bluuebunny/crossref_metadata_2025 huggingface dataset:
MO‐B‐BRC‐01: Shielding Design for Linear Accelerators Using NCRP Report 151
Authors: Martin M
Published: April 2010

The application of the structural shielding design techniques and goals as outlined in NCRP Report 147: Structural Shielding Design for Medical X‐ray Imaging Facilities (November 2004) and NCRP Report 151: Structural Shielding Design and Evaluation for Megavoltage X‐ and Gamma‐Ray Radiotherapy Facilities will be the basis for this practical course. Actual facility designs will be used as the example calculations of required shielding for Linear Accelerators to be installed in modern radiation therapy facilities. Examples of methods to minimize the amount of additional shielding needed for new departments due to well planned designs will be given.

As the equipment in radiation oncology departments has evolved to linear accelerators with IMRT as state of the art modalities, the requirements for adequate radiation shielding for these modalities has become more rigorous. Architectural designs no longer depend on standard maze design rectangular rooms. Innovative layouts and utilization of multiple layers of shielding materials allow much greater flexibility in room designs. Shielding calculations for these challenging designs will be covered in this presentation.

Learning Objectives:

1. Understand the workload and occupancy factors to be used for dual energy linear accelerators with IMRT capabilities to determine required structural shielding to meet exposure limits for occupational personnel and the public.

2. Understand the effectiveness of existing and additional structural shielding materials to provide radiation protection and methods to calculate the required amounts of these materials.

3. Understand the calculation methods to be used in performing the shielding calculations for all aspects of linear accelerator installations to insure adequate shielding is provided to meet applicable state and ALARA requirements.
MO‐D‐BRD‐01: Pushing the Limits of Microwave Linear Accelerators
Authors: Tantawi S
Published: April 2010

We will review recent advances for ultra‐high gradient‐linac. We will show how the research on the basic phenomena of microwave breakdown in ultra‐high vacuum structure, led to novel geometrical designs that allow electron linac to achieve gradients in excess of 140 MV/m. Also, with the usage of copper alloys, one would hope to push this gradient to 180 MV/m. these advances can be applied to proton linacs. We will present suggested designs for future proton linacs, which would push the gradient to more than 70 MV/m. These will operate at high frequency in the X/Ku band. With this technology one hopes to design compact proton therapy machines at energies of ∼ 250 MeV, with fine control of energy. The compactness of the linac might allow the whole system to be installed on a single gantry.
MO‐D‐BRD‐03: Laser‐Driven Targetry: The Road to Clinical Applications
Authors: Ma C
Published: April 2010

Purpose: Significant efforts have been made through federal, industrial and institutional funding to develop cost‐effective alternatives to conventional accelerator‐based particle therapy. This presentation reviews the development of laser‐accelerated particle beams as an alternative to conventional accelerators for particle therapy. Method and Materials: Many institutions and research groups have focused on their research on the applications of laser‐accelerated proton and ion beams for medical applications, in particular for radiotherapy treatments. These include extensive investigations of optimal laser parameters and target designs to achieve therapeutic particle energies, compact particle selection and beam collimation designs for novel compact particle therapy systems, dose calculation and treatment optimization for laser‐accelerated proton beams, and system and shielding designs for clinical prototype machines. Fox Chase Cancer Center has established a laser‐ion acceleration facility that consists of a commercial 150 TW laser, custom‐made laser‐pulse compression and target chambers, particle selection and beam collimating devices, dosimetry monitoring systems and shielding constructions. Initial laser‐proton acceleration experiments were performed with thin aluminum and plastic foils as target materials. Particle‐in‐cell (PIC) simulations were carried out to investigate the optimal laser parameters and target configurations to facilitate laser‐proton acceleration and dosimetric studies. Results: The maximum proton energy achieved by laser acceleration was 58 MeV. Our initial testing with a 1018 W/cm2 laser intensity (at 20 TW) produced up to 4 MeV protons with a broad energy spectrum, which confirmed the scalability of laser intensity and maximum proton energy. A compact shielding designed was investigated using Monte Carlo simulations that allows for the installation of the particle therapy head on a small rotating gantry. Conclusion: Laser‐accelerated proton and ion beams have a great potential to replace conventional radiotherapy systems due to its compact design and cost‐effectiveness. Many technical and engineering issues must be solved before a clinical prototype can be built for radiotherapy applications.
MO‐D‐BRD‐04: Innovations in Hadron Beam Generation with Plasmas
Authors: Capelli M
Published: April 2010

