bluuebunny/crossref_metadata_2025 huggingface dataset:
SU‐G‐IeP3‐10: Molecular Imaging with Clinical X‐Ray Sources and Compton Cameras
Authors: Vernekohl D , Ahmad M , Chinn G , Xing L
Published: July 2016

Purpose:

The application of Compton cameras (CC) is a novel approach translating XFCT to a practical modality realized with clinical CT systems without the restriction of pencil beams. The dual modality design offers additional information without extra patient dose. The purpose of this work is to investigate the feasibility and efficacy of using CCs for volumetric x‐ray fluorescence (XF) imaging by Monte Carlo (MC) simulations and statistical image reconstruction.

Methods:

The feasibility of a CC for imaging x‐ray fluorescence emitted from targeted lesions is examined by MC simulations. 3 mm diameter water spheres with various gold concentrations and detector distances are placed inside the lung of an adult human phantom (MIRD) and are irradiated with both fan and cone‐beam geometries. A sandwich design CC composed of Silicon and CdTe is used to image the gold nanoparticle distribution. The detection system comprises four 16×26 cm2 detector panels placed on the chest of a MIRD phantom. Constraints of energy‐, spatial‐resolution, clinical geometries and Doppler broadening are taken into account. Image reconstruction is performed with a list‐mode MLEM algorithm with cone‐projector on a GPU.

Results:

The comparison of reconstruction of cone‐ and fan‐beam excitation shows that the spatial resolution is improved by 23% for fan‐beams with significantly decreased processing time. Cone‐beam excitation increases scatter content disturbing quantification of lesions near the body surface. Spatial resolution and detectability limit in the center of the lung is 8.7 mm and 20 fM for 50 nm diameter gold nanoparticles at 20 mGy.

Conclusion:

The implementation of XFCT with a CC is a feasible method for molecular imaging with high atomic number probes. Given constrains of detector resolutions, Doppler broadening, and limited exposure dose, spatial resolutions comparable with PET and molecular sensitivities in the fM range are realizable with current detector technology.
SU‐G‐IeP3‐11: On the Utility of Pixel Variance to Characterize Noise for Image Receptors of Digital Radiography Systems
Authors: Finley C , Dave J
Published: July 2016

Purpose:

To characterize noise for image receptors of digital radiography systems based on pixel variance.

Methods:

Nine calibrated digital image receptors associated with nine new portable digital radiography systems (Carestream Health, Inc., Rochester, NY) were used in this study. For each image receptor, thirteen images were acquired with RQA5 beam conditions for input detector air kerma ranging from 0 to 110 µGy, and linearized ‘For Processing’ images were extracted. Mean pixel value (MPV), standard deviation (SD) and relative noise (SD/MPV) were obtained from each image using ROI sizes varying from 2.5×2.5 to 20×20 mm2. Variance (SD2) was plotted as a function of input detector air kerma and the coefficients of the quadratic fit were used to derive structured, quantum and electronic noise coefficients. Relative noise was also fitted as a function of input detector air kerma to identify noise sources. The fitting functions used least‐squares approach.

Results:

The coefficient of variation values obtained using different ROI sizes was less than 1% for all the images. The structured, quantum and electronic coefficients obtained from the quadratic fit of variance (r>0.97) were 0.43±0.10, 3.95±0.27 and 2.89±0.74 (mean ± standard deviation), respectively, indicating that overall the quantum noise was the dominant noise source. However, for one system electronic noise coefficient (3.91) was greater than quantum noise coefficient (3.56) indicating electronic noise to be dominant. Using relative noise values, the power parameter of the fitting equation (|r|>0.93) showed a mean and standard deviation of 0.46±0.02. A 0.50 value for this power parameter indicates quantum noise to be the dominant noise source whereas values around 0.50 indicate presence of other noise sources.

Conclusion:

Characterizing noise from pixel variance assists in identifying contributions from various noise sources that, eventually, may affect image quality. This approach may be integrated during periodic quality assessments of digital image receptors.
SU‐G‐JeP3‐01: A Method to Quantify Lung SBRT Target Localization Accuracy Based On Digitally Reconstructed Fluoroscopy
Authors: Lafata K , Ren L , Cai J , Yin F
Published: July 2016

Purpose:

To develop a methodology based on digitally‐reconstructed‐fluoroscopy (DRF) to quantitatively assess target localization accuracy of lung SBRT, and to evaluate using both a dynamic digital phantom and a patient dataset.

Methods:

For each treatment field, a 10‐phase DRF is generated based on the planning 4DCT. Each frame is pre‐processed with a morphological top‐hat filter, and corresponding beam apertures are projected to each detector plane. A template‐matching algorithm based on cross‐correlation is used to detect the tumor location in each frame. Tumor motion relative beam aperture is extracted in the superior‐inferior direction based on each frame's impulse response to the template, and the mean tumor position (MTP) is calculated as the average tumor displacement. The DRF template coordinates are then transferred to the corresponding MV‐cine dataset, which is retrospectively filtered as above. The treatment MTP is calculated within each field's projection space, relative to the DRF‐defined template. The field's localization error is defined as the difference between the DRF‐derived‐MTP (planning) and the MV‐cine‐derived‐MTP (delivery). A dynamic digital phantom was used to assess the algorithm's ability to detect intra‐fractional changes in patient alignment, by simulating different spatial variations in the MV‐cine and calculating the corresponding change in MTP. Inter‐and‐intra‐fractional variation, IGRT accuracy, and filtering effects were investigated on a patient dataset.

