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R J Maciunas

Publications and source records attributed to R J Maciunas.

16 recordsLinked to original sources
PubMed1992

Interactive image-guided neurosurgery.

Interactive image-guided (IIG) surgery involves the synchronal display of the tip of a surgical device on preoperative scans. This display allows the surgeon to locate the present surgical position relative to the final site of surgical interest. We have developed a technique for IIG surgery device based on a six-degree-of-freedom articulated arm. Design accuracy for the arm is less than 0.1 mm and the present implementation has a submillimetric accuracy. The display can show the surgical position on any tomographic image set with simultaneous display on up to three image sets. Laboratory results and clinical applications are discussed.

Brain↗
PubMed1992

An independent application accuracy evaluation of stereotactic frame systems.

The purpose of incorporating stereotactic methodology into neurosurgical procedures is to consistently achieve a high degree of accuracy and precision in localizing intracranial targets. Therefore, the limits of resolution for the therapeutic intervention itself are a function of the accuracy and precision inherent to the particular stereotactic frame system itself. The total clinically relevant error (application accuracy) comprises errors associated with each procedural step, including imaging, target selection, vector calculation and the mechanical errors of stereotactic frames. To evaluate these parameters, a systematic error analysis was carried out in the 4 most commonly used CT-compatible stereotactic devices: the Brown-Roberts-Wells, Cosman-Roberts-Wells, Kelly-Goerss Compass (modified Todd-Wells) and Leksell frames. Over 7,681 independent test measurements were made. The results suggest a potentially significant degree of error in application accuracy of all stereotactic instrumentation which is accentuated by imaging-associated error. These individual error values must be considered with every clinical use of stereotactic frames.

Humans↗
PubMed1992

A universal system for interactive image-directed neurosurgery.

Stereotactic methods confer great accuracy to intracranial target localization, but require strict adherence to a complex program of mechanical and computational maneuvers. A computerized, articulated, localizing 'arm' has been developed that frees the neurosurgeon of these constraints and provides a completely intuitive, 'user-friendly' interface. This universal system is independent of whatever localizing fiducial system is selected. The arm may be sterilized for intracranial use. A variety of intraoperative end effectors may be selected. The patient's CT/MR/PET scans are loaded into computer memory and a three-dimensional shaded surface wireframe diagram of the patient's head is displayed simultaneously with up to 3 independent sets of cross-referenced CT/MR/PET scan images on the intraoperative video screen. The arm's endpoint location and the directional vector are shown as cursors on the relevant scan slices, and change continuously as the surgeon moves the arm. Because the information is continuously updated, an unlimited number of targets and trajectories may be displayed throughout the operation. The arm has an ultimate design accuracy for end-point localization to within 0.1 mm throughout a target volume of 40 x 40 x 40 cm. The tested application accuracy of the first prototype model is 0.31 mm. In clinical use during 30 surgeries, its real-world application accuracy is 0.9 mm. This system provides stereotactic accuracy and universally compatible, intuitive, interactive operation.

Biopsy↗
PubMed1992

Positron emission tomography imaging-directed stereotactic neurosurgery.

The diagnostic yield of stereotactic biopsies depends upon safely sampling the most representative regions of masses. Potentially, localization information presently available from CT and MR scans might be improved by considering regional levels of cerebral metabolism by PET. In 10 selected stereotactic biopsies of intracranial mass lesions, PET scans were obtained using the Siemens CTI system; the Kelly-Goerss Compass system was used as the stereotactic development platform. PET-[18F]-fluorodeoxyglucose (FDG) images provided clinically significant information by appropriately directing biopsy efforts when CT and MRI was inconclusive or misleading. PET-FDG images can be successfully incorporated into routine image-directed stereotactic surgery.

Astrocytoma↗
PubMed1991

TGF beta 1 and TGF beta 2 are potential growth regulators for low-grade and malignant gliomas in vitro: evidence in support of an autocrine hypothesis.

