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Devin V. Amin, Karl Lozanne, Phillip V. Parry, Johnathan A. Engh, Kathleen Seelman, and Arlan Mintz

Object

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.

Methods

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.

Results

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.

Conclusions

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.

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Juan J. Martin, Ajay Niranjan, Douglas Kondziolka, John C. Flickinger, Karl A. Lozanne, and L. Dade Lunsford

Object

Chordomas and chondrosarcomas of the skull base are aggressive and locally destructive tumors with a high tendency for local progression despite treatment. The authors evaluated the effect of stereotactic radiosurgery (SRS) on local tumor control and survival.

Methods

Twenty-eight patients with histologically confirmed chordomas (18) or chondrosarcomas (10) underwent Gamma Knife SRS either as primary or adjuvant treatment. Their ages ranged from 17 to 72 years (median 44 years). The most common presenting symptom was diplopia (26 patients, 93%). In two patients, SRS was the sole treatment. Twenty-six patients underwent between one and five additional surgical procedures. Two underwent an initial trans-sphenoidal biopsy. The average tumor volume was 9.8 cm3. The median dose to the tumor margin was 16 Gy.

Results

No patient was lost to follow-up. Transient symptomatic adverse radiation effects developed in only one patient. The actuarial local tumor control for chondrosarcomas at 5 years was 80 ± 10.1%. For chordomas both the actuarial tumor control and survival was 62.9 ± 10.4%.

Conclusions

Stereotactic radiosurgery is an important option for skull base chordomas and chondrosarcomas either as primary or adjunctive treatment. Multimodal management appears crucial to improve tumor control in most patients.