bluuebunny/crossref_metadata_2025_split huggingface dataset:
TH‐E‐BRF‐08: Subpopulations of Similarly‐Responding Lesions in Metastatic Prostate Cancer
Authors: Lin C , Harmon S , Perk T , Jeraj R 
Published: July 2014

Purpose:In patients with multiple lesions, resistance to cancer treatments and subsequent disease recurrence may be due to heterogeneity of response across lesions. This study aims to identify subpopulations of similarly‐responding metastatic prostate cancer lesions in bone using quantitative PET metrics.Methods:Seven metastatic prostate cancer patients treated with AR‐directed therapy received pre‐treatment and mid‐treatment [F‐18]NaF PET/CT scans. Images were registered using an articulated CT registration algorithm and transformations were applied to PET segmentations. Midtreatment response was calculated on PET‐based texture features. Hierarchical agglomerative clustering was used to form groups of similarly‐responding lesions, with the number of natural clusters (K) determined by the inconsistency coefficient. Lesion clustering was performed within each patient, and for the pooled population. The cophenetic coefficient (C) quantified how well the data was clustered. The Jaccard Index (JI) assessed similarity of cluster assignments from patient clustering and from population clustering.Results:188 lesions in seven patients were identified for analysis (between 6 to 53 lesions per patient). Lesion response was defined as percent change relative to pre‐treatment for 23 uncorrelated PET‐based feature identifiers. . High response heterogeneity was found across all lesions (i.e. range ΔSUVmax =−95.98% to 775.00%). For intra‐patient clustering, K ranged from 1–20. Population‐based clustering resulted in 75 clusters, of 1‐6 lesions each. Intra‐patient clustering resulted in higher quality clusters than population clustering (mean C=0.95, range=0.89 to 1.00). For all patients, cluster assignments from population clustering showed good agreement to intra‐patient clustering (mean JI=0.87, range=0.68 to 1.00).Conclusion:Subpopulations of similarly‐responding lesions were identified in patients with multiple metastatic lesions. Good agreement was found between population‐ and patient‐level clustering, indicating that PET‐based response features may be used to quantify disease heterogeneity in advanced metastatic disease. This method for categorizing lesion response could help in identifying lesions with similar phenotypic‐ or genetic‐based resistances to therapy.Research Supported by the Prostate Cancer Foundation.
TH‐E‐BRF‐10: Interim Esophageal Cancer Response Assessment Via 18FDG‐PET Scanning During Radiation Therapy
Authors: Higgins K , Wu Q , Perez B , Czito B , Palta M , Willett C , Das S 
Published: July 2014

Purpose:Local failure occurs in a large proportion of esophageal cancer patients treated with chemoradiation. The treatment strategy for non‐responders could potentially be modified if they are identified during therapy. This work investigates the utility of an interim 18FDG‐PET scan acquired during the course of therapy as a predictor of pathological response post‐therapy.Methods:Fifteen patients underwent 18FDG‐PET scanning prior to radiation therapy (RT) and once during RT, after delivery of ∼32 Gy. The physician‐contoured GTV on the planning CT scan was used to automatically segment a PET‐based GTV on the pre‐RT PET (GTV‐pre‐PET) as the volume with >40% of the maximum GTV PET SUV value. The pre‐ and intra‐RT CTs were deformably registered to each other to transfer the GTV‐pre‐PET to the intra‐RT PET (GTV‐intra‐PET). The fractional decrease in the maximum SUV, mean SUV and the SUV to the highest intensity 10% – 90% volumes from GTV‐pre‐PET to GTV‐intra‐PET were compared to pathological response assessed at the time of post‐RT surgery.Results:Based on post‐treatment pathology of 15 patients, 7 were classified as achieving favorable response (treatment effect grade ≤ 1) and 8 as unfavorable response (treatment effect grade > 1). Neither fractional decrease in maximum SUV nor mean SUV were significant between the favorable and unfavorable groups. However, the fractional decrease in SUV20% (SUV to the highest 20% volume) was significant (p = 0.02), with an area under the Receiver Operating Characteristics (ROC) curve of 0.84. An optimal cutoff value of 0.46 for this metric was able to distinguish between the two groups with 71% sensitivity (favorable) and 88% specificity (unfavorable).Conclusion:The fractional decrease in SUV to the volume with highest 20% intensity from pre‐ to intra‐RT 18FDG‐PET imaging may be used to distinguish between favorable and unfavorable responders with high sensitivity and specificity.
TH‐E‐BRF‐11: Dynamic Treatment of Clinical Margins Beyond the PET‐Avid Target in Emission Guided Radiation Therapy: A Retrospective Patient Study
Authors: Nanduri A , Fan Q , Yang J , Yamamoto T , Graves E , Loo B , Mazin S 
Published: July 2014

