bluuebunny/crossref_metadata_2025 huggingface dataset:
WE‐G‐220‐07: Treatment Assessment for Pulsed Focused Ultrasound Therapy of Prostate Tumor Using a Clinical 1.5T MRI
Authors: Chen X , Cvetkovic D , Chen L , Ma C
Published: November 2011

Purpose: Recent in vivo experiments have showed non‐thermal effects of pulsed focused ultrasound (pFUS) on tumor growth delay. This study investigates the application of a clinical 1.5T MR scanner for treatment assessment of prostate tumors after pFUS treatment, which provides a non‐ invasive and accurate way to measure tumor volume for treatment efficacy evaluation, and also an alternative way for small animal tumor model study that generally requires high‐magnetic‐field MRI facility (e.g., the Bruker NMR system). Methods: A mouse tumor model was developed by implanting LNCaP tumor cells in nude mice prostates. When tumor volume reached ∼130 mm3 on MRI, mice were randomly assigned into two groups (n=8): (1) pFUS treatment; (2) control. MRI‐guided pFUS treatment was performed using InSightec ExAblate 2000 with a 1.5T GE MR scanner. Non‐thermal pFUS was delivered for 60 sec per sonication (1MHz; 25W acoustic power; 10% duty cycle, on/off=0.1/0.9 sec). The body temperature was kept <42°C as measured in real‐time by MR thermometry. A total of 4– 8 sonications were used to cover the whole tumor target for each animal. Weekly MR scans were performed using 1.5T scanner to monitor the tumor growth. A ring‐shape surface coil (3 inches) was used for MR signal detection. T2‐weighted MR imaging used fast‐recovery fast‐spin‐echo (FRFSE) sequence with parameters: TR/TE=2200/85ms, NEX=3, matrix=288×288, FOV=7×7 cm2 (resolution=0. 137×0.137mm2), slice thickness=2/1 mm (coronal/axial). Results: Tumor growth delay was quantified using the clinical 1.5T MR scanner after pFUS treatment while normal tumor growth was clearly observed in the control group. A >40% reduction in tumor volume was shown in mice treated with pFUS compared to that for the control mice Conclusion: Clinical 1.5T MRI is able to assess the tumor volume change after pFUS treatment for a small animal model (tumor size: 3–10mm). It may provide an alternative way for treatment assessment for small animal studies.

This work is supported by Focused Ultrasound Surgery Foundation, Varian Medical Systems, DOD PC073127 and DOD BC102806.
TH‐A(SAM)‐BRC‐01: Physics and Dosimetry of SBRT
Authors: Miften M , Kavanagh B , Agazaryan N
Published: November 2011

SBRT is a novel cancer treatment strategy where ultra‐high doses per fraction are used, generally in the range of 6 to 20 Gy per fraction, in a hypofractionated regimen of 5 or fewer fractions. Such high doses per treatment were inconceivable in the past because of concerns about radiation‐induced injury to normal tissue if large volumes of OARs were irradiated to high doses. However, with recent technical advancements in highly‐conformal treatment planning, image‐guided radiotherapy, and delivery technologies, it has become possible to deliver safely very large fractional doses of radiation to lesions in the lung, liver, spine, and prostate. Since SBRT involves technically sophisticated patient repositioning and treatment delivery procedure, it is not uncommon for a treatment to last 40 minutes. Clinicians are usually concerned of a possible compromise in treatment efficacy for individual fractions that require long treatment time because of tumor intra‐fraction motion and patient involuntary movement during radiation delivery, as well as a theoretical risk of intra‐fractional radiation damage repair within tumor cells in the context of prolonged fractional delivery time. In this session, methods for effective, optimal and accurate planning, and efficiency and robustness in the delivery of SBRT, including QA, will be presented so that these concerns are minimized. Furthermore, the technical challenges associated with the clinical implementation of SBRT will be discussed, thereby allowing the wide application of SBRT using current treatment planning and delivery technologies (fixed‐field 3DCRT/IMRT, dynamic arcs, rotational IMRT).

The specific objectives of the session are to:

1. Describe secure and comfortable immobilization techniques to minimize patient movement, techniques accounting for internal organ motion, and accurate patient repositioning methods using online imaging

2. Discuss treatment planning methods to ensure coverage of tumor volume within high dose regions with very rapid fall‐off to surrounding OARs, including the use of Monte Carlo algorithms

3. Describe quality assurance and verification techniques for fixed‐field (3DCRT, IMRT) and rotational (static/dynamic arcs, VMAT/Rapid Arc/Tomo) delivery, usually characterized by many small beam segments, and the assessment of target conformity coverage, and high dose “spillage” region
TH‐A‐224‐02: Atlas‐Based Auto‐Segmentation of CT Images for Radiotherapy Planning
Authors: Han X
Published: November 2011

Treatment planning for high precision radiotherapy of cancer patients requires accurate delineation of both target volumes and critical structures from the planning CT image. Manual contouring is tedious and suffers from large inter‐ and intra‐rater variability. Tools for automated segmentation are thus needed.

Atlas‐based approaches have become popular for automatic medical image segmentation due to its general applicability and advancements in deformable image registration techniques. In this talk, we present our research on developing fully automated, atlas‐based methods for segmenting organs at risk from CT images in radiotherapy planning.

