bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐F‐T‐300: Impact of Electron Density Modeling of ArcCHECK Cylindricaldiode Array On 3DVH Patient Specific QA Software Tool Analysis
Authors: Patwe P , Mhatre V , Dandekar P 
Published: July 2016

Purpose:3DVH software is a patient specific quality assurance tool which estimates the 3D dose to the patient specific geometry with the help of Planned Dose Perturbation algorithm. The purpose of this study is to evaluate the impact of HU value of ArcCHECK phantom entered in Eclipse TPS on 3D dose & DVH QA analysis.Methods:Manufacturer of ArcCHECK phantom provides CT data set of phantom & recommends considering it as a homogeneous phantom with electron density (1.19 gm/cc or 282 HU) close to PMMA. We performed this study on Eclipse TPS (V13, VMS) & trueBEAM STx VMS Linac & ArcCHECK phantom (SNC). Plans were generated for 6MV photon beam, 20cm×20cm field size at isocentre & SPD (Source to phantom distance) of 86.7 cm to deliver 100cGy at isocentre. 3DVH software requires patients DICOM data generated by TPS & plan delivered on ArcCHECK phantom. Plans were generated in TPS by assigning different HU values to phantom. We analyzed gamma index & the dose profile for all plans along vertical down direction of beam's central axis for Entry, Exit & Isocentre dose.Results:The global gamma passing rate (2% & 2mm) for manufacturer recommended HU value 282 was 96.3%. Detector entry, Isocentre & detector exit Doses were 1.9048 (1.9270), 1.00(1.0199) & 0.5078(0.527) Gy for TPS (Measured) respectively.The global gamma passing rate for electron density 1.1302 gm/cc was 98.6%. Detector entry, Isocentre & detector exit Doses were 1.8714 (1.8873), 1.00(0.9988) & 0.5211(0.516) Gy for TPS (Measured) respectively.Conclusion:Electron density value assigned by manufacturer does not hold true for every user. Proper modeling of electron density of ArcCHECK in TPS is essential to avoid systematic error in dose calculation of patient specific QA.
SU‐F‐T‐312: Identifying Distinct Radiation Therapy Plan Classes Through Multi‐Dimensional Analysis of Plan Complexity Metrics
Authors: Desai V , Labby Z , Culberson W 
Published: July 2016

Purpose:To determine whether body site‐specific treatment plans form unique “plan class” clusters in a multi‐dimensional analysis of plan complexity metrics such that a single beam quality correction determined for a representative plan could be universally applied within the “plan class”, thereby increasing the dosimetric accuracy of a detector's response within a subset of similarly modulated nonstandard deliveries.Methods:We collected 95 clinical volumetric modulated arc therapy (VMAT) plans from four body sites (brain, lung, prostate, and spine). The lung data was further subdivided into SBRT and non‐SBRT data for a total of five plan classes. For each control point in each plan, a variety of aperture‐based complexity metrics were calculated and stored as unique characteristics of each patient plan. A multiple comparison of means analysis was performed such that every plan class was compared to every other plan class for every complexity metric in order to determine which groups could be considered different from one another. Statistical significance was assessed after correcting for multiple hypothesis testing.Results:Six out of a possible 10 pairwise plan class comparisons were uniquely distinguished based on at least nine out of 14 of the proposed metrics (Brain/Lung, Brain/SBRT lung, Lung/Prostate, Lung/SBRT Lung, Lung/Spine, Prostate/SBRT Lung). Eight out of 14 of the complexity metrics could distinguish at least six out of the possible 10 pairwise plan class comparisons.Conclusion:Aperture‐based complexity metrics could prove to be useful tools to quantitatively describe a distinct class of treatment plans. Certain plan‐averaged complexity metrics could be considered unique characteristics of a particular plan. A new approach to generating plan‐class specific reference (pcsr) fields could be established through a targeted preservation of select complexity metrics or a clustering algorithm that identifies plans exhibiting similar modulation characteristics. Measurements and simulations will better elucidate potential plan‐class specific dosimetry correction factors.
SU‐F‐T‐386: Analysis of Three QA Methods for Predicting Dose Deviation Pass Percentage for Lung SBRT VMAT Plans
Authors: Hardin M , To D , Giaddui T , Li J , Yu Y , Harrison A 
Published: July 2016

