bluuebunny/crossref_metadata_2025 huggingface dataset:
MO‐D‐224A‐07: A New Software Tool for Quantitative Verification of IMRT Fluence Maps
Authors: Gong Jason , Burmeister Jay
Published: July 2006

Purpose: To provide a mechanism for quantitative verification of each bixel in an IMRT fluence map within minutes. Method and Materials: A software tool called Super‐IMPOSE (Intensity Map Pre‐treatment OverSight & Evaluation) was developed to quantitatively verify fluence maps using an Electronic Portal Imager (EPI). This software imports EPI‐measured fluence maps along with TPS‐calculated maps and compares them by bixel. We developed a convolution algorithm to correct the raw fluence map for the effects of scatter within the imager, along with an edge detection and registration algorithm. Deviations between the predicted and measured bixel values are displayed as a matrix of percentage deviations, with maximum, mean, and standard deviation values calculated for each row, each column, and the entire map. Clinical applicability was investigated using IMRT plans delivered using a Varian accelerator with aS500 EPI. A set of 16 fluence maps from 6 different patients was selected, spanning a wide range of size and complexity, and employing both 0.5cm and 1cm bixel sizes. Results: The mean and standard deviation values for the bixel intensity differences were 1.9% and 1.4% for the 1cm bixel maps, and 3.2% and 1.8% for 0.5cm bixel maps. These differences are relatively small compared to the bixel intensity step size of 10%, making it relatively easy to assure that the correct intensity level was delivered to a bixel. Gross errors, such as an incorrect DMLC file or jaw setting, are easily detected by visual inspection or the resulting large mean and standard deviation values. Conclusion: This software tool facilitates accurate and expeditious IMRT delivery QA, allowing verification of all maps in a matter of minutes. The development of a more accurate convolution kernel will allow further reduction in comparison uncertainties. Clinical use will allow the establishment of a numerical threshold for a map to “pass” verification.
MO‐D‐224A‐08: Automated Patient‐Specific IMRT Quality Assurance Using Exit Detector Data
Authors: Seibert R , Ramsey C
Published: July 2006

Purpose: To develop tools for automatically evaluating IMRT treatments during delivery using exit detector data on a helical tomotherapy system. Methods and Materials: Treatment delivery sinograms and exit detector data were obtained following 6 treatment delivery sequences. The delivery sequences included 1.) No known error and nothing in the path of the beam, 2.) No known error with the couch in the path of the beam, 3.) No known error with an anthropomorphic pelvis phantom in the path of the beam, 4.) 1% error with nothing in the path of the beam, 5.) 1% error with the couch in the path of the beam, and 6.) 1% error with an anthropomorphic pelvis phantom in the path of the beam. A modeling technique was developed that could learn the attenuation relationships involved with the compressed data, thus distinguishing MLC errors from patient attenuation. A principal component modeling algorithm was developed for this purpose, employing the Hotellling's T2 statistic and the Q statistic. To develop the principle component model, the sinogram data were standardized, subtracted from one another and projected onto the model. A prospective analysis was also performed using the MLC delivery sequence to produce an expected detector signal with and without errors. Results: The Q‐statistic proved to be most useful for identifying errors in MLC openings, but correctly identified outliers and their contributing channel only when the model was trained with dissimilar (error‐less and error containing) data sets. The T‐statistic accounted for different attenuations present. Conclusions: Overall, the algorithms for analyzing compressed and uncompressed data proved to be useful in identifying errors as small as 1% in the MLC sequence.
MO‐D‐230C‐01: Evaluation of Medical Displays
Authors: Samei E
Published: July 2006

Participants:

J Charette, Barcoview, LLC;

E Samei, Duke University;

N Hashimoto, Eizo Nanao;

K Compton, National Display Systems;

A Abileah, Planar Systems;

D Sorensen, Richardson Electronics / Image Systems;

C Lipfert, Scanditronix Wellhofer GmbH;

M Hasegawa, Totoku;

H Roehrig, University of Arizona

Electronic display is a key component of modern medicine, providing soft‐copy viewing of medical images. Being the last component of the image chain, display quality can have a notable impact on overall accuracy and efficiency of the diagnostic process. Thus, it is necessary to ensure that the physical performance of a medical display is adequate for its intended use. Led by a task group initiative by the American Association of Physicists in Medicine (AAPM TG18), new guidelines have recently been published defining objective and standardized assessment procedures and criteria for acceptance testing and quality control of medical display devices (Samei et al, Med Phys 32:1205–25, 2005). The guidelines include detailed visual and quantitative methods and specific acceptance criteria for basic display characteristics including luminance, luminance spatial and angular response, resolution, noise, veiling glare, reflection, color uniformity, geometrical distortions, and display artifacts. The TG18 guidelines are also being gradually reflected in a number of other national and international directives including those by the IEC and the ACR. The goal of this demonstration workshop is multi‐fold: 1) to present a tutorial on the TG18 guidelines and its adaptations, 2) to discuss its implementation by specific vendors, 3) to offer an opportunity for hands‐on exposure to the practical aspects of display performance evaluation, 4) to provide an opportunity to informally interact with experts and ask questions, and 5) to offer a panel discussion on the issues about which there might be less consensus among experts. Representatives from the TG18 committee and from industry will be present to demonstrate and discuss display evaluation issues.

