bluuebunny/crossref_metadata_2025 huggingface dataset:
WE‐DE‐201‐11: Sensitivity and Specificity of Verification Methods Based On Total Reference Air Kerma (TRAK) Or On User Provided Dose Points for Graphically Planned Skin HDR Brachytherapy
Authors: Damato A , Devlin P , Bhagwat M , Buzurovic I , Hansen J , O'Farrell D , Cormack R
Published: July 2016

Purpose:

To investigate the sensitivity and specificity of a novel verification methodology for image‐guided skin HDR brachytherapy plans using a TRAK‐based reasonableness test, compared to a typical manual verification methodology.

Methods:

Two methodologies were used to flag treatment plans necessitating additional review due to a potential discrepancy of 3 mm between planned dose and clinical target in the skin. Manual verification was used to calculate the discrepancy between the average dose to points positioned at time of planning representative of the prescribed depth and the expected prescription dose. Automatic verification was used to calculate the discrepancy between TRAK of the clinical plan and its expected value, which was calculated using standard plans with varying curvatures, ranging from flat to cylindrically circumferential. A plan was flagged if a discrepancy >10% was observed. Sensitivity and specificity were calculated using as a criteria for true positive that >10% of plan dwells had a distance to prescription dose >1 mm different than prescription depth (3 mm + size of applicator). All HDR image‐based skin brachytherapy plans treated at our institution in 2013 were analyzed.

Results:

108 surface applicator plans to treat skin of the face, scalp, limbs, feet, hands or abdomen were analyzed. Median number of catheters was 19 (range, 4 to 71) and median number of dwells was 257 (range, 20 to 1100). Sensitivity/specificity were 57%/78% for manual and 70%/89% for automatic verification.

Conclusion:

A check based on expected TRAK value is feasible for irregularly shaped, image‐guided skin HDR brachytherapy. This test yielded higher sensitivity and specificity than a test based on the identification of representative points, and can be implemented with a dedicated calculation code or with pre‐calculated lookup tables of ideally shaped, uniform surface applicators.
WE‐DE‐BRC‐06: Exercise
Authors: Dunscombe P.
Published: July 2016

This SAMs Therapy Educational Course will introduce participants to the tools recommended by TG 100 for use in the development of a risk‐based Quality Management Program. The Course will start with an Overview of the background and rationale behind the TG 100 initiative, from which its charge was developed. After setting the scene, four 15 minute presentations will introduce the principal components of the soon to be published Report of TG 100. These are Process Mapping, Failure Modes and Effects Analysis, Fault Tree Analysis and the development of a QA/QM risk‐based Program. There will be time for two short exercises based on Failure Modes and Effects Analysis and a Discussion before the SAMs questions which will conclude the session.

Learning Objectives:

To appreciate the underlying philosophy of the TG 100 initiative.

To gain a brief overview of the principal risk‐based tools recommended by TG 100.

In an informal workshop format, to explore, at an introductory level, the use of risk analysis as proposed by TG 100 as a prelude to the development of a Quality Management Program.
WE‐DE‐BRA‐10: Development of a Novel Scanning Beam Low‐Energy Intraoperative Radiation Therapy (SBIORT) System for Pancreatic Cancer
Authors: Wears B , Mohiuddin I , Flynn R , Waldron T , Kim Y , Allen B , Xia J
Published: July 2016

Purpose:

Developing a compact collimator system and validating a 3D surface imaging module for a scanning beam low‐energy x‐ray radiation therapy (SBIORT) system that enables delivery of non‐uniform radiation dose to targets with irregular shapes intraoperatively.

Methods:

SBIORT consists of a low energy x‐ray source, a custom compact collimator module, a robotic arm, and a 3D surface imaging module. The 3D surface imaging system (structure sensor) is utilized for treatment planning and motion monitoring of the surgical cavity. SBIORT can deliver non‐uniform dose distributions by dynamically moving the x‐ray source assembly along optimal paths with various collimator apertures. The compact collimator utilizes a dynamic shutter mechanism to form a variable square aperture. The accuracy and reproducibility of the collimator were evaluated using a high accuracy encoder and a high resolution camera platform. The dosimetrical characteristics of the collimator prototype were evaluated using EBT3 films with a Pantak Therapax unit. The accuracy and clinical feasibility of the 3D imaging system were evaluated using a phantom and a cadaver cavity.

Results:

The SBIORT collimator has a compact size: 66 mm diameter and 10 mm thickness with the maximum aperture of 20 mm. The mechanical experiment indicated the average accuracy of leaf position was 0.08 mm with a reproducibility of 0.25 mm at 95% confidence level. The dosimetry study indicated the collimator had a penumbra of 0.35 mm with a leaf transmission of 0.5%. 3D surface scans can be acquired in 5 seconds. The average difference between the acquired 3D surface and the ground truth is 1 mm with a standard deviation of 0.6 mm.

Conclusion:

This work demonstrates the feasibility of the compact collimator and 3D scanning system for the SBIORT. SBIORT is a way of delivering IORT with a compact system that requires minimum shielding of the procedure room.

