bluuebunny/crossref_metadata_2025 huggingface dataset:
MO‐D‐ValB‐03: Genetic Evolutionary Taboo Search: A Novel Approach for Optimal Marker Placement in Infrared Patient Positioning
Authors: Riboldi M , Spadea M , Tagaste B , Baroni G , Garibaldi C , Orecchia R , Pedotti A
Published: July 2006

Purpose: To develop the methods of a novel approach for optimal marker placement in infrared patient positioning. Method and Materials: A nondeterministic optimization technique (Genetic Evolutionary Taboo Search, GETS), combining genetic algorithms and taboo search, was implemented. A population‐based evolution is generated, where adaptive memory features guide the evolutionary process to thoroughly explore the solution space. Preset taboo solutions are introduced to reject marker configurations resulting collinear from the point of view of infrared cameras. The GETS algorithm was tested on 10 prostate patients: treatment planning CT scans were segmented to provide 3‐D representation of PTV (prostate + seminal vesicles), OARs (bladder and rectum) and skin surface model. Segmented data were fed to the GETS algorithm to obtain optimized configurations of markers, minimizing the target registration error (TRE), to be compared to a random configuration. The changes in the optimal marker configuration when OARs are included within the target were also investigated. Results: The GETS algorithm yielded a significant improvement in TRE values: optimal configurations ensured a 26.5% mean TRE decrease. Common features in the optimal marker configurations were found for the 10 patients group, being optimized solutions symmetrically distributed, with markers mostly placed on lateral sides. Optimal marker configurations when OARs were included within the target resulted in a similar spatial distribution, if compared to the PTV‐only condition. The implemented memory‐based design resulted in improved gene expression over the evolution process, with respect to memoryless genetic algorithms. Conclusion: The GETS algorithm revealed high performance in solving the optimal marker placement problem, leading to improved marker configuration for stereophotogrammetric patient positioning in radiotherapy. Memory features ensured enhanced capabilities in exploring the solution space, if compared to conventional genetic optimization. The application of the new algorithm to a 10 patient group provided practical indications toward better marker placement for prostate cases.
MO‐D‐ValB‐06: Concurrent Tracking and Fluoroscopic Imaging of Implantable Wireless Electromagnetic Transponders
Authors: Malinowski K , Parikh P , Santanam L , Lechleiter K , Hubenschmidt J , Dimmer S , Chaudhari A , Mayse M , Bradley J , Low D
Published: July 2006

Purpose: Multiple technologies are being utilized to improve real‐time tumor tracking. To date, there have not been methods to prospectively compare different technologies with realistic tumor trajectories. We evaluated the capabilities of the Calypso® Medical 4D Localization System (Calypso Medical, Seattle, WA) and Varian Trilogy System (Varian Medical Systems, Palo Alto, CA) fluoroscopy in tracking dynamic objects. Method and Materials: Initially, a quality assurance fixture containing three implantable transponders was moved by an in‐house developed 4D phantom through an ellipse and a non‐uniform human lung tumor path modeled with CT imaging and spirometry. Subsequently, three transponders that had been implanted in a canine lung were tracked. In both experiments, the transponders were fluoroscopically imaged on a Trilogy system while simultaneously being tracked by the Calypso® 4D localization system. The fluoroscopic images were recorded and later analyzed using a custom‐written (MATLAB) image processing program to determine the transponder projection positions with respect to time. The trajectories derived from the fluoroscopic images were synchronized with and compared to the Calypso System position data. Results: The root mean square (RMS) position differences were less than 0.03 mm for all tested measurement system combinations. While both were small, the Calypso System RMS error was slightly lower than that of the fluoroscopy when compared against the 4D phantom positions. Of the three trajectories, the RMS error between imaging modalities was largest for the patient trajectory and smallest for the ellipses. Conclusion: This work indicates that both tracking methods provide excellent positioning accuracy. Although the accuracy discrepancy between the two systems is negligible, the Calypso® System also offers the ability to localize in three dimensions and has the advantage of being able to track a target continuously without the use of ionizing radiation. Conflict of Interest: Supported in part by Calypso Medical Technologies, Inc.
MO‐D‐ValB‐09: Residual Motion of Lung Tumors in End‐Of‐Inhale Respiratory Gating
Authors: Berbeco RI , Nishioka S , Shirato H , Jiang SB
Published: July 2006

