bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐E‐J‐221: A Novel Expansion Method for MRI Based Target Delineation in Prostate Radiotherapy
Authors: Ruiz B , Feng Y , Shores R , Fung C 
Published: June 2015

Purpose:To compare a novel bladder/rectum carveout expansion method on MRI delineated prostate to standard CT and expansion based methods for maintaining prostate coverage while providing superior bladder and rectal sparing.Methods:Ten prostate cases were planned to include four trials: MRI vs CT delineated prostate/proximal seminal vesicles, and each image modality compared to both standard expansions (8mm 3D expansion and 5mm posterior, i.e. ∼8mm) and carveout method expansions (5mm 3D expansion, 4mm posterior for GTV‐CTV excluding expansion into bladder/rectum followed by additional 5mm 3D expansion to PTV, i.e. ∼1cm). All trials were planned to total dose 7920 cGy via IMRT. Evaluation and comparison was made using the following criteria: QUANTEC constraints for bladder/rectum including analysis of low dose regions, changes in PTV volume, total control points, and maximum hot spot.Results:∼8mm MRI expansion consistently produced the most optimal plan with lowest total control points and best bladder/rectum sparing. However, this scheme had the smallest prostate (average 22.9% reduction) and subsequent PTV volume, consistent with prior literature. ∼1cm MRI had an average PTV volume comparable to ∼8mm CT at 3.79% difference. Bladder QUANTEC constraints were on average less for the ∼1cm MRI as compared to the ∼8mm CT and observed as statistically significant with 2.64% reduction in V65. Rectal constraints appeared to follow the same trend. Case‐by‐case analysis showed variation in rectal V30 with MRI delineated prostate being most favorable regardless of expansion type. ∼1cm MRI and ∼8mm CT had comparable plan quality.Conclusion:MRI delineated prostate with standard expansions had the smallest PTV leading to margins that may be too tight. Bladder/rectum carveout expansion method on MRI delineated prostate was found to be superior to standard CT based methods in terms of bladder and rectal sparing while maintaining prostate coverage. Continued investigation is warranted for further validation.
SU‐E‐J‐222: Feasibility Study of MRI‐Only Proton Therapy Planning
Authors: Spadea M , Izquierdo D , Catana C , Collins‐Fekete C , Bortfeld T , Seco J 
Published: June 2015

Purpose:To assess the dosimetric equivalence of MRI based proton planning vs. single energy x‐ray CT.Methods:8 glioblastoma patients were imaged with CT and MRI after surgical resection. T1‐weighted 3DMPRAGE was used to delineate the GTV, which was subsequently rigidly registered to the CT volume. A pseudoCT was generated from the aligned MRI by combining segmentation and atlas‐based approaches. The spatial resolution both for pseudo‐ and real CT was 0.6×0.6×2.5mm. Three orthogonal proton beams were simulated on the pseudoCT. Two co‐planar beams were set on the axial plane. The third one was planned parallel to the cranio‐caudal (CC) direction. Each beam was set to cover the GTV at 98% of the nominal dose (18Gy). The proton plan was copied and transferred to the real CT, including aperture/compensator geometry. Dose comparison between pseudoCT and CT plan was performed beam‐by‐beam by quantifying the range shift of dose profile on each slice of the GTV. The GTV's V98 was computed for the CT.Results:For beams in axial plane the median absolute value of the range shift was 0.3mm, with 0.9mm and 1.4mm as 95th percentile and maximum, respectively. Worst scenarios were found for the CC beam, where we measured 1.1mm (median), 2.7mm (95thpercentile) and 5mm (maximum). Regardless the direction, beams passing through the surgical site, where metal (Titanium MRI‐compatible) staples were present, were mostly affected by range shift. GTV's V98 for CT was not lower than 99.3%.Conclusion:The study showed the clinical feasibility of an MRI‐alone proton plan. Advantages include the possibility to rely on better soft tissue contrast for target and organs at risk delineation without the need of further CT scan and image registration. Additional investigation is required in presence of metal implants along the beam path and to account for partial volume effects due to slice thickness.
SU‐E‐J‐224: Using UTE and T1 Weighted Spin Echo Pulse Sequences for MR‐Only Treatment Planning; Phantom Study
Authors: Yu H , Fatemi A , Sahgal A 
Published: June 2015

