bluuebunny/crossref_metadata_2025 huggingface dataset:
MO‐FG‐204‐05: Evaluation of a Novel Algorithm for Improved 4DCT Resolution
Authors: Glide‐Hurst C , Klahr P , Briceno J , Chetty I. J.
Published: June 2015

Purpose:

Accurate tumor motion characterization is critical for increasing the therapeutic ratio of radiation therapy. To accommodate the divergent fan‐beam geometry of the scanner, the current 4D‐CT algorithm utilizes a larger temporal window to ensure that pixel values are valid throughout the entire FOV. To minimize the impact on temporal resolution, a cos2 weighting is employed. We propose a novel exponential weighting (“exponential”) 4DCT reconstruction algorithm that has a sharper slope and provides a more optimal temporal resolution.

Methods:

A respiratory motion platform translated a lung‐mimicking Styrofoam slab with several high and low‐contrast inserts 2 cm in the superior‐inferior direction. Breathing rates (10–15 bpm) and couch pitch (0.06–0.1 A.U.) were varied to assess interplay between parameters. Multi‐slice helical 4DCTs were acquired with 0.5 sec gantry rotation and data were reconstructed with cos2 and exponential weighting. Mean and standard deviation were calculated via region of interest analysis. Intensity profiles evaluated object boundaries. Retrospective raw data reconstructions were performed for both 4DCT algorithms for 3 liver and lung cancer patients. Image quality (temporal blurring/sharpness) and subtraction images were compared between reconstructions.

Results:

In the phantom, profile analysis revealed that sharper boundaries were obtained with exponential reconstructions at transitioning breathing phases (i.e. mid‐inhale or mid‐exhale). Reductions in full‐width half maximum were ∼1 mm in the superior‐inferior direction and appreciable sharpness could be observed in difference maps. This reduction also yielded a slight reduction in target volume between reconstruction algorithms. For patient cases, coronal views showed less blurring at object boundaries and local intensity differences near the tumor and diaphragm with exponential weighted reconstruction.

Conclusion:

Exponential weighted 4DCT offers potential for improving image sharpness in 4DCT. Comparisons with true object extent using static CTs of varied phantom positions are necessary to confirm these findings. Future work with additional patient cases is warranted.

Research partially sponsored by Philips Healthcare
MO‐FG‐207‐00: Technological Advances in PET/MR Imaging
Authors: Shao Yiping
Published: June 2015

The use of integrated PET/MRI systems in clinical applications can best benefit from understanding their technological advances and limitations. The currently available clinical PET/MRI systems have their own characteristics. Thorough analyses of existing technical data and evaluation of necessary performance metrics for quality assurances could be conducted to optimize application‐specific PET/MRI protocols. This Symposium will focus on technical advances and limitations of clinical PET/MRI systems, and how this exciting imaging modality can be utilized in applications that can benefit from both PET and MRI.

Learning Objectives:

To understand the technological advances of clinical PET/MRI systems

To correctly identify clinical applications that can benefit from PET/MRI

To understand ongoing work to further improve the current PET/MRI technology

Floris Jansen is a GE Healthcare employee.
MO‐FG‐207‐03: Maximizing the Utility of Integrated PET/MRI in Clinical Applications
Authors: Behr S.
Published: June 2015

The use of integrated PET/MRI systems in clinical applications can best benefit from understanding their technological advances and limitations. The currently available clinical PET/MRI systems have their own characteristics. Thorough analyses of existing technical data and evaluation of necessary performance metrics for quality assurances could be conducted to optimize application‐specific PET/MRI protocols. This Symposium will focus on technical advances and limitations of clinical PET/MRI systems, and how this exciting imaging modality can be utilized in applications that can benefit from both PET and MRI.

Learning Objectives:

To understand the technological advances of clinical PET/MRI systems

To correctly identify clinical applications that can benefit from PET/MRI

To understand ongoing work to further improve the current PET/MRI technology

Floris Jansen is a GE Healthcare employee.
MO‐FG‐201‐00: High‐Impact Presentations
Authors: Jordan David
Published: June 2015

Oral presentations are one of the most important tools to advance education, scientific research, and clinical excellence in medical physics. Medical physicists do not often captivate their audiences like a Steve Jobs keynote or a TED talk, but every physicist can learn to engage their audiences and deliver their message in a memorable way using their own personality and style. This interactive session will teach attendees to discover their own style and voice and to use it to engage and connect with their audiences. Audience reception and response will be reviewed in terms of the speaker's executive presence and content, as well as research on the psychology of audiences and physiology of speakers. Physicists will learn how to organize and mentally prepare themselves as well as their PowerPoint slides.