Proton radiotherapy for cancer is growing in the US and around the world. This growth is due to the physical advantages of the improved ability to deposit most of the radiation dose in the tumor, as opposed to x‐rays where most of the dose is deposited in normal tissues. In the US there are currently five proton therapy centers treating patients and over 2,300 x‐ray based linear accelerator facilities. Limiting the widespread application of proton radiotherapy to the general cancer patient community is the capital, building and operating costs associated with proton radiotherapy that exceed $ 100 million per site, a substantial cost differential with x‐ray based facilities. A compelling approach is to combine the physical advantages of proton therapy into a smaller, cheaper, gantry mountable system that can be widely disseminated. This requires a radical breakthrough in accelerator technology, however, as the size and mass of such an accelerator would have to be at least an order of magnitude less than those of conventional cyclotrons and synchrotrons. The Plasma Physics Laboratory at Stanford has developed a novel particle accelerator that is based on a newly‐understood second mode of operation in co‐axial plasma accelerators. By processing a plasma instead of a pure ion gas, the proposed accelerator is fundamentally different from electrostatic accelerators, resulting in two important advantages. First, a plasma gas contains electrons and positive ions, making it macroscopically neutral. As a result, it can tolerate high ion densities in a very compact device. Second, a plasma can conduct very high currents and self‐induce strong magnetic fields. This can be used to accelerate the plasma electromagnetically via the Lorentz force. The particle energy then becomes a function of the current to mass flow ratio rather than of the applied voltage. Eliminating the need for applying high voltages enables the generation of bursts of extremely energetic particles from a comparatively simple and inexpensive device. The recent identification and stabilization of a second mode of operation in coaxial plasma accelerators makes the advantages of plasma‐based approaches accessible to proton radiotherapy. The distinct features of the proposed plasma‐based accelerator may also result in attractive advantages when compared to alternative compact accelerator concepts that are currently under development.

This lecture will provide an overview of the differences between plasma and pure ion acceleration, as well as some of the limitations that have historically limited plasma accelerators to low beam energy applications. It will then summarize the advantages of operating in the second mode and describe the challenges that have to be overcome to scale and develop the existing proof of concept prototype into a viable therapy machine.
MO‐D‐303A‐01: Improving MRI Physics for Radiology Residents: Year One
Authors: Allison J , Yanasak N
Published: April 2010

Introduction: Educational concepts in various presentations by Perry Sprawls and in the AAPM 2008 Workshop (“Becoming A Better Teacher Of Medical Physics”) suggested that our MRI physics course was geared to the lowest levels of learning, according to Bloom's Taxonomy. We elected to increase the number of higher‐level learning activities in the course in an effort to improve understanding and increase retention. The Problem: Our traditional course was comprised mainly of PowerPoint lectures. One two‐hour lab was held in the evening. Most course time was spent at the “remembering” level, with higher level learning limited to a few questions in class, the lab and an exam. Residents did little outside of class. Engaging the residents in dialog was difficult. The physical layout of the classroom stifled discussion. The mindset of residents was to gather essential MRI facts to memorize before the fall radiology physics exam. Our Solution: We revamped the course to incorporate more higher‐level learning activities. A typical class included: a) out‐of‐class assignments b) a quiz based on the assignments to stimulate thought c) a relevant “artifact of the day” to provoke group discussion d) and demonstrations and discussions using a variety of media. Class was moved to a room inside an MRI suite for access to MRI hardware/software and to give the residents exposure to the MRI environment. Class met around a small table to facilitate discussion. We expanded to four lab sessions. Clinical relevance of MRI physics topics was stressed. Evaluation: We believe our classroom activities and labs inspired more higher‐level thinking, engaging residents to “figure out” (apply, analyze, and evaluate) solutions to clinically relevant problems. A survey of the resident's evaluation of the course will be presented.
MO‐D‐303A‐03: Peer Instruction in the Teaching of An Introductory Medical Physics Course
Authors: Starkschall G
Published: April 2010

Purpose: The purpose of the present work is to describe how the peer instruction teaching methodology (E Mazur. Peer Instruction: A User's Manual. Prentice Hall, Upper Saddle River NJ 1997) was incorporated into the teaching of an introductory medical physics course. Methods and Materials: Peer instruction focuses on concepts, rather than on information or on problem solving. The technique uses a series of “ConcepTest” questions to present a set of concepts in each classroom session. When presented with a ConcepTest question, students propose answers to the question, discuss their answers among each other in small groups, and finally discuss their answers with the entire class. One principle behind peer instruction is that students who more recently achieved understanding of a concept are in a better position to overcome the barriers to understanding the concept than the faculty member, who has understood the concept for a long time. Prior to each class, students are expected to download and listen to an AVI file consisting of a recording of the class lecture. Following class, students are assigned problems based on the class material, which are discussed in separate problem sessions. Results: In the discussion of the ConcepTest questions, students who did not understand the concept being tested were unable to provide a convincing argument justifying their selection, whereas students understanding the concept were able to convince their colleagues that their selection was correct. After discussion, when retested on the ConcepTest question, almost all students were able to get the correct answer. Conclusions: Students involved in peer instruction took an active role in class participation. Student feedback regarding this mode of instruction was very positive.
MO‐D‐304A‐06: Filtered Region‐Of‐Interest Cone‐Beam CT From Rotational Angiography for Image‐Guided Interventions: Evaluation of Dose Reduction and Image Quality
Authors: Schafer S , Noel P , Walczak A , Kuhls‐Gilcrist A , Hoffmann K
Published: April 2010

