Baoshe Zhang

Continuous liquid crystal pretilt control through textured substrates

Reliable control on the pretilt alignment of nematic liquid crystal (LC) in the 30°–50° range is a well-known challenge. An unconventional approach, involving microtextured surfaces with domains favoring dissimilar LC alignments, has recently demonstrated applicability in bi- and tristable displays. These textured domains realize the so-called frustrated boundary condition in which the LC elastic energy built-up (frustration) can drive the LC alignment into macroscopic uniformity. Here we show that one can harness the frustrated boundary to achieve variable LC pretilt control up to 40°.

Preliminary design of FTS-2: an imaging Fourier transform spectrometer for SCUBA-2

We present the preliminary design of FTS-2, an imaging Fourier transform spectrometer (IFTS) for use with SCUBA-2, the second generation, wide-field, submillimetre camera currently under development for the James Clerk Maxwell Telescope (JCMT). This system, which is planned for operation at the start of 2007, will provide simultaneous broadband spectral imaging across both the 850 and 450 μm bands with variable resolution ranging from resolving powers of R ~10 to 5000. The spectrometer uses a folded Mach-Zehnder configuration and novel intensity beam dividers. The mechanical and optical design of FTS-2 as of the Critical Design Review stage of the project are discussed, along with the interfaces with SCUBA-2 and the JCMT.

Performance evaluation of the Herschel/SPIRE instrument flight model imaging Fourier transform spectrometer

The Spectral and Photometric Imaging Receiver (SPIRE) is one of three scientific instruments onboard the European Space Agency (ESA)s Herschel Space Observatory. The low to medium resolution spectroscopic capability of SPIRE is provided by an imaging Fourier transformspectrometer of the Mach-Zehnder configuration. Instrument performance of the SPIRE flight model was evaluated during a series of test campaigns. The SPIRE instrument performance verification was completed with instrument delivery to ESA in early 2007. In this paper we present the resulting performance characteristics of the SPIRE spectrometer flight model as determined from these test campaigns. We verify the instruments conformance with fundamental design specifications such as spectral coverage and resolution. Variations across the imaging array of such properties as spectral resolution, vignetting, and instrumental line shape are explored. Additionally, instrumental artefacts observed during final verification testing are identified and quantified; with explanations provided for potential causes, and proposed methods to minimize their impact on scientific observations described.

Automated compromised right lung segmentation method using a robust atlas-based active volume model with sparse shape composition prior in CT

To resolve challenges in image segmentation in oncologic patients with severely compromised lung, we propose an automated right lung segmentation framework that uses a robust, atlas-based active volume model with a sparse shape composition prior. The robust atlas is achieved by combining the atlas with the output of sparse shape composition. Thoracic computed tomography images (n=38) from patients with lung tumors were collected. The right lung in each scan was manually segmented to build a reference training dataset against which the performance of the automated segmentation method was assessed. The quantitative results of this proposed segmentation method with sparse shape composition achieved mean Dice similarity coefficient (DSC) of (0.72, 0.81) with 95% CI, mean accuracy (ACC) of (0.97, 0.98) with 95% CI, and mean relative error (RE) of (0.46, 0.74) with 95% CI. Both qualitative and quantitative comparisons suggest that this proposed method can achieve better segmentation accuracy with less variance than other atlas-based segmentation methods in the compromised lung segmentation.

Integration and testing of FTS-2 : an imaging Fourier transform spectrometer for SCUBA-2

FTS-2 is an imaging Fourier transform spectrometer (IFTS) being developed for use with SCUBA-2, the second generation, wide-field, submillimetre camera which will operate at the James Clerk Maxwell Telescope (JCMT). The FTS-2 interferometer uses a folded Mach-Zehnder configuration and will provide simultaneous broadband spectral imaging across both the 850 and 450 μm bands with variable resolution ranging from resolving powers of R ~10 to 5000. Details of the instrument design, optical modeling, data reduction pipeline and calibration plan which have changed since the project CDR are discussed, along with preliminary results of lab integration and testing.

Efficient deformable model with sparse shape composition prior on compromised right lung segmentation in CT

We developed an automated lung segmentation method, which uses deformable model with sparse shape composition prior for patients with compromised lung volumes with severe pathologies in CT. Fifteen thoracic computed tomography scans for patients with lung tumors were collected and reference lung ROIs in each scan was manually segmented to assess the performance of the method. First, sparse shape composition model is constructed using training dataset. Next, the deformable model with SSC prior will be initialized according to the rough segmented right lung ROI. Then, the right lung with compromised lung volumes is segmented using the robust deformable model. Energy terms from ROI edge potential and interior ROI region based potential are combined in this model for accurate and robust segmentation. The quantitative results of our segmentation method achieved mean dice score of (0.86, 0.97) with 95% CI, mean accuracy of (0.93, 0.98) with 95% CI, and mean relative error of (0.07, 0.17) with 95% CI. The qualitative and quantitative comparisons show that our proposed method can achieve better segmentation accuracy with less variance compared with a robust active shape model method (RASM). The proposed method will be useful in radiotherapy assessment in thoracic computed tomography and image analysis applications for lung nodule or lung cancer diagnosis.