Learning Objectives:

Develop executive presence: poised under pressure to deliver a message in a relaxed, casual, and credible way

Connect with an audience by creating harmony between the content and the visual and audible elements of a presentation

Confidently deliver engaging presentations in the individual's voice and personality

Heidi Weiker and Tanya Weiker are co‐owners of Spherica LLC.
MO‐FG‐210‐01: Commissioning An US System for Brachytherapy: An Overview of Physics, Instrumentation, and Techniques
Authors: Chang Z.
Published: June 2015

Ultrasound (US) is one of the most widely used imaging modalities in medical practice. Since US imaging offers real‐time imaging capability, it has becomes an excellent option to provide image guidance for brachytherapy (IGBT). (1) The physics and the fundamental principles of US imaging are presented, and the typical steps required to commission an US system for IGBT is provided for illustration. (2) Application of US for prostate HDR brachytherapy, including partial prostate treatments using MR‐ultrasound co‐registration to enable a focused treatment on the disease within the prostate is also presented. Prostate HDR with US image guidance planning can benefit from real time visualization of the needles, and fusion of the ultrasound images with T2 weighted MR allows the focusing of the treatment to the specific areas of disease within the prostate, so that the entire gland need not be treated. Finally, (3) ultrasound guidance for an eye plaque program is presented. US can be a key component of placement and QA for episcleral plaque brachytherapy for ocular cancer, and the UCLA eye plaque program with US for image guidance is presented to demonstrate the utility of US verification of plaque placement in improving the methods and QA in episcleral plaque brachytherapy.

Learning Objectives:

To understand the physics of an US system and the necessary aspects of commissioning US for image guided brachytherapy (IGBT).

To understand real time planning of prostate HDR using ultrasound, and its application in partial prostate treatments using MR‐ultrasound fusion to focus treatment on disease within the prostate.

To understand the methods and QA in applying US for localizing the target and the implant during a episcleral plaque brachytherapy procedures.
MO‐FG‐210‐02: Implementation of Image‐Guided Prostate HDR Brachytherapy Using MR‐Ultrasound Fusion
Authors: Libby B.
Published: June 2015

Ultrasound (US) is one of the most widely used imaging modalities in medical practice. Since US imaging offers real‐time imaging capability, it has becomes an excellent option to provide image guidance for brachytherapy (IGBT). (1) The physics and the fundamental principles of US imaging are presented, and the typical steps required to commission an US system for IGBT is provided for illustration. (2) Application of US for prostate HDR brachytherapy, including partial prostate treatments using MR‐ultrasound co‐registration to enable a focused treatment on the disease within the prostate is also presented. Prostate HDR with US image guidance planning can benefit from real time visualization of the needles, and fusion of the ultrasound images with T2 weighted MR allows the focusing of the treatment to the specific areas of disease within the prostate, so that the entire gland need not be treated. Finally, (3) ultrasound guidance for an eye plaque program is presented. US can be a key component of placement and QA for episcleral plaque brachytherapy for ocular cancer, and the UCLA eye plaque program with US for image guidance is presented to demonstrate the utility of US verification of plaque placement in improving the methods and QA in episcleral plaque brachytherapy.

Learning Objectives:

To understand the physics of an US system and the necessary aspects of commissioning US for image guided brachytherapy (IGBT).

To understand real time planning of prostate HDR using ultrasound, and its application in partial prostate treatments using MR‐ultrasound fusion to focus treatment on disease within the prostate.

To understand the methods and QA in applying US for localizing the target and the implant during a episcleral plaque brachytherapy procedures.
MO‐F‐CAMPUS‐J‐04: One‐Year Analysis of Elekta CBCT Image Quality Using NPS and MTF
Authors: Nakahara S , Tachibana M , Watanabe Y
Published: June 2015

Purpose:

To compare quantitative image quality (IQ) evaluation methods using Noise Power Spectrum (NPS) and Modulation Transfer Function (MTF) with standard IQ analyses for minimizing the observer subjectivity of the standard methods and maximizing the information content.

Methods:

For our routine IQ tests of Elekta XVI Cone‐Beam CT, image noise was quantified by the standard deviation of CT number (CT#) (Sigma) over a small area in an IQ test phantom (CatPhan), and the high spatial resolution (HSR) was evaluated by the number of line‐pairs (LP#) visually recognizable on the image. We also measured the image uniformity, the low contrast resolution ratio, and the distances of two points for geometrical accuracy. For this study, we did additional evaluation of the XVI data for 12 monthly IQ tests by using NPS for noise, MTF for HSR, and the CT#‐to‐density relationship. NPS was obtained by applying Fourier analysis in a small area on the uniformity test section of CatPhan. The MTF analysis was performed by applying the Droege‐Morin (D‐M) method to the line pairs on the phantom. The CT#‐to‐density was obtained for inserts in the low‐contrast test section of the phantom.

Results:

All the quantities showed a noticeable change over the one‐year period. Especially the noise level changed significantly after a repair of the imager. NPS was more sensitive to the IQ change than Sigma. MTF could provide more quantitative and objective evaluation of the HSR. The CT# was very different from the expected CT#; but, the CT#‐to‐density curves were constant within 5% except two months.

Conclusion:

Since the D‐M method is easy to implement, we recommend using MTF instead of the LP# even for routine periodic QA. The month‐to‐month variation of IQ was not negligible; hence a routine IQ test must be performed, particularly after any modification of hardware including detector calibration.
MO‐F‐CAMPUS‐I‐04: Magnetic Resonance Imaging of An in Vitro 3D Tumor Model
Authors: Veiga C , Long T , Siow B , Loizidou M , Royle G , Ricketts K
Published: June 2015

Purpose:

To investigate the use of an in vitro 3D tumor model (tumoroid) as a bio‐phantom for repetitive and sequential magnetic resonance imaging (MRI) studies.