This research is supported by the University of Iowa Internal Funding Initiatives
WE‐DE‐207B‐04: Quantitative Contrast‐Enhanced Spectral Mammography Based On Photon‐Counting Detectors: A Feasibility Study
Authors: Ding H , Zhou B , Beidokhti D , Molloi S
Published: July 2016

Purpose:

To investigate the feasibility of accurate quantification of iodine mass thickness in contrast‐enhanced spectral mammography.

Methods:

Experimental phantom studies were performed on a spectral mammography system based on Si strip photon‐counting detectors. Dual‐energy images were acquired using 40 kVp and a splitting energy of 34 keV with 3 mm Al pre‐filtration. The initial calibration was done with glandular and adipose tissue equivalent phantoms of uniform thicknesses and iodine disk phantoms of various concentrations. A secondary calibration was carried out using the iodine signal obtained from the dual‐energy decomposed images and the known background phantom thicknesses and densities. The iodine signal quantification method was validated using phantoms composed of a mixture of glandular and adipose materials, for various breast thicknesses and densities. Finally, the traditional dual‐energy weighted subtraction method was also studied as a comparison. The measured iodine signal from both methods was compared to the known iodine concentrations of the disk phantoms to characterize the quantification accuracy.

Results:

There was good agreement between the iodine mass thicknesses measured using the proposed method and the known values. The root‐mean‐square (RMS) error was estimated to be 0.2 mg/cm2. The traditional weighted subtraction method also predicted a linear correlation between the measured signal and the known iodine mass thickness. However, the correlation slope and offset values were strongly dependent on the total breast thickness and density.

Conclusion:

The results of the current study suggest that iodine mass thickness can be accurately quantified with contrast‐enhanced spectral mammography. The quantitative information can potentially improve the differentiation between benign and malignant legions.

Grant funding from Philips Medical Systems.
WE‐FG‐207B‐07: Feasibility of Low Dose Lung Cancer Screening with a Whole‐Body Photon Counting CT: First Human Results
Authors: Symons R , Cork T , Folio L , Bluemke D , Pourmorteza A
Published: July 2016

Purpose:

To evaluate the feasibility of using a whole‐body photon counting detector (PCD) CT scanner for low dose lung cancer screening compared to a conventional energy integrating detector (EID) system.

Methods:

Radiation dose‐matched EID and PCD scans of the COPDGene 2 phantom and 2 human volunteers were acquired. Phantom images were acquired at different radiation dose levels (CTDIvol: 3.0, 1.5, and 0.75 mGy) and different tube voltages (120, 100, and 80 kVp), while human images were acquired at vendor recommended low‐dose lung cancer screening settings. EID and PCD images were compared for quantitative Hounsfield unit accuracy, noise levels, and contrast‐to‐noise ratios (CNR) for detection of ground‐glass nodules (GGNs) and emphysema.

Results:

The PCD Hounsfield unit accuracy was better for water at all scan parameters, and for lung, GGN and emphysema equivalent regions of interest (ROIs) at 1.5 and 0.75 mGy. PCD attenuation accuracy was more consistent for all scan parameters (all P<0.01), while Hounsfield units for lung, GGN and emphysema ROIs changed significantly for EID with decreasing dose (all P<0.001). PCD showed lower noise levels at the lowest dose setting at 120, 100 and 80 kVp (15.2±0.3 vs 15.8±0.2, P=0.03; 16.1±0.3 vs 18.0±0.4, P=0.003; and 16.1±0.3 vs 17.9±0.3, P=0.001, respectively), resulting in superior CNR for the detection of GGNs and emphysema at 100 and 80 kVp. Significantly lower PCD noise levels were confirmed in volunteer images.

Conclusion:

PCD provided better Hounsfield unit accuracy for lung, ground‐glass, and emphysema‐equivalent foams at 1.5 and 0.75 mGy with less variability than EID. Additionally, PCD showed less noise, and higher CNR at 0.75 mGy for both 100 and 80 kVp. PCD technology may help reduce radiation exposure in lung cancer screening while maintaining diagnostic quality.
WE‐FG‐207B‐10: Dual‐Energy CT Monochromatic Image Consistency Across Vendors and Platforms
Authors: Jacobsen M , Wood C , Cody D
Published: July 2016

Purpose:

Although dual‐energy CT provides improved sensitivity of HU for certain tissue types at lower simulated energy levels, if these values vary by scanner type they may impact clinical patient management decisions. Each manufacturer has selected a specific dual‐energy CT approach (or in one case, three different approaches); understanding HU variability among low monochromatic images may be required when more than one dual‐energy CT scanner type is available for use.

Methods:

A large elliptical dualenergy quality control phantom (Gammex Inc.; Middleton, WI) containing several standard tissue type materials was scanned at least three times on each of the following systems: GE HD750, prototype GE Revolution CT with GSI, Siemens Flash, Siemens Edge, Siemens AS 128, and Philips IQon. Images were generated at 50, 70, and 140 keV. Soft tissue and Iodine HU were measured on a single central 5mm‐thick image; NIST constants were used to calculate the ideal HU for each material. Scan acquisitions were approximately dose‐matched (∼25mGy CTDIvol) and image parameters were held as consistent as possible (thickness, kernel, no noise reduction).

