bluuebunny/crossref_metadata_2025_split huggingface dataset:
WE‐C‐BRA‐02: Parameters for and Use of NTCP Models in the Clinic
Authors: Yorke E 
Published: July 2007

Delivery of adequate tumor dose without causing excessive normal tissue complications is the driving principle of modern radiation therapy. Resulting dose distributions in normal tissues are very different from the “partial organ irradiation” distributions that characterize the simple beam arrangements of earlier days. Further, the growing popularity of hypofractionation drastically widens the range of biological effective doses within organs at risk (OAR). The clinical physicist is faced with uncertainty as to what aspects of an OAR dose distribution require special consideration in treatment plan design and evaluation.Normal tissue complication probability (NTCP) models are one way to account for the full dose distribution. For most serious toxicities, statistical models from various outcomes analyses help direct the planner toward dose‐volume limits. There are also several semi‐mechanistic models, each with a set of parameters that must be adjusted to describe existing data. But for conditions that differ greatly from those under which they were ‘commissioned’, two models for the same endpoint and starting from the same input dose distribution do not necessarily predict the same NTCP. A working group, with joint participation from AAPM, ASTRO and RTOG, is being established to, among other things, reconcile model differences and provide clinical guidelines in the near future.In this presentation, common NTCP models for several major dose‐limiting toxicities will be described, including parameters sets gleaned from literature review. Problems and pitfalls of integrating and interpreting diverse studies and applying them to an individual clinic's practice will be discussed and real‐world examples of application to clinical decisions will be presented.Educational Objectives:1. Understand the important features of the most widely‐used NTCP models.2. Understand how the model parameters affect predictions of normal tissue dose‐volume responses.3. Understand some of the complexities of implementing these models into routine clinical practice.
WE‐D‐L100J‐07: High‐Resolution Digital Ultrasonic Thermometers
Authors: Malyarenko E , Heyman J , Chen‐Mayer H , Tosh R 
Published: July 2007

Purpose: To develop and test 1) fully digital μK‐resolution ultrasonic thermometer for non‐invasive measurements of absorbed radiation dose in water; 2) rapid ultrasonic 2D temperature mapping system for precise characterization of radiation beam intensity profiles. Method and Materials: Monitoring tiny phase shifts of ultrasonic signals in water heated by ionizing radiation allows assessing water temperature changes at the μK level. Instead of the analog frequency‐driven Pulsed Phase‐Locked Loop (PPLL) used in the earlier work to track signal phase, the current system relies on fast digital phase algorithms that extract signal delay with resolution of 100ppb and better. Another ultrasonic system was built to produce 2D temperature maps in water. This system contains a 128‐element, 14″‐diameter circular transducer array operating in a tomographic fan‐beam data acquisition mode. The system acquires temperature maps in seconds and allows monitoring evolution of thermal processes in time. Results: The single‐channel digital ultrasonic thermometer demonstrated resolution equivalent or better than analog PPLL‐based prototype at overall lower noise level. The 2D temperature mapping system was constructed and went though a preliminary testing round. It monitored evolution of temperature profile in the cylindrical tank every 3–4 seconds acquiring each time a 64‐projection data set with 45 rays per projection. After extracting phase information from the acoustic waveforms the system reconstructed a sequence of phase shift images and converted them to temperature maps using newly developed calibration procedure. The maps were combined into movies to watch temperature evolution dynamics. Conclusion: The digital high‐resolution ultrasonic thermometer demonstrated performance improvement and will replace its analog predecessor in the radiation‐testing lab. The 2D ultrasonic temperature mapping system was successfully tested with a light radiation heating source. We plan to continue characterizing its spatial and temperature resolution and incorporate all findings into a next‐generation prototype for ionizing radiation testing.Research sponsored by NIST.
WE‐D‐L100F‐01: Highly Accelerated MRI Using Undersampled Acquisition and HYPR Processing
Authors: Mistretta C , Wieben O , Velikina J , Wu Y , Johnson K , Korosec F , Fain S , Block W , Wu Y , Perry J , Keith L , Kecskemeti S , Khansa I , Wang K , Grist T , Reeder S , Lum D , Turk A , Aagard‐Kienitz B , Turski P 
Published: July 2007