Methods:

The tissue engineered tumoroid comprised an artificial cancer mass (ACM) containing 30 million HT29 cancer cells seeded in a collagen type I matrix, whose density was increased by plastic compression (dry/wet weight=40%). The ACM was embedded in an uncompressed collagen gel that mimicked the tumor stroma, and the tumoroid was incubated for 24h before imaging. Images were acquired using the 1T ICON™ (Bruker Corporation, Billerica, MA) MRI scanner. T1 maps were calculated using an IR‐RARE sequence (TE=12ms, TR=10000ms, 7 inversion times), while for T2 maps a MSME technique (TR=6000ms, 16 echoes) was used. T1 and T2 fittings were performed using a pixel‐wise approach to produce relaxometric parametric maps.

Results:

The images acquired and corresponding T1 and T2 maps indicate contrast between the ACM and the stroma. T1 was 2500 and 2800ms, while T2 was 520 and 760ms, for the ACM and stroma respectively. The ACM construct was not homogenous and internal features were visible, which can be explained by local gradients of cell and/or collagen density. The viability of the cells was confirmed via confocal microscopy for several days after the imaging session, demonstrating the suitability of the tumoroid for sequential imaging studies.

Conclusions:

We have engineered a tumor model compatible with repetitive and sequential MRI. We found T1 and T2 contrast between the ACM and stroma using a pre‐clinical MRI scanner. The model, which enables controllable cell and matrix densities, has potential for a wide range of applications in radiotherapy, such as to study tumor progression and to validate imaging biomarkers. Further work is necessary to understand the mechanisms behind the contrast achieved, and to correlate findings with biology and histology data.
MO‐F‐CAMPUS‐I‐05: Quantitative ADC Measurement of Esophageal Cancer Before and After Chemoradiation
Authors: Yang L , Son JB , Ma J , Cheng S , Hazle J , Carter BW , Lin S
Published: June 2015

Purpose:

We investigated whether quantitative diffusion imaging can be used as an imaging biomarker for early prediction of treatment response of esophageal cancer.

Methods:

Eight patients with esophageal cancer underwent a baseline and an interim MRI studies during chemoradiation on a 3T whole body MRI scanner with an 8‐channel torso phased array coil. Each MRI study contained two axial diffusion‐weighted imaging (DWI) series with a conventional DWI sequence and a reduced field‐of‐view DWI sequence (FOCUS) of varying b‐values. ADC maps with two b‐values were computed from conventional DWI images using a mono‐exponential model. For each of DWI sequences, separate ADCall was computed by fitting the signal intensity of images with all the b‐values to a single exponential model. For the FOCUS sequence, a bi‐exponential model was used to extract perfusion and diffusion coefficients (ADCperf and ADCdiff) and their contributions to the signal decay. A board‐certified radiologist contoured the tumor region and mean ADC values and standard deviations of tumor and muscle ROIs were recorded from different ADC maps.

Results:

Our results showed that (1) the magnitude of ADCs from the same ROIs by the different analysis methods can be substantially different. (2) For a given method, the change between the baseline and interim muscle ADCs was relatively small (≤10%). In contrast, the change between the baseline and interim tumor ADCs was substantially larger, with the change in ADCdiff by FOCUS DWI showing the largest percentage change of 73.2%. (3) The range of the relative change of a specific parameter for different patients was also different.

Conclusion:

Presently, we do not have the final pathological confirmation of the treatment response for all the patients. However, for a few patients whose surgical specimen is available, the quantitative ADC changes have been found to be useful as a potential predictor for treatment response.
MO‐G‐304‐04: Generating Well‐Dispersed Representations of the Pareto Front for Multi‐Criteria Optimization in Radiation Treatment Planning
Authors: Kirlik G , Zhang H
Published: June 2015

Purpose:

To present a novel multi‐criteria optimization (MCO) solution approach that generates well‐dispersed representation of the Pareto front for radiation treatment planning.

Methods:

Different algorithms have been proposed and implemented in commercial planning software to generate MCO plans for external‐beam radiation therapy. These algorithms consider convex optimization problems. We propose a grid‐based algorithm to generate well‐dispersed treatment plans over Pareto front. Our method is able to handle nonconvexity in the problem to deal with dose‐volume objectives/constraints, biological objectives, such as equivalent uniform dose (EUD), tumor control probability (TCP), normal tissue complication probability (NTCP), etc. In addition, our algorithm is able to provide single MCO plan when clinicians are targeting narrow bounds of objectives for patients. In this situation, usually none of the generated plans were within the bounds and a solution is difficult to identify via manual navigation. We use the subproblem formulation utilized in the grid‐based algorithm to obtain a plan within the specified bounds. The subproblem aims to generate a solution that maps into the rectangle defined by the bounds. If such a solution does not exist, it generates the solution closest to the rectangle. We tested our method with 10 locally advanced head and neck cancer cases.

