bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐GG‐J‐03: Emission Guided Radiation Therapy System: A Feasibility Study
Authors: Mazin S , Nanduri A , Pelc N 
Published: August 2010

Purpose: To evaluate the feasibility of a combined PET‐Linac system for real‐time guidance of radiation therapy for tumors that move due to respiration. Method and Materials: We are developing a treatment system that will simultaneously deliver radiation during PET acquisition. A method to compensate for respiratory motion will be to deliver radiation beam‐lets along individual PET lines‐of‐response (LOR's) as they are detected. The system involves rotating a radiation source and PET detectors on a gantry while dynamically controlling a binary multi‐leaf collimator to deliver the beam‐let responses in a 2D helical mode. Simulations were conducted using GATE to model 300 seconds of PET list‐mode acquisition of a ‘hot’ 3 cm diameter tumor exhibiting 3.7 second periodic 2 cm peak‐to‐peak motion in a ‘warm’ background. A 5 cm planning target volume (PTV) was used as a filter to reject LOR's that did not intersect this volume. LOR's that intersected the PTV and whose timestamps were within a 500 ms cutoff window were responded to. A voxel‐based Monte Carlo simulation package was used to model the resultant dose distributions comparing the emission guided (EGRT) method with uniform coverage of the PTV. Results: Composite dose volume histograms were calculated using 10 phases of the motion cycle. Dose to the non‐tumor volume was normalized to the same mean value for both scenarios. The EGRT approach exhibited a non‐uniform dose distribution to the tumor compared to uniform PTV coverage. However, even with the non‐uniformity, there was a 30% relative increase in minimum dose to the tumor volume for the EGRT approach. Conclusion: Although non‐uniform dose delivery to the tumor volume needs to be addressed, the feasibility of using PET to guide radiation delivery in real‐time has been demonstrated.Conflict of Interest: SRM and ASN are co‐founders of a company commercializing emission guided radiation therapy.
SU‐GG‐J‐09: Effective Tracking of Intrafractional Organ Motion Due to Breathing Using a Siemens 160 MLC
Authors: Krauss A , Nill S , Oelfke U 
Published: August 2010

Purpose: In this work we demonstrate effective tracking of highly irregular breathing motion using a dynamic Siemens 160 MLC™ and a neural network predictor to compensate for the relatively large end‐to‐end system latency of 500 ms. Method and Materials: One‐dimensional breathing patterns were recorded from several radiotherapy patients using the ANZAI pressure belt system. The pressure belt signal was reproduced by a programmable phantom, which has embedded electromagnetic transponders for target localization and tracking (Calypso® Medical Technologies, Inc.). The aperture of a Siemens 160 MLC™ was adapted in real‐time to the target position provided by the Calypso system. Due to the highly irregular nature of breathing motion, advanced prediction methods are required to accurately compensate the system latency. We therefore implemented a feedforward neural network predictor. The network was trained on a 120 second sample of breathing data which preceded the data that was used for the subsequent tracking experiments. The geometric tracking accuracy was determined through an analysis of portal images acquired during radiation delivery. A metal ball attached to the phantom allowed the reconstruction of the phantom trajectory from the portal images. Tracking errors were quantified as the difference between the phantom trajectory and the geometric centroid of the radiation field on the portal images. Results: In an offline cross‐validation study, we could identify a common set of model parameters of the neural network, which yielded good prediction performance for all the breathing patterns under consideration. The analysis of the images acquired during the tracking experiments yielded root mean squared tracking errors of 1.21 mm, 1.29 mm and 1.58 mm for the three investigated motion patterns. Conclusion: In spite of the relatively large system latency, we achieved highly accurate MLC tracking for irregular breathing patterns.Conflict of Interest: Supported by Siemens Healthcare OCS and Calypso Medical Technologies, Inc.
SU‐GG‐J‐14: Failure Mode and Effect Analysis (FMEA)‐Based Quality Assurance for Dynamic MLC Tracking Systems
Authors: Sawant A , Dieterich S , Svatos M , Keall P 
Published: August 2010

