bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐F‐T‐453: Improved Head and Neck SBRT Treatment Planning Using PlanIQ
Authors: Wang H , Wang C , Phan J , Tung S , Chi P 
Published: July 2016

Purpose:Treatment planning for Head and Neck(HN) re‐irradiation is a challenge because of ablative doses to target volume and strict critical structure constraints. PlanIQ(Sun Nuclear Corporation) can assess the feasibility of clinical goals and quantitatively measure plan quality. Here, we assess whether incorporation of PlanIQ in our SBRT treatment planning process can improve plan quality and planning efficiency.Methods:From 2013–2015, 35 patients (29 retrospective, 6 prospective) with recurrent HN tumors were treated with SBRT using VMAT treatment plans. The median prescription dose was 45 Gy in 5 fractions. We retrospectively reviewed the treatment plans and physician directives of our first 29 patients and generated score functions of the dosimetric goals used in our practice and obtained a baseline histogram. We then re‐optimized 12 plans that had potential to further reduce organs‐at‐risk (OAR) doses according to PlanIQ feasibility DVH and plan quality analysis and compared them to the original plans. We applied our new PlanIQ‐assisted planning process for our 6 most recently treated patients and evaluated the plan quality and planning efficiency.Results:The mean plan quality metric(PQM) and feasibility adjusted PQM(APQM) scores of our initial 29 treatment plans were 77.1±13.1 and 88.7±11.9, respectively (0–100 scale). The PQM and APQM scores for the 12 optimized plans improved from 75.9±11.0 and 85.1±10.2 to 80.7±9.3 and 90.2±8.0, respectively (p<0.005). Using our newly developed PlanIQ‐assisted planning process, the PQM and APQM scores for the 6 most recently treated patients were 93.6±6.5 and 99.1±0.6, respectively. The planning goals were more straightforward to minimize OAR doses during optimization, thus less planning and revision time were used than before.Conclusion:PlanIQ has the potential to provide achievable planning goals and also improve plan quality and planning efficiency.
SU‐F‐T‐454: Dose‐Mass‐Histogram Sensitivity to Anatomical Changes During Radiotherapy for HNSCC
Authors: De Ornelas‐Couto M , Bossart E , Elsayyad N , Samuels M , Takita C , Mihaylov I 
Published: July 2016

Purpose:To determine the sensitivity of dose‐mass‐histogram (DMH) due to anatomical changes of head‐and‐neck squamous cell carcinoma (HNSCC) radiotherapy (RT).Methods:Eight patients undergoing RT treatment for HNSCC were scanned during the third and sixth week of RT. These second (CT2) and third (CT3) CTs were co‐registered to the planning CT (CT1). Contours were propagated via deformable registration from CT1 and doses were re‐calculated. DMHs were extracted for each CT set. DMH sensitivity was assessed by dose‐mass indices (DMIs), which represent the dose delivered to a certain mass of and anatomical structure. DMIs included: dose to 98%, 95% and 2% of the target masses (PTV1, PTV2, and PTV3) and organs‐at‐risk (OARs): cord DMI2%, brainstem DMI2%, left_ and right_parotid DMI2% and DMI50%, and mandible DMI2%. A two‐tailed paired t‐test was used to compare changes to DMIs in CT2 and CT3 with respect to CT1 (CT2/CT1 and CT3/CT1).Results:Changes to DMHs were found for all OARs and PTVs, but they were significant only for the PTVs. Maximum dose to PTVs increased significantly for CT2/CT1 in all three PTVs, but CT3/CT1 changes were only significantly different for PTV1 and PTV2. Dose coverage to the three PTVs was also significantly different, DMI98% was lower for both CT2/CT1 and CT3/CT1. DMI95% was significantly lower for PTV1 for CT2/CT1, PTV2 for CT2/CT1 and CT3/CT1, and PTV3 for CT3/CT1.Conclusion:Changes in anatomy significantly change dose‐mass coverage for the planning targets, making it necessary to re‐plan in order to maintain the therapeutic goals. Maximum dose to the PTVs increase significantly as RT progresses, which may not be problematic as long as the high dose remains in the gross tumor volume. Doses to OARs were minimally affected and the differences were not significant.
SU‐F‐T‐455: Is Contouring the Whole Breast Necessary for Two‐Field 3D Breast Planning?
Authors: Desai A , Ku Eric , Fang D , Lawrence C , Iannuzzi C , Shi C 
Published: July 2016