One particular atlas registration approach that we developed employs a hierarchical scheme and makes use of object shape information in the atlas to improve the registration efficiency and robustness while still being able to account for large inter‐subject shape differences. Together with a multi‐atlas fusion strategy, accurate segmentation results can be obtained for images of different anatomical sites. To make multi‐atlas segmentation computationally feasible, we also take advantage of recent advancements in GPU technology and have implemented our method on NVIDIA GPU cards. The GPU acceleration allows the auto‐segmentation of a typical CT image with 10 atlases to be computed within a time‐frame of several minutes.

After presenting validation results, we conclude the talk with discussions about future research directions.

Learning Objectives:

1. Understand the basic principle and workflow of atlas‐based image segmentation

2. Understand how atlas‐based image segmentation technology can help improve consistency and efficiency in structure contouring for treatment planning

3. Understand the promises and limitations of existing technology, as well as future research directions
TH‐A‐BRA‐01: Review of the Radiobiological Principles of Radiotherapy
Authors: Orton C
Published: November 2011

Mechanisms by which radiation kills cells and ways cell damage can be repaired will be reviewed. The effect of radiobiological parameters which we can control for radiotherapy will be discussed including dose/fraction, number of fractions, time between fractions, overall treatment time, and the LET of the radiation. Reasons why we fractionate the way we do will be discussed, along with how sparing of normal tissues using conformal techniques might affect optimal fractionation. The importance of time between fractions will be presented, especially if cancer cells which exhibit hyper‐radiosensitivity are present. The linear‐quadratic model for cell survival for high and low dose rate treatments and the effect of repopulation will be presented and discussed. The effect of LET will be presented as far as the RBE is concerned for both high and low doses.

Learning Objectives:

1. To understand the importance for radiation therapy of dose/fraction, number of fractions, time between fractions, dose rate, overall treatment time, and the LET of the radiation.

2. To understand how geometrical sparing of normal tissues might affect optimal fractionation.

3. To understand the linear‐quadratic model for radiotherapy.
TH‐A‐214‐02: Organ Dose, Effective Dose, and Dose Conversion Coefficients in Adult CT: Comparison of Mathematical, XCAT, and ICRP Reference Phantoms
Authors: Zhang Y , Li X , Segars W , Samei E
Published: November 2011

Purpose: To compare organ dose, effective dose, and dose conversion coefficients in adult CT estimated using three types of reference phantoms: (1) hermaphrodite mathematical phantom employed by the imPACT CT dose calculator, (2) reference male and female extended cardiac‐torso (XCAT) phantoms, and (3) ICRP 110 reference male and female phantoms. Methods: Representative CT examinations were selected from the database of clinical adult CT protocols in use at our institution. Organ dose, effective dose, and dose conversion coefficients (the k factor) were estimated for these examinations for a clinical CT system (LightSpeed VCT, GE Healthcare) using three methods, each employing a different type of reference phantoms. The first method employed commercial dosimetry software imPACT using Monte Carlo methods for a reference mathematical hermaphrodite phantom. The second and third methods employed a Monte Carlo program previously developed and validated in our laboratory. In the second method, the male and female extended cardiac‐torso (XCAT) phantoms created from the Visible Human data were used. In the third method, the ICRP 110 male and female phantoms based on ICRP 89 tomographic anatomic data were used. Results: The k factor varied very little between phantoms, with average 0.019 mSv/mGy‐cm (ranging from 0.009 to 0.025) for imPACT phantom and 0.018 mSv/mGy‐cm (ranging from 0.013 to 0.022) for XCAT male phantom. Distributed organs tended to have similar dose values among different phantoms for the same protocol. The calculated percent difference between imPACT and XCAT male phantom was 1.4% for bone marrow and 9.3% for bone surface. Percent differences between phantoms were generally inversely proportional with scan length ranging from 21.1% for chest‐abdomen‐pelvis protocol to −94% for liver to kidneys protocol. Conclusions: This work suggests that gender averaged dose from anthropomorphic phantoms should be used as reference to adult patient CT dose.
TH‐A‐214‐09: Direct Measurement of Skin Dose from CT Brain Perfusion Scans
Authors: Rong J , Kappadath SC , Schellingerhout D
Published: November 2011

Purpose: To directly measure skin dose using point‐dosimeters from clinical CT brain perfusion scans and compare these measurements to estimates using the standard CTDI100 method. Methods: Our clinical brain perfusion scan protocol included 11 axial 80kVp scan groups plus 2 helical 120kVp scan groups. The Landauer OSL nanoDOT dosimeters were calibrated using the same kVpˈs as the clinical protocol. Using nanoDOT dosimeters, skin doses at several positions on the surface of an anthropomorphic adult head phantom were measured during a perfusion protocol. The head CTDI 100 was also measured using a 100mm‐pencil CT ion chamber. The standard CTDI100 method estimates peak skin dose from the brain perfusion scans based on the head CTDI100(top) for axial scans plus the head CTDI100(top)/pitch for helical scans. The peak skin dose estimated from the CTDI100 method was compared with the measured values at different locations on the anthropomorphic phantom. Results: The measured skin doses ranged from 0.11 to 0.95Gy depending on dosimeter positions. The highest dose location was located at the left‐front surface laterally ∼3cm above the ear, and the lowest dose was at the back‐center surface ∼4cm from the top. The surface doses to the locations of the eyes were ∼0.23Gy. Dose origin was ∼89% from the axial scans, ∼11% from the helical scans, and <1% from the scouts. The CTDI100 method overestimated the peak skin dose to a typical adult head size, by ∼20%. No image artifact was caused by presence of nanoDOT dosimeters in scan FOV. Conclusions: Direct measurements of skin dose using nanDOT dosimeters provided accurate and precise skin dose values without any image artifacts. CTDI100 method overestimated the skin doses for our clinical CT brain perfusion scans. Direct measurements rather than estimates will be useful in terms of: a) documenting real patient dose, and b) guiding future dose optimization efforts.
TH‐A‐220‐01: An Automated Optimal ROI Discovery Method for Real‐Time 3D Surface Image Monitoring of Head Motion
Authors: Kang H.J. , Grelewicz Z , Wiersma R
Published: November 2011