Purpose:To investigate the significance of using pinpoint ionization chambers (IC) and RadCalc (RC) in determining the quality of lung SBRT VMAT plans with low dose deviation pass percentage (DDPP) as reported by ScandiDos Delta4 (D4). To quantify the relationship between DDPP and point dose deviations determined by IC (ICDD), RadCalc (RCDD), and median dose deviation reported by D4 (D4DD).Methods:Point dose deviations and D4 DDPP were compiled for 45 SBRT VMAT plans. Eighteen patients were treated on Varian Truebeam linear accelerators (linacs); the remaining 27 were treated on Elekta Synergy linacs with Agility collimators. A one‐way analysis of variance (ANOVA) was performed to determine if there were any statistically significant differences between D4DD, ICDD, and RCDD. Tukey's test was used to determine which pair of means was statistically different from each other. Multiple regression analysis was performed to determine if D4DD, ICDD, or RCDD are statistically significant predictors of DDPP.Results:Median DDPP, D4DD, ICDD, and RCDD were 80.5% (47.6%–99.2%), −0.3% (−2.0%–1.6%), 0.2% (−7.5%–6.3%), and 2.9% (−4.0%–19.7%), respectively. The ANOVA showed a statistically significant difference between D4DD, ICDD, and RCDD for a 95% confidence interval (p < 0.001). Tukey's test revealed a statistically significant difference between two pairs of groups, RCDD‐D4DD and RCDD‐ICDD (p < 0.001), but no difference between ICDD‐D4DD (p = 0.485). Multiple regression analysis revealed that ICDD (p = 0.04) and D4DD (p = 0.03) are statistically significant predictors of DDPP with an adjusted r2 of 0.115.Conclusion:This study shows ICDD predicts trends in D4 DDPP; however this trend is highly variable as shown by our low r2. This work suggests that ICDD can be used as a method to verify DDPP in delivery of lung SBRT VMAT plans. RCDD may not validate low DDPP discovered in D4 QA for small field SBRT treatments.
SU‐F‐T‐387: A Novel Optimization Technique for Field in Field (FIF) Chestwall Radiation Therapy Using a Single Plan to Improve Delivery Safety and Treatment Planning Efficiency
Authors: Tabibian A , Kim A , Rose J , Alvelo M , Perel C , Laiken K , Sheth N 
Published: July 2016

Purpose:A novel optimization technique was developed for field‐in‐field (FIF) chestwall radiotherapy using bolus every other day. The dosimetry was compared to currently used optimization.Methods:The prior five patients treated at our clinic to the chestwall and supraclavicular nodes with a mono‐isocentric four‐field arrangement were selected for this study. The prescription was 5040 cGy in 28 fractions, 5 mm bolus every other day on the tangent fields, 6 and/or 10 MV x‐rays, and multileaf collimation.Novelly, tangents FIF segments were forward planned optimized based on the composite bolus and non‐bolus dose distribution simultaneously. The prescription was spilt into 14 fractions for both bolus and non‐bolus tangents. The same segments and monitor units were used for the bolus and non‐bolus treatment. The plan was optimized until the desired coverage was achieved, minimized 105% hotspots, and a maximum dose of less than 108%. Each tangential field had less than 5 segments.Comparison plans were generated using FIF optimization with the same dosimetric goals, but using only the non‐bolus calculation for FIF optimization. The non‐bolus fields were then copied and bolus was applied. The same segments and monitor units were used for the bolus and non‐bolus segments.Results:The prescription coverage of the chestwall, as defined by RTOG guidelines, was on average 51.8% for the plans that optimized bolus and non‐bolus treatments simultaneous (SB) and 43.8% for the plans optimized to the non‐bolus treatments (NB). Chestwall coverage of 90% prescription averaged to 80.4% for SB and 79.6% for NB plans. The volume receiving 105% of the prescription was 1.9% for SB and 0.8% for NB plans on average.Conclusion:Simultaneously optimizing for bolus and non‐bolus treatments noticeably improves prescription coverage of the chestwall while maintaining similar hotspots and 90% prescription coverage in comparison to optimizing only to non‐bolus treatments.
SU‐F‐T‐389: Validation in 4D Dosimetry Using Dynamic Phantom
Authors: Lin C , Huang T , Lin C , Nien H , Tu P , Lui L , Wu C 
Published: July 2016

