bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐E‐J‐227: Evaluation of Residual Geometric Distortion in MRI for Treatment Planning
Authors: Wang J , Yang J , Hwang K , Wen Z , Court L , Ibbott G 
Published: June 2015

Purpose:To determine an appropriate model to simulate system related geometric distortions in MR images in order to investigate the dosimetric impact on MRI‐LINAC treatment planning.Methods:Two sets of geometric distortion data in 3D volume were obtained independently from two different MRI vendors using different geometric distortion phantoms with visible markers. The distortion data were used to train two parametric models in X, Y, and Z directions separately: a second order polynomial model and a spherical harmonic model. The polynomial model was constructed in 2D slices with available measurements while the spherical harmonic model was built in 3D. After the models were created, they were used to generate simulated distortions at the marker positions to be compared with the measured data for evaluation.Results:The maximum measured distortions (after standard distortion corrections) were at the border of the scan, with 6.9 mm, 6.1 mm, and 3.6 mm in the X, Y, Z (slice) direction for first dataset, and 21.7 mm, 4.0 mm, and 12.0 mm for second dataset, respectively. For the first dataset, the polynomial model had average simulation errors in X, Y, and Z of 0.4±0.4 mm, 0.2±0.2 mm, and 0.1±0.2 mm, contrasting with those from the spherical harmonic model of 0.5±0.7 mm, 0.4±0.4 mm, and 0.6±0.4 mm. For the second dataset, the polynomial model had average simulation errors of 1.4±1.8 mm, 0.3±0.3 mm, and 0.4±0.5 mm, contrasting with those from the spherical harmonic model of 2.8±3.2 mm, 0.6±0.5 mm, and 2.5±2.1 mm. We found that using a maximum order of 2 in the spherical harmonic model gave the best estimation of the distortion.Conclusion:Polynomial model showed a better simulation of the residual geometric distortion than spherical harmonic model and may be a better choice to model the residual MR image distortion for MRI‐LINAC treatment planning purposes.This work was partially supported by a research grant from Elekta.
SU‐E‐J‐231: Comparison of Delineation Variability of Soft Tissue Volume and Position in Head‐And‐Neck Between Two T1‐Weighted Pulse Sequences Using An MR‐Simulator with Immobilization
Authors: Wong O , Lo G , Yuan J , Law M , Ding A , Cheng K , Chan K , Cheung K , Yu S 
Published: June 2015

Purpose:There is growing interests in applying MR‐simulator(MR‐sim) in radiotherapy but MR images subject to hardware, patient and pulse sequence dependent geometric distortion that may potentially influence target definition. This study aimed to evaluate the influence on head‐and‐neck tissue delineation, in terms of positional and volumetric variability, of two T1‐weighted(T1w) MR sequences on a 1.5T MR‐simMethods:Four healthy volunteers were scanned (4 scans for each on different days) using both spin‐echo (3DCUBE, TR/TE=500/14ms, TA=183s) and gradient‐echo sequences (3DFSPGR, TE/TR=7/4ms, TA=173s) with identical coverage, voxel‐size(0.8×0.8×1.0mm3), receiver‐bandwidth(62.5kHz/pix) and geometric correction on a 1.5T MR‐sim immobilized with personalized thermoplastic cast and head‐rest. Under this setting, similar T1w contrast and signal‐to‐noise ratio were obtained, and factors other than sequence that might bias image distortion and tissue delineation were minimized. VOIs of parotid gland(PGR, PGL), pituitary gland(PIT) and eyeballs(EyeL, EyeR) were carefully drawn, and inter‐scan coefficient‐of‐variation(CV) of VOI centroid position and volume were calculated for each subject. Mean and standard deviation(SD) of the CVs for four subjects were compared between sequences using Wilcoxon ranksum test.Results:The mean positional(<4%) and volumetric(<7%) CVs varied between tissues, majorly dependent on tissue inherent properties like volume, location, mobility and deformability. Smaller mean volumetric CV was found in 3DCUBE, probably due to its less proneness to tissue susceptibility, but only PGL showed significant difference(P<0.05). Positional CVs had no significant differences for all VOIs(P>0.05) between sequences, suggesting volumetric variation might be more sensitive to sequence‐dependent delineation difference.Conclusion:Although 3DCUBE is considered less prone to tissue susceptibility‐induced artifact and distortion, our preliminary data showed that both sequences had insignificant differences on positional and volumetric CV in most head‐and‐neck tissues except for PGL. This study is majorly limited in its small sample size. Influences of image contrasts(T1w v.s. T2w) and inter‐observer difference have to be further investigated.
SU‐E‐J‐236: Audiovisual Biofeedback Improves Breath‐Hold Lung Tumor Position Reproducibility Measured with 4D MRI
Authors: Lee D , Greer P , Lapuz C , Ludbrook J , Pollock S , Kim T , Keall P 
Published: June 2015