Purpose: To increase image registration accuracy, and to remove the time‐ consuming manual region‐of‐interest (ROI) selection process for patient monitoring 3D surface imaging systems (AlignRT,VisionRT,UK), a method was developed to adaptively define an optimal ROI based on discovering topographically stable surfaces over time. Methods: Our method calculates the displacement and velocity of 3D surface points between a series of images captured in real‐time and the reference image. Using a set of selection criteria, the algorithm adaptively constructs a ROI by including only facial surfaces that move rigidly with the target and excludes surfaces that fluctuate locally such as the mandible regions and eyes. Data for five volunteers were acquired over various facial surface and motion types. A total of 27 data sets were analyzed, with 2–7 data sets for each volunteer and each data set contained consecutively captured 40–120 real‐time images. Results: The adaptive ROI selection algorithm correspondingly detected surfaces affected by different types of facial movement independent of target motions. It interpreted the eyes, eyebrows and mandible motions shown in the real‐time 3D images as independent of target motion even when AlignRT misinterpreted them, and excluded them from the final ROI. For 3D images taken with substantial facial motions, either most of the facial areas were excluded or only small areas with random patterns were included in the final ROI. The algorithm excluded the upper side and nose where the view of the cameras was blocked, and thus surface was not well‐ reconstructed in many of real‐time 3D images when couch was rotated greater than 40°. Conclusion: The method successfully located suitable ROI surfaces undergoing minimal displacement and temporal fluctuation. By automating the ROI selection process, the time and complexity of current ROI definition can be reduced, together with user‐dependent registration errors.
TH‐A‐220‐06: Four‐Dimensional MRI/CT Based Auto‐Adaptive Segmentation for Real‐Time Radiotherapy in Lung Cancer Treatment
Authors: Chebrolu V , Tewatia D , Dai J , Saenz D , Sethares W , Fain S , Paliwal B
Published: November 2011

Purpose: To enable real‐time magnetic resonance (MR)/computer tomography (CT) image‐guided radiotherapy (IGRT) and to reduce treatment planning durations in the radiotherapy of lung cancer through the design and implementation of computationally efficient four‐dimensional (4D) MR/CT based automated segmentation algorithms. Methods: Hyperpolarized helium‐3 (HP3He) and proton‐density 4DMRI lung data was acquired for six subjects. Thoracic 4DCT data often subjects with lung cancer was also acquired. Automated segmentation was performed using a novel Morphological Processing and Successive Localization (MPSL) approach. Three different MPSL segmentation algorithms were developed to segment the regions of tumor, body and lung respectively. MPSL segmentation: A mask that includes the intensity range of the region‐of‐interest was generated. Then morphological processing (and/or reconstruction) was performed to separate the target volume(s) from other regions. Then the different connected regions were labeled using the union‐find algorithm and their areas/volumes were calculated. A limit on the maximum/minimum possible area/volume of the target volume was used as a filter to segment the target volume. Morphological processing/reconstruction were performed again to create the final contours. Results: MPSL was shown to successfully segment the regions‐of‐interest (tumors, lung and body) from the images with both high and low signal‐to‐ noise ratio. With the use of 3D processing and successive localization MPSL was shown to separately classify tumor and diaphragm (that may appear within the 2D contours of the lung). MPSL segmentation was compared with manual segmentation. Average computational time for achieving automated lung segmentation using MPSL on one phase volume (128×128×128) of 4D HP3He MR data was 0.5s. For proton‐density 4DMRI data, the average time for automated segmentation of body and lung on one phase volume (128×128×128) was 2s. Conclusions: With the computation speed of the order of seconds for achieving automated segmentation, MPSL has realistic potential for application in real‐time image‐guidance for adaptive radiotherapy.
TH‐A‐220‐09: A Study of Prostate Edema Resolution Pattern by Principle Component Analysis
Authors: Jiang Y , Zhai Y , Papademetris X , Roberts K , Pathare P , Nath R , Chen Z
Published: November 2011