Part I

1:30–2:20 Introduction

Evaluation of Medical Displays, E Samei, Duke University

2:20–3:20 Vendor lectures

2:20–2:30 Compensation for ambient conditions, K Compton, National Display Systems

2:30–2:40 AAPM implementation using Barco software, J Charette, Barcoview, LLC

2:40–2:50 Quality Control Solutions based on AAPM TG18 from Eizo Nanao, N Hashimoto, Eizo Nanao Corp

2:50–3:00 The CFS (Calibration Feedback System) Toolkit, D Sorensen, Richardson Electronics

3:00–3:10 Totoku's Medical Display QA Solutions “i‐model”, M Hasegawa, Totoku Electric Co., Ltd.

3:10–3:20 The Priorities in the Medical Displays Parameters, A Abileah, Planar Systems
MO‐E‐330A‐01: Joint Estimation of Motion and Activity Concentration for 4D Gated PET Studies
Authors: Qiao F , Pan T , Clark J , Mawlawi O
Published: July 2006

Purpose: Gated PET acquisition has been traditionally used to address the respiratory/cardiac motion induced artifacts. However, gated PET images usually have poor image quality due to insufficient photon counts. In this regard, various efforts have been made to estimate the motion information from the gated PET images first, and then use this information to produce motion‐free, high quality images. The purpose of this study is to combine the two inter‐related tasks—motion estimation and image reconstruction, into one single process. A potential advantage of such an approach is a more accurate estimation of the motion information, as well as a better quality of the reconstructed image. Method and Materials: Motion estimation and image reconstruction are jointly performed by maximizing a modified likelihood function that incorporates motion information. A computer simulation was performed on a 2D digital phantom placed in a simulated PET scanner to test the feasibility of this approach. The digital phantom consisted of a hot sphere moving sinusoidally within a warm background. The motion of the sphere was discretized into 10 steps. This simulated a tumor in the patient body influenced by the respiratory motion during a gated data acquisition using 10 time frames. The simulated PET scanner consisted of two parallel gamma cameras each having 140 detectors, and could rotate in 280 angular steps. Projection data were modeled to follow a Poisson statistics, with 20% of random counts. Results: The jointly estimated image recovered the shape of the moving object while still preserved a good image quality. Quantification error was reduced by 21.2% when compared to the static reconstruction, and SNR was improved by 185% when compared to the gated image. Conclusion: The joint estimation approach we have proposed has a good potential in motion artifacts correction for 4D PET images.
MO‐E‐330A‐03: Automated Texture Based CT Segmentation by Gabor Filtering and Fuzzy Clustering
Authors: Kakar M , Nystrom H , Nøttrup TJ , Bruland ØS , Olsen DR
Published: July 2006

Purpose: To automate segmentation of lesion and organs at risk in lung patients by using Gabor filtering and fuzzy clustering for 4D CT image data and to check the usefulness of segmentation by using these methods. Method and Materials: Image was pre‐processed with contrast enhancement and median filtering in order to prepare it for feature extraction. By filtering the enhanced image by Gabor filtering, texture features were extracted. Three fuzzy segmentation algorithms were selected including Fuzzy C‐Means (FCM), Gustaffson Kessel and Gath Geva (GG). Optimal number of clusters is determined by using validity criterion including Partition coefficient (F), Classification entropy (H), Xie Beni index (XB) and Partition index (SC). Images were then clustered and clusters visualized by using Principle Component Analysis (PCA). Finally, Performance of the algorithms was calculated by plotting the Receiver Operating Curves (ROC). Results: It was found that different clustering algorithms are best suited for different tissue/Organ segmentations. Furthermore, ROC curves indicated that FCM segmented the left lung with a True Positive (TP) rate of 94.72%, GK segmented Lesion with a TP rate of 88% and GG segmented heart with a TP rate of 74.8%. Fuzzy clustering methods in conjunction with Gabor filters are seen to completely outperform traditional Hard clustering methods like K‐Means and KMediod. Finally, there is a marked difference seen between the fuzzy clustered regions and oncologist marked GTV. Conclusion: Texture based segmentation using Gabor filtering and fuzzy clustering perform quite well for Lesion and organs at risk segmentation, however, different fuzzy clustering methods should be combined for optimal segmentation. As Gabor filters use different frequencies and orientation for filtering, they reveal hidden structure, which may contribute to a more precise delineation of tissue/lesion structure.
MO‐E‐330A‐06: Cone Beam CT (CBCT) Image Fusion for Prostate Localization: Interobserver Variability Study Using Manual and Automatic Registration
Authors: Hammoud R , Kim J , Li S , Lord B , Patel S , Pradhan D , Movsas B
Published: July 2006