Purpose: Rotational angiography is widely used to generate 3D data for image‐guided interventions. In standard practice, full‐field acquisitions are obtained, though the surgeon's region of interest (ROI) is considerably smaller, e.g. for stent placement. To reduce dose to the patient while delivering the desired image quality for the intervention, we developed a filtered ROI (FROI) method for reducing the beam intensity outside the ROI by using an x‐ray attenuating filter. We evaluated dose reduction and image quality resulting from this method. Method and Materials: A gadolinium‐based filter with a central circular opening is mounted on the aperture of the x‐ray tube of a rotational angiography system effectively splitting the beam into a high‐intensity ROI and a low‐intensity filtered region. Artifact‐free reconstruction is achieved by equalizing the filtered‐region intensities to those in the ROI using a calibration image. Dose reduction in FROI‐CT is assessed theoretically through the dose area product and experimentally using dose measurements. Image quality in unfiltered and equalized filtered images is assessed using the scatter fraction and the contrast‐to‐noise ratio (CNR) in both projection images and reconstructed volumes. Results: Experimental dose measurements for a filter thickness of 1.29 mm and an ROI size of 20% FOV yield a 60% dose reduction, similar to theoretical calculations. Scatter fractions inside the ROI are reduced by 35% compared to conventional images. CNR in projection images in the ROI is improved from 450:1 (conventional RA) to 533:1 (FROI) and is similar in the filtered region. CNR in the reconstructed ROI is 65:1, similar to conventional RA, and lower in the filtered region (45:1 filtered, 75:1 conventional). Conclusion: The results support the potential dose‐reduction capabilities and utility of ROI imaging in rotational angiography while supplying the desired image quality inside the (reconstructed) ROI.
MO‐D‐210A‐01: Photon Counting Detectors for Mammography
Authors: Danielsson M
Published: April 2010

Mammography is currently one of the most common x‐ray imaging examinations. More than 100 million women worldwide are screened every year and early detection of breast cancer through mammography has proven to be a key to significantly reduced mortality. The requirement on spatial resolution as well as contrast resolution is very high in order to detect and diagnose the cancer. Moreover, because of the large number of women going through this procedure and the fact that more than 99 % are healthy, it also becomes very important to minimize the radiation dose.

Photon counting may be one way to meet the demands and mammography is the first modality in x‐ray imaging to implement photon counting detectors. FDA approval is still pending but they are currently in routine clinical use in more than 15 countries. The photon counting enables a discrimination of all electronic noise and a more optimum use of the information in each x‐ray. The absence of electronic noise is particularly important in low dose applications, in for example tomosynthesis a number of exposures from different angles are required and since the dose in each projection is just a fraction of the total dose for a mammogram the sensitivity to electronic noise will increase.

Using the spectral information for each x‐ray it is in principle possible to deduce the elemental composition of an object in the breast. This could for example be used to enhance microcalcifications relative to soft tissue and differentiate water from fat in cysts. Recently contrast mammography has attracted significant attention. In this application Iodine is used as a contrast media to visualize the vascular structure. As in breast MRI the cancer stand out because of the leaky vessels resulting from its angiogenesis. A photon counting detector gives a unique opportunity to image the Iodine through spectral imaging by adjusting one of the thresholds to its K‐edge.

Challenges for photon counting in mammography are high rates of x‐rays, both to generate the required flux at the source and to handle the rates at the detector without pile‐up. Even more difficult to handle are the charge sharing between detector pixels which, if not corrected for, will compromise the energy information.

The current status of photon counting detectors in mammography will be described together with strategies to overcome the pit‐falls. Also future possibilities with spectral imaging in mammography will be investigated and examples from ongoing clinical trials will be given.

Learning Objectives:

1. Status of photon counting detectors in mammography

2. Pit‐falls and opportunities with photon counting detectors for mammography

3. Future applications based on spectral detectors for mammography
MO‐D‐210A‐03: Energy‐Sensitive, Photon‐Counting Computed Tomography: Opportunities and Technological Challenges
Authors: Roessl E , Brendel B , Martens G , Proksa R , Schmidt F , Thran A , Schlomka J
Published: April 2010

Recent advances in the development of direct‐conversion, energy‐sensitive x‐ray detectors stimulate research in the domain of pre‐clinical and clinical photon‐counting x‐ray computed tomography (CT). The ability to quantify the energy of individual X‐ray photons allows for novel approaches to improve the soft tissue differentiation, material decomposition and labeling techniques, the suppression of beam‐hardening artifacts as well as the potential reduction of radiation dose. Moreover, spectral data acquisition enables the selective and quantitative imaging of certain contrast media on top of the conventional anatomy, by tuning an energy threshold in the detector system to the K‐edge discontinuity of the contrast generating element in the agent.

The present lecture will provide an overview of both, the opportunities and the technological challenges arising in the context of clinical, energy‐resolved, photon‐counting CT. Some examples of potential future applications will be given together with the most challenging technical difficulties encountered in the use of photon counting detectors in CT. The problem of counting photons at the high flux conditions of clinical CT will be discussed as well as the degradation of energy resolution by effects like pulse‐pileup or charge sharing.

All authors are employees of Philips Research.

Learning Objectives:

1. To understand the physical basics of photon counting detectors and the implications on their use in x‐ray computed tomography

2. To learn about a possible future application of energy‐sensitive CT in connection with the identification and quantification of contrast‐agents by means of the K‐edge discontinuity in the attenuation.

