bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐E‐CAMPUS‐I‐02: Estimation of the Dosimetric Error Caused by the Voxelization of Hybrid Computational Phantoms Using Triangle Mesh‐Based Monte Carlo Transport
Authors: Lee C , Badal A 
Published: July 2014

Purpose:Computational voxel phantom provides realistic anatomy but the voxel structure may result in dosimetric error compared to real anatomy composed of perfect surface. We analyzed the dosimetric error caused from the voxel structure in hybrid computational phantoms by comparing the voxel‐based doses at different resolutions with triangle mesh‐based doses.Methods:We incorporated the existing adult male UF/NCI hybrid phantom in mesh format into a Monte Carlo transport code, penMesh that supports triangle meshes. We calculated energy deposition to selected organs of interest for parallel photon beams with three mono energies (0.1, 1, and 10 MeV) in antero‐posterior geometry. We also calculated organ energy deposition using three voxel phantoms with different voxel resolutions (1, 5, and 10 mm) using MCNPX2.7.Results:Comparison of organ energy deposition between the two methods showed that agreement overall improved for higher voxel resolution, but for many organs the differences were small. Difference in the energy deposition for 1 MeV, for example, decreased from 11.5% to 1.7% in muscle but only from 0.6% to 0.3% in liver as voxel resolution increased from 10 mm to 1 mm. The differences were smaller at higher energies. The number of photon histories processed per second in voxels were 6.4×104, 3.3×104, and 1.3×104, for 10, 5, and 1 mm resolutions at 10 MeV, respectively, while meshes ran at 4.0×104 histories/sec.Conclusion:The combination of hybrid mesh phantom and penMesh was proved to be accurate and of similar speed compared to the voxel phantom and MCNPX. The lowest voxel resolution caused a maximum dosimetric error of 12.6% at 0.1 MeV and 6.8% at 10 MeV but the error was insignificant in some organs. We will apply the tool to calculate dose to very thin layer tissues (e.g., radiosensitive layer in gastro intestines) which cannot be modeled by voxel phantoms.
SU‐E‐CAMPUS‐I‐03: Dosimetric Comparison of the Hypoxia Agent Iodoazomycin Arabinoside (IAZA) Labeled with the Radioisotopes I‐123, I‐131 and I‐124
Authors: Jans H‐S , Stypinski D , Mcquarrie S , Kumar P , Mercer J , Wiebe L , McEwan S 
Published: July 2014

Purpose:To compare the radiation dose to normal organs from the radio‐iodinated, hypoxia‐binding radiosensitizer iodoazomycin arabinoside (IAZA) for three different isotopes of iodine.Methods:Dosimety studies with normal volunteers had been carried out with [123I]IAZA, a drug binding selectively to hypoxic sites. Two other isotopes of iodine, 131I and 124I, offer the opportunity to use IAZA as an agent for radioisotope therapy and as an imaging tracer for Positron Emission Tomography. Radioisotope dosimetry for 131I and 124I was performed by first deriving from the [123I]IAZA studies biological uptake and excretion data. The cumulated activities for 131I or 124I where obtained by including their half‐lives when integrating the biological data and then extrapolating to infinite time points considering a) physical decay only or b) physical and biological excretion. Doses were calculated using the Medical Internal Radiation Dose (MIRD) schema (OLINDA1.1 code, Vanderbilt 2007).Results:Compared to 123I, organ doses were elevated on average by a factor 6 and 9 for 131I and 124I, respectively, if both physical decay and biological excretion were modeled. If only physical decay is considered, doses increase by a factor 18 (131I) and 19 (124I). Highest organ doses were observed in intestinal walls, urinary bladder and thyroid. Effective doses increased by a factor 11 and 14 for 131I and 124I, respectively, if biological and physical decay are present. Purely physical decay yields a 23‐fold increase over 123I for both, 131I and 124I.Conclusion:Owing to the significant dose increase, caused by their longer half life and the approximately 10 times larger electronic dose deposited in tissue per nuclear decay, normal tissue doses of IAZA labeled with 131I and 124I need to be carefully considered when designing imaging and therapy protocols for clinical trials. Effective blocking of iodine uptake in the thyroid is essential. Alberta Innovates – Health Solutions (AIHS) and Canadian Institutes of Health Research (CIHR)
SU‐E‐CAMPUS‐I‐04: Automatic Skin‐Dose Mapping for An Angiographic System with a Region‐Of‐Interest, High‐Resolution Detector
Authors: Vijayan S , Rana V , Setlur Nagesh S , Ionita C , Rudin S , Bednarek D 
Published: July 2014