Purpose:Tumor motion due to respiration causes the uncertainties during the radiotherapy. This study aims to find the differences between planning dose by treatment planning and the received dose using dynamic phantom.Methods:Respiratory motion was simulated by the DYNAMIC THORAX PHANTOM (Model 008A). 4D‐CT scans and maximum intensity projection (MIP) images for GTV were acquired for analysis. The amplitude of craniocaudal tumor motion including 2mm, 5mm, 10mm and 20mm with 3cm2 tumor size were performed in this study. The respiratory cycles of 4‐seconds and 6‐seconds were included as the different breathing modes. IMRT, VAMT, and Tomotherapy were utilized for treatment planning. Ion chamber and EBT3 were used to measure the point dose and planar dose. Dose distributions with different amplitudes, respiratory cycles, and planning techniques were all measured and compared to calculations.Results:The variations between the does measurements and calculation dose by treatment planning system were found in both point dose and dose distribution. The 0.83% and 5.46 % differences in dose average were shown on phantom with motions using 2mm amplitude in 4 second respiratory cycle, and 20mm amplitude in 4 second respiratory cycle, respectively. The most point dose overestimation as compared of the calculations was shown the plan generated by Tomotherapy. The underestimations of planar dose as compared of calculations was found in the 100% coverage doses for GTV.Conclusion:The loss of complete (100%) GTV coverage was the predominant effect of respiratory motion observed in this study. Motion amplitude and treatment planning system were the major factors leading the dose measurement variation as compared of planning calculations.
SU‐F‐T‐394: Impact of PTV Margins With Taking Into Account Shape Variation On IMRT Plans For Prostate Cancer
Authors: Hirose T , Arimura H , Shibayama Y , Fukunaga J , Umezu Y , Oga S , Sasaki T 
Published: July 2016

Purpose:The purpose of this study was to investigate the impact of planning target volume (PTV) margins with taking into consideration clinical target volume (CTV) shape variations on treatment plans of intensity modulated radiation therapy (IMRT) for prostate cancer.Methods:The systematic errors and the random errors for patient setup errors in right‐left (RL), anterior‐posterior (AP), and superior‐inferior (SI) directions were obtained from data of 20 patients, and those for CTV shape variations were calculated from 10 patients, who were weekly scanned using cone beam computed tomography (CBCT). The setup error was defined as the difference in prostate centers between planning CT and CBCT images after bone‐based registrations. CTV shape variations of high, intermediate and low risk CTVs were calculated for each patient from variances of interfractional shape variations on each vertex of three‐dimensional CTV point distributions, which were manually obtained from CTV contours on the CBCT images. PTV margins were calculated using the setup errors with and without CTV shape variations for each risk CTV. Six treatment plans were retrospectively made by using the PTV margins with and without CTV shape variations for the three risk CTVs of 5 test patients. Furthermore, the treatment plans were applied to CBCT images for investigating the impact of shape variations on PTV margins.Results:The percentages of population to cover with the PTV, which satisfies the CTV D98 of 95%, with and without the shape variations were 89.7% and 74.4% for high risk, 89.7% and 76.9% for intermediate risk, 84.6% and 76.9% for low risk, respectively.Conclusion:PTV margins taking into account CTV shape variation provide significant improvement of applicable percentage of population (P < 0.05). This study suggested that CTV shape variation should be taken consideration into determination of the PTV margins.
SU‐F‐T‐400: Clinical Comparison of An IMRT Plan Computed with Four Algorithms
Authors: Barbiere J , Ndlovu A 
Published: July 2016

