bluuebunny/crossref_metadata_2025 huggingface dataset:
TU‐A‐9A‐04: Development of a Thermally Stable Phantom for Photoacoustic and Magnetic Resonance Temperature Imaging
Authors: Dextraze K , MacLellan C , Mitcham T , Melancon M , Bouchard R
Published: July 2014

Purpose:

Photoacoustic‐ultrasonic (PAUS) imaging, which utilizes an ultrasound transducer to provide co‐registered photoacoustic and pulse‐echo ultrasound images, is capable of measuring temperature non‐invasively while simultaneously providing anatomical images. The sub‐millimeter resolution and centimeter‐order penetration depths achievable with PAUS imaging have the potential to deliver active monitoring of both a targeted tumor microenvironment and nearby healthy tissue during thermal ablation. These characteristics make PAUS imaging a promising new technique for guidance and monitoring during photothermal ablations of solid tumors. In order to assess the potential clinical role of PAUS imaging, the technique was validated against the clinically accepted magnetic resonance thermal imaging approach (MRTI).

Methods:

To facilitate co‐registration between modalities, the phantom had inclusions of gold nanoshells encapsulating super‐paramagnetic iron oxide (SPIO) particles, where gold enhances the PA signal and SPIOs provide negative contrast on MRI. Several phantom designs were assessed for resilience to heating. PA images were acquired on a Vevo LAZR (FUJIFILM VisualSonics Inc., Toronto, Ontario) PAultrasound small‐animal imaging system (21MHz) operating at 710nm. MRTI experiments were performed using a 6‐channel flex coil (GE Healthcare, Waukesha, WI) on a 3T MRI scanner (Discovery MR750, GE Healthcare, Waukesha, WI) using a fast multi gradient echo acquisition (16 echoes, 128×128 acquisition matrix, 25.6×25.6cm field of view, 3mm slice thickness, 60ms TR, 20° flip angle, 2.9ms minimum TE and 1.6ms echo spacing). The accuracy and spatio‐temporal resolution of PA thermography was cross‐validated with both MRTI and a fluoroptic temperature sensor (LumaSense Technologies, Santa Clara, CA) in the custom‐designed phantom.

Results:

A thermally stable, dual‐modality phantom was created for cross‐validation of photoacoustic thermography and MRTI. Axial and lateral resolutions of PA images were sub‐millimeter with a temporal resolution of 0.2s, which will accommodate precise real‐time guidance and monitoring.

Conclusion:

These results indicate that a PA thermography technique offers tremendous promise for real‐time thermal monitoring of ablative therapy.

Funding support provided by Cancer Prevention Research Institute of Texas and Julia Jones Matthews family. No disclosures or conflicts of interest.
TU‐A‐12A‐12: Improved Airway Measurement Accuracy for Low Dose Quantitative CT (qCT) Using Statistical (ASIR), at Reduced DFOV, and High Resolution Kernels in a Phantom and Swine Model
Authors: Yadava G , Imai Y , Hsieh J
Published: July 2014

Purpose:

Quantitative accuracy of Iodine Hounsfield Unit (HU) in conventional single‐kVp scanning is susceptible to beam‐hardening effect. Dual‐energy CT has unique capabilities of quantification using monochromatic CT images, but this scanning mode requires the availability of the state‐of‐the‐art CT scanner and, therefore, is limited in routine clinical practice. Purpose of this work was to develop a beam‐hardening‐correction (BHC) for single‐kVp CT that can linearize Iodine projections at any nominal energy, apply this approach to study Iodine response with respect to keV, and compare with dual‐energy based monochromatic images obtained from material‐decomposition using 80kVp and 140kVp.

Methods:

Tissue characterization phantoms (Gammex Inc.), containing solid‐Iodine inserts of different concentrations, were scanned using GE multi‐slice CT scanner at 80, 100, 120, and 140 kVp. A model‐based BHC algorithm was developed where Iodine was estimated using re‐projection of image volume and corrected through an iterative process. In the correction, the re‐projected Iodine was linearized using a polynomial mapping between monochromatic path‐lengths at various nominal energies (40 to 140 keV) and physically modeled polychromatic path‐lengths. The beam‐hardening‐corrected 80kVp and 140kVp images (linearized approximately at effective energy of the beam) were used for dual‐energy material‐decomposition in Water‐Iodine basis‐pair followed by generation of monochromatic images. Characterization of Iodine HU and noise in the images obtained from singlekVp with BHC at various nominal keV, and corresponding dual‐energy monochromatic images, was carried out.

Results:

Iodine HU vs. keV response from single‐kVp with BHC and dual‐energy monochromatic images were found to be very similar, indicating that single‐kVp data may be used to create material specific monochromatic equivalent using modelbased projection linearization.

Conclusion:

This approach may enable quantification of Iodine contrast enhancement and potential reduction in injected contrast without using dual‐energy scanning. However, in general, dual‐energy scanning has unique value in material characterization and quantification, and its value cannot be discounted.

GE Healthcare Employee
TU‐C‐12A‐06: Computerized Analysis of Diffusion‐Weighted Images in Breast Cancer Diagnosis
Authors: White T , Weiss W , Giger M
Published: July 2014

Purpose:

Diffusion‐weighted imaging (DWI) for breast MRI is a non‐invasive technique which maps the diffusion process of water molecules, with the use of Brownian motion, in biological tissues, yielding apparent diffusion coefficients (ADC). Quantitative image analyses of the resulting images can yield information about the surrounding tissues in vivo. In this study, we investigated computerized image analyses of DWI images, including automated lesion segmentation, calculation of ADC values, and assessment of tumor heterogeneity, on a dataset of malignant and benign breast lesions.