Purpose: The intention of this study is to determine whether previously observed large external surrogate residual motion at end‐or‐inhale (EOI) translates into large tumor residual motion, and if improving the reproducibility at this phase can lessen the internal residual motion. Method and Materials: We simulate gated treatment at the EOI phase, using a set of recently measured internal/external correlated patient data. The 3D locations of internal fiducial markers placed near the target are tracked in real‐time with stereoscopic x‐ray fluoroscopy. An external surrogate respiratory gating system is synchronized with the fluoroscopic unit so that the log files contain the three‐dimensional marker position and the abdominal surface position at every time point. The internal and external measurements are taken even when the MV beam is gated off, throughout each treatment, so large amounts of internal/external‐correlated data were collected. Results: We found that under free‐breathing conditions the residual motion of the tumors is much larger for EOI phase than for end‐of‐exhale (EOE) phase. The mean value of residual motion at EOI was found to be 2.2 mm and 2.7 mm for amplitude and phase‐based gating, respectively; and, at EOE, 1.0 mm and 1.2 mm for the same quantities. However, the residual motion in the EOI gating window is correlated well with the reproducibility of the external surface position in the EOI phase. Using the results of a published breath‐coaching study, we deduce that the tumor residual motion at EOI would approach that at EOE under breath‐coaching conditions. Conclusion: We conclude that the same reproducibility of tumor location can be achieved at EOI as at EOE if breath coaching is implemented. Based on these results, we believe that inhale gating is preferable to exhale gating as long as proper margins are employed and breath coaching is performed.
MO‐D‐ValA‐02: Patient Motion Modeling & Treatment Adaptation
Authors: Yan D
Published: July 2006

Patient anatomical variation during the radiotherapy course can be modeled using a stochastic process. In this process, spatial position of each subvolume in patient organs of interest is defined as a random vector described using a probability distribution function (pdf). Two main parameters, the mean and the standard deviation, of the pdf have been historically used to characterize patient anatomical variation during the radiation treatment. It has been demonstrated that treatment dose distribution in an organ of interest can be evaluated approximately using these two parameters alone, without the full knowledge of organ motion distribution. The approximation is, however, dependent on the scale of the standard deviation as well as the number of treatment delivery fractions. It is straightforward to estimate these two parameters if patient anatomical variation process is stationary. In this case, the two parameters are constants or time‐invariance during the treatment course. However, the estimation will be relatively difficult if patient anatomical variation process is non‐stationary.

Patient anatomical variation in radiotherapy can be systematically managed using image feedback adaptive treatment technique. The fundamental difference between adaptive treatment technique and other image‐guided techniques is the use of patient‐specific treatment information. Adaptive technique intends to use all patient‐specific dose information ‐ including what has been delivered in the previous treatments, what can be delivered at the present treatment, and what would be delivered in future treatments ‐ in the design of treatment plan. Therefore, treatment plan designed in adaptive radiotherapy is called 4D adaptive plan, which is in principle a treatment control law to manage treatment process. Mathematically, treatment control law is a spatial mapping from the parameter space of patient variation to the parameter space of treatment delivery control, which can be determined including the patient variation in the planning optimization or inverse planning. The objectives in adaptive planning optimization are constructed based on a selection of control strategies that could be either the online or the offline with one control action, multiple actions or continue actions. Selection of control strategy and number of control actions is, of course, dependent on the nature of patient variation process as well as the estimation uncertainties, and has to be determined considering also the clinical practice.

The lecture will provide an overview of the models and characteristics of patient anatomical variation process during the radiotherapy, the 4D dose summation methodology and the strategies of adaptive treatment process.

Educational Objectives:

1. Understand the characteristics and dynamic model for patient anatomical variation during the course of radiotherapy.

2. Understand the model and methodology of 4D dose summation.

3. Understand the options of control strategy for image guided adaptive radiation treatment.
MO‐D‐230A‐02: An Immersive Virtual Environment for Training of Radiotherapy Students and Developing Clinical Experience
Authors: Beavis A , Ward J , Bridge P , Appleyard R , Phillips R
Published: July 2006

Purpose: Radiotherapy equipment and techniques are rapidly developing and so efficient training is invaluable. However, the demands on clinical systems and the lack of trained personnel make it difficult to achieve. As an alternative approach we have developed virtual reality training tools, fully interactive and operating on a life size scale these can provide valuable experience for students and staff. We designed a study for 42 first year therapist students to investigate the usefulness of our training environment for learning a clinical technique that typically causes problems. Method and Materials: We have created a virtual environment that simulates an actual radiotherapy treatment machine, controlled via an actual handheld control pendant. The study was developed to simulate a “skin apposition” electron beam treatment. A virtual patient, based on the visible human female dataset, complete with rectangular markings for a range of different treatment sites, provided a range of treatment scenarios. At the Hull Immersive Visualization Environment (HIVE) we are able to project our graphics display onto a 5.3 m by 2.5 m ‘Power Wall’ utilizing stereoscopic visualization enabled via LCD shutter glasses. Such immersive interaction techniques (including the use of the Linac hand pendant) add to the user's sense of reality. To provide feedback, we have implemented a ‘scoring algorithm’ to assess how well the user has set up the beam/ patient. Results: The students reported the training environment to be realistic and following its use 93% perceived an improvement in their understanding of this clinical technique and 69% found the control system easy to master. Conclusion: Having implemented such training software and hardware we are beginning to perform academic studies to assess the impact of its use in the educational forum. We wish to understand which areas of multi‐discipline training will benefit from such an approach.
MO‐D‐230A‐05: Medical Error Detection and Reduction Plan in Community Cancer Center
Authors: Bialkowski M , Lasher D , Wojcicka J
Published: July 2006

