bluuebunny/crossref_metadata_2025_split huggingface dataset:
MO‐FF‐A1‐01: Fluoroscopic Verification of Intensity‐Modulated Rotational Arc Therapy Delivery
Authors: Yi B , Han‐Oh Y , Lerma F , Berman B , Yu C 
Published: April 2010

Purpose: Intensity modulated rotational arc technique requires verification of leaf positions, gantry angle and dose rate in the entire arc. This study shows how to achieve this with a detailed verification of Varian RapidArc using a fluoroscopic electronic portal imaging device (EPID). Materials and Methods: Three Rapid Arc plans (prostate 1, whole pelvis 1, and head and neck 1) are delivered on a Triology linac (Varian Medical Systems, CA). During delivery, approximately 600 fluoroscopic portal images are acquired (∼8 images/s) per arc with a PV‐aS1000 EPID, without use of secondary phantoms or blocks. Each leaf position of each gantry angle is calculated from the acquired EPID images offline. Gantry angle information of each portal image is acquired from the dynalog file generated during beam delivery. Leaf positions from the dynalog file are compared to scheduled positions from the DICOM RT plan file. Results: Online EPID image acquisition of Rapid Arc delivery is prompt, involving extension of the EPID system and beam delivery time. The measurement error depends on the displacement of EPID system relatively to the center of rotation, which is only 1mm–1.5 mm. Offline analyses show the accuracy of leaf positions for static leaf and gantry field are better than 1 mm. More than 98.5% of leaf sequences exhibit less than 3mm deviations, 83 % show 2mm and 56% for 1mm. Conclusions: Position of each leaf of each gantry angle for Rapid Arc delivery is verified within 1 mm accuracy with fluoroscopic portal images. Use of fluoroscopic EPID images can be considered as a practical QA tool for the verification of the Rapid Arc delivery.This study is partially supported by Varian Medical Systems.
MO‐FF‐A1‐02: Calibration of a Novel 4D Diode Array for IMRT and VMAT QA
Authors: Yan G , Lu B , Kozelka J , Simon W , Liu C , Li J 
Published: April 2010

Purpose: To develop calibration procedures for a novel 4D diode array for IMRT as well as arc therapy quality assurance (QA). Method and Materials: A novel 4D diode array (ArcCHECK) was designed for rotational therapy QA. Its cylindrical and isotropic design presents a consistent detector image in beam's eye view for all gantry angles. Signals were acquired every 50 ms, allowing for real‐time per‐beam QA as well as measuring composite dose distributions. An efficient calibration procedure was developed to obtain diode sensitivity and directional response dependence with one full gantry rotation. In this process, each diode was in turn irradiated under the same beam condition on beam central axis. The directional response was obtained using TPS‐calculated beam profiles, which were validated in rectangular geometry. A real time algorithm to derive beam angle based on beam edge back projections was developed to apply the corresponding directional response factors. Its clinical application for IMRT QA was demonstrated with 17 IMRT head and neck beams delivered with planned beam angles. Measured dose distribution was compared to TPS calculation in three dimensions with %diff and distance‐to‐agreement analysis. Its feasibility for VMAT QA was investigated with a prostate conformal arc plan. Results: For the IMRT beams, average passing rate was 94.3%±2.1% and 99.6%±0.8% with 1%/2mm and 1%/3mm, respectively. For the conformal arc plan, the passing rate was 97.7% with 1%/2mm and 100% with 1%/3mm. Conclusion: An efficient calibration procedure was developed to obtain both the diode sensitivity and directional response dependence. Real‐time gantry angles were derived accurately based on beam edge back projections, which were used to apply directional response factors. Excellent agreement with TPS calculation was achieved for both IMRT and VMAT plans. ArcCHECK is an efficient and valuable tool for both IMRT and VMAT QA.Research sponsored by Sun Nuclear Corporation.
MO‐FF‐A1‐04: Toward a True Real‐Time in Vivo Dosimetry System Using Plastic Scintillators
Authors: Archambault L , Briere T , Poenisch F , Beaulieu L , Beddar S 
Published: April 2010

