bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐E‐J‐176: Further Investigation of Improved Reconstruction Algorithm for Tomosynthesis Plus Few Discrete Projections: Noisy Projections and TV Filtration
Authors: Wei Y , McKee M , Baydush A 
Published: November 2011

Purpose: Investigations over the past few years have demonstrated some of the benefits and shortfalls of tomosynthesis in radiation therapy for patient positioning or dose tracking. Tomosynthesis generates excellent image quality in one reconstruction plane; however, there is a loss of edge and frequency information in the additional planes due to the spatial incompleteness of the projection data. In our previous study, we demonstrated improved results from a new discrete frequency interpolation technique (DFIT), which is used to incorporate tomosynthesis limited arc projection data and three additional “filling” projections. Here, we continue investigation into DFIT by studying noisy projections for the data and incorporation of total variation (TV) noise reduction into the reconstruction processing. Methods: For this investigation, we simulated a Shepp‐Logan phantom to generate 93 parallel beam projections with ±5% uniform random noise. 90 of these projections were over a 90‐degree tomosynthetic arc. The remaining three projections were evenly spaced (i.e. 22.5, 45, and 67.5 degrees from the end of the arc) to help “fill in” the incomplete data. DFIT+TV was used to reconstruct images by interpolating frequency values into the gaps of the Fourier spectrum, inverse Fourier transforming from frequency to image space, adding the resultant image to a filtered backprojection (FBP) image, and finally applying a TV noise reduction step. Results: The images by traditional FBP, DFIT, FBP+TV and DFIT+TV are compared visually and using horizontal and vertical line profile plots. Additionally, contrast results are examined. The DFIT+TV images show improved edge delineation in the usual tomosynthesis “blurred” direction and improved reconstructed contrast. Conclusions: The addition of limited “filling” discrete projections and DFIT+TV can be used to improve the reconstruction accuracy and quality of short arc imaging. Future work will study DFIT+TV in the cone beam geometry.Research supported by Nucletron, B.V.
SU‐E‐J‐177: Improved Reconstruction Algorithm for Tomosynthesis Plus Few Discrete Projections
Authors: Wei Y , McKee M , Baydush A 
Published: November 2011

Purpose: Investigations over the past few years have demonstrated some of the benefits and shortfalls of tomosynthesis in radiation therapy for patient positioning or dose tracking. Tomosynthesis generates excellent image quality in one reconstruction plane; however, there is a loss of edge and frequency information in the additional planes due to the spatial incompleteness of the projection data. In this study, we investigate the results of a new discrete frequency interpolation technique (DFIT), which is used to incorporate tomosynthesis limited arc projection data and three additional “filling” projections. Methods: For the initial investigations, we simulated a Shepp‐Logan phantom with parallel beam geometry to generate 93 projections. 90 of these projections were over a tomosynthetic arc at one projection per degree. The remaining three projections were generated to fill in the next 90 degrees evenly (i.e. 22.5, 45, and 67.5 degrees from the end of the arc) to help “fill in” the incomplete data. Simple filtered backprojection (FBP) results show no improvement as FBP is designed for uniform distribution of projections. Per the projection slice theorem, the tomosynthesis data fills in a portion of the frequency plane. The remaining sparsely sampled area of the frequency plane is filled using linear interpolation from the end arc projections and the 3 discrete projections. The DFIT image is the sum of the FBP image and the inverse Fourier transform of the interpolated frequencies Results: The images by traditional FBP and DFIT are compared visually and using line profile plots. Additionally, contrast results are examined. The DFIT images show improved edge delineation in the usual tomosynthesis “blurred” direction and improves reconstructed contrast. Conclusions: The addition of limited “filling” discrete projections and DFIT can be used to improve the reconstruction accuracy and quality of short arc imaging.Research supported by Nucletron, B.V.
SU‐E‐T‐13: Radiobiological Model for Evaluation of Targeted Radionuclide Therapeutic Potential in Metastases Control
Authors: Martin‐Landrove R 
Published: November 2011