Purpose: Applying manual registration of CBCT to a reference image for prostate localization increases treatment time affecting prostate motion and patient setup. A reliable automatic registration can be more time efficient and accurate. This preliminary study demonstrates variability of manual fusion by multiple observers comparing manual to an in‐house automatic fusion. Methods and Materials: 7 patients with 7 CBCT scans each were studied by 4 observers. Off‐line manual fusion between CBCT and Simulation CT was performed using On‐Board Imaging (OBI) software by Varian version 1.2. We pre‐defined our Region of Interest (ROI) and Organ of Interest (OOI) to be the pelvic bones and the prostate respectively. Offsets were recorded in 4 degrees of freedom (3 translations and couch rotation). To increase precision, one outlier observation was excluded. Interobserver variation in manual registration was studied by determining percentage of observations that fall within 1 mm and 1 degree standard deviation (SD). Automatic registration, utilizing the uphill simplex, gradient correlation and mutual information similarity measures, was compared to the manual matched results using frequency histograms of the differences between the two methods. System robustness is checked using prostate calcifications. Results: Comparing different observers, 69% cranial‐caudal (C‐C), 83% anterior‐posterior (A‐P), 100% right‐left (R‐L), and 100% (couch rotation) of the observations fall within 1 mm,1 degree SD for ROI. 69% C‐C, 75% A‐P, 90% R‐L, and 100% couch rotation were observed for OOI. ROI/OOI automatic fusion showed 92%/85% overall agreement with manual fusion within 2 mm respectively. Conclusion: Manual registration is time consuming and demonstrates observers' variations. The automatic method localizes the prostate within 15 seconds. More observers and measurements, methods utilizing drawn contours and implanted fiducial markers, will be required for system accuracy and precision. Our automatic registration with feed back from observers' experiences would enable on‐line correction for prostate motion.
MO‐E‐330A‐07: Knowledge‐Based Auto‐Contouring in 4D Radiation Therapy
Authors: Chao M , Schreibmann E , Li T , Xing L
Published: July 2006

Purpose: In this work we develop a strategy of automatic contouring to relieve the effort of organ segmentation in 4D radiation therapy. The method adopts a novel technique of control volumes to achieve robust contour mapping among a series of 4D CT images. Methods and Materials: For a given patient, segmentation of tumor and sensitive structures was manually performed for one of the breathing phases by a physician. Along the segmented contours a number of small control volumes (∼ 1cm) were selected. To obtain contours on another CT phase we mapped the control volumes collectively to this phase using rigid transformation, which served as a good starting contour for further adjustment. The final positions of mapped control volumes were determined by minimizing the energy function consisting of two terms: intensity similarity between the mapped volumes and the original volumes in the selected phase; elastic potential energy preventing control volumes from movement. The approach was tested with the 4D CT images of 5 lung cancer patients. Results: For the patients the knowledge‐based approach of automatic contouring worked well even for CT images with significant deformations. In the lung case the contours have the average error of less than 2mm and a maximum error of 5mm for noisy anatomical structures. A significant reduction of time compared with manual contouring was achieved. Conclusions: The auto‐mapping of contours in 4D radiation therapy was implemented with control volumes. The method provides an efficient way for 4D segmentation with high accuracy.
MO‐E‐330D‐01: Overview of Recent Technology Developments in CT
Authors: Hsieh J
Published: July 2006

Cone Beam CT (CBCT) is one of the most recent technical advancements in x‐ray computed tomography. The state‐of‐the‐art 64‐slice scanners provide isotropic sub‐millimeter spatial resolution, significantly improved dose efficiency, large volumetric coverage, and markedly improved temporal resolution. These capabilities open doors to new clinical applications.

This presentation provides an overview of the recent technical advancements in CBCT. The discussion first covers technical challenges that face CBCT, such as detector complexity, electrical and mechanical design, image reconstruction algorithms, dose, and information management.

The second part discusses some of the recent developments in CBCT. These include the advanced dose‐reduction techniques, the dual‐source CT scanner, more advanced reconstruction algorithms that break the traditional noise vs. dose tradeoffs, larger volume coverage, and dual‐energy CT for material decomposition and presentation. If the past 10 years of CT development can be characterized by the “slice‐war”, new technology developments are pointing to different directions.

Learning Objective:

1. Overview of the recent technology developments in CBCT.

2. Understand major technical challenges in CBCT development.

3. Explore future directions in CBCT technology.
MO‐E‐330D‐03: Clinical Perspective; Impact of Future Technology Developments; Cardiac CT; Challenges
Authors: Vannier M
Published: July 2006

Computed tomography is not the most frequent radiologic imaging procedure, but is arguably the most important in terms of clinical impact. CT is used extensively for emergencies, cardiovascular, pulmonary, gastrointestinal, endocrine, neurological, orthopedic and other applications ‐ often as the first and only imaging procedure needed for diagnosis. The chances are very high that a patient will have a CT scan in the emergency department, as an outpatient or as an inpatient for a multitude of indications ‐ pain, trauma, suspected infection or malignancy, and frequently to clarify or resolve a question raised by another abnormal test, such as an EKG abnormality or ultrasound finding. Despite the universality of CT in hospitals and clinics as well as free‐standing imaging centers, the technology continues to evolve with greater coverage, faster acquisition and multienergy sources or detectors. The most demanding imaging applications are cardiovascular, where complex motion and small morphologic features coexist, so imaging methods that are very satisfactory elsewhere in the body may not be successful. Clinical cardiac CT consists of administering toxic materials, e.g., contrast media, while monitoring the EKG and illuminating the body with high brightness x‐rays. Larger area detectors and higher frame acquisition rates are welcome improvements, but don't solve all of the problems encountered with variability due to respiratory, random body, and cardiac motion, especially in a spectrum of patients from infant to massively obese adult sizes (< 1 kg to 250 kg or more). The challenges and pitfalls in CT will be delineated and evaluated relative to current and future technology.
MO‐E‐ValB‐01: Visualization of Anatomical Structures for Image Guided Surgery
Authors: Grimson E
Published: July 2006