During the past several years there has been a growing body of research developments that might be considered the beginning of a “Post Nyquist Era” in medical imaging. Investigators at Stanford and Cal Tech have shown that the iterative non‐Fourier reconstruction “Compressed Sensing” method can be used to reconstruct single images with far less than the required number of Nyquist samples [1,2] for image data sets that satisfy certain sparsity requirements. The recent developments in parallel imaging also permit the reconstruction of relatively artifact free images by synthesizing missing k‐space information using sensitivity profiles from multiple coils[3,4]. Our group has been investigating the use of VIPR, a vastly undersampled radial imaging technique [5,6] that almost immediately provides full spatial resolution after a small number of excitations at the expense of streak artifacts. In 3D these artifacts are quite incoherent and provide little degradation of image quality. Data undersampling factors of several hundred relative to the Nyquist criterion have been achieved. Recently VIPR has been combined with a new reconstruction method called HYPR (HighlY constrained PRojection reconstruction) [7] that exploits the spatio‐‘temporal’ redundancy in medical image sequences involving any serial change in an imaging variable such as time, echo time, diffusion tensor encoding direction, etc. Using HYPR in combination with VIPR, angular undersampling factors on the order of 1000 in phase contrast angiography have been achieved with good image quality. A fundamental characteristic of HYPR is its ability to provide higher SNR than competing acceleration technique. The HYPR technique has been applied to X‐ray CT angiography where clinically acceptable time‐resolved angiographic image series have been reconstructed using 1/46th of the conventional x‐ray dose.Educational Objectives1. To understand the advantages of 3D radial undersampling for increasing spatial and temporal resolution.2. To understand how HYPR provides further acceleration with substantial preservation of SNR.3. To understand how HYPR may be applied in a wide variety of medical imaging applications.
WE‐D‐L100F‐02: Parallel Magnetic Resonance Imaging (or, Scanners, Cell Phones, and the Surprising Guises of Modern Tomography)
Authors: Sodickson D 
Published: July 2007

Today, parallel data acquisition approaches are used widely in MRI, both for clinical diagnostic imaging and for research applications. Whereas in a traditional sequential MRI scan, data are collected one point and one line at a time in the presence of varying magnetic field gradients, parallel MRI uses spatial information from arrays of radiofrequency detector coils to acquire multiple data points simultaneously, thereby circumventing basic limits on imaging speed and efficiency associated with traditional sequential approaches. The use of RF coil information in combination with the traditional Fourier information available from field gradients increases the complexity of image reconstruction. In fact, parallel MR image reconstruction may be represented as a generalized linear inverse problem. This formulation highlights connections with other modalities as well as shedding light on both the potential and the limitations of parallel imaging. In this talk, the fundamentals of parallel MR image acquisition and reconstruction will be reviewed. Analogies with X‐ray computed tomography, MIMO wireless communication, and magnetoencephalography will be explored, and some future directions in parallel MR reconstruction algorithms, hardware design, and clinical applications will be surveyed.Educational Objectives:1. Understand the basic physical principles of parallel MR data acquisition and the basic mathematical principles of parallel MR image reconstruction.2. Recognize analogies with other imaging modalities and communication technologies.3. Identify fundamental physical (electrodynamic) limits of performance of parallel MRI systems.4. Appreciate some of the most common current and the most promising future clinical applications of parallel MRI.
WE‐D‐BRA‐02: Helical Tomotherapy Experience
Authors: Ramsey C 
Published: July 2007

