-ray output. The second goal was to investigate the accuracy of a correction coefficient (CC) determined at a single beam quality and applied to the measured Ka,r over a broad spectrum of beam qualities. Eleven state-of-the-art interventional fluoroscopes were evaluated, consisting of eight Siemens Artis ...
Source: Journal of Applied Clinical Medical Physics - May 15, 2016 Category: Physics Authors: Wunderle KA, Rakowski JT, Dong FF Tags: J Appl Clin Med Phys Source Type: research

Addendum to brachytherapy dose-volume histogram commissioning with multiple planning systems.
Abstract The process for validating dose-volume histogram data in brachytherapy software is presented as a supplement to a previously published article. Included is the DVH accuracy evaluation of the Best NOMOS treatment planning system called "Best TPS VolumePlan." As done previously in other software, a rectangular cuboid was contoured in the treatment planning system. A single radioactive 125I source was positioned coplanar and concentric with one end. Calculations were performed to estimate dose deposition in partial volumes of the cuboid structure, using the brachytherapy dosimetry formalism defined...
Source: Journal of Applied Clinical Medical Physics - May 15, 2016 Category: Physics Authors: Gossman MS Tags: J Appl Clin Med Phys Source Type: research

Deformable image registration and interobserver variation in contour propagation for radiation therapy planning.
Abstract Deformable image registration (DIR) and interobserver variation inevitably intro-duce uncertainty into the treatment planning process. The purpose of the current work was to measure deformable image registration (DIR) errors and interobserver variability for regions of interest (ROIs) in the head and neck and pelvic regions. Measured uncertainties were combined to examine planning margin adequacy for contours propagated for adaptive therapy and to assess the trade-off of DIR and interobserver uncertainty in atlas-based automatic segmentation. Two experi-enced dosimetrists retrospectively contoured brainst...
Source: Journal of Applied Clinical Medical Physics - May 15, 2016 Category: Physics Authors: Riegel AC, Antone JG, Zhang H, Jain P, Raince J, Rea A, Bergamo AM, Kapur A, Potters L Tags: J Appl Clin Med Phys Source Type: research

Effect of electron contamination on in vivo dosimetry for lung block shielding during TBI.
Abstract Our institution performs in vivo verification measurement for each of our total body irradiation (TBI) patients with optically stimulated luminescent dosimeters (OSLD). The lung block verification measurements were commonly higher than expected. The aim of this work is to understand this discrepancy and improve the accuracy of these lung block verification measurements. Initially, the thickness of the lung block was increased to provide adequate lung sparing. Further tests revealed the increase was due to electron contamination dose emanating from the lung block. The thickness of the bolus material coveri...
Source: Journal of Applied Clinical Medical Physics - May 15, 2016 Category: Physics Authors: Narayanasamy G, Cruz W, Saenz DL, Stathakis S, Papanikolaou N, Kirby N Tags: J Appl Clin Med Phys Source Type: research

Inverse treatment planning for spinal robotic radiosurgery: an international multi-institutional benchmark trial.
rd A Abstract Stereotactic radiosurgery (SRS) is the accurate, conformal delivery of high-dose radiation to well-defined targets while minimizing normal structure doses via steep dose gradients. While inverse treatment planning (ITP) with computerized optimization algorithms are routine, many aspects of the planning process remain user-dependent. We performed an international, multi-institutional benchmark trial to study planning variability and to analyze preferable ITP practice for spinal robotic radiosurgery. 10 SRS treatment plans were generated for a complex-shaped spinal metastasis with 21 Gy in 3 fractions ...
Source: Journal of Applied Clinical Medical Physics - May 15, 2016 Category: Physics Authors: Blanck O, Wang L, Baus W, Grimm J, Lacornerie T, Nilsson J, Luchkovskyi S, Palazon Cano I, Shou Z, Ayadi M, Treuer H, Viard R, Siebert FA, Chan MK, Hildebrandt G, Dunst J, Imhoff D, Wurster S, Wolff R, Romanelli P, Lartigau E, Semrau R, Soltys SG, Schweik Tags: J Appl Clin Med Phys Source Type: research