Purpose:To investigate the effect of contouring the whole breast on reducing the radiation dose to the heart and affected lung in tangential field‐in‐field 3D breast planning. We hypothesize that contouring the whole breast will simplify the plan normalization process, reduce dose to critical structures, while maintaining treatment plan quality and consistency.Methods:Twenty previously treated breast cancer patients using tangential field‐in‐field 3D planning technique were randomly selected. The affected breast was contoured following the RTOG breast atlas guideline. Breast PTV was created by shrinking 5 mm from the breast contour. The same plan has been pasted to the new contour and normalized to 95% of the Breast PTV receiving the prescribed isodose line. Lung V20 Gy% and Heart V25 Gy% were the primary study endpoints. Homogeneity Index (HI) and Conformity Index (CI) were calculated based on the following equations. HI= Dmax/ D95 and Nakamura's Conformity Index= PIV/TVPIV × TV/TVPIV.Results:The average CI for previous plans was 1.68 vs. 1.66 for the new hybrid plan: both plans were conformal to the breast with similar quality. The HI for both the previous and the new hybrid plan was 1.24. Lung V 20% slightly increased from 4.27% to 4.82%. Heart V 25% for LT breast patients slightly decreased from 0.38% to 0.29%. Heart V 25% for RT breast patients was close to zero in both cases.Conclusion:With similar conformal and homogeneity indices for the plan quality, by contouring the whole breast following RTOG breast atlas guideline will simplify the planning process. The study showed that contouring the whole breast for patients with left‐sided breast cancer reduced the heart V 25%, although not significantly, while maintaining the CI and HI. There was no measurable gain seen with whole breast contour for right‐sided breast cancer patients.
SU‐F‐T‐461: Dosimetric Evaluation of Indigenous Farmer Type Chamber FAR65‐ GB for Reference Dosimetry of FFF MV Photon Beam
Authors: Patwe P , Mhatre V , Dandekar P 
Published: July 2016

Purpose:Indigenous Farmer type chamber FAR 65 GB is a reference class 0.6 cc ion chamber. It can be used for dosimetric evaluation of photon and high energy electron beams. We studied dosimetric characteristics of the chamber for 6MV and 10MV Flattening filter free FFF photon beams available on trueBEAM STx Linac.Methods:The study was carried out on trueBEAM STx Linac having 6 and 10 MV FFF photon beam with maximum dose rate 1400 and 2400 MU per min respectively. The dosimetric device to be evaluated is Rosalina Instruments FAR 65‐GB Ion Chamber with active volume 0.65 cc, total active length 23.1cm, inner diameter of cylinder 6.2mm, wall thickness 0.4mm, inner electrode diameter 1mm. Inner and outer electrodes are made from Aluminium 2.7 gm per cc and graphite 1.82 gm per cc respectively. The ion chamber was placed along central axis of beam at 10cm depth and irradiated for 10cm × 10cm field size at SAD of 100 cm in plastic phantom. We studied Precision, Dose Linearity, Dose Rate dependence, directional dependence, Recombination effect. Recombination effect was determined using standard two‐voltage method.Results:1. Measurements were reproducible std deviation of 0.0105 and type A uncertainty 0.003265 under same set of reference conditions 2. Chamber exhibit dose linearity over a wider dose range. 3. Chamber shows dose rate independence for all available dose rate range. 4. Response of chamber with the angle of incidence of radiation is constant. 5. Recombination correction factors were 1.01848 and 1.02537 for dose rate 1400 and 2400 MU per min resp.Conclusion:Our study reveals that the chamber is prone to saturation effect at dose rate of 2400 MU per min. FAR 65‐GB can be used for reference dosimetry of FFF MV photon beam with proper calculation of recombination effect.
SU‐F‐T‐465: Two Years of Radiotherapy Treatments Analyzed Through MLC Log Files
Authors: Defoor D , Kabat C , Papanikolaou N , Stathakis S 
Published: July 2016