Purpose:This work demonstrates clinical differences in a prostate IMRT plan DVH depending on which of four common algorithms is used for computation. Previous comparisons were often based on simple static or re‐optimized IMRT plans which may not be clearly indicative of the clinical end result due solely to the computation algorithm.Methods:A step and shoot prostate multiple field IMRT plan was created in Pinnacle with a Collapsed Cone Convolution Superposition (CCCS) algorithm. The computed patient plan with corresponding dose and the control points without dose were both independently exported to Eclipse. Using the same patient image and structure data sets the control points were recomputed with the Anisotropic Analytical Algorithm (AAA) and Acuros XB for dose‐to‐water in medium (AXBwater) and dose‐to‐medium in medium (AXBmedium). All DVH values were measured in Eclipse to eliminated known differences between various DVH systems. A 0.3cm3 volume was created at the isocenter for point dose (PD) comparison.Results:The prostate target Acuros dose‐to‐medium in medium is clearly different than the others with a mean value of 101.7 cGy versus 103.8, 103.5 and 103.1 cGy for AAA, CCCS and AXBwater respectively. The difference in other clinical parameters such as volume at 105% dose (V105) is also unexpectedly different with values of 1.6, 23.9, 16.0 and 11.6 % respectively. The mean value in a small volume around the isocenter was 99.6, 102.4, 102.2 and 101.5 respectively which though not a great difference could affect the plan normalization and add to other effects in all regions of interest. The V102 is 25% larger for AAA compared to AXBwater. The variation in V50 for the bladder and rectum was approximately 5%.Conclusion:This work demonstrates how an individual plan can be recomputed and compared directly between various algorithms and that clinical parameters can indeed vary according to which algorithm is used for computation.
SU‐F‐T‐404: Dosimetric Advantages of Flattening Free Beams to Prone Accelerated Partial Breast Irradiation
Authors: Galavis P , Barbee D , Jozsef G 
Published: July 2016

Purpose:Prone accelerated partial breast irradiation (APBI) results in dose reduction to the heart and lung. Flattening filter free beams (FFF) reduce out of field dose due to the reduced scatter from the removal of the flattening filter and reduce the buildup region. The aim of this work is to evaluate the dosimetric advantages of FFF beams to prone APBI target coverage and reduction in dose to organs at risk.Methods:Fifteen clinical prone APBI cases using flattened photon beams were retrospectively re‐planned in Eclipse‐TPS using FFF beams. FFF plans were designed to provide equivalent target coverage with similar hotspots using the same field arrangements, resulting in comparable target DVHs. Both plans were transferred to a prone breast phantom and delivered on Varian‐Edge‐Linac. GafChromic‐film was placed in the coronal plane of the phantom, partially overlapping the treatment field and extending into OARs to compare dose profiles from both plans.Results:FFF plans were comparable to the clinical plans with maximum doses of (108.3±2.3)% and (109.2±2.4)% and mean doses of (104.5±1.0)% and (104.6±1.2)%, respectively. Similar mean dose doses to the heart and contralateral lungs were observed from both plans, whereas the mean dose to the contra‐lateral breast was (2.79±1.18) cGy and (2.86±1.40) cGy for FFF and clinical plans respectively. However for both plans the error between calculated and measured doses at 4 cm from the field edge was 10%.Conclusion:The results showed that FFF beams in prone APBI provide dosimetrically equivalent target coverage and improved coverage in superficial target due to softer energy spectra. Film analysis showed that the TPS underestimates dose outside field edges for both cases. The FFF measured plans showed less dose outside the beam that might reduce the probability of secondary cancers in the contralateral breast.
SU‐F‐T‐407: Artifact Reduction with Dual Energy Or IMAR: Who's Winning?
Authors: Elder E , Schreibmann E , Dhabaan A 
Published: July 2016

Purpose:The purpose of this abstract was to evaluate the performance of commercial strategies for artifact reduction in radiation oncology settings. The iterative metal artifact reduction (Siemens iMAR) algorithm and monoenergetic virtual datasets reconstructed from dual energy scans are compared side‐by‐side in their ability to image in the presence of metal inserts.Methods:A CIRS ATOM Dosimetry Verification Phantom was scanned with and without a metal insert on a SOMATOM Definition AS dual energy scanner. Images with the metal insert were reconstructed with (a) a tradition single energy CT scan with the iMAR option implemented, using different artifact reduction settings and (b) a monoenergetic scan calculated from dual energy scans by recovering differences in the energy‐dependence of the attenuation coefficients of different materials and then creating a virtual monoenergetic scan from these coefficients. The iMAR and monoenergetic scans were then compared with the metal‐free scan to assess changes in HU numbers and noise within a region around the metal insert.Results:Both the iMAR and dual energy scans reduced artifacts produced by the metal insert. However the iMAR results are dependent of the selected algorithm settings, with a mean HU difference ranging from 0.65 to 90.40 for different options. The mean differences without the iMAR correction were 38.74. When using the dual energy scan, the mean differences were 4.53, that is however attributed to increased noise and not artifacts, as the dual energy scan had the lowest skewness (2.52) compared to the iMAR scans (ranging from 3.90 to 4.88) and the lowest kurtosis (5.72 for dual energy, range of 18.19 to 27.36 for iMAR).Conclusion:Both approaches accurately recovered HU numbers, however the dual energy method provided smaller residual artifacts.
SU‐F‐T‐415: Differences in Lung Sparing in Deep Inspiration Breath‐Hold and Free Breathing Breast Plans Calculated in Pinnacle and Monaco
Authors: Saenz D , Stathakis S 
Published: July 2016