Low-grade astrocytomas, anaplastic astrocytomas and glioblastomas in vitro were found to ubiquitously produce the mRNA of transforming growth factor-beta (TGF beta). TGF beta 1 and TGF beta 2 mRNA were expressed to a lesser degree among the hyperdiploid malignant gliomas. By radioreceptor assay of conditioned medium, TGF beta was secreted predominantly in latent form, in both latent and active form, or only in active form within a panel of low-grade and malignant gliomas. The TGF beta receptor (types I, II, and III) was evident among the glioma lines. Many near-diploid gliomas were growth-inhibited by TGF beta 1 and TGF beta 2 in vitro. Most hyperdiploid glioblastomas showed a positive mitogenic response to exogenous TGF beta 1 and TGF beta 2. A synergistic or additive mitogenic interaction with epidermal growth factor and insulin was observed among some. Under serum-free conditions, anti-TGF beta antibody neutralized the expected growth-regulatory effect of endogenous TGF beta, thus establishing the specificity of the response in vitro. TGF beta 1 also enhanced the clonogenicity of certain gliomas which had been growth-stimulated in monolayer. Thus, basic elements in support of an autocrine hypothesis have been demonstrated: TGF beta mRNA was expressed among low-grade and malignant gliomas, TGF beta was secreted in latent and/or active form into conditioned media and appeared to serve as an endogenous regulator of glioma proliferation in vitro. The mitogenic response, either positive or negative, correlated with the degree of anaplasia and karyotypic divergence.

Blotting, Northern↗
PubMed1990

Tapetool: a software tool for importing image data from image acquisition computers to image processing computers.

Currently, the image distribution gap between image acquisition computers and image processing computers is bridged through magnetic tapes. The tape formats used by the manufacturers of the image acquisition computers are idiosyncratic and fairly complex. A general purpose window based software tool is herein described, which frees the clinical and research sectors of the responsibility of understanding and decoding these complex formats in order to import image databases from acquisition computers to image processing computers. This software tool provides a cornerstone for developing image processing software for diagnostic, therapeutic and surgical planning purposes.

Algorithms↗
PubMed1990

Volumetric measurement of canine gliomas using MRI.

The evaluation of tumor size by neurodiagnostic imaging is an important tool in determining disease progression or treatment efficacy. Apparent tumor size on any single slice image is sensitive to tumor shape and slice orientation. Volumetric measurements which use multiple, stacked images attenuate that sensitivity and can provide insights into tumor architecture. Volumetric measurements were made of induced canine gliomas using three common MR imaging protocols and with and without a contrast agent. Comparisons of the volumes described by each technique are made.

Animals↗
PubMed1990

Stereotactic neurosurgery.

Stereotactic neurosurgery is the technique for locating targets of surgical interest within the brain relative to an external frame of reference. Traditionally, that has meant temporarily attaching a mechanical frame to the patient's skull or scalp. Recent techniques are moving toward ways of reducing the trauma to the patient while retaining the information provided by the frame. Historically, the predominant use of the frames was for placement of electrodes. The advent of computed tomography led to a rebirth of stereotaxy for biopsy and as a guide for resection. Recent advances in computing are supplementing these techniques to allow improved surgical planning and intraoperative information. Finally, highly directed radiation therapy or stereotactic radiosurgery is discussed.

Brain↗
PubMed1989

Magnetic resonance and computed tomographic image-directed stereotaxy for animal research.

Current stereotactic frames for animal experimentation presume normal intracranial anatomy for atlas-directed probe placement. This is an invalid assumption for animal brain tumor models, where distortions of cerebral anatomy make image-directed stereotaxy necessary. To address this need, an accurate and reproducible magnetic resonance and computed tomographic compatible image-directed stereotactic apparatus for animal experimentation is presented.

Animals↗
PubMed1988

The natural history of unruptured intracranial arteriovenous malformations.

The authors conducted a long-term follow-up study of 168 patients to define the natural history of clinically unruptured intracranial arteriovenous malformations (AVM's). Charts of patients seen at the Mayo Clinic between 1974 and 1985 were reviewed. Follow-up information was obtained on 166 patients until death, surgery, or other intervention, or for at least 4 years after diagnosis (mean follow-up time 8.2 years). All available cerebral arteriograms and computerized tomography scans of the head were reviewed. Intracranial hemorrhage occurred in 31 patients (18%), due to AVM rupture in 29 and secondary to AVM or aneurysm rupture in two. The mean risk of hemorrhage was 2.2% per year, and the observed annual rates of hemorrhage increased over time. The risk of death from rupture was 29%, and 23% of survivors had significant long-term morbidity. The size of the AVM and the presence of treated or untreated hypertension were of no value in predicting rupture.

