bluuebunny/crossref_metadata_2025_split huggingface dataset:
TU‐C‐12A‐08: Thermally‐Stabilized Isotropic Diffusion Phantom for Multisite Assessment of Apparent Diffusion Coefficient Reproducibilty
Authors: Boss M , Chenevert T , Waterton J , Morris D , Ragheb H , Jackson A , deSouza N , Collins D , van Beers B , Garteiser P , Doblas S , Persigehl T , Hedderich D , Martin A , Mukherjee P , Keenan K , Russek S , Jackson E , Zahlmann G 
Published: July 2014

Purpose:To construct an appropriate phantom for quality control use in diffusion‐weighted imaging (DWI), to establish ground truth for measurement of apparent diffusion coefficient (ADC) and to characterize measurement linearity across a relevant physiological range of ADC.Methods:Aqueous solutions containing the polymer polyvinylpyrrolidone (PVP) were mixed at concentrations of 0, 10, 20, 30, 40 and 50% by mass PVP. These solutions were placed in 20 mL vials, arranged in concentric inner and outer circles, with a central water vial, and were fixed in a spherical phantom with a diameter of 194 mm, designed to fit into commercially‐available MRI head coils. Two prototype phantoms were constructed, and underwent inter‐site comparison in the US and EU. The phantoms were filled with an ice‐water bath to ensure stable temperature; 0 °C temperature was verified by use of a thermocouple before and after scans. The phantoms were scanned using b‐values of 0, 500 and 900 s/mm2 at several sites, using coronal and/or axial orientations and scan planes.Results:ADC values ranged from 0.12 to 1.12 × 10‐3 mm2/s, and exhibited a high degree of reproducibility across different scanners and imaging sites (coefficient of variations (CoV) ranged from 1.1 to 2.2% for 0 to 40% PVP, with 50% PVP at 11.3%). Little difference in ADCs was seen between inner and outer ring vials of the same PVP concentration (average CoV< 5% across vials, 10.3% for 50% PVP).Conclusion:The range of ADCs covers a relevant physiological range, most notably in brain white matter. The ADCs of water vials were in excellent agreement with literature values of the diffusion coefficient of water at 0 °C (1.1 × 10‐3 mm2/s). The phantom provides a much needed quality control tool for DWI, and provides ground truth with the diffusion coefficient of water at 0 °C.
TU‐D‐BRD‐01: Image Guided SBRT II: Challenges ' Pitfalls
Authors: Chang Z , Yin F , Cho J 
Published: July 2014

Stereotactic body radiation therapy (SBRT) has been effective treatment for the management of various diseases, which often delivers high radiation dose in a single or a few fractions. SBRT therefore demands precise treatment delivery to the tumor while sparing adjacent healthy tissue. Recent developments in image guidance enable target localization with increased accuracy. With such improvements in localization, image‐guided SBRT has been widely adopted into clinical practice. In SBRT, high radiation dose is generally delivered with small fields. Therefore, it is crucial to accurately measure dosimetric data for the small fields during commissioning. In addition, image‐guided SBRT demands accurate image localization to ensure safety and quality of patient care. Lately, the reports of AAPM TG 142 and TG 104 have been published and added recommendations for imaging devices that are integrated with the linear accelerator for SBRT. Furthermore, various challenges and potential pitfalls lie in the clinical implementation of image‐guided SBRT. In this lecture, these challenges and pitfalls of image‐guided SBRT will be illustrated and discussed from dosimetric, technical and clinical perspectives.Being a promising technique, image‐guided SBRT has shown great potentials, and will lead to more accurate and safer SBRT treatments.Learning Objectives:

To understand dosimetric challenges and pitfalls for IGRT application in SBRT.
To understand major clinical challenges and pitfalls for IGRT application in SBRT.
To understand major technical challenges and pitfalls for IGRT application in SBRT.
TU‐D‐9A‐01: TG176: Dosimetric Effects of Couch Tops and Immobilization Devices
Authors: Olch A 
Published: July 2014