Initial evaluation of automated treatment planning software.
We report on the initial evaluation of this algorithm on 10 challenging cases of locoreginally advanced head and neck cancer. All patients were treated with VMAT to 70 Gy to the gross disease and 56 Gy to the elective bilateral nodes. The results of post-treatment autoplanning (AP) were compared to the original human-driven plans (HDP). We used an objective scoring system based on defining a collection of specific dosimetric metrics and corresponding numeric score functions for each. Five AP techniques with different input dose goals were applied to all patients. The best of them averaged the composite score 8% lower than ...
Source: Journal of Applied Clinical Medical Physics - May 15, 2016 Category: Physics Authors: Gintz D, Latifi K, Caudell J, Nelms B, Zhang G, Moros E, Feygelman V Tags: J Appl Clin Med Phys Source Type: research

Dosimetric properties of equivalent-quality flattening filter-free (FFF) and flattened photon beams of Versa HD linear accelerator.
This study presents the basic dosimetric properties of photon beams of a Versa HD linear accelerator (linac), which is capable of delivering flattening filter-free (FFF) beams with a beam quality equivalent to the corresponding flattened beams based on comprehensive beam data measurement. The analyzed data included the PDDs, profiles, penumbra, out-of-field doses, surface doses, output factors, head and phantom scatter factors, and MLC transmissions for both FFF and flattened beams of 6 MV and 10 MV energy from an Elekta Versa HD linac. The 6MVFFF and 10MVFFF beams had an equivalent mean energy to the flattened beams and s...
Source: Journal of Applied Clinical Medical Physics - May 15, 2016 Category: Physics Authors: Meshram MN, Pramanik S, Ranjith CP, Gopal SK, Dobhal R Tags: J Appl Clin Med Phys Source Type: research

Geometric dose prediction model for hemithoracic intensity-modulated radiation therapy in mesothelioma patients with two intact lungs.
Abstract The presence of two intact lungs makes it challenging to reach a tumoricidal dose with hemithoracic pleural intensity-modulated radiation therapy (IMRT) in patients with malignant pleural mesothelioma (MPM) who underwent pleurectomy/decor-tications or have unresectable disease. We developed an anatomy-based model to predict attainable prescription dose before starting optimization. Fifty-six clinically delivered IMRT plans were analyzed regarding correlation of prescription dose and individual and total lung volumes, planning target volume (PTV), ipsilateral normal lung volume and ratios: contralateral/ip...
Source: Journal of Applied Clinical Medical Physics - May 15, 2016 Category: Physics Authors: Kuo L, Yorke ED, Dumane VA, Foster A, Zhang Z, Mechalakos JG, Wu AJ, Rosenzweig KE, Rimner A Tags: J Appl Clin Med Phys Source Type: research

2016 AAPM Spring Clinical Meeting - Abstracts.
PMID: 27167295 [PubMed - in process] (Source: Journal of Applied Clinical Medical Physics)
Source: Journal of Applied Clinical Medical Physics - May 15, 2016 Category: Physics Authors: Authors V Tags: J Appl Clin Med Phys Source Type: research

Why is Healthcare so Expensive in the United States?
PMID: 27167296 [PubMed - in process] (Source: Journal of Applied Clinical Medical Physics)
Source: Journal of Applied Clinical Medical Physics - May 15, 2016 Category: Physics Authors: Mills MD Tags: J Appl Clin Med Phys Source Type: research

Program of the 2016 AAPM Spring Clinical Meeting.
PMID: 27167297 [PubMed - in process] (Source: Journal of Applied Clinical Medical Physics)
Source: Journal of Applied Clinical Medical Physics - May 15, 2016 Category: Physics Authors: Shand A Tags: J Appl Clin Med Phys Source Type: research

2016 AAPM Spring Clinical Meeting - Abstracts
- (Source: Journal of Applied Clinical Medical Physics)
Source: Journal of Applied Clinical Medical Physics - May 5, 2016 Category: Physics Source Type: research

Addendum to brachytherapy dose-volume histogram commissioning with multiple planning systems
The process for validating dose-volume histogram data in brachytherapy software is presented as a supplement to a previously published article. Included is the DVH accuracy evaluation of the Best NOMOS treatment planning system called “Best TPS VolumePlan.” As done previously in other software, a rectangular cuboid was contoured in the treatment planning system. A single radioactive 125I source was positioned coplanar and concentric with one end. Calculations were performed to estimate dose deposition in partial volumes of the cuboid structure, using the brachytherapy dosimetry formalism defined in AAPM Task Gr...
Source: Journal of Applied Clinical Medical Physics - May 5, 2016 Category: Physics Source Type: research

