bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐FF‐T‐431: Time Delay Study of a CT Simulator in Respiratory Gated CT Scanning
Authors: Guan H 
Published: July 2006

Purpose: To evaluate the time delay in respiratory gated CT scanning and its effect to motion synchronized radiotherapy.Materials and Methods: In this study, we presented a technique to measure the time delay of AcQSim CT simulator (Philips Medical Systems) using Varian's Real‐Time Positioning Management (RPM) system (Varian Medical Systems). A respiratory gating platform (REF 91150, Standard Imaging, Inc.) was first set at the position of amplitude maximum (Phase 0). Then a ball of 1.3 cm diameter was put on the platform and set at the CT laser. A single axial‐scan was acquired across the center of the ball without motion. Then the motion was turned on and single axial‐scans gated at different phases were acquired with a very narrow gating window. The time between the phase giving a good estimate of the ball and Phase 0 is the overall delay time. The delays were also verified using metal balls of 1.5 mm diameter initially set at the amplitude minimum (Phase 180).Results: We found that for AcQSim CT, the overall delay for a single axial‐scan (with 1s‐scan time) is 1.75s. For multiple axial‐scans, the overall delay is 1.75s for the first scan and 0.75s for the subsequent ones. This demonstrated that the CT mechanical startup delay is 1s. After the first axial‐scan, the overall delay per scan is less because CT gantry continuously spins and no mechanical delay exists. We call the overall delay without the mechanical part the scanning delay, which basically equals to half the scan time (0.5s for 1s‐scan time) plus the gating pulse triggering delay (250 ms). Conclusion: It is the scanning delay rather than the triggering delay that should be compensated when doing motion synchronized radiotherapy. The current interface between the RPM system and the AcQSim CT does not compensate for this delay.
SU‐FF‐T‐435: Tongue and Groove Effect in Direct Aperture Optimization IMRT Plans
Authors: Earl M , Cao D , Shepard D 
Published: July 2006

Purpose: Direct Aperture Optimization (DAO) is a promising new IMRT technique whereby the MLC leaves and relative weights of the apertures are simultaneously optimized. Due to the stochastic nature of the simulated annealing optimization algorithm, MLC leaves can have positions that are significantly different from their neighboring leaves. Opposed adjacent leaves with these positions can lead to a “ripple” in the dose distribution due to tongue‐and‐groove effect (TGE). In this work, we attempt to quantify the magnitude of the effect and commission the Pinnacle planning system to account for it. Method and Materials: To quantify TGE, we generated a two‐segment beam: one segment with every other leaf on one side extending well past the central axis and the other with every other opposed adjacent leaf extending well past the central axis. Jaws set to 20×20 bound both segments and both had equal monitor units. This beam was delivered to a flat phantom with a film placed at 10cm depth.Newer versions of Pinnacle (7.4 or greater) take into account TGE. This is modeled in the physics tool with a tongue‐and‐groove step parameter. We systematically changed this parameter and compared the resulting dose distributions to the film measurement.We imported DAO IMRT plans into the Pinnacle planning system and compared the dose distributions with and without TGE. These were also compared with verification measurements. Results: The film displayed a 23% variation from minimum to maximum dose. The Pinnacle step parameter of 0.3cm reproduced the variation. If TGE is not accounted for in the planning, an underestimation of the absolute dose is observed for DAO IMRT plans. The magnitude of the underestimation is dependent upon the aperture shapes. Conclusions: TGE affects the dose distribution for DAO plans. Limiting the distance adjacent leaves may travel can reduce the effect of TGE.
SU‐FF‐T‐447: Utility of Film Dosimetry for Assessing TomoTherapy Treatments of Superficial PTVs
Authors: Cheek D , Hogstrom K , Gibbons J , Rosen I 
Published: July 2006

