bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐F‐T‐266: Dynalogs Based Evaluation of Different Dose Rate IMRT Using DVH and Gamma Index
Authors: Ahmed S , Ahmed S , Ahmed F , Hussain A 
Published: July 2016

Purpose:This work investigates the impact of low and high dose rate on IMRT through Dynalogs by evaluating Gamma Index and Dose Volume Histogram.Methods:The Eclipse™ treatment planning software was used to generate plans on prostate and head and neck sites. A range of dose rates 300 MU/min and 600 MU/min were applied to each plan in order to investigate their effect on the beam ON time, efficiency and accuracy. Each plan had distinct monitor units per fraction, delivery time, mean dose rate and leaf speed. The DVH data was used in the assessment of the conformity and plan quality.The treatments were delivered on Varian™ Clinac 2100C accelerator equipped with 120 leaf millennium MLC. Dynalogs of each plan were analyzed by MATLAB™ program. Fluence measurements were performed using the Sun Nuclear™ 2D diode array and results were assessed, based on Gamma analysis of dose fluence maps, beam delivery statistics and Dynalogs data.Results:Minor differences found by adjusted R‐squared analysis of DVH's for all the plans with different dose rates. It has been also found that more and larger fields have greater time reduction at high dose rate and there was a sharp decrease in number of control points observed in dynalog files by switching dose rate from 300 MU/min to 600 MU/min. Gamma Analysis of all plans passes the confidence limit of ≥95% with greater number of passing points in 300 MU/min dose rate plans.Conclusion:The dynalog files are compatible tool for software based IMRT QA. It can work perfectly parallel to measurement based QA setup and stand‐by procedure for pre and post delivery of treatment plan.
SU‐F‐T‐304: Complex Multi‐PTV Treatment Evaluation Using a Remotely Processed 3D Gel Dosimeter
Authors: Hoisak J , Dragojevic I , Sutlief S 
Published: July 2016

Purpose:A new 3D gel dosimeter (ClearView™, Modus Medical Systems) was investigated for use as a QA tool for stereotactic radiosurgery (SRS) plans exhibiting high dose gradients and spatially separated treatment targets. The unique feature of this gel dosimeter is the remote processing service provided by Modus Medical Systems.Methods:The gel dosimeters were filled in either 10 cm diameter or 15 cm diameter clear plastic jars. The jars were then shipped in ice‐cooled containers to our department for irradiation. Clinical SRS plans for treatment of multiple metastases and plans with simulated concave structures were applied to a CT scan of the gel dosimeter. The gel was irradiated in treatment position using modulated arcs and then returned in the cooled container for processing. The 3D gel dose was compared to the DICOM‐RT dose from the treatment plan to assess dosimetric and geometric agreement.Results:There was no discernible difference between the planned and measured dose for dose gradients as high as 10%/mm, which was the highest gradient we evaluated. Geometric agreement for distant metastases separated by 6 cm was within 1.5 mm. Among three identically irradiated gels using a plan intended for nine metastases, the 3%/3mm gamma passing rate was 84.5% with a range of 14.7%, measured over the entire volume of the dosimeter. Regions of larger gamma values correlated with geometric offsets between the planned and measured data.Conclusion:The gel dosimeter exhibits the dosimetric and geometric characteristics necessary for 3D evaluation of treatment plan deliverability. The range of observed gamma passing rates suggests a high sensitivity to geometric registration. With proper management of geometric registration between planned and measured data, this service should enable a radiation oncology department to use 3D dosimetry in end‐to‐end testing or patient plan delivery QA without the expense of an in‐house processing system.
SU‐F‐T‐309: Radiochromic Film Calibration Rescaling for Patient‐Specific CyberKnife MLC QA
Authors: McCaw T , Jang S , Huq M 
Published: July 2016

