bluuebunny/crossref_metadata_2025 huggingface dataset:
MO‐B‐201C‐01: Color Monitors for Medical Workstations
Authors: Flynn M , Samei E , Badano A , Roehrig H
Published: August 2010

Business class monitors are now widely used to display radiologic images for primary interpretation and for secondary display in the health enterprise. This course will review the technology and performance available in current products and discuss the increasing need to control the presentation of color images.

Learning Objectives:

1. Understand the types of products currently available that provide color presentation with performance suitable for primary interpretation by radiologists.

2. Learn the basic aspects of ICC color management and how ICC profiles are incorporated in DICOM tags.

3. Understand the types of products currently available for secondary presentation of color images in the health enterprise

4. Learn how secondary class monitors can be calibrated to conform with the DICOM Gray Scale Display Function (GSDF).

5. Learn how color monitors can be calibrated to conform with an ICC target profile.
MO‐D‐204B‐06: Segmentation Evaluation in the Context of Inter‐Physician Variance
Authors: Deeley M , Datteri R , Chen A , Moretti L , Niermann K , Noble J , Ding G , Dawant B
Published: August 2010

Purpose: To evaluate a registration‐based system for intracranial segmentation in the context of multiple physicians and cases of large space‐occupying brain lesions. Method and Materials: Segmentation analyses suffer from the absence of a known ground truth and a single adequate comparison metric. However, these limitations can be overcome by applying multiple metrics and statistical methods to large data sets. We enlisted 8 physicians to delineate the brainstem, chiasm, optic nerves, and eyes in 20 challenging patient volumes. Our system utilizing the adaptive bases algorithm automatically segmented these structures. The expert delineations formed probability maps (p‐maps) that were used to calculate a simulated ground truth. We evaluated inter‐physician and automatic‐physician variation using the Dice similarity coefficient. Each was then evaluated against the ground truth using Dice and Euclidean distance maps. To understand the observed variance at the edges of delineations, we sampled the p‐maps and fitted a linear regression model. Results: Across all structures and patients in pair‐wise Dice comparisons, the automatically derived structures compared as well or better to the physician delineations than did the physicians with one another. The inter‐physician spatial overlap for brainstem and eyes was over 80%, while for the optic chiasm and nerves it was only 40–50 percent. Median Euclidean distances to a simulated ground truth were less than 2 mm for both the automatic and physician delineations, and maximum deviations were generally less than 5 mm. Of the total p‐map variance only 20% was explained by main effects of physician, case and structure, and their interactions, suggesting the delineations are inherently noisy. Conclusion: The fully automatic system produced segmentations geometrically equivalent to those delineated by a group of physician experts. This work underscores the need for multiple physicians and metrics to avoid bias in evaluating segmentation results.
MO‐D‐201B‐04: Emerging X‐Ray Detector Technologies
Authors: Zhao W , Hsiao H , Wronski M , Rowlands J
Published: August 2010

The main topic of this Symposium talk is new development of selenium based x‐ray imaging detectors. Some of these new developments include: 1. Very high‐resolution direct‐conversion detectors for breast imaging; 2. Large area detector with low‐noise CMOS readout; 3. Large‐area indirect conversion flat‐panel imager with avalanche gain obtained with an optically sensitive selenium layer; 4. Possible approaches for 2D photon‐counting detector with selenium. The physics of direct and indirect conversion x‐ray imaging detectors will be described, and the limitations of existing detector technologies outlined. The basic principle of operation of the emerging detector technologies will be explained, and the rationales for their improved performance and potential clinical applications will be summarized.

Learning Objectives:

1. Understand the basic physics of x‐ray imaging detectors using either direct or indirect conversion

2. Understand the factors affecting imaging performance, and the limitations of different detector approaches

3. Learn the advantages of some emerging x‐ray imaging detector technologies that can address existing problems
MO‐EE‐A3‐04: Development and Dosimetric Studies of Independent Dose Validation Software on Helical Tomotherapy
Authors: He W , Shi C , Quino L Vazquez , Dzintars E , Gutiérrez A , Stathakis S , Alkhatib H , Papanikolaou N
Published: August 2010

Purpose: To develop a 2nd dose validation software for helical TomoTherapy, study the sensitivity of the commission data variation on the final dosimetry impact, and inter‐fraction setup uncertainty effect for patient quality assurance. Method and Materials: A 2nd dose validation software for helical TomoTherapy, called MU‐Tomo, has been developed to independently validates point dose upon archived patient documents, initial coordinates and planned dose of point of calculation, and common dosimetric functions. MU‐Tomo has been validated with a hundred cancer cases (30 prostate, 26 head&neck, 18 lung, 17 pelvis, and 9 brain patients). Sensitivity studies were performed by oscillating fluctuation regions of off‐axis profiles, shifting, and rotating profiles. Daily setup shifts were quantified into systematic and random shifts to evaluate dosimetric variations, separately. Results: For dose validation, 98% of dose differences are within ±5% with mean 0.20%±2.06%. Sensitivity studies show linear response by oscillating OARy, 15 times larger dose variation by shifting OARy than OARx, and less than 1.5% difference by rotating OARx in ±6° and more than 5% in ±1° by rotating OARy. Systematic variations are up to −10.02%±3.00%. Mean random variations are up to −5.65%±1.90%. ANOVA analyses show significant differences among patient random dosimetric variations and systematic dosimetric variations between head&neck‐brain group and body group. Variations are not significantly correlated with treatment fraction number with the Pearson correlation analysis. The overall random dosimetric impacts to each patient are ‐ 0.0053%±1.11%. Conclusion: MU‐Tomo, has been developed for TomoTherapy dose validation. Sensitivity studies on fifty patients have been evaluated that OARy profiles are more sensitive than OARx in dose calculation. Dosimetric consequences due to inter‐fractional setup shifts on a hundred helical tomotherapy patients were assessed.