Purpose:Investigating a new approach in MRI based treatment planning using the combination of (Ultrashort Echo Time) UTE and T1 weighted spin echo pulse sequences to delineate air, bone and water (soft tissues) in generating pseudo CT images comparable with CT.Methods:A gel phantom containing chicken bones, ping pang balls filled with distilled water and air bubbles, was made. It scanned with MRI using UTE and 2D T1W SE pulse sequences with (in plane resolution= 0.53mm, slice thickness= 2 mm) and CT with (in plane resolution= 0.5 mm and slice thickness= 0.75mm) as a ground truth for geometrical accuracy. The UTE and T1W SE images were registered with CT using mutual information registration algorithm provided by Philips Pinnacle treatment planning system. The phantom boundaries were detected using Canny edge detection algorithm for CT, and MR images. The bone, air bubbles and water in ping pong balls were segmented from CT images using threshold 300HU, ‐ 950HU and 0HU, respectively. These tissue inserts were automatically segmented from combined UTE and T1W SE images using edge detection and relative intensity histograms of the phantom. The obtained segmentations of air, bone and water inserts were evaluated with those obtained from CT.Results:Bone and air can be clearly differentiated in UTE images comparable to CT. Combining UTE and T1W SE images successfully segmented the air, bone and water. The maximum segmentation differences from combine MRI images (UTE and T1W SE) and CT are within 1.3 mm, 1.1mm for bone, air, respectively. The geometric distortion of UTE sequence is small less than 1 pixel (0.53 mm) of MR image resolution.Conclusion:Our approach indicates that MRI can be used solely for treatment planning and its quality is comparable with CT.
SU‐E‐J‐225: CEST Imaging in Head and Neck Cancer Patients
Authors: Wang J , Hwang K , Fuller C , Mohamed A , Ding Y , Frank S , Hazle J , Zhou J 
Published: June 2015

Purpose:Chemical Exchange Saturation Transfer (CEST) imaging is an MRI technique enables the detection and imaging of metabolically active compounds in vivo. It has been used to differentiate tumor types and metabolic characteristics. Unlike PET/CT,CEST imaging does not use isotopes so it can be used on patient repeatedly. This study is to report the preliminary results of CEST imaging in Head and Neck cancer (HNC) patients.Methods:A CEST imaging sequence and the post‐processing software was developed on a 3T clinical MRI scanner. Ten patients with Human papilloma virus positive oropharyngeal cancer were imaged in their immobilized treatment position. A 5 mm slice CEST image was acquired (128×128, FOV=20∼24cm) to encompass the maximum dimension of tumor. Twenty‐nine off‐set frequencies (from −7.8ppm to +7.8 ppm) were acquired to obtain the Z‐spectrum. Asymmetry analysis was used to extract the CEST contrasts. ROI at the tumor, node and surrounding tissues were measured.Results:CEST images were successfully acquired and Zspectrum asymmetry analysis demonstrated clear CEST contrasts in tumor as well as the surrounding tissues. 3∼5% CEST contrast in the range of 1 to 4 ppm was noted in tumor as well as grossly involved nodes. Injection of glucose produced a marked increase of CEST contrast in tumor region (∼10%). Motion and pulsation artifacts tend to smear the CEST contrast, making the interpretation of the image contrast difficult. Field nonuniformity, pulsation in blood vesicle and susceptibility artifacts caused by air cavities were also problematic for CEST imaging.Conclusion:We have demonstrated successful CEST acquisition and Z‐spectrum reconstruction on HNC patients with a clinical scanner. MRI acquisition in immobilized treatment position is critical for image quality as well as the success of CEST image acquisition. CEST images provide novel contrast of metabolites in HNC and present great potential in the pre‐ and post‐treatment assessment of patients undergoing radiation therapy.
SU‐E‐J‐232: Feasibility of MRI‐Based Preplan On Low Dose Rate Prostate Brachytherapy
Authors: Huang Y , Tward J , Rassiah‐Szegedi P , Zhao H , Sarkar V , Huang L , Szegedi M , Kokeny K , Salter B 
Published: June 2015