Purpose: An error reporting program, called the Medical Error Reduction Plan, was developed in our department. The program includes errors made during the patient treatment preparation process and delivery. The purpose of this study is to understand the types of errors, error frequency and trending, correlation between errors, error severity and impact on treatment quality, and to derive an error reduction strategy based on non‐punitive principles. Method and Materials: The plan supplements all required QA processes and procedures in Radiation Oncology. After patient treatment plan approval, the Therapists Check Station performs a final comprehensive check that includes: plan revision, patient setup, data entered to R&V system, approvals and scheduling. Problems are recorded in a Discrepancy Log Book that includes also errors in simulation and incomplete directives/forms. All these data are presented, discussed and analyzed at the monthly departmental meetings. We have two full years of data combined into the following categories: simulation, planning, approvals, logistics, documentation and treatment. Errors in patient treatments have been recorded in our Department as Unintended Deviations. They are presented on graphs together with data from our error reduction plan. Results: During the past two years, 350 errors were reported. Most of them (60%) were clerical, simulation and treatment planning errors accounted for 11% and 17%, respectively. At the end of the analyzed period, there was more than 50% overall reduction of treatment errors. The introduced error reporting program increased personnel alertness to treatment process details. Conclusions: The idea of a “user friendly” error detection and reduction program has proven excellent. Despite of multiple QA procedures and the R&V system, the possibility to make errors still exists. It is imperative to detect them before treatment. This process should be ongoing in view of increasing novelty and complexity of treatments.
MO‐D‐230A‐06: Statistical Consistency Reviews (SCR) as a Chart Checking Tool
Authors: Glasgow G , Gao M , Ke Y , Rusu I , Sethi A
Published: July 2006

Purpose: Chart checking is key in radiation oncology QA. AAPM TG 40, Comprehensive QA…Oncology, TG53, QA for…Planning, and ACR Technical Standard Therapy address chart checking. They recommend verifying monitor unit (MU) calculations by a second person or method before delivering 3 fractions or 10% total dose. Time‐consuming verifications are difficulty for multiple beam, heterogeneity corrected 3D and IMRT isodoses. We investigate statistical consistency reviews (SCR) of common treatments as one of several chart‐checking tools. Method and Materials: We collect data (gantry and collimator angles, SSD, field sizes, weights, fractions, dose/fraction, depths, outputs, MUs) for sites. We investigate parameter statistical consistency for the same treatment to similar patients. We report prostate four field treatments (66.6 Gy or 74 Gy/37 Fx) and IMRT five‐field (0, 75, 140, 220, 285 degrees) treatments (76 Gy/38 Fx). Results: Four field prostate treatments are surprisingly consistent. SSDs varied about 3% and MUs about 6%. Average AP SSD was 87. 9 +/− 1.9 cm (2%) requiring 47.4 +/− 2.5 (5%) MU for 45 cGy. Average lateral SSD was 80.7 +/− 2 cm (2.5%) yielding 63.3 +/− 2.5 MU (4%) for 45 cGy. IMRT treatments MU variations were about 20%. Conclusion: How to use these data? Rather than check our historically accurate algorithm calculations against another algorithm, we review four‐field prostate MU calculations against statistical norms. A recent patient's AP 57 MU were greater than three standard deviations above the norm, 47 +/− 2.5 MU. His AP 79 cm SSD was well below the norm, 87.9 +/− 1.9 cm. A planning error? No, he was just obese, but it illustrates the value of knowing average parameters. IMRT plans appear more consistent than expected; SCR may have value for IMRT plan reviews. Statistical data will be presented for other sites (breast, head/neck, etc.) commonly treated with consistent methods.
MO‐D‐230A‐08: A Technique for Tracking and Predicting Physician Referrals
Authors: Ramsey C , Seibert R
Published: July 2006

Purpose: To create a tool for collecting physician referral data, identifying strengths and weaknesses in physician referral patterns, and for predicting future referrals in real‐time. Methods and Materials: Since January 2001, the referring physician was recorded for each patient that was seen for consultation in a radiation oncology department. In addition to the physician, the referring physician group was also recorded. The total referrals for each month were summed for each individual referring physician and physician group. In addition to referral data, physician hospital in‐patient admitting data for oncology related diagnoses were obtained from the state's medical statistics. For physicians that have privileges at multiple hospitals, the “Market Share” was calculated. The number of referrals received each month was predicted using a locally weighted regression (LWR) model. The regularization parameters of the LWR model were determined through a continuous genetic algorithm that minimized the mean squared error using data not used in the LWR model. To protect confidentiality, a sample data set was crafted to simulate possible radiation oncology scenarios. Results: The results of this study are confidential business data, and so, a sample dataset is used to demonstrate referral pattern tracking. The results concluded that 95% of patient referrals originate from one of five specialties, the largest being medical oncology (43%). The top referring group in each medical specialty was responsible for 65% of patient referrals, and refer >95% of their patients inside the same health system. The remaining 35% of the hypothetical radiation oncology's referrals are physicians who practice in multiple health systems. The LWR model accurately predicted the number of referrals with a mean squared error of 2.2%. Conclusions: The collection and analysis of physician referral data provides a useful tool for maximizing radiation oncology growth and efficiency through known parameters.
MO‐D‐230A‐09: ACR Mammography Accreditation Program's Early Digital Mammography Results
Authors: Butler P , Yaffe M
Published: July 2006

