• Some feel that the frame-based approach is more accurate. We recommend using a frame-based approach for small and deep lesions.

Frameless

Imaging

• Magnetic resonance imaging (MRI): Pay particular attention to the optimal sequence for visualizing the lesion and communicate the information to the radiologist. Often, radiology will default to the postcontrast image. Make sure the radiology staff know that the scans are for image guidance so that they use thin slices
  
• Computed tomography (CT): In certain situations, CT may be indicated. CT often gives better special localization than MRI. In addition, CT scans can be obtained more quickly than MRIs. Sometimes, CT is the only option (i.e., patient has a pacemaker).
  
• Planning: Because the images are preloaded onto the imaging station (i.e., Stealth Station or BrainLab), there is time to plan the target and entry point. An inline view is suggested to follow the tract of the needle to ensure that vessels and eloquent structures are avoided.

Frame-Based

• The application of the stereotactic head frame is done prior to imaging.
  
  
  
  • Take into consideration where the lesion is (especially if it is high or low) and take that into consideration when placing the frame.
    
    
    
    • Usually, the Cosman-Roberts-Wells (CRW) or Brown-Roberts-Wells (BRW) system is used.
      
    • Be sure to try and keep the ring parallel to the skull base and place the two frontal pins in the supraorbital frontal bone and the posterior pins in the parietooccipital region. Confirm that the ring is on tightly to avoid dislodging the ring and inaccurate lesion targeting as a consequence.
  
  
• Make sure that the frame box is on securely before scanning.
  
• After acquiring the images, confirm that the fiducial points are clearly visible on the scans before planning.
  
• Enter the coordinate into the computer program to get the coordinates for the frame.

Surgery

• Anesthesia: In some situations, it may be performed under monitored anesthesia care (MAC), but general anesthesia is preferred when possible for the frameless. For frame-based biopsies, usually only MAC is needed.

Frameless

• Equipment: A dedicated biopsy kit is made for this procedure. Make sure the equipment is inventoried before surgery.
  
• Pinning: The biopsy arm attaches to the Mayfield pins (Integra). The biopsy arm will guide the trajectory, so plan how the biopsy arm will need to lay to give a free range of trajectories. This is a crucial step!
  
• Trajectory: Register the patient’s head, complete the assembly of the biopsy arm, and then identify the entry site and trajectory. The sagittal, coronal, axial, and target views on the image station are suggested. The target view usually needs the cross-hairs to be lined up or two circles brought together to help determine trajectory. Sometimes, the alignment can be difficult and the manipulation of the arm should be broken into each plane (sagittal, axial, and coronal) to guide the required movements.

Frame-Based

♦ Postoperative