bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐C‐214‐05: 2.5 MV Cone‐Beam Computed Tomography with Thick CsI EPID
Authors: Tang G , Moussot C , Morf D , Seppi E , Amols H 
Published: November 2011

Purpose: To evaluate the feasibility of CsI detector for low dose 2.5 MV cone‐beam computed tomography (MVCB). Methods: The new Varian TrueBeamTM at our center is equipped with a prototype non‐clinical 2.5 MV imaging system with a 9 mm thick cesium iodide (CsI) scintillator EPID. Both static portal radiographs and MVCB images can be obtained. The minimum dose per beam pulse or frame is ∼0.0025 cGy. Approximately 450 projections were collected at up to 9 frames/second in a full 360 degrees rotation that may take 60–90 seconds. MVCB scans of a RANDO phantom were acquired using 2.5 MV and 6 MV x‐rays, the latter taken with conventional EPID (aS1000, Varian Medical Systems). KVCB scans were also taken for comparative purposes. An acrylic phantom containing high‐Z inserts was imaged with all beams to assess image artifacts. Results: The new 2.5X prototype system required only ∼2.4–3.4 cGy to achieve clinically acceptable image quality in the head, thorax, and pelvis, while standard 6X MVCB required ∼26 cGy. Image quality approaching kVCB can be obtained with 2.5X MVCB using doses of ∼ 9cGy, although images acquired using 2.4 cGy were sufficient for bony alignment purposes. As expected, MVCB images in the head and thorax are superior to pelvis. In addition, the 2.5 MV imaging beam greatly reduces high‐Z image artifacts that can significantly perturb kV image quality. Conclusions: 2.5X MVCB with high quantum efficiency CsI detector can replace kVCB in most clinical situations at greatly reduced cost and fewer high‐Z artifacts. Unlike kV, treatment planning systems can easily incorporate MV dose into plan optimization. Further, patients having metallic implants (e.g. dental fillings, hip prosthesis, etc.) can benefit from MVCB due to its insensitivity to high‐Z materials and its ability to yield true electron densities for treatment planning.Research partially supported by Varian Medical Systems.
SU‐C‐110‐04: A Clinical Evaluation of a Novel Hybrid Amplitude‐Based 4DCT Sorting Algorithm: Impact on ITV Delineation
Authors: Bellon M , Glide‐Hurst C , Chetty I 
Published: November 2011

Purpose: The choice of sorting method used to genereate 4DCT image sets can affect image quality and target volume delineation. This study evaluated, in phantom and patient, the impact of a novel hybrid amplitude‐based (hAB) 4DCT sorting algorithm on the delineation of internal target volume (ITV), and results were compared with conventional phase‐based (PB) sorting .Methods: Eight phantom experiments were performed using respiratory motion platform programmed with simple ((1‐cos2), 5 second cycle) and complex (from RPM patient data) breathing curves with S‐I lung‐tumor excursion. 4DCT images were acquired, and corresponding datasets were sorted (10 phases) using both phase and hAB sorting algorithms. A retrospective study of nine early‐stage lung cancer patients were also reconstructed using both sorting algorithms, and maximum intensity projections (MIPs) were generated from each 4DCT dataset. ITVs for both phantom and patient data were auto‐contoured on each MIP. ITV volumes and centroids were compared between sorting algorithms. Results: For all phantom and patient studies, hAB produced smaller or equivalent ITVs than the PB approach. Average percent difference in delineated ITV volume was 5.2% (range: 0.0 – 13.5%) and 3.0% (range: 0.2 – 7.9%) for patient and phantom studies, respectively. For the patient study, the largest percent differences occurred when lateral or anterior‐posterior tumor motion was present. Average variation in centroid coordinates was < 1mm for all phantom and patient cases studied. The largest variation in ITV extent was expressed in the sup‐inf direction in the phantom study. Noticeable sorting artifact was observed for two phantom cases for both the hAB and PB sorted data Conclusions: This study demonstrates clinical application of a novel hAB 4DCT sorting algorithm. We have quantified the variation in ITV delineation stratified by sorting technique, and revealed situations which may increase the potential for the underestimation of full tumor volume extent encompassing motion.Conflict of Interest: Henry Ford Health Systems holds a research agreement with Philips Medical Systems
SU‐D‐BRB‐03: All‐Inclusive DOSXYZnrc Source for Monte Carlo QA of External Beam Radiotherapy
Authors: Alexander A , Renaud M , Seuntjens J 
Published: November 2011

