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Central Nervous System
Published in Pat Price, Karol Sikora, Treatment of Cancer, 2020
Stereotaxy relates to the method of localization in which the target is defined in relation to an external coordinate system. This has the potential for a greater degree of accuracy but implies the need for rigid immobilization. The fixation may be “internal,” using pins screwed into the skull and suitable only for one-off treatments, or “external,” based on an accurate, re-locatable anterior and posterior, individualized immobilization mask (or beam direction shell), usually in association with a dental mouth-bite. Externally fixated shells can be used for the delivery of single or multiple fractions of SRT. Accuracies of 1–2 mm are standard.
Anterior thalamic nucleus stimulation: issues in study design
Published in Hans O Lüders, Deep Brain Stimulation and Epilepsy, 2020
Two other surgical issues to be decided are whether to perform stereotaxy under local or general anesthesia, and whether to implant the device in one or two stages. The anesthetic technique is at the discretion of the surgeon and anesthesiologist. Increasing numbers of procedures are done under local anesthesia, or brief propofol anesthesia just for placement of the frame. Implantation of the electrodes in one stage and extension leads plus the stimulator in a second depends on protocol needs. Externalization of the electrodes for a few days allows recording from the stimulation target. In theory, this could identify patterns of participation in seizures that would allow development of predictors for future successes. However, two operations are required instead of one, increasing risk and cost. Special care must be taken to avoid infection when implanting external electrodes.
Neurosurgery: Minimally invasive neurosurgery
Published in Hemanshu Prabhakar, Charu Mahajan, Indu Kapoor, Essentials of Geriatric Neuroanesthesia, 2019
Charu Mahajan, Indu Kapoor, Hemanshu Prabhakar
Stereotaxy helps in assessment of depth and direction so that this guided instrumentation causes minimal trauma with improved precision. However, in frame-based stereotactic procedures, the frame is a hindrance for access to the airway. The newer frameless stereotaxy uses scalp markers as fiducial points which help in relating the computer-generated 3-D image to surgical instruments. Stereotaxy may be used for biopsy or excision of brain tumors, drainage of abscess/hematoma, and deep brain stimulation (DBS) for patients having Parkinson’s disease.
Technical efficacy and local recurrence after stereotactic radiofrequency ablation of 2653 liver tumors: a 15-year single-center experience with evaluation of prognostic factors
Published in International Journal of Hyperthermia, 2022
Peter Schullian, Gregor Laimer, Edward Johnston, Daniel Putzer, Gernot Eberle, Yannick Scharll, Gerlig Widmann, Christian Kolbitsch, Reto Bale
Radiofrequency ablation (RFA) has gained wide acceptance in the management of hepatocellular carcinomas (HCCs), intrahepatic cholangiocarcinoma (ICC) and liver metastases from colorectal cancer, breast cancer and neuroendocrine tumors [1–3]. In patients with early HCC [4], RFA has comparable overall survival to hepatic resection (HR) paired with lower morbidity rates due to its minimally invasive nature. However, HR often remains the treatment of choice in the context of preserved liver function. This is mainly attributed to relatively high rates of local recurrence (LR) reported in the RFA literature, varying from 10 to 39.1% within 5 years – depending on tumor size and number [5,6]. To minimize the chances of undertreatment, it is critical to establish a sufficient safety margin surrounding the tumor completely by at least 5 mm of ablation zone in all dimensions [7]. However, adequate treatment margins may be particularly challenging for tumors > 3 cm or in situations when the target is either difficult to visualize, awkward to access, or situated adjacent to vulnerable structures. To increase the size of the ablation zone, multiple RF electrode techniques or more efficient thermal ablation devices, such as microwave may be used [8–11]. However, conventional US- or CT-fluoroscopic guidance lacks reliability for accurate three-dimensional probe placement. Stereotaxy, already widely used in radiotherapy and surgical procedures, represents a useful way of precisely transposing pre-defined three-dimensional plans to the patient in order to enable more complex or challenging interventions.
Computer-assisted surgery in medical and dental applications
Published in Expert Review of Medical Devices, 2021
Yen-Wei Chen, Brian W. Hanak, Tzu-Chian Yang, Taylor A. Wilson, Jenovie M. Hsia, Hollie E. Walsh, Huai-Che Shih, Kanako J. Nagatomo
Neuronavigation arose through a combination of stereotaxy, neuroimaging, and computer technology [6,7]. Stereotaxy is an approach to localizing and targeting a specific point within a defined space using a three-dimensional coordinate system. Thus, regarding the brain as a geometric volume, stereotactic surgery utilizes a coordinate system to precisely and accurately target any structure within the brain [8]. In the early 1900s, stereotactic neurosurgery began by using a three-dimensional Cartesian coordinate system defined by a rigid frame affixed to the patient’s head to target specific anatomical regions in the brain. These early frame-based stereotactic systems were used to localize deep brain structures based on external skull landmarks using relationships defined by normalized cadaveric dissection studies, giving rise to the field of ‘craniometry’ [9]. Not surprisingly, however, these early stereotactic systems, of which there were several, all suffered from inaccuracies generated by the variability of brain structures’ correlation with skull landmarks.
The future of neuromodulation: smart neuromodulation
Published in Expert Review of Medical Devices, 2021
Dirk De Ridder, Jarek Maciaczyk, Sven Vanneste
Therefore, a new non-medicated way to treat brain disorders is crucial. Interestingly, the methodology for this is already available, albeit in a rudimentary form. Indeed, more than 60 years ago, in 1952, Delgado described the implantation of electrodes into the brain to measure electrical brain activity as a diagnostic tool, and deep brain stimulation through the same electrodes as a possible treatment for mental disorders [15]. This was based on the clinically beneficial effects of psychosurgery, by making lesions in the brain, and the development of stereotaxy [16], through which very targeted small lesions could be made [17]. The described technique was adapted for movement disorders in 1963 by Bechtereva in Russia [18] and later, in 1987, by Benabid in the western world [19]. However, the last 50 years have been characterized by a relative stagnation, in the development of new technology for brain stimulation, in stark contrast to the exponential technological progress in consumer devices such as smartphones, personal computers, etc. The discrepancy between the highly advanced consumer devices and brain implantation devices demonstrates there is a very large margin for improvement. In summary, neuromodulation consists of an electrode that is placed in the brain, on the spinal cord or near a nerve and affects the offended nerves and support cells. The International Neuromodulation Society defines neuromodulation as the alteration of nerve activity through targeted delivery of a stimulus, such as electrical stimulation or chemical agents, to specific neurological sites in the body [20]. The battery and the software that controls the stimuli are contained in an internal pulse generator (IPG), an adapted and derivative of the classic cardiac pacemaker.