3. To obtain an overview of the technological challenges to be overcome in order to realize photon‐counting CT in clinical practice.
MO‐D‐213A‐02: Practical Aspects of Nuclear Medicine Accreditation
Authors: Harkness B
Published: April 2010

This lecture will present a review of the specific aspects and requirements of the nuclear medicine accreditation process. Particular emphasis will be placed on the process for SPECT cameras. The specifics of the phantoms, acquisition procedures, and the review of submitted data will be presented. Examples will be given for specific cameras. Upon completion of the course participants will be able to describe:

1. The characteristics of the required ACR phantom for SPECT.

2. The acquisition procedures used for accreditation in nuclear medicine.

3. The image characteristics evaluated by the ACR phantom reviewers.
MO‐E‐211A‐01: Professional Doctor of Medical Physics
Authors: Serago C , Coffey C , Herman M , Gerbi B , Klein E , Hevezi J
Published: April 2010

There has been and continues to be a dynamic dialogue concerning the establishment of a professional doctorate in medical physics (DMP). The AAPM created a working group in the spring of 2008 tasked with assessing the impact of a DMP degree on the education, research, and clinical practice of medical physics. This working group submitted their report to the AAPM Board of Directors the summer of 2008 outlining many of the potential ramifications the DMP may have on the profession of medical physics. Among the implications to be considered if the DMP degree becomes a reality are: impact on existing Masters medical physics programs; impact on Ph.D. medical physics programs; impact on post‐doctoral programs; impact on the quality of patient care; impact on medical physics residency programs; and the impact on the professional standing of medical physics. Since 2008 some academic institutions have or are in the process of creating DMP graduate programs. This potential new pathway toward a career in medical physics will also impact credentialing organizations such as CAMPEP (Commission of Accreditation of Medical Physics Education Programs) and the ABR (American Board of Radiology).
MO‐EE‐A1‐01: A QA Procedure for MLC Leaf Position and Dynalog File Accuracy Using the EPID
Authors: Emam I , Fan J , Xu Q , Jin L , Ma C
Published: April 2010

Purpose: A main concern about the IMRT dose validation tool using Monte Carlo (MC) simulation and R&V system/Dynalog file is the potential inconsistency between the actual leaf‐end positions and those recorded by the Dynalog file. The present study investigates an accurate, fast and independent method to validate the accuracy of the dynalog files using aSi‐EPID images. Materials and Methods: A computer program was developed to detect the MLC segmented field edges in EPID images (1024×768 pixels, pixel size: 0.392mm). Standard reference MLC segmented fields were designed and leaf‐end positions were measured accurately. EPID images for these reference MLC fields were recorded and the leaf‐end positions were calculated as the locations where the image intensity is 50% of the maximum. Small corrections were made to minimize the effect of scattered photons (background). Daily EPID images of the same MLC segmented fields were compared to the original images and to check the accuracy of the Dynalog files. The patient‐specific Dynalog files were used for MC based patient‐specific treatment verification. Results: Both the MLC and EPID were calibrated to produce accurate and consistent leaf‐end positions. The results showed that the EPID‐extracted leaf‐end positions were within ±0.167mm of their actual positions, while the average RMS leaf‐end deviation was 1.73mm. Differences between daily EPID and Dynalog leaf‐end positions were established and to be monitored on the long term. Random small leaf position variations have negligible effect on the patient dose distribution but a 1mm systematic leaf‐end‐position error could result in a 3% change in the delivered dose. Conclusion: A daily QA tool is developed to check the accuracy of the Dynalog file and MLC leaf‐end positions as part of the comprehensive IMRT QA procedure. This ensures the accuracy of the MC based patient‐specific IMRT dose verification using the information recorded in the R&V system/Dynalog files.
MO‐EE‐A1‐06: Performance of MPC‐Based Adaptive Radiotherapy Optimization
Authors: Jee K , Kashani R , McShan D , Fraass B
Published: April 2010

Purpose: An adaptive re‐planning framework was used to account for tissue deformation during RT treatment courses. The framework is based on a multivariate control concept called model predictive control (MPC). A variety of control rules and optimization schemes were investigated using a prioritization‐based optimization method. Performance of the MPC control was evaluated with conventional evaluation metrics such as DVH, coverage, and homogeneity as well as model‐based plan evaluation metrics. Method and Materials: The Head/Neck IMRT treatment process was simulated using mid‐course CT scans, tracking treatment doses to tissues at the voxel level. Off‐line adaptation was performed with the changing patient model, updating the state of the process along with the dose‐to‐date information. Constrained optimizations were performed for re‐planning as well as for pre‐treatment planning. Multivariate control schemes including maximum constraint violation were utilized for re‐planning. Results: With the adaptation of the treatment plan to the patient‐specific anatomical changes, the predicted outputs could be efficiently controlled improving the robustness to those changes. Although the results show that the general trend in the predicted outputs follow the tissue volume changes, the clinical decision to re‐plan should be made by assessing the total predicted treatment output expectations. For cases investigated, a limited number (3∼4) of re‐plans were sufficient to control high priority outputs while the use of a tighter tolerance increased the number of re‐plans. Re‐plans were triggered mostly by the target coverage criteria. The studied course simulations indicate that significant changes are shown early in treatment. Therefore, frequent updates of the patient models may be necessary and critical to plan adaptation. Conclusion: The proposed multivariate control framework provided an intuitive method of articulating clinicians' decisions and priorities for re‐planning. In addition, the use of prioritization in re‐optimization may allow more efficient re‐planning which requires fewer planning resources.