Purpose:Our real‐time skin dose tracking system (DTS) has been upgraded to monitor dose for the micro‐angiographic fluoroscope (MAF), a high‐resolution, small field‐of‐view x‐ray detector.Methods:The MAF has been mounted on a changer on a clinical C‐Arm gantry so it can be used interchangeably with the standard flat‐panel detector (FPD) during neuro‐interventional procedures when high resolution is needed in a region‐of‐interest. To monitor patient skin dose when using the MAF, our DTS has been modified to automatically account for the change in scatter for the very small MAF FOV and to provide separated dose distributions for each detector. The DTS is able to provide a color‐coded mapping of the cumulative skin dose on a 3D graphic model of the patient. To determine the correct entrance skin exposure to be applied by the DTS, a correction factor was determined by measuring the exposure at the entrance surface of a skull phantom with an ionization chamber as a function of entrance beam size for various beam filters and kVps. Entrance exposure measurements included primary radiation, patient backscatter and table forward scatter. To allow separation of the dose from each detector, a parameter log is kept that allows a replay of the procedure exposure events and recalculation of the dose components. The graphic display can then be constructed showing the dose distribution from the MAF and FPD separately or together.Results:The DTS is able to provide separate displays of dose for the MAF and FPD with field‐size specific scatter corrections. These measured corrections change from about 49% down to 10% when changing from the FPD to the MAF.Conclusion:The upgraded DTS allows identification of the patient skin dose delivered when using each detector in order to achieve improved dose management as well as to facilitate peak skin‐dose reduction through dose spreading.Research supported in part by Toshiba Medical Systems Corporation and NIH Grants R43FD0158401, R44FD0158402 and R01EB002873
SU‐E‐CAMPUS‐I‐05: Internal Dosimetric Calculations for Several Imaging Radiopharmaceuticals in Preclinical Studies and Quantitative Assessment of the Mouse Size Impact On Them. Realistic Monte Carlo Simulations Based On the 4D‐MOBY Model
Authors: Kostou T , Papadimitroulas P , Loudos G , Kagadis GC 
Published: July 2014

Purpose:Commonly used radiopharmaceuticals were tested to define the most important dosimetric factors in preclinical studies. Dosimetric calculations were applied in two different whole‐body mouse models, with varying organ size, so as to determine their impact on absorbed doses and S‐values. Organ mass influence was evaluated with computational models and Monte Carlo(MC) simulations.Methods:MC simulations were executed on GATE to determine dose distribution in the 4D digital MOBY mouse phantom. Two mouse models, 28 and 34 g respectively, were constructed based on realistic preclinical exams to calculate the absorbed doses and S‐values of five commonly used radionuclides in SPECT/PET studies (18F, 68Ga, 177Lu, 111In and 99mTc).Radionuclide biodistributions were obtained from literature. Realistic statistics (uncertainty lower than 4.5%) were acquired using the standard physical model in Geant4. Comparisons of the dosimetric calculations on the two different phantoms for each radiopharmaceutical are presented.Results:Dose per organ in mGy was calculated for all radiopharmaceuticals. The two models introduced a difference of 0.69% in their brain masses, while the largest differences were observed in the marrow 18.98% and in the thyroid 18.65% masses.Furthermore, S‐values of the most important target‐organs were calculated for each isotope. Source‐organ was selected to be the whole mouse body.Differences on the S‐factors were observed in the 6.0–30.0% range. Tables with all the calculations as reference dosimetric data were developed.Conclusion:Accurate dose per organ and the most appropriate S‐values are derived for specific preclinical studies. The impact of the mouse model size is rather high (up to 30% for a 17.65% difference in the total mass), and thus accurate definition of the organ mass is a crucial parameter for self‐absorbed S values calculation.Our goal is to extent the study for accurate estimations in small animal imaging, whereas it is known that there is a large variety in the anatomy of the organs.
SU‐E‐CAMPUS‐I‐06: Y90 PET/CT for the Instantaneous Determination of Both Target and Non‐Target Absorbed Doses Following Hepatic Radioembolization
Authors: Pasciak A , Kao J 
Published: July 2014