Purpose:To present treatment statistics of a Varian Novalis Tx using more than 90,000 Varian Dynalog files collected over the past 2 years.Methods:Varian Dynalog files are recorded for every patient treated on our Varian Novalis Tx. The files are collected and analyzed daily to check interfraction agreement of treatment deliveries. This is accomplished by creating fluence maps from the data contained in the Dynalog files. From the Dynalog files we have also compiled statistics for treatment delivery times, MLC errors, gantry errors and collimator errors.Results:The mean treatment time for VMAT patients was 153 ± 86 seconds while the mean treatment time for step & shoot was 256 ± 149 seconds. Patient's treatment times showed a variation of 0.4% over there treatment course for VMAT and 0.5% for step & shoot. The average field sizes were 40 cm2 and 26 cm2 for VMAT and step & shoot respectively. VMAT beams contained and average overall leaf travel of 34.17 meters and step & shoot beams averaged less than half of that at 15.93 meters. When comparing planned and delivered fluence maps generated using the Dynalog files VMAT plans showed an average gamma passing percentage of 99.85 ± 0.47. Step & shoot plans showed an average gamma passing percentage of 97.04 ± 0.04. 5.3% of beams contained an MLC error greater than 1 mm and 2.4% had an error greater than 2mm. The mean gantry speed for VMAT plans was 1.01 degrees/s with a maximum of 6.5 degrees/s.Conclusion:Varian Dynalog files are useful for monitoring machine performance treatment parameters. The Dynalog files have shown that the performance of the Novalis Tx is consistent over the course of a patients treatment with only slight variations in patient treatment times and a low rate of MLC errors.
SU‐F‐T‐466: An Enhanced Daily Quality Assurance Process for a Six Degrees of Freedom Robotic Table
Authors: Kremmel E , Doyle L , Yu Y , Harrison A 
Published: July 2016

Purpose:A Varian PerfectPitch six degrees of freedom robotic table necessitates daily quality assurance (QA). Therapists were credentialed for this QA procedure which was easily incorporated into the existing daily warmup process. This procedure adds depth to TG‐142 requirements without additional morning time costs.Methods:This PerfectPitch table QA introduces a consistent rotation of the QUASAR™ Penta‐Guide phantom and requires automatic table corrections through image fusions. Rotational offsets are generated by inserting a platform tool under a specified corner of the phantom; then a conebeamCT is performed. This conebeamCT image is fused with a planned reference CT image set and the table is auto‐adjusted to correct for induced translational and rotational offsets. After executing table shifts, a second conebeamCT verifies the table movement and the phantom's return to isocenter.Results:Pre‐shift and post‐shift table corrections were recorded daily. It was discovered that due to slight variations in the setup, it took three performances of the QA for each therapist to have consistent induced rotations. Four therapists performed this QA and after the initial training period, the inter‐user variability was minimal. Consistency of the induced rotation was evaluated by the variation of the pre‐shift table corrections. Excluding the first three attempts of each therapist, the pre‐shift table correction standard deviations were ≤ 0.67mm for the translational axes and ≤ 0.49° for the rotational axes. Accuracy of the automatic table movement was confirmed by the post‐shift table corrections. The average post‐shift table corrections for the translational axes were ≤ 0.15mm and for the rotational axes were ≤ 0.42°. Using our clinic's existing table corrections tolerance of <1mm and <0.5°, these results were deemed acceptable.Conclusion:Therapists successfully and rapidly adopted daily QA procedures using the PerfectPitch table; automated rotational robotic table motions were confirmed through image fusions. This procedure enhances existing TG‐142 recommendations.
SU‐F‐T‐467: A Cross‐Checking Approach for Dosimetric Verification of Beam‐ Matched Elekta Linear Accelerators
Authors: Zheng Y , Yuan J , Geis P , Colussi V , Machtay M , Ellis R , Wessels B 
Published: July 2016

Purpose:To verify the similarity of the dosimetric characteristics between two Elekta linear accelerators (linacs) in order to treat patients interchangeably on these two machines without re‐planning.Methods:To investigate the viability of matching the 6 MV flattened beam on an existing linac (Elekta Synergy with Agility head) with a recently installed new linca (Elekta Versa HD), percent depth doses (PDD), flatness and symmetry output factors were compared for both machines. To validate the beam matching among machines, we carried out two approaches to cross‐check the dosimetrical equivalence: 1) the prior treatment plans were re‐computed based on the newly built Versa HD treatment planning system (TPS) model without changing the beam control points; 2) The same plans were delivered on both machines and the radiation dose measurements on a MapCheck2 were compared with TPS calculations. Three VMAT plans (Head and neck, lung, and prostate) were used in the study.Results:The difference between the PDDs for 10×10 cm2 field at all depths was less than 0.8%. The difference of flatness and symmetry for 30×30 cm2 field was less than 0.8%, and the measured output factors varies by less than 1% for each field size ranging from 2×2 cm2 to 40×40 cm2. For the same plans, the maximum difference of the two calculated dose distributions is 2% of prescription. For the QA measurements, the gamma index passing rates were above 99% for 3%/3mm criteria with 10% threshold for all three clinical plans.Conclusion:A beam modality matching between two Elekta linacs is demonstrated with a cross‐checking approach.
SU‐F‐T‐468: Efficient Scanning Data Analysis for TomoTherapy
Authors: Sintay B , Pearman K , Maurer J , Liu H , Hayes T , Wiant D 
Published: July 2016