Purpose:Emission guided radiation therapy (EGRT) is a new modality that uses PET emissions for direct real‐time tumor tracking. Radiation beamlets are delivered along PET lines of response (LOR' s) by a fast rotating PET‐Linac closed ring gantry. In this work, we develop a scheme to treat clinical margins defined proximal to the moving PET‐avid tumor, while maintaining EGRT's inherent real‐time tracking ability.Methods:The principle of EGRT is to deliver radiation along PET emission paths to concentrate dose in the PET‐avid gross tumor volume (GTV). To account for adjacent non‐ PET avid regions in the clinical volume (CTV) a method was developed that expands the set of radiation beamlet responses to include the effective margin extension from the GTV to the CTV. An LOR detection may now Result in multiple beamlet responses: one along the original LOR, and others that are adjacent to it in the direction of margin extension. Evaluation studies were performed on a 4D digital patient as well as a clinical breast cancer patient with moving lung tumors. Emission data were obtained using GATE and a commercial PET scanner. Dose delivery was simulated using VMC++. For the patient study, Philips Pinnacle was used for planning and Mirada RTx was used for deformable dose registration across multiple breathing phases.Results:Compared with IMRT, the EGRT margin extension method achieved a 25.3% and 9.0% relative increase in dose to 95% of the CTV for the digital and clinical patients, respectively. The corresponding CTV dose increases without margin extension were 9.7% and 1.4%. The organs at risk doses were kept similar or lower for EGRT in both cases, with tumor tracking preserved.Conclusions:With the capability of accurate treatment of the moving CTV, EGRT has the potential to enable a practical and effective implementation of 4D biologically guided radiation therapy.Authors SRM and AN are stockholders of RefleXion Medical
TH‐E‐17A‐01: Internal Respiratory Surrogate for 4D CT Using Fourier Transform and Anatomical Features
Authors: Hui C , Suh Y , Robertson D , Pan T , Das P , Crane C , Beddar S 
Published: July 2014

Purpose:To develop a novel algorithm to generate internal respiratory signals for sorting of four‐dimensional (4D) computed tomography (CT) images.Methods:The proposed algorithm extracted multiple time resolved features as potential respiratory signals. These features were taken from the 4D CT images and its Fourier transformed space. Several low‐frequency locations in the Fourier space and selected anatomical features from the images were used as potential respiratory signals. A clustering algorithm was then used to search for the group of appropriate potential respiratory signals. The chosen signals were then normalized and averaged to form the final internal respiratory signal. Performance of the algorithm was tested in 50 4D CT data sets and results were compared with external signals from the real‐time position management (RPM) system.Results:In almost all cases, the proposed algorithm generated internal respiratory signals that visibly matched the external respiratory signals from the RPM system. On average, the end inspiration times calculated by the proposed algorithm were within 0.1 s of those given by the RPM system. Less than 3% of the calculated end inspiration times were more than one time frame away from those given by the RPM system. In 3 out of the 50 cases, the proposed algorithm generated internal respiratory signals that were significantly smoother than the RPM signals. In these cases, images sorted using the internal respiratory signals showed fewer artifacts in locations corresponding to the discrepancy in the internal and external respiratory signals.Conclusion:We developed a robust algorithm that generates internal respiratory signals from 4D CT images. In some cases, it even showed the potential to outperform the RPM system. The proposed algorithm is completely automatic and generally takes less than 2 min to process. It can be easily implemented into the clinic and can potentially replace the use of external surrogates.
TH‐E‐17A‐04: Geometric Validation of K‐Space Self‐Gated 4D‐MRI Vs. 4D‐CT Using A Respiratory Motion Phantom
Authors: Yue Y , Fan Z , Yang W , Pang J , McKenzie E , Deng Z , Tuli R , Sandler H , Li D , Fraass B 
Published: July 2014