Supported in part by CA‐P01‐CA59827
MO‐EE‐A2‐06: Measurements and Comparison of Out‐Of‐Field Organ Doses From Varian Clinac IMRT Plans Using the Atom Phantom
Authors: Han B , Dorgu A , Pavord D , Bednarz B , Xu X
Published: April 2010

Purpose: To quantify and analyze the unwanted out‐of‐field organ doses during different IMRT prostate treatments and make a systematical comparison of previously reported organ doses. Method and Materials: The measurement involved an ATOM Phantom, thermoluminescent dosimeters (TLD) and a Varian 2100C Clinac. The ATOM phantom was scanned using CT machine to create virtual images for treatment planning. We developed two 6‐MV prostate IMRT plans of 5‐ and 9‐field with the same dose prescriptions, constraints to organs‐at‐risk, and similar in‐field dose distributions. A total of 162 TLDs were placed in the predefined holes to measure the average organ doses of 7 different organs. The results of the two treatment plans were compared to estimate the difference of the out‐of‐field doses. Results: The measurements showed that dose decreases as the distances from the measurement point to the radiation field increases for all treatment plans. The average out‐of‐field organ doses ranged from a maximum of 30.92 cGy to the small intestines to a minimum of 4.40 cGy to the thyroid. The 9‐field IMRT plan resulted in an absorbed dose up to 30% higher than the 5‐field plan which is mainly due to the increased accumulative scatter and lower MU efficiency of the 9‐field IMRT plan. The results were also compared with other studies and the discrepancies were mainly due to the different distances from organs to treatment fields. Conclusion: A method to use TLD and the ATOM physical phantom to measure out‐of‐field organ doses for IMRT has been presented. The measurement results demonstrated that the 9‐field IMRT treatment delivered higher photon doses than the 5‐field IMRT treatment to the out‐of‐field organs. Findings from this study involving the prostate treatments express the need to implement the out‐of‐field dose estimation to the treatment planning in order to minimize the secondary cancer and other radiation risk.
MO‐EE‐A4‐01: Stability of T1 Relaxation Time and DCE‐MRI Measures
Authors: Bosca R , Jackson E
Published: April 2010

Purpose: With the increased interest in using MR as a means of assessing therapy response, it is important to assess longitudinal systematic variations. In this study, T1 and contrast‐to‐noise ratio (CNR) variations during a dynamic contrast enhanced (DCE) acquisition were assessed on three scanners at three time points. Method and Materials: CNR and T1 measures were calculated from images of a modified Eurospin TO‐5 phantom (DiagnosticSonar, Scotland) consisting of 19 compartments with T1 values ranging from 208–1630 ms. Three GE Excite HD scanners were evaluated. Multiple TI (N=10) inversion recovery (IR), multiple flip angle (N=7) fast spoiled gradient echo (FSPGR), and FSPGR DCE data were acquired at three time points (baseline, 1 hr, 1 week). T1 measurements were obtained using both IR and FSPGR data. CNR measurements were computed using the longest T1 sample as a reference. Correlation and Bland‐Altman repeatability (same scanner) and agreement (different scanners) measures were computed. Results: Correlations of the IR‐ and FSPGR‐based T1 measures were significant for all three scanners (R2>0.996; slopes ranging from 0.84–1.11). Short‐term (1 hr) and one‐week FSPGR repeatability results ranged from 7.0–9.1ms and 10.0–17.4 ms, respectively, with limits of agreement ranging from −15.5–15.1 ms and −21.5–31.7 ms, respectively. The FSPGR BA analyses indicated a linear increase in T1 differences with increasing T1 and the maximum difference was 343 ms. The IR based measurements did not demonstrate such a linear trend and differences were less than 40 ms. Short‐term (1 hr) IR/FSPGR repeatability and limits of agreement results ranged from 91.3–185.1 ms and −330.7–39.5 ms, respectively. Intra‐DCE scan CNR variations ranged from 0.3–0.6% across scanners and time points. Conclusion: The clinical scanners evaluated demonstrate good repeatability of T1 and CNR measurements on a given scanner with larger variations seen between different scanners, even from the same vendor.
MO‐EE‐A4‐03: Evaluation of a New More Efficient and More Objective MRS Tool for Brain Gliomas
Authors: Wu D , Doblas S , Modi J , Towner R
Published: April 2010