Method and Database:

The IRB‐approved, retrospectively collected dataset included 46 breast lesions ‐‐ 36 malignant and 10 benign. The DW images had been acquired during clinical breast MRI on a high‐field 1.5 T echo‐planar system using five b values [b = 0, 500, 1000, 1500, and 2000 s/mm2]. Seed‐point‐initiated 3D Gaussian‐based lesion segmentation was conducted to yield the lesion margins, and within the margin and after b‐value fitting, ADC values were calculated. Average ADC values and various measures of heterogeneity were calculated for benign and malignant lesions.

Results:

Our findings showed that malignant lesions tended, as expected, to have lower ADC values relative to benign lesions with average ADC values for benign and malignant lesions being 1.70 +/− 0.50 × 10(−3) and 1.07 +/− 0.37 × 10(−3), respectively. In addition, malignant lesions showed higher heterogeneity. In the task of distinguishing between benign and malignant lesions, ROC analysis, from histogram analysis, yielded AUC values of 0.86 +/− 0.07 and 0.88 +/− 0.06 for average ADC values and standard deviation of ADC values, respectively.

Conclusion:

DWI exhibits potential for differentiating between benign and malignant lesions, and inclusion of computerized quantitative image analysis methods allow for more objectives and efficient calculations of the ADC values and their variations, for potential use in decision making.

M. L. Giger is a stockholder in R2 Technology/Hologic, is a shareholder/investor in Quantitative Insights, Qview Medical,receives royalties from Hologic, GE Medical Systems, MEDIAN Technologies, Riverain Medical, Mitsubishi and Toshiba.
TU‐C‐12A‐10: BEST IN PHYSICS (IMAGING) – Correlating 4DCT‐Ventilation with Clinical Pulmonary Function Test Data
Authors: Vinogradskiy Y , Castillo R , Castillo E , Guerrero T , Miften M , Kavanagh B , Martel M , Schubert L
Published: July 2014

Purpose:

4DCT‐ventilation is an emerging form of lung function imaging calculated from 4DCT data. Because 4DCTs are acquired as part of routine care, the lung function information comes at no extra monetary or dosimetric cost to the patient. Studies are needed that compare 4DCT‐ventilation with clinical data. Pulmonary function tests (PFT) provide an established method of evaluating lung function. Our study performed a clinical validation by comparing 4DCT‐ventilation with PFT data.

Methods:

63 patients with pre‐treatment PFTs and 4DCT data were used for the study. Standard PFT metrics used to diagnose tumor‐based obstructive lung disease were recorded for each patient, including forced expiratory volume in 1 second (FEV1), and the ratio between FEV1 and the forced vital capacity (FEV1/FVC). A PFT value of 70% was used to delineate normal versus abnormal lung function for modeling. 4DCT data sets were input into a density‐change based model to compute 4DCT‐ventilation. The 4DCT‐ventilation maps were reduced to single metrics intended to reflect the degree of ventilation obstruction and heterogeneity. The coefficient of variation (CoV) defined as the ratio of standard deviation over mean ventilation and the ventilation‐V20 (volume of lung <20% ventilation) were computed. Ventilation metrics were compared to PFT data using correlation coefficients and logistic regression modeling methods.

Results:

The 4DCT‐ventilation metrics correlated well with PFT data. Ventilation‐V20 had correlation values of 0.75 and 0.71 with FEV1 and FEV1/FVC respectively. A probit model as a function of the ventilationderived CoV was fit and able to significantly (p<0.01) predict for normal versus abnormal PFT‐based lung function.

Conclusions:

The current study validates 4DCT‐ventilation with a clinically established end‐point. Our data demonstrate good agreement between PFTs and ventilation data, indicating that 4DCT‐ventilation can reliably demonstrate oncologic‐based obstructive lung disease. We present important results that support integration of 4DCT‐based pre‐treatment lung function assessment into clinical practice.

This work was partially supported by the NIH Director's new Innovator award (TG, EC, RC) and NIH research scientist development award (RC)
TU‐F‐16A‐01: Communicating Risk
Authors: McCollough C , Wagner L , Kofler J , Brateman L
Published: July 2014

The radiobiological risks associated with medical imaging are generally considered to be small, if existent. However, the public view of the risk of medical radiation at diagnostic levels can be substantially different from the clinical reality. Radiation science is not taught to the general public, and so perception of radiation risks can be based on a variety sources, including some that may be misleading, incorrect, or sensationalized. Consequently, patients can have significant concerns about procedures they or their loved ones might have had or that might be needed in their medical care. It is the responsibility of the physicist to be able to communicate risk in a manner that is clear, understandable, and respectful. This session will present a number of real life scenarios of patient or family concern about radiation risks. The panel will, through demonstration or discussion, present various options for handling each situation. The audience will be involved in discussion and critique of the approaches presented.

Learning Objectives:

To gain insight to the patients perspective on radiation risk and how to respond professionally to their concerns.

To learn basic principles for effectively communicating with patients about radiation risk.

