bluuebunny/crossref_metadata_2025 huggingface dataset:
WE‐EF‐210‐07: Development of a Minimally Invasive Photo Acoustic Imaging System for Early Prostate Cancer Detection
Authors: Sano M , Yousefi S , Xing L
Published: June 2015

Purpose:

The objective of this work is to design, implement and characterize a catheter‐based ultrasound/photoacoustic imaging probe for early‐diagnosis of prostate cancer and to aid in image‐guided radiation therapy.

Methods:

The need to image across 6–10cm of tissue to image the whole prostate gland limits the resolution achievable with a transrectal ultrasound approach. In contrast, the urethra bisects the prostate gland, providing a minimally invasive pathway for deploying a high resolution ultrasound transducer. Utilizing a high‐frequency (20MHz) ultrasound/photoacoustic probe, high‐resolution structural and molecular imaging of the prostate tissue is possible. A custom 3D printed probe containing a high‐frequency single‐element ultrasound transducer is utilized. The diameter of the probe is designed to fit inside a Foley catheter and the probe is rotated around the central axis to achieve a circular B‐scan. A custom ultrasound amplifier and receiver was set up to trigger the ultrasound pulse transmission and record the reflected signal. The reconstructed images were compared to images generated by traditional 5 MHz ultrasound transducers.

Results:

The preliminary results using the high‐frequency ultrasound probe show that it is possible to resolve finely detailed information in a prostate tissue phantom that was not achievable with previous low‐frequency ultrasound systems. Preliminary ultrasound imaging was performed on tissue mimicking phantom and sensitivity and signal‐to‐noise ratio of the catheter was measured.

Conclusion:

In order to achieve non‐invasive, high‐resolution, structural and molecular imaging for early‐diagnosis and image‐guided radiation therapy of the prostate tissue, a transurethral catheter was designed. Structural/molecular imaging using ultrasound/photoacoustic of the prostate tissue will allow for localization of hyper vascularized areas for early‐stage prostate cancer diagnosis.
WE‐F‐304‐05: Cranial TCP/NTCP Modeling Insights and Caveats
Authors: El Naqa I.
Published: June 2015

Stereotactic Body Radiation Therapy (SBRT) was introduced clinically more than twenty years ago, and many subsequent publications have reported safety and efficacy data. The AAPM Working Group on Biological Effects of Hypofractionated Radiotherapy/SBRT (WGSBRT) extracted published treatment outcomes data from extensive literature searches to summarize and construct tumor control probability (TCP) and normal tissue complication probability (NTCP) models for six anatomical regions: Cranial, Head and Neck, Thoracic, Abdominal, Pelvic, and Spinal. In this session, we present the WGSBRT's work for cranial sites, and recurrent head and neck cancer. From literature‐based data and associated models, guidelines to aid with safe and effective hypofractionated radiotherapy treatment are being determined. Further, the ability of existing and proposed radiobiological models to fit these data is considered as to the ability to distinguish between the linear‐quadratic and alternative radiobiological models such as secondary cell death from vascular damage, immunogenic, or bystander effects. Where appropriate, specific model parameters are estimated. As described in “The lessons of QUANTEC,” (1), lack of adequate reporting standards continues to limit the amount of useful quantitative information that can be extracted from peer‐reviewed publications. Recommendations regarding reporting standards are considered, to enable such reviews to achieve more complete characterization of clinical outcomes.

1 Jackson A, Marks LB, Bentzen SM, Eisbruch A, Yorke ED, Ten Haken RK, Constine LS, Deasy JO. The lessons of QUANTEC: recommendations for reporting and gathering data on dose‐volume dependencies of treatment outcome. Int J Radiat Oncol Biol Phys. 2010 Mar 1;76(3 Suppl):S155–60.

Learning Objectives:

Describe the techniques, types of cancer and dose schedules used in treating recurrent H&N cancers with SBRT

List the radiobiological models that compete with the linear‐quadratic model in explaining the results of hypofractionated RT

Describe the dose/volume metrics that are considered safe in SBRT treatment of tumors near the optic structures.

Discuss the efficacy of hypofractionation and dosing schedules used in treating vestibular schwannomas

Identify some difficulties in modeling TCP and NTCP for cranial tumors treated with hypofractionation.

One moderator, Dr. Grimm, designed and holds intellectual property rights to the DVH Evaluator software tool which is an FDA‐cleared product in commercial use, and can analyze some of this data.

No others have relevant conflicts of interest.
WE‐F‐213‐01: Building, Maintaining and Improving Physics Residency Programs
Authors: Klein E.
Published: June 2015

In this session we will discuss the key steps for building, maintaining and improving a physics residency program. The initial momentum starts with a secure commitment of; a program director, physics faculty, physicians, key technical personnel, and, of course, administration. The ultimate goal is to build a strong clinical physicist who practice independently and/or work in an interdisciplinary team. Part of the initiation is to find out the right balance of training, resident empowerment, and service contributed back to the clinic.

Another key step that will be discussed is the recruitment of resident candidates. Namely, where the residents are coming from, what their educational background is, and most importantly during interviews, how to gauge what makes an ideal resident. Experiences on the first year of Medphys Match will be shared as well as strategies for placement following graduation.