Purpose: Effective QA for newly introduced radiotherapy technology has received increased attention within the radiotherapy community and the general public. This work aims to develop and implement a FMEA‐based quality management (QM) framework for dynamic MLC (DMLC) tumor tracking systems. Methods: A systematic FMEA was performed for a prototype tumor tracking system that uses the Calypso system for position monitoring and a DMLC for real‐time beam adaptation. A process tree of DMLC tracking delivery was mapped and potential failure modes were identified. For each failure mode, a risk probability number (RPN 1:1000) was calculated from the product of the probability of occurrence, severity of effect and detectability of failure. Based on the insights obtained from FMEA, commissioning and QA procedures were developed to check (i) coordinate transformation, (ii) system latency, (iii) delivery accuracy, (iv) delivery efficiency and (v) system response to error conditions. Results: Failures modes with RPN ≥ 20 were: delivery accuracy, efficiency and data communication integrity. These were recommended to be tested monthly. Failure modes with RPN < 20 were: coordinate transformation, latency error and target out‐of‐range error. These were recommended only during comprehensive testing e.g., commissioning, annual testing and after major software/hardware upgrades. The total time taken for monthly QA was ∼35 minutes while that taken for comprehensive testing was ∼3.5 hours. Conclusion: FMEA proved to be a powerful and flexible tool to develop a QM framework for DMLC tracking. We conclude that the use of FMEA ensures efficient allocation of valuable clinical resources because the most critical failure modes receive the most attention. Finally, consistent with the goals of FMEA, this framework can serve as the basis of a dynamic QM program that is continuously updated with increasing intra‐ and inter‐institutional experience.Conflict of interest: This work was partially supported by Varian and Calypso
SU‐GG‐J‐96: Statistical Analysis of the Correlation between Breathing Characteristics with Patient Parameters
Authors: Guo B , Vazquez L , Xu X , Shi C 
Published: August 2010

Purpose: Breathing curve of lung patient is an important feature for tumor tracking and 4D delivery. The correlation of external breathing curve characteristics with internal tumor location and with the biological features of the patient is of large interest. In this study, we are aiming to propose a method for analyzing the parameters of breathing curves and study the correlation of breathing characteristics with features of patients. Method and Materials: Piecewise cosine functions were used to fit breathing curves and determine the amplitude, period and baseline of each breathing cycle. Mean value and standard deviation of amplitude, period and baseline over the breathing curves were determined as the “characteristics” of a breathing curve. Statistical analysis was performed to correlate these characteristics with patient parameters including age, gender and tumor site base on a total of 305 breathing curves from 158 patients acquired from Real‐time Position Management (RPM) system. Pearson correlation method was used to determine the correlation of age with breathing parameters. Two‐sided unpaired t‐test was used to study whether gender or presence of tumor in lung affect the breathing characteristics significantly. Results: Age has no correlation with breathing characteristics studied. Gender affects both the mean (p = 0.971) and standard deviation (p = 0.425) of breathing period. The effect of gender on breathing amplitude or baseline variation was insignificant. Presence of lung tumor affects the mean amplitude (p = 0.317) and period (p = 0.384). The baseline variation was also affected slightly (p = 0.860). But the irregularity of amplitude and period was irrelevant to the tumor locations. Conclusion: Statistical analysis of large number of breathing curves revealed that parameters of patient may affect the breathing curve statistics thus affecting the management of tumor motion in radiation therapy.Conflict of interest: Research supported by grant NIH/NLM R01LM009362
SU‐GG‐J‐153: Voxel‐Based Phenomenological SUV‐Dose Response Model for the Human Parotid Glands
Authors: Cannon B , Tucker S , Chambers M , Garden A , Martel M , Schwartz D , Dong L 
Published: August 2010