Conflict of Interest: This project was supported in part by Oncology Data Systems, Inc., Oklahoma City, OK, USA.
MO‐E‐204C‐03: On the Development of On‐Board PET with Tomotherapy Using Open Dual Ring Geometry
Authors: Darwish N , Mackie T , Thomadsen B , Kao C
Published: August 2010

Purpose: Positron emission tomography (PET) using open dual ring geometry was investigated as an on‐board system for functional imaging and PET marker tracking, specifically with tomotherapy. The dual ring PET would allow measurement of both inter and intra‐fractional variation, facilitating the determination of treatment uncertainties and improving the delineation of tumor volume at any stage in the radiation treatment delivery process. This study demonstrates the field of view (FOV) of various PET ring axial gaps, the sensitivity of each system for each gap, and the image quality as a function of scan time and activity for one specified design. Method and Materials: Investigation of FOV and sensitivity of each design was accomplished via Monte Carlo simulations with GATE, the Geant4 Application for Emission Tomography. Image quality was investigated with a fully 3D OSEM iterative reconstruction algorithm for noiseless data to investigate the FOV and noisy data to investigate the scan time at a specified activity. Results: Even when the axial gap (G) exceeded the axial width (W) for each open ring system as in the extreme case of G = 600 mm (required to avoid actuators holding MLC's) the axial FOV was approximately 200 mm. A continuous axial and transaxial FOV (determined by PET ring diameter) of 360 mm and 450 mm respectively resulted from G=W=120mm. Reconstructed NEMA 2001 phantom images for activity of 15 mCi/70kg and scan times ranging from 10 to 100 seconds was demonstrated without the effect of attenuation, scatter, and random events. `Conclusion: For tomotherapy treatment 200 mm continuous FOV axially was sufficient and was achievable with all gaps simulated in the range from 120 mm to 600 mm. Open dual ring on‐board PET has the potential to acquire images within the time limit of a tomotherapy treatment session.
MO‐E‐204B‐03: Characterizing the Scattered Radiation from a C‐Arm Fluoroscope
Authors: Schippers D , Bichay T
Published: August 2010

Purpose: Fluoroscopic procedures result in staff exposure from scattered radiation and are a radiation safety concern. Our purpose is to investigate the intensity and mean energy of this scattered radiation. The intent is to use the results to guide staff in the choice of preferred position relative to the patient and in the choice of protective clothing. Method and Materials: A C‐arm fluoroscope was positioned to image the abdomen and pelvis of a RANDO phantom. The technique factors were initially established by the automatic exposure system, then fixed to allow for multiple measurements of scattered radiation and beam energy. The technique factors were maintained at 70 kVp and 5.4 mA for all measurements. Detailed measurements were performed with the beam positioned posterior to anterior with an additional set of measurements performed in the anterior to posterior orientation. Radiation exposure was measured at various distances and angles from the phantom. The mean energy of the scattered radiation was also determined at several locations and C‐arm orientations. Results: The intensity of scattered radiation is a function of both distance and angle of measurement relative to the phantom. The intensity in the long‐axis direction of the phantom, even for equal distance from the x‐ray field, is significantly less than the intensity at the phantom's side. The intensity also depends upon the orientation of the x‐ray tube. Scattered radiation, measured at the operator's eye level, is approximately five times greater when the x‐ray tube is positioned above the patient versus below the patient. The mean energy of the scattered radiation varied very little. Conclusion: Radiation scatter about the patient during fluoroscopic procedures is not isotropic. Staff would receive reduced dose if positioned in the cranial‐caudal direction as opposed to the lateral direction. The energy of the scattered beam was largely independent of scatter direction.
MO‐E‐204B‐08: How Well Do Effective Doses Predict Carcinogenic Risks in Body CT?
Authors: He W , Huda W
Published: August 2010

