bluuebunny/crossref_metadata_2025 huggingface dataset:
SU‐F‐I‐53: Coded Aperture Coherent Scatter Spectral Imaging of the Breast: A Monte Carlo Evaluation of Absorbed Dose
Authors: Morris R , Lakshmanan M , Fong G , Kapadia A , Greenberg J
Published: July 2016

Purpose:

Coherent scatter based imaging has shown improved contrast and molecular specificity over conventional digital mammography however the biological risks have not been quantified due to a lack of accurate information on absorbed dose. This study intends to characterize the dose distribution and average glandular dose from coded aperture coherent scatter spectral imaging of the breast. The dose deposited in the breast from this new diagnostic imaging modality has not yet been quantitatively evaluated. Here, various digitized anthropomorphic phantoms are tested in a Monte Carlo simulation to evaluate the absorbed dose distribution and average glandular dose using clinically feasible scan protocols.

Methods:

Geant4 Monte Carlo radiation transport simulation software is used to replicate the coded aperture coherent scatter spectral imaging system. Energy sensitive, photon counting detectors are used to characterize the x‐ray beam spectra for various imaging protocols. This input spectra is cross‐validated with the results from XSPECT, a commercially available application that yields x‐ray tube specific spectra for the operating parameters employed. XSPECT is also used to determine the appropriate number of photons emitted per mAs of tube current at a given kVp tube potential. With the implementation of the XCAT digital anthropomorphic breast phantom library, a variety of breast sizes with differing anatomical structure are evaluated. Simulations were performed with and without compression of the breast for dose comparison.

Results:

Through the Monte Carlo evaluation of a diverse population of breast types imaged under real‐world scan conditions, a clinically relevant average glandular dose for this new imaging modality is extrapolated.

Conclusion:

With access to the physical coherent scatter imaging system used in the simulation, the results of this Monte Carlo study may be used to directly influence the future development of the modality to keep breast dose to a minimum while still maintaining clinically viable image quality.
SU‐F‐I‐63: Relaxation Times of Lipid Resonances in NAFLD Animal Model Using Enhanced Curve Fitting
Authors: Song K‐H , Yoo C‐H , Lim S‐I , Choe B‐Y
Published: July 2016

Purpose:

The objective of this study is to evaluate the relaxation time of methylene resonance in comparison with other lipid resonances.

Methods:

The examinations were performed on a 3.0T MRI scanner using a four‐channel animal coil. Eight more Sprague‐Dawley rats in the same baseline weight range were housed with ad libitum access to water and a high‐fat (HF) diet (60% fat, 20% protein, and 20% carbohydrate). In order to avoid large blood vessels, a voxel (0.8×0.8×0.8 cm3) was placed in a homogeneous area of the liver parenchyma during free breathing. Lipid relaxations in NC and HF diet rats were estimated at a fixed repetition time (TR) of 6000 msec, and multi echo time (TEs) of 40–220 msec. All spectra for data measurement were processed using the Advanced Method for Accurate, Robust, and Efficient Spectral (AMARES) fitting algorithm of the Java‐based Magnetic Resonance User Interface (jMRUI) package.

Results:

The mean T2 relaxation time of the methylene resonance in normal‐chow diet was 37.1 msec (M0, 2.9±0.5), with a standard deviation of 4.3 msec. The mean T2 relaxation time of the methylene resonance was 31.4 msec (M0, 3.7±0.3), with a standard deviation of 1.8 msec. The T2 relaxation times of methylene protons were higher in normal‐chow diet rats than in HF rats (p<0.05), and the extrapolated M0 values were higher in HF rats than in NC rats (p<0.005). The excellent linear fit with R2>0.9971 and R2>0.9987 indicates T2 relaxation decay curves with mono‐exponential function.

Conclusion:

In in vivo, a sufficient spectral resolution and a sufficiently high signal‐to‐noise ratio (SNR) can be achieved, so that the data measured over short TE values can be extrapolated back to TE = 0 to produce better estimates of the relative weights of the spectral components. In the short term, treating the effective decay rate as exponential is an adequate approximation.
SU‐F‐I‐68: Longitudinal Neurochemical Changes On Rat Prefrontal Cortex of Single Prolonged Stress Model by Using Proton Magnetic Resonance Spectroscopy at 9.4T
Authors: Lim S‐I , Song K‐H , Yoo C‐H , Woo D‐C , Choe B‐Y
Published: July 2016

Purpose:

Single prolonged stress (SPS) is an animal model of posttraumatic stress disorder (PTSD). However, it has not been known how PTSD develops from the first exposure to traumatic events and neurochemical differences between acute/single stress and PTSD‐triggering stress. Therefore, the object of this study is to determine time‐dependent neurochemical changes in prefrontal cortex (PFC) of rats using in vivo proton magnetic resonance spectroscopy (1H‐MRS).

Methods:

Male Sprague‐Dawley rats (n=14; body weight=200–220g) were used. The SPS protocol was used in this study. Rats were restrained for 2h and then immediately forced to swim for 20min in water (20–24 Celsius). After a 15‐min recuperation period, rats were exposed to ether (using a desiccator) until general anesthesia occurred (<5min). In vivo proton MRS was performed 30min before the SPS (Base), approximately 10min after the SPS (D+0), 3 (D+3) and 7 (D+7) days after SPS to investigate time‐dependent changes on metabolites levels in the PFC. Acquisition of in vivo MRS spectra and MRI was conducted at the four time points using 9.4 T Agilent Scanner. Concentration of metabolites was quantified by LCModel.