Results:

Phantom results demonstrated a high accuracy in detecting both translational and rotational variation. The lowest localization error of the patient dataset was achieved at each fraction's first field (mean=0.38mm), with Fx3 demonstrating a particularly strong correlation between intra‐fractional motion‐caused localization error and treatment progress. Filtering significantly improved tracking visibility in both the DRF and MV‐cine images.

Conclusion:

We have developed and evaluated a methodology to quantify lung SBRT target localization accuracy based on digitally‐reconstructed‐fluoroscopy. Our approach may be useful in potentially reducing treatment margins to optimize lung SBRT outcomes.

R01‐184173
SU‐G‐JeP3‐03: Effect of Robot Pose On Beam Blocking for Ultrasound Guided SBRT of the Prostate
Authors: Gerlach S , Kuhlemann I , Ernst F , Fuerweger C , Schlaefer A
Published: July 2016

Purpose:

Ultrasound presents a fast, volumetric image modality for real‐time tracking of abdominal organ motion. How‐ever, ultrasound transducer placement during radiation therapy is challenging. Recently, approaches using robotic arms for intra‐treatment ultrasound imaging have been proposed. Good and reliable imaging requires placing the transducer close to the PTV. We studied the effect of a seven degrees of freedom robot on the fea‐sible beam directions.

Methods:

For five CyberKnife prostate treatment plans we established viewports for the transducer, i.e., points on the patient surface with a soft tissue view towards the PTV. Choosing a feasible transducer pose and using the kinematic redundancy of the KUKA LBR iiwa robot, we considered three robot poses. Poses 1 to 3 had the elbow point anterior, superior, and inferior, respectively. For each pose and each beam starting point, the pro‐jections of robot and PTV were computed. We added a 20 mm margin accounting for organ / beam motion. The number of nodes for which the PTV was partially of fully blocked were established. Moreover, the cumula‐tive overlap for each of the poses and the minimum overlap over all poses were computed.

Results:

The fully and partially blocked nodes ranged from 12% to 20% and 13% to 27%, respectively. Typically, pose 3 caused the fewest blocked nodes. The cumulative overlap ranged from 19% to 29%. Taking the minimum overlap, i.e., considering moving the robot's elbow while maintaining the transducer pose, the cumulative over‐lap was reduced to 16% to 18% and was 3% to 6% lower than for the best individual pose.

Conclusion:

Our results indicate that it is possible to identify feasible ultrasound transducer poses and to use the kinematic redundancy of a 7 DOF robot to minimize the impact of the imaging subsystem on the feasible beam directions for ultrasound guided and motion compensated SBRT.

Research partially funded by DFG grants ER 817/1‐1 and SCHL 1844/3‐1.
SU‐G‐JeP3‐09: Tumor Location Prediction Using Natural Respiratory Volume for Respiratory Gated Radiation Therapy (RGRT): System Verification Study
Authors: Kim M , Jung J , Yoon D , Shin H , Kim S , Suh T
Published: July 2016

Purpose:

Respiratory gated radiation therapy (RGRT) gives accurate results when a patient's breathing is stable and regular. Thus, the patient should be fully aware during respiratory pattern training before undergoing the RGRT treatment. In order to bypass the process of respiratory pattern training, we propose a target location prediction system for RGRT that uses only natural respiratory volume, and confirm its application.

Methods:

In order to verify the proposed target location prediction system, an in‐house phantom set was used. This set involves a chest phantom including target, external markers, and motion generator. Natural respiratory volume signals were generated using the random function in MATLAB code. In the chest phantom, the target takes a linear motion based on the respiratory signal. After a four‐dimensional computed tomography (4DCT) scan of the in‐house phantom, the motion trajectory was derived as a linear equation. The accuracy of the linear equation was compared with that of the motion algorithm used by the operating motion generator. In addition, we attempted target location prediction using random respiratory volume values.

Results:

The correspondence rate of the linear equation derived from the 4DCT images with the motion algorithm of the motion generator was 99.41%. In addition, the average error rate of target location prediction was 1.23% for 26 cases.

Conclusion:

We confirmed the applicability of our proposed target location prediction system for RGRT using natural respiratory volume. If additional clinical studies can be conducted, a more accurate prediction system can be realized without requiring respiratory pattern training.
SU‐G‐TeP3‐03: Dose Enhancement of Gold Nanoparticle in Proton Therapy: A Monte Carlo Study Based On the Transmission Electron Microscopy Imaging
Authors: Ma Y , Laprise‐Pelletier M , Lagueux J , Cote M , Fordin M , Beaulieu L
Published: July 2016

Purpose:

Gold nanoparticle (GNP) is a promising radiosensitizer that selectively boosts tumor dose in radiotherapy. Transmission electron microscopy (TEM) imaging observations recently revealed for the first time that GNP exists in vivo in the form of highly localized vesicles, instead of hypothetical uniform distribution. This work investigates the corresponding difference of energy deposition in proton therapy.