Results:

8 objectives were used including 3 different objectives for primary target volume, high‐risk and low‐risk target volumes, and 5 objectives for each of the organs‐at‐risk (OARs) (two parotids, spinal cord, brain stem and oral cavity). Given tight bounds, uniform dose was achieved for all targets while as much as 26% improvement was achieved in OAR sparing comparing to clinical plans without MCO and previously proposed MCO method.

Conclusion:

Our method is able to obtain well‐dispersed treatment plans to attain better approximation for convex and nonconvex Pareto fronts. Single treatment plan can be achieved when given bounds on the objectives.
TU‐A‐213‐00: MBAs for Medical Physicists: Business School Basics
Authors: Tarver Russell
Published: June 2015

A broad survey of business schools and their potential to augment the utility of practicing medical physicists will be presented in didactic format. Topics will include: 1) business education vs. medical and scientific education, 2) the MBA degree vs. alternative degrees/certificates, 3) distinguishing features among MBA programs, 4) the MBA admissions process and student experience, 5) a description of the typical MBA curriculum and its relevance to clinical practice, and 6) themes to consider when performing a cost‐benefit analysis of whether or not to enroll in an MBA program.

This session is the first of two consecutive sessions exploring the professional impact of supplementing medical physics credentials with formal business education, and is also part of a larger block of sessions concentrating on the Management, Business and Supervision aspects of Medical Physics.

Learning Objectives:

To consider medical physics credentials within a broader educational and economic context.

To gain a sense of what is taught in business schools and how medical physicists might become more effective with this knowledge.

To discern market segments among MBA students and product differentiation among MBA programs.
TU‐A‐304‐00: Imaging, Treatment Planning, and QA for Stereotactic Body Radiation Therapy (SBRT)
Authors: Xing Lei
Published: June 2015

Increased use of SBRT and hypo fractionation in radiation oncology practice has posted a number of challenges to medical physicist, ranging from planning, image‐guided patient setup and on‐treatment monitoring, to quality assurance (QA) and dose delivery. This symposium is designed to provide updated knowledge necessary for the safe and efficient implementation of SBRT in various linac platforms, including the emerging digital linacs equipped with high dose rate FFF beams. Issues related to 4D CT, PET and MRI simulations, 3D/4D CBCT guided patient setup, real‐time image guidance during SBRT dose delivery using gated/un‐gated VMAT or IMRT, and technical advancements in QA of SBRT (in particular, strategies dealing with high dose rate FFF beams) will be addressed. The symposium will help the attendees to gain a comprehensive understanding of the SBRT workflow and facilitate their clinical implementation of the state‐of‐art imaging and planning techniques.

Learning Objectives:

Present background knowledge of SBRT, describe essential requirements for safe implementation of SBRT, and discuss issues specific to SBRT treatment planning and QA.

Update on the use of multi‐dimensional (3D and 4D) and multi‐modality (CT, beam‐level X‐ray imaging, pre‐ and on‐treatment 3D/4D MRI, PET, robotic ultrasound, etc.) for reliable guidance of SBRT.

Provide a comprehensive overview of emerging digital linacs and summarize the key geometric and dosimetric features of the new generation of linacs for substantially improved SBRT.

Discuss treatment planning and quality assurance issues specific to SBRT.

Research grant from Varian Medical Systems
TU‐B‐210‐01: MRg HIFU ‐ Bone and Soft Tissue Tumor Ablation
Authors: Ghanouni P.
Published: June 2015

MR guided focused ultrasound (MRgFUS), or alternatively high‐intensity focused ultrasound (MRgHIFU), is approved for thermal ablative treatment of uterine fibroids and pain palliation in bone metastases. Ablation of malignant tumors is under active investigation in sites such as breast, prostate, brain, liver, kidney, pancreas, and soft tissue. Hyperthermia therapy with MRgFUS is also feasible, and may be used in conjunction with radiotherapy and for local targeted drug delivery. MRI allows in situ target definition and provides continuous temperature monitoring and subsequent thermal dose mapping during HIFU. Although MRgHIFU can be very precise, treatment of mobile organs is challenging and advanced techniques are required because of artifacts in MR temperature mapping, the need for intercostal firing, and need for gated HIFU or tracking of the lesion in real time. The first invited talk, “MR guided Focused Ultrasound Treatment of Tumors in Bone and Soft Tissue”, will summarize the treatment protocol and review results from treatment of bone tumors. In addition, efforts to extend this technology to treat both benign and malignant soft tissue tumors of the extremities will be presented. The second invited talk, “MRI guided High Intensity Focused Ultrasound – Advanced Approaches for Ablation and Hyperthermia”, will provide an overview of techniques that are in or near clinical trials for thermal ablation and hyperthermia, with an emphasis of applications in abdominal organs and breast, including methods for MRTI and tracking targets in moving organs.