Purpose:Audiovisual biofeedback breath‐hold (AVBH) was employed to reproduce tumor position on inhale and exhale breath‐holds for 4D tumor information. We hypothesize that lung tumor position will be more consistent using AVBH compared with conventional breath‐hold (CBH).Methods:Lung tumor positions were determined for seven lung cancer patients (age: 25 – 74) during to two separate 3T MRI sessions. A breathhold training session was performed prior to the MRI sessions to allow patients to become comfortable with AVBH and their exhale and inhale target positions. CBH and AVBH 4D image datasets were obtained in the first MRI session (pre‐treatment) and the second MRI session (midtreatment) within six weeks of the first session. Audio‐instruction (MRI: Siemens Skyra) in CBH and verbal‐instruction (radiographer) in AVBH were used. A radiation oncologist contoured the lung tumor using Eclipse (Varian Medical Systems); tumor position was quantified as the centroid of the contoured tumor after rigid registration based on vertebral anatomy across two MRI sessions. CBH and AVBH were compared in terms of the reproducibility assessed via (1) the difference between the two exhale positions for the two sessions and the two inhale positions for the sessions. (2) The difference in amplitude (exhale to inhale) between the two sessions.Results:Compared to CBH, AVBH improved the reproducibility of two exhale (or inhale) lung tumor positions relative to each other by 33%, from 6.4±5.3 mm to 4.3±3.0 mm (p=0.005). Compared to CBH, AVBH improved the reproducibility of exhale and inhale amplitude by 66%, from 5.6±5.9 mm to 1.9±1.4 mm (p=0.005).Conclusions:This study demonstrated that audiovisual biofeedback can be utilized for improving the reproducibility of breath‐hold lung tumor position. These results are advantageous towards achieving more accurate emerging radiation treatment planning methods, in addition to imaging and treatment modalities utilizing breath‐hold procedures.
SU‐E‐J‐243: Reproducibility of Radiomics Features Through Different Voxel Discretization Levels in F18‐FDG PET Images of Cervical Cancer
Authors: Altazi B , Fernandez D , Zhang G , Biagioli M , Moros E , Moffitt H. Lee 
Published: June 2015

Purpose:Site‐specific investigations of the role of Radiomics in cancer diagnosis and therapy are needed. We report of the reproducibility of quantitative image features over different discrete voxel levels in PET/CT images of cervical cancer.Methods:Our dataset consisted of the pretreatment PET/CT scans from a cohort of 76 patients diagnosed with cervical cancer, FIGO stage IB‐IVA, age range 31–76 years, treated with external beam radiation therapy to a dose range between 45–50.4 Gy (median dose: 45 Gy), concurrent cisplatin chemotherapy and MRI‐based Brachytherapy to a dose of 20–30 Gy (median total dose: 28 Gy). Two board certified radiation oncologists delineated Metabolic Tumor volume (MTV) for each patient. Radiomics features were extracted based on 32, 64, 128 and 256 discretization levels (DL). The 64 level was chosen to be the reference DL. Features were calculated based on Co‐occurrence (COM), Gray Level Size Zone (GLSZM) and Run‐Length (RLM) matrices. Mean Percentage Differences (Δ) of features for discrete levels were determined. Normality distribution of Δ was tested using Kolomogorov ‐ Smirnov test. Bland‐Altman test was used to investigate differences between feature values measured on different DL. The mean, standard deviation and upper/lower value limits for each pair of DL were calculated. Interclass Correlation Coefficient (ICC) analysis was performed to examine the reliability of repeated measures within the context of the test re‐test format.Results:3 global and 5 regional features out of 48 features showed distribution not significantly different from a normal one. The reproducible features passed the normality test. Only 5 reproducible results were reliable, ICC range 0.7 – 0.99.Conclusion:Most of the radiomics features tested showed sensitivity to voxel level discretization between (32 – 256). Only 4 GLSZM, 3 COM and 1 RLM showed insensitivity towards mentioned discrete levels.
SU‐E‐J‐245: Sensitivity of FDG PET Feature Analysis in Multi‐Plane Vs. Single‐Plane Extraction
Authors: Harmon S , Galavis P , Jeraj R 
Published: June 2015