Purpose: To provide a rabiobiological evaluation tool based on a mathematical model for control of metastases during treatment with the use of FDG beta emissions as therapeutic agent. Methods: Analytical and numerical solution of a nonlinear set of equations in order to describe the interaction between beta radiation and clonogenic transformed cells which are part of a primary tumor and related metastases. Under the consideration that beta emissions in this particular case can be taken as high LET radiation, the critical time and fraction number for local minima in the transformed cell population and can be found in closed form. Results: This theory can explain the observed behavior for the primary tumor and particularly for metastases in a mice‐melanoma experimental model, where 3 out of 7 of the treated animals showed no metastases. This result suggests the possibility of a fractionation scheme for total dose which can produce the same effect when repeated intravenous inoculations are provided at the proper critical time intervals. Conclusions: For metastases control with radionuclides, which are beta emitters like FDG as therapeutic agents, a treatment planning and follow up is possible from a quantitative point of view using a radiobiological kinetic model based on DNA damage mechanisms.Funding was provided by the School of Physics, Faculty of Science and Consejo de Desarrollo Científico y Humanístico, Universidad Central de Venezuela and Física Médica C. A.
SU‐E‐T‐20: Differential Modulation of Antioxidant Defense System in Various Organs of Balb/c Mice by Whole Body Exposure to Low‐Dose Gamma Radiation
Authors: Pathak CM , Avti PK , Khanduja KL 
Published: November 2011

Purpose: To evaluate the effect of low‐dose (< 50 cGy) whole body gamma irradiation on antioxidant defense system enzymes in the liver, lung and kidney of Balb/c mice at various post‐irradiation intervals. We examined the critical level of radiation dose and the degree to which these changes remain affected in these organs after irradiation. Methods: Young male Balb/c mice (5–6 wks), were divided into irradiated and non‐irradiated groups. Whole body irradiation was done with gamma rays from a, 60</sup> Cobalt source at doses of 10, 25 and 50 cGy (48.78 cGy/min). Lipid peroxidation and antioxidant defense enzymes (reduced glutathione, superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase) were measured in liver, lung and kidney at 4, 12 and 24 hr after irradiation.Results: Lipid peroxidation increased by 1.38, 2.0 and 1.33 folds in lung, liver and kidney respectively at 12 hrs after exposure to 25 cGy. Reduced glutathione increased significantly in all these organs at 12 hrs after exposure of the animals at these doses as compared to control. Superoxide dismutase activity increased in liver and kidney up to 1.37 folds at 12 hrs of exposure at these doses. The antioxidant enzyme activities of catalase, glutathione peroxidase and glutathione reductase also increased between 1.1 and 1.3 folds in kidney and liver of mice at these doses. Interestingly, the activities of these enzymes remained unaltered in the lung after exposure of the animals at different doses Conclusions: Low‐dose whole body irradiation differentially modulates the antioxidant defense system in liver, lungs and kidneys of mice which may be due to variable sensitivities in activation of the related genes in these organs. The induction of endogenous glutathione immediately after exposure to low‐dose gamma irradiation, may be beneficial in protecting the cells from the reactive oxygen species (ROS) induced oxidative stress in various ROS‐related diseasesFunds for conducting this project were provided by Director, Post Graduate Institute of Medical Education and Research, Chandigarh, India.
SU‐E‐T‐46: Evaluation of Different Cancer Risk Models on Second Cancer Risk Calculation for Conventional Breast Cancer Radiation Therapy
Authors: Joosten A , Bochud F , Matzinger O , Moeckli R 
Published: November 2011

Purpose: To determine the influence of different cancer risk models on second cancer risk when these models are applied to full‐body dose distribution of two conventional breast treatments computed by Monte Carlo. Methods: Two conventional breast treatments (2‐fields and 4‐fields) were simulated in a full‐body voxelised anthropomorphic phantom with a Monte Carlo model of the Siemens Primus 6MV linac. Dose distribution for each organ at risk was extracted. Linear risk models from the ICRP 103 and BEIR VII were applied to the average dose of specific organs. Both cancer incidence risk and cancer mortality risk were determined for the BEIR calculations. Risks were determined when considering all organs together and out‐of‐field organs exclusively. In addition to these linear models, cancer risks were determined with non‐linear dose risk models applied to the full body dose distribution yielding “Organ Equivalent Doses” (OED). for all models used, both the absolute risks were determined for the two treatments and the relative risk between the two treatment plans. Results: The radiation‐induced second cancer risk ranged from 0.12% to 145% for the 2‐field treatment and from 0.84% to 458% for the 4‐field treatment depending on the choice of models. The calculated risks can be much higher than the values reported by epidemiological studies (2–4%). The ratio of risks between the two treatments varied from 1.2 to 9.1. Conclusions: Risk models should be applied with great caution. Great uncertainties underlie absolute risk calculations yielding unrealistic risks; therefore many investigators use the ratio of risk to compare different treatments. However, the ratio of risk between two treatments may also greatly vary depending on the risk models used. This may explain inconsistent findings on the potential increase in risk of IMRT techniques compared to conventional treatments.This work was supported by the Swiss National Science Foundation FNRS 320000‐114101
SU‐E‐T‐141: Leaf Position Verification during Dynamic Beam Delivery of Volumetric Modulated Arc Therapy Using Electronic Portal Imaging Device
Authors: Sarkar B , Manikandan A , Holla R 
Published: November 2011