Purpose: Plastic scintillation detectors (PSDs) have shown great promise for offline applications such as IMRT QA. Because of their fast response and high sensitivity they could also be used as in vivo detectors. In this work we present and validate a PSD system designed for multi‐probe in vivo measurements with an electron‐multiplying CCD for real‐time photodetection. Method and Materials: The detectors were built with a dose sensitive volume of 0.4 cubic millimeters. Individual PSDs were assembled in modular detector patches each containing 5 closely packed detector elements. Continuous dose readings were performed every 150 ms (1.5 cGy) with a dead time of less than 0.3 ms between consecutive readings. We first studied the signal‐to‐noise ratio for different electron multiplication gain factors. We then analyzed the precision and accuracy of the detectors in acrylic and anthropomorphic pelvic phantoms. Results: The PSDs were found to be compatible with two clinical models of rectal balloons and could easily be inserted into the anthropomorphic phantom. A twofold increase in signal‐to‐noise ratio was seen by setting the electron‐multiplication gain factor to 40 therefore making near real‐time dosimetry feasible. Under calibration conditions, the PSDs agreed with ion chamber measurements to 0.08%. Precision was a function of the total dose delivered, ranging from 2% at 2 cGy to 0.4% at 200 cGy. Conclusion: We have shown PSD read in 150 ms with high accuracy and precision. We have also shown that these detectors can be mounted on different types of rectal balloons therefore transforming these clinical devices in dose detectors without modifying current clinical standard of practice and care. Real‐time monitoring of the dose delivered close to the rectum during prostate treatments will be invaluable to protect this sensitive normal structure while keeping small margins around the prostate.Supported by the NCI (1R01CA120198‐01A2)
TU‐SAM‐304A‐02: Clinical Considerations of the ACR MRI Accreditation Program
Authors: Branham T 
Published: April 2010

In October, 2008, the ACR MRI Accreditation Program was updated to a more flexible, modular process. The ACR MR Accreditation process includes the initial application, and the submission of clinical and phantom images and forms.The medial physicist plays a critical role in the accreditation process, along with the lead technologist and the supervising radiologist. A team approach is necessary to ensure that all information is accurate and appropriate for the examinations (both clinical and phantom) submitted for accreditation. The medical physicist should assist the facility in assessing the condition of the scanner as well as optimizing the clinical protocols.This lecture will provide a brief overview of the application steps, and some of the most common problems encountered during clinical portion of the accreditation submission.Learning Objectives:1. Understand the basics of the ACR MR Accreditation process.2. Understand the relationship of the medical physicist in this process as it relates to clinical protocols.3. Understand some of the most common pitfalls and misconceptions in the accreditation process.
TU‐A‐BRC‐01: Monte Carlo Treatment Planning: Implementation of Clinical Systems
Authors: Popple R , Cygler J 
Published: April 2010

Monte Carlo (MC) based treatment planning systems are already commercially available for both photon and electron beams and more users are implementing them in a clinical setting. Therefore it is important that strategies and paradigms for clinical commissioning and implementation of such systems be formulated and discussed. The purpose of commissioning tests for MC based treatment planning systems is not only to evaluate the accuracy of the system, but also to define the optimum calculation parameters, such as number of histories, calculation voxel size, etc., which will be applied in clinical use of the system. This in turn requires that medical physicists responsible for clinical implementation of such systems are well educated in principles of Monte Carlo algorithms.We provide a brief review of AAPM Task Group Report No. 105 (Med. Phys. 34 (2007) 4818–4853), a document which outlines the important aspects of a MC‐based dose calculation algorithm, from the basic aspects of the use of the MC method for radiation transport to the application of this approach in routine clinical photon and electron beam treatment planning. We also describe possible clinical implementation issues, including dose‐to‐medium vs. dose‐to‐water differences and give comparison of computation times for typical patient anatomies and calculation parameters.Learning Objectives:1. To provide an educational review of the physics of the MC method.2. To discuss the factors associated with MC dose calculation within the patient‐specific geometry, such as statistical uncertainties, approximations of the underlying physics model, CT‐number to material density assignments, and reporting of dose‐to‐medium versus dose‐to‐water.3. To briefly review the vendor transport codes currently used for clinical treatment planning.4. To discuss the issues associated with experimental verification of MC algorithms.5. To briefly review the potential clinical implications of MC calculated dose distributions.6. To provide example timing comparisons of the major vendor MC codes in the clinical setting.
TU‐A‐210A‐01: Quality Assurance for Digital Radiography
Authors: Willis C 
Published: April 2010