The Mammography Quality Standards Act (MQSA) of 1992 requires that all mammography facilities in the United States (including those using full field digital mammography [FFDM] equipment) be accredited by an approved body, certified by the U.S. Department of Health and Human Services (HHS), and receive an on‐site inspection by a state agency acting on behalf of the HHS (or by HHS inspectors). The FDA approved the first premarket approval application for a FFDM unit in January 2000. Immediately accrediting these units presented a dilemma for the American College of Radiology (ACR) since, historically, programs are only developed for mature, widely‐available technologies, so that reasonable standards may be developed based on expert experience. Consequently, the ACR could not have an accreditation program available for this new technology at the time FDA approved it to be sold in the US. To provide time for accreditation development, the FDA provided a process to exempt FFDM units from the MQSA accreditation requirement if an accreditation program was not yet available for the specific FFDM model. The FDA approved the ACR to accredit the General Electric Senographe 2000D, the Fischer SenoScan and the Lorad Selenia FFDM units in 2003; the General Electric Senographe DS in 2004 and the Siemens Mammomat Novation in 2005. Although some of the accreditation instructions and submissions are different for digital accreditation, each unit is still required to pass clinical image quality, phantom image quality and dose. Data since 2003 shows that the deficiency rate for FFDM units making their first attempt at accreditation is lower than with screen‐film applicants (approximately 7% vs. 11%). Accreditation results from over 1200 units at 900 facilities will be presented.
MO‐D‐224A‐03: Dependence of Planar IMRT QA On MLC Positional Inaccuracies
Authors: Ahunbay E , Jursinic P , Li XA
Published: July 2006

Purpose: This work aims to investigate the sensitivity of IMRT QA done by means of planar dosimetry to MLC positional inaccuracies. Also we propose an accurate method for measurement of MLC positioning errors using the 2D diode array. Methods: A method to measure the MLC position errors by using 2D‐arrary of 455 diodes (MapCheck, Sun Nuclear) is developed. Our method utilizes the fact that each diode's signal will be most sensitive to the MLC position error when its center coincides with the edge of a MLC leaf where a small deviation from the accurate position produces sharp increase or decrease in the diode output. We designed various multi‐segmented test patterns based on this principle that can evaluate the MLC deviations with sub‐mm accuracy at multiple MLC banks simultaneously. By using this information as a deviation histogram, we created deliberately erroneous IMRT fields with varying standard deviations of MLC leaf position error. MapCHECK planar dose analysis is performed and the sensitivity of the IMRT QA procedure to MLC position inaccuracy using MapCHECK device is evaluated. Results: Our results indicate that for SIEMENS Primus and MD machines, the MLC positional errors show a standard deviation of about +/− 0.7mm. Right after the MLC calibration, this deviation might reduce to 0.55mm. It has been found that a single leaf position can vary by as much as 1mm between two consecutive measurements. Fields with less number of segments that are generated by Direct Aperture Optimization are found to be less sensitive to these errors by measurements with deliberately modified fields with random MLC inaccuracies. Conclusion: A method to accurately quantify MLC position is proposed and used to obtain a distribution of leaf position errors for many leaves at multiple banks. The sensitivity of planar dosimeter to the MLC positioning errors is investigated.
MO‐D‐224A‐04: EPID Transmission Dosimetry for QA Use in Adaptive Radiotherapy
Authors: Price R , Paskalev K , Fourkal E , Feigenberg S , Ma C
Published: July 2006

Purpose: Radiotherapy patients treated for H&N cancer often lose weight and have shrinkage of their tumors causing drastic anatomical changes. This can result in changes in dose distribution with respect to PTV coverage and OARs. Monitoring these changes is difficult and presents QA problems for IMRT treatments. In this work we develop a method to monitor H&N thickness changes and correlate with changes in dose distribution. Method and Materials: Wax was applied to the neck region of an anthropomorphic phantom in 3‐1cm layers. Contours depicting tumor and critical structures were delineated. An IMRT plan was generated to delivery 70Gy to the PTV. The resultant sequence was virtually delivered to the phantom with layers of wax removed. PTV coverage, hot spot, and PRV doses were recorded. A characteristic response curve was generated using the amorphous silicon EPID on a Varian 21EX linear accelerator and slabs of solid water. The phantom was then consecutively imaged removing 1cm layers of wax. All images were acquired for the same number of MU. Results: Decreasing the thickness of the neck region bilaterally by 3cm resulted in an increase in 95% PTV coverage from 70Gy to 72.8Gy. The maximum dose in the PTV increased from 80.6Gy to 86Gy. The PTV volume receiving 110% of the prescribed dose increased from 13.4% to 66.6%. The dose to 0.01cc of the spinal cord and brainstem PRVs increased from 45.8Gy to 47.9Gy and 49.7Gy to 51.2Gy, respectively. Using the EPID we were able to predict changes in the lateral dimension of the phantom to within 4mm. Conclusion: Our results indicate that anatomical changes during treatment may lead to unacceptable dose distributions. By using lateral EPID images we can monitor the thickness changes (path length) in the H&N region. These changes may be used to determine when re‐planning is necessary.
MO‐D‐224A‐05: In‐Vivo Dosimetry Using Electronic Portal Imaging and Monte Carlo Techniques
Authors: Jarry G , Verhaegen F
Published: July 2006