Helical tomotherapy is a rotational radiation therapy delivery technique that combines pre‐treatment CT‐based image‐guidance and Intensity‐Modulated Radiation Therapy (IMRT) using a fan‐beam delivery. Helical tomotherapy treatments are delivered by a continually rotating gantry mounted on a slip ring system, which permits power and communications to be passed from the rotating to stationary sub‐systems. Treatments are delivered with both the gantry and the couch in continuous simultaneous motion. Thus, helical tomotherapy can continuously deliver intensity‐modulated radiation from 360° in a transverse plane about the patient.In addition to its ability to deliver IMRT, helical tomotherapy systems also have the ability to obtain Megavoltage CT (MVCT) images of the patient in the treatment position prior to each treatment fraction. Daily positional uncertainties and anatomical changes (such as weight loss, tumor response, etc…) can be minimized by utilizing CT‐based pre‐treatment imaging. As such, the position of the tumor relative to the treatment beam can be corrected prior to treatment by moving the patient with appropriate superior‐inferior, anterior‐posterior, lateral, pitch, roll, and/or yaw offsets.The combination of precise positioning of the target volume and the rotational nature of the delivery make helical tomotherapy well suited for simultaneously delivering differential doses to multiple targets. Treatment sites that are large in the superior‐inferior direction are easily treated with helical tomotherapy. Multiple target volumes up to meter in length can be treated in a single helical tomotherapy delivery sequence. This can be useful for treating multiple metastases throughout the body while avoiding nearby critical structures. Head and Neck patients can be treated with integrated boosts with minimal dose spillover, dumping, hot spots, or critical structure problems. Shrinking lung tumors can be treated with a simultaneous integrated volume‐adapted boost (SIVAB) that allows dose escalation to the residual tumor mass without compromising normal tissue tolerance and dose to areas at risk for microscopic tumor spread. For prostate patients that are at risk for nodal involvement, the regional lymph nodes, the seminal vesicles, and the prostate can be simultaneously targeted and treated to different doses.This lecture will provide an overview of clinical scenarios utilizing differential dose delivery with helical tomotherapy. The advantages and disadvantages of helical tomotherapy will be discussed for each clinical example.Educational Objectives:1. Provide a brief overview of the helical tomotherapy system's imaging and treatment capabilities.2. Present clinical scenarios for utilizing differential dose delivery with helical tomotherapy.3. Discuss potential applications of adaptive differential dose delivery.
WE‐E‐L100J‐01: Simulation of Tomosynthesis Mammograms with Cone Beam CT Images of Mastectomy Breast Specimens
Authors: Shaw C , Han T , Chen L , Altunbas M , Lai C , Liu X , Wang T , Yang W , Whitman G 
Published: July 2007

Purpose: To describe and discuss about a technique to simulate digital mammograms and tomosynthesis images with cone beam CT images of mastectomy breast specimens. Method and Materials: To allow x‐ray images to be simulated, cone beam breast CT images of a mastectomy breast specimen were acquired at 80 kVp and used to generate a 3‐D map of linear attenuation coefficients for mammographic x‐rays. The map was then deformed to generate a new map for a compressed breast. A software re‐projector was developed and used to compute projection images for a stationary detector and a linearly shifted x‐ray source. A special re‐projector was developed to preserve the contrast of microcalcifications (MCs). The resulting images were then used to reconstruct tomosynthesis mammograms using various reconstruction algorithms. Results: We have successively used cone beam CT images of mastectomy breast specimens to generate 3‐D maps of attenuation coefficients to model compressed breasts and to use them to simulate digital mammograms and tomosynthesis images. It was found that MCs clearly visible in cone beam CT images were not visible in regular mammograms but faintly visible in tomosynthesis images. The MCs were clearly visible in both MC enhanced mammograms and the tomosynthesis images reconstructed from them. Conclusions: Cone beam CT images may be used to model a compressed breast for simulating mammograms and tomosynthesis images. Cone beam CT images are superior to regular or tomosynthesis mammograms in depicting MCs within their resolution limit. MC enhanced re‐projection, however, could be useful in displaying the cone beam CT images with the more conventional appearances of regular and tomosynthesis mammograms while maintaining the contrast and visibility of MCs in the CT images.This work was supported in part by a research grant EB00117 from the NIH‐NIBIB and a research grant CA104759 from the NIH‐NCI.
TH‐C‐AUD‐08: Comparison of Tomotherapy Dose Distributions for 6MV X‐Rays and Different Cobalt‐60 Source Designs Using Monte Carlo Methods
Authors: Joshi Chandra P , Darko Johnson , Dhanesar Sandeep K , Vidyasagar P B , Schreiner L John 
Published: July 2007

