bluuebunny/crossref_metadata_2025_split huggingface dataset:
Clinical consequences of changing the sliding window IMRT dose rate
Authors: Ghasroddashti E. , Smith W.L. , Quirk S. , Kirkby C. 
Published: February 2017

Changing pulse repetition frequency or dose rate used for IMRT treatments can alter the number of monitor units (MUs) and the time required to deliver a plan. This work was done to develop a practical picture of the magnitude of these changes. We used Varian's Eclipse Treatment Planning System to calculate the number of MUs and beam‐on times for a total of 40 different treatment plans across an array of common IMRT sites including prostate/pelvis, prostate bed, head and neck, and central nervous system cancers using dose rates of 300, 400 and . In general, we observed a 4%–7% increase in the number of MUs delivered and a 10–40 second decrease in the beam‐on time for each of dose rate increase. The increase in the number of MUs resulted in a reduction of the “beam‐on time saved”. The exact magnitude of the changes depended on treatment site and planning target volume. These changes can lead to minor, but not negligible, concerns with respect to radiation protection and treatment planning. Although the number of MUs increased more rapidly for more complex treatment plans, the absolute beam‐on time savings was greater for these plans because of the higher total number of MUs required to deliver them. We estimate that increasing the IMRT dose rate from 300 to has the potential to add up to two treatment slots per day for each IMRT linear accelerator. These results will be of value to anyone considering general changes to IMRT dose rates within their clinic.PACS number: 87.55.N
Proton dose perturbations caused by high‐voltage leads from implanted cardioverter defibrillators
Authors: Wootton Landon S. , Polf Jerimy C. , Peterson Stephen , Wilkinson Jeff , Rozner Marc A. , Balter Peter A. , Beddar Sam 
Published: February 2017

An increasing number of patients undergoing proton radiotherapy have cardiac implantable electrical devices (CIEDs). We recently encountered a situation in which a high‐voltage coil on a lead from an implanted cardiac defibrillator was located within the clinical treatment volume for a patient receiving proton radiotherapy for esophageal cancer. To study the effects of the lead on the dose delivery, we placed a high‐Z CIED lead at both the center and the distal edge of a clinical spread‐out Bragg peak (SOBP) in a water phantom, in both a stationary position and with the lead moving in a periodic pattern to simulate cardiorespiratory movement. We then calculated planned doses using a commercial proton treatment planning system (TPS), and compared them with the doses delivered in the phantom, measured using radiographic film. Dose profiles from TPS‐calculated and measured dose distributions showed large pertubrations in the delivered proton dose in the vicinity of the CIED lead when it was not moving. The TPS predicted perturbations up to 20% and measurements revealed perturbations up to 35%. However, the perturbations were less than 3% when the lead was moving. Greater dose perturbations were seen when the lead was placed at the distal edge of the SOBP than when it was placed in the center of the SOBP. We conclude that although cardiorespiratory motion of the lead mitigates some of the perturbations, the effects of the leads should be considered and steps taken to reduce these effects during the treatment planning process.PACS numbers: 87.55.D‐,87.55.ne, 87.85.M
The prospect of carbon fiber implants in radiotherapy
Authors: Xin‐ye Ni , Xiao‐bin Tang , Chang‐ran Geng , Da Chen 
Published: February 2017

Because of their superior characteristics, carbonaceous materials, which are still at their early stage of development, have garnered significant interest. Because of their low atomic number, carbonaceous orthopedic implants possess radiation properties similar to biological tissues and, therefore, they are more suitable to patients in need of radiotherapy. The effects of stainless steel, titanium, and carbon plates on radiation dose distributions were investigated in this work using Monte Carlo simulations and TLD measurements for 6 MV photon beams. It is found that carbon plates will neither increase the incident surface dose, nor lead to the decrease of exit surface dose (the effect of a second build‐up). Carbon fiber orthopedic implants have a good prospect for radiotherapy patients because they have minimal perturbation effects on the radiotherapy dose distribution.PACS number: 87.55.K‐,87.55.Gh, 87.55.ne
An experimental investigation on the effect of beam angle optimization on the reduction of beam numbers in IMRT of head and neck tumors
Authors: Narayanan V. K. Sathiya , Vaitheeswaran R. , Bhangle Janhavi R. , Basu Sumit , Maiya Vikram , Zade Bhooshan 
Published: February 2017