PurposeThe process of converting Yttrium‐90 (Y90) PET/CT images into 3D absorbed dose maps will be explained. The simple methods presented will allow the medical physicst to analyze Y90 PET images following radioembolization and determine the absorbed dose to tumor, normal liver parenchyma and other areas of interest, without application of Monte‐Carlo radiation transport or dose‐point‐kernel (DPK) convolution.MethodsAbsorbed dose can be computed from Y90 PET/CT images based on the premise that radioembolization is a permanent implant with a constant relative activity distribution after infusion. Many Y90 PET/CT publications have used DPK convolution to obtain 3D absorbed dose maps. However, this method requires specialized software limiting clinical utility. The Local Deposition method, an alternative to DPK convolution, can be used to obtain absorbed dose and requires no additional computer processing. Pixel values from regions of interest drawn on Y90 PET/CT images can be converted to absorbed dose (Gy) by multiplication with a scalar constant.ResultsThere is evidence that suggests the Local Deposition method may actually be more accurate than DPK convolution and it has been successfully used in a recent Y90 PET/CT publication. We have analytically compared dose‐volume‐histograms (DVH) for phantom hot‐spheres to determine the difference between the DPK and Local Deposition methods, as a function of PET scanner point‐spread‐function for Y90. We have found that for PET/CT systems with a FWHM greater than 3.0 mm when imaging Y90, the Local Deposition Method provides a more accurate representation of DVH, regardless of target size than DPK convolution.ConclusionUsing the Local Deposition Method, post‐radioembolization Y90 PET/CT images can be transformed into 3D absorbed dose maps of the liver. An interventional radiologist or a Medical Physicist can perform this transformation in a clinical setting, allowing for rapid prediction of treatment efficacy by comparison to published tumoricidal thresholds.
SU‐E‐CAMPUS‐J‐01: TG142 Complied Comprehensive Commissioning and Quality Assurance Procedure for Respiratory Gating
Authors: Woods K , Rong Y , Weldon M , Gupta N 
Published: July 2014

Purpose:To develop and establish a comprehensive gating commissioning and quality assurance procedure in compliance with TG142.Methods:Quality assurance tests on three Varian LINACs included beam output and energy constancy, calibration of surrogate, as well as phase and amplitude gating temporal accuracy. A diode array (MapCHECK 2) and film (Gafchromic EBT2) were used to measure the temporal accuracy of phase and amplitude gating windows. A motion simulation device (MotionSim) was used to simulate respiratory motion for both detectors. An end‐to‐end test was also performed on all three machines. The overall accuracy and uncertainty was analyzed and compared.Results:The end‐to‐end test using an anthropomorphic lung phantom (CIRS) results in an OSL dose difference reading within 5% (within measurement uncertainty) for both phase and amplitude gated treatment. Film results showed < 1% agreement between profiles for gated delivery and predicted dose. The diode array demonstrated an 80% passing rate for gamma criteria of 2%/0.2 mm, which results in a 111 msec temporal accuracy. However, the diode array is limited by its spatial resolution of measurements, due to its 7.07 mm diode spacing. Film provided higher measuring resolution, thus demonstrated a temporal accuracy of <100 msec.Conclusion:Results showed consistent respiratory gating stability and accuracy. MapCHECK 2 may not be sufficient for the temporal accuracy test in the respiratory gating treatment in order to meet the corresponding tolerance in TG142. One would need to decrease respiratory motion speed from the surrogate or tighten the gating window in order to be within tolerance of 100 msec temporal accuracy per TG‐142. The end‐to‐end test offers insight to the overall accuracy and uncertainties with a gated protocol. Compared to static delivery, respiratory motion increases the overall uncertainty of treatment delivery from 3% to 5% dose difference.
SU‐E‐CAMPUS‐J‐02: Implementation of Routine Clinical Daily Dose Evaluation for Patient Specific Quality Control
Authors: Brock K , Lee C , Lockhart C , Balter J , Ten Haken R , Eisbruch A 
Published: July 2014

