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Biomedical subjects

W A Friedman

Publications and source records attributed to W A Friedman.

At least 73 records · Page 4Linked to original sources

Radiosurgery for arteriovenous malformations.

In summary, many reports indicate that approximately 80% of AVMs in the "radiosurgery-sized range" will be angiographically obliterated 2 years after radiosurgical treatment. Permanent neurologic complications are rare (2 to 3%). The major drawback of this treatment method is that patients are unprotected against hemorrhage during the 2-year latent period. Although radiosurgery has been used primarily as a single modality of treatment in previous studies, more recently it has been increasingly used as part of a multimodality treatment approach incorporating surgical and endovascular methods. Radiosurgery is currently of unproven value in the treatment of cavernous malformations.

Cerebral Hemorrhage↗

Linear accelerator-based stereotactic radiosurgery for acoustic schwannomas.

PURPOSE: Stereotactic radiosurgery (SRS) is currently being investigated for treatment of acoustic schwannomas in patients who are not good surgical candidates. The vast majority of the available data is based on gamma knife-treated patients. We present the largest series of patients treated with linear accelerator-based SRS. METHODS AND MATERIALS: Thirty-two patients with acoustic schwannomas were treated with SRS between July 1988 and February 1993; follow-up ranged from 4-59 months. Age ranged from 34-88 years (mean, 62 years). The primary presenting symptom was hearing loss in 30 patients and dementia in two patients. Indications for SRS were age > 65 years (17 patients); recurrence after surgery (13 patients); and medical infirmity (two patients). Dose to the periphery of the lesion ranged from 10-22.5 Gy (mean, 15.5 Gy) specified at the 68-90% isodose line (mean, 80%). Collimator size ranged from 12-35 mm (mean, 23 mm), indicating that the sizes of the tumors were significantly larger than those reported in most gamma knife series. RESULTS: Follow-up magnetic resonance imaging (MRI) and/or computed tomography (CT) scans revealed the following at 1 year: tumor regression, 12 patients (63%); and no change, seven patients (37%). At 2 years, 11 tumors (73%) were smaller and four tumors (27%) were unchanged. At 3 years, seven patients (78%) had experienced tumor regression and two (22%) had no change. No patient experienced tumor progression after SRS. Seven patients (22%) suffered one or more treatment complications: new onset of 5th and/or 7th cranial nerve deficit (six patients), ataxia (two patients), and/or hydrocephalus necessitating VP shunt (two patients). CONCLUSION: Linear accelerator-based SRS provides excellent short-term local control and a relatively low incidence of complications for acoustic schwannomas. Our data compare favorably with results obtained with gamma knife-based SRS. Additional follow-up will be necessary to evaluate the long-term results of treatment.

Adult↗

Radiosurgical treatment of a hemangioblastoma: case report.

A hemangioblastoma of the fourth ventricle was treated with radiosurgery after attempts at surgical resection failed. No change in the size of the lesion has been seen in 2 years of follow-up, and the patient's neurological status remains normal. A brief review of the rationale for conventional radiation therapy and radiosurgery in the management of persistent/recurrent hemangioblastomas is presented.

Adult↗

Temporal characteristics of radiosurgical lesions in an animal model.

To characterize the temporal course of radiosurgical lesions, 19 cats were irradiated in an animal linear accelerator radiosurgical device. The animals were followed clinically and, at 3.5, 6, 12, 18, 23, 29, and 63 weeks, were studied with gadolinium-enhanced magnetic resonance (MR) imaging. They were then sacrificed after Evans blue dye perfusion, and gross pathological and histopathological studies were performed. Mild neurological deficits developed between 3.5 and 4.5 weeks, correlating with the onset of mass effect both grossly and radiographically and with the maximum amount of white matter edema on T2-weighted MR imaging and microscopic examination. Clinical improvement occurred within several weeks as these resolved. The lesions were of similar size at all time intervals. Gadolinium-enhanced MR imaging demonstrated lesions with peripheral areas of enhancement and central nonenhancing regions which correlated histologically with areas of vascular proliferation and radiation necrosis, respectively. In the early lesions at 3.5 and 6 weeks, necrosis and edema were predominant. From 12 to 29 weeks, an intermediate stage was observed, with resorption of the necrotic debris as evidenced by progressive cavitation and microglial response and by increased perilesional vascularity. At 63 weeks, resorption was still taking place, but gliosis and diminution of the vascular response were seen.