A software tool to automatically assure and report daily treatment deliveries by a Cobalt-60 radiation therapy device
The aims of this study were to develop a method for automatic and immediate verification of treatment delivery after each treatment fraction in order to detect and correct errors, and to develop a comprehensive daily report which includes delivery verification results, daily image-guided radiation therapy (IGRT) review, and information for weekly physics reviews. After systematically analyzing the requirements for treatment delivery verification and understanding the available information from a commercial MRI-guided radiotherapy treatment machine, we designed a procedure to use 1) treatment plan files, 2) delivery log fil...
Source: Journal of Applied Clinical Medical Physics - May 5, 2016 Category: Physics Source Type: research

Effect of electron contamination on in vivo dosimetry for lung block shielding during TBI
Our institution performs in vivo verification measurement for each of our total body irradiation (TBI) patients with optically stimulated luminescent dosimeters (OSLD). The lung block verification measurements were commonly higher than expected. The aim of this work is to understand this discrepancy and improve the accuracy of these lung block verification measurements. Initially, the thickness of the lung block was increased to provide adequate lung sparing. Further tests revealed the increase was due to electron contamination dose emanating from the lung block. The thickness of the bolus material covering the OSLD behind...
Source: Journal of Applied Clinical Medical Physics - May 5, 2016 Category: Physics Source Type: research

On the accuracy of dose prediction near metal fixation devices for spine SBRT
In this study, two commercially available dose prediction algorithms (Eclipse AAA and ACUROS), EGSnrc Monte Carlo, and GAFchromic film measurements were com­pared for a clinical spine SBRT case to determine their accuracy. An open six-field plan and a clinical nine-field IMRT plan were applied to a phantom containing a metal spine fixation device. Dose difference and gamma analysis were performed in and around the tumor region adjacent to the fixation device. Dose calculation inconsistency was observed in the open field plan. However, in the IMRT plan, the dose perturbation effect was not observed beyond 5 mm. Our resu...
Source: Journal of Applied Clinical Medical Physics - May 5, 2016 Category: Physics Source Type: research

Effect of fluoroscopic X-ray beam spectrum on air-kerma measurement accuracy: implications for establishing correction coefficients on interventional fluoroscopes with KAP meters
The first goal of this study was to investigate the accuracy of the displayed reference plane air kerma (Ka,r) or air kerma-area product (Pk,a) over a broad spectrum of X-ray beam qualities on clinically used interventional fluoroscopes incorporating air kerma-area product meters (KAP meters) to measure X-ray output. The second goal was to investigate the accuracy of a correction coefficient (CC) determined at a single beam quality and applied to the measured Ka,r over a broad spectrum of beam qualities. Eleven state-of-the-art interventional fluoroscopes were evaluated, consisting of eight Siemens Artis zee and Artis Q sy...
Source: Journal of Applied Clinical Medical Physics - May 5, 2016 Category: Physics Source Type: research

Improvement in CT image resolution due to the use of focal spot deflection and increased sampling
This study examines the effect of posi­tion and reconstruction algorithm on image resolution achieved by a CT scanner operating in a high resolution (HR) scan mode which incorporates focal spot deflection and acquires an increased number of projections per rotation. Images of a metal bead contained in a phantom were acquired on a GE CT750 HD scanner with multiple reconstruction algorithms, in the normal and HR scan mode, and at two positions, scanner isocenter and 15 cm directly above isocenter. The images of the metal bead yielded two-dimensional point spread functions which were averaged along two perpendicular direc...
Source: Journal of Applied Clinical Medical Physics - May 5, 2016 Category: Physics Source Type: research