Purpose: To introduce a novel two‐point initialization and semiautomated objective tool for MR brain spectroscopy. This method will improve the efficiency speed and reduce user‐bias in evaluation in‐vivo spectra assessed over artifacts (simulated) that arise from shimming, electronic noise, field inhomogeneity, coil sensitivities, relaxation which can cause variation in baseline drift or system noise. Method and Materials: Ten cases of C‐6 induced rodent Glioma models/controls were analyzed from MRS data acquired on a Bruker Biospin 7T scanner. The new two point method only requires the user/technologist to specify ‘start’ ‐ ‘end’ PPMs. First moment calculation is to used estimate the global standard deviation that initializes a Marquart‐Levenberg nonlinear optimization method. Three equations were assessed: I) Gaussian‐only fit, II) equal weighted Gaussian and Lorentzian Mixture, and III) free ratio between Gaussian and Lorentzian mixtures. We tested the algorithm in four metabolic regimes (Creatine, Choline, NAA, and Lipid/Lactate). Results: General Linearized Mixed Models were used to assess the method. There were significant differences (F=1817; df = (3, 47e3), p<.0001) between the algorithm types (I‐III) across disease model (c6 vs. control). When the pure Gaussian was applied the results tended to over estimate area (t= 2.73; df=450.0, p<0.001). The 50% mixture of Gaussian‐Lorentzian (t= −2.28; df 428.1, p<0.001) was found to underestimate of the true area. No difference was found on the freely varying (model III) for two point fit. Conclusion: The 2‐point method was shown to be equivalent or better than the 3 pt method for the initial spectra bracketing step. This provides advantages since the two point method requires less judgment (more objective) and is faster to perform. Additionally, we have demonstrated that the simple fitting of a Gaussian function may not be sufficient and Lorentzian terms may be required. Such standards are important for efficient glioma MRS evaluation.
MO‐EE‐A4‐06: Using Total‐Variation Regularization for Deformable Registration of the Shear Movement of the Lungs
Authors: Xie Y , Zhu L , Xing L
Published: April 2010

Purpose: To report a deformable image registration strategy using total‐variation regularization with explicit inclusion of the differential motions of thoracic structures. Methods and Materials: Accurate modeling of thoracic organ motions remains illusive because of the lack of an effective mechanism to deal with the discontinuous movements of the involved anatomic structures. In this work, we propose an efficient deformable registration algorithm to deal with the lung motion. Instead of directly applying the least square optimization, we include a total‐variation regularization to account for the motion discontinuity close to the contact surface between lungs and chest wall. The term of total variation calculates the sum of absolute values of the derivatives, and the penalties drive the derivatives toward zeros and force the optimized displacement vector close to be piece‐wise continuity. Results: The proposed approach is evaluated using a digital phantom case and two lung cancer patients. For the phantom case, a comparison with the Levenberg‐Marquardt least square optimization showed that the registration accuracy was markedly improved. On average, the registration error of 15 representative points in the lung (against the known ground truth) was reduced from 6.0±4.1 mm to 1.6±0.7 mm when the new method was used. Similar level of improvement was achieved for the clinical cases. Conclusions: The deformable approach using total‐variation provides a natural and logical solution to model the discontinuous organ motions and greatly improves the accuracy and robustness of deformable registration.
MO‐E‐BRC‐01: Applying Single Molecule Real Time DNA Sequencing
Authors: Turner S
Published: April 2010

SMRT (single molecule real time) DNA sequencing is a novel, high throughput method for sequencing DNA. It harnesses the intrinsic power of DNA polymerase enzymes as sequencing engines by eavesdropping on template‐directed synthesis in real‐time. Two critical technology components enable this process: The first is phospholinked nucleotides where, in contrast to other sequencing approaches, the fluorescent label is attached to the terminal phosphate rather than the base. The enzyme cleaves away the fluorophore as part of the incorporation process, leaving behind completely natural double‐stranded DNA. The second critical component is zero‐mode waveguide (ZMW) observation confinement technology that allows single‐molecule detection at concentrations of labeled analogs relevant to the enzyme. Through the combination of these innovations, our technology allows the speed, processivity, efficiency and fidelity of the enzyme to be exploited. We show application of this technology to shotgun sequencing of human and bacterial DNA resulting in high consensus accuracy and unprecedented readlength. Because with Phospholink nucleotides the polymerase reverts completely to the initial state after each base sequenced the accuracy profile as a function of position within a read is flat. We will present a novel sample prep concept based on DNA hairpin ligation to double‐stranded DNA that facilitates whole genome shotgun sequencing directly from genomic DNA with near‐Poisson limited coverage uniformity and practically no GC bias. This sample prep will be demonstrated to enable consensus sequencing based on data extracted from just one molecule, allowing high accuracy sequencing at the molecular limit and without amplification.

Objectives

• The attendee should be able to distinguish 2 technologies enabling SMRT DNA sequencing and characteristics of each.

• They should be able to define what SMRT DNA sequencing is and how it differs from other sequencing technologies.

• Attendees should be able to explain how high accuracy without amplification is achieved through sample prep — ie, what methods

• Attendees will have learned about a unique sample prep process involving DNA hairpin ligation and double‐stranded DNA.
MO‐E‐BRC‐02: Challenges for Next‐Generation Accelerators
Authors: Lykken J
Published: April 2010

Particle accelerators, once the exclusive playthings of high‐energy physicists, have become an essential technology for modern medicine, materials science, and molecular biology. The world's 7000 operating medical linacs have already enabled treatment of 30,000,000 patients, and new developments such as advanced proton therapies imply a growing demand for accelerators in the decades ahead.

