Image-guided surgery and therapy

I am pleased to see the publication of this very novel issue. It brings together in one volume the role modern imaging has to play in surgery and radiotherapy. Certainly in functional neurosurgery imaging has transformed the way it is performed. In its first blossoming in the 1950s, patients were fixed in a stereotactic frame, contrast was injected into the ventricles and x-rays were taken of the patient's head in the frame from AP and lateral projections. One then had to make corrections for the degree of magnification and divergence of the x-ray beam. Following this, the anterior and posterior commissure were identified on the ventriculogram and the mid-commissural point and its coordinates calculated. Having done so, the surgeon referred to an atlas based upon cadaveric studies to calculate the position in the frame with the highest probability of hitting the target. In those days, the motor thalamus or pallidum was identified for Parkinson's disease and tremor [1]. Morbidity after contrast ventriculography was not unusual [2]. Although surgery was effective in abolishing tremor, there were many side effects as the lesions were imprecise by nature. Alleviation of pain with deep brain surgery had even more side effects as the targets, the peri-acqueductal gray area and sensory thalamus, lay in pathways that were also involved in emotion [3]. Deep brain stimulation though studied in the 1950s was never used long term because of technical limitations. Also, with plain x-rays and ventriculography it was never precise where the electrodes were placed [4]. Ventriculography was also poorly tolerated because it was associated with headaches and nausea. The introduction of computed tomography (CT) scanning came about at a time when functional neurosurgery had all but stopped. However, for the first time surgeons were able to visualise tumours and the frame emerged again as a useful tool for biopsying tumours, which was in fact the first form of image-guided neurosurgery [5]. It was also used for stereotactic craniotomies. However, CT scans could not visualise deep brain structures apart from the AC and PC. Therefore in performing functional neurosurgery, CT scanning eliminated the need for contrast ventriculography which made such surgery far more tolerable [6]. It also meant that the accuracy of localisation was no better than CT scanning either. With better understanding of the physiology of movement disorders and pain, new and old targets became far more relevant for disease alleviation. Accurate placement of lesions …