The key to maintenance of a residency program is to not allow stagnation, but rather to constantly update. Examples will be given of evolution of programs in terms of the didactic and clinical rotational components. In addition, how to allocate the resident developmental work, whether it be clinical or benchmark, without disrupting training. We will also discuss how to evaluate faculty on the ownership they take regarding resident training. We will discuss both therapy and imaging programs.

Finally, we will share experiences on steps to continually improve one's program.

Learning Objectives:

To obtain from the experience of long standing programs the lessons learned.

To find out what historically has worked out to be ideal resident candidates.

Guidelines for continually improving a program.
WE‐F‐213‐02: Building, Maintaining and Improving Physics Residency Programs
Authors: Nye J.
Published: June 2015

In this session we will discuss the key steps for building, maintaining and improving a physics residency program. The initial momentum starts with a secure commitment of; a program director, physics faculty, physicians, key technical personnel, and, of course, administration. The ultimate goal is to build a strong clinical physicist who practice independently and/or work in an interdisciplinary team. Part of the initiation is to find out the right balance of training, resident empowerment, and service contributed back to the clinic.

Another key step that will be discussed is the recruitment of resident candidates. Namely, where the residents are coming from, what their educational background is, and most importantly during interviews, how to gauge what makes an ideal resident. Experiences on the first year of Medphys Match will be shared as well as strategies for placement following graduation.

The key to maintenance of a residency program is to not allow stagnation, but rather to constantly update. Examples will be given of evolution of programs in terms of the didactic and clinical rotational components. In addition, how to allocate the resident developmental work, whether it be clinical or benchmark, without disrupting training. We will also discuss how to evaluate faculty on the ownership they take regarding resident training. We will discuss both therapy and imaging programs.

Finally, we will share experiences on steps to continually improve one's program.

Learning Objectives:

To obtain from the experience of long standing programs the lessons learned.

To find out what historically has worked out to be ideal resident candidates.

Guidelines for continually improving a program.
WE‐F‐304‐02: Recurrent HNC Treated with SBRT: TCP‐Based Outcome Estimates
Authors: Clump D.
Published: June 2015

Stereotactic Body Radiation Therapy (SBRT) was introduced clinically more than twenty years ago, and many subsequent publications have reported safety and efficacy data. The AAPM Working Group on Biological Effects of Hypofractionated Radiotherapy/SBRT (WGSBRT) extracted published treatment outcomes data from extensive literature searches to summarize and construct tumor control probability (TCP) and normal tissue complication probability (NTCP) models for six anatomical regions: Cranial, Head and Neck, Thoracic, Abdominal, Pelvic, and Spinal. In this session, we present the WGSBRT's work for cranial sites, and recurrent head and neck cancer. From literature‐based data and associated models, guidelines to aid with safe and effective hypofractionated radiotherapy treatment are being determined. Further, the ability of existing and proposed radiobiological models to fit these data is considered as to the ability to distinguish between the linear‐quadratic and alternative radiobiological models such as secondary cell death from vascular damage, immunogenic, or bystander effects. Where appropriate, specific model parameters are estimated. As described in “The lessons of QUANTEC,” (1), lack of adequate reporting standards continues to limit the amount of useful quantitative information that can be extracted from peer‐reviewed publications. Recommendations regarding reporting standards are considered, to enable such reviews to achieve more complete characterization of clinical outcomes.

1 Jackson A, Marks LB, Bentzen SM, Eisbruch A, Yorke ED, Ten Haken RK, Constine LS, Deasy JO. The lessons of QUANTEC: recommendations for reporting and gathering data on dose‐volume dependencies of treatment outcome. Int J Radiat Oncol Biol Phys. 2010 Mar 1;76(3 Suppl):S155–60.

Learning Objectives:

Describe the techniques, types of cancer and dose schedules used in treating recurrent H&N cancers with SBRT

List the radiobiological models that compete with the linear‐quadratic model in explaining the results of hypofractionated RT

Describe the dose/volume metrics that are considered safe in SBRT treatment of tumors near the optic structures.

Discuss the efficacy of hypofractionation and dosing schedules used in treating vestibular schwannomas

Identify some difficulties in modeling TCP and NTCP for cranial tumors treated with hypofractionation.

One moderator, Dr. Grimm, designed and holds intellectual property rights to the DVH Evaluator software tool which is an FDA‐cleared product in commercial use, and can analyze some of this data.

No others have relevant conflicts of interest.
WE‐F‐BRB‐02: Setting the Stage for Incorporation of Toxicity Measures in Treatment Plan Assessments
Authors: Mayo C.
Published: June 2015

Advancements in informatics in radiotherapy are opening up opportunities to improve our ability to assess treatment plans. Models on individualizing patient dose constraints from prior patient data and shape relationships have been extensively researched and are now making their way into commercial products. New developments in knowledge based treatment planning involve understanding the impact of the radiation dosimetry on the patient. Akin to radiobiology models that have driven intensity modulated radiotherapy optimization, toxicity and outcome predictions based on treatment plans and prior patient experiences may be the next step in knowledge based planning. In order to realize these predictions, it is necessary to understand how the clinical information can be captured, structured and organized with ontologies and databases designed for recall. Large databases containing radiation dosimetry and outcomes present the opportunity to evaluate treatment plans against predictions of toxicity and disease response. Such evaluations can be based on dose volume histogram or even the full 3‐dimensional dose distribution and its relation to the critical anatomy.

