bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐E‐T‐659: Quantitative Evaluation of Patient Setup Accuracy of Stereotactic Radiotherapy with the Frameless 6D‐ExacTrac System Using Statistical Modeling
Authors: Keeling V , Jin H , Hossain S , Algan O , Ahmad S , Ali I 
Published: June 2015

Purpose:To evaluate patient setup accuracy and quantify individual and cumulative positioning uncertainties associated with different hardware and software components of the stereotactic radiotherapy (SRS/SRT) with the frameless‐6D‐ExacTrac system.Methods:A statistical model was used to evaluate positioning uncertainties of the different components of SRS/SRT treatment with the BrainLAB 6D‐ExacTrac system using the positioning shifts of 35 patients having cranial lesions (49 total lesions treated in 1, 3, 5 fractions). All these patients were immobilized with rigid head‐and‐neck masks, simulated with BrainLAB‐localizer and planned with iPlan treatment planning system. Infrared imaging (IR) was used initially to setup patients. Then, stereoscopic x‐ray images (XC) were acquired and registered to corresponding digitally‐reconstructed‐radiographs using bony‐anatomy matching to calculate 6D‐translational and rotational shifts. When the shifts were within tolerance (0.7mm and 1°), treatment was initiated. Otherwise corrections were applied and additional x‐rays were acquired (XV) to verify that patient position was within tolerance.Results:The uncertainties from the mask, localizer, IR‐frame, x‐ray imaging, MV and kV isocentricity were quantified individually. Mask uncertainty (Translational: Lateral, Longitudinal, Vertical; Rotational: Pitch, Roll, Yaw) was the largest and varied with patients in the range (−1.05−1.50mm, −5.06–3.57mm, −5.51−3.49mm; −1.40−2.40°, −1.24−1.74°, and −2.43−1.90°) obtained from mean of XC shifts for each patient. Setup uncertainty in IR positioning (0.88,2.12,1.40mm, and 0.64,0.83,0.96°) was extracted from standard‐deviation of XC. Systematic uncertainties of the localizer (−0.03,−0.01,0.03mm, and −0.03,0.00,−0.01°) and frame (0.18,0.25,−1.27mm,−0.32,0.18, and 0.47°) were extracted from means of all XV setups and mean of all XC distributions, respectively. Uncertainties in isocentricity of the MV radiotherapy machine were (0.27,0.24,0.34mm) and kV‐imager (0.15,−0.4,0.21mm).Conclusion:A statistical model was developed to evaluate the individual and cumulative systematic and random uncertainties induced by the different hardware and software components of the 6D‐ExacTrac‐system. The immobilization mask was associated with the largest positioning uncertainty.
SU‐E‐T‐660: Quantitative Fault Testing for Commissioning of Proton Therapy Machines
Authors: Reilly M , Rankine L , Grantham K , Klein E 
Published: June 2015

Purpose:To ensure proper fault testing for the first single room proton therapy machine by establishing a common set of acceptance testing and commissioning parameters with the manufacturer. The following work details the parameters tested and associated results.Methods:Dose rates in service mode were varied to ensure that when the threshold for maximum or minimum MU/min was met, the beam promptly shut off. The flatness parameter was tested by purposely assigning an incorrect secondary scatter, to ensure the beam shut off when detecting a heterogeneous profile. The beam symmetry parameter was tested by altering the steering coil up to 3.0A, thereby forcing the beam to be asymmetric and shut off. Lastly, the quench system was tested by ramping down the magnet to 5% capacity, whereby the quench button was engaged to bring down the magnet current to a safe level.Results:A dose rate increase or decrease in excess of 10% shut the beam off within 5 seconds as observed by the current on a Matrixx ionization chamber array (IBA Dosimetry, Bartlett, TN) A 3.0A change in the beam steering coil introduced a 2% change in the flatness and symmetry profiles with respect to baseline measurements resulting in the beam shutting off within 5 seconds. An incorrect 2nd scatterer introduced a flatness of 4.1% and symmetry of 6.4% which immediately triggered a beam shut off. Finally, the quench system worked as expected during the ramp down procedure.Conclusion:A fault testing plan to check dosimetric faults and the quench system was performed for the first single room proton therapy system. All dosimetric parameters and machine conditions were met to our satisfaction. We propose that the same type of fault testing should be applied to any proton system during commissioning, including scanning beam systems.
SU‐E‐T‐662: Quick and Efficient Daily QA for Compact PBS Proton Therapy Machine
Authors: Patel B , Syh J , Ding X , Syh J , Song X , Freund D , Wu H 
Published: June 2015