Purpose:This work investigated the development of EBT3 film as a function of dose rate, and also the accuracy of a commercial calibrationrescaling analysis method, to determine potential application to patientspecific QA of CyberKnife MLC treatments.Methods:EBT3 films were exposed to 300cGy at dose rates ranging from 5–300cGy/min, and scanned repeatedly from 2–5760min after exposure using a flatbed scanner. All other films were scanned 1 and 24hr after exposure. Ten calibration films were exposed to doses between 0 and 800cGy. Four verification films were exposed to doses between 80 and 290cGy, and 0 to 30min later, reference films were exposed to 450cGy. The verification and reference films were scanned together and analyzed both with and without calibration rescaling. The dose distribution of a 36min treatment plan was measured. Immediately prior to the measurement, a reference film was exposed. Both films were scanned together and analyzed both with and without calibration rescaling.Results:The development of EBT3 film is linear with the logarithm of time after exposure. If the midpoint of the exposure duration is taken as time zero, then film development is independent of dose rate. The doses measured with the verification films agreed with the expected dose within 1‐ 2% with calibration rescaling for all reference films. The delay between the exposure of the reference and QA films was 24min relative to the midpoint of exposure. Analysis of the scan at 60min post‐exposure using rescaling of the calibration at 24hr had a gamma passing rate of 92% with 2%/1mm criteria, consistent with analysis of the scan at 24hr post‐exposure without calibration rescaling.Conclusion:Using calibration rescaling, measured doses were accurate within 1–2% 60min after exposure. If the midpoint of exposure is taken as time zero, then calibration rescaling can be applied to patient‐specific QA for CyberKnife MLC treatments.
SU‐F‐T‐310: Does a Head‐Mounted Ionization Chamber Detect IMRT Errors?
Authors: Wegener S , Herzog B , Sauer O 
Published: July 2016

Purpose:The conventional plan verification strategy is delivering a plan to a QA‐phantom before the first treatment. Monitoring each fraction of the patient treatment in real‐time would improve patient safety. We evaluated how well a new detector, the IQM (iRT Systems, Germany), is capable of detecting errors we induced into IMRT plans of three different treatment regions. Results were compared to an established phantom.Methods:Clinical plans of a brain, prostate and head‐and‐neck patient were modified in the Pinnacle planning system, such that they resulted in either several percent lower prescribed doses to the target volume or several percent higher doses to relevant organs at risk. Unaltered plans were measured on three days, modified plans once, each with the IQM at an Elekta Synergy with an Agility MLC. All plans were also measured with the ArcCHECK with the cavity plug and a PTW semiflex 31010 ionization chamber inserted. Measurements were evaluated with SNC patient software.Results:Repeated IQM measurements of the original plans were reproducible, such that a 1% deviation from the mean as warning and 3% as action level as suggested by the manufacturer seemed reasonable. The IQM detected most of the simulated errors including wrong energy, a faulty leaf, wrong trial exported and a 2 mm shift of one leaf bank. Detection limits were reached for two plans ‐ a 2 mm field position error and a leaf bank offset combined with an MU change. ArcCHECK evaluation according to our current standards also left undetected errors. Ionization chamber evaluation alone would leave most errors undetected.Conclusion:The IQM detected most errors and performed as well as currently established phantoms with the advantage that it can be used throughout the whole treatment. Drawback is that it does not indicate the source of the error.
SU‐F‐T‐314: Estimation of Dose Distributions with Different Types of Breast Implants in Various Radiation Treatment Techniques for Breast Cancer
Authors: Lee M , Jung J , Lee S , Kim S , Cho Y , Lee I , Suh T 
Published: July 2016

Purpose:This study investigates the effects of different kinds and designs of commercialized breast implants on the dose distributions in breast cancer radiotherapy under a variety of conditions.Methods:The dose for the clinical conventional tangential irradiation, Intensity Modulated Radiation Therapy (IMRT), volumetric modulated arc therapy (VMAT) breast plans was measured using radiochromic films and stimulated luminescence dosimeter (OSLD). The radiochromic film was used as an integrating dosimeter, while the OSLDs were used for real‐time dosimetry to isolate the contribution of dose from individual segment. The films were placed at various slices in the Rando phantom and between the body and breast surface OSLDs were used to measure skin dose at 18 positions spaced on the two (right/left) breast. The implant breast was placed on the left side and the phantom breast was remained on the right side. Each treatment technique was performed on different size of the breasts and different shape of the breast implant. The PTV dose was prescribed 50.4 Gy and V47.88≥95%.Results:In different shapes of the breast implant, because of the shadow formed extensive around the breast implant, dose variation was relatively higher that of prescribed dose. As the PTV was delineated on the whole breast, maximum 5% dose error and average 3% difference was observed averagely. VMAT techniques largely decrease the contiguous hot spot in the skin by an average of 25% compared with IMRT. The both IMRT and VMAT techniques resulted in lower doses to normal critical structures than tangential plans for nearly all dose analyzation.Conclusion:Compared to the other technique, IMRT reduced radiation dose exposure to normal tissues and maintained reasonable target homogeneity and for the same target coverage, VMAT can reduce the skin dose in all the regions of the body.
SU‐F‐T‐316: A Model to Deal with Dosimetric and Delivery Uncertainties in Radiotherapy Treatment Planning
Authors: Haering P , Lang C , Splinter M 
Published: July 2016