Algorithmic methods from computer vision and machine learning are dramatically changing the practice of health care and the exploration of fundamental issues in neuroscience. By coupling knowledge of tissue response, atlases of normal anatomy, and statistical models of shape variation, these methods are used to build detailed, patient‐specific reconstructions of neuroanatomical structure from MRI imagery. Such structural models can be automatically augmented with information about function (using fMRI), and about connectivity (using DT‐MRI) to create detailed models of a patient's brain. These models are routinely used for surgical planning — how to reach the target tumor with minimal damage to nearby critical structures; and for surgical navigation — guiding the surgeon to the target site rapidly and safely.

By combining with statistical models of population variation, these methods can also be used to investigate basic neuroscience questions — how different are the shapes of subcortical structures between normal subjects and patients with a specific disease (such as schizophrenia or Alzheimer's); how do these shapes change with development in children, or with administration of pharmaceuticals; how do physiological properties differ between populations (such as the local structure of fiber orientation in white matter tracts). These computational methods provide a toolkit for exploring the structure and connectivity of neuroanatomical structures, in normal subjects and in diseased patients.

This lecture will review current methods for image segmentation and shape analysis.

Educational Objectives:

1. Understand algorithmic methods for image segmentation by tissue type;

2. Understand methods for analyzing shapes of anatomical structures across populations;

3. Understand the application of reconstructed anatomy for surgical guidance and navigation.
MO‐E‐ValB‐02: Hybrid Imaging for Guidance of Interventional Procedures
Authors: Fahrig R
Published: July 2006

The last decade has seen an explosion in the number of procedures carried out using minimally invasive approaches, as devices and techniques develop. The promise of these new procedures is realized only with a parallel improvement in imaging techniques. Hybrid systems that combine real‐time acquisition with cross‐sectional and/or functional data are one response to the need, and several such systems have now reached the clinic. Depending on the application, different combinations can be used to greater advantage. The interventionalist's familiarity with x‐ray fluoroscopy and the real‐time and projection capability makes it a logical first choice to marry with others such as ultrasound, CT or MR.

The combination of fluoroscopy with C‐arm CT for application to 3D vascular imaging was first implemented in the mid‐90's. New flat‐panel detector technology is now expanding the role of C‐arm CT into low‐contrast imaging applications such as detection of fresh bleeds during treatment of intracranial abnormalities and guidance of vascular and percutaneous abdominal interventions. Highest image quality depends on correction algorithms for lag, truncation, scatter etc. all of which are still under investigation. Recent investigations indicate that contrast resolution as low as 5 HU is possible under clinically realistic conditions.

The combination of fluoroscopy with MR has also been under investigation since the mid‐90's with several prototype long‐travel systems installed in research clinics. While feasibility of such systems has been shown, patient transport between imaging FOVs has been complicated and enthusiasm for the systems has been limited. New flat‐panel detectors which are immune to static magnetic fields, and new x‐ray tube designs are now under development that allow close integration of fluoroscopy and MR systems. Using a double‐donut interventional magnet and a static‐anode x‐ray tube, good image quality can be achieved from both modalities if care is taken to maintain magnetic field homogeneity, rf noise is limited, and the electron optics of the x‐ray tube are controlled. Switching between modalities can take a little as one minute.

The current status of X‐ray/MR, and of X‐ray/CT and C‐arm fluoroscopy/C‐arm CT will be discussed and described. New hardware and software for X‐ray/MR and new image correction and visualization algorithms for fluoroscopy/C‐arm CT will be described. Current challenges in the area will be outlined.

Educational Objectives:

1. Understand the options available for hybrid interventional guidance.

2. Understand the issues related to image quality in C‐arm‐based CT and XMR.

3. Understand the current challenges relating to clinical workflow, multi‐modality registration and image visualization.

Disclosure:

The work presented here has been supported by NIH R01 EB003524, P41 RR 09784, R01 EB000198, Siemens Medical Solutions, GE Medical Systems and the Lucas Foundation.
MO‐E‐ValB‐03: MRI‐Guided Focused Ultrasound
Authors: Hynynen K
Published: July 2006