Diagnostic medical physicists have traditionally played a key role in the radiology department's Quality Assurance (QA) program. Procedures for QA of digital radiography (DR) systems are less well‐established than those designed for conventional screen‐film radiography. Some methods that were appropriate for conventional systems do not yield accurate results for digital systems. Methods that rely on images on film cannot be performed in a facility devoid of chemical processing. Methods that do not consider effects of all stages of the digital imaging chain from acquisition to display are likely to provide erroneous results. Digital systems often do not provide data in a convenient form for assessing performance. Nevertheless, medical physicists are responsible for designing and directing efforts to assure the safety and efficacy of DR.Development of standards for performance verification of digital radiographic systems has been outpaced by commercialization of the technology. Practitioners, operators, vendors, and medical physicists are uncertain as to how to configure, calibrate, and verify systems for the best diagnostic quality images at the lowest practical radiation exposure to the patient. Several manufacturers have fielded commercial systems for performance verification, but long term data indicating trends and action limits is rare. Sources of definitive information on practical clinical methods are also scarce in the scientific literature. This has led to the current situation where clinical imaging operations are routinely conducted using systems that are not optimized.The good news is that methods in common practice for conventional radiography can be applied with modification to digital radiography. Some of these methods are described in recent literature. The AAPM has recognized the dilemma and has initiated an effort to provide practical guidance to clinical physicists, i.e. Task Group 150.This lecture will discuss some components of a QA program for DR, including adaptation of conventional QA processes. The lecture will discuss methods of evaluating system performance and provide examples of potential interferences. The lecture will review commercial devices for performance evaluation and their limitations. Finally, some ongoing standardization efforts will be described.Learning Objectives:1. Review components of a QA program and show how they apply to DR.2. Understand how some conventional tests should be modified for a digital radiographic system integrated into an electronic image management system.3. Identify key references and standards that can be useful in QA of DR.
TU‐B‐BRC‐01: Promise and Challenges of PET for Target Definition and Treatment Response Evaluation
Authors: Jeraj R , Kirov AS 
Published: April 2010

Positron Emission Tomography (PET) images show physiological and biological information through the in vivo distribution of radioactive, positron‐emitting agents. PET imaging shows focal and distributed regions of cancer and its metastases. Initial PET uses in oncology include diagnosis and staging, which are important for determining treatment decisions. Current PET uses now include target definition for radiation planning followed by PET‐based assessment of treatment. Hybrid PET‐CT devices are becoming attractive radiation treatment simulators.PET imaging has coarse spatial resolution compared to CT and MR. PET's clinical use is valued because of its great sensitivity for cancer detection. While F‐18‐labled Fluoro‐deoxyglucose (FDG) remains the most promising agent for tumor diagnosis and staging, other, biologically more specific agents (e.g., FMISO, CuATSM for hypoxia imaging or FLT for cell proliferation imaging) might be more appropriate for target definition and treatment assessment.Although PET brings to radiation therapy of cancer the critical advantage of defining the tumor based on its molecular properties, delineating the gross tumor volume (GTV) with PET is problematic due to the uncertainties in the biological and physiological processes governing the tracer uptake and due to physical limitations for the accuracy of PET images. The main PET image degrading factors, including limited resolution, photon scatter and attenuation will be described and some of the current correction strategies will be introduced. A brief summary of the PET image segmentation methods will be presented.This course reviews PET‐CT hybrid scanning devices, uses of FDG and non‐FDG PET for oncology imaging, and quantitative aspects for PET‐based radiation target definition and treatment assessment. Example images demonstrate the potential contributions and limitations of FDG and non‐FDG PET oncology imaging. This review course is intended for both imaging and radiation oncology physicists.Learning Objectives1. Understand the principle and the current physical limitations of PET2. Become familiar with the types of PET‐based tumor segmentation methods3. Discuss quantitative aspects of PET imaging for treatment assessment
TU‐C‐304A‐05: Dose Reductions of Bismuth Shields in Diagnostic Radiology: Measurements and Monte Carlo Simulations
Authors: Kim S , Yoshizumi T , Frush D , Anderson‐Evans C , Toncheva G 
Published: April 2010