Adolescent↗
PubMed1988

Limiting artifact in CT stereotaxic periventricular procedures. Technical note.

One potential source of computerized tomography image artifact during stereotaxic data acquisition is scatter from standard steel-tipped fixation pins as supplied for use with the Brown-Roberts-Wells stereotaxic headframe. In some cases, this can hinder selection of periventricular targets. Replacement of the steel-tipped pins with aluminum-tipped pins, which produce less artifact, helps to facilitate stereotaxic intervention.

Aluminum↗
PubMed1986

The long-term results of chymopapain chemonucleolysis for lumbar disc disease. Ten-year follow-up results in 268 patients injected at the Mayo Clinic.

The long-term clinical outcome is evaluated for 268 patients after chymopapain chemonucleolysis for radicular complaints referrable to documented intervertebral disc disease. The follow-up period for 92% of these patients was 10 years. No complications due to chymopapain toxicity were observed; 80.1% of patients were relieved of their presenting radicular leg pain and 75.1% were employed at a capacity equal to or more strenuous than before injection. Chemonucleolysis was demonstrated to be a safe and effective treatment modality, with long-term results that compare favorably with those of similarly selected patients undergoing open surgical procedures. In the patients whose chymopapain therapy failed, the outcome of subsequent open surgical procedures was not necessarily compromised by prior chemonucleolysis. A higher rate of failure and subsequent surgical intervention was seen in those patients with injections performed soon after an unsuccessful open procedure on the same side and at the same interspace, those with workmen's compensation or litigation pending, those with a history of work-related injury, those whose employment involved heavy manual labor or extensive driving, and those whose preinjection spine x-ray films indicated retrograde spondylolisthesis.

Adult↗
PubMed1986

The long-term results of chymopapain. Ten-year follow-up of 268 patients after chemonucleolysis.

The effect of chymopapain injection was investigated in myelographically confirmed intervertebral disc herniation in 268 patients after ten years. Mean age is 39.4 years, 178 males and 90 females. Sixty-two patients had compensation or litigation and 12 had prior lumbar spine surgery. Discography was performed in 223 patients, resulting in 134 one-level injections, 124 two-level injections, and ten three-level injections. Forty percent of the patients experienced postoperative muscle spasm for several days. No complications were seen in 241 patients (92%) who were available for follow-up examination at ten years; 86% had less leg pain, 82% were employed at a capacity equal to or greater than before injection, 9% were at a less strenuous job, 1% were disabled, and 8% had retired. In 22 patients treated surgically within one year of chemonucleolysis, disc-related pathology was present in 14 cases and spondylosis or spinal stenosis was present in seven cases. One had a negative exploration and continued to be disabled. Eight patients came to surgical intervention after one year because of persisting symptoms: four patients had disc protrusion, three had laminectomy and spinal fusion, and one had a decompressive laminectomy secondary to spondylotic change. Chemonucleolysis did not prejudice the outcome of subsequent surgical treatment with good results following this intervention. One tumor, a neurofibroma, was found in this study. Chemonucleolysis with chymopapain was a safe and effective treatment of radicular complaints caused by well-documented intervertebral disc herniation.

Adult↗
PubMedDate not supplied

Growth factors in the tumorigenicity of a brain tumor cell line.

We studied a virally induced canine gliosarcoma brain tumor cell line capable of producing brain tumors in vivo following intracerebral inoculation of the cells into the brains of adult mongrel dogs. Cloned populations from this cell line differed in their ability to produce brain tumors in vivo. In vitro transforming growth factor-beta secretion by each clone correlated with in vivo tumorigenicity. Mitogenic activity like that produced with platelet-derived growth factor was also secreted by each clone and correlated with in vivo tumorigenicity. Epidermal growth factor and transforming growth factor-alpha production was not detected in any of the clones of canine gliosarcoma cells. Although only some of the brain tumor cell clones were able to produce tumors in immunologically normal dogs, brain tumors were produced in all dogs pretreated with cyclosporin and in all "nude" mice, suggesting that tumor immunology plays an important role in this brain tumor model. In vitro cloning efficiency of each brain tumor cell clone also correlated with in vivo tumorigenicity. We postulate that transforming growth factor-beta may both stimulate brain tumor cell growth and inhibit host antitumor immune surveillance.

Animals↗