Purpose: Volumetric‐modulated arc therapy is a technique for delivering intensity‐modulated radiation therapy using rotational beams. During delivery of the rotational beam, the field shape, created by a multileaf collimator (MLC), changes continuously. The objectives of this study were to verify the MLC positional error at some arbitrary intermediate point during delivery for different dose rates and MLC speeds. Methods: The Elekta Synergy‐S has a discreet dose rate, forty pairs of MLC. Dose rate, gantry speed, MLC speed is constant between two Control Points. The MLC Positions were verified with AmSi portal imaging. The leaf speed depends on three factors: ‐ dose rate, delivered MU and distance traveled by MLC. The leaf positions were verified for all combinations of available dose rates 35, 70, 140, 280, 560 MU/min and MLC speed of 0.5, 1, 1.5, 2, 2.5 cm/sec for a dynamically varying field size from 20×16 cm2 to 10×16 cm2 for a 0– 10 degree gantry rotation. Results: The largest MLC Leaf positional error found for 2.5 cm/sec speed for 35MU/min was −1.1±0.26 mm (95% Confidence Intervals‐CI). The minimum leaf positional error encountered for 1.5cm/ sec and 140MU/min was 0.03± 0.16 mm (95% CI). The single highest positional error was −1.31 mm. The maximum and minimum leaf positional error of all 25 sets results mean error of 0.36±0.72mm and − 0.08±0.67mm respectively with 95% CI. The MLC positional error depends on the MLC speed as well as dose rate also. Conclusions: 3.4% tested leaf positional errors found more than tolerance limit (±1 mm). It can be concluded that MLC positional error is higher in case of lower dose rate and highest MLC leaf Speed. The largest three errors (in descending order) encountered for highest speed 2.5 cm/sec and dose rate 35, 70 and 140 MU/min respectively. This clearly indicates lower delivered MU increases the Leaf positional error.No Funding, support and no conflict of interest
SU‐E‐T‐154: Evaluation and Improvement of the ArcCHECK 3D Dosimeter
Authors: Kozelka J , Robinson J , Zhang G , Nelms B , Feygelman V 
Published: November 2011

Purpose: To address important questions regarding calibration and use of the ArcCHECK (Sun Nuclear Corp) detector resulting from its hollow shape and cylindrical array geometry. The goals are to investigate how accurate different treatment planning algorithms are with the phantom containing a large air‐density inhomogeneity; to establish a method of calibrating the detector against an isotropic, energy‐independent dosimeter; and to develop a robust virtual inclinometer capable of providing uninterrupted beam angle information during arc deliveries. Methods: A PMMA shell accommodating an ion chamber at the diode position was designed to replicate the dimensions of the ArcCHECK phantom. The ratio of entrance to exit dose was measured and compared to calculations by five sophisticated commercial algorithms. Field size dependence of the diode response was measured at different locations in the phantom. A novel virtual inclinometer algorithm was designed based on the coincidence of dose grid images projected with attenuation on a common plane. A formalism of reading to dose conversion accounting for the field size and detector position dependence was developed. A practical method of measuring the positional dependence factors against an ion chamber in the actual phantom geometry was designed.Results: Philips Pinnacle CCC, CMS XiO Superposition and Monaco algorithms disagreed with the ion chamber by no more than 1.5%. XiO Convolution and Varian Eclipse AAA were off by >11%. Field size correction is position‐dependent and varies between the hollow and plugged phantom configurations. Virtual inclinometer is robust and deviates no more than 0.5±0.7° from the Dynalog record. An average disagreement is 0.5% between the diode and ion chamber dose measurements in a wide field Conclusions: Using hollow ArcCHECK phantom configuration with Eclipse AAA is not recommended. A robust positional correction based on the novel virtual inclinometer is feasible. Diode “reading to dose” formalism must include field size dependence.This work was supported in part by Sun Nuclear Corp.
SU‐E‐T‐169: Modification and Implementation of the RPC Heterogeneous Thorax Phantom for Verification of Proton Therapy Treatment Procedures
Authors: Blatnica A , Ibbott G , Zhu X , Balter P , White R , Followill D 
Published: November 2011