Assessment of diffusion tensor image quality across sites and vendors using the American College of Radiology head phantom
The purpose of this study was to explore the feasibility of assessing quality of diffusion tensor imaging (DTI) from multiple sites and vendors using American College of Radiology (ACR) phantom. Participating sites (Siemens (n = 2), GE (n= 2), and Philips (n = 4)) reached consensus on parameters for DTI and used the widely available ACR phantom. Tensor data were processed at one site. B0 and eddy current distortions were assessed using grid line displacement on phantom Slice 5; signal-to-noise ratio (SNR) was measured at the center and periphery of the b = 0 image; fractional anisotropy (FA) and mean diffusivity (MD) were ...
Source: Journal of Applied Clinical Medical Physics - May 5, 2016 Category: Physics Source Type: research

Radiation doses and estimated risk from angiographic projections during coronary angiography performed using novel flat detector
This study intends to evaluate radiation doses and estimated risk from angiographic projections during CA procedure performed using novel flat detector (FD) system with improved image processing and noise reduction techniques. Real-time monitoring of radiation doses using kerma-area product (KAP) meter was performed for 140 patients using Philips Clarity FD system. The CA procedure involved seven standard projections, of which five were extensively selected by interventionalists. Mean fluoroscopic time (FT), KAP, and reference air kerma (Ka,r) for CA procedure were 3.24 min (0.5–10.51), 13.99Gycm2 (4.02–37.6), ...
Source: Journal of Applied Clinical Medical Physics - May 5, 2016 Category: Physics Source Type: research

A qualitative and quantitative analysis of radiation dose and image quality of computed tomography images using adaptive statistical iterative reconstruction
In this study, we assessed CT image quality produced by two reconstruction algorithms provided with GE Healthcare’s Discovery 690 Elite positron emission tomography (PET) CT scanner. Image quality was measured for images obtained at various doses with both conventional filtered back-projection (FBP) and adaptive statistical iterative reconstruction (ASIR) algorithms. A stan­dard CT dose index (CTDI) phantom and a pencil ionization chamber were used to measure the CT dose at 120 kVp and an exposure of 260 mAs. Image quality was assessed using two phantoms. CT images of both phantoms were acquired at tube voltage (...
Source: Journal of Applied Clinical Medical Physics - May 5, 2016 Category: Physics Source Type: research

Image texture and radiation dose properties in CT
The aim of this study was to compare image noise properties of GE Discovery HD 750 and Toshiba Aquilion ONE. The uniformity section of a Catphan 600 image quality assurance phantom was scanned with both scanners, at different dose levels and with extension rings simulating patients of different sizes. 36 datasets were obtained and analyzed in terms of noise power spectrum. All the results prove that introduction of extension rings significantly altered the image quality with respect to noise properties. Without extension rings, the Toshiba scanner had lower total visible noise than GE (with GE as reference: FC18 had 82% an...
Source: Journal of Applied Clinical Medical Physics - May 5, 2016 Category: Physics Source Type: research

Practical considerations for noise power spectra estimation for clinical CT scanners
In this study, the effects of varied calculation parameters on the local NPS were analyzed, and practical suggestions were provided regarding the estimation of local NPS for clinical CT scanners. The uniformity module of a Catphan phantom was scanned with a Philips Brilliance 64 slice CT simulator with varied scanning protocols. Images were reconstructed using FBP and iDose4 iterative reconstruction with noise reduction levels 1, 3, and 6. Local NPS were calculated and compared for varied region of interest (ROI) locations and sizes, image background removal methods, and window functions. Additionally, with a predetermined...
Source: Journal of Applied Clinical Medical Physics - May 5, 2016 Category: Physics Source Type: research

An evaluation of organ dose modulation on a GE optima CT660-computed tomography scanner
Organ Dose Modulation or ODM (GE Healthcare, Milwaukee, WI) was evaluated to characterize changes in CTDIvol, image noise, effective dose, and organ dose saving to patients. Three separate investigations were completed: a tube current modulation phantom was scanned with and without ODM, a CTDIvol phantom was scanned with ODM, and Monte Carlo simulations were performed. ODM was found to reduce the CTDIvol by approximately 20% whilst increasing the noise by approximately 14%. This was reflected in the dose distribution, where the anterior peripheral dose was reduced by approximately 40% whilst the identical poste­rior do...
Source: Journal of Applied Clinical Medical Physics - May 5, 2016 Category: Physics Source Type: research

