bluuebunny/crossref_metadata_2025_split huggingface dataset:
Commissioning of a motion system to investigate dosimetric consequences due to variability of respiratory waveforms
Authors: Cetnar Ashley J. , James Joshua , Wang Brain 
Published: February 2017

A commercially available six‐dimensional (6D) motion system was assessed for accuracy and clinical use in our department. Positional accuracy and respiratory waveform reproducibility were evaluated for the motion system. The system was then used to investigate the dosimetric consequences of respiratory waveform variation when an internal target volume (ITV) approach is used for motion management. The maximum deviations are 0.3 mm and 0.22° for translation and rotation accuracy, respectively, for the tested clinical ranges. The origin reproducibility is less than . The average differences are less than 0.1 mm with a maximum standard deviation of 0.8 mm between waveforms of actual patients and replication of those waveforms by HexaMotion for three breath‐hold and one free‐breathing waveform. A modified gamma analysis shows greater than 98% agreement with a 0.5 mm and 100 ms threshold. The motion system was used to investigate respiratory waveform variation and showed that, as the amplitude of the treatment waveform increases above that of the simulation waveform, the periphery of the target volume receives less dose than expected. However, by using gating limits to terminate the beam outside of the simulation amplitude, the results are as expected dosimetrically. Specifically, the average dose difference in the periphery between treating with the simulation waveform and the larger amplitude waveform could be up to 12% less without gating limits, but only differed 2% or less with the gating limits in place. The general functionality of the system performs within the manufacturer's specifications and can accurately replicate patient specific waveforms. When an ITV approach is used for motion management, we found the use of gating limits that coincide with the amplitude of the patient waveform at simulation helpful to prevent the potential underdosing of the target due to changes in patient respiration.PACS numbers: 87.55.Kh, 87.55.Qr, 87.56.Fc
Performance variations among clinically available deformable image registration tools in adaptive radiotherapy — how should we evaluate and interpret the result?
Authors: Nie Ke , Pouliot Jean , Smith Eric , Chuang Cynthia 
Published: February 2017

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 transformation matrices served as a “reference” for the following comparisons. Three commercialized DIR algorithms: the free‐form deformation from MIMVista 5.5 and the RegRefine from MIMMaestro 6.0, the multipass B‐spline from VelocityAI v3.0.1, and the adaptive demons from OnQ rts 2.1.15, were applied between the initial images and the deformed CT sets. The generated adaptive contours and dose distributions were compared with the “reference” and among each other. The performance in transferring contours was comparable among all three tools with an average Dice similarity coefficient of 0.81 for all the organs. However, the dose warping accuracy appeared to rely on the evaluation end points and methodologies. Point‐dose differences could show a difference of up to 23.3 Gy inside the PTVs and to overestimate up to 13.2 Gy for OARs, which was substantial for a 72 Gy prescription dose. Dosevolume histogram‐based evaluation might not be sensitive enough to illustrate all the detailed variations, while isodose assessment on a slice‐by‐slice basis could be tedious. We further explored the possibility of using 3D gamma index analysis for warping dose variation assessment, and observed differences in dose warping using different DIR tools. Overall, our results demonstrated that evaluation based only on the performance of contour transformation could not guarantee the accuracy in dose warping, while dose‐transferring validation strongly relied on the evaluation endpoint. As dose‐transferring errors could cause misinterpretations when attempting to accumulate dose for adaptive radiation therapy and more DIR tools are available for clinical use, a standard and clinically meaningful quality assurance criterion should be established for DIR QA in the near future.PACS number(s): 87.57
Evaluation of the range shifter model for proton pencil‐beam scanning for the Eclipse v.11 treatment planning system
Authors: Matysiak Witold , Yeung Daniel , Slopsema Roelf , Li Zuofeng 
Published: February 2017

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 thicknesses of the RS in the beam path. The Eclipse version 11 (v11) treatment planning system (TPS) models RS‐induced beam widening by incorporating the scattering properties of the RS material into the V‐parameter. Monte Carlo simulations with Geant4 code and analytical calculations using the Fermi‐Eyges (FE) theory with Highland approximation of multiple Coulomb scattering (MCS) were employed to calculate proton beam widening due to scattering in the RS. We demonstrated that both methods achieved consistent results and could be used as a benchmark for evaluating the Eclipse V‐parameter model. In most cases, the V‐parameter model correctly predicted the beam spot size after traversing the RS. However, Eclipse did not enforce the constraint for a nonnegative covariance matrix when fitting the spot sizes to derive the phase space parameters, which resulted in incorrect calculations under specific conditions. In addition, Eclipse v11 incorrectly imposed limits on the individual values of the phase space parameters, which could lead to incorrect spot size values in the air calculated for beams with spot sigmas . Notably, the TPS supplier (Varian) and hardware vendor (Ion Beam Applications) inconsistently refer to the RS position, which may result in improper spot size calculations.PACS number(s): 87.53.Jw, 87.53.Kn, 87.55.kd, 87.56.‐v
Beam perturbation characteristics of a 2D transmission silicon diode array, Magic Plate
Authors: Alrowaili Ziyad A. , Lerch Michael L.F. , Petasecca Marco , Carolan Martin G. , Metcalfe Peter E. , Rosenfeld Anatoly B. 
Published: February 2017