Purpose: To extend the versatility and simplicity of external beam Monte Carlo (MC) methods within BEAMnrc/DOSXYZnrc with the introduction of a new universal DOSXYZnrc source for multi‐field simulations. Methods and Materials: A single DOSXYZnrc source, capable of simulating all types of external beam radiotherapy, was developed as an extension to the standard set of sources. The source incorporates dynamic movement of components such as MLC leaves, jaws, gantry, collimator and couch. This was achieved by coupling the field index between the BEAMnrc components with the field index of the DOSXYZnrc components through the LATCH variable, transferred from BEAMnrc to DOSXYZnrc via the phase space information. This allows the state of the accelerator (such as MLC leaves, jaw positions and angles of incidence) to be changed for each history, effectively simulating coupled time‐dependent geometries. The process for RapidArc is as follows. RapidArc fields are defined within the control points of the DICOM plan file. Each point defines a MLC pattern and gantry angle. Within the MC simulation, the MLC pattern was defined in BEAMnrc, while the gantry angles were defined in the new DOSXYZnrc source. Control points for Tomotherapy are defined with the XML and sinogram files. In addition, IMRT and conformal treatments such as SBRT, which are comprised of 1–7 beams, can be merged into a single simulation. For practical considerations, it is more efficient to run a single MC simulation than to manage the submission of multiple beams and recombining them afterwards. We tested the new source within the context of the MMCTP system.Results and Conclusion: This source has enabled MC plan verification of RapidArc and Tomotherapy and simplified the MC calculation of IMRT and SBRT into a single simulation for efficient QA. The new source adds much needed functionality to the existing set of DOSXYZnrc sources.
SU‐D‐BRC‐01: Multi‐Fraction Dose Distributions for Image‐Guided IMRT of Prostate: Impact on TCP and NTCP
Authors: Battista J , Johnson C , Turnbull D , Kempe J , Bauman G , Van Dyk J 
Published: November 2011

Purpose: IMRT of the prostate consists of multiple stages of treatment planning and dose delivery, each with inherent anatomical uncertainties. Differential filling of the bladder and rectum can displace the prostate during a course of treatment. The purpose of this study was to assess the effectiveness of adapting to these anatomical changes using various CT image‐guided adaptive (IGART) strategies. Methods: Our computer model is based on the Philips Pinnacle treatment planning system. A multi‐fraction simulation of 5‐field IMRT (76 Gy/35 fractions) yields the daily dose accumulation in individual tissue elements. Using megavoltage CT studies of 13 prostate cases, cumulated dose distributions are mapped onto the reference treatment plan. Total dose‐volume histograms are then processed to estimate the changes in tumor control probability (TCP) and normal tissue complication probability (NTCP) for various IGART scenarios. Results: Retargeting of the prostate generally maintains the intended TCP (typically 0.9 versus 0.8 with No Image Guidance) but is often associated with an enhanced risk of rectal toxicity (NTCP rises to 0.05 when Image Guidance is applied). This effect is due mainly to a systematic anterior shift caused by sag in the treatment couch (average 10mm). Without image‐guidance, this offset goes uncorrected, resulting in poorer coverage of the target with consistent avoidance of rectal exposure. Conclusions: Geometric repositioning without dose re‐planning is sufficient to maintain the intended TCP. IGART corrects for sag in the treatment couch and this results in greater risk of rectal toxicity, compared with no IGART. Smaller PTV margins could offset this effect, emphasizing the need for integrated image guided and intensity modulated delivery for optimal results. In the extreme, daily IMRT re‐planning based on in‐room imaging could exploit maximum benefits of this technology but this would require significantly more computing resources and streamlining of procedures at the treatment console.Research funding was provided by the Canadian Health Research Institutes and the Ontario Research and Development Challenge Fund (OCITS Project), with Philips Medical Systems as an industry partner.
SU‐D‐BRC‐03: Spatial‐Temporal PET‐CT Features for Predicting Pathological Response of Esophagus Cancer to Chemo‐Radiation Therapies
Authors: Tan S , Chen W , Lu M , Kim G , Feigenberg S , DˈSouza W , Suntharalingam M , Lu W 
Published: November 2011

