Imaging for Therapy Guidance

Keywords: medical imaging, image-guidance, flat-panel imagers, cone-beam CT, volume imaging, MRI, image science, imaging performance, radiation therapy

Among the most challenging and exciting topics in medical imaging research is the development of advanced imaging technologies for guiding therapeutic procedures. With applications ranging from radiation therapy to interventional procedures and surgery, the importance of bringing high-performance imaging into the arena of therapy is clear. The development of such novel technologies, however, raises a number of critical research questions, ranging from issues of basic image science to integration with the therapeutic procedure. These questions are at the heart of the projects carried out in the laboratories of the image-guided therapy (IGTx) group, encompassing a broad range of topics targeted toward the development and rapid deployment of innovative imaging technologies for therapy guidance. Central to Dr. Siewerdsen’s research are issues of basic imaging physics, quantitative description of multi-dimensional imaging performance and imaging task, and the development of novel multidimensional imaging technologies.

A promising modality under development in this program involves the use of flat-panel detectors for volumetric cone-beam CT. Such systems can provide sub-millimeter spatial resolution in combination with soft-tissue visibility and appear well suited to image-guided procedures. An experimental benchtop for flat-panel cone-beam CT is shown in Figure (a). This system provides a powerful proving ground for investigation of basic imaging performance issues within a flexible, computercontrolled geometry. An example volumetric image is shown in Figure (b), illustrating the uniform quality and exquisite spatial detail achieved with this technology. Translation to clinical platforms is underway, with systems being implemented on: i.) a medical linear accelerator for soft-tissue target guidance in radiation therapy; and ii.) a mobile C-arm for volume CT guidance of interventional procedures.

Issues central to these and other research activities in the projects include:
• Imaging physics
• 3-D reconstruction
• Volume CT
• Optical tracking and navigation
• Flat-panel detectors
• MR-guided procedures
• Image processing and registration
• Functional guidance
• Imaging task and image theory
• Instrumentation and integration
The projects enjoy a lively, interdisciplinary atmosphere of physicists,
engineers and clinicians.

For further information, please go to http://www.igtx.ca/

Graduate Students:

• Sajendra Nithiananthan

Selected References:

• Siewerdsen JH, Cunningham IA, and Jaffray DA, “A framework for noise-power spectrum analysis of multidimensional images,” Med Phys 29 (11) (2002).

• Groh BA, Siewerdsen JH, Drake DG, Wong JW, and Jaffray DA, “Performance comparison of MV and kV cone-beam CT,” Med. Phys. 29(6) 967-975 (2002).

• Jaffray DA, Siewerdsen JH, Wong JW, and Martinez AA, “Flatpanel cone-beam computed tomography for image-guided radiation therapy,” Int. J. Rad. Onc. Biol. Phys. 53(5) 1337-1349 (2002).

• Siewerdsen JH and Jaffray DA, “Cone-beam computed tomography with a flat-panel imager: magnitude and effects of X-ray scatter,” Med. Phys. 28(2) 220-231 (2001).

• Siewerdsen JH, Edmundson GK, Sanders WP, Wong JW, Martinez AA, and Jaffray DA, “Flat-panel cone-beam CT: A novel imaging technology for image-guided procedures,” SPIE Medical Imaging 2001: Visualization, Display, and Image-Guided Procedures , Vol. 4319, 435-444 (2001).

• Siewerdsen JH and Jaffray DA, “Cone-beam computed tomography with a flat-panel imager: noise considerations for fully 3-D imaging,” SPIE Physics of Medical Imaging Vol. 3336, 546-554 (2000).

• Jaffray DA and Siewerdsen JH, “Cone-beam computed tomography with a flat-panel imager: initial performance characterization,” Med Phys 27(6) 1311-1323(2000).

• Siewerdsen JH and Jaffray DA, “Optimization of X-ray imaging geometry (with specific application to flat-panel cone-beam computed tomography,” Med. Phys. 27(8) 1903-1914 (2000).

• Siewerdsen JH and Jaffray DA, “Cone-beam computed tomography with a flat-panel imager: effects of image lag,” Med Phys 26(12) 2635-2647 (1999).

• Siewerdsen JH and Jaffray DA, “A ghost story: spatio-temporal response characteristics of an amorphous silicon flat-panel imager,” Med Phys 26(8) 1624-1641 (1999).