Purpose:As proton therapy machines become widespread the need for a quick simple routine daily QA like that for linear accelerators becomes more important. Willis‐Knighton has developed an accurate and efficient daily QA that can be performed in 15 minutes.Methods:A holder for a 2D ionization chamber array (MatriXX PT) was created that is indexed to the couch to allow for quick setup, lasers accuracy with respect to beam isocenter, and couch reproducibility. Image position/reposition was performed to check Isocentricity accuracy by placing BBs on the MatriXX. The couch coordinates are compared to that of commissioning. Laser positions were confirmed with the MatriXX isocenter. After IGRT, three beams were separately delivered according to setup. For the first beam, range shifter was inserted and dose at R90, field size, flatness and symmetry in X and Y direction was measured. R90 was used so any minor changes in the range shifter can be detected. For the open beam, dose at center of SOBP, flatness and symmetry in X and Y direction was measured. Field size was measured in ±X and ±Y direction at FWHM. This is measured so any variation in spot size will be detected. For the third beam additional solid water was added and dose at R50 was measured so that any variation in beam energy will be detected. Basic mechanical and safety checks were also performed.Results:Medical physicists were able to complete the daily QA and reduce the time by half to two‐third from initial daily QA procedure. All the values measured were within tolerance of that of the baseline which was established from water tank and initial MatriXX measurements.Conclusion:The change in daily QA procedure resulted in quick and easy setup and was able to measure all the basic functionality of the proton therapy PBS.
SU‐E‐T‐663: Radiation Properties of a Water‐Equivalent Material Formulated Using the Stoichiometric Analysis Method in Heavy Charged Particle Therapy
Authors: Yohannes I , Hild S , Vasiliniuc S , Langner O , Graeff C , Bert C 
Published: June 2015

Purpose:A material has been designed to be employed as water‐equivalent in particle therapy using a previously established stoichiometric analysis method (SAM). After manufacturing, experimental verification of the material's water‐equivalent path length (WEPL) and analysis of its total inelastic nuclear interaction cross sections for proton beams were performed.Methods:Using the SAM, we optimized the material composed of three base materials, i.e., polyurethane, calcium carbonate and microspheres. From the elemental composition of the compound, electron density, linear attenuation coefficients, particle stopping powers and inelastic nuclear cross sections for protons using data from ICRU 63 were calculated. The calculations were then compared to Hounsfield units (HUs) measured with 350 mAs at 80, 100, 120 and 140 kV and the WEPLs measured with three different ions: proton (106.8 MeV/u), helium (107.93 MeV/u) and carbon (200.3 MeV/u).Results:The material's measured HUs (0.7±3.0 to 2.6±6.2 HU) as well as its calculated relative electron density (1.0001) are in close agreement with water as reference. The WEPLs measured on a 20.00 mm thick target were 20.16±0.12, 20.29±0.12 and 20.38±0.12 mmH2O for proton, helium and carbon ions, respectively. Within measurement uncertainties, these values verified the calculated WEPLs of 20.28 mmH2O (proton), 20.28 mmH2O (helium) and 20.26 mmH2O (carbon). Moreover, the calculated proton inelastic cross sections of the material differed only by 0.89% (100 MeV/u) and 0.01% (200 MeV/u) when compared to water.Conclusion:The SAM is capable of optimizing material with defined properties, e.g., HU, electron density, WEPL and inelastic nuclear interaction cross section for particle therapy. Such material will have a wide range of applications amongst others absolute dosimetry.This work was supported by grant ZIM KF2137107AK4 from the German Federal Ministry for Economic Affairs and Energy.
SU‐E‐T‐666: Radionuclides and Activity of the Patient Apertures Used in a Proton Beam of Wobbling System
Authors: Wang B.Y. , Chen H.H. , Tsai H.Y. , Sheu R.J. 
Published: June 2015