Geometric dose prediction model for hemithoracic intensity-modulated radiation therapy in mesothelioma patients with two intact lungs
The presence of two intact lungs makes it challenging to reach a tumoricidal dose with hemithoracic pleural intensity-modulated radiation therapy (IMRT) in patients with malignant pleural mesothelioma (MPM) who underwent pleurectomy/decor­tications or have unresectable disease. We developed an anatomy-based model to predict attainable prescription dose before starting optimization. Fifty-six clinically delivered IMRT plans were analyzed regarding correlation of prescription dose and individual and total lung volumes, planning target volume (PTV), ipsilateral normal lung volume and ratios: contralateral/ipsilateral lung...
Source: Journal of Applied Clinical Medical Physics - May 5, 2016 Category: Physics Source Type: research

Dosimetric properties of equivalent-quality flattening filter-free (FFF) and flattened photon beams of Versa HD linear accelerator
This study presents the basic dosimetric properties of photon beams of a Versa HD linear accelerator (linac), which is capable of delivering flattening filter-free (FFF) beams with a beam quality equivalent to the corresponding flattened beams based on comprehensive beam data measurement. The analyzed data included the PDDs, profiles, penumbra, out-of-field doses, surface doses, output factors, head and phantom scatter factors, and MLC transmissions for both FFF and flattened beams of 6 MV and 10 MV energy from an Elekta Versa HD linac. The 6MVFFF and 10MVFFF beams had an equivalent mean energy to the flattened beams and s...
Source: Journal of Applied Clinical Medical Physics - May 5, 2016 Category: Physics Source Type: research

Deformable image registration and interobserver variation in contour propagation for radiation therapy planning
Deformable image registration (DIR) and interobserver variation inevitably intro­duce uncertainty into the treatment planning process. The purpose of the current work was to measure deformable image registration (DIR) errors and interobserver variability for regions of interest (ROIs) in the head and neck and pelvic regions. Measured uncertainties were combined to examine planning margin adequacy for contours propagated for adaptive therapy and to assess the trade-off of DIR and interobserver uncertainty in atlas-based automatic segmentation. Two experi­enced dosimetrists retrospectively contoured brainstem, spinal...
Source: Journal of Applied Clinical Medical Physics - May 5, 2016 Category: Physics Source Type: research

Initial evaluation of automated treatment planning software
We report on the initial evaluation of this algorithm on 10 challenging cases of locoreginally advanced head and neck cancer. All patients were treated with VMAT to 70 Gy to the gross disease and 56 Gy to the elective bilateral nodes. The results of post-treatment autoplanning (AP) were compared to the original human-driven plans (HDP). We used an objective scoring system based on defining a collection of specific dosimetric metrics and corresponding numeric score functions for each. Five AP techniques with different input dose goals were applied to all patients. The best of them averaged the composite score 8% lower than ...
Source: Journal of Applied Clinical Medical Physics - May 5, 2016 Category: Physics Source Type: research

Inverse treatment planning for spinal robotic radiosurgery: an international multi-institutional benchmark trial
Stereotactic radiosurgery (SRS) is the accurate, conformal delivery of high-dose radiation to well-defined targets while minimizing normal structure doses via steep dose gradients. While inverse treatment planning (ITP) with computerized optimization algorithms are routine, many aspects of the planning process remain user-dependent. We performed an international, multi-institutional benchmark trial to study planning variability and to analyze preferable ITP practice for spinal robotic radiosurgery. 10 SRS treatment plans were generated for a complex-shaped spinal metastasis with 21 Gy in 3 fractions and tight constraints f...
Source: Journal of Applied Clinical Medical Physics - May 5, 2016 Category: Physics Source Type: research

Quantification of the margin required for treating intraprostatic lesions
Advances in magnetic resonance imaging (MRI) sequences allow physicians to define the dominant intraprostatic lesion (IPL) in prostate radiation therapy treat­ments allowing for dose escalation and potentially increased tumor control. This work quantifies the margin required around the MRI-defined IPL accounting for both prostate motion and deformation. Ten patients treated with a simultaneous integrated intraprostatic boost (SIIB) were retrospectively selected and replanned with incremental 1 mm margins from 0–5 mm around the IPL to determine if there were any significant differences in dosimetric parameters. Se...
Source: Journal of Applied Clinical Medical Physics - May 5, 2016 Category: Physics Source Type: research