Learning Objectives:

Learn background on devices and techniques for MR guided HIFU for cancer therapy

Understand issues and current status of clinical MRg HIFU

Understand strategies for compensating for organ movement during MRgHIFU

Understand strategies for strategies for delivering hyperthermia with MRgHIFU

CM ‐ research collaboration with Philips
TU‐CD‐213‐00: Administrative Aspects of Medical Physics
Authors: Johnson Jennifer Lynn
Published: June 2015

As part of the AAPM's Scope of Practice, medical physicists are expected to collaborate effectively with practioners and allied health care providers. Interpersonal skills such as communication, negotiation and persuasion are vital for successful collaboration to achieve shared goals. This session will provide some theoretical background of these interpersonal skills as well as specific techniques and practical tools to influence others. Applications of these interpersonal skills for administrative and human resource management purposes vital to medical physicists will be shared. Session attendees will gain knowledge and tools to help them effectively collaborate with administrative and physician leaders in areas such as capital and human resource selection, prioritization, and implementation. Participants will hear methods of how to articulate their goals and to understand the goals of administration, helping ensure alignment of purpose.

Session speakers will present one of the topics: equipment selection, budget creation, contracts, and program‐related policy development. Specifics may include designing a business case in language that administrators understand, calculating the prioritization of budget requests, and influencing policies for safe and effective care. Human resource topics may include staffing justification, recruitment for fit, employment contracts, and benefits. Speakers will provide examples in both radiation therapy and diagnostic imaging departments and will share experiences and outcomes of their approaches for better results.

Learning Objectives:

After this course attendees will be better able to

Understand the shared goal between administrative and physicist leadership.

Articulate the “why” of the technical or human resource need.

Utilize communication, negotiation and persuasion tools to improve collaboration.
TU‐CD‐213‐02: Communication, Negotiation, and Persuasion: Approaches for Better Results
Authors: Clements J.
Published: June 2015

As part of the AAPM's Scope of Practice, medical physicists are expected to collaborate effectively with practioners and allied health care providers. Interpersonal skills such as communication, negotiation and persuasion are vital for successful collaboration to achieve shared goals. This session will provide some theoretical background of these interpersonal skills as well as specific techniques and practical tools to influence others. Applications of these interpersonal skills for administrative and human resource management purposes vital to medical physicists will be shared. Session attendees will gain knowledge and tools to help them effectively collaborate with administrative and physician leaders in areas such as capital and human resource selection, prioritization, and implementation. Participants will hear methods of how to articulate their goals and to understand the goals of administration, helping ensure alignment of purpose.

Session speakers will present one of the topics: equipment selection, budget creation, contracts, and program‐related policy development. Specifics may include designing a business case in language that administrators understand, calculating the prioritization of budget requests, and influencing policies for safe and effective care. Human resource topics may include staffing justification, recruitment for fit, employment contracts, and benefits. Speakers will provide examples in both radiation therapy and diagnostic imaging departments and will share experiences and outcomes of their approaches for better results.

Learning Objectives:

After this course attendees will be better able to

Understand the shared goal between administrative and physicist leadership.

Articulate the “why” of the technical or human resource need.

Utilize communication, negotiation and persuasion tools to improve collaboration.
TU‐CD‐304‐01: FEATURED PRESENTATION and BEST IN PHYSICS (THERAPY): Trajectory Modulated Arc Therapy: Development of Novel Arc Delivery Techniques Integrating Dynamic Table Motion for Extended Volume Treatments
Authors: Chin E , Otto K , Hoppe R , Million L , Loo B , Koong A , Xing L , Hsu A , Fahimian B
Published: June 2015

Purpose:

Integration of coordinated robotic table motion with inversely‐planned arc delivery has the potential to resolve table‐top delivery limitations of large‐field treatments such as Total Body Irradiation (TBI), Total Lymphoid Irradiation (TLI), and Cranial‐Spinal Irradiation (CSI). We formulate the foundation for Trajectory Modulated Arc Therapy (TMAT), and using Varian Developer Mode capabilities, experimentally investigate its practical implementation for such techniques.

Methods:

A MATLAB algorithm was developed for inverse planning optimization of the table motion, MLC positions, and gantry motion under extended‐SSD geometry. To maximize the effective field size, delivery trajectories for TMAT TBI were formed with the table rotated at 270° IEC and dropped vertically to 152.5cm SSD. Preliminary testing of algorithm parameters was done through retrospective planning analysis. Robotic delivery was programmed using custom XML scripting on the TrueBeam Developer Mode platform. Final dose was calculated using the Eclipse AAA algorithm. Initial verification of delivery accuracy was measured using OSLDs on a solid water phantom of varying thickness.

Results:

A comparison of DVH curves demonstrated that dynamic couch motion irradiation was sufficiently approximated by static control points spaced in intervals of less than 2cm. Optimized MLC motion decreased the average lung dose to 68.5% of the prescription dose. The programmed irradiation integrating coordinated table motion was deliverable on a TrueBeam STx linac in 6.7 min. With the couch translating under an open 10cmx20cm field angled at 10°, OSLD measurements along the midline of a solid water phantom at depths of 3, 5, and 9cm were within 3% of the TPS AAA algorithm with an average deviation of 1.2%.

