Ferenc Jolesz, M.D., Chair
July 28, 1998
Present: Ferenc A. Jolesz, M.D., Anthony D'Amico, M.D., Jonathan Lewin, M.D., Charles Truwit, M.D., S. Morry Blumenfels, Ph.D., Kim Butts, Ph.D., Warren Grundfest, M.D., Kullervo Hynynen, Ph.D., Ron Kikinis, M.D., Daniel Sullivan, M.D.
Not Present: Bruce Daniels, M.D., Clare Tempany, M.D., Gary Glazer, M.D., James Hayman, M.D., Philip Templeton, M.D., Richard Wahl, M.D., Lucia Zamarano, M.D.
The participants discussed the current progress in new imaging modalities and in high performance computing which are prerequisites for the development of Image-Guided Therapies. The intrinsic relationship between imaging for diagnosis and for guiding therapy, and the role of diagnostic radiology as the parent field of image-guided therapy were emphasized. The participants discussed several aspects of imaging guidance for percutaneous interventional approaches, minimally invasive therapy (endoscopic or laparoscopy) and surgery.
It was clarified that Intraoperative Image Guidance can be provided with both preoperatively- and intraoperatively-acquired images. Both methods of image guidance use computer technology, navigational devices, operator interaction and rely heavily on image processing techniques, i.e., registration (including multimodality fusion) and display methods (including virtual reality techniques).
The significance of image-based modeling for developing image-guided methods for interventional radiology and for surgery was also discussed. The role of surgical planning in optimizing trajectories, and in developing surgical simulations has been found essential by many surgeons. For registration and multimodality fusion computerized techniques such as elastic warping, digital anatomy atlas with localized functional anatomical data can be essential. New methods of position sensing and tracking and the image-based application of various sensors, virtual pointers, will facilitate the development of virtual environments in which interactive display and navigational tools can facilitate image-based therapeutic assistance.
The participants emphasized that various methods of thermal ablations such as interstitial laser or radiofrequency treatment, cryotherapy or focused ultrasound surgery benefit from image-guidance. Of particular importance is the role of temperature-sensitive imaging in monitoring heating or freezing in the detection of tissue phase transitions and irreversible cell death. The participants agreed that among thermal ablations the non-invasive image-guided focused ultrasound treatment has great potential for tumor ablation but also is applicable for occlusion of blood vessels and for functional neurosurgery or targeted drug delivery and gene therapy.
Targeted drug delivery methods, in general, require image guidance. In the future, instillations of chemicals or chemotherapeutic agents as well as high energy isotopes will be a substantial part of interventional radiology. Also, gene therapy and the delivery of larger molecules (peptides, proteins, genetic material) may turn out more effective with targeted, image-guided delivery.
It was discussed that the combination of direct vision and imaging can enhance interventional and surgical techniques. Progress in frameless stereotaxy, navigational tools and multimodality image fusion in neurosurgery should be extended to other fields.
The goal of this task force is to make suggestions that will improve development of minimally invasive procedures using image-guidance tools. The prerequisite is to prove that the use of image-guidance improves outcomes.
In addition the task force identified areas where image guidance can improve the intraoperative definition of tumor margins, and/or reduce the aggressiveness of treatment. In summary, minimally invasive surgery can be combined with pre- and intraoperative imaging modalities to create better treatment outcomes.
In principle, image-guided minimally invasive therapy (MIT) should be potentially as good as or better than existing non-image-guided therapies. The health care system cannot pay for a new therapy which is less effective than the state of the art unless the great savings in morbidity and invasiveness provided by the image-guidance procedure outweighs small losses in efficacy. Utility assessments are necessary to validate this hypothesis before extensive research can be initiated to develop the application.
Image-guided therapy is predicated on treatment of localized disease. If there is no benefit of treating a focal lesion, and systemic therapy is needed, then we see no particular role for image-guided therapy. Diseases which have proven benefit from local treatment should be the first targets of investigations.
Basic science efforts that parallel clinical projects are essential and still very important in this emerging arena. In most cases it is too early to expect rigorous, randomized clinical trials which compare the efficacy of one image-guided therapy to another. We should focus on demonstrations of the clinical efficacy of new therapeutic modalities and the more advanced applications, as well as on the occurrence and rate of associated side effects.
As far as technology development and assessment is concerned it is important to develop therapy delivery systems which are compatible with imaging and therapy monitoring. Also extremely important is development of technologies for surgical planning, simulation and the study of imaging strategies for targeting (i.e., optimizing the ability to view both the target lesion and delivery device at the same time). Monitoring of organ-specific physiologic response is also an important area of research because potentially different challenges are present in each organ system.