Purpose: To assess the dosimetric characteristics of bismuth breast shields for a CT beam with ion chamber measurements and Monte Carlo simulations. Method and Materials: Primary attenuation and backscatter effects of both adult and pediatric bismuth superficial organ (e.g. breast) shields were measured with a 0.18‐cc ion chamber and a rectangular slab phantom made of a tissue equivalent material. Simulated CT beams (120 kVp with 100∼400 mAs) were used to irradiate the ion chamber with and without bismuth shields. Both 2‐ply (pediatric) and 4‐ply (adult) bismuth shields (F&L Medical Products, Vandergrift, PA) were placed at the front of the chamber for primary attenuation measurements and at the back of the chamber to measure backscatter radiation. Radiation doses were measured free‐in‐air and in the tissue‐equivalent slabs. Monte Carlo simulations for the same measurement settings were performed by using EGSnrc/BEAMnrc code. Results: Mean radiation dose reduction from primary attenuation was about 23% (2‐ply) and 40% (4‐ply) for the free‐in‐air and tissue slab measurements. The radiation dose increase from backscatter was around 2% for both the 2‐ply and 4‐ply shields. The Monte Carlo simulations produced the dose reduction from primary attenuation was about 20% (2‐ply) and 38% (4‐ply), and the dose increase from backscatter was around 6% for both shields.Conclusion: Primary attenuation is the dominant factor that induces radiation dose changes in bismuth shields in CT examinations. The dose contribution from backscattered radiation in bismuth shields is very small.
TU‐E‐303A‐01: Contrasted‐Enhanced Breast Tomosynthesis
Authors: Maidment ADA 
Published: April 2010

Digital breast tomosynthesis (DBT) is on the verge of routine clinical use in the United States; every major mammography manufacturer has a prototype under development, numerous clinical trials are in progress and one manufacturer is selling systems in Europe. DBT has been shown to have clear value in increasing the conspicuity of lesions by removing overlaying structures present in mammograms.Regardless of the advances, DBT is currently limited to the depiction of tumor morphology. We have recently installed a Hologic Dimensions DBT prototype that has been modified to allow contrast‐enhanced (CE) imaging. Both dual‐energy and temporal CE‐DBT are under investigation. In previous work, we have shown that CE‐DBT can provide results concordant with dynamic contrast‐enhanced MR in a group of 17 women with known or suspected breast cancer. Our work continues with technique optimization, reconstruction algorithm development, motion correction, and scatter and other signal dependent corrections. With appropriate corrections, CE‐DBT can accurate quantify contrast agent uptake.CE‐DBT has potential benefit in a number of roles, as illustrated by breast MR. These roles include screening high‐risk populations, staging cancer patients through identification of multifocal, multicentric and contralateral cancer, and assessment of tumor response to neoadjuvant chemotherapy. Research is also ongoing in the field of targeted radiographic imaging agents for breast cancer.Learning Objectives:1. Review the state‐of‐the‐art in DBT system design2. Describe adaptations necessary to perform quantitative CE‐DBT3. Exemplify the clinical applications of CE‐DBTResearch support for this project has been provide in part by XCounter AB, General Electric Health Care, and Hologic Corp, in addition to the Komen for the Cure Foundation, the Department of Defense and the Radiological Society of North America.
TU‐E‐303A‐03: Breast CT as a Platform for Image Guided Therapies of Breast Cancer
Authors: Boone JM , Prionas N , Burkett G , Packard N , Yang K 
Published: April 2010