The dosimetric impact from devices external to the patient is a complex combination of increased skin dose, reduced tumor dose, and altered dose distribution. Although small monitor unit or dose corrections are routinely made for blocking trays, ion chamber correction factors, or tissue inhomogeneities, the dose perturbation of the treatment couch top or immobilization devices are often overlooked. These devices also increase surface dose, an effect which is also often ignored or underestimated. These concerns have grown recently due to the increased use of monolithic carbon fiber couch tops which are optimal for imaging for patient position verification but cause attenuation and increased surface dose compared to the ‘tennis racket’ style couch top they often replace. Also, arc delivery techniques have replaced stationary gantry techniques which cause a greater fraction of the dose to be delivered from posterior angles. A host of immobilization devices are available and used to increase patient positioning reproducibility, and these also have attenuation and skin dose implications which are often ignored. This report of Task Group 176 serves to present a survey of published data that illustrates the magnitude of the dosimetric effects of a wide range of devices external to the patient. The report also provides methods for modeling couch tops in treatment planning systems so the physicist can accurately compute the dosimetric effects for indexed patient treatments. Both photon and proton beams are considered. A discussion on avoidance of high density structures during beam planning is also provided. An important aspect of this report are the recommendations we make to clinical physicists, treatment planning system vendors, and device vendors on how to make measurements of skin dose and attenuation, how to report these values, and for the vendors, an appeal is made to work together to provide accurate couch top models in planning systems.Learning Objectives:

What are the dosimetric effects of couch tops
What are the dosimetric effects of immobilization devices
How can one model couch tops in the treatment planning system
How can one measure attenuation and surface dose changes due to external devices
TU‐F‐BRE‐07: In Vivo Neutron Detection in Patients Undergoing Stereotactic Ablative Radiotherapy (SABR) for Primary Kidney Cancer Using 6Li and 7Li Enriched TLD Pairs
Authors: Lonski P , Franich R , Siva S , Keehan S , Taylor M , Kron T 
Published: July 2014

Purpose:Stereotactic ablative radiotherapy (SABR) for primary kidney cancer often involves the use of high‐energy photons combined with a large number of monitor units. While important for risk assessment, the additional neutron dose to untargeted healthy tissue is not accounted for in treatment planning. This work aims to detect out‐of‐field neutrons in vivo for patients undergoing SABR with high‐energy (>10 MV) photons and provides preliminary estimates of neutron effective dose.Methods:3 variations of high‐sensitivity LiF:Mg,Cu,P thermoluminescent dosimeter (TLD) material, each with varying 6Li / 7Li concentrations, were used in custom‐made Perspex holders for in vivo measurements. The variation in cross section for thermal neutrons between Li isotopes was exploited to distinguish neutron from photon signal. Measurements were made out‐of‐field for 7 patients, each undergoing 3D‐conformal SABR treatment for primary kidney cancer on a Varian 21iX linear accelerator.Results:In vivo measurements show increased signal for the 6Li enriched material for patients treated with 18 MV photons. Measurements on one SABR patient treated using only 6 MV showed no difference between the 3 TLD materials. The out‐of‐field photon signal decreased exponentially with distance from the treatment field. The neutron signal, taken as the difference between 6Li enriched and 7Li enriched TLD response, remains almost constant up to 50 cm from the beam central axis. Estimates of neutron effective dose from preliminary TLD calibration suggest between 10 and 30 mSv per 1000 MU delivered at 18 MV for the 7 patients.Conclusion:TLD was proven to be a useful tool for the purpose of in vivo neutron detection at out‐of‐field locations. Further work is required to understand the relationship between TL signal and neutron dose. Dose estimates based on preliminary TLD calibration in a neutron beam suggest the additional neutron dose was <30 mSv per 1000 MU at 18 MV.
TU‐F‐BRE‐08: Significant Variations in Measured Small Cone Output Factor for FFF Beams
Authors: Sudhyadhom A , Ma L , Kirby N 
Published: July 2014