Purpose: To compare the radiation‐induced cancer risks per unit effective dose for five types of body CT scans. Method and Materials: CT examinations investigated were chest, abdominal, pelvic, abdomen/pelvis and chest/abdomen/pelvis. Effective doses and organ doses were obtained using ImPACT CT Patient Dosimetry Calculator (version 1.0). Organ doses were converted into gender and age‐dependent patient carcinogenic risks using data in BEIR VII. Values of cancer incidence risk per unit effective dose (mSv) were obtained for males and females ranging from 20 to 80 year old. Results: For males, the highest cancer risk was 14 per 100,000 people per mSv for 20 year olds undergoing pelvic CT, and the lowest risk was 1.2 per 100,000 people per mSv for 80 year olds undergoing chest CT. For females, the highest cancer risk was 17 per 100,000 people per mSv for 20 year olds undergoing chest CT, and the lowest risk was 1.4 per 100,000 people per mSv for 80 year olds undergoing abdominal CT. The age‐averaged value (± Standard Deviation) of the ratio of the highest to lowest risk per mSv for males and females were 2.8 ± 0.2 and 2.2 ± 0.2, respectively. The average carcinogenic risk for females per mSv was about 23% higher than that for males. Increasing the patient age from 20 to 80 reduced the radiation risk by nearly a factor of five for males, and nearly a factor of six for females. Conclusion: For the same effective doses in body CT, the risk to any individual patient can vary by up to 300%. Patient age is much more important for determining patient risk than patient sex.
MO‐E‐204B‐09: A Method to Evaluate the Effect of Automatic Brightness Control Tracking on Image Quality and Patient Dose for Interventional Fluoroscopic Systems
Authors: Dohatcu A , Bednarek D
Published: August 2010

Purpose: Automatic‐brightness‐control (ABC) tracking is used to maintain a constant image‐receptor signal independent of changes in the attenuation of the patient. The manner of tracking impacts image quality as well as patient dose. We have developed a procedure to evaluate the effect of the ABC‐operation logic on both dose and contrast‐signal‐to‐noise ratio (CSNR) for interventional‐ fluoroscopic systems. Method and Materials: Two vascular‐angiography systems, one with an image intensifier (II) and the other with a flat‐panel detector (FPD), were used for assessment of the testing procedure. A phantom insert containing iodine‐filled disks was sandwiched within a variable‐thickness, uniform PMMA phantom. The variation of contrast visibility and patient dose was assessed as the ABC system automatically adjusted technique parameters to compensate for changes in phantom thickness. The x‐ray techniques, filter selected by the system, acquisition rate, patient entrance exposure and detector input exposure were recorded as a function of phantom thickness. The CSNR and CSNR per entrance exposure were plotted as a function of phantom thickness for all fluoroscopic modes. Results: All systems and modes had a decrease in CSNR and an increase in dose with patient thickness, but different modes resulted in different rates of change due to the manner of mAs and kVp selection. Although noise varied between fluoroscopy modes for the II and FPD, it was almost constant for a given mode as a function of thickness since the ABC tries to maintain a constant detector exposure rate. Conclusion: The method is easy to implement with a standard phantom and is an important adjunct to evaluate ABC system performance and to allow inter‐system comparisons. Understanding the tradeoffs between patient dose and CSNR due to the operation of a specific ABC mode can help optimize system utilization.
MO‐FF‐A2‐06: Feasibility of Using a Multi‐Array Ion Chamber Detector for Daily QA in Protons Therapy
Authors: Poenisch F , Sahoo N , Martin C , Zhu XR , Gillin M
Published: August 2010

Purpose: Feasibility of using a multiarray detector system for daily quality assurance checks in proton therapy. Method and Materials: The daily dose output of the passive scattering beamline for one range modulator wheel (RMW) is measured at 4 different locations along the depth (proximal, center and distal to the plateau and at the end of particle range) using a 2D‐multiarray detector system (Starcheck, PTW Freiburg, Germany). Different depths were generated along the SOBP by using a dedicated compensator. The flatness and symmetry of the beam were measured by irradiating the detector using a 15×15cm2 aperture without the compensator. Results: The diagonal profiles of the high‐energy medium‐scatter RMW were measured. The central part of each profile is influenced by scatter from the thicker part of the compensator into the thin proximal area. Therefore, the average dose value is determined 50 mm from the center by averaging the readings of 8 ion chambers. The dose output is in agreement with those from the commissioning data. This QA dosimeter system has a rather good reproducibility. The maximum relative deviation from the average measured dose with this system was 2.3% for all data, except for the end of range location. By using the ICRU78‐protocol, the symmetry and flatness was determined to be 0.23±0.07% and 1.8±0.2% respectively, which are within acceptable tolerance limits for this energy. Conclusion: The Starcheck with the dedicated compensator offers several advantages over conventional single point measurement with one ionization chamber for daily QA, namely, the ability to measure the depth dose and flatness and symmetry using the same device quickly. The use of this system allows both an independent flatness and symmetry check to be performed on a daily basis without increasing the time and efficient QA checks for all the RMWs used clinically.
MO‐FF‐A3‐01: Optimization of Spot Position in Intensity Modulated Proton Therapy
Authors: Mo X , Mackie T
Published: August 2010