Purpose: The goal of this study is to evaluate SUV as an imaging biomarker of parotid function following radiotherapy (RT) and to develop a phenomenological model of SUV‐dose response, enabling prediction of the biomarker prior to RT. Method and Materials: As part of an ongoing study, patients (n = 8) with head and neck cancer (HNC) had 18F‐FDG PET/CT studies performed before (within 30 days) and following RT (∼50 days). In addition, resting and stimulated whole mouth saliva was collected. Next, a deformable image registration algorithm was utilized to map parotid contours from planning CT (PCT) images to pre‐ and post‐RT PET/CT studies, separately. Mean SUV was then calculated for the parotid glands at both time points and compared to collected saliva. The SUV‐dose response relationship was assessed in a separate cohort (n = 60) also treated for HNC. Pre‐ and post‐RT PET/CT images were deformably aligned to PCT images to achieve correspondence between SUV and planned dose. SUV response was then modeled using a single parameter, incorporating planned dose and pre‐RT SUV; defined as metabolic dose. Results: Post‐RT stimulated saliva and SUV decreased (59% and 20%, respectively) in seven patients. For one patient, stimulated saliva and SUV increased (14% and 11%, respectively). Fractional SUV correlated significantly with xerostomia grade, P < 0.01 and Spearman's ρ = −0.964. A second order polynomial provided an adequate fit to the log transformed SUV‐dose response curve, adjusted R2 = 0.95. Post‐RT SUV was predicted within 3% for an exemplary patient, but overestimated (50%) in the worst case. Conclusions: Pilot data suggest that SUV is significantly correlated with parotid saliva output. Furthermore, the feasibility of predicting reductions in SUV, prior to treatment delivery, has been demonstrated.Conflict of Interest: Research partially sponsored by Varian Medical Systems.
SU‐GG‐T‐200: Comparison of a Novel Transmission Detector to a Standard Measurement Technique for Patient IMRT Quality Assurance
Authors: McCurdy B , Malkoske K 
Published: August 2010

Purpose: A new measurement‐based, pre‐treatment IMRT composite quality assurance (QA) procedure was compared to a standard QA method. The standard QA method consisted of delivering the treatment to a cuboidal IMRT phantom containing dose measuring media. This standard measurement employed Gaf‐chromic film sheets for relative dosimetry and an ion chamber for absolute dosimetry. The new method examined here used a novel transmission detector measurement (IBA Dosimetry) designed for in vivo patient dosimetry. However, before in vivo application, we compare to our standard QA method, which is the focus of this work. Method and Materials: Treatment plans for ten previously‐treated, head and neck IMRT patients were used. All treatment plans were QA'd with the standard method at the treatment beam angles. Measurements with the transmission detector (an array of 1600 IC's) were also performed at the treatment beam angles. The COMPASS software (IBA Dosimetry) converts these 2D‐array measurements to incident fluence, and then forward calculates dose in a patient model (ie. CT data). In this work the patient model was a cuboidal shaped solid‐water IMRT phantom (MedTec). Absolute doses were compared using isocentre location for the COMPASS/planning system, and a low dose gradient point location for the IC/planning system comparison (near isocentre, but not necessarily due to alignment needs during measurement). Results: On average, the standard QA method results for absolute dosimetry were different by 1.4±1.8% compared to the planning system (measured above planning system). On average the transmission detector based QA method results for absolute dosimetry were different by 0.3±1.6% compared to the planning system (measured above planning system). Conclusion: QA results using the COMPASS software with the transmission detector were comparable to the standard QA method.Conflict of Interest: CancerCare Manitoba has a collaborative research agreement with IBA Dosimetry, although there is not direct financial support.
SU‐GG‐T‐351: Dosimetric Evaluation of an Implantable DVS‐HFT Dosimeter for Hypo‐Fractionated Radiation Treatment
Authors: Ding G , Coffey C , Malcolm A 
Published: August 2010