Purpose: To investigate and characterize the spatial resolution patterns of prostate edema in permanent prostate brachytherapy for accurate post‐implant dosimetry. Methods: Three patients with prostate cancer received 103Pd seed implant (day‐0) and consented to participate in an IRB approved post‐implant serial CT imaging study. Patient 1 was scanned on days: −1,1, 7, 10, 17, 30, 42; Patient 2: −1, 0, 1, 7, 16, 40; and patient 3: −1, 0, 1, 6, 11, 15, 30, 42. The image of patient 1 on day‐0 was contoured by a radiation oncologist and set as the template image for registration using a validated deformable image registration algorithm. For all voxel points inside the prostate in the template image, their corresponding coordinates in the subsequent images were obtained by the resulting deformation fields. These point sets were further aligned by rigid shape registration so as to reflect the intrinsic edema resolution. Principle component analysis (PCA) was used to compute the variation pattern among the point sets of each patient, and also among the point sets averaged from all patients on days −1, 1, 6/7, 15/16/17, and 40/42. Results: The percentages of the greatest four components of variation over the total variation are 92.0%, 2.9%, 2.1%, 1.2% for patient 1, 43.8%, 32.0%, 10.4%, 8.2% for patient 2, 45.6%, 15.1%, 12.3%, 10.5% for patient 3, and 63.0%, 18.4%, 11.3%, 7.2% for the averaged one. The greatest four components of variation plotted on the surfaces of prostate and of a sphere of similar size provided an easy visualization of major edema resolution patterns. Conclusions: Strong anisotropic edema resolution patterns were observed in patients receiving permanent prostate brachytherapy. PCA analysis and visual inspections indicated that different patients have significantly different edema resolution patterns. It suggests that spatial anisotropy of edema resolution should be considered for accurate dosimetry.

This research project is currently funded by the NIH grant R01CA134627‐01
TH‐B‐224‐02: PET Image Segmentation for Radiation Therapy
Authors: Kirov A
Published: November 2011

Positron emission tomography (PET) brings to radiation therapy of cancer the critical advantage of defining the tumor based on its molecular properties. However, delineating the gross tumor volume (GTV) with PET is problematic due to the uncertainties in the biological and physiological processes governing the tracer uptake and to the instrumental inaccuracy of the PET images. Despite this, the delineation of tumors in PET images is used in radiation therapy for target definition, dose painting and treatment outcome assessment.

The lecture will provide examples of the different tumor segmentation tasks and point to the different requirements they may present. It will further point to the segmentation challenges arising from the PET image specifics, inaccuracies and uncertainties. It will also propose a classification of the auto‐segmentation methods used in PET and provide examples of few auto‐segmentation methods representative of the different classes. Finally, the need of evaluation and validation of the segmentation techniques will be discussed.

Learning objectives:

1. Understand the different requirements to PET segmentation set by the specific goal.

2. Be aware of the physical properties of PET images which affect segmentation accuracy.

3. Be able to provide a simple classification of the auto‐segmentation tools and explain the need for validation.
TH‐B‐301‐01: FFDM Quality Control Testing in Canada ‐ a Vendor‐Neutral Approach
Authors: Rajapakshe R
Published: November 2011

Lack of national and international standards for quality control for digital mammography dictates that users have to follow manufacturerˈs recommendations. This leads to significant additional work for facilities with digital mammography systems from multiple vendors. Therefore, a comprehensive and unified quality control test for medical physicists and mammography technologists was developed for the Screening Mammography Program of British Columbia (SMPBC), in collaboration with Ontario Breast Screening Program with the intent of using them as a national standard in Canada.

The quality control tests developed for the ACRIN DMIST study were used as the starting point for the new tests; however, due to the recent implementation of AEC algorithms by some manufacturers, it has become difficult to use the uniform phantom suggested by DMIST work. To address this, a simple 19 cm diameter semicircle uniform phantom was designed. Furthermore, it was found that the technologist weekly image quality test should be performed on “FOR PRESENTATION” images so that changes in image processing algorithms (similar to changes in film processing conditions) can be identified. IHE Mammography Integration Profile compliance was also included as part of the Medical Physicists tests.

The new unified quality control procedures have been adopted as the standard in the province of BC for more than two years. This unified approach has made it possible to streamline and manage the quality control of screening mammography facilities within the province. The technologist weekly image quality test done with “FOR PRESENTATION” images instead of “FOR PROCESSING” images (as suggested by ACRIN DMIST study findings) have uncovered changes in image processing algorithms that were implemented by manufacturers without the knowledge of the users. The new semicircle uniform phantom is found to be suitable for testing the AEC performance of every digital mammography unit used in the province of BC.

Due to the success in the use of the new unified QC tests in the province of BC, we are in the process of promoting this as a national standard for digital mammography quality control in Canada.

This presentation will provide an overview of the development and implementation of these vendor neutral unified quality control procedures and its advantages.

Learning Objectives:

1. Understand the type of testing required for Digital mammography systems.

2. Understand the advantages of a unified QA procedure.

3. Understand some of the technical and logistical issues involved in implementing vendor neutral QA procedures.

4. Understand the importance of using IHE Mammography Integration Profile as part of the Medical Physicist testing.
TH‐C‐224‐01: Reimbursement: Resources and Updates
Authors: Goodwin J
Published: November 2011

Healthcare reimbursement is a complex, changing environment with multiple payers and multiple sets of rules. The practicing medical physicist should be familiar with reimbursement and coding so that he/she can: 1) assure that fair reimbursement is received for the physics work performed, 2) assure that physics billing is done correctly and in compliance with applicable rules and procedures, and 3) justify the physics staffing levels necessary in the clinic. This presentation will build upon previous general reviews of the mechanisms of Medicare reimbursement and will cover practical aspects for the practicing physicist including where to find information on reimbursement and coding. The National Correct Coding Initiative (NCCI) and Medically Unlikely Edits (MUE) and their effect on daily billing will be reviewed. In addition, proposed changes in the Hospital Outpatient Prospective Payment System (HOPPS) and Medicare Physician Fee Schedule (MPFS) for calendar year 2012 will be discussed.

