bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐F‐J‐153: ACR MRI Phantom Test On a 1.5T MR‐Simulator with Flexible Coils Setting and Performance Comparison to Volumetric Head Coil Setting
Authors: Yuan J , Wong O , Cheung K , Yu S 
Published: July 2016

Purpose:To accommodate head‐and‐neck (HN) RT simulation scan with immobilization, sub‐optimized flexible radiofrequency coils have to be used on an MR‐sim rather than a volumetric head coil for diagnostic radiological (DR) applications. In this study, we present and compare ACR MRI phantom test with flexible coils setting (RT‐setting) and volumetric head coil setting (DR‐setting).Methods:Two 8‐channel array coils were wrapped close to an ACR MRI phantom placed on a flat couch‐top in RT‐setting for acquisition. ACR MRI phantom tests were conducted 10 times for each setting on a 1.5T MR‐sim. Sagittal localizer (TE/TR=20/200ms), axial T1 (TE/TR=20/500ms) and T2 scans (2TEs/TR=20,80/2000ms) were acquired (NEX=1). Acqusition and image analysis were conducted following ACR guidelines. Extra 10 RT‐setting acquisitions were obtained by enabling prescan normalization.Results:For RT‐setting without prescan normalization, all tests passed the ACR recommended criteria but image intensity uniformity. Geometric accuracy was 147.8±0.3mm and 191.0±0.4mm. Spatial resolution was 0.9mm. Slice thickness was 5.2mm±0.1mm (T1) and 5.1±0.1mm (T2). Slice position accuracy was 1.4±0.6mm, −2.2±0.3mm (T1), and 1.5±0.2mm, −2.2±0.2mm (T2). Image uniformity was 80.6%±2.6% (T1) and 80.2%±3.1% (T2) (criteria: ≥87.5% for 1.5T). Ghosting ratio was 0.0006±0.0004. Low contrast detectability was 30.7±1.7 (T1) and 22.6±3.0 (T2). Image uniformity (91.4%±4.2% and 91.8%±4.3%) and low contrast detectability (36.5±1.4 and 31.6±2.2) of DR‐setting were better than RT‐setting. Prescan normalization substantially improved image uniformity to 93.4%±0.2% and 93.4%±0.3%, but slightly compromised ghosting (0.0033±0.0004) and spatial resolution (0.9mm or 1.0mm) for RT‐setting.Conclusion:Flexible coils setting for HN‐RT simulation scan could successfully pass ACR criteria (prescan normalization enabled) and generally achieve comparable performance to volumetric coil setting, although compromise on low contrast detectability was observed probably due to the lower signal‐to‐noise ratio of the flexible coils. Our results could also serve as a reference baseline of high‐field MR‐sim QA performance under ACR guideline.
SU‐F‐J‐161: Prostate Contouring in Patients with Bilateral Hip Prostheses: Impact of Using Artifact‐Reduced CT Images and MRI
Authors: Elzibak A , Loblaw A , Morton G , Vesprini D , Liu S , Chung H , Davidson M 
Published: July 2016

Purpose:To investigate the usefulness of metal artifact reduction in CT images of patients with bilateral hip prostheses (BHP) for contouring the prostate and determine if the inclusion of MR images provides additional benefits.Methods:Five patients with BHP were CT scanned using our clinical protocol (140kV, 300mAs, 3mm slices, 1.5mm increment, Philips Medical Systems, OH). Images were reconstructed with the orthopaedic metal artifact reduction (O‐MAR) algorithm. MRI scanning was then performed (1.5T, GE Healthcare, WI) with a flat table‐top (T2‐weighted, inherent body coil, FRFSE, 3mm slices with 0mm gap). All images were transferred to Pinnacle (Version 9.2, Philips Medical Systems). For each patient, two data sets were produced: one containing the O‐MAR‐corrected CT images and another containing fused MRI and O‐MAR‐corrected CT images. Four genito‐urinary radiation oncologists contoured the prostate of each patient on the O‐MAR‐corrected CT data. Two weeks later, they contoured the prostate on the fused data set, blinded to all other contours. During each contouring session, the oncologists reported their confidence in the contours (1=very confident, 3=not confident) and the contouring difficulty that they experienced (1=really easy, 4=very challenging). Prostate volumes were computed from the contours and the conformity index was used to evaluate inter‐observer variability.Results:Larger prostate volumes were found on the O‐MAR‐corrected CT set than on the fused set (p< 0.05, median=36.9cm3 vs. 26.63 cm3). No significant differences were noted in the inter‐observer variability between the two data sets (p=0.3). Contouring difficulty decreased with the addition of MRI (p<0.05) while the radiation oncologists reported more confidence in their contours when MRI was fused with the O‐MAR‐corrected CT data (p<0.05).Conclusion:This preliminary work demonstrated that, while O‐MAR correction to CT images improves visualization of anatomy, the addition of MRI enhanced the oncologists’ confidence in contouring the prostate in patients with BHP.
SU‐F‐J‐168: Dosimetric Impact of MR Image Distortion in Treatment Planning
Authors: Yan Y , Yang J , Beddar S , Ibbott G , Balter P , Kudchadker R , Krishnan S , Fuller C , Wang J 
Published: July 2016