To serve the broadest possible patient population worldwide, medical accelerators need to become smaller, cheaper, and easier to operate. At first glance these needs appear orthogonal to those of particle physics, where the push has always been for larger more complex accelerators capable of reaching ever‐higher energies. However particle physicists have realized for some time that the 27 kilometer Large Hadron Collider, beginning operation this year, represents the last hurrah of conventional accelerator technology. The future lies with fundamentally new approaches that promise much stronger accelerating gradients. The same breakthroughs needed to make large high‐energy accelerators affordable will also make medical linacs smaller and cheaper.

Fermilab and other national laboratories have taken the lead in developing new accelerator technologies with revolutionary potential. These include superconducting accelerating cavities, plasma wakefields, and laser acceleration. This lecture will provide a non‐technical overview of the prospects for next‐generation accelerators.

Learning Objectives:

1. Understand the increasing importance of particle accelerators across many disciplines.

2. Understand the needs driving research into new accelerator technologies.

3. Gain a working idea of the most promising avenues for next‐generation accelerators.
MO‐FF‐A1‐03: Investigation of Discrepancy in Reports On GafChromic EBT Energy Dependence
Authors: Rink A , Ruschin M , Jaffray D , Lindsay P
Published: April 2010

Purpose: Radiochromic films, such as GafChromic EBT, provide a convenient and versatile dosimeter, and are particularly useful for small field dosimetry. Due to previous reports showing energy independence, GafChromic EBT films were implemented as dosimeters across a wide range of energies. However, in recent years, reports showing energy dependence have been presented, contradicting previously published data. This discrepancy was investigated by comparing two batches of film manufactured 4 years ago to two recently manufactured batches. Method and Materials: Small pieces of film were irradiated to 100 cGy using a 6 MV and a 105 kVp beams. A 30 cm × 30 cm × 4.5 cm phantom equipped with optical fibers was used, with appropriate amount of Solid Water as backscatter. Net optical density was measured by two completely independent methods: a 10 nm range at main absorbance peak was used for real‐time measurements, and a red channel of an Epson 1680 flatbed scanner was used for the measurements performed 24 hours after irradiation. Results: The ratios of optical density (105 kVp to 6 MV) were markedly different between the old and new batches of film, both for real‐time and scanner measurements. While the ratio of the older films demonstrated energy independent within 10%, as previously reported, the newer films show approximately a 25% drop in response when orthovoltage energies were used. Conclusion: A statistically significant difference in energy dependence exists between older and newer GafChromic EBT films, confirming both the publications demonstrating energy independence and those showing a decrease in sensitivity at low energies. Chemical analysis is underway to investigate the potential causes of the observed results.
MO‐FF‐A2‐02: Respiration Induced Heart Motion and Indications of Gated Delivery for Left‐Sided Breast Irradiation
Authors: Qi X , Wang K , Hu B , Lopez F , Tai A , White J , Li X
Published: April 2010

Purpose: To study dosimetric gain of respiratory gating to account for heart motion during left‐sided breast irradiation and to determine indications for gating treatment during treatment planning. Methods and materials: The 4DCT data acquired with free breathing for 13 (out of 68) left‐sided breast cancer patients, who underwent whole breast irradiation with or without regional nodal irradiation, were analyzed retrospectively. Contours of the targets, lung and heart from the planning CT, selected to be the CT at 20% phase, were populated to 0‐ and 50%‐phase CT using deformable registration. The 3D dose distributions were reconstructed in these three phases (0, 20 and 50%). The heart dislocation between the breathing phases was measured in three selected transverse CT slices for the three phases by the changes of DLAD [the distance from left ascending aorta (LAD) to a fixed line drawn on each slice], and maximal heart depth (MDH, the distance of the forefront of the heart to the line). These distances were correlated with the changes of mean heart dose (MHD) and V25.2 for heart between the breathing phases. Results: Significant respiration induced heart displacement was seen, which resulted in substantial variations in dose delivered to the heart. In particular, the heart appeared to move towards to the chest wall during respiration, DLAD changed up to 9 mm, and MDH changed 10.4 mm, 11.0 mm and 10.7mm, respectively, on the three transverse CT slices from superior to inferior. The MHD and V25.2 varied up to 38% and 39%, respectively. These variations were reduced substantially with gating. Conclusion: The respiration induced heart displacement can result in significant variation in heart dose during left‐sided breast irradiation. A large variation in the distances: MDH and/or DLAD, can be used as an indicator to trigger respiratory management, such as gating prior to the treatment delivery.
MO‐FF‐A2‐03: Is Average CT a Good Estimate of Mid‐Ventilation Position of Surrounding Normal Structures for Proton Therapy Treatment Planning of Lung Tumors?
Authors: Matney J , Vedam S , Dong L , Amos R , Zhu X , Balter P , Mohan R
Published: April 2010