Learning Objectives:

1. Become familiar with available resources for reimbursement and coding

2. Understand the National Correct Coding Initiative and Medically Unlikely Edits

3. Be aware of proposed changes in Medicare reimbursement for 2012
TH‐C‐BRA‐02: Adaptive Image‐Guided Radiation Therapy: A Physicianˈs PerspectiveTherapy Symposium
Authors: Mundt A
Published: November 2011

Image guided radiation therapy (IGRT) today is focused on the use of in‐room imaging technologies to improve patient setup and target localization. IGRT in the future, however, will also include the use of imaging to adapt treatment to changes in the tumor (and patient) during treatment. One of the most important changes which can be adapted to is in morphology of both the tumor and surrounding normal tissues. Newer in‐room volumetric imaging opens the door to adapting to such changes. Discussion of adaptive IGRT quickly turn to the technical issues involved including automated segmentation and deformable registration. However, a fundamental understanding of the variety and frequency of morphologic changes which occur is crucial to the development of adaptive IGRT strategies. This lecture reviews the morphologic changes which occur during treatment of patients with CNS, Head and Neck, lung, gastrointestinal, breast, gynecologic, genitourinary and pediatric tumors. Published data on adaptive IGRT approaches in a variety of tumor sites will also be presented.
TH‐C‐BRC‐02: Development of a Lung Tumor Motion Predictor for Intra‐Fractional Tumor Tracking Based on a Self‐Optimizing Artificial Neural Networks (ANN)
Authors: Yun J , MacKenzie M , Rathee S , Fallone B
Published: November 2011

Purpose: To develop a newly designed lung tumor motion predictor for intra‐fractional MR tumor tracking based on self‐optimizing artificial neural networks (ANN). The new predictor could resolve practical issues of (1) ANN structure optimization and (2) tumor tracking failure due to MLC stopping. Methods: An adaptive, 4 layered feed‐forward ANN was built to predict future positions of lung tumor. The ANN training was performed with back‐propagation learning along with a self‐adaptive learning rate. A particle swarm optimization was implemented in the predictor to optimize and customize the ANN structure and its weights for each patient. To minimize tracking failures due to MLC stopping, we implemented a dual ANN structure in our predictor, so that multiple consecutive future positions of MLC could be assigned at each prediction. We extracted 8 minutes long, 1D superior‐inferior lung tumor motion patterns from the first 3 fractions of 10 lung cancer patientsˈ data. These were used to evaluate the performance of our predictor by calculating root‐mean‐square‐error (RMSE) and normalized RMSE (nRMSE : normalized to the max. amplitude of given original data) between the original and predicted pattern. Results: For each of 10 patients, tumor motion patterns were predicted in 2 fractions. The maximum amplitude of original pattern ranges from 4.87 to 19.72 mm. All optimized ANN structures contains 2 hidden layers except in one case. RMSE values ranged 0.26 to 1.01 mm, and nRMSE ranged from 4.46 to 10.11%. In most cases, RMSE were less than 1mm with nRMSE less then 10%. Conclusions: A self‐optimizable lung tumor motion predictor was developed based on adaptive ANNs. The predictorˈs performance was evaluated with 10 lung cancer patientsˈ data. The results suggest ANN structure with 2 hidden layers for lung tumor motion prediction, as well as the necessity of individually optimized predictor for each patient.
TH‐C‐BRC‐10: Fluoroscopic Lung Tumor Tracking Based on Real‐Time Deformable Image Registration
Authors: Gu X , Jia X , Graves Y , Jiang S
Published: November 2011

Purpose: To develop a real‐time and accurate lung tumor tracking algorithm from fluoroscopic images based on deformable image registration. Methods: The new tracking algorithm is developed based on deformable image registration (DIR) of fluoroscopic images using our GPU‐based Demons algorithm. Choosing an initial frame image as a reference image, we deform all the incoming frame images to this reference image to obtain deformation vector fields (DVFs). And consequently, the physician contoured tumor region on the initial frame can be properly propagated to the incoming frames and the new tumor location can be obtained by calculating the centroid of the propagated tumor. Results:The proposed tracking algorithm is initially tested on four lung cancer patientsˈ fluoroscopic images. The average computation time for the tumor tracking for each frame is between 0.21 and 0.26 seconds on an NVIDIA Tesla C1060 equipped workstation. The accuracy of tracking results are quantified by comparing the numerical tracking tumor centroid with physician determined tumor centroid in each frame. In superior‐inferior direction, the average of tumor centroid localization error is found to be 0.97 mm for the best testing case and 1.29 mm for the worst cases, and the error at 95 percentile is smaller than 3.2 mm for all testing cases. In lateral direction, the average error is in the range between 0.8 and 1.02 mm, and 95% error is smaller than 3.5 mm for all testing cases. The average of 2D vector errors range from 1.49–2.00mm and 95% 2D error is smaller than 4.0mm. Conclusions:The preliminary results indicate that high computational efficiency and tumor location accuracy can be achieved using the proposed real‐time DIR based lung tumor tracking method. This method provides a real‐time markerless tumor tracking tool for lung cancer radiation therapy.
TH‐C‐110‐03: Pitfalls and Remedies of MDCT Scanners as Quantitative Instruments
Authors: Hsieh J
Published: November 2011