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). The MP was placed in the block tray of a Varian linac head operated at 6, 10 and 18 MV beam energy. To optimize the MPTM operational setup, two conditions were investigated and each setup was compared to the case where no MP is positioned in place (i.e., open field): (i) MPTM alone and (ii) MPTM with a thin passive contamination electron filter. The in‐field and out‐of‐field surface doses of a solid water phantom were investigated for both setups using a Markus plane parallel (Model N23343) and Attix parallel‐plate, MRI model 449 ionization chambers. In addition, the effect on the 2D dose distribution measured by the Delta4 QA system was also investigated. The transmission factor for both of these MPTM setups in the central axis was also investigated using a Farmer ionization chamber (Model 2571A) and an Attix ionization chamber. Measurements were performed for different irradiation field sizes of and . The change in the surface dose relative to was measured to be less than 0.5% for the 6 MV, 10 MV, and 18 MV energy beams. Transmission factors measured for both set ups (i & ii above) with 6 MV, 10 MV, and 18 MV at a depth of and a depth of 10 cm were all within 1.6% of open field. The impact of both the bare MPTM and the MPTM with 1 mm buildup on 3D dose distribution in comparison to the open field investigated using the Delta4 system and both the MPTM versions passed standard clinical gamma analysis criteria. Two MPTM operational setups were studied and presented in this article. The results indicate that both versions may be suitable for the new real‐time megavoltage photon treatment delivery QA system under development. However, the bare MPTM appears to be slightly better suited of the two MP versions, as it minimally perturbs the radiation field and does not lead to any significant increase in skin dose to the patient.PACS number(s): 87.50.up, 87.53.Bn, 87.55.N, 87.55.Qr, 87.56.Fc.
Gafchromic film dosimetry of a new HDR brachytherapy source
Authors: Ayoobian Navid , Asl Akbar Sarabi , Poorbaygi Hosein , Javanshir Mohammad Reza 
Published: February 2017

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 source, referred to as IRAsource‐HDR, in PMMA phantom in the framework of AAPM TG‐43 and TG‐55 recommendations for radial distances of 0.5 cm to 4 cm. Radiochromic films (RCFs) Gafchromic EBT and HD‐810 were used for measurements. The dose rate constant, Λ, of the source was determined to be , and using EBTRCF, HD‐810 RCF, and Monte Carlo (MC) simulation, respectively. The results obtained in this study are in good agreement with previously published data for HDR interstitial ‐HDR sources with a maximum discrepancy of . An acceptable agreement (within ) between MC calculations and RCFs measurements showed that HD‐810 RCF dosimetry is as good as EBTRCF, within HDR brachytherapy, and justifies the use of specific data for this new source. These data could be used as a benchmark for dose calculations in the conventional brachytherapy treatment planning systems.PACS number(s): 87.56.bg
Correction of nonuniformity error of Gafchromic EBT2 and EBT3
Authors: Katsuda Toshizo , Gotanda Rumi , Gotanda Tatsuhiro , Akagawa Takuya , Tanki Nobuyoshi , Kuwano Tadao , Yabunaka Kouichi 
Published: February 2017

This study investigates an X‐ray dose measurement method for computed tomography using Gafchromic films. Nonuniformity of the active layer is a major problem in Gafchromic films. In radiotherapy, nonuniformity error is reduced by applying the double‐exposure technique, but this is impractical in diagnostic radiology because of the heel effect. Therefore, we propose replacing the X‐rays in the double‐exposure technique with ultraviolet (UV)‐A irradiation of Gafchromic EBT2 and EBT3. To improve the reproducibility of the scan position, Gafchromic EBT2 and EBT3 films were attached to a 3‐mm‐thick acrylic plate. The samples were then irradiated with a 10 W UV‐A fluorescent lamp placed at a distance of 72 cm for 30, 60, and 90 minutes. The profile curves were evaluated along the long and short axes of the film center, and the standard deviations of the pixel values were calculated over large areas of the films. Paired t‐test was performed. UV‐A irradiation exerted a significant effect on Gafchromic EBT2 (paired t‐test; ) but not on EBT3 (paired t‐test; ). Similarly, the homogeneity was improved in Gafchromic EBT2 but not in EBT3. Therefore, the double‐exposure technique under UV‐A irradiation is suitable only for EBT2 films.PACS number(s): 87.53 Bn
Evaluation of the Eclipse eMC algorithm for bolus electron conformal therapy using a standard verification dataset
Authors: Carver Robert L. , Sprunger Conrad P. , Hogstrom Kenneth R. , Popple Richard A. , Antolak John A. 
Published: February 2017