Purpose: To investigate intensity modulated dose distributions for Co‐60 based tomotherapy with cylindrical and rectangular shaped source geometries for a typical head and neck case using Monte Carlo (MC) methods. Method and Materials: EGSnrc/BEAMnrc MC code has been used to model three Co‐60 tomotherapy units and a 6 MV (Varian 2100EX) unit. Two of the Co‐60 units, consisting of modified collimator systems with customized binary multi‐leaf collimator (BMLC) were modeled for 3 and 5 cm long rectangular sources and SADs of 70 and 80 cm, respectively. The other units were a conventional Co‐60 unit (T780c) with 2 cm diameter cylindrical source (MDS Nordion, Canada) and a 6 MV Linac with an addon MIMiC BMLC (NOMOS, USA). All the Co‐60 sources had identical active volumes.EGSnrc/DOSXYZnrc MC code was used to calculate the intensity modulated beamlets and fan beam dose profiles in a water phantom. The intensity modulated energy fluence profiles from a 6 MV Linac and two Co‐60 units using the same beam segments will be compared. Tomotherapy treatment plans for a typical H&N case were calculated. All plans were optimized for PTV, two neck nodes and the spinal cord using the same optimization parameters. The treatment planning was provided by an in‐house inverse planning system based on a multi‐objective gradient‐search approach using MC calculated dose data. Results: Comparisons of optimized dose distributions, dose difference maps and dose area histogram will be presented. Despite significant differences in fluence profiles for Co‐60 and 6 MV beams, optimized dose distribution for all plans met the dose‐volume and tolerance criteria. However, the integral doses are potentially higher for Co‐60 plans particularly with longer source size and shorter SAD. Conclusions: Co‐60 based tomotherapy with appropriate source and BMLC design is dosimetrically viable.Research supported (in‐kind) by MDS Nordion, Canada.
TH‐D‐L100F‐01: Who's Minding the Dose?
Authors: Frush D , Boone J , McNitt‐Gray M , Cody D 
Published: July 2007

This three‐part symposium will provide an update on the important topic of CT radiation dose, which continues to receive increased scrutiny from a growing proportion of the medical field.The first talk is entitled “Radiation dose considerations in pediatric CT imaging,” and will be delivered by Dr. Donald Frush, an eminent expert in pediatric radiology. There are unique considerations when performing CT in infants and children. These considerations include the sensitivity of children to radiation, radiation dose exposure and dose assessment for this technology. The special technical considerations make pediatric CT in many ways more demanding than in adults. Accurate dose assessment is important for determining potential risks essential for the risk‐benefit ratio in this younger population.The second talk is entitled “CT measurements: The good, the bad, and the ugly,” and will be delivered by Dr. John Boone, an esteemed medical physicist. The theory behind the current method for assessing radiation dose in CT (the CT dose index) will be reviewed. This method has many positive features (“the good”), and a growing number of limitations (“the bad”). Several groups have been formed to develop a different approach to assessing CT radiation dose, and many issues must be carefully considered (“the ugly”. Dr. Boone will provide his perspective on these and other interesting developments in the area of CT dose assessment.The third talk is entitled “Custom patient‐based CT radiation dose estimations,” and will be delivered by Dr. Michael McNitt‐Gray, also an esteemed medical physicist. An approach that appears to be gaining in popularity for CT patient dose estimation is the use of computer models and scan simulations. This type of methodology requires a substantial investment in program development, but can result in a very flexible approach for exploring alternative technique design strategies. The use of computer modeling may find a more widespread role in CT dose assessment in the future, so it is important to understand its limitations in addition to its advantages.
TH‐D‐M100F‐03: A PET Head and Neck Tumor Delineation Approach Based On Adaptive Region‐Growing and Dual‐Front Active Contours
Authors: Li H , Thorstad W , Biehl K , Laforest R , Donnelly E , Low D , Lu W 
Published: July 2007