Purpose:Deep inspiration breath‐hold (DIBH) is used for left‐sided breast radiotherapy to spare the heart and lung. The magnitude of sparing has been shown to be significant. Monte Carlo, furthermore, has the potential to calculate most accurately the dose in the heterogeneous lung medium at the interface with the lung wall. The lung dose was investigated in Monaco to determine the level of sparing relative to that calculated in Pinnacle3.Methods:Five patients undergoing DIBH radiotherapy on an Elekta Versa HD linear accelerator in conjunction with the Catalyst C‐RAD surface imaging system were planned using Phillips Pinnacle3. Free breathing plans were also created to clinically assure a benefit. Both plans were re‐calculated in Monaco to determine if there were any significant differences. The mean heart dose, mean left lung, and mean total lung dose were compared in addition to the V20 for left and both lungs. Dose was calculated as dose to medium as well as dose to water with a statistical precision of 0.7%.Results:Mean lung dose was significantly different (p < 0.003) between the two calculations for both DIBH (11.6% higher in Monaco) and free breathing (14.2% higher in Monaco). V20 was also higher in Monaco (p < 0.05) for DIBH (5.7% higher) and free breathing (4.9% higher). The mean heart dose was not significantly different between the dose calculations for either DIBH or free breathing. Results were no more than 0.1% different when calculated as dose to water.Conclusion:The use of Monte Carlo can provide insight on the lung dose for both free breathing and DIBH techniques for whole breast irradiation. While the sparing (dose reductions with DIBH as compared to free breathing) is equivalent for either planning system, the lung doses themselves are higher when calculated with Monaco.
SU‐F‐T‐416: Dosimetric Comparison of Coplanar and Non‐Coplanar IMRT Plans for Peripheral Lung Lesion
Authors: Kang J , Zhang S , Philbrook S , Paul S , Wang B 
Published: July 2016

Purpose:The purpose of this study was to compare dosimetric parameters of treatment plans between coplanar and non‐coplanar techniques for treating peripheral lung lesions.Methods:The planning CT scans of 6 patients in supine positions were used in this study. The size of the PTV ranges from 163 c.c. to 782 c.c.. The locations of PTV are mostly at the peripheral of Lung, some spreading to the mediastinum. For each patient, we generated two IMRT plans, one with and the other without non‐coplanar beams. The non‐coplanar beams were carefully selected so that the beams would never exit patient bodies through the contralateral lung. The IMRT plans were generated with Pinnacle 9.8 treatment planning software. The IMRT optimization objectives were kept the same for the corresponding pairs of plans. All plans were normalized such that 95% of PTV receives the prescription dose (full dose).Results:The conformity index (mean±standard deviation of the mean) is 1.49±0.14 and 1.58±0.23 for the coplanar and noncoplanar plans, respectively. The heterogeneity index (mean±standard deviation of the mean) is 7.74 ±2.33 and 6.34±1.40 for the coplanar and non‐coplanar plans, respectively. The maximum heart dose is 60.94±6.22 and 60.42±7.21 Gy, and mean heart dose is 10.22 ±7.57, 9.07 ±6.32 Gy, for the coplanar and non‐coplanar plans, respectively. The ipsilateral lung V20 is 48.0%±2.4% and 47.5%±3.3%, and V5 is 68.2%±10.0% and 69.1%±7.3%, for the coplanar and noncoplanar plans, respectively. Furthermore, with the non‐coplanar beam arrangement, the contralateral lung V20 was reduced from 3.3%±3.7% to 1.3%±0.8%, and the contralateral Lung V5 is reduced significantly from 65.6%±9.3% to 33.5%±20.9% (p value =0.008).Conclusion:The IMRT plans with non‐coplanar beam arrangement could reduce the exit dose to the contralateral lung, and therefore reduce the contralateral lung V5 significantly. This method is especially helpful while the lung lesion doesn't have a symmetric shape.