PurposeThe conventional way of dealing with uncertainties resulting from dose calculation or beam delivery in IMRT, is to do verification measurements for the plan in question. Here we present an alternative based on recommendations given in the AAPM 142 report and treatment specific parameters that model the uncertainties for the plan delivery.MethodsBasis of the model is the assignment of uncertainty parameters to all segment fields or control point sequences of a plan. The given field shape is analyzed for complexity, dose rate, number of MU, field size related output as well as factors for in/out field position and penumbra regions. Together with depth related uncertainties, a 3D matrix is generated by a projection algorithm. Patient anatomy is included as uncertainty CT data set as well. Therefore, object density is classified in 4 categories close to water, lung, bone and gradient regions with additional uncertainties. The result is then exported as a DICOM dose file by the software tool (written in IDL, Exelis), having the given resolution and target point.ResultsUncertainty matrixes for several patient cases have been calculated and compared side by side in the planning system. The result is not quite always intuitive but it clearly indicates high and low uncertainties related to OARs and target volumes as well as to measured gamma distributions.ConclusionThe imported uncertainty datasets may help the treatment planner to understand the complexity of the treatment plan. He then might decide to change the plan to produce a more suited uncertainty distribution, e.g. by changing the beam angles the high uncertainty spots can be influenced or try to use another treatment setup, resulting in a plan with lower uncertainties. A next step could be to include such a model into the optimization algorithm to add a new dose uncertainty constraint.
SU‐F‐T‐319: The Impact of Radiation Beam Obliquity and Air Gap Thickness On Optically Stimulated Luminescent in Vivo Dosimetry for Radiation Therapy
Authors: Riegel A , Sea P , Klein E 
Published: July 2016

Purpose:Optically‐stimulated luminescent dosimeters (OSLDs) are increasingly utilized for in vivo dosimetry of complex radiation delivery techniques. Measured doses, however, underestimate planned doses for plans that utilize thermoplastic mask immobilization. The purpose of this work was to quantify the effect of beam obliquity and air gap span between the mask and backscatter material, on measured‐to‐planned OSLD dose agreement.Methods:A previously‐used thermoplastic mask was cut, reheated, and flattened to form a 33 by 9 cm2 stage approximately 2 mm thick. Two OSLDs were placed on the stage on 5 cm of solid water, covered with 50 by 50 by 5 mm3 square of bolus, and scanned in the CT simulator. Plans were created with 10 by 10 cm2 open fields using 4, 6, 10, and 15 MV photon beams at 0°, 45°, and 90° incidence. The isocenter was placed between the OSLDs at 5 mm depth. Dose was calculated and averaged for two OSLDs. Artificial air gaps of 3, 5, 10, and 20 mm were introduced in the plan and dose was recalculated for each energy/angle/gap combination. The experimental setup was replicated on a linear accelerator and air gaps were introduced by “bridging” the thermoplastic stage across solid water plastic of varying thickness. Fields were delivered as planned. OSLDs were read 12–15 hours after irradiation.Results:Measured‐toplanned percent differences were constant with increasing gap thickness for 0° and 45° beam angles. At 90° and 0 cm gap, planned dose underestimated measured dose by 10–23% for all energies. This discrepancy decreased linearly to 0% with a 20 mm gap. OSLD signal did not decrease more than 6% for any gap span and energy.Conclusion:With the exception of parallel beam incidence, beam obliquity and air gap thickness did not have a substantial effect on measured‐to‐planned dose agreement.
SU‐F‐T‐388: Comparison of Biophysical Indices in Hippocampal‐Avoidance Whole Brain VMAT and IMRT Radiation Therapy Treatment Plans
Authors: Kendall E , Ahmad S , Algan O , Higby C , Hossain S 
Published: July 2016