Results:

Measured soft tissue (29 HU at 120 kVp) varied from 28 HU to 44 HU at 50 keV (excluding one outlier), from 21 HU to 31 HU at 70 keV, and from 19 HU to 32 HU at 140 keV. Measured iodine (5mg/ml, 106 HU at 120 kVp) varied from 246 HU to 280 HU at 50 keV, from 123 HU to 129 HU at 70 keV, and from 22 HU to 32 HU at 140 keV.

Conclusion:

Measured HU in standard rods across 3 dual‐energy CT manufacturers and 6 scanner models varied directly with monochromatic level, with the most variability was observed at 50 keV and least variability at 70keV. Future work will include additional scanner platforms and how measurement variability impacts radiologists.

This research has been supported by funds from Dr. William Murphy, Jr., the John S. Dunn, Sr. Distinguished Chair in Diagnostic Imaging at MD Anderson Cancer Center.
WE‐FG‐207B‐11: Objective Image Characterization of Spectral CT with a Dual‐Layer Detector
Authors: Ozguner O , Halliburton S , Dhanantwari A , Wen G , Utrup S , Jordan D
Published: July 2016

Purpose:

To obtain objective reference data for the spectral performance on a dual‐layer detector CT platform (IQon, Philips) and compare virtual monoenergetic to conventional CT images.

Methods:

Scanning was performed using the hospital's clinical adult body protocol: helical acquisition at 120kVp, with CTDIvol=15mGy. Multiple modules (591, 515, 528) of a CATPHAN 600 phantom and a 20 cm diameter cylindrical water phantom were scanned. No modifications to the standard protocol were necessary to enable spectral imaging. Both conventional and virtual monoenergetic images were generated from acquired data. Noise characteristics were assessed through Noise Power Spectra (NPS) and pixel standard deviation from water phantom images. Spatial resolution was evaluated using Modulation Transfer Functions (MTF) of a tungsten wire as well as resolution bars. Low‐contrast detectability was studied using contrast‐to‐noise ratio (CNR) of a low contrast object.

Results:

MTF curves of monoenergetic and conventional images were almost identical. MTF 50%, 10%, and 5% levels for monoenergetic images agreed with conventional images within 0.05lp/cm. These observations were verified by the resolution bars, which were clearly resolved at 7lp/cm but started blurring at 8lp/cm for this protocol in both conventional and 70 keV images. NPS curves indicated that, compared to conventional images, the noise power distribution of 70 keV monoenergetic images is similar (i.e. noise texture is similar) but exhibit a low frequency peak at keVs higher and lower than 70 keV. Standard deviation measurements show monoenergetic images have lower noise except at 40 keV where it is slightly higher. CNR of monoenergetic images is mostly flat across keV values and is superior to that of conventional images.

Conclusion:

Values for standard image quality metrics are the same or better for monoenergetic images compared to conventional images. Results indicate virtual monoenergetic images can be used without any loss in image quality or noise penalties relative to conventional images.

This study was performed as part of a research agreement among Philips Healthcare, University Hospitals of Cleveland, and Case Western Reserve University.
WE‐FG‐207B‐12: Quantitative Evaluation of a Spectral CT Scanner in a Phantom Study: Results of Spectral Reconstructions
Authors: Duan X , Arbique G , Guild J , Yagil Y , Anderson J
Published: July 2016

Purpose:

To evaluate the quantitative image quality of spectral reconstructions of phantom data from a spectral CT scanner.

Methods:

The spectral CT scanner (IQon Spectral CT, Philips Healthcare) is equipped with a dual‐layer detector and generates conventional 80ߝ140 kVp images and variety of spectral reconstructions, e.g., virtual monochromatic (VM) images, virtual non‐contrast (VNC) images, iodine maps, and effective atomic number (Z) images. A cylindrical solid water phantom (Gammex 472, 33 cm diameter and 5 cm thick) with iodine (2.0ߝ20.0 mg I/ml) and calcium (50ߝ600 mg/ml) rod inserts was scanned at 120 kVp and 27 mGy CTDIvol. Spectral reconstructions were evaluated by comparing image measurements with theoretical values calculated from nominal rod compositions provided by the phantom manufacturer. The theoretical VNC was calculated using water and iodine basis material decomposition, and the theoretical Z was calculated using two common methods, the chemical formula method (Z1) and the dual‐energy ratio method (Z2).

Results:

Beam‐hardening‐like artifacts between high‐attenuation calcium rods (≥300 mg/ml, >800 HU) influenced quantitative measurements, so the quantitative analysis was only performed on iodine rods using the images from the scan with all the calcium rods removed. The CT numbers of the iodine rods in the VM images (50∼150 keV) were close to theoretical values with average difference of 2.4±6.9 HU. Compared with theoretical values, the average difference for iodine concentration, VNC CT number and effective Z of iodine rods were −0.10±0.38 mg/ml, −0.1±8.2 HU, 0.25±0.06 (Z1) and −0.23±0.07 (Z2).

Conclusion:

The results indicate that the spectral CT scanner generates quantitatively accurate spectral reconstructions at clinically relevant iodine concentrations. Beam‐hardening‐like artifacts still exist when high‐attenuation objects are present and their impact on patient images needs further investigation.