Purpose: To modify the existing RPC heterogeneous thorax phantom to assess lung tumor proton beam therapy procedures including patient simulation, treatment planning, and treatment delivery. Methods: A new dosimetry/imaging insert was designed for use with the RPC thorax phantom. The insert was constructed of extra heavy balsa wood with density from 0.30 – 0.34 g/cm3 and average HU of −670. A relative linear stopping power of 0.313 was measured. A tapered compression technique eliminated air gaps around the dosimeters. TLDs were positioned in the superior and inferior aspects of a unit density target and EBT2 radiochromic film was placed in three orthogonal planes. The phantom was imaged with a 16 slice CT scanner. A treatment plan with fields at 10 and 80 degree gantry angles and a 15 degree couch kick was designed with an Eclipse TPS utilizing apertures (expanded 10mm) and compensators (smeared 6mm). The plan was delivered three times with new dosimeters for each irradiation.Results: The ratio of measured dose to calculated dose was 0.947±0.009 (superior point) and 0.937±0.003 (inferior point). Gamma analysis utilizing 5%/5mm criteria showed 3 trial average pass rates of 86.7% (axial), 90.0% (coronal), 90.1% (sagittal) and 88.9% (3 plane average). DTA ranged from 0.9 – 2.4mm (axial), 0.4 –1.8mm (coronal), 0.6 – 1.9mm (sagittal). Conclusions: This work indicated that modifications to the existing RPC thorax phantom allowed the evaluation of proton therapy procedures. The differences in measured/calculated doses were higher than expected but consistent with previous experience with this phantom. Gamma analysis and DTA showed good results, with poor correspondence in the distal low dose regions of the treatment fields. Further analysis is underway to determine if the discrepancies reflect inadequacies of the TPS or limitations of the dosimetry system.Work supported in part by PHS grants CA010953 and CA081647, awarded by NCI, DHHS.
SU‐E‐T‐209: Testing of Prototype Delta4AT Diode Array for In‐Vivo Radiotherapy Dosimetry
Authors: Riley S , Matzen T , Carver A 
Published: November 2011

Purpose: The Delta, 4AT, (ScandiDos, Sweden,) is a head‐mounted diode‐array detector that is intended to be used during a patientˈs treatment. The device currently only exists in prototype form. By introducing MU and MLC errors into radiotherapy plans, the ability of the hardware and software to detect errors was measured. The closest separation of the diodes, (when projected to the isocentre plane,) is 8mm in the prototype, but it is intended to reduce this to 2mm in the final device. Methods: The Delta, 4AT</sup> is calibrated for each patient by taking a simultaneous measurement with the existing Delta, 4PT</sup> phantom. The Delta, 4AT</sup> then reports subsequent measurements of the same plan as predicted doses on the two perpendicular diodes arrays within the cylindrical Delta, 4PT</sup> phantom. To test the accuracy of the Delta, 4AT, the Delta, 4PT</sup> was left on the couch for the subsequent beam deliveries and the predicted doses in the Delta, 4PT</sup> were compared to the actual doses. The Delta, 4AT</sup> was calibrated with known good conformal and RapidArcTM plans, (Varian Medical Systems.). MU errors of −1.5%, −3%, +1.5% and +3% were used and MLC errors of +1.5 mm to the X1 bank, +3mm to the X1 bank and +1.5mm and +3mm to an individual MLC. Results: For a RapidArc plan and MU errors, the Delta, 4AT</sup> measurements were within gamma <1 (0.5%/0.5mm) of the Delta, 4PT</sup> for >99% of diodes, (detectors above 20% included). For a RapidArc plan and smaller MLC errors (+1.5mm), the Delta, 4AT</sup> measurements were within gamma < 1 for > 95% of diodes at 3%/3mm. For a conformal plan and a +3mm X1 bank error the Delta, 4AT</sup> measurements were within gamma <1 of the Delta, 4PT</sup> for >95% of diodes at 2%/2mm. Conclusions: The prototype Delta4, AT</sup> has been shown to produce accurate measurements and will allow verification throughout a patientˈs treatment.Thomas Matzen is employed by ScandiDos, the manufacturer of the Delta, 4AT. The meeting registration fees and travel costs of the presenting author may or may not be partly paid by ScandiDos.
SU‐E‐T‐211: Optical Fluorescence Monitoring during External Beam Radiation Therapy Using Cerenkov Emission as Excitation Source
Authors: Axelsson J , Davis S , Gladstone D , Pogue B 
Published: November 2011