Results:

Statistical significance was analyzed using one‐way ANOVA with post hoc Tukey HSD tests to assess the metabolite changes in the PFC. The SPS resulted in significant stress‐induced differences for 7 days in glutamine (F(3,52)=6.750, P=0.001), choline‐containing compounds (F(3,52)=16.442, P=0.000), glutamine/glutamate concentrations (F(3,52)=7.352, P=0.000).

Conclusion:

PTSD in human is associated with decreased neuronal activity in the PFC. In this study, SPS altered total choline, glutamine levels but not NAA levels in the PFC of the rats. Therefore, for the three stressors and quiescent period of seven days, SPS attenuated excitatory tone and membrane turnover but did not affect neural integrity in the PFC.
SU‐F‐I‐69: Absorbed Dose Estimation for a Commercially Available MicroCT Scanner with Various Filtration Techniques
Authors: Lau A , Liu H , Ren L , Ahmad S , Chen Y
Published: July 2016

Purpose:

To quantify the simulated mean absorbed dose per technique (cGy/mAs) from a commercially available microCT scanner using various filtration techniques.

Methods:

Monte Carlo simulations using the Geant4 toolkit (version 10) was used utilizing the standard electromagnetic physics model. The Quantum FX microCT scanner (PerkinElmer, Waltham, MA) was modeled incorporating measured energy spectra and spatial dimensions of nominal source‐to‐object (SOD) distances. The energy distribution was measured using a spectrometer (X‐123CdTe, Amptek Inc., Bedford, USA) for the 90 kVp X‐ray beams with various filters (including no filter, 1 mm, 2 mm, 3 mm, 4 mm Al and 0.2 mm Cu + 2.5 mm Al). The SOD was set to 154 mm, 104 mm, and 52 mm. A total of 10 million incident particles were processed per simulation. Cutout value was set to 0.1 mm for both photon and electron. The mean dose absorbed (cGy/per incident particle) in a PMMA phantom (length of 2 cm and radius of 3 cm) were recorded. Exposure measurements were taken using a Radcal 9095 system with a protocol of 90 kVp, 200 µA, and ∼12 s beam‐On time for the various filters.

Results:

The mean absorbed dose per mAs for various filtrations and different SOD setups indicated that the dose decreased as the SOD increased and as the amount of filtration increased. For a given SOD, the dose was reduced by as much as ∼13.7% by varying the filter (from 0.2 mm Cu + 2.5 mm Al to no filter). The maximum dose was found to be 0.39 cGy/mAs (SOD of 5.196 cm, no filter) while the minimum dose value was 0.077 cGy/mAs (SOD of 15.4 cm, .2mm Cu + 2mm Al filter).

Conclusion:

This study estimates easily the mean dose for objects scanned with a microCT scanner with different filtration.
SU‐F‐I‐71: Fetal Protection During Fluoroscopy: To Shield Or Not to Shield?
Authors: Joshi S , Vanderhoek M
Published: July 2016

Purpose:

Lead aprons are routinely used to shield the fetus from radiation during fluoroscopically guided interventions (FGI) involving pregnant patients. When placed in the primary beam, lead aprons often reduce image quality and increase fluoroscopic radiation output, which can adversely affect fetal dose. The purpose of this work is to identify an effective and practical method to reduce fetal dose without affecting image quality.

Methods:

A pregnant patient equivalent abdominal phantom is set on the table along with an image quality test object (CIRS model 903) representing patient anatomy of interest. An ion chamber is positioned at the x‐ray beam entrance to the phantom, which is used to estimate the relative fetal dose. For three protective methods, image quality and fetal dose measurements are compared to baseline (no protection):1. Lead apron shielding the entire abdomen2. Lead apron shielding part of the abdomen, including the fetus 3. Narrow collimation such that fetus is excluded from the primary beam

Results:

With lead shielding the entire abdomen, the dose is reduced by 80% relative to baseline along with a drastic deterioration of image quality. With lead shielding only the fetus, the dose is reduced by 65% along with complete preservation of image quality, since the image quality test object is not shielded. However, narrow collimation results in 90% dose reduction and a slight improvement of image quality relative to baseline.

Conclusion:

The use of narrow collimation to protect the fetus during FGI is a simple and highly effective method that simultaneously reduces fetal dose and maintains sufficient image quality. Lead aprons are not as effective at fetal dose reduction, and if placed improperly, they can severely degrade image quality. Future work aims to investigate a wider variety of fluoroscopy systems to confirm these results across many different system geometries.
SU‐F‐I‐72: Evaluation of the Ancillary Lead Shielding for Optimizing Radiation Protection in the Interventional Radiology Department
Authors: Tonkopi E , Lightfoot C , LeBlanc E
Published: July 2016

Purpose:

The rising complexity of interventional fluoroscopic procedures has resulted in an increase of occupational radiation exposures in the interventional radiology (IR) department. This study assessed the impact of ancillary shielding on optimizing radiation protection for the IR staff.

Methods:

Scattered radiation measurements were performed in two IR suites equipped with Axiom Artis systems (Siemens Healthcare, Erlangen, Germany) installed in 2006 and 2010. Both rooms had suspended ceiling‐mounted lead‐acrylic shields of 75×60 cm (Mavig, Munich, Germany) with lead equivalency of 0.5 mm, and under‐table drapes of 70×116 cm and 65×70 cm in the newer and the older room respectively. The larger skirt can be wrapped around the table's corner and in addition the newer suite had two upper shields of 25×55 cm and 25×35 cm. The patient was simulated by 30 cm of acrylic, air kerma rate (AKR) was measured with the 180cc ionization chamber (AccuPro Radcal Corporation, Monrovia, CA, USA) at different positions. The ancillary shields, x‐ray tube, image detector, and table height were adjusted by the IR radiologist to simulate various clinical setups. The same exposure parameters were used for all acquisitions. AKR measurements were made at different positions relative to the operator.

