inflammation of theology

Friday, 6 May 2022

Stereotactic Bipsy

Stereo - 3 dimensional, Taxis - to move toward 

Frame-Based Stereotaxis 4 system has been used: 
  1. Polar coordinate 
    • Guidance of the probe be described with regard to the angle in relation to a skull entry point 
  2.  2. Arc-radius
    • Commonly used
    • Basis for Leksell frame
    • Probe equivalent to the radius of a semicircular arc will reach the center of the arc when introduced perpendicular to any point along the arc 
  3. Focal point
  4. Phantom target  
Frameless Stereotaxis
  • Principles: point-pair registration or surface contour registration can be used to establish the relationship between the preoperative images and those in the surgical field
  • Requires a set of at least three non-colinear points to be defined in the coordinates of the images
  • Registration
    • Marker
    • Surface contour 
Indication for Stereotactic Biopsy
  • Goal: to provide a representative sample for pathologic diagnosis to guide subsequent treatment
  • Advantages:
    • Higher accuracy
    • Minimize potential adverse effects
  • Lesion that support stereotactic over open biopsy:
    • Lesions that do not exert a symptomatic mass effect
    • Not treatable by surgical excision eg metastases, malignant intrinsic brain tumor
    • Deep seated lesion or occupying space in eloquent area or deep nuclei
    • Infiltrative lesion eg gliomatosis cerebri
    • Lesion suggest infection or demyelinating rather than tumor
  • Vascular tumor eg metastatic renal cell carcinoma, etc
  • Location of tumor close to major blood vessel, vessel-rich Sylvian fissure, cavernous sinus
  • Patients on anticoagulant 
Sampling Error
  • Particularly in non-enhancing lesion eg LGG
  • To improve accuracy: use PET scan, MR Perfusion, MRS
  • Hemorrhage 
    • Damage to friable vessels within targeted neoplastic lesion 
    • Vessels along trajectory
  • Neurological deficits
    • Direct brain damage
    • Edema 
Stereotactic Biopsy of Brainstem Lesions 
  • Transtentorial approach
  • Ipsilateral transfrontal trajectory
  • Suboccipital transcerebellar route
  • Contralateral, extraventricular, transfrontal approach 
Trajectory Planning
  • Area of thickest enhancement 
  • Slightly deeper or shallower samples could be obtained along the same trajectory 
Entry point
  • Avoid entry into a dural blood vessel, cortical blood vessel, or sulcus
  • Entry point could be planned to be incorporated into future craniotomy incision avoid unnecessarily traversing pial or ependymal surfaces