bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐E‐J‐17: Intra‐Fractional Prostate Movement Correction During Treatment Delivery Period for Prostate Cancer Using the Intra‐Fractional Orthogonal KV‐MV Image Pairs
Authors: Zhang J , Azawi S , Cho‐Lim J , Wei R , Williams R , Frank E 
Published: June 2015

Purpose:To evaluate the intra‐fractional prostate movement range during the beam delivery and implement new IGRT method to correct the prostate movement during the hypofractionated prostate treatment delivery.Methods:To evaluate the prostate internal motion range during the beam delivery, 11 conventional treatments were utilized. Two‐arc RapidArc plans were used for the treatment delivery. Orthogonal KV imaging is performed in the middle of the treatment to correct intra‐fractional prostate movement. However, it takes gantry‐mounted on‐board imaging system relative long time to finish the orthogonal KV imaging because of gantry rotation. To avoid gantry movement and accelerate the IGRT processing time, orthogonal KV‐MV image pair is tested using the OBI daily QA Cube phantom.Results:The average prostate movement between two orthogonal KV image pairs was 0.38cm (0.20cm ∼ 0.85cm). And the interval time between them was 6.71 min (4.64min ∼ 9.22 min). 2‐arc beam delivery time is within 3 minutes for conventional RapidArc treatment delivery. Hypofractionated treatment or SBRT need 4 partial arc and possible non‐coplanar technology, which need much longer beam delivery time. Therefore prostate movement might be larger. New orthogonal KV‐MV image pair is a new method to correct the prostate movement in the middle of the beam delivery if real time tracking method is not available. Orthogonal KV‐MV image pair doesn't need gantry rotation. Images were acquired quickly which minimized possible new prostate movement. Therefore orthogonal KV‐MV image pair is feasible for IGRT.Conclusion:Hypofractionated prostate treatment with less PTV margin always needs longer beam delivery time. Therefore prostate movement correction during the treatment delivery is critical. Orthogonal KV‐MV imaging pair is efficient and accurate to correct the prostate movement during treatment beam delivery. Due to limited fraction number and high dose per fraction, the MV imaging dose is negligible.
SU‐E‐J‐23: Characteristics of X‐Rays From ExacTrac and Patient Dose From Imaging Procedures
Authors: Ding G 
Published: June 2015

Purpose:The purpose of this investigation is 1) provide the beam characteristics of x‐rays produced by a Novalis TX ExacTrac system; 2) present a method to commission such beams, 3) present radiation dose to patients resulting from the imaging procedures.Methods:The Monte Carlo simulations were used to obtain the characteristics of kV beams and validated by measurements. The calculated beam HVLs, profiles and depth‐dose curves were benchmarked against measurements. Twelve different image acquisition protocols were studied. The x‐ray tube voltage ranges from 70 ‐ 145 kV and milliampere‐second (mAs) ranges from 8 ‐ 80 mAs depending on the selection of Cranium, Head & Neck, Thorax or Abdomen imaging protocols. The beam output of each image acquisition protocol was determined by using an ionization chamber. The air kerma calibration factors of the ion chamber were obtained from an Accredited Dosimetry Calibration Laboratory for specified HVLs.Results:The agreements between measured and simulated results were within the uncertainties for HVLs, dose profiles and depth‐dose curves. When %dd was normalized at 1 cm depth, its values at depth of 5 cm ranged from 45% to 66% of in water for kV beams range from 70 kVp to 145 kVp respectively. For head images, a typical dose to eye resulting from single projection ranged from 0.008 cGy to 0.025 cGy depending on the cranial image protocols selected. For a single pelvic image the skin dose could reach up to 0.1 cGy from an abdominal protocol.Conclusion:Although multiple pairs of x‐ray images are commonly acquired during a daily patient treatment, the imaging doses to patients resulting from the sum of these projected x‐rays are generally much less than 0.5 cGy. The knowledge obtained from this investigation can be used to estimate the image dose and optimize the used of the system.
SU‐E‐J‐31: Monitor Interfractional Variation of Tumor Respiratory Motion Using 4D KV Conebeam Computed Tomography for Stereotactic Body Radiation Therapy of Lung Cancer
Authors: Tai A , Prior P , Gore E , Johnstone C , Li X 
Published: June 2015