Magnetic Resonance Imaging (MRI) provides such features as excellent soft tissue contrast, temperature sensitivity and ability to detect thermally coagulated tissue, that make it well suited for the guidance, control, and monitoring of thermal therapies. In this talk the current progress in MRI guided focused ultrasound thermal ablations and other non thermal interventions will be reviewed. The treatment of uterine fibroids has been approved by the FDA and is on its way to become routine. There are several other clinical trials in testing MRI guided focused ultrasound for the treatment of breast and other tumors. In addition, there is evidence that low thermal exposures controlled by MRI can be used to locally activate treatments. Finally, animal experiments show that ultrasound exposures can induce transient blood‐brain barrier disruption thus allowing targeted delivery of molecules such as chemotherapeutic agents in the brain.
MO‐E‐230A‐02: Intellectual Property ‐ Medical Physics
Authors: Hendee W
Published: July 2006

Every medically‐oriented scientific journal is confronted with a fundamental conflict. The journal exists for the purpose of disseminating information produced by authors to others who may be able to use the information to enhance their own research, education programs or clinical practices. Journals and the information they disseminate contribute in a substantial way to progress in science, education and the clinical practice of medicine. Articles published in a legitimate scientific journal have high credibility because they are from identified authors, are peer‐reviewed, and are integrated within the literature related to the topics of the articles. The conflict in this process arises because articles contain information that belongs to the authors and the authors' institutions, and may represent intellectual property that will ultimately be marketed commercially. The journal has an obligation to protect this property and its potential value to the authors and institutions. This protection is provided by the journal's copyright over the information. When this protection is compromised by plagiarism of the article's information by another author, the journal must be prepared to act through enactment of a plagiarism policy approved, in the case of Medical Physics, by the journal's Board of Editors and by the sponsoring society (American Association of Physicists in Medicine). It is possible for authors to plagiarize their own work, through duplicate publication in more than one journal. For this purpose, Medical Physics requires submission of a Conflict of Interest statement that includes disclosure of an article's publication elsewhere before submission to Medical Physics.
MO‐E‐224C‐01: Quantitative Evaluation of Conformal Treatment Plans: A New Methodology
Authors: Menhel J , Levin D , Alezra D , Symon Z , Pfeffer R
Published: July 2006

Purpose: To establish a quantitative method for evaluation of 3D conformal and IMRT plans based on organ specific tolerances and target coverage assessment. Method and Materials: We propose a novel evaluation criterion, which reflects both target coverage and overdoses in organs at risk (OARs). Critical Organ Scoring Index (COSI) is defined as: , where V>tol is the volume of OAR receiving more than tolerance dose and TC is the partial volume of target receiving at least prescription dose. To assess overall plan conformity we propose a 2D graphical representation of COSI vs. Conformity Index (CI). This method enables quantitative evaluation of competing plans in terms of multiple organs at risk. The COSI‐CI plots were tested for evaluation of the following treatment sites: maxillary sinus and pancreatic tumors, to compare non‐coplanar 3D and IMRT plans, and cavernous sinus meningiomas for stereotactic radiation with either dynamic arcs or IMRT. Results: For all three sites COSI‐CI plots assisted the physician in choosing the optimal plan, in terms of both target coverage and critical organ sparing. We verified each choice by analyzing individual DVHs and isodose distributions. Comparing our index to the widely used Conformation Number, we found that in all cases where there were discrepancies between CN and COSI in the choice of optimal treatment plan, the COSI‐CI graphs led to the better plan. Conclusion: We introduced a novel scoring index, COSI, which is a measure of both target coverage and critical organ overdose. Using the COSI index, we propose a two‐dimensional representation of plan quality for comparison purposes. The method was found it to be a quick and reliable tool in aiding physicians in the choice of correct plans. The main advantage of the proposed methodology is its ability to simultaneously compare multiple plans as well as multiple critical structures.
MO‐E‐224C‐05: Comparison of TomoTherapy with Conventional Electron/X‐Ray Treatment Plans for Chest Wall
Authors: Ashenafi M , Boyd R , Lo K , Lee T , Hogstrom K
Published: July 2006

Purpose: Post‐mastectomy radiotherapy (PMRT) of the chest wall (CW) often will involve use of electron beams due to their rapid fall‐off of dose near the practical range of the electron energy. The TomoTherapy helical, fan‐beam delivery system, along with the inverse‐planning optimizer, has the potential to provide planning and delivery of 6 MV x‐rays to superficial target volumes conventionally treated with electrons. In the present study, five chest wall patients were planned for TomoTherapy and compared to their conventional plan that utilized electron beams. Analysis of breathing motion were not included. Methods and Materials: Five PMRT patients treated with electron beams and planned on the Pinnacle treatment planning system (TPS) were selected. A planning target volume (PTV) was generated to follow the isodose contour defined by 90% of the prescribed dose on the Pinnacle plan. Target dose homogeneity in the Tomotherapy TPS dose optimizer was relaxed to better achieve critical structure dose objectives when necessary. Normal tissue complication probabilities (NTCP) were calculated for the lung and the heart. A questionnaire form was provided for the radiation oncologist to evaluate each plan. Results: For all cases, the TomoTherapy plan was rated superior to the Pinnacle plan by the radiation oncologists. The TomoTherapy TPS produced a significantly more uniform dose distribution in the PTV. The average volume of ipsilateral lung receiving dose above 20 Gy was reduced from 21.5% to 17.7%. The average volume of heart receiving dose above 30 Gy was reduced from 2.2% to 1.3%. NTCP for the lung and heart were also reduced in the TomoTherapy plan. Conclusion: The results of this study demonstrated that TomoTherapy is able to deliver clinically‐acceptable dose distributions to a “static” model of PMRT patients conventionally treated with electron beams.