Purpose:4D‐CT is often limited by motion artifacts, low temporal resolution, and poor phase‐based target definition. We recently developed a novel k‐space self‐gated 4D‐MRI technique with high spatial and temporal resolution. The goal here is to geometrically validate 4D‐MRI using a MRI‐CT compatible respiratory motion phantom and comparison to 4D‐CT.Methods:4D‐MRI was acquired using 3T spoiled gradient echo‐based 3D projection sequences. Respiratory phases were resolved using self‐gated k‐space lines as the motion surrogate. Images were reconstructed into 10 temporal bins with 1.56×1.56×1.56mm3. A MRI‐CT compatible phantom was designed with a 23mm diameter ball target filled with highconcentration gadolinium(Gd) gel embedded in a 35×40×63mm3 plastic box stabilized with low‐concentration Gd gel. The whole phantom was driven by an air pump. Human respiratory motion was mimicked using the controller from a commercial dynamic phantom (RSD). Four breathing settings (rates/depths: 10s/20mm, 6s/15mm, 4s/10mm, 3s/7mm) were scanned with 4D‐MRI and 4D‐CT (slice thickness 1.25mm). Motion ground‐truth was obtained from input signals and real‐time video recordings. Reconstructed images were imported into Eclipse(Varian) for target contouring. Volumes and target positions were compared with ground‐truth. Initial human study was investigated on a liver patient.Results:4D‐MRI and 4D‐CT scans for the different breathing cycles were reconstructed with 10 phases. Target volume in each phase was measured for both 4D‐CT and 4D‐MRI. Volume percentage difference for the 6.37ml target ranged from 6.67±5.33 to 11.63±5.57 for 4D‐CT and from 1.47±0.52 to 2.12±1.60 for 4D‐MRI. The Mann‐Whitney U‐test shows the 4D‐MRI is significantly superior to 4D‐CT (p=0.021) for phase‐based target definition. Centroid motion error ranges were 1.35–1.25mm (4D‐CT), and 0.31–0.12mm (4D‐MRI).Conclusion:The k‐space self‐gated 4D‐MRI we recently developed can accurately determine phase‐based target volume while avoiding typical motion artifacts found in 4D‐CT, and is being further studied for use in GI targeting and motion management.This work supported in part by grant 1R03CA173273‐01
TH‐E‐17A‐05: Optimizing Four Dimensional Cone Beam Computed Tomography Projection Allocation to Respiratory Bins
Authors: OBrien R , Shieh C , Kipritidis J , Keall P 
Published: July 2014

Purpose:Four dimensional cone beam computed tomography (4DCBCT) is an emerging image guidance strategy but it can suffer from poor image quality. To avoid repeating scans it is beneficial to make the best use of the imaging data obtained. For conventional 4DCBCT the location and size of respiratory bins is fixed and projections are allocated to the respiratory bin within which it falls. Strictly adhering to this rule is unnecessary and can compromise image quality. In this study we optimize the size and location of respiratory bins and allow projections to be sourced from adjacent phases of the respiratory cycle.Methods:A mathematical optimization framework using mixed integer quadratic programming has been developed that determines when to source projections from adjacent respiratory bins and optimizes the size and location of the bins. The method, which we will call projection sharing, runs in under 2 seconds of CPU time. Five 4DCBCT datasets of stage III‐IV lung cancer patients were used to test the algorithm. The standard deviation of the angular separation between projections (SD‐A) and the standard deviation in the volume of the reconstructed fiducial gold coil (SD‐V) were used as proxies to measure streaking artefacts and motion blur respectively.Results:The SD‐A using displacement binning and projection sharing was 30%–50% smaller than conventional phase based binning and 59%–76% smaller than conventional displacement binning indicating more uniformly spaced projections and fewer streaking artefacts. The SD‐V was 20–90% smaller when using projection sharing than using conventional phase based binning suggesting more uniform marker segmentation and less motion blur.Conclusion:Image quality was visibly and significantly improved with projection sharing. Projection sharing does not require any modifications to existing hardware and offers a more robust replacement to phase based binning, or, an option if phase based reconstruction is not of a suitable quality.This project is supported by an NHMRC Australia Fellowship and NHMRC project grant number 1034060
TH‐E‐17A‐07: Improved Cine Four‐Dimensional Computed Tomography (4D CT) Acquisition and Processing Method
Authors: Castillo S , Castillo R , Castillo E , Pan T , Ibbott G , Balter P , Hobbs B , Dai J , Guerrero T 
Published: July 2014