Purpose: To assess the utility of film dosimetry in a cylindrical polystyrene phantom for evaluating the accuracy of dose calculated by the TomoTherapy HI⋅ART treatment planning system for superficial planning target volumes (PTVs). Method and Materials: A TomoTherapy treatment plan was developed for a superficial PTV (1‐cm deep radially by 90° azimuthally by 4.2‐cm longitudinally) contoured on a 27‐cm diameter by 37.4‐cm long cylindrical white opaque polystyrene phantom. The phantom included two removable planar film cassettes, one perpendicular to and one including the cylinder's axis. Kodak EDR2 film was cut using templates, resulting in film edges coinciding with the phantom surface (±0.25‐mm). The axial film was irradiated according to the TomoTherapy plan then the phantom was translated longitudinally and the sagittal film irradiated. The films were scanned with a Vidar film digitizer, converted to dose, and the common depth‐dose curves compared. Measured axial and sagittal dose distributions were compared with those calculated. Results: The common depth‐dose of the axial and sagittal films agreed well, although the axial film had a lower relative dose by 2.5%. Comparisons of measured and calculated dose on the axial film showed agreements to within 5% at depths greater than 3‐mm. At shallower depths, doses showed larger differences but distance‐to‐agreement values were small (<2mm). These differences could be due to planned to delivered dose alignment techniques and/or the film cutting process, which is under investigation. Conclusion: Orthogonal films irradiated in a cylindrical polystyrene phantom produced common depth‐dose curves that agreed well. Future comparisons with thermoluminescent dosimetry should confirm the utility of EDR2 film for a comprehensive study of the accuracy of the TomoTherapy treatment planning system for planning treatments of superficial PTVs normally treated with electrons.Supported in part by a research agreement with TomoTherapy, Inc.
SU‐FF‐T‐459: An Implantable Dosimeter Study of Patients with Prostate Cancer
Authors: Beyer G , Scarantino C , Mann G , Carrea T , Anscher M , Prestidge B , Black R 
Published: July 2006

Purpose: A study of 30 prostate cancer patients who received implanted radiation dosimeters in conjunction with external beam radiation therapy has been completed. The purpose of the study was to compare daily measured dose to the value predicted by the treatment planning system. Method and Materials: In most patients two dosimeters were placed adjacent to the capsule of the prostate. The devices were introduced perineally using a trocar/cannula system. Polyester mesh was placed behind the sensors after insertion to prevent them from moving back down the insertion track before healing occurred. Serial CT scans were taken to gauge any migration of the devices away from the point of surgical placement. Some patients were localized on a daily basis using a kilovoltage x‐ray positioning system. The clinical protocol did not permit alteration of the therapy parameters based on sensor readings. Results: An evaluation of the dose discrepancy between measured and planned values was completed for each sensor. Additionally, the relative standard deviation of each sensor's readings was calculated (as a measure of randomness of the readings). In many patients, the relative standard deviation value exceeded 3%, which is beyond the nominal value for the sensor itself when tested in a phantom. In some patients the cumulative dose for a given treatment period disagreed with the planned dose by 5% or more. The discrepancy tended to be more pronounced for boost phases when the isodose contours were reduced in volume. Conclusions: This initial data suggests that implanted dosimeters may play a useful role in tracking dose discrepancies, both systematic and random, in patients being treated with external beam therapy for prostate cancer. Future studies will focus on the effects of daily kilovoltage x‐ray localization, using the dosimeters as fiducial markers, on the magnitude and randomness of dose discrepancies.Supported by Sicel Technologies.
SU‐FF‐T‐466: A Single Dose Calibration Method for IMRT QA Film Dosimetry Using Gafchromic® EBT Film
Authors: Baker J , Telivala T , Reinstein L 
Published: July 2006