Purpose: The purpose of this work is to develop and validate an algorithm based on Monte Carlo (MC) simulations to compute the in‐vivo dose given to patients during conventional treatments and IMRT from portal images. Method and Materials: The exit fluence from primary particles is obtained from the portal image after correction for scatter radiation. The scattered radiation at the portal imager and the spectral energy distribution of the primary particles are estimated from MC simulations at the treatment planning stage. The exit fluence and the spectral energy distribution of the primary particles are then used to ray‐trace the particles from the portal imager towards the source through the CT geometry of the patient. Particle weights reflecting the probability of a particle being transmitted are computed during this step. A dedicated MC code is finally used to transport back these particles from the source through the CT geometry of the patient to obtain an in‐vivo dose. Only Compton interactions are considered and secondary electron transport is implemented by depositing the dose uniformly on the surface of a sphere of radius corresponding to the electron projected range. This code also produces a predicted portal image which is used as a verification tool to ensure that the dose reconstruction is reliable. The dose reconstruction algorithm was compared against MC treatment planning (MCTP) predictions and against measurements. Results: The reconstructed doses and the MCTP predictions in homogeneous and heterogeneous phantoms agree within 1% for simple open fields except in the buildup region and in the penumbra where the agreement is within 9%. Comparison with film‐measured dose distribution for IMRT fields yielded agreement within 3 mm, 3 %. Conclusion: A novel dose reconstruction algorithm based on MC simulations has been developed and validated in homogeneous and heterogeneous phantoms for conventional and IMRT fields.
MO‐D‐224A‐06: Fast Monte Carlo‐Based Computation of ASi‐EPID Dose Images for IMRT Treatment Field Through Phantom
Authors: Li W , Siebers J , Kawrakow I
Published: July 2006

Purpose: During‐treatment IMRT dosimetric verification can be accomplished with exit dose portal dosimetry; however, differential beam hardening and patient scatter radiation results in inaccuracies in invariant kernel‐based calculation methods. The purpose of this study is to develop an accurate, yet efficient Monte‐Carlo (MC) based algorithm to predict during treatment dosimetric aSi‐EPID images to compare with measured images for plan delivery quality assurance. Method and Materials: To compute EPID images, the VMC++ MC algorithm is used to transport particles through the patient geometry. Particles exiting the patient are scored into 19 energy‐differential fluence‐matrices at the EPID surface. Computed EPID images are generated by summing the contributions of each fluence‐matrix convolved with MC generated mono‐energetic energy deposition kernels. Kernel‐based method validation was performed for open, MLC‐blocked, intensity test‐pattern and a prostate‐IMRT field with and without a 20 cm thick phantom by comparing with full MC computation of EPID images. Additionally, the prostate‐IMRT plan was computed through a pelvic phantom. A cone‐beam CT of the pelvic phantom was used for dose computation particle transport. Comparison metrics include image profiles and gamma‐metric evaluation. Results: For the test fields, kernel‐based methods had >95% of voxels with γ<1 for 1 %, 1mm criteria and >99.1% with a 2%, 2mm criteria with respect to the MC‐calculated fields. For the pelvic phantom, 92.6% of pixels had γ<1 for 1%, 1mm criteria. The systematic discrepancy(∼0.5%) is well below the statistical uncertainty(∼3%). Conclusion: The kernel‐based convolution method is comparable in accuracy with full MC while requiring substantially less computation time than a full MC EPID simulation. Image computation time is independent of MC statistical precision and adds <1min to the MC simulation time. Comparison of measured images with MC‐computed portal images may be a practical method to perform during‐treatment dose validation. Conflict of Interest: Supported in‐part by Varian Medical Systems.
MO‐D‐224A‐09: Validation of Synchronized Dynamic Dose Reconstruction Using Film Dosimetry
Authors: Hadley S , Litzenberg D , Tyagi N , Chetty I
Published: July 2006