Purpose:4DCT has been widely used to generate internal tumor volume (ITV) for a lung tumor for treatment planning. However, lung tumors may show different respiratory motion on the treatment day. The purpose of this study is to evaluate 4D KV conebeam computed tomography (CBCT) for monitoring tumor interfractional motion variation between simulation and each fraction of stereotactic body radiation therapy (SBRT) for lung cancer.Methods:4D KV CBCT was acquired with the Elekta XVI system. The accuracy of 4D KV CBCT for image‐guided radiation therapy (IGRT) was tested with a dynamic thorax motion phantom (CIRS, Virginia) with a linear amplitude of 2 cm. In addition, an adult anthropomorphic phantom (Alderson, Rando) with optically stimulated luminescence (OSL) dosimeters embedded at the center and periphery of a slab of solid water was used to measure the dose of 4D KV CBCT and to compare it with the dose with 3D KV CBCT. The image registration was performed by aligning\ each phase images of 4D KV CBCT to the planning images and the final couch shifts were calculated as a mean of all these individual shifts along each direction.A workflow was established based on these quality assurance tests for lung cancer patients.Results:4D KV CBCT does not increase imaging dose in comparison to 3D KV CBCT. Acquisition of 4D KV CBCT is 4 minutes as compared to 2 minutes for 3D KV CBCT. Most of patients showed a small daily variation of tumor respiratory motion about 2 mm. However, some patients may have more than 5 mm variations of tumor respiratory motion.Conclusion:The radiation dose does not increase with 4D KV CBCT. 4D KV CBCT is a useful tool for monitoring interfractional variations of tumor respiratory motion before SBRT of lung cancer patients.
SU‐E‐J‐48: Imaging Origin‐Radiation Isocenter Coincidence for Linac‐Based SRS with Novalis Tx
Authors: Geraghty C , Workie D , Hasson B 
Published: June 2015

PurposeTo implement and evaluate an image‐based Winston‐Lutz (WL) test to measure the displacement between ExacTrac imaging origin and radiation isocenter on a Novalis Tx system using RIT V6.2 software analysis tools. Displacement between imaging and radiation isocenters was tracked over time. The method was applied for cone‐based and MLC‐based WL tests.MethodsThe Brainlab Winston‐Lutz phantom was aligned to room lasers. The ExacTrac imaging system was then used to detect the Winston‐ Lutz phantom and obtain the displacement between the center of the phantom and the imaging origin. EPID images of the phantom were obtained at various gantry and couch angles and analyzed with RIT calculating the phantom center to radiation isocenter displacement. The RIT and Exactrac displacements were combined to calculate the displacement between imaging origin and radiation isocenter. Results were tracked over time.ResultsMean displacements between ExacTrac origin and radiation isocenter were: VRT: −0.1mm ± 0.3mm, LNG: 0.5mm ± 0.2mm, LAT: 0.2mm ± 0.2mm (vector magnitude of 0.7 ± 0.2mm). Radiation isocenter was characterized by the mean of the standard deviations of the WL phantom displacements: σVRT: 0.2mm, σLNG: 0.4mm, σLAT: 0.6mm. The linac couch base was serviced to reduce couch walkout. This reduced σLAT to 0.2mm. These measurements established a new baseline of radiation isocenter‐imaging origin coincidence.ConclusionThe image‐based WL test has ensured submillimeter localization accuracy using the ExacTrac imaging system. Standard deviations of ExacTrac‐radiation isocenter displacements indicate that average agreement within 0.3mm is possible in each axis. This WL test is a departure from the tradiational WL in that imaging origin/radiation isocenter agreement is the end goal not lasers/radiation isocenter.
SU‐E‐J‐51: The Impact of Off‐Center Position On Image Quality of Megavoltage CT
Authors: Zhang K , Hu ZH , Dai JR 
Published: June 2015