Purpose: In order to decrease the workload for IMRT QA film dosimetry we propose a simple method for Gafchromic® EBT film calibration using a pre‐measured batch calibration curve (BCC) which is mathematically scaled with a single dose exposure (SDE) for each subsequent IMRT QA session. We evaluate how the SDE method corrects for post exposure density growth and temperature dependence in addition to inter film response homogeneity. Method and Materials:Each of five EBT films, from a single production lot, were exposed to doses of 22.5, 43.1, 84.4, 147.4, 209.1, and 291.2 cGy. Measurement of the resulting response curves were performed at times ranging from 0.7 to 52 hours post exposure on a Macbeth TD932 point densitometer customized with a 636nm band pass filter and 16 bit digitizer for increased sensitivity, yielding 35 curves in all. The BCC was generated from a film measured at 0.7 hours and fit to the equation . To test the method, net optical density (NOD) data for the remaining 34 curves was scaled to fit the BCC using 209.1 cGy as the SDE. The scaling factor is the ratio of the actual measured NOD of the SDE, and the NOD predicted by the BCC for this dose. The new scaled calibration is used to predict all 204 test doses, which were then compared to the actual delivered doses. Results: Using the single uncorrected BCC resulted in an average error for the 204 dose points of 11.9 cGy. However, scaling according the method described reduced the average measured dose error to 1.1 cGy. Conclusion: The single dose exposure method described here is an accurate and time efficient calibration procedure for IMRT QA film dosimetry. Conflict of Interest: Partially supported by International Specialty Products.
SU‐FF‐P‐05: Medical Physics Situation in Colombia
Authors: Machado N , Plazas M 
Published: July 2006

Purpose: To describe the current situation of the Medical Physics field in Colombia concerning to human resources, physics infrastructure (radiation oncology centers, radiation machines, treatment planning systems, dosimetry systems, nuclear medicine and diagnostic facilities, imaging devices and radiation protection systems), academic programs, medical physics societies and regulatory institutions. Method and Materials: For this presentation we have taken as reference some studies carried out in Colombia during the last few years as follows:• Evaluation of radiation oncology facilities in Colombia, an audit study conducted to evaluate the radiotherapy centers and the quality of assistance for cancer patients.Comparison among Medical Physics academic programs offered in the world, specially those carried out in the Latino‐American region. Results: Up to the date the mentioned study was conducted, there was 46 radiation therapy centers in Colombia and only 14 had medical physicists.The number of nuclear medicine centers existing in Colombia was approximately 47, mainly concentrated in Bogotá, where 22 of them are located. Currently the number of medical physicists working in the nuclear medicine facilities in Colombia is really scarce.Worldwide it can be seen that North America is the region with the greatest number of universities offering Medical Physics Master programs. In the Latin American context, Mexico had the greatest number.The statistical distribution of diagnostic x ray machines was about 53000 in Latin‐American countries and the number of medical physicist working to these centers is very low. There is human resources shortage, especially for Medical Physicists in the radiation oncology, nuclear medicine and diagnostic facilities. There are some academic programs in Medical Physics. Currently there is a increasing interest from universities in Colombia to create medical physics under and postgraduate programs.
MO‐A‐330A‐01: Recent Advances in Digital Mammography
Authors: Yaffe M 
Published: July 2006

Digital mammography was developed to address several technical limitations of screen film mammography with the goal of improving the accuracy of detecting breast cancer. The recent publication of the results of the ACRIN DMIST study has demonstrated such an improvement in a subset of women, notably, younger women and those with dense breasts. Nevertheless, the study also indicated that a significant fraction of cancers were not detected by either film or digital mammography. This is likely due to a number of reasons including the biology of the cancers, inadequate conspicuity of the lesions and variability of the skills of the radiologists. While it probably is not possible to detect all these cancers with mammography there are promising new techniques that can be developed on the platform of digital mammography to improve detection. One of these is computer‐aided detection, the use of computer artificial intelligence algorithms to identify patterns in the digital images that are suspicious for the presence of cancer. These provide some of the advantages of double reading of the mammograms (interpretation by two different radiologists), a process known to improve the sensitivity of cancer detection. Another new technique is contrast‐enhanced digital mammography (CEDM), which images leakage of an iodine contrast agent from microscopic vessels formed in the vicinity of a growing tumour. By imaging this tumour angiogenesis, cancers that are invisible on mammography might be seen. In addition, better information about the extent of the disease will be helpful in planning therapy. In mammography all of the anatomy in the 3‐dimensional breast is superimposed in two dimensions to form the image. Tomosynthesis and breast CT provide three‐dimensional images to separate the structures within the breast, possibly allowing tumors to be seen more easily and eliminating the overlap of structures from different parts of the breast that can falsely resemble a cancer. Telemammography can help improve the accessibility of high quality mammography in sparsely‐populated communities. In this presentation, the current status and the potential of these exciting new techniques will be considered.Disclosure:Martin Yaffe's laboratory carries out research on topics related to digital mammography in collaboration with GE Healthcare. Martin Yaffe is a member of the Scientific Advisory Board of XCounter.Educational Objectives:1. Become familiar with current challenges in breast cancer imaging.2. Learn about new techniques that are available or under development to address these challenges.
MO‐A‐330D‐01: Advances in PET Technology ‐ New Crystals and Detector Designs
Authors: Fahey F 
Published: July 2006