Objectives: CT HU accuracy is influenced by the fundamental properties of x‐ray physics, CT system calibration processes, data acquisition hardware and protocols, image reconstruction techniques, and patient preparation and handling. With a renewed and increased importance of quantitative imaging, this talk will provide an overview on this issue and focus on a few specific areas: scatter, beam‐hardening effect, CT components and system impact, and data acquisition protocols. Various techniques to reduce, correct, or avoid the pitfalls are presented. Current system limitations and new technologies to overcome the shortcomings will also be discussed.
TH‐C‐110‐04: Dual Energy CT Imaging for Density Measurements
Authors: Pelc N
Published: November 2011

Purpose: Diagnostic CT scanners use polychromatic x‐ray beams, which introduces errors from beam hardening. If the object is composed of a single material corrections for beam hardening can be exact but if the object is heterogenous some errors would remain. Dual energy CT can avoid these errors and can also provide atomic number information.

Methods: If transmission measurements at two or more energies are obtained, even with polychromatic beams, more specific information about the object can be obtained. In the diagnostic energy range and if there are no materials with k‐edges in the spectrum, the x‐ray attenuation can be described by a linear combination of two processes (photoelectric absorption and Compton scattering) or, equivalently, two basis materials. The process of calculating the amount of the two basis functions implicitly corrects for beam hardening and therefore can lead to improvements in quantitative accuracy. Implementations of dual energy include dual‐source, rapidly switching kVp sources, dual layer detectors and energy discriminating detectors.

Results: Dual energy CT can correct for beam hardening. It can quantify effective atomic number and electron density in each voxel. It can also quantify the amounts of specific materials even in heterogenous voxels. The precision of the dual energy information is limited by statistics and the accuracy can be compromised by scatter.

Conclusion: Dual energy CT can provide additional information for quantitative measurements with CT but its limitations need to be appreciated as well.

Research sponsored by GE Healthcare.

The learning objectives are to familiarize the audience with

1. basic principles of dual energy CT

2. implementations of dual energy CT

3. basis material decomposition

4. dual energy CT can characterize materials and correct for nonlinearity (e.g., beam hardening)

5. limitations of dual energy CT
TH‐C‐211‐01: International Perspectives on Radiation Protection
Authors: Rehani M , Suleiman O , Rajapakshe R
Published: November 2011

There are some actions which require international cooperation. An example of good cooperation can be found in the largely seamless international use of credit cards and ATM machines. Conversely, an example where international cooperation has not been effective can be found in the diversity of electricity plugs and sockets in different countries. In the area of radiation protection, there are also examples of good and bad cooperation. The global acceptance of concepts and principles of radiation protection as developed by the International Commission on Radiological Protection (ICRP) such as justification, optimization and dose limitation is a good example. Conversely, there are quite a few examples of non‐agreement or partial agreement of issues in the field of radiation protection, such as dose limits for workers and members of the public, and acceptance of SI units e.g. Sv and Gy against rem and rad. When it comes to radiation protection of patients, there is Universityersal agreement that there should be no dose limits and that the concept of diagnostic reference levels (DRLs) should be used with flexibility. International actions are needed not only to create harmonization of concepts but also to give impetus to some areas, raise awareness about emerging issues and forewarn about upcoming dangers if actions are not initiated by countries well in time.

The talk will cover “How does the International System of Radiation Protection work” and inform about an International Action Plan on Radiation Protection of Patients of the IAEA. Is the international system binding or national systems are?. How harmonization is achieved through the work of the IAEA. Ultimately, the role medical physicists and health physicists in implementing the radiation protection requirements for staff and patient protection shall be discussed.

Learning Objectives:

1. To understand the system of radiation protection in international and national context

2. To become familiar with international action plan on radiation protection of patients

3. To become familiar with international organizations in the area of medical radiation protection

4. To understand the potential role you can play in international activities
TH‐C‐301‐02: Advanced Portable Radiation Instruments of Diagnostic Imaging QC
Authors: Jordan D
Published: November 2011

This presentation will highlight the features, benefits, and limitations of solid‐state radiation detectors for diagnostic radiology QC applications. The focus will be on types of solid‐state detectors typically used in commercial portable survey instruments. Practical aspects will include calibration procedures and intervals, directional and energy dependence of detector response, and user options such as configurations, settings, and triggering. The objectives of this session are twofold. First, the user of such instruments should be able to determine which applications are appropriate and inappropriate for a given detector. Second, the user should be able to choose the best detector for a given application.
TH‐C‐220‐10: Limit of Setup Accuracy Using Bioluminescence Imaging to Guide Focal Pre‐Clinical Irradiation
Authors: Wong J , Armour M , Tuli R , Herman J , Artemov D , Patterson M
Published: November 2011