Purpose: To develop a method of integrating optimization of spot position into the inverse planning of intensity modulated proton therapy (IMPT), and evaluate the potential improvement of treatment plan quality, particularly in the case of limited intensity levels. Method and Materials: To obtain the optimal treatment plan with fixed discrete intensity levels, the beam weights and positions are optimized separately in an alternate manner. First, the beam weights are optimized as continuous variables and subsequently rounded to the nearest intensity levels. Then the beamlet, or spot, positions are optimized with this set of weights. This process is repeated until the plan is acceptable. The same objective function is used for both optimizations and is similar to that used in traditional IMPT. The optimization engine uses a sequential quadratic programming method. Results: The algorithm is evaluated on an ellipsoid water phantom with a spherical target at the center, treated with single field spot scanning. With 10 intensity levels, merely rounding the beam intensities to the nearest levels resulted in homogeneity index (HI = (D2%‐D98%)/Dmean) increasing from 1.31% to 10.5%. The final optimized plan achieved HI of 1.51%. With 5 intensity levels, severe under‐dosage on the PTV (D98 at 71.85% prescription dose and HI of 40.7%) is observed if only rounding the beam intensity. Our algorithm yielded a plan of HI of 5.76%. Conclusions: Incorporating the optimization of proton beamlet positions into the inverse treatment planning system of IMPT offers more flexibility. Our phantom study suggests rounding the beam intensities to the nearest levels can be acceptable with more than 10 levels. In the case of greatly limited number of intensity levels, alternately optimizing the beamlet weights and positions is a feasible solution and can achieve treatment plans of comparable uniformity and conformity to traditional IMPT with continuous intensity levels.
TU‐A‐BRA‐03: Knowledge‐Based and Patient‐Geometry Specific IMRT Treatment Planning
Authors: Wu B , Sanguineti G , Kazhdan M , Simari P , Taylor R , McNutt T
Published: August 2010

Purpose: To create an IMRT treatment planning approach by which planners can access the knowledge of prior clinical plans to control the quality of new plans. Method and Materials: Overlap volume histogram (OVH) is used to access the knowledge of prior clinical plans. It allows planners to identify a reference group of prior clinical plans that contains geometric information “similar” to a new patient. The best plan in terms of OAR sparing in the reference group will then provide input to IMRT optimization for the new patient. In a retrospective OVH‐assisted planning demonstration, 15 patients were randomly selected from a database of 91 prior head‐and‐neck patients with a three‐level prescription: 58.1 Gy, 63 Gy and 70 Gy. A leave‐one‐out methodology was applied to generate the DVHs for each OVH‐assisted plan (OP). The database‐generated DVHs were then used by a planner who had no knowledge of the clinical plans (CPs). To evaluate the effectiveness of our methodology, the dosimetric results for three sets of plans: CPs, OPs after the first‐round optimization and final OPs were compared by the Wilcoxon p test. Results: Averages of optimization rounds required for completing CPs and OPs were 27.6 and 1.9 (p<0.00001); three OPs were completed in a single optimization round. For both OPs, averages of standard deviation to the PTV63 deceased by ∼0.5 Gy (p<0.02); averages of D0.1 cc to the cord+4mm decreased by ∼6.5 Gy (p<0.0001); averages of D0.1 cc to the brainstem decreased by ∼7.5 Gy (p<0.005); averages of V(30 Gy) to the contra‐lateral parotid decreased by ∼8% (p<0.0001). Additionally, both OPs were comparable with or better than the CPs in PTV uniformity, conformity and other OAR sparing. Conclusion: The method offers a way of predicting clinically achievable doses ahead of planning, making IMRT planning no longer a trial and error process.
TU‐B‐204C‐01: Breast Specific Gamma Imaging
Authors: Stern L
Published: August 2010

Molecular Breast Imaging is a new modality for diagnosing breast cancer. Screening Mammography has vastly improved over the last 30 years, but radiologists still miss 10% of breast cancers especially in women with dense breast tissue. The use of breast ultrasound and breast MRI has definitely helped radiologists to detect additional cases of breast cancer and to evaluate the extent of breast cancer.

There now is a new different test that can be used to solve difficult or confusing cases. It also is an excellent test when MRI is not feasible or available. It is a nuclear medicine test that analyzes cellular activity. Since cancer cells are usually more active than normal cells, they usually will absorb more of the radioactive isotope producing a black (hot spot) on the image.

This lecture will explain the underlying physics of the procedure and the technique in using the machine. Examples of real cases will be used to demonstrate how this new test fits in with the more traditional methods of breast cancer detection.

Learning Objectives:

1. Understanding the physics behind Molecular Breast Imaging.

2. Understanding the clinical applications of this test.

3. Understanding how this test fits in with Mammography, Breast Ultrasound and Breast MRI.
TU‐C‐BRA‐08: Can We Ignore Angular Acceleration and Deceleration Caused by Gantry Angular Speed Modulation in Volumetric Modulated Radiation Therapy
Authors: Song Y , Obcemea C , Mueller B , Mychalczak B
Published: August 2010