Purpose:Artifacts arising from the 4D CT acquisition and post‐processing methods add systematic uncertainty to the treatment planning process. We propose an alternate cine 4D CT acquisition and post‐processing method to consistently reduce artifacts, and explore patient parameters indicative of image quality.Methods:In an IRB‐approved protocol, 18 patients with primary thoracic malignancies received a standard cine 4D CT acquisition followed by an oversampling 4D CT that doubled the number of images acquired. A second cohort of 10 patients received the clinical 4D CT plus 3 oversampling scans for intra‐fraction reproducibility. The clinical acquisitions were processed by the standard phase sorting method. The oversampling acquisitions were processed using Dijkstras algorithm to optimize an artifact metric over available image data. Image quality was evaluated with a one‐way mixed ANOVA model using a correlation‐based artifact metric calculated from the final 4D CT image sets. Spearman correlations and a linear mixed model tested the association between breathing parameters, patient characteristics, and image quality.Results:The oversampling 4D CT scans reduced artifact presence significantly by 27% and 28%, for the first cohort and second cohort respectively. From cohort 2, the inter‐replicate deviation for the oversampling method was within approximately 13% of the cross scan average at the 0.05 significance level. Artifact presence for both clinical and oversampling methods was significantly correlated with breathing period (ρ=0.407, p‐value<0.032 clinical, ρ=0.296, p‐value<0.041 oversampling). Artifact presence in the oversampling method was significantly correlated with amount of data acquired, (ρ=‐0.335, p‐value<0.02) indicating decreased artifact presence with increased breathing cycles per scan location.Conclusion:The 4D CT oversampling acquisition with optimized sorting reduced artifact presence significantly and reproducibly compared to the phase‐sorted clinical acquisition.
SU‐C‐16A‐02: A Beryllium Oxide (BeO) Fibre‐Coupled Luminescence Dosimeter for High Dose Rate Brachytherapy
Authors: Santos A , Mohammadi M , Afshar V. S 
Published: July 2014

Purpose:Beryllium oxide (BeO) ceramics have an effective atomic number, zeff ∼7.1, closely matched to water, zeff ∼7.4. The purpose of this study was to evaluate the use of a beryllium oxide (BeO) ceramic fibrecoupled luminescence dosimeter, named RL/OSL BeO FOD, for high dose rate (HDR) brachytherapy dosimetry. In our dosimetry system the radioluminescence (RL) of BeO ceramics is utilized for dose‐rate measurements, and the optically stimulated luminescence (OSL) can be read post exposure for accumulated dose measurements.Methods:The RL/OSL BeO FOD consists of a 1 mm diameter × 1 mm long cylinder of BeO ceramic coupled to a 15 m long silica‐silica optical fibre. The optical fibre is connected to a custom developed portable RL and OSL reader, located outside of the treatment suite. The x‐ray energy response was evaluated using superficial x‐rays, an Ir‐192 source and high energy linear accelerators. The RL/OSL BeO FOD was then characterised for an Ir‐192 source, investigating the dose response and angular dependency. A depth dose curve for the Ir‐192 source was also measured.Results:The RL/OSL BeO FOD shows an under‐response at low energy x‐rays as expected. Though at higher x‐ray energies, the OSL response continued to increase, while the RL response remained relatively constant. The dose response for the RL is found to be linear up to doses of 15 Gy, while the OSL response becomes more supralinear to doses above 15 Gy. Little angular dependency is observed and the depth dose curve measured agreed within 4% of that calculated based on TG‐43.Conclusion:This works shows that the RL/OSL BeO FOD can be useful in HDR dosimetry. With the RL/OSL BeO FODs current size, it is capable of being inserted into intraluminal catheters and interstitial needles to verify HDR treatments.
SU‐C‐19A‐02: An Innovative Critical Organ Repositioner Device for Use During Radiotherapy Treatments
Authors: Parsai E , Elahinia M , Reddy K , Chen C 
Published: July 2014

Purpose:In most radiation oncology applications the use of shape memory alloy (SMA) actuation can be extremely beneficial in sparing normal structures by relocating them away from the path of the external beam, or placing distance between the structure and radiation source such as in Brachytherapy. Implementation of this organ repositioner device in conjunction with IMRT could open new possibilities for dose escalation and significant dose reduction to normal tissues. Similarly, in high dose rate brachytherapy applications, the ideal effective dose may not be delivered to the target volume due to toxicity concerns to adjacent critical structures. Here we present a dual functioning device manufactured from SMA materials to: 1) provide a desirable tool to reposition the organ at risk away from the radiation source, and 2) facilitate localization when imaging the area.Methods:A Nitinol based actuator with controlled force and displacement will be incorporated in the design of an organ repositioner (e.g., a rectal marker) with the ability to recall a pre‐defined shape at temperature T1 (body temp) and shift back to its original shape at temperature T2 (to facilitate removal). An open distal end permits the marker to function as a part of a barium delivery system.Results:An example of this SMA manufactured in our laboratory for atrial fibrillation radio frequency ablation is the esophagus SMA positioner, designed to position the esophagus away from the ablation area. This device shows the maximum strain in the deflected esophagus to be less than 3%. The prototype positioner deflected the organ at risk by 5 cm away from the site of ablation.Conclusions:The organ repositioner device is feasible for use in clinics, provides patient comfort due to its gradual deflection, and has dual functionality in repositioning the organ at risk as well as serving as a localization device.
SU‐C‐BRE‐05: PTV Margin Determination Based On Tumor Radiobiological Characteristics and Geometric Uncertainties Derived From Daily Cone‐ Beam CT Images
Authors: Selvaraj J 
Published: July 2014

