Stereotactic biopsy of intracranial brain lesions. High diagnostic yield without increased complications: 65 consecutive biopsies with early postoperative CT scans

Diagnostic yield and complication rate were analyzed for a series of 65 consecutive stereotactic biopsies of intra-axial brain lesions. The diagnostic yield was 98.5 +/- 1.5% and the complication rate was 1.5%. A median number of 14 biopsies (range 1-48) were taken per lesion. The biopsy sites followed a clockwise pattern, going from the superficial margin to the center and the deep margin of the lesion with respect to the inner table of the skull. A side window cannula biopsy needle was used. All patients underwent immediate postoperative CT scans within 4 h of biopsy to rule out intracranial complications. All patients were discharged within 24 h after biopsy, unless medical reasons unrelated to the biopsy required further hospitalization. We attribute the high diagnostic yield in our series to the high number of systematically taken biopsies per lesion. The higher number of biopsies did not lead to an increase in complications. From our experience, it appears safe to discharge patients the same day or within 24 h after a stereotactic biopsy if the postoperative CT shows no complication. Stereotactic biopsy could often safely be performed on an outpatient basis.

LINAC-based spinal stereotactic radiosurgery

The authors' report on the use of a prototype spinal stereotactic radiosurgery frame which was employed for the treatment of 9 patients who presented with recurrent neoplastic involvement of the spinal column. All patients had failed standard therapy consisting of surgery, external fractionated radiation therapy, and/or chemotherapy. Eight of the lesions represented metastatic tumors in the vertebral column, one of the lesions was a primary osteosarcoma involving multiple vertebral bodies. The lesions were found at multiple levels, from the cervical through the sacral region. Six out of the 9 patients presented with epidural compression: 4 of the 9 patients with evidence of myelopathy: 2 of the 9 patients with radicular symptoms secondary to compression from the tumor, and 1 patient was free of any compressive symptoms. All patients had pain requiring narcotics. Patients were treated with a median radiosurgical dose of 800 cGy (range 800-1.000) with a median of 1 isocenter (range 1-7 isocenters) and median normalization of 80% to the isodose contour (range 80-160). Median dose delivered to the already prior irradiated spinal cord was 179 cGy (range 52-320 cGy) with a median spinal cord dose of 34 (range 4-68). To date, there have been three minor complications: one radiation-induced esophagitis which was treated medically: one wound infection, and 1 patient requiring an additional 24 h of hospitalization stay. There have been no major complications. To date, 5 of the 9 patients have died, all from causes unrelated to the spinal radiosurgery. Three out of the 9 patients have been followed for more than 1 year. In all 3, there was radiographic regression of the tumor and epidural compression. In 2 patients, there was histologic confirmation of absence of tumor in the treated site: in 1 patient. no tumor was found at postmortem. 12 months after treatment, when the patient died of unrelated causes. Although the number of patients followed is limited, the phase I study clearly shows the technical feasibility of spinal radiosurgery for the control of metastatic involvement of the vertebral column even in the face of epidural compression.

Preliminary clinical experience with linear accelerator-based spinal stereotactic radiosurgery

A prototype device called an extracranial stereotactic radiosurgery frame was used to deliver stereotactic radiosurgery, with a modified linear accelerator, to metastatic neoplasms in the cervical, thoracic, and lumbar regions in five patients. In all patients, the neoplasms had failed to respond to spinal cord tolerance doses delivered by standard external fractionated radiation therapy to a median dose of 45 Gy (range, 33-65 Gy/11-30 fractions). The tumors were treated with single-fraction stereotactic radiosurgery with the spinal stereotactic frame for immobilization, localization, and treatment. The median number of isocenters was one (range, one to five) with a median single fraction dose of 10 Gy (range, 8-10 Gy) with median normalization to 80% isodose contour (range, 80-160%). There has been a single complication of esophagitis to date from radiosurgery of a tumor involving the C6-T1 segments; the esophagitis resolved with medical therapy. Median follow-up in this group of patients has been 6 months (range, 1-12 mo). To date, there has been no radiographic or clinical progression of the treated tumor in any patient. Two patients have died from systemic metastatic disease. In the three surviving patients, there has been computed tomographic- or magnetic resonance-documented regression of the treated tumor with a decrease of thecal sac compression with a median follow-up of 6 months (range, 3-14 mo). These five patients represent the first clinical application of stereotactic radiosurgery in the spine. The results suggest that extracranial radiosurgery may be suitable for the treatment of paraspinal neoplasms after external fractionated radiation therapy, even in the face of spinal cord compression.