Purpose: To validate a method of retrospective dose reconstruction that uses real‐time intra‐treatment patient motion data that is synchronized with MLC leaf positions during IMRT treatments. Method and Materials: IMRT fields from an IRB‐approved prostate protocol were delivered to a water‐equivalent phantom on a programmable translation stage. Kodak XV film was placed at 5 cm depth with an SSD of 95cm and marked to register it with the Monte Carlo (MC) calculation grid. Motion was synchronized with beam delivery by using the target signal to trigger motion. Film measurements were repeated for each beam while the phantom was stationary, and while moving with both idealized and clinically measured motion profiles. MLC leaf positions and fluence state for each beam were obtained from the Varian DynaLog files. MC dose accumulation was performed which incorporated the real‐time phantom motion, DynaLog files and beam state. Films were digitized and compared to the results of the MC calculations. Results: Film measurements in stationary phantoms were measured three times on two machines. The measured dose distributions were compared and showed an average difference of 0.38 +/− 1.53 cGy. The average difference between MC and film measurements of the moving phantom was 0.44 +/− 3.4 cGy and was independent of the motion profile. Measured dose patterns, for both stationary and moving phantoms, were generally well reproduced by MC dose accumulation, including tongue‐and‐groove and motion related features. Doses in moving and static phantoms were compared, for both films and simulations. The measured dose deviations due to motion were well‐characterized by the MC dose accumulation method and not significantly different when a static phantom was compared to MC calculation. Conclusion: Real‐time motion and machine data may be used to reconstruct the dose delivered to the target volume, and may serve as a basis for dynamic refinement of treatments.
MO‐D‐230C‐05: The CFS (Calibration Feedback System) Toolkit
Authors: Sorenson D
Published: July 2006

Medical imaging professionals know that properly calibrated displays are one key component to providing optimal image quality. CFS (Calibration Feedback System) provides software and hardware tools to enable this to be done properly and in a cost‐effective manner. This includes addressing calibration of both monochrome and color displays on a hands‐free basis, network monitoring and control, and access to TG18 patterns and methodology. An update of these tools will be provided.
MO‐D‐230C‐06: Totoku's Medical Display QA Solutions “i‐Model”
Authors: Hasegawa M
Published: July 2006

As PACS gains widespread use, the importance of quality assurance in medical image displays is rising and QA control methods are specified by guidelines and standards worldwide. In Japan, QA guidelines JESRA X‐0093−2005 kicked into full swing last August. The JESRA QA guidelines are based on the current AAPM‐TG18 and the expected IEC standards.

In light of such trends in the market, TOTOKU developed a QA software that covers AAPM‐TG18 and the other major standards, QA Medivisor. This software makes acceptance and constancy testing easy and accurate.

There is also a demand from medical personnel for a solution that quantitatively controls display quality. TOTOKU's i model displays satisfy such a need. The i‐model displays have a luminance sensor that is installed in front of the LCD panel. It controls the display's luminance, the key factors in determining display quality, and realizes quick and easy evaluation of the display's conformance to the DICOM GSDF. This conformance evaluation function can be used to supplement other standards and guidelines.

Furthermore, TOTOKU's performance monitoring software PM Medivisor keeps a constant watch on operating status of all displays connected to the PACS network.

This workshop focuses on the basic QA procedures and a demonstration of the DICOM GSDF conformance evaluation on the i‐model display.
MO‐E‐330A‐02: Automated Prostate Contour Drawing On Post‐Implant CT Images Based On Ultrasound Volume and Seeds Positions
Authors: Rivet‐Sabourin G , Laurendeau D , Beaulieu L
Published: July 2006

Purpose: It is difficult to locate precisely the prostate on CT images. We propose an automated contouring help method based on data acquired during intra‐operative brachytherapy procedure. The algorithm uses ultrasound volume and seeds positions to draw a preliminary contour on CT image.

Method and Materials: The data acquired during the clinical protocol are the intra‐operative ultrasound volume and the seeds positions based on the detected needle insertion, and the seed positions and the CT images thirty days post‐implant. In the first step the US volume and seed cloud are matched. For each z position of a clinical CT image, the US contour and seeds are extracted. The seeds positions are automatically detected on CT image and are used to calculate a transformation matrix to translate the seeds positions from day 0 to 30. The contours are reshaped using active contour. The reshaping process begins with the center slice and progress on both sides. The active contours are initialize with an expanded US volume. Implementation (results): There are no parameters to adjust in the first part of the algorithm. In the second part, there are six snakes parameters : continuity, curvature, convergence, gradient contraction minimum and contraction maximum. There is also a parameter controlling the resize factor of the US contours. The preliminary tests are conducted on ten clinical cases. Most of the contours were the final contour. The others needed a small physician action to correct the contours. Conclusion: This algorithm will be a useful tool to help physicians in tedious work to draw prostate contours on CT images. This automated approach presents the physician with intra‐op US volume fused to the 30 days CT exams and proposes a new set of contours based on the morphology of the seed distribution.
MO‐E‐330A‐04: Semi‐Automatic Contouring for Respiratory Gating
Authors: Wu X , Sui S , Spencer S , Fiveash J , Duan J , Popple R , Pareek P , Brezovich I
Published: July 2006