Purpose:To investigate the feasibility of using MRI‐based preplan for low dose rate prostate brachytherapy.Methods:12 patients who received transrectal ultrasound (TRUS) guided prostate brachytherapy with Pd‐103 were retrospectively studied. Our care‐standard of the TRUS‐based preplan served as the control. One or more prostate T2‐weighted wide and/or narrow‐field of view MRIs obtained within the 3 months prior to the implant were imported into the MIM Symphony software v6.3 (MIM Software Inc., Cleveland, OH) for each patient. In total, 37 MRI preplans (10 different image sequences with average thickness of 4.8mm) were generated. The contoured prostate volume and the seed counts required to achieve adequate dosimetric coverage from TRUS and MRI preplans were compared for each patient. The effects of different MRI sequences and image thicknesses were also investigated statistically using Student's t‐test. Lastly, the nomogram from the MRI preplan and TRUS preplan from our historical treatment data were compared.Results:The average prostate volume contoured on the TRUS and MRI were 26.6cc (range: 12.6∼41.3cc), and 27.4 cc (range: 14.3∼50.0cc), respectively. Axial MRI thicknesses (range: 3.5∼8.1mm) did not significantly affect the contoured volume or the number of seeds required on the preplan (R2 = 0.0002 and 0.0012, respectively). Four of the MRI sequences (AX‐T2, AX‐T2‐Whole‐Pelvis, AX‐T2‐FSE, and AXIALT2‐ Hi‐Res) showed statistically significant better prostate volume agreement with TRUS than the other seven sequences (P <0.01). Nomogram overlay between the MRI and TRUS preplans showed good agreement; indicating volumes contoured on MRI preplan scan reliably predict how many seeds are needed for implant.Conclusion:Although MRI does not allow for determination of the actual implant geometry, it can give reliable volumes for seed ordering purposes. Our future work will investigate if MRI is sufficient to reliably replace TRUS preplanning in patients where preplan TRUS may be technically challenging.
SU‐E‐J‐234: Application of a Breathing Motion Model to ViewRay Cine MR Images
Authors: O'Connell D. P. , Thomas D. H. , Dou T. H. , Lamb J. M. , Yang L. , Low D. A. 
Published: June 2015

Purpose:A respiratory motion model previously used to generate breathing‐gated CT images was used with cine MR images. Accuracy and predictive ability of the in‐plane models were evaluated.Methods:Sagittalplane cine MR images of a patient undergoing treatment on a ViewRay MRI/radiotherapy system were acquired before and during treatment. Images were acquired at 4 frames/second with 3.5 × 3.5 mm resolution and a slice thickness of 5 mm. The first cine frame was deformably registered to following frames. Superior/inferior component of the tumor centroid position was used as a breathing surrogate. Deformation vectors and surrogate measurements were used to determine motion model parameters. Model error was evaluated and subsequent treatment cines were predicted from breathing surrogate data. A simulated CT cine was created by generating breathing‐gated volumetric images at 0.25 second intervals along the measured breathing trace, selecting a sagittal slice and downsampling to the resolution of the MR cines. A motion model was built using the first half of the simulated cine data. Model accuracy and error in predicting the remaining frames of the cine were evaluated.Results:Mean difference between model predicted and deformably registered lung tissue positions for the 28 second preview MR cine acquired before treatment was 0.81 +/− 0.30 mm. The model was used to predict two minutes of the subsequent treatment cine with a mean accuracy of 1.59 +/− 0.63 mm.Conclusion:Inplane motion models were built using MR cine images and evaluated for accuracy and ability to predict future respiratory motion from breathing surrogate measurements. Examination of long term predictive ability is ongoing. The technique was applied to simulated CT cines for further validation, and the authors are currently investigating use of in‐plane models to update pre‐existing volumetric motion models used for generation of breathing‐gated CT planning images.
SU‐E‐J‐237: Real‐Time 3D Anatomy Estimation From Undersampled MR Acquisitions
Authors: Glitzner M , de Senneville B Denis , Lagendijk J , Raaymakers B , Crijns S 
Published: June 2015

Recent developments made MRI guided radiotherapy feasible. Performing simultaneous imaging during fractions can provide information about changing anatomy by means of deformable image registration for either immediate plan adaptations or accurate dose accumulation on the changing anatomy. In 3D MRI, however, acquisition time is considerable and scales with resolution. Furthermore, intra‐scan motion degrades image quality.In this work, we investigate the sensitivity of registration quality on imageresolution: potentially, by employing spatial undersampling, the acquisition timeof MR images for the purpose of deformable image registration can be reducedsignificantly.On a volunteer, 3D‐MR imaging data was sampled in a navigator‐gated manner, acquiring one axial volume (360×260×100mm3) per 3s during exhale phase. A T1‐weighted FFE sequence was used with an acquired voxel size of (2.5mm3) for a duration of 17min. Deformation vector fields were evaluated for 100 imaging cycles with respect to the initial anatomy using deformable image registration based on optical flow. Subsequently, the imaging data was downsampled by a factor of 2, simulating a fourfold acquisition speed. Displacements of the downsampled volumes were then calculated by the same process.In kidneyliver boundaries and the region around stomach/duodenum, prominent organ drifts could be observed in both the original and the downsampled imaging data. An increasing displacement of approximately 2mm was observed for the kidney, while an area around the stomach showed sudden displacements of 4mm. Comparison of the motile points over time showed high reproducibility between the displacements of high‐resolution and downsampled volumes: over a 17min acquisition, the componentwise RMS error was not more than 0.38mm.Based on the synthetic experiments, 3D nonrigid image registration shows little sensitivity to image resolution and the displacement information is preserved even when halving the resolution. This can be employed to greatly reduce image acquisition times for interventional applications in real‐time.This work was funded by the SoRTS consortium, which includes the industry partners Elekta, Philips and Technolution
SU‐E‐J‐238: First‐Order Approximation of Time‐Resolved 4DMRI From Cine 2DMRI and Respiratory‐Correlated 4DMRI
Authors: Li G , Wei J , Tyagi N , Hunt M , Deasy J 
Published: June 2015