Comparison of manual and automatic MR-CT registration for radiotherapy of prostate cancer
In image-guided radiotherapy (IGRT) of prostate cancer, delineation of the clini­cal target volume (CTV) often relies on magnetic resonance (MR) because of its good soft-tissue visualization. Registration of MR and computed tomography (CT) is required in order to add this accurate delineation to the dose planning CT. An automatic approach for local MR-CT registration of the prostate has previously been developed using a voxel property-based registration as an alternative to a manual landmark-based registration. The aim of this study is to compare the two registration approaches and to investigate the clinical potential...
Source: Journal of Applied Clinical Medical Physics - May 5, 2016 Category: Physics Source Type: research

Assessment of Monte Carlo algorithm for compliance with RTOG 0915 dosimetric criteria in peripheral lung cancer patients treated with stereotactic body radiotherapy
This study evaluated 20 Stage I-II NSCLC patients with peripherally located lung tumors, who underwent MC-based SBRT with heterogeneity correction using X-ray Voxel Monte Carlo (XVMC) algorithm (Brainlab iPlan version 4.1.2). Total dose of 50 to 54 Gy in 3 to 5 fractions was delivered to the planning target vol­ume (PTV) with at least 95% of the PTV receiving 100% of the prescription dose (V100% ≥ 95%). The internal target volume (ITV) was delineated on maximum intensity projection (MIP) images of 4D CT scans. The PTV included the ITV plus 5 mm uniform margin applied to the ITV. The PTV ranged from 11.1 to 163.0 cc ...
Source: Journal of Applied Clinical Medical Physics - May 5, 2016 Category: Physics Source Type: research

EPID based in vivo dosimetry system: clinical experience and results
Mandatory in several countries, in vivo dosimetry has been recognized as one of the next milestones in radiation oncology. Our department has implemented clinically an EPID based in vivo dosimetry system, EPIgray, by DOSISOFT S.A., since 2006. An analysis of the measurements per linac and energy over a two-year period was performed, which included a more detailed examination per technique and treat­ment site over a six-month period. A comparison of the treatment planning system doses and the doses estimated by EPIgray shows a mean of the differences of 1.9% (± 5.2%) for the two-year period. The 3D conformal trea...
Source: Journal of Applied Clinical Medical Physics - May 5, 2016 Category: Physics Source Type: research

VMAT linear accelerator commissioning and quality assurance: dose control and gantry speed tests
In VMAT treatment delivery the ability of the linear accelerator (linac) to accurately control dose versus gantry angle is critical to delivering the plan correctly. A new VMAT test delivery was developed to specifically test the dose versus gantry angle with the full range of allowed gantry speeds and dose rates. The gantry-mounted IBA MatriXX with attached inclinometer was used in movie mode to measure the instantaneous relative dose versus gantry angle during the plan every 0.54 s. The results were compared to the expected relative dose at each gantry angle calculated from the plan. The same dataset was also used to com...
Source: Journal of Applied Clinical Medical Physics - May 5, 2016 Category: Physics Source Type: research

MR image-based synthetic CT for IMRT prostate treatment planning and CBCT image-guided localization
The purpose of this study was to propose and evaluate a method of creating a synthetic CT (S-CT) from MRI simulation for dose calculation and daily CBCT localization. A pair of MR and CT images was obtained in the same day from each of 10 prostate patients. The pair of MR and CT images was preregistered using the deformable image registration (DIR). Using the corresponding displacement vector field (atlas-DVF), the CT image was deformed to the MR image to create an atlas MR-CT pair. Regions of interest (ROI) on the atlas MR-CT pair were delineated and used to create atlas-ROI masks. ‘Leave-one-out’ test (one pa...
Source: Journal of Applied Clinical Medical Physics - May 5, 2016 Category: Physics Source Type: research

Small field detector correction factors: effects of the flattening filter for Elekta and Varian linear accelerators
Flattening filter-free (FFF) beams are becoming the preferred beam type for stereotactic radiosurgery (SRS) and stereotactic ablative radiation therapy (SABR), as they enable an increase in dose rate and a decrease in treatment time. This work assesses the effects of the flattening filter on small field output factors for 6 MV beams generated by both Elekta and Varian linear accelerators, and determines differences between detector response in flattened (FF) and FFF beams. Relative output factors were measured with a range of detectors (diodes, ionization cham­bers, radiochromic film, and microDiamond) and referenced t...
Source: Journal of Applied Clinical Medical Physics - May 5, 2016 Category: Physics Source Type: research

