Imaging requirements for image guided interventions

Accuracy and robustness of image guidance methodology is obviously of critical importance in surgical interventions and is of significant current interest. In neurosurgery surgical requirements vary from the highest precision (1 mm or better) for procedures such as pallidatomy and electrode placement to about 5 mm for craniotomy planning. Outside the head high precision may be required in areas such as the spine but less important in pelvic or abdominal surgery. In the eye or ear precision of a few tens of microns may be necessary. Validation of these new methodologies is difficult and requires painstaking and methodical work, such as that done recently with stereotaxic frames (Maciunas, 1994), yet it is of vital importance. Matching image sampling to application is important and often neglected. It is no use expecting surgical guidance accurate to 1 mm with CT slices acquired at a thickness of 5 mm or more