Purpose:The standard TomoTherapy 2D scanning system requires manual analysis using spreadsheets or similar software. Manual analysis is time consuming and does not allow efficient use of the medical physicist or timely results that may indicate issues during the acquisition of data. The purpose of this study is to determine if an in‐house solution can provide timely analysis of TomoTherapy scan data.Methods:A custom MATLAB program utilizing a streamlined graphical interface was developed to interpret the native scanning data acquired by the TomoTherapy Electrometer Measurement System (TEMS). The gold beam data provided by the manufacturer was used as a baseline for the acquired data. Two separate sets of scan data were used including longitudinal, transverse, and percent depth dose (PDD). The scan data were compared visually in an overlay and analytically for each beam width using the full width half max (FWHM) for longitudinal profiles and difference inside the field core for the transverse profiles as recommended by TG‐148. A plot of the PDD percent error at each point along the curve was generated to show agreement. The time to analysis was measured on a laptop running an Intel i5 processor with 8GB of RAM.Results:The software program required on average less than 5 seconds to load and analyze the results. No conversion or reformatting of the data was required. This allowed real‐time visualization of the comparison to the gold beam data as well as the parameters recommended by TG‐148. The average percent difference was 0.3% for the longitudinal profiles and 0.1% for the transverse profiles. All PDD data was less than 1% different beyond dmax.Conclusion:We have developed a tool to analyze TomoTherapy scan data in real‐time. This allows an efficient method to perform beam commissioning, annual QA, and adjust the beam parameters if necessary.
SU‐F‐T‐470: Implementation of a Daily Quality Assurance Phantom for Six Degrees‐Of‐Freedom Couch Testing
Authors: Gaballa H , O'Brien M , Riegel A , Jamshidi A , Klein E 
Published: July 2016

Purpose:To develop a daily quality assurance (QA) device that can test the 6DoF (degrees of freedom) couch repositioning accuracy, prior to SBRT treatment deliveries, with an accuracy of ±0.3 degrees and ±0.3 mm.Methods:A daily QA phantom is designed with a focus on the derived center of projections of its markers, rather than tracking its individual markers one at a time. This approach can be the most favorable to address the intended machining accuracy of the QA phantom and the CBCT spatial resolution limitations, primarily 1 mm min slice thickness, simultaneously. With the current design, ±0.1 mm congruence of the resultant center of gravity of the markers with reference CT (0.6 mm minimum slice thickness) vs CBCT (1.0 mm minimum slice thickness) can be achieved. If successful, the QA device should be qualified to test 6DoF couch performance with a gauged accuracy of ±0.3 degrees/±0.3 mm. Testing is performed for the Varian True Beam 2.0 6DoF system.Results:Once the QA phantom is constructed and tested, agreement of the center of gravity of the reference CT scan and the CBCT scan of ±0.1 mm is achieved. This has translated into a consistent 3D‐3D match on the treatment machine, CT vs CBCT, with a repetitive ±0.1 mm variation, thus exceeding our expectations. We have deployed the phantom for daily QA on one of our accelerators, and found that the QA time has increased by only 10 minutes.Conclusion:A 6DoF phantom has been designed (patent pending) and built with a realistic work flow in mind where the daily couch accuracy QA checks taking less than 10 minutes. Current developments include integration with the Varian's Machine Performance Check consistency module.
SU‐F‐T‐473: Evaluation of Off‐Axis And Peripheral Dose Using Different Detectors
Authors: Ganesan B , Prakasarao A , Palraj T , Rai R , Singaravelu G 
Published: July 2016

Purpose:In radiation therapy, measurement of off‐axis and peripheral dose is a tedious task. The dose distribution along the beam central axis give only part of the information required for an accurate dose description inside the patient. Dose distributions in 2‐D and 3‐D are determined with central axis data in conjunction with off‐axis dose profiles. Combining a central axis dose distribution with off‐axis data results in volume dose matrix that provides 2‐D and 3‐D information on dose distribution. By considering the importance of these two parameters this study investigates and compares the off axis and peripheral dose measurement using Ionization chamber, MOSFET, Radiochromic film and EDR2 film.Methods:In the measurement of off‐axis and peripheral doses 0.6cc farmer type chamber, EDR‐2 film, MD‐55 radiochromic film and MOSFET detectors were used for both 6MV and 15MV beams. The off‐axis and peripheral dose was measured at every 1 cm interval by changing the position of the couch without disturbing the other experimental setup in particular, the phantom with detector position.Results:Readings were obtained for both 6MV and 15MV photon beams at SSD technique for various field size using MOSFET, Ionization chamber and Radiochromic film. The results shows the percentage difference between various detectors for various field sizes. For Peripheral dose measurement were taken from the edge of the field size and for off axis it is measured form central axis dose.Conclusion:In conclusion, our study shows that no detector is ideal and only a comparison between different detectors highlights the weaknesses of each detector. MOSFET provides adequate dose assessment in off‐axis and peripheral regions in 6MV and 15MV photon beams. Film dosimetry in general a convenient method to generate one‐ and two‐dimensional dose distributions. The result of this indicates that MOSFET is flexible tool for relative dosimetry as films.
SU‐F‐T‐474: Evaluation of Dose Perturbation, Temperature and Sensitivity Variation With Accumulated Dose of MOSFET Detector
Authors: Ganesan B , Prakasarao A , Palraj T , Rai R , Singaravelu G 
Published: July 2016