Supported in part by a research agreement with TomoTherapy, Inc.
MO‐E‐224C‐06: Improving Homogeneity of Abutment Dosimetry in Segmented‐Field Electron Conformal Therapy Using Variable Insert Positioning
Authors: Richert J , Hogstrom K , Boyd R
Published: July 2006

Purpose: To improve dose homogeneity in segmented‐field electron conformal therapy by matching penumbra of abutted fields. Method and Materials: A Varian 21EX electron applicator was modified to allow for energy‐dependent positioning of Cerrobend inserts resulting in energy‐dependent air gaps. Air gaps were chosen based on theoretical calculations to approximately match penumbra for 6, 9, 12, 16, and 20 MeV beams at 1.5‐cm depth in a water phantom at 100‐cm SSD. Treatment plans developed for four simulated target volumes using the modified applicator were compared to identical plans using the standard applicator. Improvement in dose homogeneity was assessed by comparing maximum and minimum dose, mean dose, and sigma of the dose distribution in the target volume for the two plans. Subsequently, electron blocks were cut with diverging edges using the Compu•cutter® system, and dose plans using the modified applicator were delivered to Kodak XV film in a polystyrene phantom to demonstrate feasibility. Results: Treatment planning results using the modified applicator showed improved dose homogeneity in all four simulated target volumes as compared to plans using the standard applicator. Averaged for all four PTVs; dose spread (Dmax − Dmin) decreased by 35%, σ of the dose distribution decreased by 29%, and D90–10 decreased by 31%. Dose delivered to a film phantom using the modified applicator was found to agree well with predictions (within approximately 5%) of the Pinnacle treatment planning system in the abutment region of the PTV (±2 cm from the abutment edge at depths ⩾1.5 cm). Conclusion: The results of this study suggest segmented‐field electron conformal therapy can be delivered with significant improvement in dose homogeneity as compared to the current method by using energy‐dependent positioning of electron inserts to match beam penumbra.
MO‐E‐224A‐01: Stereotactic Body Radiation Therapy: (1) Clinical Outcomes Following SBRT IGRT
Authors: Dawson L
Published: July 2006

Advances in high precision radiation planning and delivery, image guidance technologies and methods to account for and reduce organ motion have made it possible for cranial stereotactic radiosurgery techniques to be applied to tumors outside of the brain. Stereotactic body radiation therapy (SBRT) refers to the use of a limited number of high dose fractions delivered very conformally to targets with high accuracy, using biologic doses of radiation far higher than those used in standard fractionation.

The rationale for SBRT is that there is a need for improved local therapies for many primary cancers and also in the situation when there are ‘oligo’ (i.e. isolated) metastases, specifically in sites where surgery has been shown previously to be able to cure patients with ‘oligo’ metastases, e.g. colorectal cancer, renal cell cancer and sarcoma. SBRT has the potential to be used in place of surgery in situations when surgery may associated with high risk.

Advancements outside of radiation oncology also provide rationale for SBRT. Functional imaging such as PET allows better patient selection for SBRT. Furthermore, improvements in systemic therapy more likely to control micro‐metastases provide rationale for improving local therapies, such as SBRT, to reduce large foci of tumor burden.

There are radiobiological advantages to SBRT including less opportunity for tumor repopulation and repair. Furthermore, the shorter SBRT treatment times are more convenient for patients and have resource utilization advantages.

With highly potent doses of SBRT delivered with steep dose gradients, the potential for geometric uncertainties in the setting of SBRT to lead to adverse clinical outcomes (tumor recurrence and/or toxicity) is high. Thus, the need for image guided radiation therapy (IGRT) to improve precision of dose delivered is heightened. IGRT decreases the heterogeneity in delivered doses, improving our ability to measure the impact of dosimetric and non‐dosimetric factors on SBRT clinical outcomes.

This lecture will provide an overview of the rapidly increasing clinical experience with SBRT and IGRT in the setting of SBRT. Case examples demonstrating clinical benefits and potential toxicities will be discussed.