Purpose:Sensitivity of PET‐derived texture features to reconstruction methods has been reported for features extracted from axial planes; however, studies often utilize three dimensional techniques. This work aims to quantify the impact of multi‐plane (3D) vs. single‐plane (2D) feature extraction on radiomics‐based analysis, including sensitivity to reconstruction parameters and potential loss of spatial information.Methods:Twenty‐three patients with solid tumors underwent [18F]FDG PET/CT scans under identical protocols. PET data were reconstructed using five sets of reconstruction parameters. Tumors were segmented using an automatic, in‐house algorithm robust to reconstruction variations. 50 texture features were extracted using two Methods: 2D patches along axial planes and 3D patches. For each method, sensitivity of features to reconstruction parameters was calculated as percent difference relative to the average value across reconstructions. Correlations between feature values were compared when using 2D and 3D extraction.Results:21/50 features showed significantly different sensitivity to reconstruction parameters when extracted in 2D vs 3D (wilcoxon α<0.05), assessed by overall range of variation, Rangevar(%). Eleven showed greater sensitivity to reconstruction in 2D extraction, primarily first‐order and co‐occurrence features (average Rangevar increase 83%). The remaining ten showed higher variation in 3D extraction (average Rangevarincrease 27%), mainly co‐occurence and greylevel run‐length features. Correlation of feature value extracted in 2D and feature value extracted in 3D was poor (R<0.5) in 12/50 features, including eight co‐occurrence features. Feature‐to‐feature correlations in 2D were marginally higher than 3D, ∣R∣>0.8 in 16% and 13% of all feature combinations, respectively. Larger sensitivity to reconstruction parameters were seen for inter‐feature correlation in 2D(σ=6%) than 3D (σ<1%) extraction.Conclusion:Sensitivity and correlation of various texture features were shown to significantly differ between 2D and 3D extraction. Additionally, inter‐feature correlations were more sensitive to reconstruction variation using single‐plane extraction. This work highlights a need for standardized feature extraction/selection techniques in radiomics.
SU‐E‐J‐263: Repeatability of SUV and Texture Parameters in Serial PET Studies
Authors: Schwartz J , Humm J , Nehmeh S , Schoder H 
Published: June 2015

Purpose:Standardized uptake values (SUV) are standard quantitative PET measures of FDG tumor uptake used,and are used as a tool to monitor response to therapy. Textural analysis is emerging as a new tool for assessing intratumoral heterogeneity which may allow better tissue characterization and improved prediction of response and survival rate.Understanding what variations may be expected in these parameters is key in order to make decisions based on how the change throughout the course of treatment. The aim of this study was to assess repeatability in SUV measures and texture parameters,and establish criteria that differentiate changes associated with treatment rather than statistical variability.Methods:Eighty patients,167 random lesions total,were scanned in a GE Discovery STE PET/CT Scanner. One field‐of‐view was chosen centered on the largest lesion observed in a clinical whole‐body FDG PET.Immediately following,a gated 9 min scan was acquired in list mode,without changing the patient's position between any scans. Data was replayed into 3 time bins,3 min each,in order to insure equivalent noise characteristics in each replicate.Data was reconstructed into 128×128×47 square matrices.One VOI was drawn over each lesion for each patient and used to segment all 3 replicates. The mean.max and peak SUV were calculated for each VOI and replicate. First‐order textural features were also calculated (skewness and kurtosis). Repeatability was calculated as the average standard deviation over the mean for the 3 repeated measurements for each lesion.Results:The average percent error in the SUV max,peak and mean were 3.4%(0– 12.9%),1.9% (0–7.5%),2.8% (0–12.2%),respectively.For skewness and kurtosis they were 10.9% and 17.8%.Conclusion:We have shown that there is a large variation in %error in SUV measures across patients. SUVpeak is the least variable and kurtosis and skewness parameters are less reliable thatn SUVs.Higher order textures are be
SU‐E‐T‐05: 4D Measurement‐Guided Dose Reconstruction (4D‐MGDR) in End‐End Quality Assurance (E2E QA) for Assessing Safety Margin in Radiosurgery (SRS) From Clinical Perspectives
Authors: Chan M , Leung R , Wong M , Lee V , Law G , Lee K , Tung S , Blanck O 
Published: June 2015