Animals↗

Delayed computed tomography contrast enhancement patterns in biopsy proven cases.

After a stereotactic brain biopsy of intracranial lesions, many neurosurgeons routinely obtain a noncontrast computed tomographic scan to rule out hemorrhage. We have observed there is often a significant delayed contrast enhancement on this postoperative scan, and the pattern of this enhancement frequently differs from the preoperative pattern. To assess these changes and to determine if they are related to lesion pathology or other clinical factors, the pre- and postoperative scans of 89 patients who underwent stereotactic biopsies were reviewed. Despite an average time delay of 153 minutes between scans, 81% of the lesions enhanced similarly or better on the postbiopsy image. One lesion enhanced only on the postoperative image, and in two cases, new lesions were seen postoperatively. Ring and other enhancing lesions tended to fill in with time, becoming homogeneous. The area of contrast enhancement increased in 83%. The borders of the lesions tended to become less sharp with time. No patterns of delayed enhancement, which give histologically definitive diagnostic information, were found. The tendency toward an increased area of contrast enhancement with time suggests that computed tomographic scans taken at the time of contrast injection may not show the true extent of the lesion. For patients undergoing computed tomography-guided stereotactic biopsies or radiosurgery of poorly enhancing lesions, the localization scan might be delayed after the administration of contrast medium to improve resolution and target selection.

Adult↗

Modifications based on computed tomographic imaging in planning the radiosurgical treatment of arteriovenous malformations.

Early in the course of treating arteriovenous malformations with radiosurgery, it was noted that the nidus isocenter and diameter, as identified by stereotactic angiography, often differed from that identified by stereotactic enhanced computed tomography (CT). To assess the sources of discrepancy between the arteriographic and CT representations of the nidus, dosimetry (from treatment records stored on an optical disk) was reviewed in 81 consecutive cases. In 44 cases, the isocenters differed by an average of 3.6 mm and the collimator size differed. Fourteen nidi were larger on CT (average, 2.6 mm), and 30 were smaller on CT (average, 4.0 mm). Overall, the angiographic and the CT nidus differed in 75% of the cases reviewed. Sources of error in the angiographic nidus determination included overlapping vessels, bony structures, fine filamentous arterioles, and irregular shapes.

Angiography, Digital Subtraction↗

LINAC radiosurgery: an animal model.

Fifteen cats were irradiated with an animal LINAC (linear accelerator) radiosurgery device. After 6 months, they were studied with gadolinium-enhanced magnetic resonance (MR) imaging, gross pathology after Evans blue perfusion, and histopathology. The lesion size was relatively constant in the cats receiving a dose of 7500, 10,000, 12,500, or 15,000 cGy to the 84% isodose line of a 1-cm collimator. The composition of the lesion correlated with dose: the lower-dose lesions were found histologically to contain areas of edema, demyelination, reactive gliosis, and vascular proliferation; the higher-dose lesions contained increasing amounts of hemorrhage and coagulative necrosis. The borders of the lesions were sharply demarcated from surrounding normal brain. Gadolinium-enhanced MR studies correlated well with areas of blood-brain barrier breakdown, as confirmed by areas of Evans blue staining. This model could serve as the basis for further studies of the biological effects of LINAC radiosurgery.

Animals↗

Radiosurgery for arteriovenous malformations.

Radiosurgery has been shown, in multiple reports using various radiosurgical methodologies, to be a safe and effective means of treating AVMs. The major drawback of this treatment method is that it does not provide, as does open surgery, immediate protection against re-hemorrhage. For those lesions in the appropriate size range (< 3.5 cm in diameter) which are not amenable to treatment with surgical and/or endovascular techniques, radiosurgery has become an accepted and valuable part of the neurosurgical treatment armamentarium.