Conclusion:

A treatment planning and delivery system for Trajectory Modulated Arc Therapy of extended volumes has been established and experimentally demonstrated for TBI. Extension to other treatment techniques such as TLI and CSI is readily achievable through the developed platform.

Grant Funding by Varian Medical Systems.
TU‐CD‐BRD‐04: UCLA Experience, with Focus On Developing Metrics and Using RO‐ILS
Authors: Beron P.
Published: June 2015

It has long been standard practice in radiation oncology to report internally when a patient's treatment has not gone as planned and to report events to regulatory agencies when legally required. Most potential errors are caught early and never affect the patient. Quality assurance steps routinely prevent errors from reaching the patient, and these “near misses” are much more frequent than treatment errors. A growing number of radiation oncology facilities have implemented incident learning systems to report and analyze both errors and near misses. Using the term “incident learning” instead of “event reporting” emphasizes the need to use these experiences to change the practice and make future errors less likely and promote an educational, non‐punitive environment.

There are challenges in making such a system practical and effective. Speakers from institutions of different sizes and practice environments will share their experiences on how to make such a system work and what benefits their clinics have accrued. Questions that will be addressed include:

How to create a system that is easy for front line staff to access

How to motivate staff to report

How to promote the system as positive and educational and not punitive or demeaning

How to organize the team for reviewing and responding to reports

How to prioritize which reports to discuss in depth

How not to dismiss the rest

How to identify underlying causes

How to design corrective actions and implement change

How to develop useful statistics and analysis tools

How to coordinate a departmental system with a larger risk management system

How to do this without a dedicated quality manager

Some speakers’ experience is with in‐house systems and some will share experience with the AAPM/ASTRO national Radiation Oncology Incident Learning System (RO‐ILS). Reports intended to be of value nationally need to be comprehensible to outsiders; examples of useful reports will be shown.

There will be ample time set aside for audience members to contribute to the discussion.

Learning Objectives:

Learn how to promote the use of an incident learning system in a clinic.

Learn how to convert “event reporting” into “incident learning”.

See examples of practice changes that have come out of learning systems.

Learn how the RO‐ILS system can be used as a primary internal learning system.

Learn how to create succinct, meaningful reports useful to outside readers.

Gary Ezzell chairs the AAPM committee overseeing RO‐ILS and has received an honorarium from ASTRO for working on the committee reviewing RO‐ILS reports.

Derek Brown is a director of TreatSafely.org.

Brett Miller has previously received travel expenses and an honorarium from Varian.

Phillip Beron has nothing to report.
TU‐CD‐BRB‐04: Automated Radiomic Features Complement the Prognostic Value of VASARI in the TCGA‐GBM Dataset
Authors: Velazquez E Rios , Narayan V , Grossmann P , Dunn W , Gutman D , Aerts H
Published: June 2015

Purpose:

To compare the complementary prognostic value of automated Radiomic features to that of radiologist‐annotated VASARI features in TCGA‐GBM MRI dataset.

Methods:

For 96 GBM patients, pre‐operative MRI images were obtained from The Cancer Imaging Archive. The abnormal tumor bulks were manually defined on post‐contrast T1w images. The contrast‐enhancing and necrotic regions were segmented using FAST. From these sub‐volumes and the total abnormal tumor bulk, a set of Radiomic features quantifying phenotypic differences based on the tumor intensity, shape and texture, were extracted from the post‐contrast T1w images. Minimum‐redundancy‐maximum‐relevance (MRMR) was used to identify the most informative Radiomic, VASARI and combined Radiomic‐VASARI features in 70% of the dataset (training‐set). Multivariate Cox‐proportional hazards models were evaluated in 30% of the dataset (validation‐set) using the C‐index for OS. A bootstrap procedure was used to assess significance while comparing the C‐Indices of the different models.

Results:

Overall, the Radiomic features showed a moderate correlation with the radiologist‐annotated VASARI features (r = −0.37 – 0.49); however that correlation was stronger for the Tumor Diameter and Proportion of Necrosis VASARI features (r = −0.71 – 0.69). After MRMR feature selection, the best‐performing Radiomic, VASARI, and Radiomic‐VASARI Cox‐PH models showed a validation C‐index of 0.56 (p = NS), 0.58 (p = NS) and 0.65 (p = 0.01), respectively. The combined Radiomic‐VASARI model C‐index was significantly higher than that obtained from either the Radiomic or VASARI model alone (p = <0.001).