Purpose:The use of deformable registration and dose assessment in prospective clinical trials and routine patient quality control has been limited, largely due to lack of integration of the tools into standard clinical practice and decision support tools. A clinical workflow has been developed and implemented in a standard planning system using in room image.Methods:A patient‐specific quality control procedure has been initiated to ensure safe and accurate treatment delivery and develop decision making guidelines for future adaptation scenarios. Deformable registration, contour propagation, and dose calculation was performed in a clinical system (Varian, Eclipse v11). Twenty head and neck patients diagnosed with base of tongue cancer and treated with volumetric modulated arc therapy (VMAT) following daily kV‐CBCT were evaluated. The planning CT was deformed to the daily CBCT to propagate the planning contours. Daily dose was calculated on the CBCT using a density calibration table and evaluated using the mapped contours. Deviations in the normal tissues were evaluated including the mean dose to the superior constrictors, left and right parotid glands (LPG, RPG), and left and right submandibular glands (LSG, RSG). The CTV D95 was also evaluated.Results:Deformable registration and contour propagation was qualitatively evaluated and deemed acceptable for each fraction. The average (SD) daily fluctuation (planned‐daily) in mean dose to the superior constrictor, LPG, RPG, LSG, and RSG was −3.0(6.0), 1.4(8.8), −1.1(10.7), 1.0(5.4), −2.0(8.5) cGy, respectively. The average (SD) daily fluctuation in D95 for the CTV was 3.7(3.8) cGy.Conclusion:Daily dose assessment is feasible in a clinically available system. Data to guide adaptive decision making guidelines have been suggested, but require evaluation on additional patients for validity, which is ongoing. Dose accumulation, which is necessary for optimizing adaptive replanning, is needed within the clinical system to fully take advantage of this data.
SU‐E‐CAMPUS‐J‐03: Commissioning of the On‐Board Cone‐Beam CT System Equipped On the Rotating Gantry of a Proton Therapy System
Authors: Takao S , Shimizu S , Miyamoto N , Matsuura T , Toramatsu C , Nihongi H , Yamada T , Matsuda K , Sasaki T , Nagamine Y , Baba R , Umekawa T , Umegaki K , Shirato H 
Published: July 2014

Purpose:Proton therapy requires highly‐precise image guidance in patient setup to ensure accurate dose delivery. Cone‐beam CT (CBCT) is expected to play an important role to reduce uncertainties in patient setup. Hokkaido University has developed a new proton therapy system dedicated to spot‐scanning under a collaborative work with Hitachi Ltd. In our system, an orthogonal X‐ray imaging system is mounted on a full‐rotating gantry. On‐board CBCT imaging is therefore available. We have conducted commissioning of the CBCT system for clinical use in proton therapy.Methods:The orthogonal X‐ray imaging system, which consists of two sets of X‐ray tubes and flat panel detectors (FPDs), are equipped on the rotating gantry. The FPDs are mounted on the proton beam nozzle and can be retracted when not in use. The distance between the X‐ray source and the FPD is about 2.1 m. The maximum rotation speed of the gantry is 1 rpm, so CBCT images can be acquired in approximately 1 minute. The maximum reconstruction volume is nearly 40 cm in diameter and 20 cm in axial length. For commissioning of the CBCT system, mechanical accuracy of the rotating gantry first was evaluated. Imaging performance was examined via quantitative evaluation of image quality.Results:Through the mechanical test, the isocentricity of the gantry was confirmed to be less than 1 mm. Moreover, it was improved to 0.5 mm with an appropriate correction. The accurate rotation of the gantry contributes to the CBCT image quality. In the image quality test, objects with 7 line‐pairs per cm, which corresponds to a line spacing of 0.071 cm, could be discerned. Spatial linearity and uniformity were also sufficient.Conclusion:Clinical commissioning of the on‐board CBCT system for proton therapy was conducted, and CBCT images with sufficient quality were successfully obtained.This research was supported by the Cabinet Office, Government of Japan and the Japan Society for the Promotion of Science (JSPS) through the Funding Program for World‐Leading Innovative R&D on Science and Technology (FIRST Program), initiated by the Council for Science and Technology Policy (CSTP).
SU‐E‐CAMPUS‐J‐04: Image Guided Radiation Therapy (IGRT): Review of Technical Standards and Credentialing in Radiotherapy Clinical Trials
Authors: Giaddui T , Cui Y , Chen W , Yu J , Gong Y , Craig T , Dawson L , Al‐Hallaq H , Chmura S , Yin F , Galvin J , Xiao Y 
Published: July 2014