Adolescent↗

Individual variation in locomotor behavior and maximal oxygen consumption in mice.

Individual differences in open-field activity and emotionality (number of defecations and urinations), voluntary wheel running, voluntary and forced maximal sprint running speed on a photocell-timed racetrack, swimming endurance, and maximal oxygen consumption (VO2max) were studied in 35 random bred male ICR mice. With the exception of latency in the open field and voluntary speed on a racetrack, all measurements were significantly repeatable on two successive trial days. Maximal oxygen consumption (corrected for body size) was positively correlated with amount of wheel running during each day of a 7-day test, and the correlation became stronger throughout the testing period; however, none of the daily correlations reached statistical significance. The first factor from a principal components (PC) analysis showed positive loadings (component correlations) for all measures of speed in the open field, for both voluntary and forced maximal speeds on the racetrack, and for VO2max, but a negative loading for emotionality. Wheel running and VO2max loaded positively on PC 2. Only swimming endurance loaded strongly on PC 3; this trait was uncorrelated with any other measure of physiology or behavior. These results suggest that measures of both voluntary and forced locomotor speed, as well as amount of voluntary wheel running, may be related to aerobic physiological capacities in untrained mice.

Animals↗

Limitations of angiographic target localization in planning radiosurgical treatment.

Planning radiosurgical treatment for cerebral arteriovenous malformations requires accurate definition of the true tridimensional size and shape of the nidus. Over- or underestimation of these parameters may result in undue irradiation of normal brain tissue or suboptimal irradiation coverage of the malformation leading to treatment failure. Angiography is not an ideal database for radiosurgery of arteriovenous malformations. Its shortcomings include planar representation of a tridimensional volume and simultaneous visualization of feeding arteries and draining veins overlapping with the nidus and obscuring its outline. Two illustrative clinical cases of these angiographic inadequacies are presented. Stereotactic, contrast-enhanced computed tomography may provide, in selected cases, better spatial definition of the nidus and superior anatomic detail for the final design of the radiosurgical isodose distribution.

Adult↗

Acute bilateral ophthalmoplegia secondary to cavernous sinus metastasis: a case report.

A case of a 60-year-old man with metastatic adenocarcinoma of the colon who developed bilateral ophthalmoplegia acutely is presented. Bilateral cavernous sinus metastasis was suggested by magnetic resonance imaging and proven by endoscopic sphenoidal biopsy. The patient was treated with radiotherapy (2000 cGy) with near resolution of his symptoms. This patient represents the first reported case of acute bilateral ophthalmoplegia resulting from hematogenous metastasis to both cavernous sinuses, diagnosed antemortem. A review of the more common causes of acute bilateral ophthalmoplegia is presented.

Adenocarcinoma↗

Linear accelerator radiosurgery for arteriovenous malformations.

Between May, 1988, and August, 1991, 80 patients with arteriovenous malformations (AVM's) were treated radiosurgically at the University of Florida. A mean dose of 1650 cGy was directed to the periphery of the lesion, which almost always corresponded to the 80% isodose line. The mean lesion diameter was 23 mm. Seventy-six patients were treated with one isocenter. Angiography, performed at 1 year after radiosurgery in 41 of the 48 eligible patients, revealed an overall complete thrombosis rate of 39%. The 1-year thrombosis rate was highest in those patients with relatively small AVM's. Angiography was performed at 2 years posttreatment in 21 of the 25 eligible patients, demonstrating an overall complete thrombosis rate of 81%. This incidence did not correlate with lesion size: that is, large lesions (up to 35 mm in diameter) seemed just as likely to thrombose. Two patients (2.5%) experienced hemorrhage at some time after radiosurgical treatment, and both recovered. Two patients (2.5%) have sustained mild, but permanent, radiation-induced neurological complications.

Adolescent↗

[Radiosurgery].

Explore the source record for details and available documents.

Brain↗

Linear accelerator radiosurgery.