Results:

The AKR measurements demonstrated 91–99% x‐ray attenuation by the drapes in both suites. The smaller size of the under‐table skirt and absence of the side‐drapes in the older room resulted in a 20–50 fold increase of scattered radiation to the operator. The mobile suspended lead‐acrylic shield reduced AKR by 90–94% measured at 150–170 cm height. The recommendations were made to replace the smaller under‐table skirt and to use the ceiling‐mounted shields for all IR procedures.

Conclusion:

The ancillary shielding may significantly affect radiation exposure to the IR staff. The use of suspended ceiling‐mounted shields is especially important for reduction of interventional radiologists’ cranial radiation.
SU‐F‐I‐73: Surface Dose from KV Diagnostic Beams From An On‐Board Imager On a Linac Machine Using Different Imaging Techniques and Filters
Authors: Ali I , Hossain S , Syzek E , Ahmad S
Published: July 2016

Purpose:

To quantitatively investigate the surface dose deposited in patients imaged with a kV on‐board‐imager mounted on a radiotherapy machine using different clinical imaging techniques and filters.

Methods:

A high sensitivity photon diode is used to measure the surface dose on central‐axis and at an off‐axis‐point which is mounted on the top of a phantom setup. The dose is measured for different imaging techniques that include: AP‐Pelvis, AP‐Head, AP‐Abdomen, AP‐Thorax, and Extremity. The dose measurements from these imaging techniques are combined with various filtering techniques that include: no‐filter (open‐field), half‐fan bowtie (HF), full‐fan bowtie (FF) and Cu‐plate filters. The relative surface dose for different imaging and filtering techniques is evaluated quantiatively by the ratio of the dose relative to the Cu‐plate filter.

Results:

The lowest surface dose is deposited with the Cu‐plate filter. The highest surface dose deposited results from open fields without filter and it is nearly a factor of 8–30 larger than the corresponding imaging technique with the Cu‐plate filter. The AP‐Abdomen technique delivers the largest surface dose that is nearly 2.7 times larger than the AP‐Head technique. The smallest surface dose is obtained from the Extremity imaging technique. Imaging with bowtie filters decreases the surface dose by nearly 33% in comparison with the open field. The surface doses deposited with the HF or FF‐bowtie filters are within few percentages. Image‐quality of the radiographic images obtained from the different filtering techniques is similar because the Cu‐plate eliminates low‐energy photons. The HF‐ and FF‐bowtie filters generate intensity‐gradients in the radiographs which affects image‐quality in the different imaging technique.

Conclusion:

Surface dose from kV‐imaging decreases significantly with the Cu‐plate and bowtie‐filters compared to imaging without filters using open‐field beams. The use of Cu‐plate filter does not affect image‐quality and may be used as the default in the different imaging techniques.
SU‐F‐I‐77: Radiation Dose in Cardiac Catheterization Procedures: Impact of a Systematic Reduction in Pulsed Fluoroscopy Frame Rate
Authors: Schultz C , Dixon S
Published: July 2016

Purpose:

To evaluate whether one small systematic reduction in fluoroscopy frame rate has a significant effect on the total air kerma and/or dose area product for diagnostic and interventional cardiac catheterization procedures.

Methods:

The default fluoroscopy frame rate (FFR) was lowered from 15 to 10 fps in 5 Siemens™ Axiom Artis cardiac catheterization labs (CCL) on July 1, 2013. A total of 7212 consecutive diagnostic and interventional CCL procedures were divided into two study groups: 3602 procedures from 10/1/12 –6/30/13 with FFR of 15 fps; and 3610 procedures 7/1/13 – 3/31/14 at 10 fps. For each procedure, total air kerma (TAK), fluoroscopy skin dose (FSD), total/fluoroscopy dose area products (TAD, FAD), and total fluoroscopy time (FT) were recorded. Patient specific data collected for each procedure included: BSA, sex, height, weight, interventional versus diagnostic; and elective versus emergent.

Results:

For pre to post change in FFR, each categorical variable was compared using Pearson's Chi‐square test, Odds ratios and 95% confidence intervals. No statistically significant difference in BSA, height, weight, number of interventional versus diagnostic, elective versus emergent procedures was found between the two study groups. Decreasing the default FFR from 15 fps to 10 fps in the two study groups significantly reduced TAK from 1305 to 1061 mGy (p<0.0001), FSD from 627 to 454 mGy (p<0.0001), TAD from 8681 to 6991 uGy × m2(p<0.0001), and FAD from 4493 to 3297 uGy × m2(p<0.0001). No statistically significant difference in FT was noted. Clinical image quality was not analyzed, and reports of noticeable effects were minimal. From July 1, 2013 to date, the default FFR has remained 10 fps.

Conclusion:

Reducing the FFR from 15 to 10 fps significantly reduced total air kerma and dose area product which may decrease risk for potential radiation‐induced skin injuries and improve patient outcomes.
SU‐F‐I‐78: Design of Diagnostic Multileaf Collimator Based On the Monte Carlo Simulation for Dose Reduction of Diagnostic Radiography
Authors: Han S , Ji Y , Kim K , Choi S , Jung H , Park S
Published: July 2016

Purpose:

A diagnostics Multileaf Collimator (MLC) was designed for diagnostic radiography dose reduction. Monte Carlo simulation was used to evaluate efficiency of shielding material for producing leaves of Multileaf collimator.