Methods:

First, single vesicles of various radii were constructed by packing GNPs (as Φ50 nm gold spheres) in spheres and were simulated, as well as a single GNP. The radial energy depositions (REDs) were scored using 100 concentric spherical shells from 0.1µm to 10µm, 0.1µm thickness each, for both vesicles and GNP, and compared. TEM images, 8 days after injection in a PC3 prostate cancer murine model, were used to extract position/dimension of vesicles, as well as contours of cytoplasmic and nucleus membranes. Vesicles were then constructed based on the TEM images. A 100 MeV proton beam was studied by using the Geant4‐DNA code, which simulates all energy deposition events.

Results:

The vesicle REDs, normalized to the same proton energy loss as in a single GNP, are larger (smaller) than that of a single GNP when radius >2µm (<2µm). The peak increase (at about 3µm radius) is about 10% and 18% for Φ1µm and Φ1.6µm vesicles respectively, relative to a single GNP. The TEM‐based simulation resulted in a larger energy deposition (by about one order of magnitude) that follows completely different pattern from that of hypothetical GNP distributions (regular dotted pattern in extracellular and/or extranucleus regions).

Conclusion:

The in vivo energy deposition, both in pattern and magnitude, of proton therapy is greatly affected by the true distribution of the GNP, as illustrated by the presence of GNP vesicles compared to hypothetical scenarios.

Work supported by NSERC Discovery Grant #435510, Canada
SU‐G‐TeP3‐04: Evaluation of the Dose Enhancement with Gold Nanoparticle in Microdosimetry Level Using the Geant4‐DNA Toolkit
Authors: He C , Chow J
Published: July 2016

Purpose:

This study investigated the dose enhancement effect of using gold nanoparticles (GNP) as radiation sensitizers radiated by different photon beam energies. Microdosimetry of photon‐irradiated GNP was determined by the Geant4‐DNA process in the DNA scale.

Methods:

Monte Carlo simulation was conducted using the Geant4 toolkit (ver. 10.2). A GNP with different sizes (30, 50, and 100nm diameter sphere) and a DNA were placed in a water cube (1µm3). The GNP was irradiated by photon beams with different energies (50, 100, and 150keV) and produced secondary electrons to increase the dose to the DNA. Energy depositions were calculated for both with and without GNP and to investigate the dose enhancement effect at the DNA. The distance between the GNP and DNA was varied to optimize the best GNP position to the DNA. The photon beam source was set to 200nm from the GNP in each simulation.

Results:

It is found that GNP had a dose enhancement effect on kV photon radiations. For Monte Carlo results on different GNP sizes, distances between the GNP and DNA, and photon beam energies, enhancement ratio was found increasing as GNP size increased. The distance between the GNP and DNA affected the result that as distance increased while the dose enhancement ratio decreased. However, the effect of changing distance was not as significant as varying the GNP size. In addition, increasing the photon beam energy also increased the dose enhancement ratio. The largest dose enhancement ratio was found to be 3.5, when the GNP (100nm diameter) irradiated by the 150keV photon beam was set to 80nm from the DNA.

Conclusion:

Dose enhancement was determined in the DNA with GNP in the microdosimetry scale. It is concluded that the dose enhancement varied with the photon beam energy, GNP size and distance between the GNP and DNA.
SU‐G‐TeP3‐05: In Vitro Demonstration of Endothelial Dose Enhancement Due to Gold Nanoparticles During Low‐Voltage Radiotherapy
Authors: Yasmin‐Karim S , Moreau M , Kumar R , Makrigiorgos GM , Hanlon J , Arnoldussen M , Hempstead J , Celli J , Ngwa W
Published: July 2016

Purpose:

Oraya Therapy uses low‐voltage, stereotactic, highly targeted X‐rays for the treatment of wet age‐related macular degeneration (AMD) — offering a new option for patients worldwide. Neovascular endothelial cells play a crucial role in the pathogenesis of this disease. This in‐vitro study investigates the potential of gold nanoparticles (GNP) to enhance endothelial cell damage during low‐voltage radiotherapy towards potential applications in the treatment of wet‐AMD.

Methods:

Primary human umbilical cord vein endothelium cells (HUVEC) were treated with 1.4 nm sized GNPs for 24 hrs and then irradiated with variable X‐ray doses using an Oraya therapy system (100 kVp) or a Small Animal Radiation and Research platform (SARRP) at other beam qualities (up to 220 kVp). Radio‐sensitization was assessed by clonogenic assays. Variable concentrations of GNPs (0.05 mg/ml, 0.1 mg/ml, 0.25 mg/ml, 0.5 mg/ml, and 1 mg/ml) where employed. The dose enhancement factor (DEF) was calculated as the ratio of radiation doses required to give the same biological effect (survival factor, SF) with and without GNPs.

Results:

Preliminary results show DEFs of up to 2.62 for the different combinations of x‐ray doses and GNP concentrations and beam qualities. In general the DEF increased with increase in GNP concentration. However, for high doses the effect of GNP becomes less apparent likely due to already high cell kill by the radiation alone.

Conclusion:

The findings suggest that targeted GNPs can play a significant synergistic role in enhancing stereotactic radiosurgery for wet AMD. The results also provide impetus for ongoing studies to find the optimal synergy between the doses or beam energies and GNPs concentration. This will benefit in‐vivo studies towards development of nanoparticle‐aided radiotherapy for treatment of wet‐AMD and potentially ocular cancers.
SU‐G‐TeP3‐12: Retrospective Assessment of R2star Using Ultra‐High Field MRI in a Rodent Model of Radiation Necrosis
Authors: Belliveau J , Menon R
Published: July 2016

Purpose:

To establish a quantitative MRI method that would be capable of predicting radiation necrosis without using a contrast agent.