Conclusion:

Quantitative volumetric and textural Radiomic features complement the qualitative and semi‐quantitative annotated VASARI feature set. The prognostic value of informative qualitative VASARI features such as Eloquent Brain and Multifocality is increased with the addition of quantitative volumetric and textural features from the contrast‐enhancing and necrotic tumor regions. These results should be further evaluated in larger validation cohorts.
TU‐CD‐BRA‐01: A Novel 3D Registration Method for Multiparametric Radiological Images
Authors: Akhbardeh A , Parekth VS , Jacobs MA
Published: June 2015

Purpose:

Multiparametric and multimodality radiological imaging methods, such as, magnetic resonance imaging(MRI), computed tomography(CT), and positron emission tomography(PET), provide multiple types of tissue contrast and anatomical information for clinical diagnosis. However, these radiological modalities are acquired using very different technical parameters, e.g.,field of view(FOV), matrix size, and scan planes, which, can lead to challenges in registering the different data sets. Therefore, we developed a hybrid registration method based on 3D wavelet transformation and 3D interpolations that performs 3D resampling and rotation of the target radiological images without loss of information

Methods:

T1‐weighted, T2‐weighted, diffusion‐weighted‐imaging(DWI), dynamic‐contrast‐enhanced(DCE) MRI and PET/CT were used in the registration algorithm from breast and prostate data at 3T MRI and multimodality(PET/CT) cases. The hybrid registration scheme consists of several steps to reslice and match each modality using a combination of 3D wavelets, interpolations, and affine registration steps. First, orthogonal reslicing is performed to equalize FOV, matrix sizes and the number of slices using wavelet transformation. Second, angular resampling of the target data is performed to match the reference data. Finally, using optimized angles from resampling, 3D registration is performed using similarity transformation(scaling and translation) between the reference and resliced target volume is performed. After registration, the mean‐square‐error(MSE) and Dice Similarity(DS) between the reference and registered target volumes were calculated.

Results:

The 3D registration method registered synthetic and clinical data with significant improvement(p<0.05) of overlap between anatomical structures. After transforming and deforming the synthetic data, the MSE and Dice similarity were 0.12 and 0.99. The average improvement of the MSE in breast was 62%(0.27 to 0.10) and prostate was 63%(0.13 to 0.04;p<0.05). The Dice similarity was in breast 8%(0.91 to 0.99) and for prostate was 89%(0.01 to 0.90;p<0.05)

Conclusion:

Our 3D wavelet hybrid registration approach registered diverse breast and prostate data of different radiological images(MR/PET/CT) with a high accuracy.
TU‐CD‐BRA‐02: Comparing Mutual Information and Gradient Magnitude Metrics for Deformable Image Registration
Authors: Gertsenshteyn I , Tyagi N , Farjam R , Apte A , Sharp G
Published: June 2015

Purpose:

Deformable image registration between CT and MRI remains a challenge due to variability in contrast, homogeneity, and field of view. This study aims to determine whether an optimized Mutual Information (MI) or Gradient Magnitude (GM) metric provides favorable results in the head and neck region.

Methods:

Head and neck CT and MR images were acquired for 14 patients as part of an MRI simulation study with a dual echo mDixon (in phase) T1 fast field echo sequence. Each pair of scans is registered with MRI as the reference image using the GM and MI metrics, where MI was optimized by controlling histogram parameters. Results are observed visually, and quantitatively measured by comparing Dice coefficient and Hausdorff distance of manually contoured bone structures.

Results:

Using the optimized GM metric, the average Dice coefficient is 0.52 ± 0.16; the average Hausdorff distance is 7.5 ± 1.9 mm. Using the optimized MI metric, the average Dice coefficient is 0.55 ± 0.085; the average Hausdorff distance is 6.6 ± 1.4 mm.

Conclusion:

While both metrics performed similarly, the MI metric has a higher Dice coefficient than the GM metric, and a lower Hausdorff distance. This suggests image registration with the Mutual Information metric may be preferred.
TU‐CD‐BRA‐03: Left Ventricle Segmentation with a Coupled Length Regularization and Sparse Shape Prior
Authors: Liu W , Ruan D
Published: June 2015

Purpose:

To perform accurate segmentation on left ventricles from Cine MR images

Methods:

We have developed a novel variational segmentation method that incorporates prior knowledge on both geometrical relations and shapes of the endocardium and epicardium. In contrast to conventional approaches that preserve a constant distance between the endo‐ and epicardial contours, we propose to maintain a smoothly varying distance between the endo‐ and epicardium represented by two separate level set functions, which is more robust to shape variations across slices and phases among different patients. The coupled level set representation further allows us to incorporate a sparse composite shape prior to boost the performance. A robust data fidelity of Gaussian mixture is utilized to represent overlapped intensity distributions of each cardiac region under the condition of insufficient gradient information. We evaluated the proposed method on datasets from MICCAI left ventricle segmentation challenge, and compared our method against other state‐of‐the‐art approaches based on Dice similarity coefficient (DSC).

Results:

Our method successfully segmented all left ventricles in 15 validation datasets from patients of different pathologies. It achieved competitive if not better DSC accuracy compared to other state‐of‐the‐art methods, with mean DSC of 0.89 and standard deviation of 0.04 on endocardium segmentation, and mean DSC of 0.94 and standard deviation of 0.01 on epicardium segmentation.