Dedicated breast computed tomography (CT) systems were designed and fabricated in our laboratory using off‐the‐shelf components (x‐ray system, detector, and bearing) integrated into a custom designed system. For imaging, a 360 degree acquisition using cone beam geometry is used to acquire 500 projection images which are reconstructed to produce a high resolution ∼512 × 512 × 512 CT volume data set. In addition to the diagnostic imaging capabilities of the bCT scanner, the system appears to be an excellent platform for image guidance of interventional procedures such as robotic biopsy, radiofrequency ablation, and cryoablation. In addition to percutaneous procedures, the bCT system may also be an excellent platform for rotational beam radiation therapy. Computer simulations and physical phantom‐based experiments were used to define the dose distributions possible using the bCT system for radiation therapy. A number of beam energies from 120 kVp to 480 kVp were simulated. Initial results suggest that in addition to homogeneous dose distributions for treating the whole breast, that focused therapeutic approaches using collimators may be possible. The pendent position of the breast with the women prone is also thought to be a more reproducible approach to fractionated radiotherapy of the breast.Educational goals are to inform the attendee of the possible benefits of breast cancer therapies delivered from a breast CT platformResearch support for this project has been provide in part by Varian Medical Systems, Fuji Medical Systems, and Hologic Corporation, in addition to the NIH
TU‐E‐213A‐01: Quality Assurance for the Leksell Gamma Knife Perfexion™
Authors: Petti P 
Published: April 2010

The Leksell Gamma Knife_ Perfexion_ is the latest gamma stereotactic radiosurgery (GSR) unit manufactured by Elekta (Elekta Instrument, AB, Sweden). Introduced in 2006, it is substantially different in design and operation from previous Gamma Knife (GK) models. The major differences are in the collimation system, the configuration of the radioactive 60Co sources, and in the patient positioning system. The Perfexion_ has one fixed tungsten collimator containing 576 different collimating channels, whereas older GK models have one primary collimator, located inside the unit, and 4 interchangeable secondary collimators that are mounted manually. In the Perfexion_, 192 60Co sources are situated on 8 moveable sectors (24 sources per sector), that slide over the collimator placing the sources over the planned collimating channels to deliver the desired radiation shot size. In older GK models, by contrast, 201 60Co sources are fixed in space and arranged in a pseudo‐hemispherical configuration. Finally, for the Perfexion™ the treatment table, which moves with sub‐millimeter accuracy in three orthogonal directions, is the patient positioning system. For older model GK units, patient positioning is accomplished by attaching the Leksell stereotactic frame to the secondary collimator via specialized hardware called trunnions or via the automatic‐patient‐positioner (APS).The specific goals of quality assurance (QA) for gamma stereotactic radiosurgery include determining the dose rate for the largest available collimator, measuring the relative output factors and beam profiles for each collimator size and comparing the results to those used in or calculated by the treatment‐planning program, and verifying that the radiation focal point coincides with the center of the patient positioning system. Although these QA tasks for GSR units have remained essentially unchanged over the years, new tools and protocols designed for linear accelerator QA have become available that can be applied to QA for GSR devices. With this in mind, a new AAPM Task Group (TG‐178) has recently been formed and charged with updating QA procedures for older GSR devices that have static sources, creating new QA protocols for GSR devices that are characterized by moving sources, and suggesting a protocol for ionization chamber calibration specific to GSR devices.This lecture will describe the operation of the Leksell Gamma Knife_ Perfexion_ and the unique features of QA for GSR units, with emphasis on the Perfexion_. Some of the questions faced by TG‐178 will be discussed, old QA procedures will be reviewed and possible new QA tests will be suggested.Learning Objectives:1. Review QA requirements for GSR units2. Understand the design differences between older GK models and the Perfexion_ and the implications of these differences on routine QA3. Become familiar with tools provided by the manufacturer to facilitate GK QA4. Understand the difficulties associated with dosimetric calibration of GSR units5. Review the use of radiochromic film for GK QA