Purpose:To compare biophysical indices of Volumetric Modulated Arc Therapy (VMAT) and Intensity Modulated Radiation Therapy (IMRT) treatment plans for whole brain radiation therapy following the NRG‐CC001 protocol.Methods:In this retrospective study, a total of fifteen patients were planned with Varian Eclipse Treatment Planning System using VMAT (RapidArc) and IMRT techniques. The planning target volume (PTV) was defined as the whole brain volume excluding a uniform three‐dimensional 5mm expansion of the hippocampus volume. Prescribed doses in all plans were 30 Gy delivered over 10 fractions normalized to a minimum of 95% of the target volume receiving 100% of the prescribed dose. The NRG Oncology protocol guidelines were followed for contouring and dose‐volume constraints. A single radiation oncologist evaluated all treatment plans. Calculations of statistical significance were performed using Student's paired t‐test.Results:All VMAT and IMRT plans met the NRG‐CC001 protocol dose‐volume criteria. The average equivalent uniform dose (EUD) for the PTV for VMAT vs. IMRT was respectively (19.05±0.33 Gy vs. 19.38±0.47 Gy) for α/β of 2 Gy and (19.47±0.30 Gy vs. 19.84±0.42 Gy) for α/β of 10 Gy. For the PTV, the average mean and maximum doses were 2% and 5% lower in VMAT plans than in IMRT plans, respectively. The average EUD and the normal tissue complication probability (NTCP) for the hippocampus in VMAT vs. IMRT plans were (15.28±1.35 Gy vs. 15.65±0.99 Gy, p=0.18) and (0.305±0.012 Gy vs. 0.308±0.008 Gy, p=0.192), respectively. The average EUD and NTCP for the optic chiasm were both 2% higher in VMAT than in IMRT plans.Conclusion:Though statistically insignificant, VMAT plans indicate a lower hippocampus EUD than IMRT plans. Also, a small variation in NTCP was found between plans.
SU‐F‐T‐390: Dosimetric Impact of Leaf Interdigitation in Prostate Cancer Dynamic IMRT Treatment Planning
Authors: Duan J 
Published: July 2016

Purpose:The aim of this work is to study the dosimetric impact of leaf interdigitation in prostate cancer dynamic IMRT treatment planning.Methods:Fifteen previously treated prostate cancer patients were replanned for dynamic IMRT (dMLC) with and without leaf interdigitation using Monaco 3.3 TPS on the Elekta Synergy linear accelerator. The prescription dose of PTV was 70Gy/35 fractions. Various dosimetric variables, such as PTV coverage, OAR sparing, delivery efficiency and optimization time, were evaluated for each plan.Results:Interdigitation did not improve the coverage, HI and CI for PTV. Regarding OARs, sparing was equivalent with and without interdigitation. Interdigitation shown an increase in MUs and segments. It was worth noting that leaf interdigitation saved the optimization time.Conclusion:This study shows that leaf interdigitation does not improve plan quality when performing dMLC treatment plan for prostate cancer. However, it influences delivery efficiency and optimization time. Interdigitation may gain efficiency for dosimetrist when designing the prostate cancer dMLC plans.
SU‐F‐T‐391: Comparative Study of Treatment Planning Between IMRT and IMAT for Malignant Pleural Mesothelioma
Authors: Duan J 
Published: July 2016

Purpose:The purpose of this study was to compare the dosimetric differences between intensitymodulated radiation therapy (IMRT) and intensity modulated arc therapy (IMAT) for malignant pleural mesothelioma (MPM) patients with regard to the sparing effect on organs at risk (OARs), plan quality, and delivery efficiency.Methods:Ten MPM patients were recruited in this study. To avoid the inter‐operator variability, IMRT and IMAT plans for each patient were performed by one experienced dosimetrist. The treatment planning optimization process was carried out using the Eclipse 13.0 software. For a fair comparison, the planning target volume (PTV) coverage of the two plans was normalized to the same level. The treatment plans were evaluated on the following dosimetric variables: conformity index (CI) and homogeneity index (HI) for PTV, OARs dose, and the delivery efficiency for each plan.Results:All plans satisfied clinical requirements. The IMAT plans gained better CI and HI. The IMRT plans performed better sparing for heart and lung. Less MUs and control points were found in the IMAT plans. IMAT shortened delivery time compared with IMRT.Conclusion:For MPM, IMAT gains better conformity and homogeneity for PTV with IMRT, but increases the irradiation dose for OARs. IMAT shows an advantage in delivery efficiency.
SU‐F‐T‐392: Superior Brainstem and Cochlea Sparing with VMAT for Glioblastoma Multiforme
Authors: Briere TM , McAleer MF , Levy LB , Yang JN , Anderson MD 
Published: July 2016

