stereotactic

Stereotactic refers to a method of locating targets within the body in a three-dimensional reference frame to guide diagnostic or therapeutic procedures. The term combines Greek roots meaning solid or three-dimensional space and arrangement or positioning. In practice, stereotaxy uses a coordinate system to correlate a target with a fixed or image-guided reference.

Techniques vary between frame-based and frameless approaches. Frame-based stereotaxy attaches a rigid frame to the skull or body, providing a fixed coordinate reference for planning and instrument targeting. Frameless systems rely on image-guided navigation, surface or fiducial registration, and real-time tracking to identify coordinates without a rigid external frame. Planning typically uses CT, MRI, or PET imaging to define targets and trajectories, with intraoperative verification to ensure accuracy.

Common applications include neurosurgical biopsy of brain lesions, lesioning or ablation of targeted brain regions for movement disorders, and the placement of electrodes for deep brain stimulation. In radiotherapy, stereotactic techniques enable highly focused delivery of radiation to brain or body targets, as seen in stereotactic radiosurgery (eg, Gamma Knife) and stereotactic body radiotherapy, which aim to maximize tumor dose while sparing surrounding tissue.

History and development trace the concept to mid-20th century pioneers who combined anatomy with coordinate localization, followed by advances in imaging, navigation, and robotics. Modern stereotaxy emphasizes accuracy, minimally invasive access, and the ability to plan and verify targets using multimodal imaging, while acknowledging risks such as hemorrhage, infection, registration or targeting errors, and patient movement.