PurposeTo quantify the impact of off‐center position on image quality of megavoltage CT in head and neck tumor patient and body tumor patient.MethodsA Catphan 600 phantom and a Cheese phantom were imaged by TomoHD at the center and off‐center positions stepped by 5cm in AP and LR directions until the phantom edge approaching the imaging edge with fine, normal and coarse scan modes. Both phantoms incorporate image uniformity module, spatial resolution module and CT number linearity module. The CT number linearity module of Cheese phantom was set to simulate Catphan 600 phantom in a larger size. According to AAPM TG‐148 report, noise, image uniformity, spatial resolution and CT number variation were assessed for MVCT image quality. Centers of peripheral ROIs for noise and uniformity were about 4cm from phantom edge.ResultsNoise in all positions was within the criteria except the peripheral regions for Cheese phantom at off‐center scan positions. Image uniformity for most positions was acceptable, and all failed data were from the ROIs near imaging edge area. Spatial resolution degraded with off‐center scanning, and scan mode also made it worse with wider slice thickness, but just 1 level at most. CT number change with and without image uniformity correction for all positions were all less than tolerance, but it was close to the red line for water‐equivalent material.ConclusionThis work indicates that if depth of lesions is below 4cm and MVCT are used for dose calculations, the ipsilateral body edge should be 5cm within imaging edge. Otherwise, image uniformity should be concerned.
SU‐E‐J‐115: Correlation of Displacement Vector Fields Calculated by Deformable Image Registration Algorithms with Motion Parameters of CT Images with Well‐Defined Targets and Controlled‐Motion
Authors: Jaskowiak J , Alsbou N , Ahmad S , Ali I 
Published: June 2015

Purpose:To investigate correlation of displacement vector fields (DVF) calculated by deformable image registration algorithms with motion parameters in helical axial and cone‐beam CT images with motion artifacts.Methods:A mobile thorax phantom with well‐known targets with different sizes that were made from water‐equivalent material and inserted in foam to simulate lung lesions. The thorax phantom was imaged with helical, axial and cone‐beam CT. The phantom was moved with a cyclic motion with different motion amplitudes and frequencies along the superior‐inferior direction. Different deformable image registration algorithms including demons, fast demons, Horn‐Shunck and iterative‐optical‐flow from the DIRART software were used to deform CT images for the phantom with different motion patterns. The CT images of the mobile phantom were deformed to CT images of the stationary phantom.Results:The values of displacement vectors calculated by deformable image registration algorithm correlated strongly with motion amplitude where large displacement vectors were calculated for CT images with large motion amplitudes. For example, the maximal displacement vectors were nearly equal to the motion amplitudes (5mm, 10mm or 20mm) at interfaces between the mobile targets lung tissue, while the minimal displacement vectors were nearly equal to negative the motion amplitudes. The maximal and minimal displacement vectors matched with edges of the blurred targets along the Z‐axis (motion‐direction), while DVF's were small in the other directions. This indicates that the blurred edges by phantom motion were shifted largely to match with the actual target edge. These shifts were nearly equal to the motion amplitude.Conclusions:The DVF from deformable‐image registration algorithms correlated well with motion amplitude of well‐defined mobile targets. This can be used to extract motion parameters such as amplitude. However, as motion amplitudes increased, image artifacts increased significantly and that limited image quality and poor correlation between the motion amplitude and DVF was obtained.
SU‐E‐J‐117: Comparison of Different QA Methods for Deformable Image Registration to the Known Errors for Prostate and Head‐And‐Neck Virtual Phantoms
Authors: Obeidat M. , Narayanasamy G. , Cline K. , Stathakis S. , Pouliot J. , Kim H. , Kirby N. 
Published: June 2015

Purpose:Several methods can evaluate the accuracy of deformable image registration (DIR), but they are not necessarily a true measurement of DIR accuracy. The purpose here is to evaluate how these methods compare to known errors found with prostate and head‐and‐neck virtual phantoms.Methods:Quality assurance of DIR falls in three basic categories: contour comparison, landmark tracking, and image similarity. These different methods were utilized to evaluate the performance of four DIR algorithms, MIM and three from Velocity: Deformable (DEF), Deformable Multi‐Pass (DMP), and Extended Deformable Multi‐Pass (XMP). For contour comparison, organs were contoured (total of 15) on both the undeformed and deformed images. Then, the DIR algorithms were used to transfer contours from the undeformed to the deformed image and compared to that drawn directly on the deformed image. For landmark tracking, we found visible landmarks and measured their locations on the deformed and the undeformed images. The resulting deformation measurement was then compared to that predicted by the algorithm. For image similarity, we calculated the root‐mean‐square and the mean‐absolute differences between the deformed and warped undeformed images. Finally, we calculated the actual spatial registration error for each DIR algorithm, from the known deformations.Results:The MIM algorithm produced the lowest average errors for the landmark analysis, the closest image similarity, and overall the most accurate contour transfers. When compared to the known deformations, MIM also produced the lowest average error, but the largest spatial registration errors. The lowest maximum spatial errors were made by DEF and DMP for the prostate and head‐and‐neck phantoms, respectively.Conclusion:Contour comparison, landmark tracking, and image similarity all indicated that MIM was the most accurate DIR algorithm. These metrics were aligned with MIM producing the lowest known mean errors, but did not catch that MIM was also by far producing the largest known errors.
SU‐E‐J‐119: Head‐And‐Neck Digital Phantoms for Geometric and Dosimetric Uncertainty Evaluation of CT‐CBCT Deformable Image Registration
Authors: Shen Z , Bzdusek K , Koyfman S , Xia P 
Published: June 2015