Material & Methods:

The general radiography unit (Rex‐650R, Listem, Korea) was modeling with Monte Carlo simulation (MCNPX, LANL, USA) and we used SRS‐78 program to calculate the energy spectrum of tube voltage (80, 100, 120 kVp). The shielding materials was SKD 11 alloy tool steel that is composed of 1.6% carbon(C), 0.4% silicon (Si), 0.6% manganese (Mn), 5% chromium (Cr), 1% molybdenum (Mo), and vanadium (V). The density of it was 7.89 g/m3. We simulated leafs diagnostic MLC using SKD 11 with general radiography unit. We calculated efficiency of diagnostic MLC using tally6 card of MCNPX depending on energy.

Results:

The diagnostic MLC consisted of 25 individual metal shielding leaves on both sides, with dimensions of 10 × 0.5 × 0.5 cm3. The leaves of MLC were controlled by motors positioned on both sides of the MLC. According to energy (tube voltage), the shielding efficiency of MLC in Monte Carlo simulation was 99% (80 kVp), 96% (100 kVp) and 93% (120 kVp).

Conclusion:

We certified efficiency of diagnostic MLC fabricated from SKD11 alloy tool steel. Based on the results, the diagnostic MLC was designed. We will make the diagnostic MLC for dose reduction of diagnostic radiography.
SU‐F‐J‐03: Treatment Planning for Laser Ablation Therapy in Presence of Heterogeneous Tissue: A Retrospective Study
Authors: Madankan R , MacLellan C , Fahrenholtz S , Weinberg J , Rao G , Hazle J , Stafford R , Fuentes D
Published: July 2016

Purpose:

MR guided Laser Induced Thermal Therapy (MRgLITT) is an effective technique for cancerous tissue destruction in brain. Precise modeling of the thermal ablation procedure is important for treatment planning for MRgLITT. Physical properties of target tissue such as optical attenuation (µ) highly affect the outcome of thermal ablation modeling. Hence to ensure accuracy of modeling scheme, it is crucial to precisely estimate patient specific heterogeneity in these parameters.

Methods:

A steady‐state Bioheat model is used for simulation of temperature field over the heterogeneous target tissue. Physical properties are assessed from training based on previously recorded MRTI datasets. In detail, a cost function is defined based on the difference between the Bioheat model temperature predictions and MRTI measurements. Minimizing this cost function results in optimal values for physical properties of each tissue type. Optical attenuation coefficients (µ) are the dominant sensitivity and are optimized in this work. Nominal values of other parameters are used. Population averages of the optimal values of µ are then used in Bioheat model for temperature assessment in future patients. Performance of these predictions is then verified using Dice similarity index.

Results:

Results provide a comprehensive analysis of the effect of using heterogeneous tissue segmentations on performance of LITT mathematical simulation. Optimal values of µ coefficients range between 100 m−1 and 200 m−1. This corresponds with obtained values in literature. The mean and median of Dice similarity index while using optimal values of optical attenuation coefficients is 0.8022 and 0.8225, respectively.

Conclusion:

Calibration of mathematical modeling outcomes with clinical MRTI data provides a better understanding about the parameters of the Bioheat equation and consequently provides a more confident thermal dose assessment than either approach alone. Results demonstrate that modeling predictions are accurate in a‐priori prediction of thermal dose and may be useful in planning the procedure.
SU‐F‐J‐06: Optimized Patient Inclusion for NaF PET Response‐Based Biopsies
Authors: Roth A , Harmon S , Perk T , Jeraj R
Published: July 2016

Purpose:

A method to guide mid‐treatment biopsies using quantitative [F‐18]NaF PET/CT response is being investigated in a clinical trial. This study aims to develop methodology to identify patients amenable to mid‐treatment biopsy based on pre‐treatment imaging characteristics.

Methods:

35 metastatic prostate cancer patients had NaF PET/CT scans taken prior to the start of treatment and 9–12 weeks into treatment. For mid‐treatment biopsy targeting, lesions must be at least 1.5 cm3 and located in a clinically feasible region (lumbar/sacral spine, pelvis, humerus, or femur). Three methods were developed based on number of lesions present prior to treatment: a feasibility‐restricted method, a location‐restricted method, and an unrestricted method. The feasibility restricted method only utilizes information from lesions meeting biopsy requirements in the pre‐treatment scan. The unrestricted method accounts for all lesions present in the pre‐treatment scan. For each method, optimized classification cutoffs for candidate patients were determined.

Results:

13 of the 35 patients had enough lesions at the mid‐treatment for biopsy candidacy. Of 1749 lesions identified in all 35 patients at mid‐treatment, only 9.8% were amenable to biopsy. Optimizing the feasibility‐restricted method required 4 lesions at pre‐treatment meeting volume and region requirements for biopsy, resulting patient identification sensitivity of 0.8 and specificity of 0.7. Of 6 false positive patients, only one patient lacked lesions for biopsy. Restricting for location alone showed poor results (sensitivity 0.2 and specificity 0.3). The optimized unrestricted method required patients have at least 37 lesions in pretreatment scan, resulting in a sensitivity of 0.8 and specificity of 0.8. There were 5 false positives, only one lacked lesions for biopsy.

Conclusion:

Incorporating the overall pre‐treatment number of NaF PET/CT identified lesions provided best prediction for identifying candidate patients for mid‐treatment biopsy. This study provides validity for prediction‐based inclusion criteria that can be extended to various clinical trial scenarios.