Purpose:To evaluate the dosimetric impact of MR image distortion in treatment planning.Methods:Based on the realistic MRI distortion measurement data from an integrated MRI‐Linac system, we created a generalized distortion model and applied it to CT images to simulate distorted MRI images. Ten patients with IMRT plans generated in Pinnacle treatment planning system in 5 anatomical cancer sites (lung, prostate, spinal cord, liver, and pancreas) were retrospectively selected for the simulation. The distortion model was applied to the planning CT image and contours. A distorted plan was created in Pinnacle for each patient. The dose‐volume‐histogram (DVH) of targets and critical structures were compared between the original and distorted plans. For a fair comparison, the same field sizes and intensity‐modulated radiation therapy (IMRT) parameters were used in generating the distorted plan.Results:The DVH of organs at risk (OARs) within a distance of 5cm to the imaging center did not show significant difference between the original and distorted plans. For certain OARs such as the spinal cord, the seminal vesicle (SV), and the larynx, with a distance greater than 5cm to the imaging center, larger deviations were observed between the distorted and original plans. The maximum mean dose difference was 1.92Gy (proximal SV, prescribed dose is 40Gy). Similar target coverage was observed between the distorted plans and the original plans for the 10 patients. One lung case had the maximum difference of the target mean dose between the original and distorted plans of 1.63Gy (prescribed dose is 72Gy).Conclusion:The MRI distortion did not lead to significant dosimetric difference compared to the original plans in most situations. However, OARs farther than 5cm from the imaging center showed larger dosimetric difference due to the distortion. Safety margin may need to account for the distortion in treatment planning.One of the authors receive cooperate funding from the Elekta.
SU‐F‐J‐169: A Feasibility Study of Using MRI Alone in Abdominal Radiotherapy
Authors: Zawisza I , Hsu S , Peng Q , Tome W 
Published: July 2016

Purpose:To demonstrate the feasibility of a MRI alone workflow to support treatment planning and image guidance for abdominal radiotherapy.Methods:Abdominal MR images (in‐phase/out‐phase/fat/water) were acquired for a patient with breath‐hold using a Dixon pulse sequence. Air masks were created on in‐phase images using intensity thresholding and morphological processing methods in order to separate air from bone. Pseudo‐CT and DRRs were generated using a published method. To investigate the effect of heterogeneity corrections on dose calculations using pseudo‐CT, three different plans (3‐field 3D, 5‐field IMRT and 2‐arc VMAT) were performed to mimic pancreatic treatments (1.8Gy/fraction over 28 fractions).Results:The DRRs created from pseudo‐CT were of comparable quality as those created from CT. Comparing dose calculations with and without heterogeneity corrections between the 3 different plans, the biggest dosimetric differences were seen in the VMAT plan where modulation must occur across air‐tissue interfaces such as those of the stomach and bowel. The DVHs for the VMAT plan showed ∼84cc difference at V50Gy in the small bowel. In terms of pseudo‐CT quality, some small volumes of air in the bowel and stomach were misclassified as bone. The VMAT plan was re‐optimized on pseudo‐CT with 0 HU in the misclassified areas. The V50Gy in the small bowel differed by ∼90cc between the new VMAT plan with and without heterogeneity corrections.Conclusion:We found that the use of MRI alone is feasible for abdominal treatment planning and image guidance. A difference between calculations with and without heterogeneity corrections was found that is most pronounced for VMAT where the traversal of air‐tissue interfaces is unavoidable. Future work will be performed to minimize misclassification between bone and air.
SU‐F‐J‐189: A Method to Improve the Spatial Resolution of Prompt Gamma Based Compton Imaging for Proton Range Verification
Authors: Draeger E , Mackin D , Peterson S , Chen H , Beddar S , Polf J 
Published: July 2016