Objective: VMAT optimizes both MLC apertures and MU weights simultaneously. Additionally, VMAT uses a substantially higher gantry angle sampling frequency than DAO to better model the continuously moving source. VMAT achieves a desirable intensity modulation through a synergistic combination of MLC aperture, dose rate, and gantry angular speed modulations. Unlike conventional rotational techniques, VMAT requires the gantry to accelerate and decelerate frequently to deliver a given angular dose rate (MU/degree). This could potentially become a source of dosimetric error. In this study, we investigated the potential dosimetric effects of gantry angular acceleration and deceleration in VMAT delivery. Materials and Methods: A commercial phantom, MapPHAN with MapCHECK, was scanned on a CT scanner with a slice thickness of 3 mm and a matrix size of 512×512. The acquired CT images were transferred to our in‐house VMAT TPS for treatment planning. A VMAT plan with 180 control points and 360° gantry rotation was computed. On a Varian Trilogy CLINAC, the VMAT plan was delivered to the phantom six times with six different maximum dose rates: 600, 500, 400, 300, 200, and 100 MU/min, respectively. The measured dose distribution with 600 MU/min was used as the baseline for comparison purpose. Results: We found that there were observable dose differences in the dose map between the measured dose distributions for 600 MU/min and 100 MU/min. These dose discrepancies covered an extensive area, but were mainly concentrated in the PTV, i.e., in the high dose and high dose gradient regions. The dose differences ranged from –2 ∼ 6 cGy. Conclusions: For a few fractions, this difference may be trivial. But for dose escalation cases, the accumulative dose differences could be significant and should not be ignored.
TU‐C‐BRA‐10: Non‐Voxel‐Based‐Broad‐Beam (NVBB) Framework for EMRT Treatment Planning — III. Ultra‐Fast Full Dose Calculation
Authors: Chen Q , Chen M , Olivera G , Lu W
Published: August 2010

Purpose: Dose calculation is essential in treatment planning in radiation therapy. Collapsed Cone Convolution/superposition (CCCS) based dose calculation is regarded as clinical standard in terms of accuracy. It is essential to run a CCCS based dose calculation before accept the plan. Our main objective is to develop an ultrafast GPU‐based CCCS dose calculation engine capable of performing near real‐time dose calculation with a single PC. Method and Materials: The dose calculation engine in commercial TomoTherapy® system is re‐implemented using NVIDIA's CUDA language. In order to fully unleash the power of GPU, algorithms are modified to better suit the GPU architecture. A non‐voxel based ray‐tracing algorithm is used for TERMA calculation to avoid write‐conflicts and utilize GPU's free texture interpolation. An exponential dose kernel model is used for CCCS calculation that reduces the computation by over 100. Efforts are made to ensure the coalesced memory access throughout calculation. Results: The GPU dose engine running on a single NVIDIA GTX‐295 card is compared with the original commercial version running on a CPU cluster for both performance and accuracy. Extensive tests were run that includes different delivery modes (TomoHelicalSM, TomoDirectSM) and different disease sites on either patient CT or Tomo® cheese‐phantom. The GPU algorithm on one GTX‐295 is 8–16 times faster than original dose engine running on a 14‐blade (consists of 28 dual‐core Xeon5148 2.33GHz CPUs) TomoTherapy® high‐performance cluster. This translates to a speedup of 200‐400 over a single Xeon5148 CPU. The new GPU dose engine produces doses that are within 1%, 1 mm of original dose engine. It is also within 3% of the ion chamber and film measurement, passing all verification tests. Conclusion: We developed an ultrafast GPU‐based CCCS dose engine. Compared with the current cluster based commercial product, performance gains and accuracy verification are demonstrated.
TU‐D‐201B‐03: The Latest in Radiation Dose Reduction Techniques in CT
Authors: McCollough C , Yu L , Leng S , Kofler J
Published: August 2010

The dose per exam for a CT of the abdomen and pelvis has decreased by a factor of 2–3 since the 1980s due to a number of technical innovations. This was accomplished in parallel to scan times being reduced from several minutes to several seconds and routine image thicknesses being decreased from 10 mm to 3 – 5 mm. Some of the advances responsible for these improvements included: use of solid‐state scintillating detectors and electronic circuits with lower levels of “background” noise, wider multiple‐detector‐row arrays having thin individual detector elements, more powerful x‐ray tubes and generators which allow greater pre‐patient “beam‐hardening,” and beam shaping filters that vary decrease intensity to the patient periphery or restrict the majority of the dose to the center of the patient for cardiac imaging. A number of additional dose reduction techniques now exist and are gaining wide‐spread use, including automated adjustment of scanner output according to patient size, tube current modulation based on patient attenuation or ECG, automated selection of the most dose‐efficient tube potential, iterative reconstruction methods, increased spiral pitch or non‐spiral cardiac CT acquisition modes, dynamic z‐axis collimation, and novel noise reduction techniques, some of which require raw data and some of which operate on reconstructed images.

This presentation will provide an overview of CT dose reduction techniques, emphasizing those with the greatest clinical impact, and new and emerging techniques. The participant will learn about the general classes of CT dose reduction techniques, and examples of specific implementations will be given.

Learning Objectives:

1. Recognize the general classes of dose reduction techniques in CT

2. Understand the basic principles of each general class

3. Learn how specific implementations of each class function

4. Appreciate the magnitude of dose reduction that can be achieved using the described techniques
TU‐D‐201C‐03: Monitoring Cancer Treatment with Contrast‐enhanced Ultrasound Imaging
Authors: Sehgal CM
Published: August 2010

There is growing interest in evaluating cancer therapies that target tumor vasculature. However, assessing these therapies has been difficult because the conventional approach of measuring tumor size does not indicate microvascular activity. Furthermore, cancer microvessels re‐grow between treatments, requiring continual evaluation during the course of therapy.

The goal of our studies is to develop techniques that allow longitudinal imaging of tumor microvascular flow. Towards this goal, techniques that employ Doppler or grayscale ultrasound with microbubble contrast agent to visualize blood flow through microvessels will be presented. The metrics used for evaluating vascular changes induced by vascular targeting therapies will be reviewed and their efficacy demonstrated in mice tumors. The antivascular action (decrease in tumor microvascular flow) of three different treatments (combretastatin, ionizing radiation and sonication) will be discussed.