A prototype device for linear accelerator-based extracranial radiosurgery

A prototype frame for accurate stereotactic localization and linear accelerator (LINAC)-based treatment of extracranial targets was developed. The ECRSF is designed to employ either spinal or skeletal osseous fixation to immobilize the area of interest and then encircle the targeted region with a traditional orthogonal, three-axis system. A series of experiments (n = 5) with semi-radiolucent calibration targets (n = 15) and computed tomography (CT) scanning using the EC showed that a mean localization error of 0.98 +/- 0.22 mm was obtainable in the last two and most accurate series of experiments with these targets (n = 8). Using the LINAC to irradiate these same targets demonstrated an overall radiation treatment accuracy ranging from 1.4 to 2.0 mm. This discrepancy between localization error and overall radiation treatment error can be explained by a lack of isocentricity of the LINAC treatment which is typically less than 1 mm and can be as low as 0.5 mm. These data demonstrate that extracranial stereotactic radiosurgery is now technically feasible and that the accuracy of such treatment would be acceptable for clinical treatment.

Template-guided stereotactic implantation of malignant brain tumors for interstitial thermoradiotherapy

A phase I trial of 25 patients with anaplastic astrocytoma or glioblastoma multiforme is described. Hyperthermia and radiation were delivered stereotactically by means of template-guided interstitial catheters loaded with ferromagnetic wires and then 192Ir seeds. Implant volumes ranged from 15 to 113 ml (mean 54 ml) involving 9-38 catheters (mean 18); parallel catheters used hexagonal spacing of 1.0-1.5 cm. Patient tolerance of these procedures was excellent. Postoperative morbidity due to additional mass effect or edema was low, but there has been one death and one complication of hydrocephalus, bleeding and symptomatic pneumocephalus, each.

Hyperthermia in cancer treatment

Hyperthermia, used as an adjunct to radiation therapy, can increase tumor regression significantly. When used as a local (as opposed to regional or systemic) modality, proper treatment requires detailed knowledge of tumor and normal tissue geometry, and physiologic parameters such as perfusion and thermal conductivity. A brief review of local heating techniques and details of two techniques used to treat brain tumors are provided: Scan Focused Ultrasound and Interstitial Ferromagnetic Seed Implants. These techniques require the most sophisticated use of diagnostic radiology methods. Data from several modalities such as CT, MRI, angiography, and xenon CT perfusion studies must be merged into a consistent data set. This data set must be indexed precisely relative to the treatment apparatus. Real-time noninvasive temperature monitoring of the treatment field has not been achieved at this time, but is of interest to researchers in hyperthermia.

Treatment planning of template-guided stereotaxic brain implants

We have initiated a Phase I clinical trial of interstitial hyperthermia induced with inductively heated ferromagnetic implants in combination with Ir-192 implants for glioblastomas and anaplastic astrocytomas of the brain. For speed and accuracy of the implant procedure, and to control the radiation and thermal dose, a stereotaxic frame is used to position a template. We have modified the Brown-Roberts-Wells frame to be used with a variety of templates which we designed. On the morning of the implant procedure, a CT scan is done, and a CT-based treatment plan is then completed before the patient goes to the operating room. We also describe the CT-based treatment planning system developed to accommodate the template-guided implant and illustrate its clinical use.

A derivation of Batho's correction factor for heterogeneities

Batho's correction factor for dose in a heterogeneous, layered medium is derived from the tissue-air ratio method (TARM). The reason why the Batho factor is superior to the TARM factor at low energy is ascribed to the fact that it accounts for the distribution of the scatter-generating matter along the centerline. The poor behavior of the Batho factor at high energies is explained as a consequence of the lack of electron equilibrium at appreciable depth below the surface.