YY is an employee of Philips Healthcare.
WE‐G‐204‐01: Building a Career in Academic Medical Physics: The Hardest and Best Job You Will Ever Have!
Authors: Hazle J.
Published: July 2016

While many indicators for academic medical physics are distressing – jobs are tight, demands on clinical time are high (and getting worse) and national funding has been flat for several years (meaning less money in reality) the present is perhaps one of the most exciting times in cancer research history, and medical physicists have an opportunity to make a difference.

Many of us predict the impact of medical physics on cancer research over the next decade to be more significant than ever. Why is that? First, medical imaging is used for every cancer patient in developed countries. Every improvement in the acquisition, processing or analysis of radiological images has the potential to impact patients. The use of radiation therapy is at an all‐time high – and virtually cannot be performed without medical physics. Many of the advances in both biomedical imaging and radiation oncology are the result of the hard work of academic medical physicists who are thinking of the next generation of technologies that will be used against cancer or an even broader spectrum of diseases.

A career in academic medical physics is demanding, particularly for those with clinical responsibilities. As the demands for justification of their clinical effort become increasingly metricized, the ability to do “unfunded research” will become even more difficult. This means that many will have to generate external salary support to justify their efforts in research and development. This comes at a time when funding for research is compressed and harder to obtain. Generally speaking, if you are not contributing 50% or more of your effort to research, you are competing at a disadvantage and it is very unlikely you will get an NIH/NCI/NIBIB grant.

Furthermore, in the ongoing effort to improve patient care and safety, we have developed credentialing pathways that now require at least two‐years of residency training. This full‐time clinical training creates a gap in the research trajectory of graduate students who aspire to academic positions with an expectation for extramural funding. To address this, several residency programs have created hybrid programs where the two‐years of clinical training is combined with one or two years of research effort to allow candidates to further establish an academic identity and to ensure adequate academic productivity to compete for a beginning faculty position.

In conclusion, while the path to a successful career in academic medical physics is steep and sometimes hard to follow, reaching the apex is worth the journey. Different paths to a career in medical physics are available, you just have to decide which one is right for you. If improving cancer care is your goal as a physicist, then academic medical physics is the job for you!
WE‐G‐BRC‐01: Risk Assessment for Radiosurgery
Authors: Kim G.
Published: July 2016

Failure Mode and Effects Analysis (FMEA) originated as an industrial engineering technique used for risk management and safety improvement of complex processes. In the context of radiotherapy, the AAPM Task Group 100 advocates FMEA as the framework of choice for establishing clinical quality management protocols. However, there is concern that widespread adoption of FMEA in radiation oncology will be hampered by the perception that implementation of the tool will have a steep learning curve, be extremely time consuming and labor intensive, and require additional resources. To overcome these preconceptions and facilitate the introduction of the tool into clinical practice, the medical physics community must be educated in the use of this tool and the ease in which it can be implemented. Organizations with experience in FMEA should share their knowledge with others in order to increase the implementation, effectiveness and productivity of the tool.

This session will include a brief, general introduction to FMEA followed by a focus on practical aspects of implementing FMEA for specific clinical procedures including HDR brachytherapy, physics plan review and radiosurgery. A description of common equipment and devices used in these procedures and how to characterize new devices for safe use in patient treatments will be presented. This will be followed by a discussion of how to customize FMEA techniques and templates to one's own clinic. Finally, cases of common failure modes for specific procedures (described previously) will be shown and recommended intervention methodologies and outcomes reviewed.

Learning Objectives:

Understand the general concept of failure mode and effect analysis

Learn how to characterize new equipment for safety

Be able to identify potential failure modes for specific procedures and learn mitigation techniques

Be able to customize FMEA examples and templates for use in any clinic
WE‐G‐209‐01: Digital Radiography
Authors: Schueler B.
Published: July 2016

Digital radiography, CT, PET, and MR are complicated imaging modalities which are composed of many hardware and software components. These components work together in a highly coordinated chain of events with the intent to produce high quality images. Acquisition, processing and reconstruction of data must occur in a precise way for optimum image quality to be achieved. Any error or unexpected event in the entire process can produce unwanted pixel intensities in the final images which may contribute to visible image artifacts. The diagnostic imaging physicist is uniquely qualified to investigate and contribute to resolution of image artifacts.

This course will teach the participant to identify common artifacts found clinically in digital radiography, CT, PET, and MR, to determine the causes of artifacts, and to make recommendations for how to resolve artifacts.

Learning Objectives:

Identify common artifacts found clinically in digital radiography, CT, PET and MR.

Determine causes of various clinical artifacts from digital radiography, CT, PET and MR.

Describe how to resolve various clinical artifacts from digital radiography, CT, PET and MR.
WE‐H‐BRC‐06: A Unified Machine‐Learning Based Probabilistic Model for Automated Anomaly Detection in the Treatment Plan Data
Authors: Chang X , Kalet A , Liu S , Yang D
Published: July 2016

Purpose:

The purpose of this work was to investigate the ability of a machine‐learning based probabilistic approach to detect radiotherapy treatment plan anomalies given initial disease classes information.