Purpose: To evaluate the dosimetric accuracy and reproducibility of an implantable DVS‐HFT dosimeter for hypo‐fractionated radiation treatment in stereotactic radiotherapy. Method and Materials: The dosimeters are factory calibrated to read within the range of 340–950 cGy per fraction. Communication from the detector to the reading device is achieved telemetrically. Two sets of dosimeters were studied in a phantom and one set is implanted in a prostate cancer patient treated with five fractions. The planned doses to detectors were calculated based on CT images. The calculated doses were validated with ionization chamber measurements in the phantom. Both static and IMRT beams were studied. The uncertainty of dosimeter reading was estimated by Results: In the phantom studies, the uncertainty of daily readings were found to be from −0.1 to −4.9% (with a mean value of −1.6%) and from +1.4 to +4.8% (with a mean value of +2.5%) for five daily doses of 700 cGy delivered by static and IMRT beams respectively. For the dosimeters implanted in the prostate cancer patient, the daily discrepancies between dosimeter‐1 readings and calculated doses of 767 cGy range from −8.2% to +4.0% (with a mean value of +2.0%) during five fractions. However, the discrepancies of dosimeter‐2 implanted in a region with high dose gradients (calculated dose of 180 cGy) range from −4.3% to +35.0% (with a mean value of +3.4%). Conclusion: The accuracy of the DVS‐HFT dosimeter is shown to be within the manufacture stated uncertainties of < 5.5%. The study demonstrates that the dosimeter may be an effective tool to determine the actual dose delivered to treatment targets as well as organ at risk. The information obtained can be utilized to study actual dose fluctuations of daily treatment.Conflict of Interest: Two sets of dosimeters used in phantom study were provided by Sicel.
SU‐GG‐T‐555: Dosimetric Effect of Couch Position Variation for Intensity Modulated Arc Therapy
Authors: Popple R , Duan J , Shen S , Wu X , Brezovich I 
Published: August 2010

Purpose: To investigate the dosimetric effect of variation in treatment couch positioning relative to isocenter for intensity modulated arc therapy. Method and Materials: 5 RapidArc (Varian Medical Systems, Palo Alto, CA) treatment plans (2 head and neck, 2 prostate, and a lung) were selected that were calculated including the treatment couch with the support rails in the lateral position. Calculations were done for the couch positioned ±3 cm relative to isocenter and for the support rails in the center position. Dose‐volume histograms were compared for the targets and critical structures. Results: For ±3 cm shift, the largest deviation of the minimum, maximum, and mean target doses was 0.2%. For the critical structures, the largest deviation of the minimum, maximum, and mean doses was 0.6%, 0.4%, and 0.4%, respectively. The largest deviations occurred for the head and neck plans. Excluding the head and neck plans, the largest deviation of the minimum, maximum, and mean critical structure doses was 0.2%. For the support rails in the center, largest deviation of the minimum, maximum, and mean target doses from the planned lateral rail position was 1.6%, 1.6%, and 1.1%, respectively. For the critical structures, the largest deviation of the minimum, maximum, and mean doses from the planned lateral rail position plan was 0.9%, 3.8%, and 1.2%, respectively. Conclusion: The effect of couch shifts of up to 3 cm relative to isocenter is small. For positioning systems indexed to the treatment couch, the daily variation of the couch position can be safely ignored. However, for positioning systems that are independent of the couch, care must be taken to limit the daily deviation. The support rail positions have a more significant effect than couch position relative to isocenter.Conflict of Interest: First author has a sponsored research agreement with Varian.
MO‐SAM‐201B‐01: Optimizing CT Dose and Image Quality for Different Patient Sizes
Authors: McNitt‐Gray M 
Published: August 2010

CT technology has improved dramatically over the past decade and its clinical utilization has increased significantly as well. While CT can yield exquisite descriptions of anatomy that were not previously possible (at least not with noninvasive techniques), its increased utilization has led concerns over radiation dose; CT has now been identified as the single largest contributor to medical radiation dose to the population and accounts for approximately 50% of medical exposure. Methods to reduce radiation dose have been the focus of all stakeholders (medical physicists, technologists, radiologists, manufacturers and regulators). Reducing dose while maintaining acceptable image quality can be complex and this is made even more complex when considering patients of different sizes.This talk will first describe methods currently used, and some being developed, to estimate radiation dose in patients. This will include a discussion of measurement techniques as well as Monte Carlo simulation‐based techniques. Specific attention will be paid to the differences in dose to patients of different sizes ranging from pediatric patients to obese adult patients. Tradeoffs in image quality and radiation dose will also be described in this context as well. Radiation dose reduction techniques, including a review of various tube current modulation schemes currently being employed will also be described. The effect of these dose reduction methods on both radiation dose and image quality will be discussed, again with attention to how they can be deployed with patients of different size.Learning Objectives:1. Understand how radiation dose for CT studies is currently estimated2. Understand the trade‐offs of dose and image quality, especially for large (obese) patients and in pediatric patients3. Review of the manufacturers' dose modulation methods and how these affect dose in different patients
MO‐D‐201C‐03: Advances in MR: State of the Art Today and Future Directions — MR‐Guided Interventions
Authors: Stafford R 
Published: August 2010