Purpose:To test two new techniques, the distance‐of‐closest approach (DCA) and Compton line (CL) filters, developed as a means of improving the spatial resolution of Compton camera (CC) imaging.Methods:Gammas emitted from 22Na, 137Cs, and 60Co point sources were measured with a prototype 3‐stage CC. The energy deposited and position of each interaction in each stage were recorded and used to calculate a “cone‐of‐origin” for each gamma that scattered twice in the CC. A DCA filter was developed which finds the shortest distance from the gamma's cone‐of‐origin surface to the location of the gamma source. The DCA filter was applied to the data to determine the initial energy of the gamma and to remove “bad” interactions that only contribute noise to the image. Additionally, a CL filter, which removes gamma events that do not follow the theoretical predictions of the Compton scatter equation, was used to further remove “bad” interactions from the measured data. Then images were reconstructed with raw, unfiltered data, DCA filtered data, and DCA+CL filtered data and the achievable image resolution of each dataset was compared.Results:Spatial resolutions of ∼2 mm, and better than 2 mm, were achievable with the DCA and DCA+CL filtered data, respectively, compared to > 5 mm for the raw, unfiltered data.Conclusion:In many special cases in medical imaging where information about the source position may be known, such as proton radiotherapy range verification, the application of the DCA and CL filters can result in considerable improvements in the achievable spatial resolutions of Compton imaging.
SU‐F‐J‐192: A Quick and Effective Method to Validate Patient's Daily Setup and Geometry Changes Prior to Proton Treatment Delivery Based On Water Equivalent Thickness Projection Imaging (WETPI) for Head Neck Cancer (HNC) Patient
Authors: Liu G , Qin A , Zhang J , Li X , Zhou J , Yan D , Teo B , Chen P , Krauss D , Kabolizadeh P , Guerrero T , Stevens C , Liang J , Ding X 
Published: July 2016

Purpose:With the implementation of Cone‐beam Computed‐Tomography (CBCT) in proton treatment, we introduces a quick and effective tool to verify the patient's daily setup and geometry changes based on the Water‐Equivalent‐Thickness Projection‐Image(WETPI) from individual beam angle.Methods:A bilateral head neck cancer(HNC) patient previously treated via VMAT was used in this study. The patient received 35 daily CBCT during the whole treatment and there is no significant weight change. The CT numbers of daily CBCTs were corrected by mapping the CT numbers from simulation CT via Deformable Image Registration(DIR). IMPT plan was generated using 4‐field IMPT robust optimization (3.5% range and 3mm setup uncertainties) with beam angle 60, 135, 300, 225 degree. WETPI within CTV through all beam directions were calculated. 3%/3mm gamma index(GI) were used to provide a quantitative comparison between initial sim‐CT and mapped daily CBCT. To simulate an extreme case where human error is involved, a couch bar was manually inserted in front of beam angle 225 degree of one CBCT. WETPI was compared in this scenario.Results:The average of GI passing rate of this patient from different beam angles throughout the treatment course is 91.5 ± 8.6. In the cases with low passing rate, it was found that the difference between shoulder and neck angle as well as the head rest often causes major deviation. This indicates that the most challenge in treating HNC is the setup around neck area. In the extreme case where a couch bar is accidently inserted in the beam line, GI passing rate drops to 52 from 95.Conclusion:WETPI and quantitative gamma analysis give clinicians, therapists and physicists a quick feedback of the patient's setup accuracy or geometry changes. The tool could effectively avoid some human errors. Furthermore, this tool could be used potentially as an initial signal to trigger plan adaptation.
SU‐F‐J‐207: Non‐Small Cell Lung Cancer Patient Survival Prediction with Quantitative Tumor Textures Analysis in Baseline CT
Authors: Wu Y , Zou J , Murillo P , Nosher J , Amorosa J , Bramwit M , Yue N , Jabbour S , Foran D 
Published: July 2016