Methods

In total we obtained 1112 unique treatment plans with five plan parameters and disease information from a Mosaiq treatment management system database for use in the study. The plan parameters include prescription dose, fractions, fields, modality and techniques. The disease information includes disease site, and T, M and N disease stages. A Bayesian network method was employed to model the probabilistic relationships between tumor disease information, plan parameters and an anomaly flag. A Bayesian learning method with Dirichlet prior was useed to learn the joint probabilities between dependent variables in error‐free plan data and data with artificially induced anomalies. In the study, we randomly sampled data with anomaly in a specified anomaly space.We tested the approach with three groups of plan anomalies – improper concurrence of values of all five plan parameters and values of any two out of five parameters, and all single plan parameter value anomalies. Totally, 16 types of plan anomalies were covered by the study. For each type, we trained an individual Bayesian network.

Results:

We found that the true positive rate (recall) and positive predictive value (precision) to detect concurrence anomalies of five plan parameters in new patient cases were 94.45±0.26% and 93.76±0.39% respectively. To detect other 15 types of plan anomalies, the average recall and precision were 93.61±2.57% and 93.78±3.54% respectively. The computation time to detect the plan anomaly of each type in a new plan is ∼0.08 seconds.

Conclusion:

The proposed method for treatment plan anomaly detection was found effective in the initial tests. The results suggest that this type of models could be applied to develop plan anomaly detection tools to assist manual and automated plan checks.

The senior author received research grants from ViewRay Inc. and Varian Medical System.
WE‐H‐BRA‐08: A Monte Carlo Cell Nucleus Model for Assessing Cell Survival Probability Based On Particle Track Structure Analysis
Authors: Lee B , Wang C
Published: July 2016

Purpose:

To correlate the damage produced by particles of different types and qualities to cell survival on the basis of nanodosimetric analysis and advanced DNA structures in the cell nucleus.

Methods:

A Monte Carlo code was developed to simulate subnuclear DNA chromatin fibers (CFs) of 30nm utilizing a mean‐free‐path approach common to radiation transport. The cell nucleus was modeled as a spherical region containing 6000 chromatin‐dense domains (CDs) of 400nm diameter, with additional CFs modeled in a sparser interchromatin region. The Geant4‐DNA code was utilized to produce a particle track database representing various particles at different energies and dose quantities. These tracks were used to stochastically position the DNA structures based on their mean free path to interaction with CFs. Excitation and ionization events intersecting CFs were analyzed using the DBSCAN clustering algorithm for assessment of the likelihood of producing DSBs. Simulated DSBs were then assessed based on their proximity to one another for a probability of inducing cell death.

Results:

Variations in energy deposition to chromatin fibers match expectations based on differences in particle track structure. The quality of damage to CFs based on different particle types indicate more severe damage by high‐LET radiation than low‐LET radiation of identical particles. In addition, the model indicates more severe damage by protons than of alpha particles of same LET, which is consistent with differences in their track structure. Cell survival curves have been produced showing the L‐Q behavior of sparsely ionizing radiation.

Conclusion:

Initial results indicate the feasibility of producing cell survival curves based on the Monte Carlo cell nucleus method. Accurate correlation between simulated DNA damage to cell survival on the basis of nanodosimetric analysis can provide insight into the biological responses to various radiation types. Current efforts are directed at producing cell survival curves for high‐LET radiation.
WE‐H‐202‐01: Memorial Introduction
Authors: Kirby N.
Published: July 2016

Deformable image registration has now been commercially available for several years, with solid performance in a number of sites and for several applications including contour and dose mapping. However, more complex applications have arisen, such as assessing response to radiation therapy over time, registering images pre‐ and post‐surgery, and auto‐segmentation from atlases. These applications require innovative registration algorithms to achieve accurate alignment. The goal of this session is to highlight emerging registration technology and these new applications. The state of the art in image registration will be presented from an engineering perspective. Translational clinical applications will also be discussed to tie these new registration approaches together with imaging and radiation therapy applications in specific diseases such as cervical and lung cancers.

Learning Objectives:

To understand developing techniques and algorithms in deformable image registration that are likely to translate into clinical tools in the near future.

To understand emerging imaging and radiation therapy clinical applications that require such new registration algorithms.

Research supported in part by the National Institutes of Health under award numbers P01CA059827, R01CA166119, and R01CA166703. Disclosures: Phillips Medical systems (Hugo), Roger Koch (Christensen) support, Varian Medical Systems (Brock), licensing agreements from Raysearch (Brock) and Varian (Hugo).; K. Brock, Licensing Agreement ‐ RaySearch Laboratories. Research Funding ‐ Varian Medical Systems; G. Hugo, Research grant from National Institutes of Health, award number R01CA166119.; G. Christensen, Research support from NIH grants CA166119 and CA166703 and a gift from Roger Koch. There are no conflicts of interest.
WE‐H‐202‐03: Accounting for Large Geometric Changes During Radiotherapy
Authors: Hugo G.
Published: July 2016

Deformable image registration has now been commercially available for several years, with solid performance in a number of sites and for several applications including contour and dose mapping. However, more complex applications have arisen, such as assessing response to radiation therapy over time, registering images pre‐ and post‐surgery, and auto‐segmentation from atlases. These applications require innovative registration algorithms to achieve accurate alignment. The goal of this session is to highlight emerging registration technology and these new applications. The state of the art in image registration will be presented from an engineering perspective. Translational clinical applications will also be discussed to tie these new registration approaches together with imaging and radiation therapy applications in specific diseases such as cervical and lung cancers.