Purpose: The purpose of this study is to develop new PET‐CT features for predicting the pathology response of esophagus tumor to chemo‐radiation therapies, and to compare their discriminant power with SUV‐max and SUV‐peak. Methods: Fifteen patients with locally advanced esophagus cancer and treated with tri‐modality therapies were studied. All patients underwent a Pre‐treatment and a Post‐treatment PET/CT. The Pre‐ and Post‐ CT images were first aligned with a rigid registration constrained in the chest region. All images were then projected into the Pre‐PET coordinate. Two different tumor regions of interest (ROI‐SUV2.5 and ROI‐SUVPeak) were produced. Various features capturing tumor shape, texture and intensity information were extracted, resulting in a total of 432 features for each patient. Receiver operating characteristic analyses were performed to investigate and compare the discriminant power of each feature. The ground truth was set to be the pathological response in the surgical specimen. Finally, trend analysis was conducted to examine whether a tumor is more likely a responder as the value of a feature increases or decreases. Results: Five among all 432 features have higher discriminant power than that of SUV‐max and SUV‐peak. These include two shape features, one intensity feature, one texture feature and one shape plus intensity feature. Among them, the Decline of Total Glycolytic Volume feature is extracted from the Diff‐SUV image. All five features were based on the larger tumor region ROI‐SUV2.5. Conclusions: Results demonstrated that shape, texture and intensity information are all important for predicting esophagus tumor pathological response to chemo‐radiation therapies. Integrating both spatial and temporal information is also important. Features based on a larger tumor region seem to be better than those based on a single point or a smaller tumor region.This work is supported in part by NIH 1R21CA131979.
SU‐D‐BRC‐05: Characterizing Therapy‐Induced Brainstem Injury and Recovery with Serial Diffusion Tensor Imaging
Authors: Hua C 
Published: November 2011

Purpose: To characterize therapy‐induced changes in normal‐appearing brainstems of childhood brain tumor patients by serial diffusion tensor imaging (DTI). Methods: We analyzed sequential DTI of 20 brain tumor patients, aged 4–23 years, with normal‐appearing brainstems included in the radiation treatment fields. Prescribed tumor doses ranged from 54 to 59.4 Gy. Parametric maps of fractional anisotropy (FA) and apparent diffusion coefficient (ADC) were computed and registered to three‐dimensional radiation dose data. Volumes of interest included corticospinal tracts, medial lemnisci, and the pons. Serving as an age‐related benchmark for comparison, DTI studies from 20 healthy volunteers, aged 6–25 years, were included in the analysis. Results: The median DTI follow‐up was 3.5 years (range, 1.6–5.0 years). The median mean dose to the pons was 56 Gy (range, 7–59 Gy). Three distinctive patterns of temporal changes in FA and ADC were observed in the pons: (1) a stable or normal developing time trend similar to those observed in healthy children, (2) initial deviation from normal with subsequent recovery, (3) progressive deviation without evidence of complete recovery. In this group of patients without severe brainstem necrosis, maximal decline in FA often occurred 1.5 to 3.5 years after the start of radiation therapy. A full recovery time trend could be observed within 4 years. Patients with incomplete recovery often had a larger decline in FA within the first year. Radiation dose alone did not predict long‐term recovery patterns. Conclusions: Longitudinal DTI analysis revealed variation among individual patients in diffusion properties of brainstems reflecting therapy‐induced white matter injury and recovery. Early response in brainstem anisotropy may serve as an indicator of the recovery time trend over 5 years following radiation therapy. Attention should be given to patients with pronounced early changes since DTI suggested their recovery was slower and less complete than other patients.Acknowledgement: NIH grant HD049888.
SU‐D‐214‐06: Designing Simulators for Studying Medical Physics: From CT Imaging to Radiotherapy Treatment Planning and Quality Assurance
Authors: Kum O , Choi W , Park K , Chung Y , Han Y 
Published: November 2011