This session will provide an understanding of ontologies and standard terminologies used to capture clinical knowledge into structured databases; How data can be organized and accessed to utilize the knowledge in planning; and examples of research and clinical efforts to incorporate that clinical knowledge into planning for improved care for our patients.

Learning Objectives:

Understand the role of standard terminologies, ontologies and data organization in oncology

Understand methods to capture clinical toxicity and outcomes in a clinical setting

Understand opportunities to learn from clinical data and its application to treatment planning

Todd McNutt receives funding from Philips, Elekta and Toshiba for some of the work presented
WE‐F‐201‐00: Practical Guidelines for Commissioning Advanced Brachytherapy Dose Calculation Algorithms
Authors: Mourtada Firas , Richardson Susan
Published: June 2015

With the recent introduction of heterogeneity correction algorithms for brachytherapy, the AAPM community is still unclear on how to commission and implement these into clinical practice. The recently‐published AAPM TG‐186 report discusses important issues for clinical implementation of these algorithms. A charge of the AAPM‐ESTRO‐ABG Working Group on MBDCA in Brachytherapy (WGMBDCA) is the development of a set of well‐defined test case plans, available as references in the software commissioning process to be performed by clinical end‐users. In this practical medical physics course, specific examples on how to perform the commissioning process are presented, as well as descriptions of the clinical impact from recent literature reporting comparisons of TG‐43 and heterogeneity‐based dosimetry.

Learning Objectives:

Identify key clinical applications needing advanced dose calculation in brachytherapy.

Review TG‐186 and WGMBDCA guidelines, commission process, and dosimetry benchmarks.

Evaluate clinical cases using commercially available systems and compare to TG‐43 dosimetry
WE‐F‐201‐01: Identify Key Clinical Applications Needing Advanced Dose Calculation in Brachytherapy
Authors: Fulkerson R.
Published: June 2015

With the recent introduction of heterogeneity correction algorithms for brachytherapy, the AAPM community is still unclear on how to commission and implement these into clinical practice. The recently‐published AAPM TG‐186 report discusses important issues for clinical implementation of these algorithms. A charge of the AAPM‐ESTRO‐ABG Working Group on MBDCA in Brachytherapy (WGMBDCA) is the development of a set of well‐defined test case plans, available as references in the software commissioning process to be performed by clinical end‐users. In this practical medical physics course, specific examples on how to perform the commissioning process are presented, as well as descriptions of the clinical impact from recent literature reporting comparisons of TG‐43 and heterogeneity‐based dosimetry.

Learning Objectives:

Identify key clinical applications needing advanced dose calculation in brachytherapy.

Review TG‐186 and WGMBDCA guidelines, commission process, and dosimetry benchmarks.

Evaluate clinical cases using commercially available systems and compare to TG‐43 dosimetry
WE‐F‐201‐02: Review TG‐186 and WGMBDCA Guidelines, Commission Process, and Dosimetry Benchmarks
Authors: Rivard M.
Published: June 2015

With the recent introduction of heterogeneity correction algorithms for brachytherapy, the AAPM community is still unclear on how to commission and implement these into clinical practice. The recently‐published AAPM TG‐186 report discusses important issues for clinical implementation of these algorithms. A charge of the AAPM‐ESTRO‐ABG Working Group on MBDCA in Brachytherapy (WGMBDCA) is the development of a set of well‐defined test case plans, available as references in the software commissioning process to be performed by clinical end‐users. In this practical medical physics course, specific examples on how to perform the commissioning process are presented, as well as descriptions of the clinical impact from recent literature reporting comparisons of TG‐43 and heterogeneity‐based dosimetry.

Learning Objectives:

Identify key clinical applications needing advanced dose calculation in brachytherapy.

Review TG‐186 and WGMBDCA guidelines, commission process, and dosimetry benchmarks.

Evaluate clinical cases using commercially available systems and compare to TG‐43 dosimetry
WE‐G‐304‐03: My Personal Experience
Authors: Curran B.
Published: June 2015

In the past few years, several high‐profile medical physicists found their positions terminated. It is a fact that no medical physics job is a sinecure, and that individuals can be terminated through no fault of their own. Medical physicists need to be prepared for such an occurrence. Termination provisions in an employment contract, whether individually negotiated or as part of an employee manual, are important, and also generally overlooked when one is going into a new job. Coupled with the fact that most states are “at‐will,” that makes for a tough position for any physicist who finds his/her position terminated.

In this course, a medical physicist who is also a practicing attorney will start the discussion with a description of the various types of employment situations and employment agreements. This will be followed by two high‐profile medical physicists who had their positions terminated in recent years, who will describe their experiences, including answering such questions as

How much time were you given before termination was effective?

Did you have any foreshadowing of what was coming?

How did you deal with the termination?

Given hindsight, what would you have done differently to mitigate the effects of your termination?