The purpose of this study was to evaluate the accuracy and calculation speed of electron dose distributions calculated by the Eclipse electron Monte Carlo (eMC) algorithm for use with bolus electron conformal therapy (ECT). The recent commercial availability of bolus ECT technology requires further validation of the eMC dose calculation algorithm. eMC‐calculated electron dose distributions for bolus ECT have been compared to previously measured TLD‐dose points throughout patient‐based cylindrical phantoms (retromolar trigone and nose), whose axial cross sections were based on the mid‐PTV (planning treatment volume) CT anatomy. The phantoms consisted of SR4 muscle substitute, SR4 bone substitute, and air. The treatment plans were imported into the Eclipse treatment planning system, and electron dose distributions calculated using 1% and statistical uncertainties. The accuracy of the dose calculations using moderate smoothing and no smoothing were evaluated. Dose differences (eMC‐calculated less measured dose) were evaluated in terms of absolute dose difference, where 100% equals the given dose, as well as distance to agreement (DTA). Dose calculations were also evaluated for calculation speed. Results from the eMC for the retromolar trigone phantom using 1% statistical uncertainty without smoothing showed calculated dose at of the measured TLD‐dose points was within 3% dose difference or 3 mm DTA of the measured value. The average dose difference was , and the net standard deviation was 2.32%. Differences as large as 3.7% occurred immediately distal to the mandible bone. Results for the nose phantom, using 1% statistical uncertainty without smoothing, showed calculated dose at of the measured TLD‐dose points within 3% dose difference or 3 mm DTA. The average dose difference was 1.08%, and the net standard deviation was 3.17%. Differences as large as 10% occurred lateral to the nasal air cavities. Including smoothing had insignificant effects on the accuracy of the retromolar trigone phantom calculations, but reduced the accuracy of the nose phantom calculations in the high‐gradient dose areas. Dose calculation times with 1% statistical uncertainty for the retromolar trigone and nose treatment plans were 30 s and 24 s, respectively, using 16 processors (Intel Xeon E5‐2690, 2.9 GHz) on a framework agent server (FAS). In comparison, the eMC was significantly more accurate than the pencil beam algorithm (PBA). The eMC has comparable accuracy to the pencil beam redefinition algorithm (PBRA) used for bolus ECT planning and has acceptably low dose calculation times. The eMC accuracy decreased when smoothing was used in high‐gradient dose regions. The eMC accuracy was consistent with that previously reported for accuracy of the eMC electron dose algorithm and shows that the algorithm is suitable for clinical implementation of bolus ECT.PACS number(s): 87.55.kd
Using daily diagnostic quality images to validate planning margins for prostate interfractional variations
Authors: Li Wen , Vassil Andrew , Godley Andrew , Mossolly Lama Muhieddine , Shang Qingyang , Xia Ping 
Published: February 2017

The purpose of this study is to use the same diagnostic‐quality verification and planning CTs to validate planning margin account for residual interfractional variations with image‐guided soft tissue alignment of the prostate. For nine prostate cancer patients treated with IMRT to 78 Gy in 39 fractions, daily verification CT‐on‐rails images of the first seven and last seven fractions were retrospectively selected for this study. On these images, prostate, bladder, and rectum were delineated by the same attending physician. Clinical plans were created with a margin of 8 mm except for 5 mm posteriorly, referred to as 8/5 mm. Three additional plans were created for each patient with the margins of 6/4 mm, 4/2 mm, and 2 mm uniform. These plans were subsequently applied to daily images and radiation doses were recalculated. The isocenters of these plans were placed according to clinical online shifts, which were based on soft tissue alignment to the prostate. Retrospective offline shifts by aligning prostate contours were compared to online shifts. The resultant daily target dose was analyzed using , the percentage of the prescription dose received by 99% of CTV. The percent of bladder volume receiving and rectum were also analyzed. After interfractional correction, using CTV % criteria, 8/5 mm, 6/4 mm, 4/2 mm, and 2 mm planning margins met the CTV dose coverage in 95%, 91%, 65%, and 53% of the 126 fractions with online shifts, and 99%, 98%, 85%, and 68% with offline shifts. The rectum and bladder were significantly decreased at each level of margin reduction (). With daily diagnostic quality imaging‐guidance, the interfractional planning margin may be reduced from 8/5 mm to 6/4 mm. The residual interfractional uncertainties most likely stem from prostate rotation and deformation.PACS number(s): 87.53.‐j
Impact of incorporating visual biofeedback in 4D MRI
Authors: To David T. , Kim Joshua P. , Price Ryan G. , Chetty Indrin J. , Glide‐Hurst Carri K. 
Published: February 2017