Before antivascular therapy, contrast agent perfusing vascular tumors is seen in the images as a uniform flush of color filling the entire lesion. After treatment, the images show that contrast medium does not enter several regions of the tumor, indicating that these parts of the tumor are now avascular. The decrease in area enhanced by the contrast agent and the rate of inflow of contrast agent in the image plane are useful endpoints for assessing cancer treatments affecting tumor microvascular flow.

Learning Objectives:

1. Understand the techniques of contrast‐enhanced ultrasound imaging

2. Understand the issues related to microbubble disruption and ultrasound exposure

3. Understand the issues associated with the use of contrast‐enhanced imaging for monitoring vascular targeted therapies
TU‐E‐BRA‐01: Optimizing MR Imaging for Treatment Planning
Authors: Brock K , Jackson E , Mayr N
Published: August 2010

The integration of MR imaging into the treatment planning process has provided the ability to improve the identification of tumor boundaries, soft tissue interfaces, organ functioning, and tumor and normal tissue motion. Selecting and optimizing the MR imaging sequence is challenging. Sub‐optimal imaging sequences may reduce the efficacy of the MR images or increase the time required to obtain the images. Research has been underway to optimize these sequences and adapt sequences developed in diagnostic MR imaging for radiotherapy requirements. MR contrast techniques, the optimization of SNR and slice thickness, and the evaluation of differences between commonly used sequences and techniques will be presented for anatomical imaging. Functional imaging for tumors and normal tissues will be discussed, including optimizing time and resolution and the trade‐offs that must be made between them. For MR imaging of tumor and normal tissue motion, different cine imaging techniques will be presented as well as the optimization of frequency and resolution in these techniques.

The Learning Objectives include:

1. Understand techniques and sequences used for anatomical imaging, including tumor definition, contrast enhancement, and organ identification.

2. Explore techniques to perform functional imaging to evaluate tumor and normal tissue capabilities for integration into treatment planning.

3. Understand techniques to optimize speed of imaging and cine sequences for evaluating tumor and normal tissue motion. Both 2D and 3D sequences will be discussed.
WE‐D‐204B‐02: Correlated 3D Respiratory Motion Prediction with Low‐Dimensional Feature‐Based Learning
Authors: Ruan D , Keall P
Published: August 2010

Purpose: Current methods of respiratory motion prediction treat each dimension independently. In this study we develop and investigate a low dimensional inference methodology that takes advantage of the correlative relation among various physical dimensions for respiratory motion prediction. Method and Materials: Covariate‐response training pairs are constructed in the original 3D physical space, via state augmentation. Unlike existing methods where independent inference models are built for each of the x,y,z coordinates, we first map these high dimensional paired samples into a lower dimensional feature space, spanned by the principle components. In this feature space, a Gaussian kernel with block‐diagonal covariance is employed for learning the joint covariate‐response pdf, which upon marginalization yields the distribution for the projected prediction value. Finally, the estimate in the feature space is mapped back into the original physical space to recover the prediction representation in the (x,y,z) coordinate. The proposed method is compared against its counterpart with independent prediction, using 159 lung motion traces from the Synchrony respiratory tracking system. Both methods were tested for predicting 160ms and 570ms, spanning the range of measured DMLC tracing system latencies. Performance is quantified with 3D RMSE and 90% percentile 3D error. Results: Under fair setup conditions, the proposed method achieves better performance than its independent counterpart. The case‐wise 3D RMSE was reduced by 30–40%, with p‐values in the order of 10̂(−14) for both lookahead lengths. The 90% percentile 3D error was reduced from 1.8mm to 1.1mm for 160ms prediction and from 2.8mm to 2.0mm for 570ms prediction. Conclusion: We have proposed a general low dimensional feature learning methodology to perform correlated high dimensional inference. Combining it with the already effective kernel density estimation yields a highly efficient approach for real‐time respiratory motion prediction. Research supported by NIH/NCI R01 93626, Varian Medical Systems, and AAPM Research Seed Funding initiative.
WE‐E‐203‐01: One Model for Teaching Clinical Skills to Medical Physics Master's Degree Students: Employing a Clinical Skills Workbook as Part of a Structured Clinical Practicum Course
Authors: Smajo ME , Markovic A
Published: August 2010