Educational Objectives:

1. To understand the clinical rationale for SBRT.

2. To describe the rationale for IGRT in SBRT.

3. To understand the increased risks of SBRT compared to conventional RT and the increased potential for error.
MO‐E‐230C‐00: Display Evaluation Demonstration Workshop: Part II
Authors: Samei E
Published: July 2006

Participants:

J Charette, Barcoview, LLC;

E Samei, Duke University;

N Hashimoto, Eizo Nanao;

K Compton, National Display Systems;

A Abileah, Planar Systems;

D Sorensen, Richardson Electronics / Image Systems;

C Lipfert, Scanditronix Wellhofer GmbH;

M Hasegawa, Totoku;

H Roehrig, University of Arizona GmbH; M Hasegawa, Totoku; H Roehrig, University of Arizona

Electronic display is a key component of modern medicine, providing soft‐copy viewing of medical images. Being the last component of the image chain, display quality can have a notable impact on overall accuracy and efficiency of the diagnostic process. Thus, it is necessary to ensure that the physical performance of a medical display is adequate for its intended use. Led by a task group initiative by the American Association of Physicists in Medicine (AAPM TG18), new guidelines have recently been published defining objective and standardized assessment procedures and criteria for acceptance testing and quality control of medical display devices (Samei et al, Med Phys 32:1205–25, 2005). The guidelines include detailed visual and quantitative methods and specific acceptance criteria for basic display characteristics including luminance, luminance spatial and angular response, resolution, noise, veiling glare, reflection, color uniformity, geometrical distortions, and display artifacts. The TG18 guidelines are also being gradually reflected in a number of other national and international directives including those by the IEC and the ACR. The goal of this demonstration workshop is multi‐fold: 1) to present a tutorial on the TG18 guidelines and its adaptations, 2) to discuss its implementation by specific vendors, 3) to offer an opportunity for hands‐on exposure to the practical aspects of display performance evaluation, 4) to provide an opportunity to informally interact with experts and ask questions, and 5) to offer a panel discussion on the issues about which there might be less consensus among experts. Representatives from the TG18 committee and from industry will be present to demonstrate and discuss display evaluation issues.

Part II:

4:00–4:10 Local and Remote QA/QC for Color Monitors, H Roehrig, Univ of Arizona

4:10–4:20 QA Luminance Measurements at Medical Displays using a Flexible Spot Luminance Meter, C Lipfert, Scanditronix Wellhofer GmbH

4:20–5:10 Hands‐on demonstration:

5:10–5:30 Plenary Q&A and panel discussion
MO‐E‐230C‐01: Local and Remote QA/QC for Color Monitors
Authors: Roehrig H
Published: July 2006

The adoption of digital detectors and PACS has provided physicians in healthcare institutions with an effective means to electronically generate, transmit, archive, retrieve and display images to be used for the diagnosis of disease. Monochrome CRTs and LCDs were the original choice of displays. Now color displays are increasingly replacing monochrome displays mainly for cost reasons in Radiology, but also for use in multi‐modality display stations and in areas where color is essential such as in Telemedicine and Telepathology.

The ACR‐NEMA Working Group 11 has developed a Display Function Standard to allow for the standardization of monochrome image display devices. The AAPM Task Group 18 has developed methods to permit implementation of image Quality Assurance Programs as well as Acceptance Procedures for monochrome display devices.

No Display Function Standard is available for the standardization of color display devices nor are there recommendations for image Quality Assurance Programs or Acceptance Procedures for color display devices.

This presentation demonstrates that consistent color presentation as well as consistent grayscale presentation for digital color displays can be achieved with the appropriate software and a simple and portable color detector. The software to achieve color fidelity works fast and, with the aid of the portable detector, can be applied remotely, saving precious resources in the management and operation of color displays.

The presentation also provides a look into the future when a handheld color camera will be available to permit in‐field evaluation of pertinent image quality measures like modulation transfer function and signal‐to‐noise ratio of color display devices in the reading room.
TU‐A‐330A‐01: Digital Mammography Quality Control and Accreditation
Authors: Butler P
Published: July 2006

Since 2003, the number of full‐field digital mammography (FFDM) units in the United States has been increasing by about 4% per month. As of May 1, 2006, there were 1379 full‐field digital mammography units at 977 MQSA‐certified facilities in the United States. With the fall 2005 announcement that FFDM increased the effectiveness of detecting breast cancer in women with dense breasts (as well as premenopausal women and women under the age of 50), the rate of increase for digital units is expected to increase even further. FFDM systems are subject to the Food and Drug Administration's mammography regulations, as are analog systems). This presentation will discuss the steps medical physicists must take to ensure their facilities may expeditiously accredit their FFDM units. In addition, the presentation will cover preliminary QC recommendations made by the ACR's Subcommittee on Digital Mammography in preparation for their upcoming Digital Mammography FFDM Quality Control Manual.
TU‐A‐ValA‐01: DICOM: What the Physicist Needs to Know
Authors: Junck K
Published: July 2006

The DICOM (Digital Imaging and Communications in Medicine) standard has allowed for tremendous changes to occur in the workflow of a modern radiology department. Prior to DICOM, radiological images were generated, transmitted, and stored in proprietary formats by imaging vendors. DICOM provides a standard to define objects such as images and services that may be performed upon those objects. As with any disruptive technology, it has solved some problems and created a whole host of new issues. Some of these issues are being addressed within the DICOM standard while others have taken on a new life under the auspices of IHE (Integrating the Healthcare Enterprise). IHE is an initiative by healthcare professionals and industry to improve the way computer systems in healthcare share information.

This lecture is intended to provide an overview of the DICOM “language” and look at some current DICOM issues at our institution.