Funded by Prostate Cancer Foundation
SU‐F‐J‐07: Evaluating the Adequacy of Biopsy Specimens for Genetic Signature Assessment by Measuring the Metabolic Activity in Specimens Obtained Under 18F‐FDG PET/CT Guidance
Authors: Fanchon L , Russell J , Dogan S , Carlin S , Pinker‐Domenig K , Yorke E , Schmidtlein C. Ross , Fujisawa S , Manova‐Todorova K , Zanzonico P , Deasy J O , Humm J L , Solomon S , Kirov A S
Published: July 2016

Purpose:

Genetic profiling of biopsied tissue is the basis for personalized cancer therapy. However biopsied materials may not contain sufficient amounts of DNA needed for analysis. We propose a method to determine the adequacy of specimens for performing genetic profiling by quantifying metabolic activity.

Methods:

We measured the response of two radiation detectors to the activity contained in the minimum amount of tumor cells needed for genetic profiling in biopsy specimens obtained under 2‐deoxy‐2‐(18F)fluoro‐D‐glucose (18F‐FDG) PET/CT guidance. The expected tumor cell concentration in biopsy specimens was evaluated from the amount of DNA needed (∼100 µg) and the number of pathology sections typically used for the analysis. The average 18F‐FDG uptake per cell was measured by incubating KPC‐4662 pancreatic tumor cells and HT‐29 colorectal adenocarcinoma tumor cells in 18F‐FDG containing solution (activity concentrations between 0.0122 and 1.51 MBq/mL and glucose concentrations of 3.1 and 1 g/L) for 1 to 1.75 hours and then measuring the activity of a known number of cells. Measurements of surrogate specimens obtained using 18G needle biopsies of gels containing these cells in expected concentrations (∼104 µL−1) were performed using an autoradiography CCD based device (up to 20 min exposure) and a scintillation well counter (∼1 min measurements) about 3 and 5 hours after the end of incubation respectively.

Results:

At start of autoradiography there were between 0.16 and 1.5 18F‐FDG molecules/cell and between 1.14 and 5.43×107 18F‐FDG molecules/mL. For the scintillation well counter, sample to minimum‐detectable‐count rate ratios were greater than 7 and the counting error was less than 25% for ≤80 s measurement times. Images of the samples were identifiable on the autoradiograph for ∼10 min and longer exposure times.

Conclusion:

Scintillation well counter measurements and CCD based autoradiography have adequate sensitivity to detect the tumor burden needed for genetic profiling in 18G core needle biopsies.

Supported in part through the NIH/NCI Cancer Center Support Grant P30 CA008748 and by a sponsored research agreement with Biospace Lab S.A.
SU‐F‐J‐09: Radioactive Seed Localization for Breast Lumpectomy ‐ Towards Optimization
Authors: Aima M , Viscariello N , Patton T , Bednarz B
Published: July 2016

Purpose:

The aim of this work is to propose a method to optimize radioactive source localization (RSL) for non‐palpable breast cancer surgery. RSL is commonly used as a guiding technique during surgery for excision of non‐palpable tumors. A collimated hand‐held detector is used to localize radioactive sources implanted in tumors. Incisions made by the surgeon are based on maximum observed detector counts, and tumors are subsequently resected based on an arbitrary estimate of the counts expected at the surgical margin boundary. This work focuses on building a framework to predict detector counts expected throughout the procedure to improve surgical margins.

Methods:

A gamma detection system called the Neoprobe GDS was used for this work. The probe consists of a cesium zinc telluride crystal and a collimator. For this work, an I‐125 Best Medical model 2301 source was used. The source was placed in three different phantoms, a PMMA, a Breast (25%‐ glandular tissue/75%‐ adipose tissue) and a Breast (75‐25) phantom with a backscatter thickness of 6 cm. Counts detected by the probe were recorded with varying amounts of phantom thicknesses placed on top of the source. A calibration curve was generated using MATLAB based on the counts recorded for the calibration dataset acquired with the PMMA phantom.

Results:

The observed detector counts data used as the validation set was accurately predicted to within ±3.2%, ±6.9%, ±8.4% for the PMMA, Breast (75‐25), Breast (25–75) phantom respectively. The average difference between predicted and observed counts was −0.4%, 2.4%, 1.4% with a standard deviation of 1.2 %, 1.8%, 3.4% for the PMMA, Breast (75‐25), Breast (25–75) phantom respectively.

Conclusion:

The results of this work provide a basis for characterization of a detector used for RSL. Counts were predicted to within ±9% for three different phantoms without the application of a density correction factor.
SU‐F‐J‐10: Sliding Mode Control of a SMA Actuated Active Flexible Needle for Medical Procedures
Authors: Podder T
Published: July 2016

Purpose:

In medical interventional procedures such as brachytherapy, ablative therapies and biopsy precise steering and accurate placement of needles are very important for anatomical obstacle avoidance and accurate targeting. This study presents the efficacy of a sliding mode controller for Shape Memory Alloy (SMA) actuated flexible needle for medical procedures.

Methods:

Second order system dynamics of the SMA actuated active flexible needle was used for deriving the sliding mode control equations. Both proportional‐integral‐derivative (PID) and adaptive PID sliding mode control (APIDSMC) algorithms were developed and implemented. The flexible needle was attached at the end of a 6 DOF robotic system. Through LabView programming environment, the control commands were generated using the PID and APIDSMC algorithms. Experiments with artificial tissue mimicking phantom were performed to evaluate the performance of the controller. The actual needle tip position was obtained using an electromagnetic (EM) tracking sensor (Aurora, NDI, waterloo, Canada) at a sampling period of 1ms. During experiment, external disturbances were created applying force and thermal shock to investigate the robustness of the controllers.

Results:

The root mean square error (RMSE) values for APIDSMC and PID controllers were 0.75 mm and 0.92 mm, respectively, for sinusoidal reference input. In the presence of external disturbances, the APIDSMC controller showed much smoother and less overshooting response compared to that of the PID controller.