Purpose: Cone beam CT (CBCT) on‐board new small animal radiation research platforms (SARRPs) is inadequate for guiding focal irradiation of targets in soft tissue. In this study, we examined the setup uncertainty using the more sensitive bioluminescence imaging (BLI) and BL tomography (BLT) for off‐line guided irradiation. Methods: A small glass bulb containing BL cells was implanted in six euthanized mice These were handled free‐hand while five others were immobilized. Surface BLI was acquired and BLT reconstructed of each carcass using a Caliper BLI system. An ink‐dot marked the “visual” centroid of the surface BL image. The carcasses were then transported to a SARRP for CBCT localization. In the visual setup, the animal was positioned to align the ink‐dot with the central axis of the SARRP. In the CBCT‐aided setup, the pose of each carcass was adjusted to recapitulate its pose at the time of BLI. The 2D radial offset of the “true” bulb centroid in CBCT from the central axis of the SARRP was measured. In the 3D setup, the 3D contours of CBCT and BLT contours were registered and the 3D radial offset between the 2 centroids was calculated. Results: The results are virtually identical between free‐hand and immobilized setup, as well as using visual and CBCT‐aided 2D setup. The onset of rigor mortis rendered immobilization un‐necessary. The 2D offset from the “true” position of the BL bulb was 2.3 +/− 1.3 mm. The 3D radial offset was 1.5 +/− 0.9 mm, approaching the documented uncertainty in BLT reconstruction. Conclusions: With the stiff carcasses, the results represent the best that can be achieved with off‐line 2D surface BLI and 3D BLT localization. An on‐board approach with further improvement in BLT using prior information of anatomic and optical properties, localization uncertainty less than 1 mm is possible.

Funded in part by a sponsored research agreement from Xstrahl Ltd. Xstrahl Ltd. has a technology transfer Agreement with Johns Hopkins University.
TH‐E‐BRB‐07: Treatment Planning Performance of High Intensity Flattening‐Filter‐ Free Beams for Head‐And‐Neck Cancer: IMRT versus VMAT
Authors: Duan J , Shen S , Popple R , Wu X , Brezovich I
Published: November 2011

Purpose: To evaluate the performance of high‐intensity flattening‐filter‐free (FFF) beams in terms of planning efficiency and dosimetric merits for head‐ and‐neck cancers treated with IMRT and VMAT techniques. Methods: Ten patients with Stage III–IV squamous cell carcinoma of the head and neck were planned with fixed‐field IMRT and VMAT using 6MV flattened, 6MV FFF and 10MV FFF beams. Seven equi‐spaced fields and two axial arcs were used for IMRT and RapidArc, respectively. Prescription doses to the primary and nodal targets were, respectively, 70 and 54 Gy over 35 fractions. Identical dose constraints are used for IMRT and RapidArc plans. Planning times and plan qualities were assessed for IMRT versus RapidArc with flattened and FFF beams. Results: Target doses showed moderately better uniformity and conformity in IMRT plans than in RapidArc plans. While IMRT plans also exhibited some superiority in OAR sparing compared to RapidArc, the improvement is not clinically significant for most patients. The mean time for a single planning iteration was 15.7 minutes for IMRT and 55.0 minutes for RapidArc using an Eclipse workstation with 2.27 GHz Dual Quad‐Core CPUs. The average MU is 682 for RapidArc and 2636 for IMRT. The average MUs for IMRT plans varied greatly among 6MV flattened, 6MV FFF and 10 MV FFF beams requiring 1513, 2580 and 3816 MU, respectively. In RapidArc plans, however, this variation is less than 20% for the three beams. Conclusions: Both IMRT and RapidArc produced clinically acceptable treatment plans with flattened and FFF beams for head‐and‐neck cancers. Fixed‐field IMRT plans showed moderate dosimetric advantage over RapidArc plans but required almost four times the MU. Among IMRT plans, FFF beams required 2–3 times the MU of flattened beams.
Live Diatom Silica Immobilization of Multimeric and Redox-Active Enzymes
Authors: Sheppard V. C. , Scheffel A. , Poulsen N. , Kröger N.
Published: November 2011

Living organisms are adept in forming inorganic materials (biominerals) with unique structures and properties that exceed the capabilities of engineered materials. Biomimetic materials syntheses are being developed that aim at replicating the advantageous properties of biominerals
in vitro
and endow them with additional functionalities. Recently, proof-of-concept was provided for an alternative approach that allows for the production of biomineral-based functional materials
in vivo
. In this approach, the cellular machinery for the biosynthesis of nano-/micropatterned SiO
2
(silica) structures in diatoms was genetically engineered to incorporate a monomeric, cofactor-independent (“simple”) enzyme, HabB, into diatom silica. In the present work, it is demonstrated that this approach is also applicable for enzymes with “complex” activity requirements, including oligomerization, metal ions, organic redox cofactors, and posttranslational modifications. Functional expression of the enzymes β-glucuronidase, glucose oxidase, galactose oxidase, and horseradish peroxidase in the diatom
Thalassiosira pseudonana
was accomplished, and 66 to 78% of the expressed enzymes were stably incorporated into the biosilica. The
in vivo
incorporated enzymes represent approximately 0.1% (wt/wt) of the diatom biosilica and are stabilized against denaturation and proteolytic degradation. Furthermore, it is demonstrated that the gene construct for
in vivo
immobilization of glucose oxidase can be utilized as the first negative selection marker for diatom genetic engineering.
New Approaches for Isolation of Previously Uncultivated Oral Bacteria
Authors: Sizova M. V. , Hohmann T. , Hazen A. , Paster B. J. , Halem S. R. , Murphy C. M. , Panikov N. S. , Epstein S. S.
Published: November 2011