Image‐guidance of minimally invasive interventions for diagnosis and therapy has been a rapidly evolving field, particularly with respect to incorporation of increasing advanced imaging equipment for the planning, targeting, monitoring and assessment of procedures. Traditionally, these vascular, therapeutic and biopsy procedures have been carried out using fluoroscopy, ultrasound or CT. MRI is an inherently 3D, non‐ionizing imaging modality offering multiple soft‐tissue contrast mechanisms as well as functional imaging in a single locale. Because of these unique properties, use of MRI for guidance of interventions has been of growing interest in recent years for a number of procedures requiring stereotactic localization and planning or real‐time image guidance and monitoring, such as biopsy and thermal therapy delivery.However, despite the recent proliferation of commercially available hardware and software solutions for MR guided procedures, integration of MRI into an intraoperative and interventional environment remains a challenge. Because of the cost associated with equipment acquisition and siting, careful attention should be paid to specifying the MR system as well as the location of the facility. The specification of hardware and software, as well as the layout of the suite, strongly influence workflow and domain of possible procedures that can be realistically performed in the suite. Last, but certainly not least, the safety of patients and staff working in the MR environment must be considered and programs put in place to continuously educate staff who work in these suites.This talk aims to provide an overview of MR‐guided interventional procedures which are currently performed clinically on high‐field (≥1.5T) cylindrical bore systems with an emphasis on the potential for guidance of thermal ablative therapies. Illustrations of the use of MRI for planning and targeting lesions as well as monitoring and assessing thermal therapy delivery (i.e., cryotherapy and laser ablation) will be presented and challenges associated with these procedures discussed.Learning Objectives:1. Understand some of the enabling technology facilitating MR‐guided interventions as well as be able to identify challenges and safety concerns.2. Understand some of the tradeoffs in MR imaging of tumors for treatment planning, targeting, real‐time monitoring and post‐therapy assessment of thermal therapy.
MO‐D‐201B‐02: Distributed X‐Ray Source Development
Authors: Frutschy K , Neculaes B , Inzinna L , Mani V , Caiafa A , Reynolds J , Zou Y , Zhang X , Gunturi S , Cao Y , De Man B , Roffers R , Lounsberry B , Pelc N 
Published: August 2010

This work is funded in part by NTH grant R01EB006837 and General Electric Global Research. Distributed x‐ray sources have unique capabilities, which can enable break‐through medical imaging system performance. In particular, the distributed x‐ray source or “multisource” from GE has high instantaneous power, fast source switching, consistent focal spot sizes, large angular coverage, and high reliability [1]. This multisource is scalable from 1 to 2 rows of sources with source spacing in each row at 25mm currently with potential reduction down to 10mm. The multisource is being scaled up from 8 to 32 sources for the Inverse Geometry Computed Tomography (IGCT) application [2,3], which offers up to 70% x‐ray dose reduction, cone‐beam artifact reduction, and higher temporal resolution compared to conventional CT systems. Another multisource application is digital breast tomosynthesis (DBT). Today's DBT systems rely on physically moving a conventional x‐ray source over an arced path to obtain views at the required angles. A multisource not only eliminates mechanical motion and provides a faster scan, it also allows for multiple x‐ray spectrums (W, Rh, Re) at interleaved positions. Lastly, an x‐ray multisource enables vascular surgeons to see a real‐time 3D view of an interventional tool inside the blood vessels that they are navigating through. The ability to adjust electron beam current for each source (i.e, virtual bow‐tie) provides the precise amount of x‐ray dose required at each view for a particular patient's size thus eliminating excess dose in both IGCT and vascular tomography. This paper summarizes the current multisource development work, challenges, and application benefits.Learning Objectives:1. understand x‐ray multisource architecture and performance2. understand medical imaging system benefits from x‐ray multisource