Methods:

Healthy male Fischer 344 rats were irradiated using an animal irradiator capable of delivering 2.3 Gy/min with a kVp of 225 V. A dose of 40 Gy was given to half the brain in a single session. Rats were scanned using a 9.4 T animal MRI before irradiation and every two weeks following radiation until either necrosis developed or they were sacrificed for health reasons. A multi‐echo gradient‐echo sequence was acquired at every time point and the apparent transverse relaxation rate R2* was calculated based on the measured signal decay. At the last time point, an ROI mask with an R2* value of greater than 45 s−1 was applied in the area of the external and internal capsule where radiation necrosis was confirmed. A retrospective analysis was performed to determine whether R2* values would be able to predict where radiation necrosis would occur.

Results:

Radiation necrosis was morphologically visible between weeks 22–24 following treatment. Gadolinium MRI and histology confirmed radiation necrosis in the area of MRI enhancement. Our data suggests that there is a trend towards significance in the lesion as early as 12 weeks prior to morphological changes on MRI with significance occurring 6 weeks prior (p≤0.05, p≤0.01 at week 24). Measurements of the R2* in the hippocampus did not show any significant difference; however, there are areas of visible R2* change within sub‐hippocampal regions.

Conclusion:

R2* is a promising method that could be able to predict an underlying disease process that occurs prior to radiation necrosis. The constant increase in R2* values suggests a possible neuroinflammatory mechanism rather than an acute vascular event where R2* would tend to decrease in the area.
SU‐G‐IeP4‐04: DD‐Neutron Source Collimation for Neutron Stimulated Emission Computed Tomography: A Monte Carlo Simulation Study
Authors: Fong G , Kapadia A
Published: July 2016

Purpose:

To optimize collimation and shielding for a deuterium‐deuterium (DD) neutron generator for an inexpensive and compact clinical neutron imaging system. The envisioned application is cancer diagnosis through Neutron Stimulated Emission Computed Tomography (NSECT).

Methods:

Collimator designs were tested with an isotropic 2.5 MeV neutron source through GEANT4 simulations. The collimator is a 52×52×52 cm3 polyethylene block coupled with a 1 cm lead sheet in sequence. Composite opening was modeled into the collimator to permit passage of neutrons. The opening varied in shape (cylindrical vs. tapered), size (1–5 cm source‐side and target‐side openings) and aperture placements (13–39 cm from source‐side). Spatial and energy distribution of neutrons and gammas were tracked from each collimator design. Parameters analyzed were primary beam width (FWHM), divergence, and efficiency (percent transmission) for different configurations of the collimator. Select resultant outputs were then used for simulated NSECT imaging of a virtual breast phantom containing a 2.5 cm diameter tumor to assess the effect of the collimator on spatial resolution, noise, and scan time. Finally, composite shielding enclosure made of polyethylene and lead was designed and evaluated to block 99.99% of neutron and gamma radiation generated in the system.

Results:

Analysis of primary beam indicated the beam‐width is linear to the aperture size. Increasing source‐side opening allowed at least 20% more neutron throughput for all designs relative to the cylindrical openings. Maximum throughput for all designs was 364% relative to cylindrical openings.

Conclusion:

The work indicates potential for collimating and shielding a DD neutron generator for use in a clinical NSECT system. The proposed collimator designs produced a well‐defined collimated neutron beam that can be used to image samples of interest with millimeter resolution. Balance in output efficiency, noise reduction, and scan time should be considered to determine the optimal design for specific NSECT applications.
SU‐G‐IeP4‐11: Monitoring Tumor Growth in Subcutaneous Murine Tumor Model in Vivo: A Comparison Between MRI and Small Animal CT
Authors: Wang B , He W , Cvetkovic D , Chen L , Fan J , Ma C
Published: July 2016

Purpose:

The purpose of the study is to compare the volume measurement of subcutaneous tumors in mice with different imaging platforms, namely a GE MRI and a Sofie‐Biosciences small animal CT scanner.

Methods:

A549 human lung carcinoma cells and FaDu human head and neck squamous cell carcinoma cells were implanted subcutaneously into flanks of nude mice. Three FaDu tumors and three A549 tumors were included in this study. The MRI scans were done with a GE Signa 1.5 Tesla MR scanner using a fast T2‐weighted sequence (70mm FOV and 1.2mm slice thickness), while the CT scans were done with the CT scanner on a Sofie‐Biosciences G8 PET/CT platform dedicated for small animal studies (48mm FOV and 0.2mm slice thickness). Imaging contrast agent was not used in this study. Based on the DICOM images from MRI and CT scans, the tumors were contoured with Philips DICOM Viewer and the tumor volumes were obtained by summing up the contoured area and multiplied by the slice thickness.

Results:

The volume measurements based on the CT scans agree reasonably with that obtained with MR images for the subcutaneous tumors. The mean difference in the absolute tumor volumes between MRI‐ and CT‐based measurements was found to be −6.2% ± 1.0%, with the difference defined as (VMR – VCT)*100%/VMR. Furthermore, we evaluated the normalized tumor volumes, which were defined for each tumor as V/V0 where V0 stands for the volume from the first MR or CT scan. The mean difference in the normalized tumor volumes was found to be 0.10% ± 0.96%.