Purpose:Chemo‐radiation therapy (CRT) is widely used in treating patients with locally advanced non‐small cell lung cancer (NSCLC). Determination of the likelihood of patient response to treatment and optimization of treatment regime is of clinical significance. Up to date, no imaging biomarker has reliably correlated to NSCLC patient survival rate. This pilot study is to extract CT texture information from tumor regions for patient survival prediction.Methods:Thirteen patients with stage II‐III NSCLC were treated using CRT with a median dose of 6210 cGy. Non‐contrast‐enhanced CT images were acquired for treatment planning and retrospectively collected for this study. Texture analysis was applied in segmented tumor regions using the Local Binary Pattern method (LBP). By comparing its HU with neighboring voxels, the LBPs of a voxel were measured in multiple scales with different group radiuses and numbers of neighbors. The LBP histograms formed a multi‐dimensional texture vector for each patient, which was then used to establish and test a Support Vector Machine (SVM) model to predict patients’ one year survival. The leave‐one‐out cross validation strategy was used recursively to enlarge the training set and derive a reliable predictor. The predictions were compared with the true clinical outcomes.Results:A 10‐dimensional LBP histogram was extracted from 3D segmented tumor region for each of the 13 patients. Using the SVM model with the leave‐one‐out strategy, only 1 out of 13 patients was misclassified. The experiments showed an accuracy of 93%, sensitivity of 100%, and specificity of 86%.Conclusion:Within the framework of a Support Vector Machine based model, the Local Binary Pattern method is able to extract a quantitative imaging biomarker in the prediction of NSCLC patient survival. More patients are to be included in the study.
SU‐F‐J‐209: Quantification of Image‐Guidance Benefit in Image‐Guided Radiotherapy of Cancers
Authors: Zhou L , Deng J 
Published: July 2016

Purpose:Image‐guidance has been widely used in radiation oncology for accurate radiotherapy. The goal of this study is to quantify the benefit of image‐guidance in image‐guided radiotherapy (IGRT) of cancers.Methods:In this study, a new index termed image‐guidance benefit (IGB), was proposed to quantify the benefit of image‐guidance in cancer radiotherapy. It is calculated as a ratio of the square sum of dose differences between planning dose matrix and actual delivery dose matrix post image‐guidance to the square sum of dose summation between the two matrixes, summing over all dose scoring voxels. Ranging from 0 to 1, larger IGB values indicate larger benefit out of image‐guidance. With IRB approval, the DICOM RT files and 3D couch shifts applied during IGRT of 2219 patients were collected, based on which patient‐specific IGB values were calculated with an in‐house MATLAB code.Results:In this study, the mean IGB value was found to be 0.0398 (0.000583–0.999) with a positive correlation between IGB value and 3D couch shift vector at 0.0435 per cm (P<0.0001). With 2 mm shift as a threshold above which an image‐guidance is deemed clinically necessary, the corresponding mean IGB value was 0.00457, much less than 0.0398 (P<0.001). However, the IGB values of 56 cases based on couch shifts were less than those based on 2 mm shift.Conclusion:The IGB values were patient‐specific and site‐dependent. Using 2 mm shifts as criterion for applying image‐guidance, the applied image‐guidance procedures were found clinically necessary and highly beneficial in 97.5% of cancer patients. However, image‐guidance procedures were found over‐used in about 2.5% of cancer patients in our current practices of IGRT, which should be avoided as they added no benefit in improving delivery accuracy while increasing cancer risk.
SU‐F‐J‐227: Accuracy of Passive Magnetic Ultrasound Needle Guidance in High‐ Fidelity Conventional and Novel Simulated Block Approach Phantoms
Authors: Johnson A 
Published: July 2016

Purpose:The objective of this research was to demonstrate accuracy of a real‐time passive ultrasound magnetic needle guidance technology (NGT) and target localization algorithm using conventional anechogenic contact phantoms and a novel fluid‐filled hyperechogenic phantom simulating nerve block technique.Methods:Accuracy (mm to phantom target) was assessed by observing 35 medical practitioners (16 anesthesiologists and 19 residents) performing 560 needle procedures in high‐fidelity ex vivo porcine tissue phantoms. Each practitioner performed 8 tasks with GE Venue 50 magnetic NGT system with PinPoint GT (Bard Access Sys.) and 8 conventional echogenic needle (control) procedures under various conditions (#18/#22 needle gauge, IP/OOP approach, and hyperechogenic simulated block approach targets or anechogenic solid targets). Passes, user feedback, and ergonomics were also assessed.Results:Overlaid visual aids produced in real time (<300 mS delay) by NGT enabled users to consistently perform with better accuracy than control echogenic needle guidance. Accuracy improved by 51.2% at 95% CI [29.8%, 66.7%] (P = 0.0008) among block approach phantoms and 51.4% at 95% CI [34.9%, 64.0%] (P < 0.0001) among placement phantoms. Further, inadvertent contact with targets was reduced by NGT visualizations versus controls in both anesthesiologists (0 vs. 8 contacts; accuracy 2.0±1.7 vs. 4.13±6.7 mm) and novice users (3 vs. 12 contacts; accuracy 2.2±2.3 vs. 2.9±3.7 mm), respectively. Among novice users, NGT visualizations notably reduced quality‐compromising ergonomic observations compared to controls under equivalent conditions.Conclusion:NGT systems employing magnetic field generation and electromagnetic sensors to track needle position and orientation relative to a sonoanatomical target within a magnetic field have the potential to enable greater accuracy for complex needle placements and reduce unintentional needle contact, particularly in novice users. Further, NGT visualizations of needle tip and projected trajectory contribute to positive ergonomics and reducing quality‐compromising behaviors among operators, potentially reducing fatigue and needle progression error.This work was supported by funding provided by the GE Healthcare Ultrasound Business, Milwaukee, WI.
SU‐F‐T‐07: Dosimetric Impact of the Dwell Position Inaccuracy in HDR Ring and Tandem Treatments with VarisourceIX Afterloader
Authors: Veltchev I , Price R , Anderson P , Ma C 
Published: July 2016