One-year analysis of Elekta CBCT image quality using NPS and MTF
The image quality (IQ) of imaging systems must be sufficiently high for image-guided radiation therapy (IGRT). Hence, users should implement a quality assurance program to maintain IQ. In our routine IQ tests of the kV cone-beam CT system (Elekta XVI), image noise was quantified by noise standard deviation (NSD), which was the standard deviation of CT numbers measured in a small area in an image of an IQ test phantom (Catphan), and the high spatial resolution (HSR) was evaluated by the number of line-pairs (LPN) visually recognizable in the image. We also measured the image uniformity, the low contrast resolution, and the ...
Source: Journal of Applied Clinical Medical Physics - May 5, 2016 Category: Physics Source Type: research

Impact of small MU/segment and dose rate on delivery accuracy of volumetric-modulated arc therapy (VMAT)
Volumetric-modulated arc therapy (VMAT) plans may require more control points (or segments) than some of fixed-beam IMRT plans that are created with a limited number of segments. Increasing number of control points in a VMAT plan for a given prescription dose could create a large portion of the total number of segments with small number monitor units (MUs) per segment. The purpose of this study is to investigate the impact of the small number MU/segment on the delivery accuracy of VMAT delivered with various dose rates. Ten patient datasets were planned for hippocampus sparing for whole brain irradiation. For each dataset,...
Source: Journal of Applied Clinical Medical Physics - May 5, 2016 Category: Physics Source Type: research

Modeling the Agility MLC in the Monaco treatment planning system
We investigate the relationship between the various parameters in the Monaco MLC model and dose calculation accuracy for an Elekta Agility MLC. The vendor-provided MLC modeling procedure — completed first with external vendor participation and then exclusively in-house — was used in combination with our own procedures to investigate several sets of MLC modeling parameters to determine their effect on dose distributions and point-dose measurements. Simple plans provided in the vendor procedure were used to elucidate specific mechanical characteristics of the MLC, while ten complex treatment plans — five IM...
Source: Journal of Applied Clinical Medical Physics - May 5, 2016 Category: Physics Source Type: research

Improved setup and positioning accuracy using a three-point customized cushion/mask/bite-block immobilization system for stereotactic reirradiation of head and neck cancer
The purpose of this study was to investigate the setup and positioning uncertainty of a custom cushion/mask/bite-block (CMB) immobilization system and determine PTV margin for image-guided head and neck stereotactic ablative radiotherapy (HN-SABR). We analyzed 105 treatment sessions among 21 patients treated with HN-SABR for recurrent head and neck cancers using a custom CMB immobilization system. Initial patient setup was performed using the ExacTrac infrared (IR) tracking system and initial setup errors were based on comparison of ExacTrac IR tracking system to corrected online ExacTrac X-rays images registered to treatm...
Source: Journal of Applied Clinical Medical Physics - May 5, 2016 Category: Physics Source Type: research

A preplanning method for stereotactic radiosurgery to improve treatment workflow
We report a practical preplanning solution for the Brainlab iPlan treatment planning system that reduces waiting time by expediting the planning process on treatment day. A water-filled anthropomorphic head phantom was used to acquire a surrogate CT image set for preplanning and fused with patient’s MRI, which was obtained before the day of treatment. Once an acceptable preplan was obtained, it was saved as a plan template and the phantom image set was removed from the Brainlab database to prevent any confusion and mix-up of image sets. On the treatment day, the patient’s CT and MRI were fused, and the customiz...
Source: Journal of Applied Clinical Medical Physics - May 5, 2016 Category: Physics Source Type: research

Evaluation of the tool “Reg Refine” for user-guided deformable image registration
“Reg Refine” is a tool available in the MIM Maestro v6.4.5 platform (www.mim­software.com) that allows the user to actively participate in the deformable image registration process. The purpose of this work was to evaluate the efficacy of this tool and investigate strategies for how to apply it effectively. This was done by performing DIR on two publicly available ground-truth models, the Pixel-based Breathing Thorax Model (POPI) for lung, and the Deformable Image Registration Evaluation Project (DIREP) for head and neck. Image noise matched in both magnitude and texture to clinical CBCT scans was also adde...
Source: Journal of Applied Clinical Medical Physics - May 5, 2016 Category: Physics Source Type: research