Conclusion:

Despite the fact that the difference between normal and abnormal tissues is often less clear on small animal CT images than on MR images, one can still obtain reasonable tumor volume information with the small animal CT scans for subcutaneous murine xenograft models.
SU‐G‐JeP4‐08: External and Internal Motion Assessments with Amplitude and Time Based Reconstruction and AveCT
Authors: Fogg P , Aland T , West M
Published: July 2016

Purpose:

To investigate the effects of external surrogate and tumour motion by observing the reconstructed phases and AveCT in an Amplitude and Time based 4DCT.

Methods:

Based on patient motion studies, Cos6 and sinusoidal motions were simulated as external surrogate and tumour motions in a motion phantom. The diaphragm and tumour motions may or may not display the same waveform therefore the same and different waveforms were programmed into the phantom, scanned and reconstructed based on Amplitude and Time. The AveCT and phases were investigated with these different scenarios. The AveCT phantom images were also compared with CBCT phantom images programmed with the same motions.

Results:

For the same surrogate and tumour sin motions, the phases (Amplitude and Time) and AveCT indicated similar motions based on the position of the BB at the slice and displayed contrast values respectively. For cos6 motions, due to the varied time the tumour spends at each position, the Amplitude and Time based phases differed. The AveCT images represented the actual tumour motions and the Time and Amplitude based phases were represented by the surrogate with varied times.

Conclusion:

Different external surrogate and tumour motions may result in different displayed image motions when observing the AveCT and reconstructed phases. During the 4DCT, the surrogate motion is readily available for observation of the amplitude and time of the diaphragm position. Following image reconstruction, the user may need to observe the AveCT in addition to the reconstructed phases to comprehend the time weightings of the tumour motion during the scan. This may also apply to 3D CBCT images where the displayed tumour position in the images is influenced by the long duration of the CBCT. Knowledge of the tumour motion represented by the greyscale of the AveCT may also assist in CBCT treatment beam verification matching.
SU‐G‐JeP4‐13: Continuous Intra‐Fractional Monitoring of the Prostate Using Dynamic KV Collimation and Tube Current Modulation
Authors: Parsons D , Robar J
Published: July 2016

Purpose:

The focus of this work is to improve the available kV image quality for continuous intra‐fraction monitoring of the prostate. This is investigated using a novel blade collimation system enabling modulated volume‐of‐interest (VOI) imaging of prostate fiducial markers.

Methods:

A four‐blade dynamic kV collimator was used to track a VOI during gantry rotation. Planar image quality was investigated as a function of collimator dimension, while maintaining the same dose to isocenter, for a 22.2 cm diameter cylindrical water phantom with a 9 mm diameter bone insert. A sample prostate anatomy was defined in the planning system, including three fiducial markers within the CTV. The VOI margin around each marker was set to be 2σ of the population covariance matrix characterizing prostate motion. DRRs were used to calculate the kV attenuation for each VOI as a function of angle. The optimal marker and tube current were determined using kV attenuation. Monte Carlo simulations were used to calculate the imaging dose to the phantom and MV scatter dose to the imaging panel.

Results:

Preliminary measurements show an increase in CNR by a factor of 1.3 with the VOI method, when decreasing from an 6×6 to 2×2 cm2 field. Attenuation calculations show a change in kV fluence at the detector by a factor of 21.6 with fiducial optimization; resultant tube current modulation increases maximum dose by a factor of 1.4 compared to no modulation. MV scatter contribution to the kV detector changes by approximately a factor of two over a complete gantry rotation.

Conclusion:

The dynamic collimation system allows single fiducial marker tracking at a very low dose, with reduction of scatter and improvement of image quality, compared to imaging the entire prostate. The approach is compatible with tube current modulation, which enables consistent image quality throughout the range of gantry rotation.

This project was funded by Varian Medical Systems.
SU‐G‐TeP4‐01: A High Resolution Pre‐Treatment VMAT QA Technique Based On EPID for Single Isocenter Multiple Mets Stereotactic Radiosurgery
Authors: Wu Q , Adamson J , Liang B , Liu B , Zhou F
Published: July 2016

Purpose:

For multiple mets radiosurgery, it is advantageous to use VMAT with a single isocenter for the ease in planning and efficiency in delivery. Insightful pre‐treatment QA for these cases is difficult to obtain because (1) target size is often small and the same order of magnitude as the detector size for commercial array based VMAT pre‐treatment QA devices; and furthermore (2) targets are located away from central axis where the array detectors are located. In this study, we present and validate an in‐house developed VMAT QA technique that is capable of addressing these challenges.

Methods:

The VMAT plan is delivered on a Varian Truebeam STX with HDMLC. The MV cine images are converted to portal dose (PD) after calibration. The gantry and MU index encoded in each image are used to extract a sub‐arc from the plan to compute corresponding PD. A 3D matrix is constructed with the 3rd axis representing gantry angle for subsequent γ‐analysis. The EPID has a resolution of 0.8×0.8 mm2 and field size up to 40×30 cm2. Measurements were performed for 21 arcs from 4 patients. Average(range) number of mets is 7(4–9), with volume of 0.36(0.01–1.39)cc. Varian's integrated PD was compared.