During job interviews, are there ways to open closets to find the skeletons?

What advice would you give medical physicists if faced with a similar situation?

What can you negotiate in a termination agreement?

What kinds of termination agreements could be presented?

The symposium will conclude with a panel discussion.

Learning Objectives:

Identify the various types of employment contracts with an emphasis on termination provisions.

Recognize the implications of non‐compete clauses in employment contracts.

Recognize the possibility of termination of employment.

Identify ways to recognize possibly poor employment situations

Identify steps that one could take to mitigate the effects of termination.
WE‐G‐BRD‐01: A Data‐Driven 4D‐MRI Motion Model to Estimate Full Field‐Of‐View Abdominal Motion From 2D Image Navigators During MR‐Linac Treatment
Authors: Stemkens B , Tijssen RHN , de Senneville B Denis , Lagendijk JJW , van den Berg CAT
Published: June 2015

Purpose:

To estimate full field‐of‐view abdominal respiratory motion from fast 2D image navigators using a 4D‐MRI based motion model. This will allow for radiation dose accumulation mapping during MR‐Linac treatment.

Methods:

Experiments were conducted on a Philips Ingenia 1.5T MRI. First, a retrospectively ordered 4D‐MRI was constructed using 3D transient‐bSSFP with radial in‐plane sampling. Motion fields were calculated through 3D non‐rigid registration. From these motion fields a PCA‐based abdominal motion model was constructed and used to warp a 3D reference volume to fast 2D cine‐MR image navigators that can be used for real‐time tracking. To test this procedure, a time‐series consisting of two interleaved orthogonal slices (sagittal and coronal), positioned on the pancreas or kidneys, were acquired for 1m38s (dynamic scan‐time=0.196ms), during normal, shallow, or deep breathing. The coronal slices were used to update the optimal weights for the first two PCA components, in order to warp the 3D reference image and construct a dynamic 4D‐MRI time‐series. The interleaved sagittal slices served as an independent measure to test the model's accuracy and fit. Spatial maps of the root‐mean‐squared error (RMSE) and histograms of the motion differences within the pancreas and kidneys were used to evaluate the method.

Results:

Cranio‐caudal motion was accurately calculated within the pancreas using the model for normal and shallow breathing with an RMSE of 1.6mm and 1.5mm and a histogram median and standard deviation below 0.2 and 1.7mm, respectively. For deep‐breathing an underestimation of the inhale amplitude was observed (RMSE=4.1mm). Respiratory‐induced antero‐posterior and lateral motion were correctly mapped (RMSE=0.6/0.5mm). Kidney motion demonstrated good motion estimation with RMSE‐values of 0.95 and 2.4mm for the right and left kidney, respectively.

Conclusion:

We have demonstrated a method that can calculate dynamic 3D abdominal motion in a large volume, while acquiring real‐time cine‐MR images for MR‐guided radiotherapy.
WE‐G‐BRD‐02: Characterizing Information Loss in a Sparse‐Sampling‐Based Dynamic MRI Sequence (k‐T BLAST) for Lung Motion Monitoring
Authors: Arai T , Nofiele J , Sawant A
Published: June 2015

Purpose:

Rapid MRI is an attractive, non‐ionizing tool for soft‐tissue‐based monitoring of respiratory motion in thoracic and abdominal radiotherapy. One big challenge is to achieve high temporal resolution while maintaining adequate spatial resolution. K‐t BLAST, sparse‐sampling and reconstruction sequence based on a‐priori information represents a potential solution. In this work, we investigated how much “true” motion information is lost as a‐priori information is progressively added for faster imaging.

Methods:

Lung tumor motions in superior‐inferior direction obtained from ten individuals were replayed into an in‐house, MRI‐compatible, programmable motion platform (50Hz refresh and 100microns precision). Six water‐filled 1.5ml tubes were placed on it as fiducial markers. Dynamic marker motion within a coronal slice (FOV: 32×32cm2, resolution: 0.67×0.67mm2, slice‐thickness: 5mm) was collected on 3.0T body scanner (Ingenia, Philips). Balanced‐FFE (TE/TR: 1.3ms/2.5ms, flip‐angle: 40degrees) was used in conjunction with k‐t BLAST. Each motion was repeated four times as four k‐t acceleration factors 1, 2, 5, and 16 (corresponding frame rates were 2.5, 4.7, 9.8, and 19.1Hz, respectively) were compared. For each image set, one average motion trajectory was computed from six marker displacements. Root mean square error (RMS) was used as a metric of spatial accuracy where measured trajectories were compared to original data.

Results:

Tumor motion was approximately 10mm. The mean(standard deviation) of respiratory rates over ten patients was 0.28(0.06)Hz. Cumulative distributions of tumor motion frequency spectra (0–25Hz) obtained from the patients showed that 90% of motion fell on 3.88Hz or less. Therefore, the frame rate must be a double or higher for accurate monitoring. The RMS errors over patients for k‐t factors of 1, 2, 5, and 16 were.10(.04),.17(.04), .21(.06) and.26(.06)mm, respectively.