Conclusion:

Performance of the APIDSMC was superior to the PID controller. The APIDSMC was proved to be more effective controller in compensating the SMA uncertainties and external disturbances with clinically acceptable thresholds.
SU‐F‐J‐12: Dosimetrical Characteristics of a 2.5 MV Megavoltage Photon Beam
Authors: Anamalayil S , Liu H , Kim M , Zhu T
Published: July 2016

Purpose:

To evaluate the accuracy of modeling scatter factor (SF) and primary off‐axis ratio (POAR) for 2.5 MV megavoltage photon beams using an empirical model, which can be used as a dose calculation model for low energy EPID imaging.

Methods:

Scatter photon parameters were calculated for 2.5 MV photon beam from a Varian TrueBeam by fitting the product of depth dose, PDD, and the phantom scatter factor, Sp, for a range of square field sizes between 2 and 40 cm and depths between 0 and 30 cm. The model is then applied to off‐axis profiles measured for a slit field (3cm ×35 cm) for 5 depths: 0.6, 5, 10, and 20, 30 cm. Primary off‐axis ratio (POAR) values were determined based on the fitting to data using the empirical model.

Results:

The fitting to PDD*Sp has a maximum error of 14%, mostly near surface, where backscattering of photons dominate and has a standard deviation of 4.7%. The attenuation coefficient and beam‐hardening coefficient of the beam is determined to be 0.095 1/cm and 0.0038 1/cm, respectively. POAR for 2.5 MV has a peak in the center, corresponding to a beam without sufficient material to flatten the beam.

Conclusion:

This work illustrates a deficiency of the current empirical model to fit SF for a 2.5 MV photon beams. Most of the errors are near the surface region and an improved model that incorporate better modeling of backscattering can be developed to improve the model accuracy.
SU‐F‐J‐13: Choosing An IMRT Technique in the Treatment of Head and Neck Cancer with Daily Localization Uncertainties
Authors: Lin T , Wang L , Galloway T , Ma C
Published: July 2016

Purpose:

Head and Neck cancer treatment with IMRT/VMAT has two choices: split‐filed IMRT(SFI), in which the LAN is treated with a separate anterior field and the extended whole‐field IMRT(WFI) in which LAN is included with the IMRT/VMAT field. This study shows that under the same dose limit criteria, choosing the technique becomes a critical issue if daily localization and immobilization altered the dose distribution.

Methods:

Nine common head‐and‐neck cancer cases were chosen to illustrate how the daily localization and immobilization uncertainties affect to choose between SFI and WFI. Both SFI and WFI at upper target coverage were generated with VMAT. For each case, the same planning criteria were applied to the target and critical structures; therefore, similar target coverage and dose falloff can be observed in both techniques. Thirty days of kV cone beam CT(CBCT) images on each case were also delineated with contralateral and ipsilateral target as well as larynx as critical structure. About 300 CBCT images with daily delivered doses were analyzed and compared in a form of dose‐volume histograms.

Results:

While both plans for SFI and WFI with VMAT planning utilized and meet the criteria of D95>prescription dose and for not‐involved larynx with mean dose <35Gy and V55<10%, the daily localization and immobilization has a great contribution to the resulted dose delivery. With WFI, the better daily contralateral and ipsilateral neck target coverage can reflect a simpler or shorter localization; however, a much superior avoidance (WFI: mean dose a 42.5Gy; SFI: mean dose a 18.9Gy) of the non‐involved larynx from the SFI is preferred.

Conclusion:

Dosimetrically, SFI and WFI are equally well for head and Neck cancer treatment with VMAT technique; however, if considering the contribution of daily localization(CBCT) method uncertainties, SFI is better with sparing non‐involved larynx and WFI has better target coverage.
SU‐F‐J‐19: Robust Region‐Of‐Interest (ROI) for Consistent Registration On Deteriorated Surface Images
Authors: Kang H , Malin M , Chmura S , Hasan Y , Al‐Hallaq H
Published: July 2016

Purpose:

For African‐American patients receiving breast radiotherapy with a bolus, skin darkening can affect the surface visualization when using optical imaging for daily positioning and gating at deep‐inspiration breath holds (DIBH). Our goal is to identify a region‐of‐interest (ROI) that is robust against deteriorating surface image quality due to skin darkening.

Methods:

We study four patients whose post‐mastectomy surfaces are imaged daily with AlignRT (VisionRT, UK) for DIBH radiotherapy and whose surface image quality is degraded toward the end of treatment. To simulate the effects of skin darkening, surfaces from the first ten fractions of each patient are systematically degraded by 25–35%, 40–50% and 65–75% of the total area of the clinically used ROI_ipsilateral‐chestwall. The degraded surfaces are registered to the reference surface in six degrees‐of‐freedom. To identify a robust ROI, three additional reference ROIs — ROI_chest+abdomen, ROI_bilateral‐chest and ROI_extended‐ipsilateral‐chestwall are created and registered to the degraded surfaces. Differences in registration using these ROIs are compared to that using ROI_ipsilateral‐chestwall.

Results:

For three patients, the deviations in the registrations to ROI_ipsilateral‐chestwall are > 2.0, 3.1 and 7.9mm on average for 25–35%, 40–50% and 65–75% degraded surfaces, respectively. Rotational deviations reach 11.1° in pitch. For the last patient, registration is consistent to within 2.6mm even on the 65–75% degraded surfaces, possibly because the surface topography has more distinct features. For ROI_bilateral‐chest and ROI_extended‐ipsilateral‐chest registrations deviate in a similar pattern. However, registration on ROI_chest+abdomen is robust to deteriorating image qualities to within 4.2mm for all four patients.

