The initial experience with the Cosman-Roberts-Wells stereotactic system

Magnetic resonance-guided interstitial high-intensity focused ultrasound for brain tumor ablation

Currently, treatment of brain tumors is limited to resection, chemotherapy, and radiotherapy. Thermal ablation has been recently explored. High-intensity focused ultrasound (HIFU) is being explored as an alternative. Specifically, the authors propose delivering HIFU internally to the tumor with an MRI-guided robotic assistant (MRgRA). The advantage of the authors' interstitial device over external MRI-guided HIFU (MRgHIFU) is that it allows for conformal, precise ablation and concurrent tissue sampling. The authors describe their workflow for MRgRA HIFU delivery.

The Invention and Early History of the N-Localizer for Stereotactic Neurosurgery

Nearly four decades after the invention of the N-localizer, its origin and history remain misunderstood. Some are unaware that a third-year medical student invented this technology. The following conspectus accurately chronicles the origin of the N-localizer, presents recently discovered evidence that documents its history, and corrects misconceptions related to its origin and early history.

The Origin and History of the N-Localizer for Stereotactic Neurosurgery

Nearly four decades after the invention of the N-localizer, its origin and history remain misunderstood. Some are unaware that a third-year medical student invented this technology. The following conspectus accurately chronicles the origin and early history of the N-localizer and corrects some misconceptions related to both.

Computer-assisted and frameless stereotaxy: the initial Australian experience

The trends towards minimally invasive surgery coupled with the increasing use of computer software and hardware have led to an increasing use of stereotactic neurosurgery as a part of mainstream neurosurgery. Computer-assisted and frameless stereotactic systems allow the performance of stereotactic procedures without the need for the mechanical linkage to a stereotactic frame. St Vincent's Hospital, Sydney, has used the Radionics Operating Arm System since March 1994 in 106 cases for stereotactic biopsy, localization of superficial lesions and volumetric resection of tumours. The Operating Arm System uses mechanical digitizers and has the advantages of being able to be used for both framed-based and frameless stereotactic procedures, simplicity of use, and the arm as a 'mouse' software program allowing the surgeon control of the computer program within the sterile operative field.

Frame-based stereotactic biopsy remains an important diagnostic tool with distinct advantages over frameless stereotactic biopsy

OBJECT

As the availability of image-guided surgical navigation systems has increased, the application of frame-based biopsy has declined at our institution, despite equivalent accuracy and safety. There are several cost issues separating the use of surgical navigation systems and stereotactic frames for simple biopsy which may have implications in this era of health care cost control. We retrospectively reviewed the UCSF experience with stereotactic brain biopsy from a 9 year period.

METHODS

Data were collected for 213 consecutive stereotactic brain biopsies performed at UCSF (139 frame-based and 74 frameless). There were no significant differences between the frame-based and frameless biopsy groups with regard to patient demographics, overall histopathology, proportion of nondiagnostic biopsies, or incidence of complications. General anesthesia was used for 9 (6%) and 70 (95%) of the frame-based and frameless biopsy cases, respectively. Frame-based biopsies required a mean of 114+/-3 min of operating room time, while frameless biopsies required 185+/-6 min (P<0.0001). For patients admitted to our neurosurgery service who underwent frame-based (n=110) or frameless (n=52) biopsy within 24 h of admission, the mean lengths of hospital stay were 1.8+/-0.2 and 3.2+/-0.6 days, respectively (P=0.007).

CONCLUSION

Frame-based and frameless stereotactic biopsy approaches were equally effective at providing a tissue diagnosis with minimum morbidity and mortality. The frame-based approach, however, required significantly less anesthesia resources, less operating room time and shorter hospital stays, and thus should still be considered a first-line approach for stereotactic brain biopsy.