During the past decade, multiple linear accelerator (LINAC)-based radiosurgical systems have been developed. By measuring beam energy, beam accuracy, and dose gradient, it has been possible to demonstrate that these systems may compare favorably with the gamma knife. Clinical results also appear quite comparable in terms of efficacy and safety. LINAC systems appear to be advantageous in terms of cost, variety of collimator sizes available, and currently available sophistication of computerized dose planning.

Brain Neoplasms↗

Linear accelerator radiosurgery at the University of Florida.

The University of Florida radiosurgical project began in 1986 with the following design criteria: the most accurate radiosurgical device possible, state-of-the-art computer hardware and software for dose planning, and a number of collimators sufficient to treat any lesion homogeneously. In this article we have reviewed how these goals have been met. Physical aspects of this device (accuracy, dose gradient, and dose-planning speed) as well as clinical results compare favorably with any other radiosurgical experience. We believe that LINAC radiosurgical systems are advantageous in terms of cost, variety of collimator sizes available, and currently available sophistication of computerized dose planning. In the near future, the development of conformal treatment may significantly change the entire field of radiosurgery by offering heretofore unobtainable dose plans for irregularly shaped lesions. In addition, LINAC systems may be adapted for stereotactically focused fractionated radiation therapy and for radiosurgical treatment of lesions elsewhere in the body. Accuracy and computer sophistication notwithstanding, we cannot emphasize strongly enough our belief that the least important determinant of radiosurgical results is the machine used to deliver the radiation. It is absolutely vital that all groups undertaking radiosurgery include neurosurgeons, radiation physicists, and radiation therapists who have spent considerable time studying and learning the myriad details necessary to produce consistently good results. All radiosurgical patients must be followed up carefully and studied so that we can learn how to better apply this technique. Only patients who are not candidates for conventional surgery should be treated radiosurgically, at least until much more is known about long-term success and complication rates. A patient never should be treated radiosurgically simply because the referring or treating neurosurgeon is uncomfortable with proven conventional procedures. All groups performing radiosurgery should strive to adhere to the highest possible standards. We are all responsible for verifying the adequacy of our radiosurgical systems. We are all responsible for selecting our patients well, treating them with a team approach that applies the latest available knowledge of our field, following up closely, and reporting our results honestly and thoroughly so that all can benefit. We owe this, at least, to our patients and to neurosurgery.

Adult↗

The role of stereotactic technology in the management of intracerebral hemorrhage.

Stereotactic techniques have been utilized for more than 40 years in clinical neurosurgical practice. There has been considerable experience with stereotactic techniques in the drainage of intracerebral hemorrhages, although its effectiveness remains controversial. Stereotactic craniotomy, often incorporating advanced computer guidance, is increasingly applied to effect complete resection of small, deep brain lesions. Radiosurgery has become a viable alternative for the treatment of arteriovenous malformations that, in most cases, are untreatable by other means. Currently, stereotaxis is a valuable part of the therapeutic armamentarium available to cerebrovascular neurosurgeons.

Cerebral Hemorrhage↗

Rapid determination of thalamic CT-stereotactic coordinates: a method.

The anterior and posterior commissures (AC; PC) are the most frequently used reference points for target determination in functional stereotactic surgery. Computerized tomography (CT) has been slow in replacing ventriculography for identification of these points, primarily because in most methods described to date, the AC/PC plane had to be identified by reformatted CT images or cumbersome mapping procedures. The authors describe their methodology for determination of functional CT-stereotactic coordinates using the Brown-Robert-Wells (BRW) stereotactic system, axial CT imaging, and a proportional method to rapidly scale standard stereotactic map coordinates to the diencephalic size of any individual patient. 1. CT gantry angulation coinciding with Twining's line allows rapid identification of the AC/PC plane on axial CT. 2. Determination of the AC/PC distance with the "measure distance" function of the scanner enables the surgeon to rapidly find the proportional coordinates for either V.O.P., V.im., or V.C. 3. This localization method takes little more time than a routine stereotactic biopsy. Its application is easy, demanding only a few minutes of CT-console time, employing the standard computer software available in every current CT scanner. The method was been successfully employed in 25 functional thalamic procedures.

Electric Stimulation↗