Conclusions:

K‐t factor of 5 or higher can cover the high frequency component of tumor respiratory motion, while the estimated error of spatial accuracy was approximately.2mm.
WE‐G‐BRD‐03: Real‐Time Tumor Motion Tracking in Low Field Cine‐MR Images
Authors: Wan H , Pless R , Parikh P
Published: June 2015

Purpose:

ViewRay's MRIdian system acquires cine‐MR images during treatment, allowing for real‐time visualization of the tumor without additional dose. We propose a novel method for tracking the tumor target on these cine‐MR images in real‐time.

Methods:

9 patients with mobile abdominal tumors (3 stomach, 1 pancreas, 1 adrenal, 2 mesenteric, 2 peritoneal) were imaged on ViewRay (0.3T, open‐bore; TrueFISP). Sagittal slice cine‐MR images (3.5×3.5mm pixels) were acquired at 4 frames per second. A 25‐second training period was used to collect 100 images during normal breathing. PCA was used to bin the images using the first 2 eigenvalues. Manual contouring of the target was performed on the first eigenimage. The mean eigenvalues in each bin were used to reconstruct 15 images, on which template matching was used to locate the target. A linear fit of the pixel locations was used to create the motion model. For each subsequently acquired image, the 2‐component PCA model was inverted and the values plugged into the motion model to get the corresponding pixel location. Finally, this location and the user‐drawn contour were used as the initialization for an active contouring algorithm to refine the edges of the tracked target. 100 images for each patient were manually contoured and used as the gold standard for comparison using the Dice similarity coefficient (DSC) and the modified Hausdorff distance (MHD).

Results:

The mean DSC is 0.87±0.09 and MHD is 2.6±0.9mm, which is less than the pixel size. The algorithm takes 100ms per image using Matlab, and is therefore more than fast enough for real‐time use.

Conclusion:

We have developed a robust method for real‐time tumor motion tracking in low‐resolution, low‐field cine‐MR images. We foresee our method being used for automated gating and dosimetric measurement purposes with the ViewRay system.
WE‐G‐BRD‐04: BEST IN PHYSICS (JOINT IMAGING‐THERAPY): An Integrated Model‐Based Intrafractional Organ Motion Tracking Approach with Dynamic MRI in Head and Neck Radiotherapy
Authors: Chen H , Dolly S , Victoria J , Anastasio M , Ruan S , Low D , Li H , Wooten H , Dempsey J , Gay H , Mutic S , Thorstad W , Li H
Published: June 2015

Purpose:

In‐treatment dynamic cine images, provided by the first commercially available MRI‐guided radiotherapy system, allow physicians to observe intrafractional motion of head and neck (H&N) internal structures. Nevertheless, high anatomical complexity and relatively poor cine image contrast/resolution have complicated automatic intrafractional motion evaluation. We proposed an integrated model‐based approach to automatically delineate and analyze moving structures from on‐board cine images.

Methods:

The H&N upper airway, a complex and highly deformable region wherein severe internal motion often occurs, was selected as the target‐to‐be‐tracked. To reliably capture its motion, a hierarchical structure model containing three statistical shapes (face, face‐jaw, and face‐jaw‐palate) was first built from a set of manually delineated shapes using principal component analysis. An integrated model‐fitting algorithm was then employed to align the statistical shapes to the first to‐be‐detected cine frame, and multi‐feature level‐set contour propagation was performed to identify the airway shape change in the remaining frames. Ninety sagittal cine MR image sets, acquired from three H&N cancer patients, were utilized to demonstrate this approach.

Results:

The tracking accuracy was validated by comparing the results to the average of two manual delineations in 20 randomly selected images from each patient. The resulting dice similarity coefficient (93.28+/−1.46 %) and margin error (0.49+/−0.12 mm) showed good agreement with the manual results. Intrafractional displacements of anterior, posterior, inferior, and superior airway boundaries were observed, with values of 2.62+/−2.92, 1.78+/−1.43, 3.51+/−3.99, and 0.68+/−0.89 mm, respectively. The H&N airway motion was found to vary across directions, fractions, and patients, and highly correlated with patients’ respiratory frequency.

Conclusion:

We proposed the integrated computational approach, which for the first time allows to automatically identify the H&N upper airway and quantify in‐treatment H&N internal motion in real‐time. This approach can be applied to track other structures’ motion, and provide guidance on patient‐specific prediction of intra‐/inter‐fractional structure displacements.
WE‐G‐BRD‐07: Automated MR Image Standardization and Auto‐Contouring Strategy for MRI‐Based Adaptive Brachytherapy for Cervix Cancer
Authors: Saleh H Al , Erickson B , Paulson E
Published: June 2015

Purpose:

MRI‐based adaptive brachytherapy (ABT) is an emerging treatment modality for patients with gynecological tumors. However, MR image intensity non‐uniformities (IINU) can vary from fraction to fraction, complicating image interpretation and auto‐contouring accuracy. We demonstrate here an automated MR image standardization and auto‐contouring strategy for MRI‐based ABT of cervix cancer.