Over the past ten years, the use of clinical PET, particularly in the field of oncology, has increased dramatically. More recently, the introduction of hybrid PET/CT scanners has led to an enhanced ability to provide anatomical correlation to the functional findings on the PET scan. And lastly, the growing field of molecular imaging has led to the development of a variety of dedicated PET systems for small animal imaging. In the clinical arena, the goal is to develop scanners with higher sensitivity and count rate capability to be able to acquire whole body scans more efficiently. Efficiency is essential with respect to small animal imaging as well, but it must be accomplished with very high spatial resolution. This presentation will review the basics of PET imaging with a look towards the advances being made to address the needs of these two very different imaging tasks. The use of 2D versus 3D will be discussed as well as the effect using different crystal materials. Other advances being actively pursued such as the use of time‐of‐flight PET will also be discussed.Educational Objectives:After attending this presentation, the attendee will be able to list 2 advantages and 2 disadvantages of 3D PET compared to 2D PET for clinical, whole body imaging, name 3 different materials used in state‐of‐the‐art PET scanners and list 2 advantages of each, and discuss two potential advantages for time‐of‐flight PET.
MO‐A‐ValB‐01: Tradeoffs in Image Quality and Radiation Dose for CT
Authors: McNitt‐Gray M 
Published: July 2006

In CT scanning, image quality has many components and is influenced by many technical parameters. While image quality has always been a concern for the physics community, clinically acceptable image quality has become even more of an issue as strategies to reduce radiation dose — to all patients, but especially to pediatric patients— has become a focus in many radiology practices.The purpose of this presentation will be to first describe several of the components of CT image quality — noise, slice thickness (Z‐axis resolution), low contrast resolution and high contrast resolution— as well as radiation dose and to describe how each of these may be affected by technical parameter selection. This presentation will pay particular attention to the tradeoffs that exist between different aspects of image quality, especially when the reduction of radiation dose is one of the objectives.The presentation will then explore several mechanisms that can be used to reduce radiation dose in CT exams and the implications for the diagnostic image quality of the exam. Specifically, the implications of varying the tube current*time product (mAs), pitch or tablespeed (or for axial imaging, the table increment), slice thickness, beam energy (kVp), patient (or phantom) size and dose reduction options (such as tube current modulation) will be described for both radiation dose and diagnostic image quality. Finally, this presentation will emphasize that the tradeoffs between radiation dose and image quality are clinical‐task dependent; that is, the goals of the clinically indicated exam dictate what aspect of image quality may be emphasized for that exam (low contrast resolution or high contrast spatial resolution, etc.) and this will have implications for the amount of radiation dose reduction that is acceptable. This will be illustrated with examples from selected diagnostic imaging exams.Educational Objectives:1. Understand key components of image quality in CT scanning as well as reinforce CT radiation dose concepts.2. Understand the impact that technical parameter selection has on the various aspects of image quality and radiation dose.3. Examine the tradeoffs between various aspects of image quality and radiation dose.4. Examine the impact of these tradeoffs on a few clinical imaging protocols and illustrate the task‐dependence of image quality requirements.
MO‐A‐224C‐01: Daily Localization I: KV/CBCT
Authors: Yin F , Yoo S , Wang Z , Godfrey D , Wu Q 
Published: July 2006