To gain tools and approaches for addressing a wide range of patient concerns.
TU‐F‐19A‐01: New Member Symposium
Authors: Sherouse G , Miller R
Published: July 2014

As a new member of the AAPM, it’s easy to feel overwhelmed by the size and complexity of the association and to be unaware of the benefits and opportunities available to members. At this year’s AAPM annual meeting in Austin, we will host a New Member Symposium where you can learn more about the organization, member resources, and opportunities to get involved.

Learning Objectives:

Welcome, introduction to, and overview of AAPM organization

Introduction to medical physics profession

Registered attendees will receive a raffle ticket for a drawing at the symposium to win a complimentary registration for the 2015 Annual Meeting in Anaheim!

In addition, all new members who register for the Symposium will receive a drink ticket, good for one complimentary soda or beer served during the social following.
TU‐F‐BRE‐05: Experimental Determination of K Factor in Small Field Dosimetry
Authors: Das I , Akino Y , Francescon P
Published: July 2014

Purpose:

Small‐field dosimetry is challenging due to charged‐particle disequilibrium, source occlusion and more importantly finite size of detectors. IAEA/AAPM has published approach to convert detector readings to dose by k factor. Manufacturers have been trying to provide various types of micro‐detectors that could be used in small fields. However k factors depends on detector perturbations and are derived using Monte Carlo simulation. PTW has introduced a microDiamond for small‐field dosimetry. An experimental approach is presented to derive the k factor for this detector.

Methods:

PTW microDiamond is a small volume detector with 1.1 mm radius and 1.0 micron thick synthetic diamond. Output factors were measured from 1×1cm2 to 12×12 cm2 on a Varian machine at various depths using various micro‐detectors with published k factors. Dose is calculated as reading * K. Assuming k factor is accurate, output factor should be identical with every micro‐detectors. Hence published k values (Francescon et al Med Phys 35, 504‐513,2008) were used to covert readings and then output factors were computed. Based on the converged curve from other detectors, k factor for microDiamond was computed versus field size.

Results:

Traditional output factors as ratio of readings normalized to 10×10 cm2 differ significantly for micro‐detectors for fields smaller than 3×3 cm2 which are now being used extensively. When readings are converted to dose, the output factor is independent of detector. Based on this method, k factor for microDiamond was estimated to be nearly constant 0.993±0.007 over varied field sizes.

Conclusion:

Our method provides a unique opportunity to determine the k factor for any unknown detector. It is shown that even though k factor depends on machine type due to focal spot, however for fields ≥1×1 cm2 this method provides accurate evaluation of k factor. Additionally microDiamond could be used with assumption that k factor is nearly unity.
TU‐F‐BRD‐01: Biomedical Informatics for Medical Physicists
Authors: Phillips M , Kalet I , McNutt T , Smith W
Published: July 2014

Biomedical informatics encompasses a very large domain of knowledge and applications. This broad and loosely defined field can make it difficult to navigate. Physicists often are called upon to provide informatics services and/or to take part in projects involving principles of the field. The purpose of the presentations in this symposium is to help medical physicists gain some knowledge about the breadth of the field and how, in the current clinical and research environment, they can participate and contribute.

Three talks have been designed to give an overview from the perspective of physicists and to provide a more in‐depth discussion in two areas. One of the primary purposes, and the main subject of the first talk, is to help physicists achieve a perspective about the range of the topics and concepts that fall under the heading of “informatics”. The approach is to de‐mystify topics and jargon and to help physicists find resources in the field should they need them.

The other talks explore two areas of biomedical informatics in more depth. The goal is to highlight two domains of intense current interest‐‐databases and models‐‐in enough depth into current approaches so that an adequate background for independent inquiry is achieved. These two areas will serve as good examples of how physicists, using informatics principles, can contribute to oncology practice and research.

Learning Objectives:

To understand how the principles of biomedical informatics are used by medical physicists.

To put the relevant informatics concepts in perspective with regard to biomedicine in general.

To use clinical database design as an example of biomedical informatics.

To provide a solid background into the problems and issues of the design and use of data and databases in radiation oncology.

To use modeling in the service of decision support systems as an example of modeling methods and data use.

To provide a background into how uncertainty in our data and knowledge can be incorporated into modeling methods.
TU‐F‐BRF‐02: MR‐US Prostate Registration Using Patient‐Specific Tissue Elasticity Property Prior for MR‐Targeted, TRUS‐Guided HDR Brachytherapy
Authors: Yang X , Rossi P , Ogunleye T , Jani A , Curran W , Liu T
Published: July 2014

Purpose:

High‐dose‐rate (HDR) brachytherapy has become a popular treatment modality for prostate cancer. Conventional transrectal ultrasound (TRUS)‐guided prostate HDR brachytherapy could benefit significantly from MR‐targeted, TRUS‐guided procedure where the tumor locations, acquired from the multiparametric MRI, are incorporated into the treatment planning. In order to enable this integration, we have developed a MR‐TRUS registration with a patient‐specific biomechanical elasticity prior.

Methods:

The proposed method used a biomechanical elasticity prior to guide the prostate volumetric B‐spline deformation in the MRI and TRUS registration. The patient‐specific biomechanical elasticity prior was generated using ultrasound elastography, where two 3D TRUS prostate images were acquired under different probe‐induced pressures during the HDR procedure, which takes 2‐4 minutes. These two 3D TRUS images were used to calculate the local displacement (elasticity map) of two prostate volumes. The B‐spline transformation was calculated by minimizing the Euclidean distance between the normalized attribute vectors of the prostate surface landmarks on the MR and TRUS. This technique was evaluated through two studies: a prostate‐phantom study and a pilot study with 5 patients undergoing prostate HDR treatment. The accuracy of our approach was assessed through the locations of several landmarks in the post‐registration and TRUS images; our registration results were compared with the surface‐based method.

