Jennifer Xu and coauthors were awarded this year’s Sylvia and Moses Greenfield Award for the Best Paper in Medical Physics. Her paper, entitled “Cascaded systems analysis of photon counting detectors,” reports an analytical model for the imaging performance of x-ray photon counting detectors. The research extends analytical models that have been important to the development and application of (energy-integrating) flat-panel detectors to account for important characteristics of photon counters, such as the pulse height threshold and possible charge sharing effects. The work also quantifies the conditions for which photon counting detectors are expected to provide greatest benefit to imaging performance in comparison to conventional flat-panel detectors. The research was supported by that National Institutes of Health and supervised by Dr. Jeff Siewerdsen in collaboration with scientists at Philips Healthcare. Coauthors are W. Zbijewski, G. Gang, J. W. Stayman, K. Taguchi, M. Lundqvist, E. Fredenberg, J. A. Carrino, and J. H. Siewerdsen. Congratulations to Jen and coauthors on this outstanding achievement!
The I-STARs head to Barcelona for the 29th Annual CARS Meeting on Computer-Assisted Radiology and Surgery. The program includes four talks from the I-STAR Lab on topics ranging from imaging of TBI to systems for safer surgery, including new technical breakthroughs in cone-beam CT and ultrasound imaging.
Alejandro Sisniega, Postdoctoral Fellow in Biomedical Engineering at Hopkins, returns to his home country to present the development of a cone-beam CT system dedicated to high-quality imaging of traumatic brain injury (TBI) and intracranial hemorrhage (ICH). The system was designed from first principles of task-based image quality to provide performance optimal to ICH detection and combines cutting-edge systems for high-fidelity artifacts correction and model-based image reconstruction. (program)
Wojciech Zbijewski, Faculty Research Associate in Biomedical Engineering at Hopkins, presents new work in high-resolution orthopaedics imaging, extending a previously reported system for extremities cone-beam CT to include advanced model-based image reconstruction and a new scanner design in development to allow quantitative assessment of trabecular micro-architecture. Such work opens new possibilities for image-based biomarkers of early osteoarthritis by detecting subtle morphological precursors to cartilage and joint degeneration. (program)
Eugenio Marinetto, PhD Student at Universidad Carlos III and Johns Hopkins University, reports the integration of C-arm cone-beam CT and ultrasound imaging for surgical guidance. Eugenio’s work includes the characterization of imaging performance of a low-cost ultrasound probe, its integration with the TREK surgical guidance system, and registration with mobile C-arm cone-beam CT. (program)
Finally, Tharindu De Silva, Postdoctoral Fellow in Biomedical Engineering at Hopkins, reports on the development and clinical application of a 3D-2D registration method for guidance and decision support in spine surgery. Translating the LevelCheck algorithm to a large clinical study underway at Johns Hopkins Hospital, Tharindu shows how novel similarity metrics improve the robustness of the registration process and support automatic spine localization in a manner that works within existing surgical workflow. Compared to conventional manual “level counting,” the LevelCheck algorithm allows automatic labeling of vertebral levels in intraoperative radiographs as an independent check on target localization that could reduce errors, improve speed, and reduce stress in the OR. (program)
Five talks from the I-STAR Lab highlight advances in 3D imaging and image-guided interventions at the 57th Annual Meeting of the AAPM, Anaheim CA.