Conclusion:

Introducing anatomy‐specific geometric coupling and sparse composite shape priors on endo‐ and epicardium, in addition to length regularization, into the variational method has demonstrated its advantage in the challenging problem of left ventricle segmentation. A joint left and right ventricle segmentation method is under development.
TU‐CD‐BRA‐07: A Comparison of Demons Image Registration Algorithms to Monitor Longitudinal Changes in Knee Cartilage: Data From the OsteoArthritis Initiative (OAI)
Authors: Hoang U , Sinha U , Sinha U
Published: June 2015

Purpose:

To develop accurate tools to quantify small and localized changes in cartilage morphology to facilitate comparisons between patient cohorts with varying degrees of osteoarthritis (OA) as well as to track longitudinal changes(normal progression and response to treatment).

Methods:

We implemented and compared the registration accuracy of four variants of the demons algorithm on magnetic resonance cartilage image volumes. The algorithms are four variants of the Demon's algorithm: symmetric simple demons (SMSD), symmetric evolved demons (SMED), inverse‐consistent simple demons (ICSD), and inverse‐consistent evolved demons (ICED). The registration algorithms were also evaluated for the accuracy of the average Jacobians. The average Jacobian of the cartilage was compared to the ratio of volume change for validation. Evaluation was performed on 36 subjects using the baseline and later time point images acquired after 12 months.

Results:

The symmetric evolved demons algorithm provided the best in registration accuracy evaluated using quantitative metrics of mean squared error and voxel overlap. The symmetric simple demons and symmetric evolved demons performed equally well in terms of the Jacobians.

Conclusion:

Approximately 27 millions adults age 25 and older diagnosed with OA; however, cartilage loss with disease progression is small and localized to sub‐regions of the cartilage. It is desirable to develop accurate methods that can automatically extract measures of cartilage volume and thickness (global and local). The techniques developed here will be used, in future studies, to explore differences in cohorts segregated by disease severity and correlation of local changes to clinical variables.
TU‐CD‐BRA‐12: Coupling PET Image Restoration and Segmentation Using Variational Method with Multiple Regularizations
Authors: Li L , Lu W , Tan S
Published: June 2015

Purpose:

To propose a new variational method which couples image restoration with tumor segmentation for PET images using multiple regularizations.

Methods:

Partial volume effect (PVE) is a major degrading factor impacting tumor segmentation accuracy in PET imaging. The existing segmentation methods usually need to take prior calibrations to compensate PVE and they are highly system‐dependent. Taking into account that image restoration and segmentation can promote each other and they are tightly coupled, we proposed a variational method to solve the two problems together. Our method integrated total variation (TV) semi‐blind deconvolution and Mumford‐Shah (MS) segmentation. The TV norm was used on edges to protect the edge information, and the L₂ norm was used to avoid staircase effect in the no‐edge area. The blur kernel was constrained to the Gaussian model parameterized by its variance and we assumed that the variances in the X‐Y and Z directions are different. The energy functional was iteratively optimized by an alternate minimization algorithm. Segmentation performance was tested on eleven patients with non‐Hodgkin's lymphoma, and evaluated by Dice similarity index (DSI) and classification error (CE). For comparison, seven other widely used methods were also tested and evaluated.

Results:

The combination of TV and L₂ regularizations effectively improved the segmentation accuracy. The average DSI increased by around 0.1 than using either the TV or the L₂ norm. The proposed method was obviously superior to other tested methods. It has an average DSI and CE of 0.80 and 0.41, while the FCM method — the second best one — has only an average DSI and CE of 0.66 and 0.64.

Conclusion:

Coupling image restoration and segmentation can handle PVE and thus improves tumor segmentation accuracy in PET. Alternate use of TV and L2 regularizations can further improve the performance of the algorithm.

This work was supported in part by National Natural Science Foundation of China (NNSFC), under Grant No.61375018, and Fundamental Research Funds for the Central Universities, under Grant No. 2012QN086. Wei Lu was supported in part by the National Institutes of Health (NIH) Grant No. R01 CA172638.
TU‐EF‐303‐01: Altered Mechanical Poperties of Cells and Nuclei in Cancer
Authors: Rowat A.
Published: June 2015

Many medical physics diagnostic and therapeutic developments have significant overlap with biophysical approaches to measuring and modeling molecular and cellular systems. Although these methods may differ dramatically in terms of temporal and spatial scales, many of the underlying concepts are identical, suggesting potential synergies across the scales. For example, while clinical imaging is typically in the (sub)millimeter and second regime, biophysical imaging technologies reach sub‐nanometer and sub‐picosecond scales. Despite these scale differences, the use of molecular labeling, resulting large datasets, and need for quantitative analysis methods are similar, and solutions developed for one application are easily translated to others. Similarly, mathematical models used to understand clinical responses are often based on molecular and cellular networks that have been elucidated by biophysical studies. In turn, such models are directly useful for guiding on‐going biophysical and biomedical research. Relevant biophysical applications are found in the cancer, neuroscience, and cardiac fields, which are also research focus areas for many AAPM members. Presentations by physicists working in biophysics will explore potential synergies with diagnostic and therapeutic medical physics, as well as help identify areas of common interest that would be ripe for novel collaborations.

Learning Objectives:

1.To learn about differences in temporal and spatial scales of medical physics and biophysics

To learn about common methods used in medical physics and biophysics

To learn about synergistic opportunities between medical physics and biophysics