Purpose:Cine 2DMRI is useful in MR‐guided radiotherapy but it lacks volumetric information. We explore the feasibility of estimating timeresolved (TR) 4DMRI based on cine 2DMRI and respiratory‐correlated (RC) 4DMRI though simulation.Methods:We hypothesize that a volumetric image during free breathing can be approximated by interpolation among 3DMRI image sets generated from a RC‐4DMRI. Two patients’ RC‐4DMRI with 4 or 5 phases were used to generate additional 3DMRI by interpolation. For each patient, six libraries were created to have total 5‐to‐35 3DMRI images by 0–6 equi‐spaced tri‐linear interpolation between adjacent and full‐inhalation/full‐exhalation phases. Sagittal cine 2DMRI were generated from reference 3DMRIs created from separate, unique interpolations from the original RC‐4DMRI. To test if accurate 3DMRI could be generated through rigid registration of the cine 2DMRI to the 3DMRI libraries, each sagittal 2DMRI was registered to sagittal cuts in the same location in the 3DMRI within each library to identify the two best matches: one with greater lung volume and one with smaller. A final interpolation between the corresponding 3DMRI was then performed to produce the first‐order‐approximation (FOA) 3DMRI. The quality and performance of the FOA as a function of library size was assessed using both the difference in lung volume and average voxel intensity between the FOA and the reference 3DMRI.Results:The discrepancy between the FOA and reference 3DMRI decreases as the library size increases. The 3D lung volume difference decreases from 5–15% to 1–2% as the library size increases from 5 to 35 image sets. The average difference in lung voxel intensity decreases from 7–8 to 5–6 with the lung intensity being 0–135.Conclusion:This study indicates that the quality of FOA 3DMRI improves with increasing 3DMRI library size. On‐going investigations will test this approach using actual cine 2DMRI and introduce a higher order approximation for improvements.This study is in part supported by NIH (U54CA137788 and U54CA132378).
SU‐E‐J‐240: Development of a Novel 4D MRI Sequence for Real‐Time Liver Tumor Tracking During Radiotherapy
Authors: Zhuang L , Ye Y , Burmeister J 
Published: June 2015

Purpose:To develop a Novel 4D MRI Technique that is feasible for realtime liver tumor tracking during radiotherapy.Methods:A volunteer underwent an abdominal 2D fast EPI coronal scan on a 3.0T MRI scanner (Siemens Inc., Germany). An optimal set of parameters was determined based on image quality and scan time. A total of 23 slices were scanned to cover the whole liver in the test scan. For each scan position, the 2D images were retrospectively sorted into multiple phases based on breathing signal extracted from the images. Consequently the 2D slices with same phase numbers were stacked to form one 3D image. Multiple phases of 3D images formed the 4D MRI sequence representing one breathing cycle.Results:The optimal set of scan parameters were: TR= 57ms, TE= 19ms, FOV read= 320mm and flip angle= 30°, which resulted in a total scan time of 14s for 200 frames (FMs) per slice and image resolution of (2.5mm,2.5mm,5.0mm) in three directions. Ten phases of 3D images were generated, each of which had 23 slices. Based on our test scan, only 100FMs were necessary for the phase sorting process which may lower the scan time to 7s/100FMs/slice. For example, only 5 slices/35s are necessary for a 4D MRI scan to cover liver tumor size ≤ 2cm leading to the possibility of tumor trajectory tracking every 35s during treatment.Conclusion:The novel 4D MRI technique we developed can reconstruct a 4D liver MRI sequence representing one breathing cycle (7s/ slice) without an external monitor. This technique can potentially be used for real‐time liver tumor tracking during radiotherapy.
SU‐E‐J‐244: Development and Validation of a Knowledge Based Planning Model for External Beam Radiation Therapy of Locally Advanced Non‐Small Cell Lung Cancer
Authors: Liu Z , Larsen E , Bahamondes S. , Choi M , Li J , Cranford K , Hayes C , Grow A , Zheng Y , Wu X , Pai S , Kennedy A 
Published: June 2015