Conclusion:

Registration deviations using ROI_ipsilateral‐chestwall can reach 9.8mm on the 40–50% degraded surfaces. Caution is required when using AlignRT for patients experiencing skin darkening since the accuracy of AlignRT registration deteriorates. To avoid this inaccuracy, we recommend use of ROI_chest+abdomen, on which registration is consistent within 4.2mm even for highly degraded surfaces.
SU‐F‐J‐20: Commissioning and Acceptance Testing of the C‐Rad CatalystHD Surface Imaging System
Authors: Stanley D , Rasmussen K , Kirby N , Papanikolaou N , Gutierrez A
Published: July 2016

Introduction:

With the increasing use of surface‐based, nonionizing image‐guided radiotherapy (IGRT) systems, a comprehensive set of clinical acceptance and commissioning procedures are needed to ensure correct functionality and proper clinical integration. Although TG‐147 provides a specific set of parameters, measurement methodologies have yet to be described. The aim of this study was to provide a comprehensive overview of the commissioning and acceptance analysis performed for the C‐Rad CatalystHD imaging system.

Methods and Materials:

Methodology for the commissioning and acceptance of the C‐Rad CatalystHD imaging system was developed using commercially available clinical equipment. Following TG‐147 guidelines, the following tests were performed: integration of peripheral equipment, system drift, static spatial reproducibility and localization accuracy, static end‐to‐end analysis, static rotational accuracy, dynamic spatial accuracy, dynamic temporal accuracy, dynamic radiation delivery and a comprehensive end‐to‐end analysis.

Results:

The field of view (FOV) of the CatalystHD was 105×109×83 cm3 in the lateral, longitudinal and vertical directions. For thermal equilibrium and system drift, a thermal drift of 1.0mm was noted. A 45 min warmup time is recommended if the system has been shut off an extended period of time (>24 hours) before the QA procedure to eliminate any thermal drift. Spatial reproducibility was found to be 0.05±0.03 mm using a rigid phantom. For the static localization accuracy, system agreement with couch shifts was within 0.1±0.1 mm and positioning agreement with kV‐CBCT was 0.16±0.10 mm. For static rotational accuracy, system agreement with a high precision rotational stage (0.01 deg precision) was within 0.10±0.07 deg. Dynamic spatial and temporal localization accuracy was found to be within 0.2±0.1 mm.

Conclusion:

A comprehensive commissioning and acceptance study was performed using commercially available phantoms and in‐house methodologies to provide a performance evaluation of the CatalystHD imaging system.
SU‐F‐J‐21: Clinical Evaluation of Surface Scanning Systems in Different Treatment Locations
Authors: Moser T , Stefanowicz S , Rhein B , Oetzel D , Adeberg S , Koenig L , Wolf R , Rieken S , Karger C
Published: July 2016

Purpose:

To reduce imaging dose in fractionated IGRT, the ability of optical surface imaging systems (OSIS) to detect setup errors was tested. Therefore, clinical studies to evaluate for different treatment locations setup corrections derived by OSIS in comparison with x‐ray image guidance in fractionated radiation therapy was performed.

Methods:

The setup correction accuracy of an OSIS system (AlignRT, VisionRT, London, UK) will be analysed for the 4 tumour locations Pelvis, Upper Abdomen, Thorax and Breast, 20 patients for each location in comparison to a different system (Sentinel, C‐RAD, SE). For each patient, the setup corrections of the cone‐beam computed tomography (CBCT) of an Elekta Versa HD linear accelerator (Elekta, Crawley, UK) is considered as gold‐standard and then compared with those of the OSIS for the first ten fractions retrospectively. There were no clinical decisions made based on the surrogate system. For the OSIS, the reference surface is highly important as it represents the actual ground truth. It can be obtained either with the system itself or the surface structure delineated in the planning CT can be imported via DICOM interface. In this paper, the first results for the treatment region thorax are presented. The reference image modalities were compared.

Results:

Table 1 displays the difference between the setup corrections obtained with OSIS and CBCT in lateral (LAT), longitudinal (LNG) and vertical (VRT) direction for the DICOM reference image. While the median deviations are within a few millimeters, some outliers showed large deviations. Generally, the mean deviation as well as the spread was smallest in lateral and largest in vertical direction.

Conclusion:

Although the system allows fast, simple and non‐invasive determination of setup corrections, it should be evaluated treatment region dependant. Therefore, the study is ongoing. The application of OSIS may help to reduce the imaging dose for the patient.

We gratefully acknowledge the support by our colleagues from the Radiological University Clinic Heidelberg, where the study was performed. This work was funded by the Federal Ministry of Education and Research (BMBF) Germany, grant number 01IB13001B.
SU‐F‐J‐24: Setup Uncertainty and Margin of the ExacTrac 6D Image Guide System for Patients with Brain Tumors
Authors: Kim S , Oh S , Yea J , Park J
Published: July 2016

Purpose:

This study evaluated the setup uncertainties for brain sites when using BrainLAB's ExacTrac X‐ray 6D system for daily pretreatment to determine the optimal planning target volume (PTV) margin.

Methods:

Between August 2012 and April 2015, 28 patients with brain tumors were treated by daily image‐guided radiotherapy using the BrainLAB ExacTrac 6D image guidance system of the Novalis‐Tx linear accelerator. DUONTM (Orfit Industries, Wijnegem, Belgium) masks were used to fix the head. The radiotherapy was fractionated into 27–33 treatments. In total, 844 image verifications were performed for 28 patients and used for the analysis. The setup corrections along with the systematic and random errors were analyzed for six degrees of freedom in the translational (lateral, longitudinal, and vertical) and rotational (pitch, roll, and yaw) dimensions.