Purpose: Designing simulators for studying medical physics ranging from CT imaging to radiotherapy treatment planning and quality assurance will be very valuable for students, educators, and medical professionals to learn and teach radiation physics principles and to perform virtual practicing of the patient diagnosis and treatment based on physical principles. Methods: A Monte Carlo method is the best to simulate the radiation transport phenomena. Thus, in this project, we used our in‐house Monte Carlo code, PMCEPT code, to simulate directly the interactions between the radiation and the patient body. However, for better understanding of the complex physical phenomena involved in the radiation interactions with matter, some augmenting novel computational approaches such as ray‐tracing and medical image segmentation algorithms are included. Specifically, fast ray tracing method is useful for better understanding the CT images and the near future IGRT treatment planning. For the real time simulations, parallel algorithms adaptive to PC cluster and GPU‐accelerated algorithms were employed. Results: The CBCT simulator with a set of ray beams emitting towards every pixel center of the detector from the X‐ray source was developed. Semi‐automatic segmentation of CT image using watershed algorithm and graphical user interface was developed for analyzing the DICOM data to provide ASCII data file which is readable. The external beam accelerator operated with keyboard and mouse was developed. Conclusions: The important benefits of these virtual simulators may be the replacement of the conventional laborious procedures which are required for the expensive hardware simulator units, the efficiency increment, the accuracy improvement of radiation treatment procedure, and the cost reduction in terms of time and physical patientˈs presence. A more extensive assessment of the efficiency improvement provided by these simulators is still under investigation and will be presented in future articles.This research was supported by BSR program through NRF funded by the MEST (grant # 2010‐0003983)
SU‐D‐220‐03: Inter‐ and Intra‐Fraction Verification with Integrated On‐Board Xray CBCT and 3D Ultrasound Imaging: A Feaibility Study
Authors: Xia P , Lachaine M , Kazanzides P , Iordachita I , Stephans K , Wallace J , Herman J , Wong J 
Published: November 2011

Purpose: CBCT and 3D Ultrasound (3DUS) provide complementary information on bony landmarks and soft tissues, particularly for abdominal sites. Furthermore, 3DUS can potentially track intra‐fractional motion of soft tissues. In this study, we investigate the feasibility of integrating these two modalities to provide a comprehensive image guidance procedure that corrects for both inter‐and intra‐fractional motion. Methods: The ultrasound probe will be operated under robotic control to enhance reproducible placement. We investigated the effect of potential CT artifacts caused by the probe and the subsequent effect on treatment plan dose calculation. We then measured the effect on ultrasound image quality due to an 18 MV radiation beam in close proximity to the probe. A phantom was constructed by imbedding markers in gel. The reproducibility of the marker positions under controlled repeat compressions, mimicking robotic placement, was measured. The effect of removing a beam to allow probe placement during treatment was studied by comparing optimized liver plans with or without the specific beam. Results: CT artifacts associated with probe placement affected treatment planning dose by 20%. The artifacts can be avoided with a CT‐compatible model probe. Radiation dose delivered 1 cm from the probe did not affect the ultrasound image quality. When the same compression was used to compress the gel phantom, the positions of the fiducial markers were reproducible to within 0.3 mm. The reoptimized liver plan with the omission of one beam was not noticeably different from the original plan. Conclusions: On‐board x‐ray CBCT is highly effective for patient setup based on bony landmark. 3DUS is a non‐invasive, non‐ionizing means to continuously monitor soft tissue motion. Our studies indicate that it is feasible to combine both systems during treatment. Their integration, enhanced by robotic repositioning, provides a highly complementary approach for IGRT of soft tissue sites in the abdomen.Martin Lachaine is the Director of Research at Resonant Medical.
SU‐D‐220‐05: Dynamic Ultrasound Evaluation of Radiation‐Induced Vocal Cord Injury in Head and Neck Cancer Patients
Authors: Chen H , Beitler J , Tridandapani S , Yoshida E , Walter C , Liu T 
Published: November 2011