Stereotactic radiosurgery XVI: Isodosimetric comparison of photon stereotactic radiosurgery techniques (gamma knife vs. micromultileaf collimator linear accelerator) for acoustic neuroma—and potential clinical importance

PURPOSE

Two stereotactic photon radiation therapy methods are currently in practice for the treatment of acoustic neuroma. In the 1990s, our data and those of others demonstrated isodosimetric advantages for gamma knife technology over linear accelerator methodology. Since then, the introduction of micromultileaf collimator technology has improved the conformity of the linear accelerator method such that the isodosimetric differences between the two techniques have narrowed.

MATERIALS AND METHODS

In this study, modern gamma knife isodosimetry was compared to that of modern linac technology (conformal fixed fields and dynamic arcs) for the therapy of acoustic neuroma. This is an unusual target in that a special sensory nerve (holding the key to hearing preservation) frequently runs through the targeted volume, unlike the majority of other stereotactic radiation therapy targets. This was a single-dose prescription comparison; the perceived extra benefit of fractionation (a technique not routinely available to the gamma knife) was thereby abrogated.

RESULTS

Although the gamma knife technique maintained a slight, but statistically significant, advantage with regard to dose conformity (p < 0.02) (at the debatable cost of a lower minimum target dose), the much higher internal dose gradient (high maximum dose to prescription dose [MD:PD] ratio) could be interpreted as a disadvantage with respect to hearing preservation, although advantageous with regard to tumor ablation. Of the two linac methods, the dynamic arc method gave a statistically significant advantage over the fixed-field method as regards conformity (p < 0.05), at the expense of a slightly higher brainstem dose (an average of 12.4 Gy, cf. 11.7 Gy for fixed fields), but this result was not statistically significant. No significant difference was seen in the MD:PD ratio for the two single-isocenter linac techniques.

CONCLUSIONS

Gamma knife methodology remains well validated, with very good isodosimetry, but when hearing preservation is important, the improving linac technologies will compete with the gamma knife for optimal therapy. In these circumstances, the minor differences in isodosimetry between the two techniques will become important.

Minimally invasive neurosurgery using CRW-3 stereotaxy

The Cosman-Roberts-Wells (CRW-3) scanner independent stereotactic system is a recent arc-radius design developed from the Brown-Roberts-Wells system. The results of 74 supratentorial non-basal tumor suspect cases treated with this second generation computed tomography (CT) guided stereotactic apparatus are presented. Using a simple stereotactic target classification coupled with biopsy, trephine or mini-craniotomy, it has been possible to biopsy, excise and develop new strategies using microneurosurgical techniques with extremely low morbidity.

Stereotactic techniques in managing pediatric brain tumors

Stereotactic techniques available for managing pediatric brain tumors include not only stereotactic biopsy but also stereotactic craniotomy, brachytherapy, and stereotactic radiosurgery. This paper illustrates the use of these techniques in brain tumors in children over a 2-year period at Children's Hospital, Boston. Stereotactic biopsy was used in six cases of deep-seated tumor, with successful tissue diagnosis in all six. Stereotactic craniotomy, in which excision of a mass was done in the stereotactic frame with computed tomography-guided localization and control, was employed in three children. Interstitial radiation using implanted 125I seeds was carried out in two children with malignant astrocytomas: in both it provided good local control but there was later distant recurrence. Stereotactic radiosurgery with a modified linear accelerator was used in eight children as adjunctive therapy for local control. These cases illustrate the versatility of stereotactic techniques involved in a comprehensive approach to pediatric brain tumors.

Stereotactic biopsy of cerebral lesions in patients with AIDS

Central nervous system involvement with AIDS is not uncommon. The indications and timing of brain biopsy remains controversial. Stereotactic CT-guided biopsy offers a safe and effective means of establishing a diagnosis in any patient with a cerebral mass lesion and has less morbidity and mortality than freehand biopsy or exploratory craniotomy. Eleven patients with AIDS have undergone CT-directed stereotactic biopsy between May 1987 and November 1990 with one death from intracerebral haemorrhage. Histological diagnosis of the biopsy specimens showed multifocal leucoencephalopathy, toxoplasmosis, lymphoma and non-specific changes. Biopsy is recommended for patients with an atypical presentation, negative serology, progressive clinical deterioration and differential response of lesions to empirical therapy.