Results:

In PD analysis with 3%, 3mm, and 5% in threshold, pass rate of γ>1.0 is (99.6±0.3)%. Our EPID 3D analysis has the pass rate of (98.8±0.9)%, with additional criteria of 3° in angle‐to‐agreement. Projecting the 3D matrix along each axis, our analysis is reduced to 3 2D analyses, with one mimicking PD analysis at (99.0±0.9)%. Results on other planes are (99.5±0.4)% and (99.5±0.4)%, respectively. Additional criteria can be chosen to diagnose potential treatment abnormalities.

Conclusion:

We have developed an efficient EPID‐based QA technique for VMAT that has sufficient spatial and gantry angular resolution for use with single isocenter VMAT radiosurgery of multiple mets.
SU‐G‐TeP4‐05: An Evaluation of a Low Dose Rate (LDR) Prostate Brachytherapy Procedure Using a Failure Modes and Effects Analysis (FMEA)
Authors: Cheong S‐K , Kim J
Published: July 2016

Purpose:

The aim of the study is the application of a Failure Modes and Effects Analysis (FMEA) to access the risks for patients undergoing a Low Dose Rate (LDR) Prostate Brachytherapy Treatment.

Methods:

FMEA was applied to identify all the sub processes involved in the stages of identifying patient, source handling, treatment preparation, treatment delivery, and post treatment. These processes characterize the radiation treatment associated with LDR Prostate Brachytherapy. The potential failure modes together with their causes and effects were identified and ranked in order of their importance. Three indexes were assigned for each failure mode: the occurrence rating (O), the severity rating (S), and the detection rating (D). A ten‐point scale was used to score each category, ten being the number indicating most severe, most frequent, and least detectable failure mode, respectively. The risk probability number (RPN) was calculated as a product of the three attributes: RPN = O X S x D. The analysis was carried out by a working group (WG) at UPMC.

Results:

The total of 56 failure modes were identified including 32 modes before the treatment, 13 modes during the treatment, and 11 modes after the treatment. In addition to the protocols already adopted in the clinical practice, the prioritized risk management will be implanted to the high risk procedures on the basis of RPN score.

Conclusion:

The effectiveness of the FMEA method was established. The FMEA methodology provides a structured and detailed assessment method for the risk analysis of the LDR Prostate Brachytherapy Procedure and can be applied to other radiation treatment modes.
SU‐G‐TeP4‐06: An Integrated Application for Radiation Therapy Treatment Plan Directives, Management, and Reporting
Authors: Matuszak M , Anderson C , Lee C , Vineberg K , Green M , Younge K , Moran J , Mayo C
Published: July 2016

Purpose:

With electronic medical records, patient information for the treatment planning process has become disseminated across multiple applications with limited quality control and many associated failure modes. We present the development of a single application with a centralized database to manage the planning process.

Methods:

The system was designed to replace current functionalities of (i) static directives representing the physician intent for the prescription and planning goals, localization information for delivery, and other information, (ii) planning objective reports, (iii) localization and image guidance documents and (iv) the official radiation therapy prescription in the medical record. Using the Eclipse Scripting Application Programming Interface, a plug‐in script with an associated domain‐specific SQL Server database was created to manage the information in (i)–(iv). The system's user interface and database were designed by a team of physicians, clinical physicists, database experts, and software engineers to ensure usability and robustness for clinical use.

Results:

The resulting system has been fully integrated within the TPS via a custom script and database. Planning scenario templates, version control, approvals, and logic‐based quality control allow this system to fully track and document the planning process as well as physician approval of tradeoffs while improving the consistency of the data. Multiple plans and prescriptions are supported along with non‐traditional dose objectives and evaluation such as biologically corrected models, composite dose limits, and management of localization goals. User‐specific custom views were developed for the attending physician review, physicist plan checks, treating therapists, and peer review in chart rounds.

Conclusion:

A method was developed to maintain cohesive information throughout the planning process within one integrated system by using a custom treatment planning management application that interfaces directly with the TPS. Future work includes quantifying the improvements in quality, safety and efficiency that are possible with the routine clinical use of this system.

Supported in part by NIH‐P01‐CA‐059827
SU‐G‐TeP4‐14: Quality Control of Treatment Planning Using Knowledge‐Based Planning Across a System of Radiation Oncology Practices
Authors: Masi K , Ditman M , Marsh R , Dai J , Huberts M , Khadija M , Tatro D , Archer P , Matuszak M
Published: July 2016

Purpose:

There is potentially a wide variation in plan quality for a certain disease site, even for clinics located in the same system of hospitals. We have used a prostate‐specific knowledge‐based planning (KBP) model as a quality control tool to investigate the variation in prostate treatment planning across a network of affiliated radiation oncology departments.

Methods:

A previously created KBP model was applied to 10 patients each from 4 community‐based clinics (Clinics A, B, C, and D). The KBP model was developed using RapidPlan (Eclipse v13.5, Varian Medical Systems) from 60 prostate/prostate bed IMRT plans that were originally planned using an in‐house treatment planning system at the central institution of the community‐based clinics. The dosimetric plan quality (target coverage and normal‐tissue sparing) of each model‐generated plan was compared to the respective clinically‐used plan. Each community‐based clinic utilized the same planning goals to develop the clinically‐used plans that were used at the main institution.

Results:

Across all 4 clinics, the model‐generated plans decreased the mean dose to the rectum by varying amounts (on average, 12.5, 2.6, 4.5, and 2.7 Gy for Clinics A, B, C, and D, respectively). The mean dose to the bladder also decreased with the model‐generated plans (5.4, 2.3, 3.0, and 4.1 Gy, respectively). The KBP model also identified that target coverage (D95%) improvements were possible for for Clinics A, B, and D (0.12, 1.65, and 2.75%) while target coverage decreased by 0.72% for Clinic C, demonstrating potentially different trade‐offs made in clinical plans at different institutions.