Learning Objectives:

To understand developing techniques and algorithms in deformable image registration that are likely to translate into clinical tools in the near future.

To understand emerging imaging and radiation therapy clinical applications that require such new registration algorithms.

Research supported in part by the National Institutes of Health under award numbers P01CA059827, R01CA166119, and R01CA166703. Disclosures: Phillips Medical systems (Hugo), Roger Koch (Christensen) support, Varian Medical Systems (Brock), licensing agreements from Raysearch (Brock) and Varian (Hugo).; K. Brock, Licensing Agreement ‐ RaySearch Laboratories. Research Funding ‐ Varian Medical Systems; G. Hugo, Research grant from National Institutes of Health, award number R01CA166119.; G. Christensen, Research support from NIH grants CA166119 and CA166703 and a gift from Roger Koch. There are no conflicts of interest.
WE‐H‐207A‐09: Theoretical Limits to Molecular Biomarker Detection Using Magnetic Nanoparticles
Authors: Weaver J
Published: July 2016

Purpose:

Estimate the limits of molecular biomarker detection using magnetic nanoparticle methods like in vivo ELISA.

Methods:

Magnetic nanoparticles in an alternating magnetic field produce a magnetization that can be detected at exceedingly low levels because the signal at the harmonic frequencies is uniquely produced by the nanoparticles. Because the magnetization can also be used to characterize the nanoparticle rotational freedom, the bound state can be found. If the nanoparticles are coated with molecules that bind the desired biomarker, the rotational freedom reflects the biomarker concentration. The irreducible noise limit is the thermal noise or Johnson noise of the tissue and the contrast that can be measured must be larger than that limit. The contrast produced is a function of the applied field and depends strongly on nanoparticle volume. We have estimated the contrast using a Langevin function of a single composite variable to approximate the full stochastic Langevin equation for nanoparticle dynamics.

Results:

The thermal noise for a bandwidth reasonable for spectroscopy suggests mid zeptomolar (10–21) to low attomolar (10–18) concentrations can be measured in a volume that is 10cm in scale. The suggested sensitivity is far below the physiologically concentrations of almost all critical biomarkers including cytokines (picomolar), hormones (nanomolar) and heat shock proteins.

Conclusion:

The sensitivity of in vivo ELISA concentration measurements should be sufficient to measure physiological concentrations of critical biomarkers like cytokines in vivo. Further the sensitivity should be sufficient to measure concentrations of other biomarkers that are six to eight orders of magnitude lower in concentration than immune signaling molecules like cytokines.

NIH ‐ 1U54CA151662‐01

Department of Radiology
WE‐H‐209‐01: Advances in Ultrasound Therapy
Authors: Hynynen K.
Published: July 2016

Focused ultrasound has been shown to be the only method that allows noninvasive thermal coagulation of tissues and recently this potential has been explored for image‐guided drug delivery. In this presentation, the advances in ultrasound phased array technology for energy delivery, exposure monitoring and control will be discussed. Experimental results from novel multi‐frequency transmit/receive arrays will be presented. In addition, the feasibility of fully electronically focused and steered high power arrays with many thousands of transducer elements will be discussed. Finally, some of the recent clinical and preclinical results for the treatment of brain disease will be reviewed.

Learning Objectives:

Introduce FUS therapy principles and modern techniques

Discuss use of FUS for drug delivery

Cover the technology required to deliver FUS and monitor therapy

Present clinical examples of the uses of these techniques

This research was supported by funding from The Canada Research Chair Program, Grants from CIHR and NIH (no. EB003268).; K. Hynynen, Canada Foundation for Innovation; Canadian Institutes of Health Research; Focused Ultrasound Surgery Foundation; Canada Research Chair Program; Natural Sciences and Engineering Research Council of Canada; Ontario Research Fund; National Institutes of Health; Canadian Cancer Society Research Institute; The Weston Brain Institute; Harmonic Medical; Focused Ultrasound Instruments
WE‐H‐207B‐02: MR‐Driven RT Planning
Authors: Cao M.
Published: July 2016

In recent years, steady progress has been made towards the implementation of MRI in external beam radiation therapy for processes ranging from treatment simulation to in‐room guidance. Novel procedures relying mostly on MR data are currently implemented in the clinic. This session will cover topics such as (a) commissioning and quality control of the MR in‐room imagers and simulators specific to RT, (b) treatment planning requirements, constraints and challenges when dealing with various MR data, (c) quantification of organ motion with an emphasis on treatment delivery guidance, and (d) MR‐driven strategies for adaptive RT workflows. The content of the session was chosen to address both educational and practical key aspects of MR guidance.