Jennifer Xu presents on the design and optimization of a cone-beam CT head scanner for detection of acute intracranial hemorrhage. Using task-based detectability index as an objective function for system optimization, Jen’s work extends a cascaded systems model for 3D imaging performance to design the system geometry, x-ray source and detector configuration, and image acquisition technique optimal for the detection of low-contrast lesions. (abstract)
Alejandro Sisniega extends previous work on Monte Carlo modeling to yield a fast (GPU-based) system for dose calculation for cone-beam CT of the head. His work sheds new light on the asymmetric dose distributions associated with short-scan cone-beam imaging, include methods to spare dose to the anterior (eye lens) and the benefits arising from incorporation of a bowtie filter. (abstract)
Grace Gang presents on the topic of “Task-Driven Imaging for Cone-Beam CT in Interventional Guidance.” Her work extends analytical models for the local MTF, NPS, and detectability index in 3D images reconstructed by penalized likelihood estimation to obtain C-arm orbital trajectories that maximize image quality with respect to a specified task. Such work represents an exciting departure from conventional imaging methods, instead leveraging knowledge of the imaging task to maximize image quality and reduce dose. Grace’s work draws from an AAPM Research Seed Funding Grant and earned recognition as a Featured Presentation at the conference. (abstract)
Wojciech Zbijewski joins John Boone, Guang-Hong Chen, and Rebecca Fahrig in a symposium highlighting advances in cone-beam CT. Wojciech’s work focuses on cone-beam CT for musculoskeletal / orthopaedics imaging, including new cone-beam CT scanning systems offering spatial resolution beyond conventional limits. Such work opens the possibility for in vivo quantitative assessment of trabecular micro-architecture, which is recognized as an important image-based biomarker for early osteoarthritis. He also reports the development of dual-energy CBCT for visualization of bone marrow edema, which is usually occult in CT (and conventionally the domain of MRI) but can be rendered conspicuous through dual-energy decomposition of marrow and edemous fluid using advanced model-based reconstruction methods. (abstract)
Finally, Tharindu De Silva presents on the topic of 3D-2D image registration for image-guided spine surgery, showing how the robustness of vertebrae localization can be dramatically improved through incorporation of novel similarity metrics within the registration framework. Tharindu’s work also extends the LevelCheck algorithm for spine localization to a large clinical study underway at Johns Hopkins University and demonstrates valuable decision support without disruption of clinical workflow. (abstract)
New methods for model-based 3D image reconstruction are the focus of The Fully 3D Meeting, May 31 – June 4, in Newport Rhode Island, including 4 presentations from the I-STAR Lab:
Web Stayman leads the charge (Monday, June 1) with breakthrough work on “Task-Based Optimization of Source-Detector Orbits in Interventional Cone-beam CT.” By incorporating a model for task-based imaging performance as the objective function, Web shows how the x-ray source and detector orbit in cone-beam CT acquisition can be optimized to maximize image quality. Such work suggests a new paradigm for CT imaging in which data is collected based upon prior knowledge of the patient and a model for the imaging task.
Steven Tilley, PhD Student in Biomedical Engineering at Hopkins, presents his talk entitled “Generalized Penalized Weighted Least-Squares Reconstruction for Deblurred Flat-Panel CBCT” on Monday, June 1. By incorporating models for system blur arising from the x-ray focal spot size and detector scintillator, Steve shows a method for model-based reconstruction that achieves superior noise and spatial resolution in comparison to conventional deconvolution methods and identifies cone-beam CT configurations for which such modeling is important to maximizing image quality.
Amir Pourmorteza, Postdoctoral Fellow in Biomedical Engineering at Hopkins, presents on the topic of “Reconstruction of Difference using Prior Images and a Penalized-Likelihood Framework” on Tuesday, June 2. Amir’s work shows a model-based reconstruction method capable of delineating subtle changes in patient morphology based on sparse, low-dose data. Such work could be especially valuable in longitudinal imaging studies in which detection of change – e.g., tumor growth or shrinkage – is important.
Qian Cao, PhD Student in Biomedical Engineering at Hopkins, presents a poster entitled, “Multi-Resolution Penalized Weighted Least-Squares Reconstruction for Quantitative Cone-Beam CT Imaging of Bone Morphology” on Wednesday, June 3. Qian’s work builds from a new program in high-resolution orthopaedics imaging headed by Dr. Wojciech Zbijewski, showing a model-based reconstruction method in which various regions of an image can be reconstructed with disparate image quality characteristics – e.g., ultra-high-resolution within regions of bone for visualization of trabecular structure, simultaneous with lower-resolution, low-noise reconstruction in regions of soft tissue.
– Dang et al., Cone-Beam CT of Traumatic Brain Injury Using Statistical Reconstruction with a Post-Artifact-Correction Noise Model (Sunday, February 22 — 10:30am, Room: Crystal C – Session 2)
– Zbijewski et al., Dual-Energy Imaging of Bone Marrow Edema on a Dedicated Multi-Source Cone-Beam CT System for the Extremities (Monday, February 23 — 10:50am, Room: Crystal C – Session 6)
– Sisniega et al., Spectral CT of the Extremities with a Silicon Strip Photon Counting Detector (Monday, February 23 — 1:20pm, Room: Crystal C – Session 7)
– Ouadah et al., Self-Calibration of Cone-Beam CT Geometry Using 3D-2D Image Registration: Development and Application to Tasked-Based Imaging with a Robotic C-Arm (Tuesday, February 24 –11:30am, Room: Oceans 4 – Session 9)
– Uneri et al., Known-Component 3D-2D Registration for Image Guidance and Quality Assurance in Spine Surgery Pedicle Screw Placement (Tuesday, February 24 — 2:20pm, Room: Oceans 4 – Session 10)
– Gang et al., Task-Driven Imaging in Cone-Beam Computed Tomography (Wednesday, February 25 — 1:20pm, Room: Crystal C – Session 14)