Purpose: Curative radiation for oral cavity, oropharyngeal, hypopharyngeal and nasopharyngeal cancers can injure the vocal cords which can adversely affect speech and quality of life. Vocal cords are difficult to image with conventional MRI, CT or ultrasound. Currently, no imaging technique is available in the clinic to visualize and evaluate such injury. The purpose of this study is to develop a dynamic ultrasound technology to quantify radiation‐induced vocal cord injury. Methods: Eight healthy volunteers and five post‐radiation patients were enrolled under IRB approval. Each participant was scanned using a clinical ultrasound scanner (Sonix Touch) with a 14‐MHz linear array transducer. The ultrasound probe was placed in the transverse plane approximately parallel to the vocal foldˈs mucosal wave propagation. Each participant was asked to phonate the vowel sound “a” and sustain the phonation for 5 seconds while 315 dynamic (consecutive) ultrasound images of the vocal fold were recorded. Vocal cord vibration patterns were obtained through these consecutive images. Vibration frequency and 2‐D dimensions were computed to measure vocal cord performance. Results: The vocal cords were clearly visualized using dynamic ultrasound in all participants. Vocal cord vibration patterns of the healthy volunteers revealed smooth sinusoidal wave propagation. In contrast, the patterns of post‐radiation vocal cords presented irregular wave propagation. M‐mode videos parallel and vertical to vocal cord vibration direction were generated. The vocal cord vibration pattern was most disrupted in the patient with clinically‐identifiedvocal cord injury. Aliased frequency estimated from M‐mode video could be used to distinguish damaged vocal cord injury from normal vocal cord. Conclusions: In the effort to develop a noninvasive imaging technique for evaluating vocal cord injury post radiotherapy, we identified dynamic ultrasound as a promising tool. Ultrasound is safe, simple, and cost‐effective. This study demonstrated its feasibility in imaging the vocal cords and quantifying the vocal cord condition.Part of this research is supported by Susan Komen Grant (KG101373).
SU‐D‐220‐06: Non‐Contact (Air‐Coupled) Ultrasound Applied to Cortical Bone Phantoms
Authors: Ganezer K , Halcrow P , Bulman J. 
Published: November 2011

Purpose: The purpose was to take the first steps towards applying Non‐Contact Ultrasound (NCU) to the in‐vivo monitoring of osteoporosis and to skeletal quantitative ultrasound imaging (QUS) using cortical bone. The goals of this study focused on the possible advantages of NCU such as its lack of reliance on a technologist and a layer of acoustical coupling gel, its ability to use methods similar to those in x‐ray imaging, and the likely reduction in statistical and systematic errors. This project pursued additional applications of NCU beyond its usage in assessing the severity of third degree burns. Methods: An NCU imaging system, a pair of broadband, 1.5 MHz, non‐contact transducers, and cortical bone phantoms were used to determine bone mineral density (BMD), speed of sound (SOS), integrated acoustical response (IR), and ultrasonic transmittance. Air gaps of greater than 3 cm, two transmission and reflection paths, and a digital signal processor were used to collect data from phantoms of nominal mass density and (BMD) from 1.17 g/cm3 to 2.25 g/cm3 and from 0 g/cm3 to 1.7 g/cm3. Results: Good correlations between known BMD and measured SOS, IR, and transmittance were obtained for all 14 phantoms. Repeated measurements of the speed of sound (SOS), thickness, and IR for the phantom set show a small variation of plus or minus 1–2 %. These NCU data were shown to be in agreement with similar results from contact ultrasound to within 1–2%. Attenuation images of cortical bone phantoms showed discernible differences as a function of BMD. Conclusions: The results suggest that NCU might find additional applications beyond burn assessment. Since the NCU and conventional gel‐coupled measurements yield similar results, our air‐coupled methods might be able to reach levels of accuracy close to those attained with gel, while avoiding the disadvantages of contact.The authors would like to express their gratitude to the National Institutes of Health who supported this research through Grant Number GM 08156‐22 and its supplements which included funding for obtaining an NCU system and other ultrasound hardware used in this study.