Learning Objectives:

Good understanding of MR testing recommended for in‐room MR imaging as well as image data validation for RT chain (e.g. image transfer, filtering for consistency, spatial accuracy, manipulation for task specific);

Familiarity with MR‐based planning procedures: motivation, core workflow requirements, current status, challenges;

Overview of the current methods for the quantification of organ motion;

Discussion on approaches for adaptive treatment planning and delivery.

T. Stanescu ‐ License agreement with Modus Medical Devices to develop a phantom for the quantification of MR image system‐related distortions.; T. Stanescu, N/A
TH‐A‐204‐01: Part I ‐ Key Data for Ionizing‐Radiation Dosimetry
Authors: Seltzer S.
Published: July 2016

The ICRU is currently finalizing a report on key data for radiation dosimetry. This multi‐year review has resulted in a number of recommendations regarding “fundamental” data that are used in dosimetry related to radiation therapy. This educational session will explain the background for the ICRU committee's work, the content and conclusions of the report and the impact on outputs, including NIST primary standards, ADCL calibration coefficients and clinical reference dosimetry. Parameters and beam modalities potentially affected by this report include:

The mean excitation energy, I, for graphite, air, and water, The average energy required to create an ion pair in dry air (commonly referred to as W/e), The uncertainty in the determination of air kerma in kV x‐rays The absolute value of Co‐60 and Cs‐137 primary standards and the dissemination of calibration coefficients, The determination of air kerma strength for Ir‐192 HDR brachytherapy sources Ion chamber kQ factors for linac MV beams Ion chamber kQ factors for proton beams.

The changes in reference dosimetry that would result from adoption of the ICRU recommendations are of the order of 0.5% to 1%, an effect that will not impact clinical dose delivery but will be detectable in the clinical setting.

This session will also outline how worldwide metrology is coordinated through the Convention of the Meter and therefore how the international dosimetry community will proceed with adopting these recommendations so that uniformity from country to country in reference dosimetry is maintained. Timelines and communications methods will also be discussed to ensure that users, such as clinical medical physicists, are not surprised when their chamber's calibration coefficient apparently changes.

Learning Objectives:

Understand the background for the ICRU committee's work on key dosimetry data.

Understand the proposed changes to key data and the impacts on reference dosimetry.

Understand the methodology and timeline for adoption of the ICRU recommendations.
TH‐AB‐201‐03: Characterization of Electron Beam Out‐Of‐Field Doses and Neutron Contamination from Modern Varian and Elekta Linear Accelerators
Authors: Cardenas C , Nitsch P , Kudchadker R , Howell R , Kry S
Published: July 2016

Purpose:

To investigate out‐of‐field electron doses and neutron production from electron beams from modern Varian and Elekta linear accelerators.

Methods:

Electron dose measurements were made using 10×10cm2 applicators on two Varian 21iXs, a Varian TrueBeam, and an Elekta Versa HD operating at energies from 6 to 20 MeV. Out‐of‐field dose profiles and PDD curves were measured in a Wellhofer water phantom using a Farmer chamber. Neutron measurements were made with a combination of moderator buckets and gold activation‐foils placed on the treatment couch at various locations in the patient plane on both the 21iX and Versa HD linear accelerators.

Results:

Electron doses were highest for the highest electron energies. Dose profile curves for the Varian units were found to be lower than those from the Versa HD unit, and were lower than photon beams. Elekta's dose profiles were higher and exhibited a second dose peak around 20–30 cm from central‐axis. Electron doses in this region (0.8–1.3% of dmax at central‐axis) were close to 5 times (2.5–4.8) greater than doses from photon beams with similar energies. Electron doses decreased sharply with depth before becoming nearly constant; the dose was found to decrease to a depth of approximately E(MeV)/4 in cm. Q‐values and neutron dose equivalent increased with energy and were typically higher on central‐axis. 18 MV photon beam neutron dose equivalents were greater than any electron beam, being approximately 40 times greater than for the 20 MeV electron beam (21iX).

Conclusion:

The Versa HD exhibited higher than expected out‐of‐field electron doses in comparison to typical radiotherapy photon beams. Fortunately, out‐of‐field electron doses can be substantially reduced by applying a water‐equivalent bolus with thickness of E(MeV)/4 in cm. Neutron contamination from clinical electron beams can be considered negligible in relation to photon beams but may need to be considered for special cases.

This work was supported by Public Health Service Grant CA180803 awarded by the National Cancer Institute, United States Department of Health and Human Services.
TH‐AB‐201‐06: Examining the Influence of Humidity On Reference Ion Chamber Performance
Authors: Taank J , McEwen M
Published: July 2016

Purpose:

International dosimetry protocols require measurements made with a vented ionization chamber to be corrected for the influence of air density by using the standard temperature‐pressure correction factor. The effect of humidity, on the other hand, is generally ignored with the provision that the relative humidity is between certain limits (15% to 80%). However, there is little experimental data in the published literature as to the true effect of humidity on modern reference‐class ion chambers. This investigation used two different radiation beams – a Co‐60 irradiator and a Sr‐90 check source – to examine the effect of humidity on several versions of the standard Farmer‐type ion chamber.