Purpose:The dwell positions in the VariSourceIX HDR ring applicator are known to be somewhat inaccurate with observed deviations from the planned position of up to 5mm. The details of how to correct this issue are suggested by the vendor and the dosimetric impact on volumetric HDR plans varies from patient to patient. In this study we present our experience with correcting this issue, and discuss the impact on plan quality if the planned dwell positions were left unchanged.Methods:A 60 degree ring was characterized using gafchromic film with the applicator in treatment orientation. The offsets as a function of dwell position in the ring were deduced. The variability in each observed dwell position was determined from three consecutive runs. A total of 10 ring and tandem treatments were analyzed in this work. The PTV and organs at risk were outlined and dose‐volume histograms were produced. The patient plans were modified for delivery according to the average shift determined in the characterization stage. D2cc for the organs at risk (rectum, bladder, and sigmoid) were used as dosimetric end‐points in this study. The dose at the locations of the ICRU points A was analyzed as well.Results:Each dwell position was corrected according to the measured offsets. For each fraction, three plans were produced: dosimetric plan with ideal dwell positions, treatment plan with corrected dwell positions, and a test plan with opposite offsets for evaluation of dose differences for organs at risk and PTV. Maximum and average dose deviations were deduced for each organ at risk. For rectum, sigmoid, and bladder the maximum D2cc dose deviations were 7.6%, 5.3%, and 1.5%, respectively.Conclusion:Correcting dwell position inaccuracy in an HDR ring is essential for maintaining quality of treatment. The dose differences are significant in the organs at risk.
SU‐F‐T‐08: Brachytherapy Film Dosimetry in a Water Phantom for a Ring and Tandem HDR Applicator
Authors: Lee B , Grelewicz Z , Kang Z , Cutright D , Gopalakrishnan M , Sathiaseelan V , Zhang H 
Published: July 2016

Purpose:The feasibility of dose measurement using new generation EBT3 film was explored in a water phantom for a ring and tandem HDR applicator for measurements tracking mucosal dose during cervical brachytherapy.Methods:An experimental fixture was assembled to position the applicator in a water phantom. Prior to measurement, calibration curves for EBT3 film in water and in solidwater were verified. EBT3 film was placed at different known locations around the applicator in the water tank. A CT scan of the phantom with applicator was performed using clinical protocol. A typical cervical cancer treatment plan was then generated by Oncentra brachytherapy planning system. A dose of 500 cGy was prescribed to point A (2 cm, 2 cm). Locations measured by film included the outer surface of the ring, measurement point A_m (2.2 cm, 2.2 cm), and profiles extending from point A_m parallel to the tandem. Three independent measurements were conducted. The doses recorded by film were carefully analyzed and compared with values calculated by the treatment planning system.Results:Assessment of the EBT3 films indicate that the dose at point A matches the values predicted by the planning system. Dose to the point A_m was 411.5 cGy, and the outer circumferential surface dose of the ring was between 500 and 1150 cGy. It was found that from the point A_m, the dose drops 60% within 4.5 cm on the line parallel to the tandem. The measurement doses agree with the treatment planning system.Conclusion:Use of EBT3 film is feasible for in‐water measurements for brachytherapy. A carefully machined apparatus will likely improve measurement accuracy. In a typical plan, our study found that the ring surface dose can be 2.5 times larger than the point A prescription dose. EBT3 film can be used to monitor mucosal dose in brachytherapy treatments.