Purpose:To evaluate geometric and dosimetric uncertainties of CT‐CBCT deformable image registration (DIR) algorithms using digital phantoms generated from real patients.Methods:We selected ten H&N cancer patients with adaptive IMRT. For each patient, a planning CT (CT1), a replanning CT (CT2), and a pretreatment CBCT (CBCT1) were used as the basis for digital phantom creation. Manually adjusted meshes were created for selected ROIs (e.g. PTVs, brainstem, spinal cord, mandible, and parotids) on CT1 and CT2. The mesh vertices were input into a thin‐plate spline algorithm to generate a reference displacement vector field (DVF). The reference DVF was applied to CBCT1 to create a simulated mid‐treatment CBCT (CBCT2). The CT‐CBCT digital phantom consisted of CT1 and CBCT2, which were linked by the reference DVF. Three DIR algorithms (Demons, B‐Spline, and intensity‐based) were applied to these ten digital phantoms. The images, ROIs, and volumetric doses were mapped from CT1 to CBCT2 using the DVFs computed by these three DIRs and compared to those mapped using the reference DVF.Results:The average Dice coefficients for selected ROIs were from 0.83 to 0.94 for Demons, from 0.82 to 0.95 for B‐Spline, and from 0.67 to 0.89 for intensity‐based DIR. The average Hausdorff distances for selected ROIs were from 2.4 to 6.2 mm for Demons, from 1.8 to 5.9 mm for B‐Spline, and from 2.8 to 11.2 mm for intensity‐based DIR. The average absolute dose errors for selected ROIs were from 0.7 to 2.1 Gy for Demons, from 0.7 to 2.9 Gy for B‐ Spline, and from 1.3 to 4.5 Gy for intensity‐based DIR.Conclusion:Using clinically realistic CT‐CBCT digital phantoms, Demons and B‐Spline were shown to have similar geometric and dosimetric uncertainties while intensity‐based DIR had the worst uncertainties. CT‐CBCT DIR has the potential to provide accurate CBCT‐based dose verification for H&N adaptive radiotherapy.Z Shen: None; K Bzdusek: an employee of Philips Healthcare; S Koyfman: None; P Xia: received research grants from Philips Healthcare and Siemens Healthcare
SU‐E‐J‐125: A Novel IMRT Planning Technique to Spare Sacral Bone Marrow in Pelvic Cancer Patients
Authors: McGuire S , Bhatia S , Sun W , Menda Y , Ponto L , Gross B , Buatti J 
Published: June 2015

Purpose:Develop an IMRT planning technique that can preferentially spare sacral bone marrow for pelvic cancer patients.Methods:Six pelvic cancer patients (two each with anal, cervical, and rectal cancer) were enrolled in an IRB approved protocol to obtain FLT PET images at simulation, during, and post chemoradiation therapy. Initially, conventional IMRT plans were created to maintain target coverage and reduce dose to OARs such as bladder, bowel, rectum, and femoral heads. Simulation FLT PET images were used to create IMRT plans to spare bone marrow identified as regions with SUV of 2 or greater (IMRT‐BMS) within the pelvic bones from top of L3 to 5mm below the greater trochanter without compromising PTV coverage or OAR sparing when compared to the initial IMRT plan. IMRT‐BMS plans used 8–10 beam angles that surrounded the subject. These plans were used for treatment. Retrospectively, the same simulation FLT PET images were used to create IMRT plans that spared bone marrow located in the sacral pelvic bone region (IMRT‐FAN) also without compromising PTV coverage or OAR sparing. IMRT‐FAN plans used 16 beam angles every 12° anteriorly from 90° – 270°. Optimization objectives for the sacral bone marrow avoidance region were weighted to reduce ≥V10.Results:IMRT‐FAN reduced dose to the sacral bone marrow for all six subjects. The average V5, V10, V20, and V30 differences from the IMRT‐BMS plan were −2.2 ± 1.7%, −11.4 ± 3.6%, −17.6 ± 5.1%, and −19.1 ± 8.1% respectively. Average PTV coverage change was 0.5% ± 0.8% from the conventional IMRT plan.Conclusion:An IMRT planning technique that uses beams from the anterior and lateral directions reduced the volume of sacral bone marrow that receives ≤10Gy while maintaining PTV coverage and OAR sparing. Additionally, the volume of sacral bone marrow that received 20 or 30 Gy was also reduced.
SU‐E‐J‐127: Implementation of An Online Replanning Tool for VMAT Using Flattening Filter‐Free Beams
Authors: Ates O , Ahunbay E , Li X 
Published: June 2015