Purpose:To evaluate the measurement accuracy of several dosimeters for small cone output factors in two SRS/SBRT dedicated systems with Flattening Filter Free (FFF) beams: a Varian TrueBeam STx (TB) and an Accuray CyberKnife VSI (CK). Output factors (OFs) were measured for both machines and for CK, compared against a Monte Carlo model.Methods:Dose measurements were taken using three different FFF beams (TB 6XFFF, TB 10XFFF, and CK 6XFFF). Three commonly used types of dosimeters were examined in this work: a micro‐ion chamber (Exradin A16), two shielded diodes (PTW TN60008 and PTW TN60017), and radiochromic film (Gafchromic EBT2). Measured OFs from these dosimeters were compared with each other and OFs measured with an Exradin W1 scintillator. Monte Carlo determined correction factors for the CK beam for the micro‐ion chamber and diodes were applied to the respective OF measurements and compared against scintillator measured OFs corrected for volume averaging.Results:OFs measured for the smallest fields using the micro‐ion chamber, diodes, scintillator, and film varied substantially (with up to a 16% difference between dosimeters). Micro‐ion chamber and film OF measurements were up to 9% and 10%, respectively, lower than scintillator measurements for the smallest fields. OF measurements by diode were up to 6% greater than scintillator measurements for the smallest fields. With correction factors, the micro‐ion chamber and diode measured OFs showed good agreement with scintillator measured OFs for the CK 6XFFF beam (within 3% and 1.5%, respectively).Conclusion:Uncorrected small field OFs vary significantly with dosimeter. The accuracy of scintillator measurements for small field OFs may be greater than the other dosimeters studied in this work (when uncorrected). Measurements involving EBT2 film may Result in lower accuracy for smaller fields (less than 10mm). Care should be taken in the choice of the dosimeter used for small field OF measurements.
TU‐F‐BRE‐09: Towards the Establishment of Dosimetric References in Small Fields Using the New Concept of Dose‐Area Product
Authors: Dufreneix S , Bordy J , Delaunay F , Delaunay F , Daures J , Gouriou J , Le Roy M , Ostrowsky A , Rapp B , Sommier L 
Published: July 2014

Purpose:To establish dosimetric references of absorbed dose in water in radiation fields smaller than 2 cm used in radiotherapy thanks to a new methodology based on the use of dosimeters larger than the field size.Methods:A new graphite calorimeter was constructed with a large sensitive volume (diameter of the core: 30 mm). This primary dosimeter was fully characterized and compared to previous LNE‐LNHB graphite calorimeters in a 60Co large field. A specially designed graphite parallel‐plate ionization chamber with a 30 mm collecting electrode was also assembled and tested. Measurements were then conducted in two 6 MV small circular fields of 2 cm and 1 cm diameter respectively, using the new concept of dose‐area product instead of punctual dose commonly used in radiotherapy.Results:The dose rate established in a large 60Co field with the new calorimeter is in agreement within 0.4% with previous calorimeters. The ionization chamber shows good characteristics except for a 0.06% drift per hour in water. The ratio of calorimetric against ionometric measurements in the 2 cm diameter field is 1.1% higher than the one in the 1 cm diameter field (with respectively 0.30% and 1.03% type A uncertainty for each field).Conclusion:Results presented here highlight the possibility of measuring dose‐area products in small fields with a graphite calorimeter and a parallel‐plate ionization chamber. Measurements in a 0.75 cm diameter field are already underway to confirm the trend observed in the 2 cm and 1 cm diameter fields. The last step to establish precise dosimetric references in small fields is to calculate correction factors thanks to Monte Carlo simulations.
TU‐F‐BRF‐05: Level Set Based Segmentation with a Dynamic Shape Prior
Authors: Liu W , Ruan D 
Published: July 2014

Purpose:To perform accurate segmentation on low‐SNR MR images subject to motion artifacts and signal voids.Methods:We have developed a novel level set based segmentation method that incorporates a dynamic shape prior. In contrast to conventional shape prior models that are either based on a single template or statistical models, we modeled the shape prior as sparse linear combinations of templates in a shape library. The proposed method was applied to segment real‐time kidney geometry from an abdominal MR series acquired under respiration and compared with the Chan‐Vese approach. Synthetic occlusions were further introduced to assess performance robustness. We compared the segmentation results with the ground truth contours and evaluated the segmentation accuracy based on the Dice similarity coefficient.Results:The proposed method successfully segmented all kidneys in the testing series. The corresponding shape priors were reasonably reconstructed from a small number of shape templates in the library, as expected. On testing dataset without occlusion, the proposed method achieved mean DSC of 0.97, which was more accurate than the Chan‐Vese approach with a DSC of 0.93. When tested on dataset with synthetic occlusions, the proposed method made robust inference on the occlusion sites and achieved mean DSC of 0.95, compared to 0.76 from the Chan‐Vese method, demonstrating the advantage of incorporating the proposed shape prior.Conclusion:We have developed a novel level set based segmentation method with a novel regularization to incorporate a dynamic shape prior. The shape prior is dynamically updated during the segmentation process as a sparse linear combination of templates from a shape library. Preliminary results have demonstrated the ability of the proposed method in improving segmentation accuracy, especially when noises and/or signal voids are present. Future work will consider dynamically update and evolve the shape library to encode shape priors as segmentations are being performed.
TU‐F‐BRF‐09: Feasibility Study of Spatial and Temporal Fractionation Using a Table‐Top Image‐Guided MRT System
Authors: Zhang L , Inscoe C , Yuan H , Burk L , Ger R , Chtcheprov P , Lu J , Chang S , Zhou O 
Published: July 2014