Daily target localization is a critical step to secure accurate delivery for 3‐D conformal radiation therapy and intensity‐modulated radiation therapy. One emerging technology using in‐room kilovoltage (kV) imaging has shown to be very promising for targeting treatment volumes. The major advantages of using kV imaging are 1) its comparable contrast between soft tissue and bone structure to that in simulation images, 2) real‐time high resolution fluoroscopic imaging, 3) lower radiation dose to patient compared to conventional MV imaging, and 4) availability of reconstructing tomographic images (for example, cone‐beam CT) using 2‐ D kV projection images. At present, different types of in‐room kV imaging systems are being developed for different applications such as in‐room CT on rail, ceiling‐mounted dual‐source/detector configuration, and gantrymounted single source/detector system. In terms of clinical applications, some generate 2‐D radiographic images for target verification based on bony marks or implanted surrogator while others generate 3‐D tomographic images for target verification based on both soft tissues and bony structures. Some could be used for viewing organ motion to verify applied margin while others could be used for monitoring target motion to verify dynamic delivering or gated treatment. Issues related to the risk and benefit between imaging information and radiation dose using 2‐D or 3‐D imaging, the geometric accuracy of imaging systems, trade‐off between treatment accuracy vs. time required to carry on imaging and manipulation process, early image‐guided protocols for basic clinical applications, etc. will be discussed. Some new developments related to effective and efficient use of in‐room kV and MV imaging, tomographic image reconstruction using limited number and angle projections have shown very promising for future clinical applications.This lecture will describe the commercially avaialbe kV imaging systems, as we as their applicable clinical protocols, acceptance testing and commissioning processes, basic QA requirements, system limitations, and potential future developments.Educational Objectives:1. Understand the latest commercial available technologies for in‐room kV and CBCT systems.2. Understand the basic functionalities of in‐room kV imaging system.3. Understand the basic imaging applications.4. Understand the basic system limitations and QA.
MO‐B‐330D‐01: Design and Performance Characteristics of Computed Radiographic Acquisition Technologies
Authors: Schaetzing R 
Published: July 2006

Digital Radiography (DR) using Storage Phosphors, also known as Computed Radiography (or CR), has been commercially available for a quarter of a century. Each new generation of scanners and screens has brought improvements in image quality, throughput, physical size and cost. With these improvements has come a high level of clinical acceptance, with a corresponding displacement of screen/film systems as the standard for projection radiography acquisition.Scanner improvements include better, more reliable light sources, more efficient light collection systems, higher quality photodetectors, and better electronics. The latest CR scanner advances have done away with traditional flying‐spot (point‐at‐a‐time) scanning in favor of line‐at‐a‐time scanning, bringing significant throughput, image quality, and size advantages. At the same time, advances in the design and manufacture of powder‐based, particle‐in‐a‐binder CR screens, or image plates, have enabled improved inherent signal and noise properties (x‐ray absorption, Modulation Transfer Function, Noise Power Spectra, Detective Quantum Efficiency, etc.), and a better matching of screen absorption and emission spectra to the scanner characteristics. Screens with transparent substrates have produced improved image quality due to the ability to extract latent image signal from both sides of the screen. The latest storage‐phosphor screen materials can be grown in needle form, similar to the scintillators used in indirect flat‐panel detectors, resulting in dramatically improved image sharpness and higher x‐ray absorption due to the absence of binding material.This presentation will review the form, function and performance of CR systems, with an eye towards more recent developments. The current state of the art in CR will be placed into the larger context of newer DR acquisition systems (e.g., active‐matrix flat panels), looking at the advantages and disadvantages of each. Advances made in CR technologies in recent years portend continued expansion of CR‐based medical imaging.Educational Objectives:1. Describe the form and function of today's computed radiography (CR) systems.2. Identify the main factors that influence the image quality of CR systems.3. Compare modern CR systems to other acquisition technologies.4. Describe the latest and future developments in CR.Conflict of Interest StatementThe author is employed by Agfa Corporation.