Purpose:To assess the plan robustness and safety margin in SRS from 4DMGDR in E2E QA based on clinical objectives.Methods:OCTAVIUS SRS 1000 detector array and 4D phantom (PTW, Freiburg, Germany) were used to measure 5 coplanar SRS plans with 1 and 2 mm planning target volume (PTV). 3 targets were clinical, and 2 were virtual simulated to be 1mm from the brainstem (BS), and between chiasm (CS) and optic nerve (ON). Planning was done on Monaco v5.0 (Elekta, Maryland Heights, MO) to achieve 95–99% PTV and 100% gross tumor volume (GTV) prescription dose coverage. CBCT setup of the 4D phantom by 6D robotic couch was performed as for real patient. 4D‐MGDR in patient CT and dosimetric analysis were performed in PTW Verisoft v6.1. The safety margin that achieved 100% GTV coverage was determined, and doses to 2% (D2%) of BS, ON and CS were assessed from E2E QA.Results:100% GTV coverage was achieved with 1mm margin for 2 plans and 2mm margin for all plans. 98.3% and 99.4% GTV coverage were found in E2E QA for 1mm PTVs that either had sharp changing contour, or was nearby CS and ON or BS, and had either low planned minimum GTV dose (∼101% of the prescribed dose vs.∼106%) or compromised PTV coverage (95% vs. 99%). D2% to CS obtained with 4D‐MGDR for one virtual target were 18.8Gy for 1mm PTV and 19.2Gy for 2mm PTV, exceeding the planned tolerance of 18Gy/3 fractions for prescription dose of 24Gy.Conclusion:1mm margin is generally sufficient for dose planning and machine delivery errors. Irregular GTV with just enough dose coverage to spare critical organs may need 2mm margin at the costs of possible higher organ doses. 4D MGDR in an E2E QA approach can put the treatment plan evaluation in clinical perspectives.
SU‐E‐T‐21: A D‐D Based Neutron Generator System for Boron Neutron Capture Therapy: A Feasibility Study
Authors: Hsieh M , Liu Y , Nie L 
Published: June 2015

Purpose:To investigate the feasibility of a deuterium‐deuterium (DD) neutron generator for application in boron neutron capture therapy (BNCT) of brain cancerMethods:MCNP simulations were performed using a head phantom and a monoenergetic neutron source, which resembles the point source in a DD generator that emits 2.45‐MeV neutrons. Source energies ranging from 5eV to 2.45MeV were simulated to determine the optimal treatment energy. The phantom consisted of soft tissue, brain tissue, skull, skin layer, and a brain tumor of 5 cm in diameter. Tumor depth was varied from 5–10 cm. Boron‐10 concentrations of 10 ppm, 15 ppm, and 30 ppm were used in the soft/brain tissues, skin, and tumor, respectively. The neutron flux required to deliver 60 Gy to the tumor as well as the normal tissue doses were determined.Results:Beam energies between 5eV and 10keV obtained doses with the highest dose ratios (3.3–25.9) between the tumor and the brain at various depths. The dose ratio with 2.45‐MeV neutrons ranged from 0.8–6.6. To achieve the desired tumor dose in 40 minutes, the required neutron flux for a DD generator was between 8.8E10 and 5.2E11 n/s and the resulting brain dose was between 2.3 and 18 Gy, depending on the tumor depth. The skin and soft tissue doses were within acceptable tolerances. The boron‐neutron interaction accounted for 54–58% of the total dose.Conclusion:This study shows that the DD neutron generator can be a feasible neutron source for BNCT. The required neutron flux for treatment is achievable with the current DD neutron technology. With a well‐designed beam shaping assembly and treatment geometry, the neutron flux can be further improved and a 60‐Gy prescription can be accurately delivered to the target while maintaining tolerable normal tissue doses. Further experimental studies will be developed and conducted to validate the simulation results.
SU‐E‐T‐32: A Feasibility Study of Independent Dose Verification for IMAT
Authors: Kamima T , Takahashi R , Baba H , Yamashita M , Sugawara Y , Sato Y , Tachibana H 
Published: June 2015