Results:

For the phantom study, the mean landmark displacement of the proposed method was 1.29±0.11 mm. For the 5 patients, the mean landmark displacement of the surface‐based method was 3.25±0.51 mm; our method, 1.71±0.25 mm. Therefore, our proposed method of prostate registration outperformed the surfaced‐based registration significantly.

Conclusion:

We have developed a novel MR‐TRUS prostate registration approach based on patient‐specific biomechanical elasticity prior. Successful integration of multi‐parametric MR and TRUS prostate images provides a prostate‐cancer map for treatment planning, enables accurate dose planning and delivery, and potentially enhances prostate HDR treatment outcome.
TU‐F‐17A‐03: An Analytical Respiratory Perturbation Model for Lung Motion Prediction
Authors: Li G , Yuan A , Wei J
Published: July 2014

Purpose:

Breathing irregularity is common, causing unreliable prediction in tumor motion for correlation‐based surrogates. Both tidal volume (TV) and breathing pattern (BP=ΔVthorax/TV, where TV=ΔVthorax+ΔVabdomen) affect lung motion in anterior‐posterior and superior‐inferior directions. We developed a novel respiratory motion perturbation (RMP) model in analytical form to account for changes in TV and BP in motion prediction from simulation to treatment.

Methods:

The RMP model is an analytical function of patient‐specific anatomic and physiologic parameters. It contains a base‐motion trajectory d(x,y,z) derived from a 4‐dimensional computed tomography (4DCT) at simulation and a perturbation term Δd(ΔTV,ΔBP) accounting for deviation at treatment from simulation. The perturbation is dependent on tumor‐specific location and patient‐specific anatomy. Eleven patients with simulation and treatment 4DCT images were used to assess the RMP method in motion prediction from 4DCT1 to 4DCT2, and vice versa. For each patient, ten motion trajectories of corresponding points in the lower lobes were measured in both 4DCTs: one served as the base‐motion trajectory and the other as the ground truth for comparison. In total, 220 motion trajectory predictions were assessed. The motion discrepancy between two 4DCTs for each patient served as a control. An established 5D motion model was used for comparison.

Results:

The average absolute error of RMP model prediction in superior‐inferior direction is 1.6±1.8 mm, similar to 1.7±1.6 mm from the 5D model (p=0.98). Some uncertainty is associated with limited spatial resolution (2.5mm slice thickness) and temporal resolution (10‐phases). Non‐corrected motion discrepancy between two 4DCTs is 2.6±2.7mm, with the maximum of ±20mm, and correction is necessary (p=0.01).

Conclusion:

The analytical motion model predicts lung motion with accuracy similar to the 5D model. The analytical model is based on physical relationships, requires no training, and therefore is potentially more resilient to breathing irregularities. On‐going investigation introduces airflow into the RMP model for improvement.

This research is in part supported by NIH (U54CA137788/132378). AY would like to thank MSKCC summer medical student research program supported by National Cancer Institute and hosted by Department of Medical Physics at MSKCC.
WE‐D‐BRD‐01: Innovation in Radiation Therapy Delivery: Advanced Digital Linac Features
Authors: Xing L , Wong J , Li R
Published: July 2014

Last few years has witnessed significant advances in linac technology and therapeutic dose delivery method. Digital linacs equipped with high dose rate FFF beams have been clinically implemented in a number of hospitals. Gated VMAT is becoming increasingly popular in treating tumors affected by respiratory motion. This session is devoted to update the audience with these technical advances and to present our experience in clinically implementing the new linacs and dose delivery methods. Topics to be covered include, technical features of new generation of linacs from different vendors, dosimetric characteristics and clinical need for FFF‐beam based IMRT and VMAT, respiration‐gated VMAT, the concept and implementation of station parameter optimized radiation therapy (SPORT), beam level imaging and onboard image guidance tools. Emphasis will be on providing fundamental understanding of the new treatment delivery and image guidance strategies, control systems, and the associated dosimetric characteristics. Commissioning and acceptance experience on these new treatment delivery technologies will be reported. Clinical experience and challenges encountered during the process of implementation of the new treatment techniques and future applications of the systems will also be highlighted.

Learning Objectives:

Present background knowledge of emerging digital linacs and summarize their key geometric and dosimetric features.

SPORT as an emerging radiation therapy modality specifically designed to take advantage of digital linacs.

Discuss issues related to the acceptance and commissioning of the digital linacs and FFF beams.

Describe clinical utility of the new generation of digital linacs and their future applications.
WE‐D‐BRF‐02: Acoustic Signal From the Bragg Peak for Range Verification in Proton Therapy
Authors: Reinhardt S , Assmann W , Kellnberger S , Omar M , Fink A , Gaebisch C , Thirolf P , Moser M , Dollinger G , Sergiadis G , Ntziachristos V , Parodi K
Published: July 2014

Purpose:

Range verification in ion beam therapy relies to date on nuclear imaging techniques which require complex and costly detector systems. A different approach is the detection of thermoacoustic signals that are generated due to localized energy loss of ion beams. Aim of this work is to study the feasibility of determining the ion range with sub‐mm accuracy by use of high frequency ultrasonic (US) transducers and to image the Bragg peak by tomography.