Purpose:To review IGRT credentialing experience and unexpected technical issues encountered in connection with advanced radiotherapy technologies as implemented in RTOG clinical trials. To update IGRT credentialing procedures with the aim of improving the quality of the process, and to increase the proportion of IGRT credentialing compliance. To develop a living disease site‐specific IGRT encyclopedia.Methods:Numerous technical issues were encountered during the IGRT credentialing process. The criteria used for credentialing review were based on: image quality; anatomy included in fused data sets and shift results. Credentialing requirements have been updated according to the AAPM task group reports for IGRT to ensure that all required technical items are included in the quality review process. Implementation instructions have been updated and expanded for recent protocols.Results:Technical issues observed during the credentialing review process include, but are not limited to: poor quality images; inadequate image acquisition region; poor data quality; shifts larger than acceptable; no soft tissue surrogate. The updated IGRT credentialing process will address these issues and will also include the technical items required from AAPM: TG 104; TG 142 and TG 179 reports. An instruction manual has been developed describing a remote credentialing method for reviewers. Submission requirements are updated, including images/documents as well as facility questionnaire. The review report now includes summary of the review process and the parameters that reviewers check. We have reached consensus on the minimum IGRT technical requirement for a number of disease sites. RTOG 1311(NRG‐BR002A Phase 1 Study of Stereotactic Body Radiotherapy (SBRT) for the Treatment of Multiple Metastases) is an example, here; the protocol specified the minimum requirement for each anatomical sites (with/without fiducials).Conclusion:Technical issues are identified and reported. IGRT guidelines are updated, with the corresponding credentialing requirements. An IGRT encyclopedia describing site‐specific implementation issues is currently in development.
SU‐E‐CAMPUS‐J‐05: Quantitative Investigation of Random and Systematic Uncertainties From Hardware and Software Components in the Frameless 6DBrainLAB ExacTrac System
Authors: Keeling V , Jin H , Hossain S , Ahmad S , Ali I 
Published: July 2014

Purpose:To evaluate setup accuracy and quantify individual systematic and random errors for the various hardware and software components of the frameless 6D‐BrainLAB ExacTrac system.Methods:35 patients with cranial lesions, some with multiple isocenters (50 total lesions treated in 1, 3, 5 fractions), were investigated. All patients were simulated with a rigid head‐and‐neck mask and the BrainLAB localizer. CT images were transferred to the IPLAN treatment planning system where optimized plans were generated using stereotactic reference frame based on the localizer. The patients were setup initially with infrared (IR) positioning ExacTrac system. Stereoscopic X‐ray images (XC: X‐ray Correction) were registered to their corresponding digitally‐reconstructed‐radiographs, based on bony anatomy matching, to calculate 6D‐translational and rotational (Lateral, Longitudinal, Vertical, Pitch, Roll, Yaw) shifts. XC combines systematic errors of the mask, localizer, image registration, frame, and IR. If shifts were below tolerance (0.7 mm translational and 1 degree rotational), treatment was initiated; otherwise corrections were applied and additional X‐rays were acquired to verify patient position (XV: X‐ray Verification). Statistical analysis was used to extract systematic and random errors of the different components of the 6D‐ExacTrac system and evaluate the cumulative setup accuracy.Results:Mask systematic errors (translational; rotational) were the largest and varied from one patient to another in the range (−15 to 4mm; −2.5 to 2.5degree) obtained from mean of XC for each patient. Setup uncertainty in IR positioning (0.97,2.47,1.62mm;0.65,0.84,0.96degree) was extracted from standard‐deviation of XC. Combined systematic errors of the frame and localizer (0.32,−0.42,−1.21mm; −0.27,0.34,0.26degree) was extracted from mean of means of XC distributions. Final patient setup uncertainty was obtained from the standard deviations of XV (0.57,0.77,0.67mm,0.39,0.35,0.30degree).Conclusion:Statistical analysis was used to calculate cumulative and individual systematic errors from the different hardware and software components of the 6D‐ExacTrac‐system. Patients were treated with cumulative errors (<1mm,<1degree) with XV image guidance.