Are simple IMRT beams more robust against MLC error? Exploring the impact of MLC errors on planar quality assurance and plan quality for different complexity beams
This study investigated the impact of beam complexities on planar quality assur­ance and plan quality robustness by introducing MLC errors in intensity-modulate radiation therapy. Forty patients’ planar quality assurance (QA) plans were enrolled in this study, including 20 dynamic MLC (DMLC) IMRT plans and 20 static MLC (SMLC) IMRT plans. The total beam numbers were 150 and 160 for DMLC and SMLC, respectively. Six different magnitudes of MLC errors were introduced to these beams. Gamma pass rates were calculated by comparing error-free fluence and error-induced fluence. The plan quality variation was acquired by ...
Source: Journal of Applied Clinical Medical Physics - May 5, 2016 Category: Physics Source Type: research

In-house quality check of external beam plans using 3D treatment planning systems — a DVH comparison
This paper presents a new approach towards the quality assurance of external beam plans using in-house-developed DICOM import and export software in a clinical setup. The new approach is different from what is currently used in most clinics, viz., only MU and point dose are verified. The DICOM-RT software generates ASCII files to import/export structure sets, treatment beam data, and dose-volume histo­grams (DVH) from one treatment planning system (TPS) to the other. An efficient and reliable 3D planning system, ROPS, was used for verifying the accuracy of treatment plans and treatment plan parameters. With the use of ...
Source: Journal of Applied Clinical Medical Physics - May 5, 2016 Category: Physics Source Type: research

Impact of incorporating visual biofeedback in 4D MRI
Precise radiation therapy (RT) for abdominal lesions is complicated by respiratory motion and suboptimal soft tissue contrast in 4D CT. 4D MRI offers improved con­trast although long scan times and irregular breathing patterns can be limiting. To address this, visual biofeedback (VBF) was introduced into 4D MRI. Ten volunteers were consented to an IRB-approved protocol. Prospective respiratory-triggered, T2-weighted, coronal 4D MRIs were acquired on an open 1.0T MR-SIM. VBF was integrated using an MR-compatible interactive breath-hold control system. Subjects visually monitored their breathing patterns to stay within p...
Source: Journal of Applied Clinical Medical Physics - May 5, 2016 Category: Physics Source Type: research

Quantitative evaluation of patient setup uncertainty of stereotactic radiotherapy with the frameless 6D ExacTrac system using statistical modeling
The purpose of this study is to evaluate patient setup accuracy and quantify indi­vidual and cumulative positioning uncertainties associated with different hardware and software components of the stereotactic radiotherapy (SRS/SRT) with the frameless 6D ExacTrac system. A statistical model is used to evaluate positioning uncertainties of the different components of SRS/SRT treatment with the Brainlab 6D ExacTrac system using the positioning shifts of 35 patients having cranial lesions. All these patients are immobilized with rigid head-and-neck masks, simu­lated with Brainlab localizer and planned with iPlan treatm...
Source: Journal of Applied Clinical Medical Physics - May 5, 2016 Category: Physics Source Type: research

Output factor comparison of Monte Carlo and measurement for Varian TrueBeam 6 MV and 10 MV flattening filter-free stereotactic radiosurgery system
In this study, we report a comparison of Monte Carlo simulations and measurements of output factors for the Varian SRS system with conical collimators for energies of 6 MV flattening filter-free (6 MV) and 10 MV flattening filter-free (10 MV) on the TrueBeam accelerator. Monte Carlo simulations of Varian’s SRS system for 6 MV and 10 MV photon energies with cones sizes of 17.5 mm, 15.0 mm, 12.5 mm, 10.0 mm, 7.5 mm, 5.0 mm, and 4.0 mm were performed using EGSnrc (release V4 2.4.0) codes. Varian’s version-2 phase-space files for 6 MV and 10 MV of TrueBeam accelerator were utilized in the Monte Carlo simulations. T...
Source: Journal of Applied Clinical Medical Physics - May 5, 2016 Category: Physics Source Type: research