Conclusion:

Quality control of dosimetric plan quality across a system of radiation oncology practices is possible with knowledge‐based planning. By using a quality KBP model, smaller community‐based clinics can potentially identify the areas of their treatment plans that may be improved, whether it be in normal‐tissue sparing or improved target coverage.

M. Matuszak has research funding for KBP from Varian Medical Systems
MO‐AB‐204‐03: Profile Development and IHE Process
Authors: Pauer C.
Published: July 2016

You've experienced the frustration: vendor A's device claims to work with vendor B's device, but the practice doesn't match the promise. Getting devices working together is the hidden art that Radiology and Radiation Oncology staff have to master. To assist with that difficult process, the Integrating the Healthcare Enterprise (IHE) effort was established in 1998, with the coordination of the Radiological Society of North America.

Integrating the Healthcare Enterprise (IHE) is a consortium of healthcare professionals and industry partners focused on improving the way computer systems interconnect and exchange information. This is done by coordinating the use of published standards like DICOM and HL7. Several clinical and operational IHE domains exist in the healthcare arena, including Radiology and Radiation Oncology. The ASTRO‐sponsored IHE Radiation Oncology (IHE‐RO) domain focuses on radiation oncology specific information exchange. This session will explore the IHE Radiology and IHE RO process for;

IHE solicitation process for new profiles.

Improving the way computer systems interconnect and exchange information in the healthcare enterprise

Supporting interconnectivity descriptions and proof of adherence by vendors

Testing and assuring the vendor solutions to connectivity problems.

Including IHE profiles in RFPs for future software and hardware purchases.

Learning Objectives:

Understand IHE role in improving interoperability in health care.

Understand process of profile development and implantation.

Understand how vendors prove adherence to IHE RO profiles.

S. Hadley, ASTRO Supported Activity
MO‐A‐201‐00: A Cliff's Notes Version of Proton Therapy
Authors: Kruse Jon
Published: July 2016

Proton therapy is a rapidly growing modality in the fight against cancer. From a high‐level perspective the process of proton therapy is identical to x‐ray based external beam radiotherapy. However, this course is meant to illustrate for x‐ray physicists the many differences between x‐ray and proton based practices.

Unlike in x‐ray therapy, proton dose calculations use CT Hounsfield Units (HU) to determine proton stopping power and calculate the range of a beam in a patient. Errors in stopping power dominate the dosimetric uncertainty in the beam direction, while variations in patient position determine uncertainties orthogonal to the beam path. Mismatches between geometric and range errors lead to asymmetric uncertainties, and so while geometric uncertainties in x‐ray therapy are mitigated through the use of a Planning Target Volume (PTV), this approach is not suitable for proton therapy. Robust treatment planning and evaluation are critical in proton therapy, and will be discussed in this course.

Predicting the biological effect of a proton dose distribution within a patient is also a complex undertaking. The proton therapy community has generally regarded the Radiobiological Effectiveness (RBE) of a proton beam to be 1.1 everywhere in the patient, but there are increasing data to suggest that the RBE probably climbs higher than 1.1 near the end of a proton beam when the energy deposition density increases. This lecture will discuss the evidence for variable RBE in proton therapy and describe how this is incorporated into current proton treatment planning strategies.

Finally, there are unique challenges presented by the delivery process of proton therapy. Many modern systems use a spot scanning technique which has several advantages over earlier scattered beam designs. However, the time dependence of the dose deposition leads to greater concern with organ motion than with scattered protons or x‐rays. Image guidance techniques in proton therapy may also differ from standard x‐ray approaches, due to equipment design or the desire to maximize efficiency within a high‐cost proton therapy treatment room. Differences between x‐ray and proton therapy delivery will be described.

Learning Objectives:

Understand how CT HU are calibrated to provide proton stopping power, and the sources of uncertainty in this process.

Understand why a PTV is not suitable for proton therapy, and how robust treatment planning and evaluation are used to mitigate uncertainties.

Understand the source and implications of variable RBE in proton therapy

Learn about proton specific challenges and approaches in beam delivery and image guidance

Jon Kruse has a research grant from Varian Medical Systems related to proton therapy treatment plannning.; J. Kruse, Jon Kruse has a research grant with Varian Medical Systems related to proton therapy planning.
MO‐A‐201‐01: A Cliff's Notes Version of Proton Therapy
Authors: Kruse J.
Published: July 2016

Proton therapy is a rapidly growing modality in the fight against cancer. From a high‐level perspective the process of proton therapy is identical to x‐ray based external beam radiotherapy. However, this course is meant to illustrate for x‐ray physicists the many differences between x‐ray and proton based practices.

Unlike in x‐ray therapy, proton dose calculations use CT Hounsfield Units (HU) to determine proton stopping power and calculate the range of a beam in a patient. Errors in stopping power dominate the dosimetric uncertainty in the beam direction, while variations in patient position determine uncertainties orthogonal to the beam path. Mismatches between geometric and range errors lead to asymmetric uncertainties, and so while geometric uncertainties in x‐ray therapy are mitigated through the use of a Planning Target Volume (PTV), this approach is not suitable for proton therapy. Robust treatment planning and evaluation are critical in proton therapy, and will be discussed in this course.