A significant number of microorganisms from the human oral cavity remain uncultivated. This is a major impediment to the study of human health since some of the uncultivated species may be involved in a variety of systemic diseases. We used a range of innovations previously developed to cultivate microorganisms from the human oral cavity, focusing on anaerobic species. These innovations include (i)
in vivo
cultivation to specifically enrich for species actively growing in the oral cavity (the “minitrap” method), (ii) single-cell long-term cultivation to minimize the effect of fast-growing microorganisms, and (iii) modifications of conventional enrichment techniques, using media that did not contain sugar, including glucose. To enable cultivation of obligate anaerobes, we maintained strict anaerobic conditions in most of our cultivation experiments. We report that, on a per cell basis, the most successful recovery was achieved using minitrap enrichment (11%), followed by single-cell cultivation (3%) and conventional plating (1%). Taxonomically, the richest collection was obtained using the single-cell cultivation method, followed by minitrap and conventional enrichment, comprising representatives of 13, 9, and 4 genera, respectively. Interestingly, no single species was isolated by all three methods, indicating method complementarity. An important result is the isolation and maintenance in pure culture of 10 strains previously only known by their molecular signatures, as well as representatives of what are likely to be three new microbial genera. We conclude that the ensemble of new methods we introduced will likely help close the gap between cultivated and uncultivated species from the human oral cavity.
Molecular Survey and Genetic Identification of Anaplasma Species in Goats from Central and Southern China
Authors: Liu Zhijie , Ma Miling , Wang Zhaowen , Wang Jing , Peng Yulv , Li Youquan , Guan Guiquan , Luo Jianxun , Yin Hong
Published: November 2011

Anaplasmaspecies are obligate intracellular rickettsial pathogens that impact the health of humans and animals. Few studies have been carried out onAnaplasmainfections in central and southern China. This study was conducted to determine the coinfection rates ofAnaplasma ovis,A. bovis, andA. phagocytophilumfrom 262 field blood samples of goats in these regions. The average prevalences of single infection ofA. ovis,A. bovis, andA. phagocytophilumwere 15.3, 16.0, and 6.1%, respectively. Coinfection ofA. ovisandA. boviswas dominant, with an infection rate of 27.1%. Coinfection ofA. ovisandA. phagocytophilumwas 1.9% and that ofA. bovisandA. phagocytophilumwas 4.2%. Three-pathogen coinfection was found in three of four investigated provinces with a prevalence between 0 and 5.3%. The accuracy of the PCR results was corroborated by sequencing. Analysis of the 16S rRNA gene sequences ofA. bovisandA. phagocytophilumconfirmed the presence of these pathogens at the investigated sites and indicated the possible genetic diversity ofA. phagocytophilum. Field blood inoculation of experimental animals led to successful identification and observation of the morphological shapes ofA. bovisin the infected monocytes of sheep. Phylogenetic study withmsp4sequences ofA. ovisindicated that theA. ovisgenotypes from sheep in the north differed from the genotypes of goats in the investigated sites.
The Neurospora crassa DCC-1 Protein, a Putative Histidine Kinase, Is Required for Normal Sexual and Asexual Development and Carotenogenesis
Authors: Barba-Ostria Carlos , Lledías Fernando , Georgellis Dimitris
Published: November 2011

Two-component signaling pathways based on phosphoryl group transfer between histidine kinase and response regulator proteins regulate environmental responses in bacteria, archaea, plants, slime molds, and fungi. Here we characterize a mutant form of DCC-1, a putative histidine kinase encoded by the NCU00939 gene of the filamentous fungus
Neurospora crassa
. We show that this protein participates in the regulation of processes such as conidiation, perithecial development, and, to a certain degree, carotenogenesis. Furthermore, DCC-1 is suggested to exert its effect by promoting cyclic AMP production, thereby placing this protein within the context of a signaling pathway.
FtsZ-ZapA-ZapB Interactome of Escherichia coli
Authors: Galli Elisa , Gerdes Kenn
Published: November 2011

Bacterial cell division relies on the formation and contraction of the Z ring, coordinated and regulated by a dynamic protein complex called the divisome. The cell division factor ZapA interacts directly with FtsZ and thereby increases FtsZ protofilament association and Z-ring stability. Here, we investigated ZapB interaction with ZapA and its effect on Z-ring formation and FtsZ protofilament bundling. The combination of the
ftsZ84
allele that encodes an FtsZ variant that polymerizes inefficiently with a
zapB
null mutant resulted in a synthetic defective phenotype. Overproduction of ZapA led to the formation of aberrant FtsZ helical structures and delocalization of ZapB. The N-terminal end of ZapB was essential for ZapB-ZapA interaction, and amino acid changes close to the N terminus of ZapB exhibited reduced interaction with ZapA. Sedimentation assays showed that ZapB interacts strongly with ZapA and reduces ZapA's interaction with FtsZ
in vitro
. The morphology of the structures formed by ZapA and ZapB together was similar to the cables formed by ZapB in the presence of CaCl
2
, a known ZapB bundling agent. The
in vivo
and
in vitro
data support a model in which ZapA interacts strongly with ZapB and the ZapA-ZapB interaction is favored over ZapA-FtsZ.