Educational Objectives:

1. Review the history of the DICOM standard and understand its origins and goals.

2. Understand the language of DICOM objects and services.

3. Understand the possible sources of DICOM issues.

4. Learn of available online resources for additional information.
TU‐A‐224A‐01: Positron Emission Tomography for Oncologic Imaging and Treatment
Authors: Bourland J
Published: July 2006

Purpose: Positron Emission Tomography (PET) images show physiological and biological information through the in‐vivo distribution of radioactive, short‐lived, positron‐emitting species. PET imaging shows focal and distributed regions of cancer and its metastases. PET uses in oncology include diagnosis, staging, and disease monitoring, important for prognosis and treatment decisions. Quantitative uses of PET include assessment of the degree of malignancy and target definition for radiation treatment. Hybrid PET‐CT devices are being used as radiation treatment simulators. Method and Materials: F‐18‐labled Fluoro‐deoxyglucose (F‐18 FDG) is the most commonly used PET imaging agent. FDG shows regions of active glucose metabolism, such as local cancer, metastases, non‐cancer inflammation, and normal glucose use in brain. Non‐FDG PET agents can be highly specific in tissue targeting (binding), such as F‐18 Misonidazole and C‐11‐labeled amino acids, to image tumor biology like hypoxia and cell proliferation, respectively. Results: 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. Voxel intensity and image fidelity depend on equipment design, patient size, anatomic site, and imaging study parameters. PET‐CT units enable CT‐based attenuation corrections and inclusion of CT information in a registered PET‐CT dataset. Interest is high for PET‐CT simulators. The Standardized Uptake Value (SUV) is a normalized intensity measure for quantitative indication of disease, and can be used for target delineation, with certain constraints. Conclusion: This course reviews the basic physics of PET, uses of FDG and non‐FDG PET for oncology imaging, and quantitative aspects for PET‐based radiation target definition. 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.

Educational Objectives:

1. Review the basics physics of PET imaging.

2. Describe FDG PET imaging and oncologic indications.

3. Review the uses and limitations of PET images in radiation treatment.

4. Describe the SUV and other threshold parameters for target delineation.

5. Review non‐FDG PET imaging of tumor biology.

Conflict of Interest: Research sponsored in part by Varian Medical Systems and GE Healthcare.
TU‐A‐224C‐01: Daily Localization II: EPID, MVCBCT
Authors: Pouliot J
Published: July 2006

The Mega‐Voltage Cone‐Beam CT (MVCBCT) system provides a 3D image of the patient anatomy in the actual treatment position that can be tightly aligned to the planning CT, allowing daily verification and correction of the patient position moments before the dose delivery. Integrated onto a linear accelerator, the system consists of a new a‐Si flat panel adapted for MV imaging and a workflow application allowing the automatic acquisition of projection images at low dose rate, CBCT image reconstruction, CT to CBCT image registration and couch position adjustment. Moreover, MVCBCT provides accurate electron density and allows studies of dosimetrical impact of setup error, anatomical changes or presence of implanted metallic objects.

This lecture will provide an overview of the physics characteristics of MV and MV CBCT imaging, acceptance testing and commissioning, acquisition and reconstruction, image registration, alignment precision and quality assurance procedures. An overview of the clinical applications will be provided. Finally, current challenges and future developments will be addressed.

Educational Objectives:

1. Understand the basics concepts of MV Cone‐Beam CT imaging.

2. Understand the workflow and issues related to clinical applications of MV CBCT, including acquisition, reconstruction, registration and patient alignment.

3. Understand the possibilities of 3D Imaging for patient alignment.

This work was supported by Siemens Oncology Care Systems.
TU‐B‐330D‐01: Design and Performance Characteristics of Flat‐Panel Acquisition Technologies
Authors: Yorkston J
Published: July 2006

Flat‐panel detectors are becoming more commonplace throughout the world for numerous applications ranging from mammography to megavoltage imaging and from static projection radiography to real‐time fluoroscopy and cone beam CT. A detailed understanding of their advantages and limitations is essential to ensure their efficient integration into the clinical environment. This presentation will review their place in the current DR detector landscape and the unique features that provide them with their improved image quality performance when compared to other approaches. The differences and similarities between the various flat‐panel designs will also be discussed with a view to highlighting their inherent image quality capabilities as well as some practical limitations to their performance. The process of gain/offset corrections will be reviewed and the issue of bad pixels, defective lines and image artifacts commented on. The implications of certain gain calibration procedures will be reviewed in terms of the possibility of image artifact creation, in particular in terms of other system components such as anti‐scatter grids and AEC circuitry. The impact of non‐linear behavior and pixel saturation will also be reviewed. In conclusion the development of advanced imaging applications such as dual energy, tomosynthesis and cone‐beam CT will be reviewed.

Conflict of Interest: John Yorkston is an employee of Eastman Kodak Company which sells DR systems based on CsI(Tl) type Flat‐Panel detectors.

Educational Objectives:

1. Review the range of DR and flat‐panel detectors currently available and their design and performance differences.

2. Review the process of gain/offset calibration and its benefits and limitations.

3. Review the impact of pixel and line defects, correlated line noise, pixel saturation and other characteristics behaviors of flat‐panel detectors.

4. Review the prospect of advanced applications utilizing flat‐panel technology.