Purpose: Mid‐ventilation CT has been used as the reference data set for proton therapy treatment planning. Our aim was to determine if average CT provides an accurate representation of mid‐ventilation position of surrounding normal structures for proton therapy of lung tumors. Methods and Materials: 4DCT scans were acquired for 9 patients with lung tumors for the purpose of proton therapy treatment planning. Maximum (MIP) and average (AVGIP) intensity projection CT datasets were then derived from the 4DCT. Total lung volumes and diaphragm apex positions were delineated on each of the 10 phases of the 4D CT and the average CT. A representative external marker position for each phase of the 4D CT was also determined. Correlations between diaphragm apex position, lung volumes and external marker position were studied. Lung volumes obtained from average CT were compared to those obtained from a mid‐ventilation (30% phase of the 4D CT) CT data set. Results: Eight of nine patients exhibited a correlation greater than 0.9 between the lung volume and external respiratory motion. One patient with an erratic external respiratory trace had a correlation of 0.63. The correlation between lung volume and internal respiratory (diaphragm) motion was greater than 0.85 for all patients observed. Total lung volume determined from the mid‐ventilation (30% phase) CT differed from the average CT by > 5% in only 2 out of 9 cases (max difference = 13.5%). Conclusions: Total lung volume is strongly correlated to both external and internal (diaphragm) respiratory motion. The average CT provides a suitable representation of mid‐ventilation position of surrounding normal structures for thoracic proton therapy treatment planning.
MO‐FF‐A3‐02: In‐Vivo Correspondence Validation of a Deformable Image Registration Method
Authors: Lian J , Foskey M , Wang S , Shen D , Chang S
Published: April 2010

Purpose: During a course of radiation therapy for the prostate, organs such as the bladder and rectum may change shape significantly from day to day, causing the delivered dose to differ from that planned. Deformable image registration has been used to overlap structures with different shape. In this project, we propose a method to validate the correspondence accuracy of a deformable registration algorithm using images of previously treated prostate patients. Method and Materials: The planning and one daily treatment CT images for each of five patients with three Calypso transponders implanted in their prostate were retrospectively selected for the study. Two CT volumes of each patient were pre‐processed to mask the fiducials. A fluid‐based image registration method was used to register images. The displacement fields obtained were applied on the original images with fiducials. The overlap of prostate volumes between the registered images was evaluated by the coincidence index (CI). The centroid positions of each transponder were calculated. The distance between the corresponding transponders was used to quantify the accuracy of correspondence of image registration. Results: The fluid deformable image registration produced satisfactory results of the overlap of the prostate volumes. The mean CI is 95.3%, with 91.5% as minimum and 98.7% as maximum. The average distance between the centroid of all pairs of transponders is 0.35 mm. The displacement is related to the quality of image registration. For image registration with CI 98.7%, all displacement of three pairs of transponders is within 0.22 mm. When less overlap is achieved, CI 91.5%, one pair of transponder is 0.78 mm apart. Conclusion: We have used real patient data to validate the correspondence of the fluid deformable image registration method. For the prostate, it has maintained sub‐millimeter mapping accuracy, which is dependent on image registration quality.
MO‐FF‐A3‐03: Quantitative Assessment of Automatic Anatomy Segmentation of 4D CT Images Using a Deformable Image Registration Algorithm
Authors: Dogan N , Sleeman W , Yan C , Fatyga M , Wu J , Christensen G , Hugo G , Weiss E , Williamson J
Published: April 2010

Purpose: Quantify the accuracy of Small Deformation Inverse Consistent Linear Elastic (SICLE) deformable image registration to auto‐segment contours on 4D thoracic CT images. Method and Materials: A process of automatic contouring based on SICLE deformable image registration of respiratory CT phases from 4DCT scans was integrated into our image‐guided‐radiotherapy‐computing‐framework. The gross tumor volumes (GTVs), right and left lungs, cord and esophagus were manually‐drawn by the same physician for all ten respiratory phases. Registrations were performed using three intensity windows: 0–900 (lung only), 900–1300 (remaining tissue excluding lung) and 0–1300 (whole image). For each respiratory phase, the differences between the manually‐drawn and deformably‐mapped contours for each phase were quantified using fractional volume differences (FVDiff), differences in center of mass coordinates (COMdiff) and volume overlap index (VOI) and 3D maps of perpendicular distance between manually‐drawn and deformably‐mapped boundaries. The results were also compared against the previously‐implemented viscous fluid‐based registration. Results: The VOI for GTV and heart varied from 0.85 to 0.90, from 0.9 to 0.97, respectively. As expected, the smallest FVDiff were found be for the lungs (<0.027). The SICLE (0–900) and viscous fluid methods yielded similar GTV COM in superior‐inferior direction. COMdiff were largest for the esophagus (∼0.36 cm) since the esophagus is difficult to visualize on CT, especially in the lower thorax. Overall, visual comparison of GTV manual and auto contours showed good agreement. However, large discrepancies (up to 2cm) were found at the most inferior portion of the lung. This disagreement was also very evident from 3D maps of perpendicular distances between manually‐drawn and deformably‐mapped contours. Conclusion: Automatically‐generated contours using SICLE algorithm can produce high quality contours on subsequent respiratory CT phases. Deformable image registration may reduce or even eliminate the manual contouring workload and can be used for manually‐drawn contour quality assurance.

Supported by NIHgrant‐P01CA11602