Purpose:To identify the radionuclides and quantify the activity of the patient apertures used in a 190‐MeV proton beam of wobbling system.Methods:A proton beam of wobbling system in the first proton center in Taiwan, Chang Gung Memorial Hospital at Linkou, was used to bombard the patient apertures. The patient aperture was composed of 60.5 % copper, 39.4 % Zinc, 0.05 % iron, 0.05 % lead. A protable high‐purity germanium (HPGe) coaxial detector was used to measure the spectra of the induced nuclides of patient apertures. The analysis of the spectra and the identification of the radionuclides were preliminarily operated by the Nuclide Navigator III Master Library. On the basis of the results by Nuclide Navigator III Master Library, we manually selected the reliable nuclides by the gamma‐ray energies, branching ratio, and half life. In the spectra, we can quantify the activity of radionuclides by the Monte Carlo efficiency transfer method.Results:In this study, the radioisotopes activated in patient apertures by the 190‐MeV proton beam were divided into two categories. The first category is long half‐life radionuclides, such as Co‐56 (half life, 77.3 days). Other radionuclides of Cu‐60, Cu‐61, Cu‐62, Cu‐66, and Zn‐62 have shorter half life. The radionuclide of Cu‐60 had the highest activity. From calculation with the efficiency transfer method, the deviations between the computed results and the measured efficiencies were mostly within 10%.Conclusion:To identify the radionuclides and quantify the activity helps us to estimate proper time intervals for cooling the patient apertures.This study was supported by the grants from the Chang Gung Memorial Hospital (CMRPD1C0682).
SU‐E‐T‐668: Radiosensitizing Effect of Bosutinib On Prostate and Colon Cancers: A Pilot in Vitro Study
Authors: Wang B , Cvetkovic D , Wang C , Chen L , Ma C 
Published: June 2015

Purpose:Recently it has been reported that Bosutinib, a clinical kinase inhibitor, can enhance the tumor cell chemosensitivity by overriding DNA damage checkpoints. However, to the best of our knowledge, there is no report on its effect on cell radiosensitivity in the literature. The objective of the present study is to determine whether Bosutinib has the potential to be used as a radiosensitizer for various cancer cell lines.Methods:In this study, we tested 4 cell lines derived from human prostate (LNCaP, PC‐3, DU‐145) and colon (HT‐29) cancers. The cells were seeded into 12‐well plates 24 hours prior to the radiation treatments. For each cell line, we designed 4 study groups, namely, the control, Bosutinib, radiotherapy, and radiotherapy+Bosutinib groups. We used 6 MV photon beams from a Siemens Artiste accelerator to deliver 2 Gy dose in one fraction to the cells in the radiotherapy and radiotherapy+Bosutinib groups. Immediately after irradiation, the cells in the radiotherapy+Bosutinib group were treated with Bosutinib (1µM) for 3 hours. The cell survival was evaluated through clonogenic assays.Results:The cell survival rates of the LNCaP, PC‐3, DU‐145, and HT‐29 cells were found to be 21%, 92%, 76%, and 93% for the radiotherapy group; 21%, 69%, 67%, and 81% for the radiotherapy+Bosutinib group; and 103%, 107%, 86%, and 102% for the Bosutinib group, respectively. Although synergetic cell killing was not seen for the LNCaP and DU‐145 cell lines in this study, the cell survival data from the clonogenic assay indicated that Bosutinib could enhance the sensitivity of PC‐3 and HT‐29 cells to radiation treatment.Conclusion:Our preliminary results demonstrated the possibility of Bosutinib as a radiosensitizer for certain prostate and colon cancers, which are resistant to radiotherapy. Further studies are warranted to quantify the radiosensitizing effect of Bosutinib.
SU‐E‐T‐669: Radiosurgery Failure for Trigeminal Neuralgia: A Study of Radiographic Spatial Fidelity
Authors: Howe J , Spalding A 
Published: June 2015