In static intensity‐modulated radiation therapy (IMRT), the fundamental factors that determine the quality of a plan are the number of beams and their angles. The objective of this study is to investigate the effect of beam angle optimization (BAO) on the beam number in IMRT. We used six head and neck cases to carry out the study. Basically the methodology uses a parameter called “Beam Intensity Profile Perturbation Score” (BIPPS) to determine the suitable beam angles in IMRT. We used two set of plans in which one set contains plans with equispaced beam configuration starting from beam numbers 3 to 18, and another set contains plans with optimal beam angles chosen using the in‐house BAO algorithm. We used quadratic dose‐based single criteria objective function as a measure of the quality of a plan. The objective function scores obtained for equispaced beam plans and optimal beam angle plans for six head and neck cases were plotted against the beam numbers in a single graphical plot for effective comparison. It is observed that the optimization of beam angles reduces the beam numbers required to produce clinically acceptable dose distribution in IMRT of head and neck tumors. Especially (represents the beam number at which the objective function reaches a value of 0.1) is considerably reduced by beam angle optimization in almost all the cases included in the study. We believe that the experimental findings of this study will be helpful in understanding the interplay between beam angle optimization and beam number selection process in IMRT which, in turn, can be used to improve the performance of BAO algorithms and beam number selection process in IMRT.PACS number: 87.55.de
Application of AAPM TG 119 to volumetric arc therapy (VMAT)
Authors: Mynampati Dinesh Kumar , Yaparpalvi Ravindra , Hong Linda , Kuo Hsiang‐Chi , Mah Dennis 
Published: February 2017

The purpose of this study was to create AAPM TG 119 benchmark plans for volumetric arc therapy (VMAT) and to compare VMAT plans with IMRT plan data. AAPM TG 119 proposes a set of test clinical cases for testing the accuracy of IMRT planning and delivery system. For these test cases, we generated two treatment plans, the first plan using 7–9 static dMLC IMRT fields and a second plan utilizing one‐ or two‐arc VMAT technique. Dose optimization and calculations performed using 6 MV photons and Eclipse treatment planning system. Dose prescription and planning objectives were set according to the TG 119 goals. Plans were scored based on TG 119 planning objectives. Treatment plans were compared using conformity index (CI) for reference dose and homogeneity index (HI) (for ). F or test cases prostate, head‐and‐neck, C‐shape and multitarget prescription dose are 75.6 Gy, 50.4 Gy, 50 Gy and 50 Gy, respectively. VMAT dose distributions were comparable to dMLC IMRT plans. Our planning results matched TG 119 planning results. For treatment plans studied, conformity indices ranged from 1.05–1.23 (IMRT) and 1.04–1.23 (VMAT). Homogeneity indices ranged from 4.6%–11.0% (IMRT) and 4.6%–10.5% (VMAT). The ratio of total monitor units necessary for dMLC IMRT to that of VMAT was in the range of 1.1–2.0. AAPM TG 119 test cases are useful to generate VMAT benchmark plans. At preclinical implementation stage, plan comparison of VMAT and IMRT plans of AAPM TG 119 test case allowed us to understand basic capabilities of VMAT technique.PACS number: 87.55.Qr
Comparing dose in the build‐up region between compensator‐ and MLC‐based IMRT
Authors: Javedan Khosrow , Zhang Geoffrey G. , Hoffe Sarah , Feygelman Vladimir , Forster Kenneth 
Published: February 2017