Methods:

A water phantom was irradiated by a pulsed 20 MeV proton beam with varying pulse intensity, length and repetition rate. The acoustic signal of single proton pulses was measured by different PZT‐based US detectors (3.5 MHz and 10 MHz central frequencies). For tomography a 64 channel US detector array was used and moved along the ion track by a remotely controlled motor stage.

Results:

A clear signal of the Bragg peak was visible for an energy deposition as low as 1012 eV. The signal amplitude showed a linear increase with particle number per pulse and thus, dose. Range measurements were reproducible within +/− 20 micrometer and agreed well with Geant4 simulations. The tomographic reconstruction does not only allow to measure the ion range but also the beam spot size at the Bragg peak position.

Conclusion:

Range verification by acoustic means is a promising new technique for treatment modalities where the tumor can be localized by US imaging. Further improvement of sensitivity is required to account for higher attenuation of the US signal in tissue, as well as lower energy density in the Bragg peak in realistic treatment cases due to higher particle energy and larger spot sizes. Nevertheless, the acoustic range verification approach could offer the possibility of combining anatomical US imaging with Bragg Peak imaging in the near future.

The work was funded by the DFG cluster of excellence Munich Centre for Advanced Photonics (MAP).
WE‐D‐BRF‐03: Proton Beam Range Verification with a Single Prompt Gamma‐Ray Detector
Authors: Verburg J , Testa M , Cascio E , Bortfeld T , Lu H , Seco J
Published: July 2014

Purpose:

To present an experimental study of a novel range verification method for scanned and scattered proton beams.

Methods:

A detection system consisting of an actively shielded lanthanum(III)bromide scintillator and a one‐sided lead collimator was used to measure prompt gamma‐rays emitted during the delivery of proton beams to a water phantom and an anthropomorphic head phantom. The residual proton range at the collimator position was determined by comparing gamma‐ray intensities while the proton energy was modulated to the distal end of the target. We used a clinical field to deliver a 50 cGy dose to a 12 cm diameter target in the water phantom and to a 175 cc tumor‐shaped target in the head phantom. The detector signals were acquired with a custom data acquisition system enabling energy and time‐of‐flight discrimination of prompt gamma‐rays.

Results:

Range deviations were detected with a statistical accuracy of ± 0.2 mm and ± 1.4 mm at 90% confidence level, respectively for the water and head phantom. We obtained a time resolution of 1 ns FWHM and an energy resolution < 2% FWHM for the main gamma lines from proton‐induced nuclear reactions with carbon and oxygen. This allowed for an accurate separation of the prompt gamma‐rays from neutron‐induced background.

Conclusion:

Proton range deviations can be detected with millimeter accuracy using a single prompt gamma‐ray measurement point acquired during the delivery of a few proton energy layers to the distal part of the target. The method is also feasible in the presence of background radiation from passively scattered proton beam delivery.
WE‐D‐BRF‐04: Experimental Investigations On Ion Radiography with Beam Scanning Using a Range Telescope
Authors: Rinaldi I , Marcelos T , Magallanes L , Takechi M , Brons S , Jaekel O , Voss B , Parodi K
Published: July 2014

Purpose:

Ion beams exhibit a finite range and an inverted depth‐dose profile, the Bragg peak. These favorable properties allow superior tumordose conformality, but introduce sensitivity to range uncertainties. Hence, imaging techniques play an increasingly important role to support the treatment planning and the in‐vivo monitoring of the actual ion beam treatment.

Methods:

This work presents the experimental investigations carried out to address the feasibility of ion transmission imaging at the Heidelberg Ion Therapy center using an active raster scanning beam delivery system and a prototype range telescope set‐up based on a stack of 61 parallel‐plate ionization chambers (PPIC) interleaved with 3 mm absorber plates of PMMA.

Results:

An extensive characterization of the set‐up in terms of beam parameters and settings of the read‐out electronics was performed and results will be presented. A data processing method to increase the range resolution (MIRR) of the PPIC stack was developed. In this approach, the position of the maximum of the Bragg curve is deduced from the ratio of measured signals in adjacent PPIC channels. MIRR evaluation is based on Bragg curves obtained from Monte Carlo simulations and validated with experimental data acquired with the PPIC stack using ion beams. MIRR was applied to the carbon ion radiography of an anthropomorphic Alderson head phantom yielding a resolution of 0.8 mm water equivalent thickness (WET) compared to the nominal value of 3.495 mm WET given by the thickness of the absorber slabs in the PPIC stack. An absolute comparison of the Alderson phantom carbon ion transmitted image with an X‐ray digitally reconstructed radiography, both converted into WET, will also be shown.

Conclusion:

The obtained results are very promising and motivate further developments of the system towards an eventual clinical use. This work is supported by the German Research Foundation and the German Academic Exchange Service.

This work is supported by the German Research Foundation (DFG) and the German Academic Exchange Service (DAAD).
WE‐D‐17A‐01: A Dynamic Collimation System for Spot Scanned Proton Therapy: Conceptual Overview
Authors: Hyer D , Hill P , Wang D , Smith B , Flynn R
Published: July 2014

Purpose:

In the absence of a collimation system, the lateral penumbra in pencil beam scanning (PBS) proton therapy delivered at low energies is highly dependent on the spot size. This dependence, coupled with the fact that spot sizes increase with decreasing energy, reduces the benefit of the PBS technique for treating shallow tumors such as those found in the head and neck region. In order to overcome this limitation, a dynamic collimation system (DCS) was developed for sharpening the lateral penumbra of low energy proton therapy dose distributions delivered by PBS.