Methods:

MR image standardization consisted of: 1) IINU correction using the MNI N3 algorithm, 2) noise filtering using anisotropic diffusion, and 3) signal intensity normalization using the volumetric median. This post‐processing chain was implemented as a series of custom Matlab and Java extensions in MIM (v6.4.5, MIM Software) and was applied to 3D T2 SPACE images of six patients undergoing MRI‐based ABT at 3T. Coefficients of variation (CV=σ/µ) were calculated for both original and standardized images and compared using Mann‐Whitney tests. Patient‐specific cumulative MR atlases of bladder, rectum, and sigmoid contours were constructed throughout ABT, using original and standardized MR images from all previous ABT fractions. Auto‐contouring was performed in MIM two ways: 1) best‐match of one atlas image to the daily MR image, 2) multi‐match of all previous fraction atlas images to the daily MR image. Dice's Similarity Coefficients (DSCs) were calculated for auto‐generated contours relative to reference contours for both original and standardized MR images and compared using Mann‐Whitney tests.

Results:

Significant improvements in CV were detected following MR image standardization (p=0.0043), demonstrating an improvement in MR image uniformity. DSCs consistently increased for auto‐contoured bladder, rectum, and sigmoid following MR image standardization, with the highest DSCs detected when the combination of MR image standardization and multi‐match cumulative atlas‐based auto‐contouring was utilized.

Conclusion:

MR image standardization significantly improves MR image uniformity. The combination of MR image standardization and multi‐match cumulative atlas‐based auto‐contouring produced the highest DSCs and is a promising strategy for MRI‐based ABT for cervix cancer.
WE‐G‐BRB‐00: NIH‐Funded Research: Instrumental in the Pursuit of Clinical Trials and Technological Innovations
Authors: Moran Jean
Published: June 2015

Over the past 20 years the NIH has funded individual grants, program projects grants, and clinical trials which have been instrumental in advancing patient care. The ways that each grant mechanism lends itself to the different phases of translating research into clinical practice will be described. Major technological innovations, such as IMRT and proton therapy, have been advanced with R01‐type and P01‐type funding and will be discussed. Similarly, the role of program project grants in identifying and addressing key hypotheses on the potential of 3D conformal therapy, normal tissue‐guided dose escalation and motion management will be described. An overview will be provided regarding how these technological innovations have been applied to multi‐institutional NIH‐sponsored trials. Finally, the panel will discuss regarding which research questions should be funded by the NIH to inspire the next advances in radiation therapy.

Learning Objectives:

Understand the different funding mechanisms of the NIH

Learn about research advances that have led to innovation in delivery

Review achievements due to NIH‐funded program project grants in radiotherapy over the past 20 years

Understand example advances achieved with multi‐institutional clinical trials

NIH
WE‐G‐BRB‐01: The Importance of NIH Funding in Innovation in Radiation Therapy
Authors: Deye J.
Published: June 2015

Over the past 20 years the NIH has funded individual grants, program projects grants, and clinical trials which have been instrumental in advancing patient care. The ways that each grant mechanism lends itself to the different phases of translating research into clinical practice will be described. Major technological innovations, such as IMRT and proton therapy, have been advanced with R01‐type and P01‐type funding and will be discussed. Similarly, the role of program project grants in identifying and addressing key hypotheses on the potential of 3D conformal therapy, normal tissue‐guided dose escalation and motion management will be described. An overview will be provided regarding how these technological innovations have been applied to multi‐institutional NIH‐sponsored trials. Finally, the panel will discuss regarding which research questions should be funded by the NIH to inspire the next advances in radiation therapy.

Learning Objectives:

Understand the different funding mechanisms of the NIH

Learn about research advances that have led to innovation in delivery

Review achievements due to NIH‐funded program project grants in radiotherapy over the past 20 years

Understand example advances achieved with multi‐institutional clinical trials

NIH
WE‐G‐BRB‐02: The Role of Program Project Grants in Study of 3D Conformal Therapy, Dose Escalation and Motion Management
Authors: Fraass B.
Published: June 2015

Over the past 20 years the NIH has funded individual grants, program projects grants, and clinical trials which have been instrumental in advancing patient care. The ways that each grant mechanism lends itself to the different phases of translating research into clinical practice will be described. Major technological innovations, such as IMRT and proton therapy, have been advanced with R01‐type and P01‐type funding and will be discussed. Similarly, the role of program project grants in identifying and addressing key hypotheses on the potential of 3D conformal therapy, normal tissue‐guided dose escalation and motion management will be described. An overview will be provided regarding how these technological innovations have been applied to multi‐institutional NIH‐sponsored trials. Finally, the panel will discuss regarding which research questions should be funded by the NIH to inspire the next advances in radiation therapy.