Purpose:The study aims to develop and validate a knowledge based planning (KBP) model for external beam radiation therapy of locally advanced non‐small cell lung cancer (LA‐NSCLC).Methods:RapidPlan™ technology was used to develop a lung KBP model. Plans from 65 patients with LA‐NSCLC were used to train the model. 25 patients were treated with VMAT, and the other patients were treated with IMRT. Organs‐at‐risk (OARs) included right lung, left lung, heart, esophagus, and spinal cord. DVH and geometric distribution DVH were extracted from the treated plans. The model was trained using principal component analysis and step‐wise multiple regression. Box plot and regression plot tools were used to identify geometric outliers and dosimetry outliers and help fine‐tune the model. The validation was performed by (a) comparing predicted DVH boundaries to actual DVHs of 63 patients and (b) using an independent set of treatment planning data.Results:63 out of 65 plans were included in the final KBP model with PTV volume ranging from 102.5cc to 1450.2cc. Total treatment dose prescription varied from 50Gy to 70Gy based on institutional guidelines. One patient was excluded due to geometric outlier where 2.18cc of spinal cord was included in PTV. The other patient was excluded due to dosimetric outlier where the dose sparing to spinal cord was heavily enforced in the clinical plan. Target volume, OAR volume, OAR overlap volume percentage to target, and OAR out‐of‐field volume were included in the trained model. Lungs and heart had two principal component scores of GEDVH, whereas spinal cord and esophagus had three in the final model. Predicted DVH band (mean ±1 standard deviation) represented 66.2±3.6% of all DVHs.Conclusion:A KBP model was developed and validated for radiotherapy of LA‐NSCLC in a commercial treatment planning system. The clinical implementation may improve the consistency of IMRT/VMAT planning.
SU‐E‐J‐246: CT‐Based Volumetric Features Are Associated with Somatic Mutations in Lung Cancer
Authors: Coroller T , Grossmann P , Hou Y , Lee S , Mak R , Aerts H 
Published: June 2015

Purpose:Subsets of non‐small cell lung cancer (NSCLC) are driven by mutations in key oncogenes, with unique biology including susceptibility to targeted treatment. Additionally, those mutations could lead to phenotypic differences of the primary tumor that can be assess with quantitative imaging. In this study, we investigated whether somatic mutation are associated with, and hence can be predicted by CT tumor volume‐based features of NSCLC patients.Methods:We included 117 NSCLC patients with treatment‐planning CT scans in our analysis and clinical genotyping for the epidermal growth factor receptor (EGFR) and Kirsten rat sarcoma viral oncogene homolog (KRAS) oncogenes. We extracted four volumetric features describing volume and diameters (x/y axis and 3D) of the primary tumor. Volumetric differences between mutant and wild‐type tumors were assessed using Wilcoxon test. Predictive value of the volumetric features for mutation status was assessed using the area under the curve (AUC).Results:Genotype distribution included 14 (12%) EGFR mutant, 35 (30%) KRAS mutant, and 68 (58%) wild‐type tumors. All volumetric features for EGFR mutant were significantly (p‐value <0.05) lower than for KRAS mutant and Wild‐Type. No volumetric features were significantly different between KRAS and Wild‐Type. The median (Q1–Q3) for volume was 10.2(6.1– 29.6), 39.3(14.3–89.7) and 49(10.7–119) for EGFR, KRAS and Wild‐Type respectively. All volumetric features were also significant predictive features for EGFR mutation with median (range) AUC of 0.69(0.67–0.70) and all p‐value<0.05. However, the AUC was only 0.51(0.50–0.51) for KRAS mutation.Conclusion:EGFR mutant primary tumors were significantly smaller (for all volumetric features) than KRAS or Wild‐Type. Moreover, all volumetric features were significantly predictive for EGFR. KRAS and Wild‐type could not be discriminated only based on volumetric features. A larger set of imaging features (e.g. Radiomics) would help find more predictive biomarkers for tumor mutation status.