Purpose:This is to report the implementation of an online replanning tool based on segment aperture morphing (SAM) for VMAT with flattening filter free (FFF) beams.Methods:Previously reported SAM algorithm modified to accommodate VMAT with FFF beams was implemented in a tool that was interfaced with a treatment planning system (Monaco, Elekta). The tool allows (1) to output the beam parameters of the original VMAT plan from Monaco, and (2) to input the apertures generated from the SAM algorithm into Monaco for the dose calculation on daily CT/CBCT/MRI in the following steps:(1) Quickly generating target contour based on the image of the day, using an auto‐segmentation tool (ADMIRE, Elekta) with manual editing if necessary; (2) Morphing apertures based on the SAM in the original VMAT plan to account for the interfractional change of the target from the planning to the daily images; (3) Calculating dose distribution for new apertures with the same numbers of MU as in the original plan; (4) Transferring the new plan into a record & verify system (MOSAIQ, Elekta); (5) Performing a pre‐delivery QA based on software; (6) Delivering the adaptive plan for the fraction.This workflow was implemented on a 16‐CPU (2.6 GHz dual‐core) hardware with GPU and was tested for sample cases of prostate, pancreas and lung tumors.Results:The online replanning process can be completed within 10 minutes. The adaptive plans generally have improved the plan quality when compared to the IGRT repositioning plans. The adaptive plans with FFF beams have better normal tissue sparing as compared with those of FF beams.Conclusion:The online replanning tool based on SAM can quickly generate adaptive VMAT plans using FFF beams with improved plan quality than those from the IGRT repositioning plans based on daily CT/CBCT/MRI and can be used clinically.This research was supported by Elekta Inc. (Crawley, UK).
SU‐E‐J‐133: Autosegmentation of Linac CBCT: Improved Accuracy Via Penalized Likelihood Reconstruction
Authors: Chen Y 
Published: June 2015

Purpose:To improve the quality of kV X‐ray cone beam CT (CBCT) for use in radiotherapy delivery assessment and re‐planning by using penalized likelihood (PL) iterative reconstruction and auto‐segmentation accuracy of the resulting CBCTs as an image quality metric.Methods:Present filtered backprojection (FBP) CBCT reconstructions can be improved upon by PL reconstruction with image formation models and appropriate regularization constraints. We use two constraints: 1) image smoothing via an edge preserving filter, and 2) a constraint minimizing the differences between the reconstruction and a registered prior image. Reconstructions of prostate therapy CBCTs were computed with constraint 1 alone and with both constraints. The prior images were planning CTs(pCT) deformable‐registered to the FBP reconstructions. Anatomy segmentations were done using atlas‐based auto‐segmentation (Elekta ADMIRE).Results:We observed small but consistent improvements in the Dice similarity coefficients of PL reconstructions over the FBP results, and additional small improvements with the added prior image constraint. For a CBCT with anatomy very similar in appearance to the pCT, we observed these changes in the Dice metric: +2.9% (prostate), +8.6% (rectum), −1.9% (bladder). For a second CBCT with a very different rectum configuration, we observed +0.8% (prostate), +8.9% (rectum), −1.2% (bladder). For a third case with significant lateral truncation of the field of view, we observed: +0.8% (prostate), +8.9% (rectum), −1.2% (bladder). Adding the prior image constraint raised Dice measures by about 1%.Conclusion:Efficient and practical adaptive radiotherapy requires accurate deformable registration and accurate anatomy delineation. We show here small and consistent patterns of improved contour accuracy using PL iterative reconstruction compared with FBP reconstruction. However, the modest extent of these results and the pattern of differences across CBCT cases suggest that significant further development will be required to make CBCT useful to adaptive radiotherapy.