Purpose: To present one model for teaching clinical skills to medical physics master's degree students: employing a clinical skills workbook as part of a structured practicum course. Method and Materials: By creating a workbook and accompanying practicum course structure, our goal is to provide a framework for improved learning of medical physics skills in practice. Each workbook section begins with selected references. Included exercises seek to empower the students to think deeply and critically by guiding them through a series of tasks and detailed questions. This encourages them to understand the rationales behind medical physics procedures and to acquire the skills needed to analyze, compare, and implement new technologies. Additional structure and materials help to keep the course cohesive, relevant, and organized. A competency list is employed to track student progress over time. Discussions between students and clinical preceptors are emphasized, and regular individual meetings of each student and preceptor with our Director of Clinical Education are required. The information obtained during these meetings allows close monitoring of student development and intervention when appropriate. Quarterly student evaluations of the course, preceptor, and clinical sites, as well as preceptor input, enable continual improvement of the workbook and course structure. Results: Feedback from students and preceptors indicates that students meet our expectation of at least two full days of practicum work per week for 6 of their 7 quarters in the program, master the majority of tasks outlined in the clinical competency list prior to graduation, achieve a good level of understanding of clinical procedures, and benefit from the enhanced structure our course provides. Conclusion: Through the use of a clinical skills workbook and structured practicum course, we seek to ensure that our students will learn to safely and appropriately practice clinical medical physics.
WE‐E‐203‐04: Development of a Web Accessible, Data Base to Facilitate Managing Medical Physics Residencies
Authors: Mayo C
Published: August 2010

Purpose: Develop software tools to facilitate managing documentation of a medical physics residency program Method and Materials: Medical physics residency programs are often carried out in busy clinics with few additional staffing resources. Creating a process that is both efficient and meets CAMPEP and university requirements for documenting the resident's entry into and progress through the program can be challenging. When the process involves faculty on multiple campuses, difficulty of the task is increased. Various tools for managing the data electronically were evaluated and a single approach converged upon. Results: Managing data using an SQL database, using web based applications (ASP.Net/C#.Net) as interfaces to the database was the preferred approach. This allowed greater flexibility than spread sheet based solutions and was more easily generalized for use by other medical physics residency programs. Initial applications were created and used to manage application materials for the residency, enable faculty to rank applications through all 4 phases of the process and aggregate statistics on the rankings to inform discussions. Additional applications are being developed to replace the spread sheet based documentation currently used to document resident progress through the program. Conclusion: Managing information on medical physics residencies with a database having a web based interface provides significant advantages for efficient use of staffing resources, facilitating reporting and aggregation of relevant statistics. A solution has been created that may be used by other institutions. Such efforts could form the basis of a unified approach among the various medical physics residency programs.
TH‐A‐202‐01: Risks in IR and Establishing a Patient Safety Program
Authors: Jones A
Published: August 2010

A patient safety program is critical to proper medical management in interventional radiology or cardiology departments. While radiation is only one part of the overall patient safety picture it is a vital and often overlooked aspect of any safety program. One of the main goals of a radiation safety program is to prevent deterministic radiation effects if possible and identify effects when they occur so appropriate medical treatment can be administered. The development of such a program requires that the physicist understands possible deterministic effects quantities used to assess the radiation dose to a patient and current practice guidelines and regulations that address radiation dose in an interventional radiology setting.

Learning Objectives:

1. Understand the quantities and methods that can be used to estimate peak skin dose;

2. Understand possible deterministic effects that can result from interventional radiology procedures;

3. Understand current practice guidelines and regulations governing patient safety in interventional radiology;

4. Learn how to set up a patient safety program including pre‐procedure intra‐procedure and post‐procedure phases.
TH‐D‐204B‐01: Theory and Applications in MR Imaging of Compressive Sensing
Authors: Goldstein T , Osher S
Published: August 2010

This talk will introduce the concept of compressed sensing (CS). We will begin with some intuitive justification for CS. Compressed sensing will then be discussed from a more rigourous perspective and theoretical results will be presented. The application of the CS theory to magnetic resonance imaging will then be discussed. Finally we shall discuss the split Bregman method ‐ a fast numerical scheme for reconstructing images from compressed sensing data.

Learning Objective:

1. Understand the basic theory of compressed sensing and the advantages it offers.

2. Understand how compressed sensing can be applied to MRI

3. Understand the computational challenges of compressed sensing and the split Bregman method for reconstructing images from compressed data.
TH‐D‐201C‐02: Rapid T1 Mapping of Myocardium and Left Ventricle Blood for Small Animals Using Saturation Recovery Look‐Locker Method
Authors: Li W , Griswold M , Yu X
Published: August 2010

Purpose: Dynamic contrast enhanced MRI (DCE‐MRI) has been increasingly used to delineate cardiac patho‐physiological conditions such as tumor and infarction. The time course of contrast agent in tissue and blood is required for quantitative analysis. However the sampling of contrast agent dynamics is challenging for small animal models because of the fast heart beat and blood circulation. Current study aims to develop and validate a rapid T1 mapping method for simultaneous quantification of myocardium and blood contrast agent concentrations in small animal DCE‐MRI studies. Method and Materials: An ECG‐triggered saturation recovery Look‐Locker (SRLL) method was developed for T1 estimation by sampling the initial portion of the longitudinal magnetization recovery curve. Monte‐Carlo simulations were conducted for error analysis and parameter optimization. Validation was performed on both phantom and mouse heart in vivo (n=7). SRLL and keyhole sampling scheme was also jointly applied in a manganese enhanced MRI experiment to show its practical utility. Results: Simulations showed that SRLL can provide accurate T1 estimation despite of heart rate fluctuation and field inhomogeneity. This was validated in both phantom and in vivo mouse heart by a strong agreement between T1 measured by SRLL and by the standard inversion recovery Look‐Locker method. The myocardium and blood T1 values were also consistent with the literature. No significant changes in SRLL measured T1 were found by the application of keyhole method. In the manganese enhanced MRI experiment T1 continuously decreased during MnCl2 injection and remained unchanged during the 15 min post infusion period. Conclusion: Our results indicate that SRLL can provide a robust measurement of myocardium and blood T1 in mice at high spatial (195×390 μm2) and temporal (3 min) resolutions. The application of keyhole can further reduce the imaging time to less than 2 min.
TH‐D‐201C‐11: Reference Image Compressed Sensing Based Dynamic Contrast Enhanced MRI
Authors: Wang H , Zhou K , Yu Y , He Q , Bao S , Hu J
Published: August 2010