Purpose:Management of Trigeminal Neuralgia with radiosurgery is well established, but often met with limited success. Recent advancements in imaging afford improvements in target localization for radiosurgery.Methods:A Trigeminal Neuralgia radiosurgery specific protocol was established for MR enhancement of the trigeminal nerve using a CISS scan with slice spacing of 0.7mm. Computed Tomography simulation was performed using axial slices on a 40 slice CT with slice spacing of 0.6mm. These datasets were registered using a mutual information algorithm and localized in a stereotactic coordinate system. Image registration between the MR and CT was evaluated for each patient by a Medical Physicist to ensure accuracy. The dorsal root entry zone target was defined on the CISS MR by a Neurosurgeon and dose calculations performed on the localized CT. Treatment plans were reviewed and approved by a Radiation Oncologist and Neurosurgeon. Image guided radiosurgery was delivered using positioning tolerance of 0.5mm and 1°. Eight patients with Trigeminal Neuralgia were treated with this protocol.Results:Seven patients reported a favorable response to treatment with average Barrow Neurological Index pain score of four before treatment and one following treatment. Only one patient had a BNI>1 following treatment and review of the treatment plan revealed that the CISS MR was registered to the CT via a low resolution (5mm slice spacing) T2 MR. All other patients had CISS MR registered directly with the localized CT. This patient was retreated 6 months later using direct registration between CISS MR and localized CT and subsequently responded to treatment with a BNI of one.Conclusion:Frameless radiosurgery offers an effective solution to Trigeminal Neuralgia management provided appropriate technology and imaging protocols (utilizing submillimeter imaging) are established and maintained.
SU‐E‐T‐670: Radiotherapy Vault Shielding Evaluation Method for a Flattening Filter‐Free (FFF) Linac‐Practical Considerations and Recommendations
Authors: Mihailidis D 
Published: June 2015

Purpose:To date, there isn't formal approach for flattening filter‐free (FFF) linac vault shielding evaluation, thus, we propose an extension to NCRP#151 to accommodate the recent large number of FFF linac installations.Methods and Materials: We extended the approach in NCRP#151 to design two Truebeam vaults in our new cancer center for hypofractionated treatments. Monte Carlo calculations have characterized primary, scattered, leakage and neutron radiations from FFF‐modes. These calculations have shown that: a) FFF primary beam is softer on the central‐axis compared to flattening filtered (FF), b) the lateral dose profile is peaked on the central axis and less integral target current is required to generate the same tumor dose with the FF beam. Thus, the TVLs for FFF mode are smaller than those of the FF mode and the scatter functions of the FF mode (NCRP#151) may not be appropriate for FFF‐mode, c) the neutron source strength and fluence for 18X‐FFF is smaller than 18X‐FF, but it is not of a concern here, no 18X‐FFF‐mode is available on the linac under investigation.Results:These barrier thickness are smaller (12% reduction on the average) than those computed for conventional FF mode with same realistic primary workload since, the primary TVLs used here are smaller and the WL is smaller than the conventional (almost half reduced), keeping the TADR in tolerance.Conclusions:A comprehensive method for shielding barrier calculations based on dedicated data for FFF‐mode linacs is highly desired. Meanwhile, we provide an extension to NCRP#151 to accommodate the shielding design of such installations. It is also shown that if a vault is already designed for IMRT/VMAT and SABR hypofractionated treatments with FFF‐mode linac, the vault can also be used for a FFF mode linac replacement, leaving some leeway for slightly higher workload on the FFF linac.
SU‐E‐T‐671: Range‐Modulation Effects of Carbon Ion Beams in Lung Tissue
Authors: Witt M , Weber U , Simeonov Y , Zink K 
Published: June 2015

Purpose:When particles traversing inhomogeneous materials like lung they show a characteristic range modulation which cannot be observed in homogeneous materials. It is possible to describe the range modulation by a convolution of an unperturbed Bragg‐Curve and a normal distribution. The sigma of the normal distribution is a parameter for the strength of the modulation effect. A new material parameter (modulation power, P_mod) is introduced which is independent of the material thickness. It is defined as the square of sigma divided by the mean water equivalent thickness of the target (µ).Methods:The modulation power of lung tissue was determined by actual Bragg‐peak measurements after traversing an ex‐vivo porcine lung and by Monte‐Carlo simulations with micro‐CT data of human lung tissue. The determined modulation powers were used to show the effect of range modulation effects in a simplified treatment situation. A four centimeter spread‐out Bragg‐peak after traversing eight centimeter of lung tissue was simulated in FLUKA. The SOBP with and without consideration of range modulation effects were compared.Results:As well in the measurements as in the MC simulations range modulation effects of lung tissue were observed. The determined modulation powers showed a great range from 0.05 mm, in the micro‐CT data, to 0.7 mm in the lung measurements. The SOBP comparison showed that range modulation effects Result in over‐ and underdosages at the distal and proximal edge of the SOBP. In the investigated case, the last 0.5 cm of the SOBP showed an underdosage of up to 50% at the distal edge, while 0.5 cm distal to the SOBP an overdosage of up to 50% was observed.Conclusion:Range modulation effects occur in inhomogeneous materials like lung. These modulation effects may Result in clinically relevant over‐ and underdosages but are currently not considered in commercially available treatment planning systems.
SU‐E‐T‐672: Real‐Time In Vivo Dosimeters Using LiPCDA and Optical Fibers
Authors: Rink A , Croteau A , Caron S , Mermut O , Jaffray DA 
Published: June 2015