Methods:

The proposed DCS consists of two pairs of orthogonal trimmer blades which intercept the edges of the proton beam near the target edge in the beam's eye view. Each trimmer blade is capable of rapid motion in the direction perpendicular to the central beam axis by means of a linear motor, with maximum velocity and acceleration of 2.5 m/s and 19.6 m/s2, respectively. Two‐dimensional treatment plans were created both with and without the DCS for in‐air spot sizes (σ_air) of 3, 5, 7, and 9 mm, representing a wide array of clinically available equipment.

Results:

In its current configuration, the snout of the DCS has outer dimensions of 22.6 × 22.6 cm2 and is capable of delivering a minimum treatment field size of 15 × 15 cm2. Using off the shelf components, the constructed system would weigh less than 20 kg. The treatment plans created with the DCS yielded a reduction in the mean dose to normal tissue surrounding the target of 26.2–40.6% for spot sizes of 3–9 mm, respectively.

Conclusion:

The DCS can be integrated with current or future proton therapy equipment and we believe it will serve as a useful tool to further improve the next generation of proton therapy delivery.
WE‐D‐17A‐03: Improvement of Accuracy of Spot‐Scanning Proton Beam Delivery for Liver Tumor by Real‐Time Tumor‐Monitoring and Gating System: A Simulation Study
Authors: Matsuura T , Shimizu S , Miyamoto N , Takao S , Toramatsu C , Nihongi H , Yamada T , Fujii Y , Umezawa M , Umegaki K , Shirato H
Published: July 2014

Purpose:

To improve the accuracy of spot‐scanning proton beam delivery for target in motion, a real‐time tumor‐monitoring and gating system using fluoroscopy images was developed. This study investigates the efficacy of this method for treatment of liver tumors using simulation.

Methods:

Three‐dimensional position of a fiducial marker inserted close to the tumor is calculated in real time and proton beam is gated according to the marker's distance from the planned position (Shirato, 2012). The efficient beam delivery is realized even for the irregular and sporadic motion signals, by employing the multiple‐gated irradiations per operation cycle (Umezawa, 2012). For each of two breath‐hold CTs (CTV=14.6cc, 63.1cc), dose distributions were calculated with internal margins corresponding to freebreathing (FB) and real‐time gating (RG) with a 2‐mm gating window. We applied 8 trajectories of liver tumor recorded during the treatment of RTRT in X‐ray therapy and 6 initial timings. Dmax/Dmin in CTV, mean liver dose (MLD), and irradiation time to administer 3 Gy (RBE) dose were estimated assuming rigid motion of targets by using in‐house simulation tools and VQA treatment planning system (Hitachi, Ltd., Tokyo).

Results:

Dmax/Dmin was degraded by less than 5% compared to the prescribed dose with all motion parameters for smaller CTV and less than 7% for larger CTV with one exception. Irradiation time showed only a modest increase if RG was used instead of FB; the average value over motion parameters was 113 (FB) and 138 s (RG) for smaller CTV and 120 (FB) and 207 s (RG) for larger CTV. In RG, it was within 5 min for all but one trajectory. MLD was markedly decreased by 14% and 5–6% for smaller and larger CTVs respectively, if RG was applied.

Conclusions:

Spot‐scanning proton beam was shown to be delivered successfully to liver tumor without much lengthening of treatment time.

This research was supported by the Cabinet Office, Government of Japan and the Japan Society for the Promotion of Science (JSPS) through the Funding Program for World‐Leading Innovative R&D on Science and Technology (FIRST Program), initiated by the Council for Science and Technology Policy (CSTP).
WE‐D‐17A‐05: Measurement of Stray Radiation Within An Active Scanning Proton Therapy Facility: EURADOS WG9 Intercomparison Exercise of Active Dosimetry Systems
Authors: Farah J , Stolarczyk L , Algranati C , Domingo C , Dufek V , Fellin F , Frojdh E , George S , Harrison R , Klodowska M , Kubancak J , Knezevic Z , Liszka M , Majer M , Mares V , Miljanic S , Ploc O , Romero‐Exposito M , Ruhm W , Schinner K , Schwarz M , Trinkl S , Trompier F , Wielunski M , Olko P
Published: July 2014

Purpose:

Intercomparison of active dosemeters in the measurement of stray radiation at the Trento active‐scanning proton therapy facility.

Methods:

EURADOS WG9 carried out a large intercomparison exercise to test different dosemeters while measuring secondary neutrons within a 230 MeV scanned proton therapy facility. Detectors included two Bonner Sphere Spectrometers (BSS), three tissue equivalent proportional counters (TEPCHawk) and six rem‐counters (Wendi II, Berthold, RadEye, a regular and an extended‐range Anderson & Braun NM2B counters). Measurements of neutron ambient dose equivalents, H*(10), were done at several positions inside (8 positions) and outside (3 positions) the treatment room while irradiating a water tank phantom with a 10 × 10 × 10 cc field.