The build‐up dose in the megavoltage photon beams can be a limiting factor in intensity‐modulated radiation therapy (IMRT) treatments. Excessive surface dose can cause patient discomfort and treatment interruptions, while underdosing may lead to tumor repopulation and local failure. Dose in the build‐up region was investigated for IMRT delivery with solid brass compensator technique (compensator‐based IMRT) and compared with that of multileaf collimator (MLC)‐based IMRT. A Varian Trilogy linear accelerator equipped with an MLC was used for beam delivery. A special solid brass step‐wise compensator was designed and built for testing purposes. Two step‐and‐shoot MLC fields were programmed to produce a similar modulated step‐wise dose profile. The MLC and compensator dose profiles were measured and adjusted to match at the isocenter depth of 10 cm. Build‐up dose in the 1–5 mm depth range was measured with an ultrathin window, fixed volume parallel plate ionization chamber. Monte Carlo simulations were used to model the brass compensator and step‐and‐shoot MLC fields. The measured and simulated profiles for the two IMRT techniques were matched at the isocenter depth of 10 cm. Different component contributions to the shallow dose, including the MLC scatter, were quantified. Mean spectral energies for the open and filtered beams were calculated. The compensator and MLC profiles at 10 cm depth were matched better than . The build‐up dose was up to 7% lower for compensator IMRT compared to MLC IMRT due to beam hardening in the brass. Low‐energy electrons contribute 22% and 15% dose at 1 mm depth for compensator and MLC modalities, respectively. Compensator‐based IMRT delivers less dose in the build‐up region than MLC‐based IMRT does, even though a compensator is closer to the skin than the MLC.PACS number: 87.55.dk, 87.56.ng
Providing a fast conversion of total dose to biological effective dose (BED) for hybrid seed brachytherapy
Authors: Pritz Jakub , Forster Kenneth M. , Saini Amarjit S. , Biagioli Matthew C. , Zhang Geoffrey G. 
Published: February 2017

Optimization of permanent seed implant brachytherapy plans for treatment of prostate cancer should be based on biological effective dose (BED) distributions, since dose does not accurately represent biological effects between different types of sources. Currently, biological optimization for these plans is not feasible due to the amount of time necessary to calculate the BED distribution. This study provides a fast calculation method, based on the total dose, to calculate the BED distribution. Distributions of various numbers of hybrid seeds were used to calculate total dose distributions, as well as BED distributions. Hybrid seeds are a mixture of different isotopes (in this study 125I and 103Pd). Three ratios of hybrid seeds were investigated: 25/75, 50/50, and 75/25. The total dose and BED value from each voxel were coupled together to produce graphs of total dose vs. BED. Equations were then derived from these graphs. The study investigated four types of tissue: bladder, rectum, prostate, and other normal tissue. Equations were derived from the total dose – BED correspondence. Accuracy of conversion from total dose to BED was within 2 Gy; however, accuracy of conversion was found to be better for high total dose regions as compared to lower dose regions. The method introduced in this paper allows one to perform fast conversion of total dose to BED for brachytherapy using hybrid seeds, which makes the BED‐based plan optimization practical. The method defined here can be extended to other ratios, as well as other tissues that are affected by permanent seed implant brachytherapy (i.e., breast).PACS number: 87.55.de
The energy margin strategy for reducing dose variation due to setup uncertainty in intensity modulated proton therapy (IMPT) delivered with distal edge tracking (DET)
Authors: Zhang Miao , Flynn Ryan T. , Mo Xiaohu , Mackie Thomas Rock 
Published: February 2017