Designing and Implementing a Computing Framework for Image-Guided Radiation Therapy Research

Research computing in radiation therapy is transitioning from small-scale computing to large software systems. Accelerator-mounted imaging devices collect multiple images at every treatment fraction, creating datasets of hundreds of images per patient. Compounding this challenge is the fact that software infrastructure upgrades are difficult to manage in academic environments, due to inadequate experience in large-scale software development.

SU‐GG‐T‐261: An Integrated Software Environment for Image Guided Adaptive Radiation Therapy Research

Purpose: Modern research in Image Guided Adaptive Radiation Therapy (IGART) generates very large quantities of imaging data, as it is no longer uncommon to collect upwards of 200GBytes of imaging data, stored as thousands of files, per research patient. Such proliferation of data requires new software infrastructure which can handle collection, anonymization, indexing and automated processing of data. Software infrastructure, in support of NIH sponsored research program on IGART, had to be developed, ab initio, at our institution. Materials and Methods: Patient data is initially collected by networked Personal Computers provided by vendors of imaging equipment. Disk synchronization software is used to create a UNIX disk mirror of data bearing disks, which is hosted on EMC Clariion networked storage devices supported by the university computing group. Automated Patient Accumulator (APA) application extracts data from the mirror, accumulates data for selected patients, and performs initial tests of data integrity. Automated Database Builder (ADB) application monitors accumulated data, creates anonymized copy of newly acquired data, and organizes anonymized data into the Reference Data Database (RDD). A customized interface to Philips Pinnacle Treatment Planning System (TPS) supports dynamic building of TPS patients from RDD images, as well as saving of image segmentation and treatment planning data back into the RDD. A dedicated C++ library, called Research Computing Framework (RCF), supports programmatic access to RDD data, building of automated data processing pipelines, and storage of derived research data into temporary research databases. Data visualization is based on the AVS Express toolkit, combined with the RCF library as means of converting research data types into AVS data types. Results: A comprehensive software infrastructure to support IGART research has been built, ab initio, at our institution. This infrastructure is currently being used to perform IGART research. Acknowledgments: Supported by NIH Grant P01 CA11602

SU‐E‐T‐32: An Integrated IGART Planning Environment

Purpose: Open Radiological Archiving and Communication System(ORACS) relational research database, which stores images, projections, plans, trials and doses etc, is the backbone for Image Guided Adaptive Radiation Therapy (IGART) Research Project at VCU. Philips Pinnacle3 is being used by this project for IGART adaptive planning of Virtual Clinical Trials (VCT). Therefore, in order to establish a user‐friendly interactive environment and facilitate collaboration between different sub‐projects, seamless integration of these two systems will be a must. Methods: It is well‐known that Pinnacle3 lacks the capacity to interact with a database server. However, we take advantage of Pinnacles configurability and scripting power to enhance Pinnacle with new GUI controls, which invoke a middleware layer to access ORACS database. Users can import images from ORACS database through remote web services or locally, and save contours and plans and doses and other derived Pinnacle data back to ORACS database by simply clicking these new GUI controls. Moreover, a Pinnacle database can be re‐created easily and entirely from ORACS database through these new GUI controls and the middleware layer. The same technique can be used to create connection between Pinnacle3 and other database servers. Also because ORACS database uses web services for data access, if a specific middleware is created, any Treatment Planning System can access ORACS database interactively. Results: We presented a software infrastructure for seamless integration of ORACS research database and Philips Pinnacle3, which created an integrated virtual clinical trial environment for IGART researchers at our institution. Conclusions: Contemporary IGART research imposes new demands on the IT infrastructure of Radiation Oncology departments. We created a data management system which takes first steps towards managing new and complex tasks of automated analysis of large data sets. NIH Grant P01 CA11602

SU‐E‐T‐278: Volume Based Comparison of Deformable Image Registration Algorithms Using Spatial Discrepancy Volume Histograms

Purpose: Accurate Deformable Image Registration (DIR) algorithms are essential to clinical implementation of adaptive planning strategies hence finding validation strategies for DIR algorithms remains a pressing concern. Most validation efforts are based on contour or landmark tracking, thus sampling the Deformable Vector Field (DVF) relatively sparsely. The primary purpose of this work is to assess interchangeability of DIR algorithms in dose accumulation, and assess if contour based methods are sufficient to validate the equivalence of DIR algorithms. Methods: We registered peak inhale and peak exhale phases of thirteen lung patients using three DIR algorithms. The DVF maps were pairwise compared through voxel‐by‐voxel subtraction of vector fields. The vector difference maps were analyzed by building volume histograms on regions of interest. This method of analysis is directly relevant to the Dose Volume Histogram accumulation, as vector difference between the maps will be translated into a distance between dose interpolation points. We further compared Jacobian distributions for the three maps, as local derivatives of DVF maps would be important to any algorithm that attempts local density corrections. We performed contour based comparison of the three algorithms, to connect this validation method to prior work. Results: The volume histogram analysis shows that differences between DVFs in 2% tails of volume histogram are in the 1cm – 4cm range, although the contour‐based analysis using Dices Similarity Coefficient (DSC) would suggest that the three algorithms are nearly equivalent. For most structures, spatial differences between maps are below 0.5cm over approximately 70% of structure volume, and exceed 0.5cm over the remainder. Jacobian distributions differ significantly, implying that local density corrections are strongly algorithm dependent. Conclusions: Differences between algorithms are potentially significant for dose accumulation, and such differences are not revealed by contour based comparisons. Acknowledgments: Supported by NIH Grant P01 CA11602