Results:

A generally good agreement on H*(10) values was observed for the tested detectors. At distance of 2.25 m and angles 45°, 90° and 180° with respect to the beam axis, BSS and proportional counters agreed within 30%. Higher differences (up to 60%) were observed at the closest and farthest distances, i.e. at positions where detectors sensitivity, energy, fluence and angular response are highly dependent on neutron spectra (flux and energy). The highest neutron H*(10) value, ∼60 microSv/Gy, was measured at 1.15 m along the beam axis. H*(10) decreased significantly with the distance from the isocenter dropping to 1.1 microSv/Gy at 4.25 m and 90° from beam axis, ∼2 nanoSv/Gy at the entrance of the maze, 0.2 nanoSv/Gy at the door outside the room and below detection limit in the gantry control room and at an adjacent room. These values remain considerately lower than those of passively scattered proton beams. BSS and Hawk unfolded spectra provide valuable inputs when studying the response of each detector.

Conclusion:

TEPCs and BSS enable accurate measurements of stray neutrons while other rem‐meters also give satisfactory results but require further improvements to reduce uncertainties.
WE‐D‐18A‐01: Evaluation of Three Commercial Metal Artifact Reduction Methods for CT Simulations in Radiation Therapy Treatment Planning
Authors: Huang J , Kerns J , Nute J , Liu X , Stingo F , Followill D , Mirkovic D , Howell R , Kry S
Published: July 2014

Purpose:

To evaluate three commercial metal artifact reduction methods (MAR) in the context of radiation therapy treatment planning.

Methods:

Three MAR strategies were evaluated: Philips O‐MAR, monochromatic imaging using Gemstone Spectral Imaging (GSI) dual energy CT, and monochromatic imaging with metal artifact reduction software (GSIMARs). The Gammex RMI 467 tissue characterization phantom with several metal rods and two anthropomorphic phantoms (pelvic phantom with hip prosthesis and head phantom with dental fillings), were scanned with and without (baseline) metals. Each MAR method was evaluated based on CT number accuracy, metal size accuracy, and reduction in the severity of streak artifacts. CT number difference maps between the baseline and metal scan images were calculated, and the severity of streak artifacts was quantified using the percentage of pixels with >40 HU error (“bad pixels”).

Results:

Philips O‐MAR generally reduced HU errors in the RMI phantom. However, increased errors and induced artifacts were observed for lung materials. GSI monochromatic 70keV images generally showed similar HU errors as 120kVp imaging, while 140keV images reduced errors. GSI‐MARs systematically reduced errors compared to GSI monochromatic imaging. All imaging techniques preserved the diameter of a stainless steel rod to within ±1.6mm (2 pixels). For the hip prosthesis, O‐MAR reduced the average % bad pixels from 47% to 32%. For GSI 140keV imaging, the percent of bad pixels was reduced from 37% to 29% compared to 120kVp imaging, while GSI‐MARs further reduced it to 12%. For the head phantom, none of the MAR methods were particularly successful.

Conclusion:

The three MAR methods all improve CT images for treatment planning to some degree, but none of them are globally effective for all conditions. The MAR methods were successful for large metal implants in a homogeneous environment (hip prosthesis) but were not successful for the more complicated case of dental artifacts.
WE‐D‐18A‐06: Estimating Local Noise Power Spectrum From a Few CT Scans
Authors: Zeng R , Gavrielides M , Li Q , Petrick N , Sahiner B , Myers K
Published: July 2014

Purpose:

The traditional way to estimate CT NPS is by averaging the power spectrum of many noisy scans. When only a few scans are available, regions of interests are often extracted from different locations to obtain sufficient samples to estimate NPS, thus ignoring the nonstationarity of CT noise. This approach to estimating NPS does not accurately reflect the location‐variant characteristics of CT noise. The purpose of this work is to develop a method to estimate local NPS from only a few CT scans.

Methods:

As a result of the FBP reconstruction algorithm, the CT NPS presents the following radial property: the shape of the radial profile of the NPS is almost constant, determined by the reconstruction filter, and the magnitude varies with angle depending on the object attenuation map. Therefore, a shape function and an angular magnitude function are sufficient to describe the CT NPS. Based on this property, the dimensionality of the NPS is greatly reduced and we are able to derive a radial NPS method to estimate the NPS from only a few scans.

Results:

We applied the radial NPS method to simulated CT scans of a nonuniform object. The results showed that the local NPS estimated from only 6 scans using the radial method was very close to the NPS estimated using the traditional method from 400 scans, according to normalized mean squared error (NMSE) and the signal detectability based on an NPS‐prewhitening Hoteling model observer. We also applied this method to physical phantom scans. Good accuracy was again achieved from only 6 scans using the radial NPS method.

Conclusion:

The radial NPS method was shown to be accurate and efficient in estimating the local NPS of FBP reconstructed CT images. This method is readily extendable to estimating the NPS of helical CT scans.
WE‐D‐9A‐03: CSDF: A Color Extension of the Grayscale Standard Display Function
Authors: Kimpe T , Avanaki A , Marchessoux C , Rostang J , Espig K , Piepers B , Xthona A
Published: July 2014

Purpose:

Use of color images in medical imaging has increased significantly the last few years. As of today there is no agreed standard on how color information needs to be visualized on medical color displays, resulting into large variability of color appearance and it making consistency and quality assurance a challenge. This paper presents a proposal for an extension of DICOM GSDF towards color.

Methods:

Visualization needs for several color modalities (multimodality imaging, nuclear medicine, digital pathology, quantitative imaging applications…) have been studied. On this basis a proposal was made for desired color behavior of color medical display systems and its behavior and effect on color medical images was analyzed.