Purpose:To determine required PTV margins for ≤1% loss in mean population TCP using systematic (Σ) and random (σ) errors calculated from daily cone‐beam CT (CBCT) images of head and neck patients.Methods:Daily CBCT images were acquired for 50 head and neck patients. The CBCT image sets acquired at each fraction were registered with planning CT to obtain positional errors for each patient for each fraction. Systematic and random errors were calculated from data collected for 50 patients as described in IPEM On Target report. CTV delineation uncertainty of 2mm is added quadratically to systematic error. Assuming a spherical target volume, the dose in each voxel of target volume is summed for each fraction in the treatment by shifting the dose grid to calculate mean population TCP inclusive of geometric uncertainties using a Monte Carlo method. These simulations were repeated for the set of Σ & σ in each axis for different PTV margins and drop in TCP for each margin are obtained. In order to study the effect of dose‐response curve on PTV margins, two different σα of 0.048 Gy‐1 and 0.218 Gy‐1 representing steep and shallow dose‐response curves are studied. Σ were 2.5, 2.5, 2.1 mm and σ were 0.3, 0.3 0.2 mm respectively in x, y and z axis respectively.Results:PTV margins based on tumor radiobiological characteristics are 4.8, 4.8 and 4 mm in x, y and z axis assuming 25 treatment fractions for σα 0.048 Gy‐1 (steep) and 4.2,4.2 and 2.2 for σα of 0.218 Gy‐1 (shallow). While the TCP‐based margins did not differ much in x and y axis, it is considerably smaller in z axis for shallow DRC.Conclusion:TCP based margins are substantially smaller than physical dose‐based margin recipes. This study also demonstrates the importance of considering tumor radiobiological characteristics while deriving margins.
SU‐C‐17A‐04: Distortion Characterization and Correction of MR‐SIM Images
Authors: Price R , Hearshen D , Wen N , Chetty I , Glide‐Hurst C 
Published: July 2014

Purpose:Distortions in MRI compromise spatial fidelity, potentially impacting delineation and dose calculation. We characterized 2D and 3D large field of view (FOV), system‐level distortion to implement correction maps for MR‐SIM treatment planning.Methods:For 2D in‐plane distortion characterization, a 36×43×2 cm3 phantom with 255 known landmarks (∼1 mm3) was scanned using 1.0T high‐field open MR‐SIM in the transverse, sagittal, and coronal axes (TE/TR/α = 30/500 ms/90°, voxel size =1.4×1.4×5mm3). A binary template (reference) was generated from phantom schematic. An automated program converted MR‐SIM images to binary via masking, thresholding, and testing for connectivity to identify landmarks. Distortion maps were generated by centroid mapping. Images were corrected via warping with inverse distortion maps. Temporal stability was assessed. 3D distortion was characterized using a 40×40×40 cm3 phantom (3D T1‐FFE, TE/TR/α= 3.83/9 ms/10°, voxel size=1 mm3) and performing B‐spline‐based deformable image registration to CT‐SIM (reference). Displacement vector fields describing vector distortion magnitude and distortion histograms were generated.Results:Over 9 months, B0‐field distortions (mm) were 0.51 ± 0.84 (maximum = 5.5), 0.18 ± 0.84 (maximum = 5.5), and 1.03 ± 0.50 (maximum = 3.6) in transverse, sagittal, and coronal planes, respectively. Maximum distortions occurred 18–24 cm from isocenter for all planes. After implementing correction maps, distortions (mm) were reduced to 0.14 ± 0.19 (maximum = 2.12), 0.01 ± 0.21 (maximum = 1.68), and 0.17 ± 0.21 (maximum = 3.00) in transverse, sagittal, and coronal planes, respectively. 3D vector distortion was 0.59 ± 0.32 mm (maximum = 1.65) within 5 cm of isocenter. Distortions were non‐negligible (mean = 1.57 ± 1.06 mm, maximum = 6.26), 10‐15 cm from isocenter.Conclusion:Assessment of 2D distortion was conducted, revealing the need to further correct the periphery of MR‐SIM images. Future work includes generating 3D corrections and quantifying objectinduced distortions to improve planning accuracy with MR‐SIM.Research supported in part by a grant from Philips HealthCare