The successful marriage between high-performance computing and sophisticated imaging systems for the production of multi-modality three-dimensional images of top quality, has created an ideal opportunity for significant improvement in pre-operative surgical and treatment planning, as well as in post-operative evaluation. For more than a decade, surgeons at Mayo Clinic in Rochester have been developing, using and assessing the ANALIZE software system for interactive visualisation, manipulation and measurement of 3-D medical images. At present, over 3000 medical scientists, physicians and surgeons in more than 200 institutions throughout the world are working with ANALYZE for Computer Aided Surgery (CAS) and Radiation Treatment Planning (RPT) in various applications such as craniofacial, orthopedic and neurosurgery planning as well as radiation therapy planning. Undoubtedly, ANALYZE will result in minimised patient risk and morbidity and in a substantial reduction of health care costs.
Dr. Richard Robb and his colleagues of the Biomedical Imaging Resource (BIR) at the Mayo Clinic have brought together a number of exemplary cases in an elucidating paper on CAS and RTP. A short overview will highlight the fascinating results they have achieved using ANALYZE. Craniofacial surgery (CFS) involves surgery of the facial and cranial skeleton and soft tissues which implies both quantitative and qualitative knowledge of the anatomy. A direct visualisation of the entire 3-D context allows precise measurement of the concerned structures, prior to the actual operation. Interactive simulation of the surgical procedure permits the surgeon to draw up an accurate pre-operative plan, thus reducing the final intervention time in the operating room. Comparison of the post-operative CT and MRI scans with the pre-operative photographs allows for objective evaluation of the outcome while providing statistical data for the establishment of future normative values regarding pathological conditions.
Visualisation and analysis of brain anatomy and function plays a capital role in neurosurgery, apart from multi-modality images containing non-anatomic fiducials. In this way, the surgeon gains a clear insight in the anatomical link between the areas of functional control and both normal brain tissue and pathology in order to specify for instance the margins for resection of a tumour. First, the removal can be rehearsed by means of object manipulation tools, provided in the shape of bottom panels in the ANALYZE package. These data is used in the real intervention to preserve adjacent normal tissues from being damaged which might cause postoperative neurological motor deficit.
It is not always possible to perform surgery, for example in case of diffuse diseases or localised pathology, adjacent to or even infiltrating surrounding critical structures. Radiation therapy may constitute an alternative but often effective treatment. Thanks to three-dimensional multi-modality imaging, the design of an optimal plan for radiation treatment can be envisaged in order to deliver a lethal dose to the cancer cells while the healthy tissue is only submitted to a far lower and less dangerous dose. The dose distribution can be mapped in advance as to quantitatively compare the kill and non-kill regions.
X-ray Computed Tomographic (CT) volume images which have been processed with 3-D rendering techniques, subsequently can be co-registered with Magnetic Resonance Images (MRI) to offer a simultaneous integrated visualisation of both soft and hard tissues. In orthopedic surgery, the muscles, tendons and ligaments are equally important to the surgeon as the bones. In this regard, the interactive 3-D visualisation amounts to direct quantitative measurements of distances, areas, volumes and shapes. This permits the surgeon to draw up an effective pre-operative plan for a perfect approach to the fracture repair.
With prostate surgery, two major problems occur, which are turning this intervention currently into one of the most delicate ones. First of all, surgeons experience severe difficulties as to distinguish malignant from benign tumours. Giving the seriousness of prostate cancer, one is inclined to surgically treat any prostate complaint, necessary or not. Second, prostate surgery often leads to psychologically devastating complications, such as impotence and incontinence. Advanced MRI technology may therefore refine the diagnostic ability and optimise the surgical planning since the highly variable pelvic anatomy of each individual patient can be far better visualised up to its tiniest details. Thus, the surgeon is able to protect adjacent vital structures when performing a prostatectomy. Only in case the cancer has spread beyond the enclosing prostate capsule, surgery is not recommendable. The accurate detection of such a condition is absolutely indispensable for a proper therapeutic stratification of prostate cancer patients.
The ANALYZE software system has ultimately proven its revolutionary potential in some unusual and challenging surgical interventions. Three-dimensional CT imaging has been used to periodically measure the differential lung volume over time as a result of single-lung transplant surgery. The lung images were most carefully segmented to obtain precise measurements of the transplanted lung in comparison with the original lung. A transplanted lung usually does not fill with air to the same extent as the original one, but results tend to improve within a few months of surgery. The use of 3-D CT scans allows accurate evaluation of the performance outcome.
The separation of Siamese twins could be executed successfully after designing a detailed pre-operative plan by means of volume rendering and the interactive tools associated with realistic 3-D visualisation, manipulation and measurements, the three major components to support sophisticated surgery planning. The separation has been practised in advance in order to determine the optimal bisection to minimise the size of the surgical opening and to decide upon the quantity of skin and grafting material needed to cover the openings. These examples show that three-dimensional visualisation and analysis of medical images are starting to outgrow the trial-and-error stage of careful research and are gradually moving into the every day practice of the hospital operating theatres. You can find the full text of the paper, written by the BIR research team and illustrated with some thrilling visual material, at the web site of the Mayo Clinic.