Learning Objectives:

Understand the different funding mechanisms of the NIH

Learn about research advances that have led to innovation in delivery

Review achievements due to NIH‐funded program project grants in radiotherapy over the past 20 years

Understand example advances achieved with multi‐institutional clinical trials

NIH
WE‐G‐303‐03: Advances in in Vivo Magnetic NanoparticleSensing
Authors: Weaver J.
Published: June 2015

Over the last decade, there has been a growing interest in applying nanotechnology to cancer detection, treatment, and treatment monitoring. Advances in nanotechnology have enabled the fabrication of nanoparticles from various materials with different shapes and sizes. Nanoparticles can be accumulated preferentially within tumors by either “passive targeting” through a phenomenon typically known as “enhanced permeability and retention” or “active targeting” in which nanoparticles are conjugated with antibodies or peptides directed against tumor and/or stromal markers. The tumor specificity of nanoparticles in conjunction with their unique physicochemical properties offers many novel strategies for cancer treatment and detection. For example, notable approaches in the radiation oncology setting include the use of gold nanoparticles for radiation response modulation of tumor or normal tissue and thermal ablation or hyperthermia treatment of tumors. Some of these approaches are currently being tested either on humans or on animals and, very likely, will become the clinical reality in the near future. Various computational and experimental techniques have also been applied to address unique research issues associated with nanoparticles and may become the standard tools for future investigations and clinical translations. Therefore, both clinicians and researchers may need to be properly educated about the basic principles as well as the promise of nanoparticle‐based applications with regard to the future of cancer diagnostics and therapeutics.

This symposium will familiarize the audience with the potential applications of nanoparticles in oncologic imaging and therapy using specific illustrative examples. The audience will be properly oriented by these illustrative examples to the multiple avenues for collaborative research amongst interdisciplinary teams of physicists, clinicians, engineers, chemists, and biologists in industry and academia.

Learning Objectives:

Understand the physical bases of gold nanoparticle applications for radiosensitization and x‐ray fluorescence imaging

Understand the parameters that define gold nanoparticle‐mediated radiosensitization in biological systems

Understand the potential of magnetic nanoparticle characterization of the microenvironment

Understand the various strategies for radiolabeling of nanoparticles and their applications

S.C. and S.K. acknowledge support from MD Anderson Cancer Center, NIH (R01CA155446 and P30CA16672) and DoD (W81XWH‐12‐1‐0198); J.W. acknowledges support from NIH (U54CA151662‐01); W.C. acknowledges support from the University of Wisconsin‐Madison, NIH (R01CA169365, P30CA014520, and T32CA009206), DoD (W81XWH‐11‐1‐0644 and W81XWH‐11‐1‐0648), and ACS (125246‐RSG‐13‐099‐01‐CCE).
WE‐G‐204‐01: BEST IN PHYSICS (IMAGING): Effect of Image Processing Parameters On Nodule Detectability in Chest Radiography
Authors: Little K , Lu Z , MacMahon H , Reiser I
Published: June 2015

Purpose:

To investigate the effect of varying system image processing parameters on lung nodule detectability in digital radiography.

Methods:

An anthropomorphic chest phantom was imaged in the posterior‐anterior position using a GE Discovery XR656 digital radiography system. To simulate lung nodules, a polystyrene board with 6.35mm diameter PMMA spheres was placed adjacent to the phantom (into the x‐ray path). Due to magnification, the projected simulated nodules had a diameter in the radiographs of approximately 7.5 mm. The images were processed using one of GE's default chest settings (Factory3) and reprocessed by varying the “Edge” and “Tissue Contrast” processing parameters, which were the two user‐configurable parameters for a single edge and contrast enhancement algorithm. For each parameter setting, the nodule signals were calculated by subtracting the chest‐only image from the image with simulated nodules. Twenty nodule signals were averaged, Gaussian filtered, and radially averaged in order to generate an approximately noiseless signal. For each processing parameter setting, this noise‐free signal and 180 background samples from across the lung were used to estimate ideal observer performance in a signal‐known‐exactly detection task. Performance was estimated using a channelized Hotelling observer with 10 Laguerre‐Gauss channel functions.

Results:

The “Edge” and “Tissue Contrast” parameters each had an effect on the detectability as calculated by the model observer. The CHO‐estimated signal detectability ranged from 2.36 to 2.93 and was highest for “Edge” = 4 and “Tissue Contrast” = −0.15. In general, detectability tended to decrease as “Edge” was increased and as “Tissue Contrast” was increased. A human observer study should be performed to validate the relation to human detection performance.

Conclusion:

Image processing parameters can affect lung nodule detection performance in radiography. While validation with a human observer study is needed, model observer detectability for common tasks could provide a means for optimizing image processing parameters.
WE‐G‐204‐04: Focal Spot Deblurring For High Resolution Amorphous Selenium (aSe) Complementary Metal Oxide Semiconductor (CMOS) X‐Ray Detector
Authors: Nagesh S Setlur , Rana R , Russ M , Ionita C , Bednarek D , Rudin S
Published: June 2015

Purpose:

CMOS‐based aSe detectors compared to CsI‐TFT‐based flat panels have the advantages of higher spatial sampling due to smaller pixel size and decreased blurring characteristic of direct rather than indirect detection. For systems with such detectors, the limiting factor degrading image resolution then becomes the focal‐spot geometric unsharpness. This effect can seriously limit the use of such detectors in areas such as cone beam computed tomography, clinical fluoroscopy and angiography. In this work a technique to remove the effect of focal‐spot blur is presented for a simulated aSe detector.