Intensity‐modulated proton therapy (IMPT) can produce plans with similar target dose conformity but lower normal tissue dose than intensity‐modulated X‐ray therapy (IMXT). However, due to the finite range of proton beams in tissue, proton therapy treatment plans are usually more sensitive to setup uncertainties than X‐ray therapy plans. In this work, the energy margin (EM) concept, which was initially developed for passive scattering proton therapy, was generalized to apply to IMPT treatment planning. The effectiveness of the EM method was evaluated on five head‐and‐neck cancer patients with distal edge tracking (DET) treatment plans by comparing the original plans (ORG) without an EM to those with an EM. Three beam arrangements were considered: 24 beams delivered over a 360° arc, 12 beams delivered over a 180° arc, and 12 beams delivered over two 90° fan angles. Setup uncertainty was modeled by sampling rigid translational shifts from a Gaussian distribution with a mean of 0 mm and standard deviation of 2 mm in all directions. Delivered dose distributions for all 30 fractions were recalculated using the Geant4 Monte Carlo code. Normalized total dose (NTD) for both the CTV and a ring structure surrounding the PTV were recorded. The plan quality comparison revealed that EM plans had the same CTV coverage but higher dose to the normal tissue than ORG plans. After the simulated delivery, ORG plans resulted in more than 3% underdosage to 5% of the CTV volume in all three beam arrangements, whereas the EM plans did not. Both ORG and EM plans did not produce more than 5% overdose to of the ring structure. The use of an EM for IMPT treatment planning can substantially reduce sensitivity of the resulting dose distributions to setup uncertainty.PACS number: 87.55.K‐
A phantom study to determine the optimum size of a single collimator for shortening the treatment time in CyberKnife stereotactic radiosurgery of spherical targets
Authors: Harikrishnaperumal Sudahar , Kurup Gopalakrishna , Venkatraman Murali , Jagadeesan Velmurugan 
Published: February 2017

Prolonged treatment execution time is a concern in CyberKnife robotic radiosurgery. Beam reduction and node reduction technique, and monitor unit optimization methods are adopted to reduce the treatment time. Usage of single collimator in the CyberKnife treatment plan can potentially reduce collimator exchange time. An optimal single collimator, which yields an acceptable dose distribution along with minimum number of nodes, beams, and monitor units, can be a versatile alternative for shortening treatment time. The aim of the present study is to find the optimal single collimator in CyberKnife treatment planning to shorten the treatment time with the acceptable dose distribution. A spherical planning target volume PTV1 was drawn in an anthropomorphic head and neck phantom. Plans with same treatment goals were generated for all the 12 collimators independently. was selected as the prescribing isodose and the prescribed dose was 10 Gy. The plan of the optimal collimator size was evaluated for conformity, homogeneity, and dose spillage outside the target. The optimum collimator size and the target dimensions were correlated. The study was repeated with two other target volumes PTV2 and PTV3 for generalizing the results. Collimator sizes just above the diameter of the spherical PTVs were yielding least number of nodes and beams with acceptable dose distributions. The collimator size of 35 mm is optimum for the PTV1, whose diameter is 31.4 mm. Similarly, 50 mm collimator is optimum for PTV2 and 20 mm collimator is optimum for PTV3 . The total number of monitor units is found to reduce with increasing collimator size. Optimal single collimator is found to be useful for shortening the treatment time in spherical targets. Studies on two clinical targets, (a brain metastasis and a liver metastasis cases) show comparable results with the phantom study.PACS numbers: 87.55.D, 87.55.de, 87.53.Ly, 87.55.kh, 87.56.nk, 87.55.ne, 87.55.‐x
Effectiveness of a novel gas‐release endorectal balloon in the removal of rectal gas for prostate proton radiation therapy
Authors: Wootton Landon S. , Kudchadker Rajat J. , Beddar A. Sam , Lee Andrew K. 
Published: February 2017

Endorectal balloons (ERBs) are routinely used in prostate proton radiation therapy to immobilize the prostate and spare the rectal wall. Rectal gas can distend the rectum and displace the prostate even in the presence of ERBs. The purpose of this work was to quantify the effects an ERB with a passive gas release conduit had on the incidence of rectal gas. Fifteen patients who were treated with a standard ERB and 15 with a gas‐release ERB were selected for this retrospective study. Location and cross‐sectional area of gas pockets and the fraction of time they occurred on 1133 lateral kilovoltage (kV) images were analyzed. Gas locations were classified as trapped between the ERB and anterior rectal wall, between the ERB and posterior rectal wall, or superior to the ERB. For patients using the standard ERB, gas was found in at least one region in 45.8% of fractions. Gas was trapped in the anterior region in 37.1% of fractions, in the posterior region in 5.0% of fractions, and in the sigmoid region in 9.6% of fractions. For patients using the ERB with the gas‐release conduit, gas was found in at least one region in 19.7% of fractions. Gas was trapped in the anterior region in 5.6% of fractions, in the posterior region in 8.3% of fractions, and in the sigmoid region in 7.4% of fractions. Both the number of fractions with gas in the anterior region and the number of fractions with gas in at least one region were significantly higher in the former group than in the latter. The cross‐sectional area of trapped gas did not differ between the two groups. Thus gas‐release balloon can effectively release gas, and may be able to improve clinical workflow by reducing the need for catheterization.PACS number: 87.56.Da
Radiation dose and physical image quality in 128‐section dual‐source computed tomographic coronary angiography: a phantom study
Authors: Matsubara Kosuke , Koshida Haruka , Sakuta Keita , Takata Tadanori , Horii Junsei , Iida Hiroji , Koshida Kichiro , Ichikawa Katsuhiro , Matsui Osamu 
Published: February 2017