Purpose: Cerenkov emission is induced when a charged particle travels faster than the speed of light in a given medium. The Cerenkov effect occurs in everyday radiation therapy of tissue, yet this phenomenon has never been quantitatively characterized. In this study, an investigation of high‐energy radiation from a linear accelerator was carried out, to quantify the induced Cerenkov emission in biological media. Furthermore, we demonstrate that the Cerenkov emission can excite a molecularly produced fluorophore, protoporphyrin IX (PpIX), embedded in biological phantoms. Methods: Electrons at 6–18 MeV energies and photons at 6 or 18 MV energies, from a linear accelerator, were used to induce Cerenkov emission in aqueous phantoms. First, a CMOS camera imaged a water tank in order to investigate the dose distribution of external beam radiation. Secondly, the fluorescent photosensitizer PpIX was mixed into the phantom. An optical fiber bundle, positioned at the phantom surface, collected the Cerenkov emission and the Cerenkov‐induced optical fluorescence. Results: Images acquired in a water tank clearly shows the cross section of the electron (or photon) beam at all energies using a dose rate of approximately 4Gy/min. As expected from the Cerenkov theory the intensity increases as the energy of the radiation increases. Spectra acquired, either with photons or electrons, reveal that the Cerenkov emission excites the PpIX molecule, leading to optical fluorescence in the red spectral region. Conclusions: The results here indicate that molecular fluorescence monitoring during external beam radiotherapy is possible. This could potentially be used as a tool for treatment assessment through the evaluation PpIX production from e.g. high‐grade glioma.This work has been funded by NIH grants RO1CA120368 and PO1CA084203.
SU‐E‐T‐247: A Solution to the Real‐Time Safety Interlock Control of the Linac and the Externally Mounted Multi‐Leaf Collimator
Authors: Tan Youheng , Li Yongjie , Yao Jonathan 
Published: November 2011

Purpose: This study aims to provide a solution for a real‐time safety interlock control of the linac and the externally mounted dynamic multi‐leaf collimator (dMLC) from other manufacturers, between which it is difficult to build a bridge because of the internal interfaces unopened to other manufacturers. Methods: An external dMLC is mounted on the linac head. They can not work corporately and safely if no interlock control is built between them. Our solution is to set a VGA splitter between the linac control computer and its monitor, and from this VGA splitter a VGA signal grabber is connected to the MLC control computer. Through this connection, the data sent to the linac console monitor is also captured and sent to the MLC control computer real time in a form of image. By analyzing this captured image using methods of feature extraction and pattern recognition, the current setting of the linac is extracted and used to judge whether the current setting of the linac is consistent with that stored on the MLC control computer. Results: The display format on the monitor is generally fixed for a specified accelerator, which is helpful for the quick and accurate extraction of the parameter setting of the linac from the captured image. When the parameter settings on linac control computer and MLC control computer are not identical, the MLC control computer pops up an error message, and at the same time, a NOT READY signal is sent to the READY/NOT‐READY circuit in the linac, and hence a safety interlock control is realized. Conclusions: Externally mounted dMLC is an economic solution to upgrade the linac that has no built‐in dMLC. Safety interlock control between them can be effectively realized simply using a VGA signal grabber and a control signal sent to the linac.Funding support: This work was supported by the Program for New Century Excellent Talents in University of China (NCET‐07‐0151) and the Natural Science Foundations of China (61075109, 30730036).