Method:

To simulate images from an aSe detector affected with focal‐spot blur, first a set of high‐resolution images of a stent (FRED from Microvention, Inc.) were acquired using a 75µm pixel size Dexela‐Perkin‐Elmer detector and averaged to reduce quantum noise. Then the averaged image was blurred with a known Gaussian blur at two different magnifications to simulate an idealized focal spot. The blurred images were then deconvolved with a set of different Gaussian blurs to remove the effect of focal‐spot blurring using a threshold‐based, inverse‐filtering method.

Results:

The blur was removed by deconvolving the images using a set of Gaussian functions for both magnifications. Selecting the correct function resulted in an image close to the original; however, selection of too wide a function would cause severe artifacts.

Conclusion:

Experimentally, focal‐spot blur at different magnifications can be measured using a pin hole with a high resolution detector. This spread function can be used to deblur the input images that are acquired at corresponding magnifications to correct for the focal spot blur. For CBCT applications, the magnification of specific objects can be obtained using initial reconstructions then corrected for focal‐spot blurring to improve resolution. Similarly, if object magnification can be determined such correction may be applied in fluoroscopy and angiography.
WE‐G‐204‐05: Relative Object Detectability Evaluation of a New High Resolution A‐Se Direct Detection System Compared to Indirect Micro‐Angiographic Fluoroscopic (MAF) Detectors
Authors: Russ M , Nagesh S Setlur , Ionita C , Scott C , Karim K , Bednarek D , Rudin S
Published: June 2015

Purpose:

To evaluate the task specific imaging performance of a new 25µm pixel pitch, 1000µm thick amorphous selenium direct detection system with CMOS readout for typical angiographic exposure parameters using the relative object detectability (ROD) metric.

Methods:

The ROD metric uses a simulated object function weighted at each spatial frequency by the detectors’ detective quantum efficiency (DQE), which is an intrinsic performance metric. For this study, the simulated objects were aluminum spheres of varying diameter (0.05–0.6mm). The weighted object function is then integrated over the full range of detectable frequencies inherent to each detector, and a ratio is taken of the resulting value for two detectors. The DQE for the 25µm detector was obtained from a simulation of a proposed a‐Se detector using an exposure of 200µR for a 50keV x‐ray beam. This a‐Se detector was compared to two microangiographic fluoroscope (MAF) detectors [the MAF‐CCD with pixel size of 35µm and Nyquist frequency of 14.2 cycles/mm and the MAF‐CMOS with pixel size of 75µm and Nyquist frequency of 6.6 cycles/mm] and a standard flat‐panel detector (FPD with pixel size of 194µm and Nyquist frequency of 2.5cycles/mm).

Results:

ROD calculations indicated vastly superior performance by the a‐Se detector in imaging small aluminum spheres. For the 50µm diameter sphere, the ROD values for the a‐Se detector compared to the MAF‐CCD, the MAF‐CMOS, and the FPD were 7.3, 9.3 and 58, respectively. Detector performance in the low frequency regime was dictated by each detector's DQE(0) value.

Conclusion:

The a‐Se with CMOS readout is unique and appears to have distinctive advantages of incomparable high resolution, low noise, no readout lag, and expandable design. The a‐Se direct detection system will be a powerful imaging tool in angiography, with potential break‐through applications in diagnosis and treatment of neuro‐vascular disease.

Supported by NIH Grant: 2R01EB002873 and an equipment grant from Toshiba Medical Systems Corporation
WE‐G‐204‐06: Grid‐Line Artifact Minimization for High Resolution Detectors Using Iterative Residual Scatter Correction
Authors: Rana R , Bednarek D , Rudin S
Published: June 2015

Purpose:

Anti‐scatter grid‐line artifacts are more prominent for high‐resolution x‐ray detectors since the fraction of a pixel blocked by the grid septa is large. Direct logarithmic subtraction of the artifact pattern is limited by residual scattered radiation and we investigate an iterative method for scatter correction.

Methods:

A stationary Smit‐Rοntgen anti‐scatter grid was used with a high resolution Dexela 1207 CMOS X‐ray detector (75 µm pixel size) to image an artery block (Nuclear Associates, Model 76‐705) placed within a uniform head equivalent phantom as the scattering source. The image of the phantom was divided by a flat‐field image obtained without scatter but with the grid to eliminate grid‐line artifacts. Constant scatter values were subtracted from the phantom image before dividing by the averaged flat‐field‐with‐grid image. The standard deviation of pixel values for a fixed region of the resultant images with different subtracted scatter values provided a measure of the remaining grid‐line artifacts.

Results:

A plot of the standard deviation of image pixel values versus the subtracted scatter value shows that the image structure noise reaches a minimum before going up again as the scatter value is increased. This minimum corresponds to a minimization of the grid‐line artifacts as demonstrated in line profile plots obtained through each of the images perpendicular to the grid lines. Artifact‐free images of the artery block were obtained with the optimal scatter value obtained by this iterative approach.

Conclusion:

Residual scatter subtraction can provide improved grid‐line artifact elimination when using the flat‐field with grid “subtraction” technique. The standard deviation of image pixel values can be used to determine the optimal scatter value to subtract to obtain a minimization of grid line artifacts with high resolution x‐ray imaging detectors.

This study was supported by NIH Grant R01EB002873 and an equipment grant from Toshiba Medical Systems Corp.