Predicting the biological effect of a proton dose distribution within a patient is also a complex undertaking. The proton therapy community has generally regarded the Radiobiological Effectiveness (RBE) of a proton beam to be 1.1 everywhere in the patient, but there are increasing data to suggest that the RBE probably climbs higher than 1.1 near the end of a proton beam when the energy deposition density increases. This lecture will discuss the evidence for variable RBE in proton therapy and describe how this is incorporated into current proton treatment planning strategies.

Finally, there are unique challenges presented by the delivery process of proton therapy. Many modern systems use a spot scanning technique which has several advantages over earlier scattered beam designs. However, the time dependence of the dose deposition leads to greater concern with organ motion than with scattered protons or x‐rays. Image guidance techniques in proton therapy may also differ from standard x‐ray approaches, due to equipment design or the desire to maximize efficiency within a high‐cost proton therapy treatment room. Differences between x‐ray and proton therapy delivery will be described.

Learning Objectives:

Understand how CT HU are calibrated to provide proton stopping power, and the sources of uncertainty in this process.

Understand why a PTV is not suitable for proton therapy, and how robust treatment planning and evaluation are used to mitigate uncertainties.

Understand the source and implications of variable RBE in proton therapy

Learn about proton specific challenges and approaches in beam delivery and image guidance

Jon Kruse has a research grant from Varian Medical Systems related to proton therapy treatment plannning.; J. Kruse, Jon Kruse has a research grant with Varian Medical Systems related to proton therapy planning.
MO‐A‐BRC‐01: TG167 Report ‐ Introduction
Authors: Nath R.
Published: July 2016

Although a multicenter, Phase III, prospective, randomized trial is the gold standard for evidence‐based medicine, it is rarely used to evaluate innovative radiotherapy devices because of many practical and ethical reasons. It is usually sufficient to compare the dose distributions and dose rates for determining equivalence of the innovative device to an existing one. Thus, quantitative evaluation of the dosimetric characteristics of an innovative brachytherapy device or application is a critical part in which physicists are actively involved. The physicist's role, along with physician colleagues, in this process is highlighted for innovative products or applications and includes evaluation of 1) dosimetric considerations for clinical implementation (including calibrations, dose calculations, and radiobiological aspects) to comply with existing societal dosimetric prerequisites for sources in routine clinical use, 2) risks and benefits from regulatory and safety perspectives, and 3) resource assessment and preparedness. Further, calibration methods should be traceable to a primary standards dosimetry laboratory such as NIST in the U.S. or to other primary standards dosimetry laboratory located elsewhere. Clinical users should follow standards as approved by their country's regulatory agencies that approved such a brachytherapy device. Integration of this system into the medical source calibration infrastructure of secondary standard dosimetry laboratories such as the ADCLs is encouraged before a source is introduced into widespread routine clinical use. The AAPM and GEC‐ESTRO have developed guidelines for the safe and consistent application of brachytherapy using innovative brachytherapy devices and applications. The current report covers regulatory approvals, calibration, dose calculations, radiobiological issues, and overall safety concerns that should be addressed during the commissioning stage preceding clinical use. These guidelines are based on review of requirements of the U.S. NRC, FDA, Department of Transportation, International Electrotechnical Commission Medical Electrical Equipment Standard 60601, European Commission for CE Marking, and institutional review boards and radiation safety committees.

Learning Objectives:

Understand the necessary dosimetric considerations for clinical implementation (including calibrations, dose calculations, and radiobiological aspects) to comply with existing societal dosimetric prerequisites for sources in routine clinical use.

Evaluate risks and benefits from regulatory and safety perspectives.

Identify necessary resources and create a plan for clinical introduction of innovative brachytherapy device or applications.

Consultant for Theragenics Corp.; R. Nath, Consultant to Theragenics Corp.
MO‐A‐BRB‐00: TG191: Clinical Use of Luminescent Dosimeters
Authors: Kry Stephen
Published: July 2016

This presentation will highlight the upcoming TG‐191 report: Clinical Use of Luminescent Dosimeters. Luminescent dosimetry based on TLD and OSLD is a practical, accurate, and precise technique for point dosimetry in medical physics applications. The charges of Task Group 191 were to detail the methodologies for practical and optimal luminescent dosimetry in a clinical setting. This includes (1) To review the variety of TLD/OSL materials available, including features and limitations of each. (2) To outline the optimal steps to achieve accurate and precise dosimetry with luminescent detectors and to evaluate the uncertainty induced when less rigorous procedures are used. (3) To develop consensus guidelines on the optimal use of luminescent dosimeters for clinical practice. (4) To develop guidelines for special medically relevant uses of TLDs/OSLs (e.g., mixed field i.e. photon/neutron dosimetry, particle beam dosimetry, skin dosimetry). While this report provides general guidelines for arbitrary TLD and OSLD processes, the report, and therefore this presentation, provide specific guidance for TLD‐100 (LiF:Ti,Mg) and nanoDot (Al2O3:C) dosimeters because of their prevalence in clinical practice.

Learning Objectives:

Understand the available dosimetry systems, and basic theory of their operation

Understand the range of dose determination methodologies and the uncertainties associated with them

Become familiar with special considerations for TLD/OSLD relevant for special clinical situations

Learn recommended commissioning and QA procedures for these dosimetry systems.