Results:

Several medical color modalities could benefit from perceptually linear color visualization for similar reasons as why GSDF was put in place for greyscale medical images. An extension of the GSDF (Greyscale Standard Display Function) to color is proposed: CSDF (color standard display function). CSDF is based on deltaE2000 and offers a perceptually linear color behavior. CSDF uses GSDF as its neutral grey behavior. A comparison between sRGB/GSDF and CSDF confirms that CSDF significantly improves perceptual color linearity. Furthermore, results also indicate that because of the improved perceptual linearity, CSDF has the potential to increase perceived contrast of clinically relevant color features.

Conclusion:

There is a need for an extension of GSDF towards color visualization in order to guarantee consistency and quality. A first proposal (CSDF) for such extension has been made. Behavior of a CSDF calibrated display has been characterized and compared with sRGB/GSDF behavior. First results indicate that CSDF could have a positive influence on perceived contrast of clinically relevant color features and could offer benefits for quantitative imaging applications.

Authors are employees of Barco Healthcare
WE‐D‐9A‐05: Medical Hyperspectral Imaging for the Detection of Head and Neck Cancer in Animal Models
Authors: Fei B , Lu G , Pike R , Wang D , Chen G
Published: July 2014

Purpose:

The objective of this study is to develop hyperspectral imaging technology and advanced image analysis methods for the detection of head and neck cancer.

Methods:

A head and neck tumor xenograft model was used in the experiment. The M4E head and neck cancer cells with green fluorescence protein (GFP) were injected into nude mice. Hyperspectral images were acquired from the tumor‐bearing mice using a CRI Maestro invivo imaging camera. The wavelength setting was defined within the range of 450–950 nm with 2 nm increments. Two advanced image classification methods were developed to classify normal and cancer tissue on hyperspectral images. In the first method, a tensor‐based computation and modeling framework was proposed for the analysis of hyperspectral images for cancer detection. In the second classification method, support vector machines were incorporated into a minimum spanning forest algorithm for differentiating cancer tissue from normal tissue. The classification results were validated by the GPP images of the same animals.

Results:

The tensor‐based classification method can distinguish between malignant tissue and healthy tissue with an average sensitivity of 97.0% and an average specificity of 91.4% in tumor‐bearing mice. The minimum spanning forest algorithm also achieved a high accuracy of more than 97.0% in the animal model.

Conclusion:

The hyperspectral imaging and classification technology has been demonstrated in animal models and can have many potential applications in cancer research and management.

This research is supported in part by NIH grants (R01CA156775, R21CA176684, and P50CA128301) and Georgia Cancer Coalition Distinguished Clinicians and Scientists Award.
WE‐D‐9A‐06: Open Source Monitor Calibration and Quality Control Software for Enterprise Display Management
Authors: Bevins N , Vanderhoek M , Lang S , Flynn M
Published: July 2014

Purpose:

Medical display monitor calibration and quality control present challenges to medical physicists. The purpose of this work is to demonstrate and share experiences with an open source package that allows for both initial monitor setup and routine performance evaluation.

Methods:

A software package, pacsDisplay, has been developed over the last decade to aid in the calibration of all monitors within the radiology group in our health system. The software is used to calibrate monitors to follow the DICOM Grayscale Standard Display Function (GSDF) via lookup tables installed on the workstation. Additional functionality facilitates periodic evaluations of both primary and secondary medical monitors to ensure satisfactory performance. This software is installed on all radiology workstations, and can also be run as a stand‐alone tool from a USB disk. Recently, a database has been developed to store and centralize the monitor performance data and to provide long‐term trends for compliance with internal standards and various accrediting organizations.

Results:

Implementation and utilization of pacsDisplay has resulted in improved monitor performance across the health system. Monitor testing is now performed at regular intervals and the software is being used across multiple imaging modalities. Monitor performance characteristics such as maximum and minimum luminance, ambient luminance and illuminance, color tracking, and GSDF conformity are loaded into a centralized database for system performance comparisons. Compliance reports for organizations such as MQSA, ACR, and TJC are generated automatically and stored in the same database.

Conclusion:

An open source software solution has simplified and improved the standardization of displays within our health system. This work serves as an example method for calibrating and testing monitors within an enterprise health system.
WE‐E‐BRD‐01: HDR Brachytherapy I: Overview of Clinical Application and QA
Authors: Libby B , Showalter T
Published: July 2014

With the increased usage of high dose rate (HDR) brachytherapy and the introduction of dedicated image guided brachytherapy suites, it is necessary to review the processes and procedures associated with safely delivering these treatments in the expedited time scales that dedicated treatment suites afford.

The speakers will present the clinical aspects of switching from LDR to HDR treatments, including guidelines for patient selection, and the clinical outcomes comparing LDR to HDR. The speakers will also discuss the HDR treatment process itself, because the shortened clinical timeline involved with a streamlined scan/plan/treat workflow can introduce other issues. Safety and QA aspects involved with the streamlined process, including increased personnel required for parallel tasks, and possible interfering tasks causing delays in patient treatments will also be discussed.

Learning Objectives:

To understand the clinical aspects of HDR Brachytherapy, including common clinical indications, patient selection, and the evolving evidence in support of this therapeutic modality

To review the current prominent clinical trials for HDR brachytherapy

To interpret the established guidelines for HDR brachytherapy quality assurance for implementation into practical clinical settings.

To introduce the basic requirements for image guided brachytherapy