Purpose: Contouring is very labor intensive, especially in image‐guided radiotherapy involving many image sets. To expedite this task, a semiautomatic image segmentation algorithm was developed to obtain lung and tumor volumes at the end‐of‐exhalation from contours drawn on an image set taken at the end‐of‐inhalation, and vice versa. Method and Materials: The gradient vector flow (GVF) algorithm was first proposed by Xu and Prince. This snake model can dynamically conform to object shapes in response to two kinds of forces: internal force from the contour itself, and external forces from image gradients. The energy cost function composed of these two forces can be minimized based on local GVF information. Different parameters were used for elasticity and rigidity of lung and tumor tissue. A variation of the GVF method is proposed to speed up the convergence. A momentum item ξΔUt EXP(−t/T0) was added to the gradient vector calculation, in which ξ is a momentum constant and T0 is the initial annealing temperature. Results: Two CT image sets were used to verify the algorithm. The lung and tumor contours drawn at one phase were used as an initial guess for the automatic drawing in the second phase. The GVF was calculated for each slice and some important parameters, like elasticity, rigidity and mass viscosity etc were assigned specific values for the optimization. The GVF calculation converged quickly to 10−3 in less than 5 seconds for a 512 × 512 image. The ratio of overlapping areas drawn by the algorithm to those of the manual approach exceeded 98%. Conclusion: The close match between computed and manually drawn contours, as well as the short computing time indicates the feasibility of this method for clinical use. This method should also be expandable to other applications like image guided radiotherapy. More work is needed for contouring 4D image sets.
MO‐E‐330A‐05: Evaluation of Similarity Measures for Use in Intensity‐Based Registration in Radiotherapy
Authors: Wu J , Huang M , Wang Z , Samant S
Published: July 2006

Purpose: In radiotherapy, the implementation of automated patient positioning depends on optimal selection of a similarity measure. Visual inspection of a registration is insufficient for evaluating performance of a measure, since high precision registration is usually involved. A general methodology is presented for evaluation of a measure based on convergence, precision and systematic errors for 2D and 3D imaging. Method and Materials: The following common metrics were studied: mean pixelwise product (PROD), normalized correlation coefficient (NCC), partitioned intensity uniformity (PIU), mutual information (MI), normalized mutual information (NMI), entropy of the difference image (ED), gradient correlation (GC), gradient difference (GD), and pattern intensity (PI). Imaging from an anthropomorphic phantom and clinical data were used. Portal images were acquired with a video camera EPID and a flat‐panel imager. Kilovoltage digitally reconstructed radiographs (DRR) and megavoltage DRRs (MVDRR) were used for reference images. The following shifts were carried out: translations from −10 mm to +10 mm with 0.2 mm increments, and/or rotations from −10° to +10° with 0.2° increments. The effect down‐sampling and image type were also investigated. Results: The selection of a measure depended on image type and down‐sampling schedule. PROD introduced the largest systematic error. NCC, PIU, MI, NMI, and GD typically had systematic errors less than 1 mm and 1°. Down‐sampling has less effect on NCC, PIU, and GC. MI, NMI, GC, GD, and PI have sharp “peaks” around their global optima. Asymmetry in the objective function was observed in NCC, PIU, MI, NMI, and ED. Registrations using GC, GD, and PI were less sensitive to the variation of anatomical structures. Using MVDRRs instead of DRRs increased objective function smoothness. Conclusion: A general methodology was presented for evaluation and selection of a measure. Selection was application dependent, indicating necessity of a validation study, as presented here, prior to clinical use.
MO‐E‐330D‐02: 256 Slice CT: Development, Design, and Clinical Applications
Authors: Mather R , Katada K , Okumura M , Rifu T
Published: July 2006

As CT has evolved from axial to helical to multislice helical, the advanced applications have been focused on volumetric imaging. Improvements in coverage and temporal resolution have opened the doors to challenging imaging tasks such as coronary angiography. However, even with today's most advanced systems, there is still a several second time difference between the imaging of the superior and inferior portions of the heart. During this time period, small differences in heart rate and contrast medium can lead to discontinuities within the volume data as seen in some MPR images. Such artifacts can lead to inaccessibility or, worse, misdiagnosis. Toshiba has developed its 256 slice system to cover over 12 cm of anatomy in a single rotation with 0.5 mm slices to allow the complete coverage of the heart at a single, instantaneous time point. Such a system will enable seamless coverage free from banding artifacts and discontinuities. Furthermore, wide volume coverage will allow dynamic evaluation of the flow of contrast material and perfusion over an entire organ rather than in just 3–4 cm, opening the doors to new clinical applications. No new system is without technological challenges. The wide coverage of the 256 slice system requires a cone angle that is four times larger than a 64 slice system and advancements in cone beam reconstruction have been necessary to meet this need. This lecture will detail the design of Toshiba's 256 slice system and provide an overview of the system's image quality, dosimetry, and clinical applications. It will show early clinical examples of the advantages of whole organ coverage. It will explore some of the technological challenges inherent in such a system and the solutions to these challenges.

Educational Objectives

1. Understand the development and design of Toshiba's 256 slice system.

2. Understand the clinical utility of seamless, wide volume coverage.

3. Understand the technical challenges of the 256.

4. Understand the system's image quality.
MO‐E‐230A‐01: Legal Issues
Authors: Davis M
Published: July 2006

Research plays a prime role in the professional lives of many medical physicists, especially those in academic institutions. The prime goal of this research is to acquire new knowledge. Acquiring the knowledge, however, is not sufficient, in that the information must also be disseminated to the community.