Purpose: The purpose of this work is to implement the CS‐based MRI in DCE‐MRI to develop a new method that can exhibit both high temporal and high spatial resolution results which are significant for DCE‐MRI and related diagnosis. Method and Materials: By exploring the DCE specific characteristic that administration of contrast agent (CA) induces change only in image signal intensity in certain areas such as vessels and lesions no significant change in anatomical structure we have developed a novel approach Reference imAge based Compressed sEnsing (RACE) to capitalize the sparsity and compressibility of DCE‐MRI. Phantom experiments have been performed on an MAGNETOM ESSANZA 1.5T MRI scanner (Siemens Erlangen Germany)focusing on the study of temporal and spatial resolution respectively. Spatial finite difference (SPD) is chosen to be the sparse transformation. 3D radial sampling is implemented as under sampling scheme. The reconstruction is based on solving a constrained total variation (TV)‐norm minimization problem. Results: According to the phantom experiments during a same time course much more (up to 10 times) time frames can be obtained with RACE which means higher temporal resolution. The comparisons demonstrate that the details of the dynamic curves can be detected using RACE especially when the intensity varying rate is high (Fig.3 c). Meanwhile the spatial resolution is not degraded. Conclusion: This work proved that RACE which properly explored the features of DCE‐MRI can significantly improve the temporal resolution of DCE‐MRI without degrading its spatial resolution. Conflict of Interest (only if applicable): Phantom experiments are supported by Siemens Mindit Magnetic Resonance Ltd. Co.
Sci—Thur PM: YIS — 04: Aperture Superposition Algorithm for Photon Dose Calculations of Finite Size Cobalt‐60 Radiation Source for Tomotherapy Dose Deliveries
Authors: Dhanesar S , Darko J , Schreiner LJ
Published: August 2010

The finite size pencil beam (FSPB) superposition method is commonly used to calculate dose for intensity modulated beams in IMRT. The FSPB model assumes that broad beam dose from a radiation originating from a point source can be calculated by a superposition of dose from pencil beams. For finite size sources, such as a Cobalt‐60 (Co‐60) source of 2 cm diameter, this method is no longer valid. In this paper we propose an aperture superposition (AS) dose calculation method that can be used for dose calculations of intensity modulated beams from finite size radiation sources. The model is applied to fan beams, as encountered in tomotherapy, and results are compared to the FSPB model and the film measurements. The comparisons between the AS model and film measurements show agreement to 1.5% in the high dose regions and 3.7% in the low dose regions. On the other hand, film measurement comparisons to the FSPB model show that the FSPB model underestimates the dose by up to 7% for small field sizes such as 2×2cm2 and 20% for larger field sizes such as 20×2 cm2. In conclusion, the AS model provides a better accuracy than the FSPB model when calculating dose for fan beams from large radiation sources. Research is underway to extend the application of this model to broad IMRT beams obtained from non‐binary multi‐leaf collimators. The implementation of this model to the current treatment planning systems can be useful for treatment planning of Co‐60 based IMRT and tomotherapy.
Sci—Thur PM: YIS — 06: Presentation of a Novel Scintillating Fiber Fluence Monitor for the Real‐Time Verification of Advanced MLC‐Driven Radiotherapy Treatment
Authors: Goulet M , Gingras L , Beaulieu L
Published: August 2010

Purpose: To present a novel type of fluence monitoring detector based on optical attenuation for the on‐line quality control of radiotherapy treatments. Method: Long scintillating fibers were aligned along the direction of motion under each of the leaf pair of a Varian Clinac iX MLC and coupled on both ends to clear optical fibers to enable light collection. Following a theoretical model of scintillation collection based on optical attenuation, the detector performance was evaluated by 1) measuring the intrinsic variation of the readings, 2) comparing the experimental data to the expected values calculated from the treatment planning software (TPS) and 3) measuring random leaf errors introduced in an IMRT field. Results: The detector allows the measurement of the central position of the dose deposition on each fiber (xc) and the integral fluence passing through it (Φint). Very low intrinsic dispersion, dominated by Poisson statistics, was observed (under 1mm for xc and under 0.15% for Φint). When compared to the TPS, both xc and Φint) exhibited more significant deviations (respectively a mean of 1.3mm and 2.6%) due to the uncertainties on the dose calculated in regions of high perpendicular dose gradients.Φint is highly sensitive to single leaf motion errors as low as 1mm (at isocenter) while xc showed a good response to a leaf pair translation error of 2mm and more. Conclusion: This work clearly demonstrates the sensitivity and specificity of on‐line quality control of the incident fluence by a thin transmission detector based on optical attenuation of scintillating fibers.