Purpose:Volumetric arc therapy (VMAT) can provide similar target coverage and normal tissue sparing as IMRT but with shorter treatment times. At our institution VMAT was adopted for the treatment glioblastoma multiforme (GBM) after a small number of test plans demonstrated its non‐inferiority. In this study, we compare actual clinical treatment plans for a larger cohort of patients treated with either VMAT or IMRT.Methods:90 GBM patients were included in this study, 45 treated with IMRT and 45 with VMAT. All planning target volumes (PTVs) were prescribed a dose of 50 Gy, with a simultaneous integrated boost to 60 Gy. Most IMRT plans used 5 non‐coplanar beams, while most VMAT plans used 2 coplanar beams. Statistical analysis was performed using Fisher's exact test or the Wilcoxon‐Mann‐Whitney rank sum test. Included in the analysis were patient and treatment characteristics as well as the doses to the target volumes and organs at risk.Results:Treatment times for the VMAT plans were reduced by 5 minutes compared with IMRT. The PTV coverage was similar, with at least 95% covered for all plans, while the median boost PTV dose differed by 0.1 Gy between the IMRT and VMAT cohorts. The doses to the brain, optic chiasm, optic nerves and eyes were not significantly different. The mean dose to the brainstem, however, was 9.4 Gy less with VMAT (p<0.001). The dose to the ipsilateral and contralateral cochleae were respectively 19.7 and 9.5 Gy less (p<0.001).Conclusion:Comparison of clinical treatment plans for separate IMRT and VMAT cohorts demonstrates that VMAT can save substantial treatment time while providing similar target coverage and superior sparing of the brainstem and cochleae. To our knowledge this is the first study to demonstrate this benefit of VMAT in the management of GBM.
SU‐F‐T‐405: Development of a Rapid Cardiac Contouring Tool Using Landmark‐Driven Modeling
Authors: Pelletier C , Mosher E , Lee C , Lee C , Jung J 
Published: July 2016

Purpose:This study aims to develop a tool to rapidly delineate cardiac substructures for use in dosimetry for large‐scale clinical trial or epidemiological investigations. The goal is to produce a system that can semi‐automatically delineate nine cardiac structures to a reasonable accuracy within a couple of minutes.Methods:The cardiac contouring tool employs a Most Similar Atlas method, where a selection criterion is used to pre‐select the most similar model to the patient from a library of pre‐defined atlases. Sixty contrast‐enhanced cardiac computed tomography angiography (CTA) scans (30 male and 30 female) were manually contoured to serve as the atlas library. For each CTA 12 structures were delineated. Kabsch algorithm was used to compute the optimum rotation and translation matrices between the patient and atlas. Minimum root mean squared distance between the patient and atlas after transformation was used to select the most‐similar atlas. An initial study using 10 CTA sets was performed to assess system feasibility. Leave‐one patient out method was performed, and fit criteria were calculated to evaluate the fit accuracy compared to manual contours.Results:For the pilot study, mean dice indices of .895 were achieved for the whole heart, .867 for the ventricles, and .802 for the atria. In addition, mean distance was measured via the chord length distribution (CLD) between ground truth and the atlas structures for the four coronary arteries. The mean CLD for all coronary arteries was below 14mm, with the left circumflex artery showing the best agreement (7.08mm).Conclusion:The cardiac contouring tool is able to delineate cardiac structures with reasonable accuracy in less than 90 seconds. Pilot data indicates that the system is able to delineate the whole heart and ventricles within a reasonable accuracy using even a limited library. We are extending the atlas sets to 60 adult males and females in total.