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 predetermined tolerances. 4D MRIs were acquired with and without VBF for 2‐ and 8‐phase acquisitions. Normalized respiratory waveforms were evaluated for scan time, duty cycle (programmed/acquisition time), breathing period, and breathing regularity (end‐inhale coefficient of variation, EI‐COV). Three reviewers performed image quality assessment to compare artifacts with and without VBF. Respiration‐induced liver motion was calculated via centroid difference analysis of end‐exhale (EE) and EI liver contours. Incorporating VBF reduced 2‐phase acquisition time ( and with and without VBF, respectively) while reducing EI‐COV by . For 8‐phase acquisitions, VBF reduced acquisition time by and EI‐COVs by despite breathing rate remaining similar ( breaths/min with vs. without). Using VBF yielded higher duty cycles than unguided free breathing ( vs. , respectively). Image grading showed that out of 40 paired evaluations, 20 cases had equivalent and 17 had improved image quality scores with VBF, particularly for mid‐exhale and EI. Increased liver excursion was observed with VBF, where superior–inferior, anterior–posterior, and left–right EE‐EI displacements were , , and , respectively, with VBF compared to , , and without. Incorporating VBF into 4D MRI substantially reduced acquisition time, breathing irregularity, and image artifacts. However, differences in excursion were observed, thus implementation will be required throughout the RT workflow.PACS number(s): 87.55.‐x, 87.61.‐c, 87.19.xj
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
Authors: Wang Jiazhou , Jin Xiance , Peng Jiayuan , Xie Jiang , Chen Junchao , Hu Weigang 
Published: February 2017

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 comparing PTV coverage. Eight complexity scores were calculated based on the beam fluence and the MLC sequence. The complexity scores include fractal dimension, monitor unit, modulation index, fluence map complexity, weighted average of field area, weighted average of field perimeter, and small aperture ratio . The Spearman's rank correlation coefficient was calculated to analyze the correlation between these scores and gamma pass rate and plan quality variation. For planar QA, the most significant complexity index was fractal dimension for DMLC and weighted segment area for SMLC at low magnitude MLC error. For plan quality, the most significant complexity index was weighted segment perimeter for DMLC and weighted segment area for SMLC at low magnitude MLC error. The sensitivity of planar QA was weakly associated with the field complexity with low magnitude MLC error, but the plan quality robustness was associated with beam complexity. Plans with simple beams were more robust to MLC error.PACS number(s): 87.55
A preplanning method for stereotactic radiosurgery to improve treatment workflow
Authors: Ahn Kang‐Hyun , Ozturk Naim , Smith Brett , Slavin Konstantin V. , Koshy Matthew , Aydogan Bulent 
Published: February 2017

Frame‐based stereotactic radiosurgery (SRS) requires fixation of an invasive head ring to ensure accurate targeting. Minimizing waiting time with a fixed head ring is important for patient comfort and satisfaction. 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 customized beam settings of the preplan template were then applied and optimized. Up to 10‐fold of reduction in treatment plan time was demonstrated by bench testing with multiple planners and a variety of cases. Loading the plan template and fine‐tuning the preconfigured beam settings took only a small fraction of the preplan time to restore the conformity and dose falloff comparable to those of the preplan. For instance, preplan time was 2 hr for a two‐isocenter case, whereas, it took less than 20 min for a less experienced planner to plan it on the day of treatment using the preplan method. The SRS preplanning technique implemented in this study for the Brainlab iPlan treatment planning system offers an opportunity to explore possible beam configurations thoroughly, optimize planning parameters, resolve gantry angle clearance issues, and communicate and address challenges with physicians before the treatment day. Preplanning has been proven to improve plan quality and to improve efficiency in our clinic, especially for multiple‐isocenter and dosimetrically challenging cases.PACS number(s): 87.53.Ly, 87.55.D‐, 87.55.Gh, 87.55.tm