Purpose:To assess the feasibility of the independent dose verification (Indp) for intensity modulated arc therapy (IMAT).Methods:An independent dose calculation software program (Simple MU Analysis, Triangle Products, JP) was used in this study, which can compute the radiological path length from the surface to the reference point for each control point using patient's CT image dataset and the MLC aperture shape was simultaneously modeled in reference to the information of MLC from DICOM‐RT plan. Dose calculation was performed using a modified Clarkson method considering MLC transmission and dosimetric leaf gap. In this study, a retrospective analysis was conducted in which IMAT plans from 120 patients of the two sites (prostate / head and neck) from four institutes were retrospectively analyzed to compare the Indp to the TPS using patient CT images. In addition, an ion‐chamber measurement was performed to verify the accuracy of the TPS and the Indp in water‐equivalent phantom.Results:The agreements between the Indp and the TPS (mean±1SD) were −0.8±2.4% and −1.3±3.8% for the regions of prostate and head and neck, respectively. The measurement comparison showed similar results (−0.8±1.6% and 0.1±4.6% for prostate and head and neck). The variation was larger in the head and neck because the number of the segments was increased that the reference point was under the MLC and the modified Clarkson method cannot consider the smooth falloff of the leaf penumbra.Conclusion:The independent verification program would be practical and effective for secondary check for IMAT with the sufficient accuracy in the measurement and CT‐based calculation. The accuracy would be improved if considering the falloff of the leaf penumbra.
SU‐E‐T‐33: A Feasibility‐Seeking Algorithm Applied to Planning of Intensity Modulated Proton Therapy: A Proof of Principle Study
Authors: Penfold S , Casiraghi M , Dou T , Schulte R , Censor Y 
Published: June 2015

Purpose:To investigate the applicability of feasibility‐seeking cyclic orthogonal projections to the field of intensity modulated proton therapy (IMPT) inverse planning. Feasibility of constraints only, as opposed to optimization of a merit function, is less demanding algorithmically and holds a promise of parallel computations capability with non‐cyclic orthogonal projections algorithms such as string‐averaging or block‐iterative strategies.Methods:A virtual 2D geometry was designed containing a C‐shaped planning target volume (PTV) surrounding an organ at risk (OAR). The geometry was pixelized into 1 mm pixels. Four beams containing a subset of proton pencil beams were simulated in Geant4 to provide the system matrix A whose elements a_ij correspond to the dose delivered to pixel i by a unit intensity pencil beam j. A cyclic orthogonal projections algorithm was applied with the goal of finding a pencil beam intensity distribution that would meet the following dose requirements: D_OAR < 54 Gy and 57 Gy < D_PTV < 64.2 Gy. The cyclic algorithm was based on the concept of orthogonal projections onto half‐spaces according to the Agmon‐Motzkin‐Schoenberg algorithm, also known as ‘ART for inequalities’.Results:The cyclic orthogonal projections algorithm resulted in less than 5% of the PTV pixels and less than 1% of OAR pixels violating their dose constraints, respectively. Because of the abutting OAR‐PTV geometry and the realistic modelling of the pencil beam penumbra, complete satisfaction of the dose objectives was not achieved, although this would be a clinically acceptable plan for a meningioma abutting the brainstem, for example.Conclusion:The cyclic orthogonal projections algorithm was demonstrated to be an effective tool for inverse IMPT planning in the 2D test geometry described. We plan to further develop this linear algorithm to be capable of incorporating dose‐volume constraints into the feasibility‐seeking algorithm.
SU‐E‐T‐34: A Feasible Action Level System for DVH‐Based IMRT QA
Authors: Redler G , Zhen H 
Published: June 2015

Purpose:Gamma‐based IMRT QA metrics have been shown to inadequately predict clinically relevant patient dose errors. In this study, we develop and evaluate an intuitive and feasible DVH‐based IMRT QA action level system, which incorporates both physical and clinical considerations.Methods:VMAT plans from previously treated prostate (n=11) and brain (n=13) patients are analyzed. Treatment plans were created using Eclipse TPS and delivered using Varian's Trilogy linac. Initial IMRT QA was performed using the ArcCHECK phantom. All plans passed gamma‐based criteria (3%/3mm) with at least a 97% passing rate. To design and test the feasibility of the DVH‐based IMRT QA metric, 3DVH software is used to process the QA data from the ArcCHECK measurement and predict the 3D distribution of dose delivered to the patient. This enables comparison of a standard set of clinically important DVH values between TPS calculations and that predicted by the QA process. A two‐level system is implemented to determine the IMRT QA Result. Level 1 requires that QA predicted DVH values for the PTV and OARs fall within a physical tolerance generated by scaling the original planned dose uniformly by ±5%. If level 1 tolerance is exceeded, level 2 requires that the QA‐predicted DVH values are within institutional normal tissue tolerances. OARs for prostate cases include bladder and rectum. OARs for brain cases include the lens, optic nerve, optic chiasm, and brainstem.Results:All analyzed QAs passed the proposed action levels, with prostate cases all satisfying physical tolerances. Ten brain cases had DVH values failing physical tolerances, but satisfying clinical tolerances. All DVHs failing physical tolerances are in low dose region.Conclusion:The proposed IMRT QA metrics represents a straightforward alternative to the gamma‐based metric. It has the potential to better address both physical and clinical concerns that are specific to individual patients.