I-STARs at 101st RSNA Conference in Chicago

November 18, 2015

At the 101st meeting of the RSNA, four presentations from the I-STAR Lab highlight new research in CT imaging physics. Topics range from the development of a new cone-beam CT system for detection of traumatic brain injury to dual-energy CT for detection of bone marrow edema.

Jennifer Xu, a PhD student in Biomedical Engineering at Johns Hopkins University, presents on “Development of a Dedicated Cone-beam CT System for Imaging of Intracranial Hemorrhage.” Her work uses a task-based image quality model to design a new cone-beam CT system for reliable detection of brain injury at the point of care. By combining optimal system design with high-quality artifacts correction and model-based 3D image reconstruction, the research has enabled development of a scanner prototype for first clinical tests in the ICU.

J. Web Stayman, PhD, Assistant Professor of Biomedical Engineering at Johns Hopkins University presents 2 talks on advanced 3D imaging methods – the first involving “Fluence field modulation for low-dose x-ray computed tomography using compact multiple aperture devices,” and the second on “Polyenergetic known component reconstruction (KCR) for flat-panel CBCT with unknown material compositions and unknown x-ray spectra.”

Finally Wojciech Zbijewski, PhD, Faculty in Biomedical Engineering at Johns Hopkins University, will present on “Ultra-High Resolution Quantitative Cone Beam CT of the Extremities with a CMOS X-ray Detector.” His work advances a cone-beam CT system for extremities imaging beyond conventional spatial resolution limits to permit quantitative analysis of subchondral bone morphology. Through development of a new imaging chain with a high-resolution detector, model-based multi-resolution 3D image reconstruction, and motion correction methods, the research promises a new means for in vivo quantitative image-based biomarkers  of bone health and disease progression in osteoarthritis.

Hao Dang Named a 2016 Siebel Scholar

August 18, 2015

Hao Dang, a graduate student in the I-STAR Lab at Hopkins, was recently named to the 2016 class of Siebel Scholars for outstanding research, academic achievements, and leadership. The Siebel Scholars program was established by the Thomas and Stacey Siebel Foundation in 2000 to recognize talented students at the world’s leading graduate schools of business, computer science, bioengineering, and energy science. The Engineering program at Hopkins is proud to be among the few programs in the world recognized by the Siebel Scholars Foundation. Hao is a PhD student in Biomedical Engineering supervised by Professor Jeffrey H. Siewerdsen. His thesis focuses on the development of new methods for 3D image reconstruction in cone-beam CT (CBCT) using advanced models of imaging physics. His project involves development of an imaging system for improved detection of intracranial hemorrhage. Hao’s work has yielded substantial improvement in image quality compared to traditional reconstruction methods by accurately incorporating the image noise characteristics associated with artifact correction (paper). His previous work includes automatic image-to-world registration for surgical guidance using C-arm CBCT system (paper) and work with Dr. J. Webster Stayman on novel image reconstruction using prior image information for dose reduction and image quality improvement (paper). The Siebel Scholarship includes a stipend support from the Siebel Scholars Foundation for his final year of graduate studies.

Best Paper in Medical Physics 2014 Awarded to Jennifer Xu

June 24, 2015

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!

Four I-STAR Talks in CARS Barcelona

June 10, 2015

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)

I-STARs Shine at AAPM 2015, Anaheim CA

June 9, 2015

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)