One‐hundred‐and‐twenty‐eight–section dual X‐ray source computed tomography (CT) systems have been introduced into clinical practice and have been shown to increase temporal resolution. Higher temporal resolution allows low‐dose spiral mode at a high pitch factor during CT coronary angiography. We evaluated radiation dose and physical image qualities in CT coronary angiography by applying high‐pitch spiral, step‐and‐shoot, and low‐pitch spiral modes to determine the optimal acquisition mode for clinical situations. An anthropomorphic phantom, small dosimeters, a calibration phantom, and a microdisc phantom were used to evaluate the radiation doses absorbed by thoracic organs, noise power spectrums, in‐plane and z‐axis modulation transfer functions, slice sensitivity profiles, and number of artifacts for the three acquisition modes. The high‐pitch spiral mode had the advantage of a small absorbed radiation dose, but provided low image quality. The low‐pitch spiral mode resulted in a high absorbed radiation dose of approximately 200 mGy for the heart. Although the absorbed radiation dose was lower in the step‐and‐shoot mode than in the low‐pitch spiral mode, the noise power spectrum was inferior. The quality of the in‐plane modulation transfer function differed, depending on spatial frequency. Therefore, the step‐and‐shoot mode should be applied initially because of its low absorbed radiation dose and superior image quality.PACS numbers: 87.57.‐s; 87.57.C‐; 87.57.cf; 87.57.cm; 87.57.cp; 87.57.Q‐; 87.57.qp; 87.57.uq
Determination of optimal fiducial marker across image‐guided radiation therapy (IGRT) modalities: visibility and artifact analysis of gold, carbon, and polymer fiducial markers
Authors: Handsfield Lydia L. , Yue Ning J. , Zhou Jinghao , Chen Ting , Goyal Sharad 
Published: February 2017

The purpose of this study was to evaluate the visibility and artifact created by gold, carbon, and polymer fiducial markers in a simple phantom across computed tomography (CT), kilovoltage (kV), and megavoltage (MV) linear accelerator imaging and MV tomotherapy imaging. Three types of fiducial markers (gold, carbon, and polymer) were investigated for their visibility and artifacts in images acquired with various modalities and with different imaging parameters (kV, mAs, slice thickness). The imaging modalities include kV CT, 2D linac‐based kilovoltage and megavoltage X‐ray imaging systems, kV cone‐beam CT, and normal and fine tomotherapy imaging. The images were acquired on a phantom constructed using Superflab bolus in which markers of each type were inserted into the center layer. The visibility and artifacts produced by each marker were assessed qualitatively and quantitatively. All tested markers could be identified clearly on the acquired CT and linac‐based kV images; gold markers demonstrated the highest contrast. On the CT images, gold markers produced a significant artifact, while no artifacts were observed with polymer markers. Only gold markers were visible when using linac‐based MV and tomotherapy imaging. For linac‐based kV images, the contrast increased with kV and mAs values for all the markers, with the gold being the most pronounced. On CT images, the contrast increased with kV for the gold markers, while decreasing for the polymer and carbon marker. With the bolus phantom used, we found that when kV imaging‐based treatment verification equipment is available, polymer and carbon markers may be the preferred choice for target localization and patient treatment positioning verification due to less image artifacts. If MV imaging will be the sole modality for positioning verification, it may be necessary to use gold markers despite the artifacts they create on the simulation CT images.PACS number: 87