Results:

Optimal PTV margins were calculated based on van Herk et al.'s [margin recipe = 2.5∑ + 0.7σ − 3 mm] and Stroom et al.'s [margin recipe = 2∑ + 0.7σ] formulas. The systematic errors (∑) were 0.72, 1.57, and 0.97 mm in the lateral, longitudinal, and vertical translational dimensions, respectively, and 0.72°, 0.87°, and 0.83° in the pitch, roll, and yaw rotational dimensions, respectively. The random errors (σ) were 0.31, 0.46, and 0.54 mm in the lateral, longitudinal, and vertical rotational dimensions, respectively, and 0.28°, 0.24°, and 0.31° in the pitch, roll, and yaw rotational dimensions, respectively. According to van Herk et al.'s and Stroom et al.'s recipes, the recommended lateral PTV margins were 0.97 and 1.66 mm, respectively; the longitudinal margins were 1.26 and 3.47 mm, respectively; and the vertical margins were 0.21 and 2.31 mm, respectively.

Conclusion:

Therefore, daily setup verifications using the BrainLAB ExacTrac 6D image guide system are very useful for evaluating the setup uncertainties and determining the setup margin.∑σ
SU‐F‐J‐26: Performance of 2.5MV Portal Imaging in Comparison with KV X‐Ray and 6MV and Flattening‐Filter‐Free 6MV Portal Imaging
Authors: Duan J , Yang Y , Faught A , Subashi E , Wu Q , Yin F
Published: July 2016

Purpose:

To assess image quality and imaging dose of 2.5MV electronic portal imaging in comparison to kV imaging and 6MV and Flattening‐Filter‐Free 6MV (6MVFFF) portal imaging using a DMI imager.

Methods:

Quantitative assessment of image quality was performed with Leeds and Las Vegas test phantoms in conjunction with qualitative evaluation of clinical patient images for kV imaging and 2.5MV, 6MV and 6MVFFF portal imaging. High and low contrast resolutions were evaluated and imaging doses were measured using these x‐rays. Phantom test was performed both in air and in solid water. Clinical patient portal images were also reviewed and qualitatively assessed for these three imaging MV energies.

Results:

Among the 28 objects in Las Vegas phantom, 16, 17 and 26 of them were resolved using Low Dose technique and 18, 22 and 26 were resolved using High Quality technique with 6MV, 6MVFFF and 2.5MV, respectively. The number of Leeds low contrast objects resolved by 6MV, 6MFFFF and 2.5MV was 6, 15 and 18 with Low Dose technique and 14, 17 and 18 with High Quality technique, respectively. When the test phantoms were embedded in 20cm thick solid water, the results were noticeably affected, but the performance of 2.5MV was still substantially better than 6MV and 6MVFFF. Imaging dose with 2.5MV measured at 10 cm depth was about half of that with 6MV or 6MVFFF. Clinical patient portal images were reviewed and qualitatively assessed for different sites including brain, head‐and‐neck, chest and pelvis. 2.5MV imaging provided more details and substantially higher contrast.

Conclusion:

While portal imaging with 6MVFFF provides noticeably better image quality than that with 6MV, the performance of 2.5MV portal imaging is substantially better than both 6MV and 6MVFFF in terms of high and low contrast resolutions as well as lower imaging dose. 2.5MV imaging provides near kV imaging quality.
SU‐F‐J‐27: Segmentation of Prostate CBCT Images with Implanted Calypso Transponders Using Double Haar Wavelet Transform
Authors: Liu Y , Saleh Z , Song Y , Obcemea C , Chan M , Li X , Happersett L , Shi C , Qian X , Tang X
Published: July 2016

Purpose:

Segmentation of prostate CBCT images is an essential step towards real‐time adaptive radiotherapy. It is challenging For Calypso patients, as more artifacts are generated by the beacon transponders. We herein propose a novel wavelet‐based segmentation algorithm for rectum, bladder, and prostate of CBCT images with implanted Calypso transponders.

Methods:

Five hypofractionated prostate patients with daily CBCT were studied. Each patient had 3 Calypso transponder beacons implanted, and the patients were setup and treated with Calypso tracking system. Two sets of CBCT images from each patient were studied. The structures (i.e. rectum, bladder, and prostate) were contoured by a trained expert, and these served as ground truth. For a given CBCT, the moving window‐based Double Haar transformation is applied first to obtain the wavelet coefficients. Based on a user defined point in the object of interest, a cluster algorithm based adaptive thresholding is applied to the low frequency components of the wavelet coefficients, and a Lee filter theory based adaptive thresholding is applied to the high frequency components. For the next step, the wavelet reconstruction is applied to the thresholded wavelet coefficients. A binary/segmented image of the object of interest is therefore obtained. DICE, sensitivity, inclusiveness and ΔV were used to evaluate the segmentation result.

Results:

Considering all patients, the bladder has the DICE, sensitivity, inclusiveness, and ΔV ranges of [0.81–0.95], [0.76–0.99], [0.83–0.94], [0.02–0.21]. For prostate, the ranges are [0.77–0.93], [0.84–0.97], [0.68–0.92], [0.1–0.46]. For rectum, the ranges are [0.72–0.93], [0.57–0.99], [0.73–0.98], [0.03–0.42].

Conclusion:

The proposed algorithm appeared effective segmenting prostate CBCT images with the present of the Calypso artifacts. However, it is not robust in two scenarios: 1) rectum with significant amount of gas; 2) prostate with very low contrast. Model based algorithm might improve the segmentation in these two scenarios.