Image-guided frameless stereotactic techniques provide an alternative to traditional head-frame fixation in the performance of fine-needle biopsies. However, these techniques still require rigid head fixation, usually in the form of a head holder. The authors report on a series of fine-needle biopsies and brain abscess aspirations in which a frameless technique was used with a patient's head supported on a horseshoe headholder. To validate this technique, they performed an in vitro accuracy study.
Forty-eight patients underwent fine-needle biopsy of intracranial lesions that ranged in size from 0.9 to more than 107.7 ml; a fiducial-less, frameless, image-guided technique was used without rigid head fixation. In 1 of the 48 patients a cerebral abscess was drained. The accuracy study was performed with a skull phantom that was imaged with a CT scanner and tracked with a registration mask containing light-emitting diodes. The objective was a skin fiducial marker with a 4-mm circular target to accommodate the 2.5-mm biopsy needle. A series of 50 trials was conducted.
Diagnostic tissue was obtained on the first attempt in 47 of 48 brain biopsy cases. In 2 cases small hemorrhages at the biopsy site were noted as a complication on the postoperative CT scan. One of these hemorrhages resulted in hand and arm weakness. The accuracy study demonstrated a 98% success rate of the biopsy needle passing through the 4-mm circular target using the registration mask as the registration and tracking device. This demonstrates a ± 0.75-mm tolerance on the targeting method.
The accuracy study demonstrated the ability of the mask to actively track the target and allow navigation to a 4-mm-diameter circular target with a 98% success rate. The frameless, pinless, fiducial-less technique described herein will likely be another safe, fast alternative to frame-based stereotactic techniques for fine-needle biopsy that avoids the potential morbidity of rigid head-pin fixation. Furthermore, it should lend itself to other image-guided applications such as the placement of ventricular catheters for shunting or Ommaya reservoirs.