Purpose:Microbeam radiation therapy is a promising experimental radiotherapy method for cancer treatment. Synchrotron studies have shown that MRT can preferentially ablate tumors while mostly preserving the surrounding normal tissues. Our purpose is to develop a compact microbeam irradiator that can be accessible for laboratory research on MRT's therapeutic mechanism, with the ultimate goal of translating this technique for clinical applications. Utilizing a carbon nanotube field emission X‐ray source array, our lab has developed a first of its kind table‐top microbeam irradiator. The purpose of this study is to investigate the possibility of increasing the total dose to the tumor region using spatial and temporal fractionation.Methods:MRI and CT scans were acquired and registered to locate both the target region and the landmark in the treatment coordinate space. A crossbeam treatment configuration was planned to achieve the desired dosage and tumor coverage. One array of 300 μm‐thick microbeams was delivered to the target on the first day. Another array, perpendicular to the first one, was delivered the next day targeting the same region. The feasibility of this image‐guided MRT procedure was evaluated using a phantom. Gafchromic EBT2 film was employed to characterize the targeting accuracy and the delivered tumor dose.Results:The preliminary phantom study showed that a cross‐pattern of microbeam arrays was successfully delivered with sub‐millimeter targeting accuracy. The delivered dose in the target region was doubled. The fraction of tumor volume that received the peak dose was increased.Conclusion:Temporal fractionation of crosspatterned microbeams can be delivered to the same target region. The feasibility of this procedure was investigated with a phantom study. Once implemented, this procedure has the potential of increasing the tumor control effect of MRT and of achieving better normal tissue recovery.
TU‐F‐17A‐01: BEST IN PHYSICS (JOINT IMAGING‐THERAPY) – An Automatic Toolkit for Efficient and Robust Analysis of 4D Respiratory Motion
Authors: Wei J , Yuan A , Li G 
Published: July 2014

Purpose:To provide an automatic image analysis toolkit to process thoracic 4‐dimensional computed tomography (4DCT) and extract patient‐specific motion information to facilitate investigational or clinical use of 4DCT.Methods:We developed an automatic toolkit in MATLAB to overcome the extra workload from the time dimension in 4DCT. This toolkit employs image/signal processing, computer vision, and machine learning methods to visualize, segment, register, and characterize lung 4DCT automatically or interactively. A fully‐automated 3D lung segmentation algorithm was designed and 4D lung segmentation was achieved in batch mode. Voxel counting was used to calculate volume variations of the torso, lung and its air component, and local volume changes at the diaphragm and chest wall to characterize breathing pattern. Segmented lung volumes in 12 patients are compared with those from a treatment planning system (TPS). Voxel conversion was introduced from CT# to other physical parameters, such as gravity‐induced pressure, to create a secondary 4D image. A demon algorithm was applied in deformable image registration and motion trajectories were extracted automatically. Calculated motion parameters were plotted with various templates. Machine learning algorithms, such as Naive Bayes and random forests, were implemented to study respiratory motion. This toolkit is complementary to and will be integrated with the Computational Environment for Radiotherapy Research (CERR).Results:The automatic 4D image/data processing toolkit provides a platform for analysis of 4D images and datasets. It processes 4D data automatically in batch mode and provides interactive visual verification for manual adjustments. The discrepancy in lung volume calculation between this and the TPS is <±2% and the time saving is by 1–2 orders of magnitude.Conclusion:A framework of 4D toolkit has been developed to analyze thoracic 4DCT automatically or interactively, facilitating both investigational and clinical use. More software tools are under development for automatic analysis of other 4D imaging modalities.This research is in part supported by NIH (U54CA137788/132378) and City Seed FY13(Grant No. 93348‐14 01). 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.
TU‐F‐17A‐06: Motion Stability and Dosimetric Impact of Spirometer‐Based DIBH‐RT of Left‐Sided Breast Cancer
Authors: McKenzie E , Yang W , Burnison M , Mirhadi A , Hakimian B , Stephen S , Robert R , Yue Y , Sandler H , Fraass B 
Published: July 2014