Purpose:The use of mega voltage gamma and x‐ray sources with their skin sparring qualities in radiation therapy has been a boon in relieving patient discomfort and allowing high tumor doses to be given with fewer restrictions due to radiation effects in the skin. However, high doses given to deep tumors may require careful consideration of dose distribution in the buildup region in order to avoid irreparable damage to the skin.Methods:To measure the perturbation of MOSFET detector in Co60,6MV and 15MV the detector was placed on the surface of the phantom covered with the brass build up cap. To measure the effect of temperature the MOSFET detector was kept on the surface of hot water polythene container and the radiation was delivere. In order to measure the sensitivity variation with accumulated dose Measurements were taken by delivering the dose of 200 cGy to MOSFET until the MOSFET absorbed dose comes to 20,000 cGyResults:the Measurement was performed by positioning the bare MOSFET and MOSFET with brass build up cap on the top surface of the solid water phantom for various field sizes in order to find whether there is any attenuation caused in the dose distribution. The response of MOSFET was monitored for temperature ranging from 42 degree C to 22 degree C. The integrated dose dependence of MOSFET dosimeter sensitivity over different energy is not well characterized. This work investigates the dual‐bias MOSFET dosimeter sensitivity response to 6 MV and 15 MV beams.Conclusion:From this study it is observed that unlike diode, bare MOSFET does not perturb the radiation field.. It is observed that the build‐up influences the temperature dependency of MOSFET and causes some uncertainty in the readings. In the case of sensitivity variation with accumulated dose MOSFET showed higher sensitivity with dose accumulation for both the energies.
SU‐F‐T‐484: Initial Evaluation of a Novel 6D QA Phantom (HexaCheck) for Daily 6D Couch Correction Assessment
Authors: Roring JE , Stanley D , Papanikolaou N , Gutierrez AN 
Published: July 2016

Purpose:Treatment couches with 6D correction capabilities have become a regular part of IGRT. While 6D couches have been shown to function mechanically well, phantoms for daily angular QA accuracy assessment have yet to be commercially available. Standard Imaging™ has developed a phantom designed for daily verification of pitch, roll, and yaw corrections. In this study, the mechanical integrity, reproducibility, and daily 6D correction stability of the phantom using both volumetric (Elekta− XVI kV‐CBCT) and orthogonal kV (Brainlab ExacTrac) imaging was evaluated.Methods:The HexaCheck is a rotating base that works in conjunction with the MIMI imaging phantom. The MIMI is placed inside the HexaCheck and secured to prevent motion. The HexaCheck has screws in each rotational direction (pitch, roll, and yaw) along with a spring‐loaded peg to lock each direction firmly. When a peg is released, the HexaCheck rotates 2.5° solely in that direction. Mechanical integrity was assessed using a level with 0.05° precision. For daily 6D corrections, a high resolution reference CT (0.59 × 0.59 × 1.25 mm3) of the HexaCheck was acquired. Ten (n=10) independent, daily acquisitions using both the ExacTrac with the 6D Brainlab™ couch and the Elekta XVI kV‐CBCT with the HexaPOD™ couch were acquired to test detection and positioning accuracy.Results:Physical measurements show that the HexaCheck rotations for pitch, roll, and yaw were 2.43±0.05 deg, 2.50±0.05 deg, and 2.62±0.05 deg, respectively. Maximum mean values for the imaging registration accuracy were 0.2° and 0.3° for ExacTrac and XVI, respectively. Maximum mean values for the couch positioning accuracy were 0.1° and 0.2° for the Brainlab couch and HexaPOD, respectively.Conclusion:The HexaCheck performance yields consistent results for daily testing in all three rotational directions using both 2D and 3D imaging modalities and also appears to be a simple method for daily 3D rotational testing.