Purpose:To investigate dosimeter prototypes made with lithium pentacosa‐10,12‐diynoate (LiPCDA, the material used in GafChromic EBT films) and optical fibers for their suitability in real‐time in vivo measurements.Methods:The prototypes, made with 500 µm plastic optical fibers and 8.5 µm thickness of LiPCDA at fiber tip, were irradiated with a 6 MV beam. To investigate the efficacy of pre‐irradiation calibration, the probes were irradiated to 2 Gy twice, with 5 minutes in between. Net optical density values (netOD) around the main absorbance peak were compared, and effect of correcting second measurement by the first was assessed. Ageing was assessed by irradiating two prototypes to 2 Gy and comparing the netOD to that obtained for 15 prototypes from the same batch 12–14 months earlier. To measure angular dependence, the probes were pre‐irradiated with beam perpendicular to fiber axis and then, 5 minutes later either perpendicular or parallel to fiber axes. The thickness‐corrected netOD measurements were compared.Results:Standard deviation of netOD for probes of the same batch was measured to be 5–6%. When netOD was corrected for material thickness by using results from the first irradiation, the standard deviation decreased to 1.3%. This was comparable to the uncertainty in measurements observed with a single probe and is attributed to variations in light output, spectrometer noise and splitter‐to‐probe connection variations. Comparison of netOD values obtained a year apart failed to illustrate statistically significant decrease in sensitivity due to ageing (0.38 ± 0.03 and 0.3656 ± 0.0003). NetOD measured with MV beam parallel to fiber was within error of netOD measured with MV beam perpendicular to fiber.Conclusion:Current prototype construction allows for shelf life of at least one year. With material thickness corrected for, the prototypes can measure dose with an uncertainty below 2% at a given energy and dose rate.This work has been funded by the Ontario Centres of Excellence Market Readiness grant. The authors have no conflict of interest to declare.
SU‐E‐T‐674: Relationship Between Conformity Indices and Treatment Characteristics in Cone Based Linac Stereotactic Radiosurgery
Authors: Li K 
Published: June 2015

Purpose:To investigate the correlation between conformity indices and dose prescription methodologies for LINAC based stereotactic surgery (SRS) cone plans.Methods:A vestibular schwannoma Linac based SRS cone plan was selected for this study. The target volume was 0.49cc and its equivalent sphere diameter is 1.0cm. Single 360 degree ARC Plans with different sizes of cones were done in Eclipse Cone planning System from Varian Medical. The plans were prescribed to satisfy to be normalized to 50% isodose line, 80% isodose line, 100% isodose line covering 95% of the target volume, at target mean dose and target minimum dose. The cones were select to be 10mm, 12mm, 14mm, 16mm, 18mm, 20mm, and 22mm in diameter. The indices for this study were conformity index(CI), which is defined to be the ratio between prescription isodose volume (PIV) and target volume (TV), and integrated conformity index (ICI), which is defined to be (TVpiv)2/(PIVxTV), where TVpiv is the intersection between PIV and TV.Results:When the plans were normalized to 50% of maximum dose, 80% of maximum dose, 100% isodose line covering 95% of the target volume, at target mean dose and target minimum dose, the corresponding values of ICI ranged from 0.45 to 0.04, 0.68 to 0.08, 0.58 to 0.54, 0.65 to 0.58, and 0.37 to 0.26; and the corresponding values of CI ranged from 2.2 to 22.8, 0.9 to 11.4, 1.5 to 1.7, 0.7 to 0.5, and 2.7 to 3.9.Conclusion:The values of indices used to describe SRS plans vary with different prescription conditions for single 360 degree ARC cone plans. For plans satisfied 100 % isodose covering 95% of target volume, the values of CI were between 1 and 2. A dynamic sensitive analysis system should be developed to correlate the plan evaluation index such as CI and ICI with clinical parameters.