Purpose:Patients undergoing radiotherapy (RT) for left‐sided breast cancer have increased risk of coronary artery disease. Deep Inhalation Breath Hold assisted RT (DIBH‐RT) is shown to increase the geometric separation of the target area and heart, reducing cardiac radiation dose. The purposes of this study are to use Cine MV portal images to determine the stability of spirometer‐guided DIBH‐RT and examine the dosimetric cardiopulmonary impact of this technique.Methods:Twenty consecutive patients with left‐sided breast cancer were recruited to the IRB‐approved study. Free‐breathing (FB) and DIBH‐CT's were acquired at simulation. Rigid registration of the FB‐CT and DIBH‐CT was performed using primarily breast tissue. Treatment plans were created for each FB‐CT and DIBH‐CT using identical paired tangent fields with field‐in‐field or electronic compensation techniques. Dosimetric evaluation included mean and maximum (Dmax) doses for the left anterior descending artery (LAD), mean heart dose, and left lung V20. Cine MV portal images were acquired for medial and lateral fields during treatment. Analysis of Cine images involved chest wall segmentation using an algorithm developed in‐house. Intra‐ and inter‐fractional chest wall motion were determined through affine registration to the first frame of each Cine.Results:Dose to each cardiac structure evaluated was significantly (p<0.001) reduced with the DIBH plans. Mean heart dose decreased from 2.9(0.9–6.6) to 1.6(0.6–5.3) Gy; mean LAD dose from 16.6(3–43.6) to 7.4(1.7–32.7) Gy; and LAD Dmax from 35.4 (6.1–53) to 18.4(2.5–51.2) Gy. No statistically significant reduction was found for the left lung V20. Average AP and SI median chest wall motion (intrafractional) was 0.1 (SD=0.9) and 0.5 (SD=1.1) mm, respectively. Average AP inter‐fractional chest wall motion was 2.0 (SD=1.4) mm.Conclusion:Spirometer‐based DIBH treatments of the left breast are reproducible both inter‐ and intra‐fractionally, and provide a statistically and potentially clinically useful dosimetric advantage to cardiac structures.
WE‐D‐9A‐04: Improving Multi‐Modality Image Registration Using Edge‐Based Transformations
Authors: Wang Y , Tyagi N , Veeraraghavan H , Deasy J 
Published: July 2014

Purpose:Multi‐modality deformable image registration (DIR) for head & neck (HN) radiotherapy is difficult, particularly when matching computed tomography (CT) scans with magnetic resonance imaging (MRI) scans. We hypothesized that the ‘shared information’ between images of different modalities was to be found in some form of edge‐based transformation, and that novel edge‐based DIR methods might outperform standard DIR methods.Methods:We propose a novel method that combines gray‐scale edge‐based morphology and mutual information (MI) in two stages. In the first step, we applied a modification of a previously published mathematical morphology method as an efficient gray scale edge estimator, with denoising function. The results were fed into a MI‐based solver (plastimatch). The method was tested on 5 HN patients with pretreatment CT and MR datasets and associated follow‐up weekly MR scans. The followup MRs showed significant regression in tumor and normal structure volumes as compared to the pretreatment MRs. The MR images used in this study were obtained using fast spin echo based T2w images with a 1 mm isotropic resolution and FOV matching the CT scan.Results:In all cases, the novel edge‐based registration method provided better registration quality than MI‐based DIR using the original CT and MRI images. For example, the mismatch in carotid arteries was reduced from 3–5 mm to within 2 mm. The novel edge‐based method with different registration regulation parameters did not show any distorted deformations as compared to the non‐realistic deformations resulting from MI on the original images. Processing time was 1.3 to 2 times shorter (edge vs. non‐edge). In general, we observed quality improvement and significant calculation time reduction with the new method.Conclusion:Transforming images to an ‘edge‐space,’ if designed appropriately, greatly increases the speed and accuracy of DIR.