Methods:

An environmental cabinet controlled the humidity. For the Co‐60 beam, the irradiation was external, whereas for the Sr‐90 measurements, the source itself was placed within the cabinet. Extensive measurements were carried out to ensure that the experimental setup provided reproducible readings. Four chamber types were investigated: IBA FC65‐G (×2), IBA FC65‐P, PTW30013 & Exradin A19. The different wall materials provided potentially different mechanical responses (i.e., in terms of expansion/contraction) to the water content in the air. The relative humidity was varied between 8 % and 97 % and measurements were made with increasing and decreasing humidity to investigate possible hysteresis effects.

Results:

Measurements in Co‐60 were consistent with the published data obtained with primary standard cavity chambers in ICRU Report 31. Ionization currents with Sr‐90 showed no dependence with the relative humidity, within the measurement uncertainties. Very good repeatability of the ionization current was obtained over successive wet/dry cycles, no hysteresis was observed, and there was no dependence on chamber type.

Conclusion:

This null result is very encouraging as it indicates that humidity has no significant effect on these particular types of ionization chambers, consistent with recommendations in current megavoltage dosimetry protocols.
TH‐AB‐BRB‐00: Research Opportunities with Digital Linear Accelerators
Authors: Sheng Ke
Published: July 2016

Current state‐of‐the art digital C‐arm medical linear accelerators are capable of delivering radiation treatments with high level of automation, which affords coordinated motions of gantry, couch, and multileaf collimator (MLC) with dose rate modulations. The new machine capacity has shown the potential to bring substantially improved radiation dosimetry and/or delivery efficiency to many challenging diseases. Combining an integrated beam orientation optimization algorithm with automated machine navigation, markedly improved dose conformity has been achieved using 4ρ therapy. Trajectory modulated radiation therapy (TMAT) can be used to deliver highly conformal dose to partial breast or to carve complex dose distribution for therapy involving extended volumes such as total marrow and total lymph node treatment. Dynamic electron arc radiotherapy (DEAR) not only overcomes the deficiencies of conventional electron therapy in dose conformity and homogeneity but also achieves so without patient‐specific shields. The combination of MLC and couch tracking provides improved motion management of thoracic and abdominal tumors. A substantial body of work has been done in these technological advances for clinical translation. The proposed symposium will provide a timely review of these exciting opportunities.

Learning Objectives:

Recognize the potential of using digitally controlled linacs for clinically significant improvements in delivered dose distributions for various treatment sites.

Identify existing approaches to treatment planning, optimization and delivery for treatment techniques utilizing the advanced functions of digital linacs and venues for further development and improvement.

Understand methods for testing and validating delivery system performance.

Identify tools available on current delivery systems for implementation and control for such treatments.

Obtain the update in clinical applications, trials and regulatory approval.

K. Sheng, NIH U19AI067769, NIH R43CA183390, NIH R01CA188300, Varian Medical Systems

V. Yu, Varian Medical Systems, AAPM Summer Undergraduate Fellowship, NSF graduate fellowship

S. Nill, Elekta AB. Cancer Research UK under Programme C33589/A19727, NIHR Biomedical Research Centre at The Royal Marsden and The Institute of Cancer Research.
TH‐AB‐BRB‐03: 4n Radiotherapy
Authors: Sheng K.
Published: July 2016

Current state‐of‐the art digital C‐arm medical linear accelerators are capable of delivering radiation treatments with high level of automation, which affords coordinated motions of gantry, couch, and multileaf collimator (MLC) with dose rate modulations. The new machine capacity has shown the potential to bring substantially improved radiation dosimetry and/or delivery efficiency to many challenging diseases. Combining an integrated beam orientation optimization algorithm with automated machine navigation, markedly improved dose conformity has been achieved using 4ρ therapy. Trajectory modulated radiation therapy (TMAT) can be used to deliver highly conformal dose to partial breast or to carve complex dose distribution for therapy involving extended volumes such as total marrow and total lymph node treatment. Dynamic electron arc radiotherapy (DEAR) not only overcomes the deficiencies of conventional electron therapy in dose conformity and homogeneity but also achieves so without patient‐specific shields. The combination of MLC and couch tracking provides improved motion management of thoracic and abdominal tumors. A substantial body of work has been done in these technological advances for clinical translation. The proposed symposium will provide a timely review of these exciting opportunities.

Learning Objectives:

Recognize the potential of using digitally controlled linacs for clinically significant improvements in delivered dose distributions for various treatment sites.

Identify existing approaches to treatment planning, optimization and delivery for treatment techniques utilizing the advanced functions of digital linacs and venues for further development and improvement.

Understand methods for testing and validating delivery system performance.

Identify tools available on current delivery systems for implementation and control for such treatments.

Obtain the update in clinical applications, trials and regulatory approval.

K. Sheng, NIH U19AI067769, NIH R43CA183390, NIH R01CA188300, Varian Medical Systems

V. Yu, Varian Medical Systems, AAPM Summer Undergraduate Fellowship, NSF graduate fellowship

S. Nill, Elekta AB. Cancer Research UK under Programme C33589/A19727, NIHR Biomedical Research Centre at The Royal Marsden and The Institute of Cancer Research.