Purpose: To present a novel, semi‐automatic hybrid method for PET tumor delineation utilizing adaptive region‐growing and dual‐front active contours. Method and Materials: The process begins when an experienced radiation oncologist manually draws a rough region of interest (ROI) that encloses a tumor. The image voxel having the highest intensity is chosen as a seed point. A region growing algorithm successively appends to the seed point all neighboring voxels whose intensities >= T% of the mean of the current region, which is updated after each voxel is added. When T varies from 100 to 0, the resulting volumes increase from a small region to the entire rough ROI. With this criterion, a sharp volume increase has been observed at certain T values. The process uses the sharp increases as landmarks that are used to define the image intensity level that is used to define the tumor boundary.However, the tumor volume is found to be slightly larger than the anatomically defined volume possibly due to the partial volume effect. Therefore, we use a dual‐front active contour model to refine it automatically. We assign all points on the initial tumor boundary one label, and the seed point another label. Then we propagate the labeled boundaries towards each other. The evolution stops at meeting points that form the final tumor boundary. Results: A cylindrical phantom with seven hollow spheres of varying size (8–32mm) was constructed and scanned using a Siemens PET scanner under 12 various conditions. The method was tested on these 84 images with errors of volume overlap metric of 57.4% to 99.0% between the detected volumes and the actual volumes. Conclusion: This hybrid method guarantees a reproducible result for a specific image. Experimental results demonstrate the robustness, accuracy, reproducibility, and its potential usefulness in clinical radiation therapy planning.
TH‐D‐M100F‐05: Online Region‐Of‐Interest Delineation of Daily Head and Neck Images
Authors: Zhang T , Chi Y , Drake D , Yan D , Meldolesi E 
Published: July 2007

Purpose: Online imaging modalities, such as cone beam computed tomography (CBCT) or CT on‐rail provide online volumetric images. A fast, automatic and robust region‐of‐interest (ROI) delineation method is highly desired in image guided radiation therapy (IGRT). We have developed such a method and tested it via segmentation of head and neck (HN) fan beam CT and CBCT images. Material and Methods: ROIs on planning CT images were manually delineated using commercial treatment planning system. A variational‐based deformable image registration algorithm was implemented to register planning CT images to daily CT images. ROIs on planning CT images were automatically mapped to daily images using voxel matching information between planning and daily image datasets. The results were quantitatively and qualitatively validated by comparing to manual delineation. In order to accelerate computing speed, we paralleled the algorithm using message passing interface (MPI) on a Beowulf cluster with 16 processing elements (PE). Speed improvement was benchmarked. Results: The discrepancies between automatically and manually delineated ROIs on fan beam images were mostly within 2mm. Automatic segmentation of CBCT images was acceptable by visual inspection. Benchmark results showed that paralleling efficiencies were above 95% and speedup factors were approximately equal to the number of PE used. With 16 PEs online delineation of HN images took about 1 minute. Conclusion: The online ROI delineation method we have developed is robust, fast and is suitable for HN online adaptive radiation treatments.This research was partially supported by the Department of Defense Prostate Cancer Research Program under award number W81XWH‐07‐0083.