The standard vehicle for dissemination of research knowledge is the peer‐reviewed journal. In fact, a medical physicist's academic advancement is often based on the number of papers that have appeared in a peer‐reviewed journal. However, publication in a journal introduces significant restriction on the ability for subsequent dissemination of the research information. Prior to publication, the producer of the information is the complete owner of the information. Researchers may disseminate the information to anyone they please in any form they please. Publication, however, places significant limitations as to how information may be disseminated because of the existence of copyright laws. Often, the individual who has generated the information has turned over ownership of the information to the publisher of the journal and no longer has complete control over how the information may be distributed to others.

Limits exist, however, on the extent that a publisher may control dissemination of the information in a journal article. In the distant past (>40 yr ago) the publisher exercised significant control over dissemination. If an author wished to provide others with copies of a paper, the author would have to purchase reprints of the article from the publisher and deliver the reprint to the recipient. In the more recent past, the author of the article, or anyone else for that matter, may photocopy the article from the journal. The ease of photocopying has established some principles of “fair use,” that is, scenarios where photocopying lies within the limitations of copyright restrictions, and other scenarios where photocopying violates copyright. For example, individuals may copy an article from a journal for their own use, but to make a large number of copies without permission for distribution to a class may violate copyright restrictions. Presently, most journal articles appear in electronic form, typically as a PDF file that can be downloaded and stored on an individual's computer. The same file can be emailed to many recipients. Because of the ease of dissemination of this information, a new paradigm for dissemination is necessary. It is necessary to balance the need to disseminate information against the need for the journal to recoup the expenses of publication and dissemination and, when appropriate, make sufficient profit to warrant remaining in business.
MO‐E‐230A‐03: Journal of Applied Clinical Medical Physics
Authors: Mills M
Published: July 2006

Publication, or dissemination of knowledge, is an essential component of scholarly activity. However, the money and profit associated with access to scholarly information is the source of both a crisis and a revolution to address that crisis. It is most common for the author to lose ownership, copyright, other property rights and control over the information. Unfortunately, these problems are not recognized as public policy issues. Public policy is important because access to print journal information has traditionally been through publicly funded libraries, and libraries are in a long, downward crisis. Universities pay scholars, usually through income derived from governmental grants, grants from non‐profit and for‐profit corporations, tuition, fund‐raising, corporate participation, etc. The majority of funding for scholarly activities comes from public sources. Scholars produce scholarly articles, and then universities pay for their libraries and scholars to have access to these scholarly articles. When scholars give up copyright to creative work, they have no say about how their research is disseminated and priced. The Journal of Applied Clinical Medical Physics is part of the open‐source publication revolution. The author retains the copyright and retains full control over the dissemination of the scholarly contribution. The key for the JACMP was to lower transaction and production costs by a factor of four below the cost of providing a subscription‐based print journal with restricted online access. The JACMP is squarely in the middle of the open‐source publication revolution as it offers scholarly articles to the worldwide medical physics community without cost.

Objectives: 1. Understand the history and importance of the open‐source publication revolution. 2. Understand the role of the JACMP in the dissemination of scholarly activity to the worldwide medical physics community.
MO‐E‐224C‐02: Quantification of Respiration‐Induced Dosimetric Impact On Liver for Abdominal Radiotherapy
Authors: Lin L , Shi C , Salter B , Fuss M , Papanikolaou N
Published: July 2006

Purpose: To quantify the dosimetric impact of respiratory motion on liver dose for IMRT abdominal radiotherapy based on 4D CT imaging Method and Materials: 4D‐CT images of a patient with klatskin tumor were acquired on a GE CT scanner during free‐breathing. Respiratory information was recorded using the Varian RPM system. The images were sorted retrospectively into ten respiratory phases. For each phase‐binned 4D data set, manual contours for liver were delineated. The Corvus inverse planning system (NOMOS Inc.) was used to generate optimized treatment plans. Two kinds of image registration methods, feature‐based iterative closest point (ICP) rigid image registration and normalized mutual information (NMI) non‐rigid image registration method, were implemented to transform each of the ten phases to a reference phase. The reference phase was the end of expiration (50%phase). A composite 4D‐DVH, which accounts for respiratory induced voxel motion, was subsequently calculated using equal weighting for each respiratory phase. A dose of 45Gy to the target was prescribed. The treatment plan was optimized to provide a minimum of 95% isodose coverage for PTV. Results: Variation of liver dose throughout each of the 10 calculated phases was within 5%. 4D effective DVH showed reduced volume coverage up to 18% for the same dose. In the high dose region of the liver DVH, the dose was less for the NMI algorithm as compared to the ICP algorithm. Conclusions: Two kinds of image registration methods have been implemented to derive 4D effective DVHs for an abdominal patient. In this study we found that respiratory‐induced motion does not produce a significant alteration of the liver DVH between the 10 phases. However, the 4D effective DVH method shows that the liver received less dose.