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C Lindquist

Publications and source records attributed to C Lindquist.

At least 55 records · Page 3Linked to original sources
PubMed1994

Stereotactic radiosurgery for tectal low-grade gliomas.

We report 7 cases with low-grade gliomas in the tectal region of the midbrain. This series started in 1979 and all tumors were treated by radiosurgery using the Leksell Gamma Knife. All cases were treated by using a single isocenter with the 14 mm collimator. Doses administered ranged from 14 to 35 Gy delivered to the 50-70% isodose line. All tumours but one responded to the treatment and disappeared or ceased growing. In the first two treated cases, the dose was chosen by the early experience from the AVM's, with 30 and 35 Gy as the peripheral dose. These cases developed severe radio-induced oedema with aggravating symptoms and permanent deficits. We conclude that radiosurgery is effective in the treatment of deeply located low-grade gliomas. Cases accepted for treatment should be carefully selected and the peripheral dose should not exceed 14Gy to avoid uncontrolled radio-induced changes.

Adolescent↗
PubMed1994

Intrinsic and extrinsic characteristics of human tumors relevant to radiosurgery: comparative cellular radiosensitivity and hypoxic percentages.

UNLABELLED: We have collected the in vitro x-ray radiation survival characteristics of 181 lines from 12 different classes of exponentially growing human tumor cells (sarcomas, lung cancers, colo-rectal cancers, medulloblastomas, melanoma, breast cancers, prostate cancers, renal cell cancers, grades III and IV brain tumors, ovarian, and head and neck cancers). This information was used to intercompare survival after single high doses of 20-40 Gy for each tumor line. Radiosensitivities could roughly be divided into two groups. The more radiosensitive group included: sarcoma, small-cell lung cancer, non-small cell lung cancer, colorectal cancer, medulloblastoma and melanoma. The more radioresistant group included breast, prostate, renal cell, primary brain tumors, ovarian tumors, and head and neck cancers. Using a model of a 3 cm diameter brain lesion containing about 1.4 x 10(9) oxic cells, the single doses calculated to reduce survival to 1 cell were: sarcoma and small cell lung cancers-22-23 Gy; melanoma-25 Gy; non-small cell lung and colorectal cancer-26 Gy; medullo-blastoma-28 Gy; breast, prostate, renal cell, primary brain tumors, ovarian tumors, and head and neck cancers-30-36 Gy. If, however, tumors contained on average 20 percent hypoxic cells, the dose needed for equivalent cell killing increased by about a factor of 2.6-2.8. Also, there was no correlation between the ranking of relative radiosensitivities of the various classes of tumor cells at high doses (as in radiosurgery) to the sensitivity at low doses (as in conventional fractionated radiotherapy). CONCLUSION: available information on the intrinsic radiosensitivity of human tumor cells indicates that meaningful differences exist among different histological classes of neoplasm that are relevant to the single high doses used in radioneurosurgery, and which could constitute a basis for "tailoring" the administered dose to the particular neoplasm. However, if intracerebral lesions contain a large number of hypoxic cells (e.g., 20%), this may constitute a significant problem.

Cells, Cultured↗
PubMed1994

Multiple intracranial arteriovenous malformations: a case report.

Multiple intracranial arteriovenous malformations are rare. There are a few cases in the literature with up to three malformations in one patient. A child with seven separate cerebral malformations is now described. There was no history of haemorrhage, but only of febrile seizures. The malformations were discovered at CT and verified at angiography. Six were selected for stereotaxic irradiation with the multi-cobalt unit. The seventh was considered too big for irradiation and suitable for surgery.

Cerebral Angiography↗
PubMed1994

A stereotactic guide for microsurgery. Technical note.

A stereotactic guide for microsurgery is presented. The guide consists of a weak helium neon laser projecting a red beam towards the target when the arc carrying the beam has been set on the Leksell frame according to the stereotactic co-ordinates of the target calculated on the pre-operative imaging studies. The device allows free manoeuverability of the operating microscope.

Brain Diseases↗
PubMed1994

Neurosurgical treatment for refractory obsessive-compulsive disorder: implications for understanding frontal lobe function.

A minority of patients with obsessive-compulsive disorder (OCD) have a chronic course and extreme disability, with symptoms refractory to pharmacological and psychological treatment. Considerable uncontrolled evidence suggests such cases may respond to neurosurgical intervention. The authors update current stereotactic procedures and their efficacy, safety, and side effect profiles. The design of an ongoing placebo-controlled trial of Gamma Knife capsulotomy for refractory OCD is outlined. Drug treatment of OCD may be assumed to affect a proposed functional imbalance between the frontal lobes and other parts of the brain. As for neurosurgical treatments, both the effects and side effects may be viewed as expressions of their influence on this functional imbalance.

Brain Mapping↗
PubMed1993

Gamma knife surgery of cerebral arteriovenous malformations: serial MR imaging studies after radiosurgery.

PURPOSE: To investigate the temporal sequence of post radiosurgery magnetic resonance imaging changes in cerebral arteriovenous malformations. METHODS AND MATERIALS: Eighteen patients were regularly followed up after gamma knife surgery. The follow-up intervals ranged from one day to 44 months. High signal lesion in or around arteriovenous malformations on T2-weighted magnetic resonance images corresponding to the treatment volume and developing after radiosurgery were defined as the adverse reaction of the irradiation. This high signal and the regression of arteriovenous malformations nidus after radiosurgery were evaluated. RESULTS: Adverse reaction of irradiation was observed in nine cases. Seven of them were symptomatic. The reactions presented as focal high signal in three cases and focal high signal with extension along the neural tracts in six cases. The reactions were seen either immediately after treatment (one case), between 3 and 14 months (seven cases), and 40 months after treatment (one case). The regression of the adverse reaction was observed to start 5 +/- 3 months after its appearance. Regression of the arteriovenous malformations' nidus was found in 16 cases. In two cases the AVMs became invisible on magnetic resonance images but the angiogram still demonstrated abnormal shunts. In another one case with angiogram showing total obliteration, the nidus was erroneously interpreted as incomplete obliteration on magnetic resonance images. CONCLUSION: It is concluded that magnetic resonance imaging is a sensitive in vivo method for detecting cerebral radiation injury. Magnetic resonance imaging offers a method for evaluating the regression of arteriovenous malformations' nidus, but the diagnosis of complete obliteration of the nidus after radiosurgery still relies on the angiogram.

Adolescent↗
PubMed1993

Maintenance of set force in anterior cruciate ligament grafts.

This study was undertaken to determine how accurately total graft force and load-sharing between graft segments could be set and maintained during augmented anterior cruciate ligament (ACL) reconstruction in the goat knee. Special procedures were developed to reduce the effect of tissue creep and to overcome difficulties in the setting of graft force. Five knees from goat cadavers were reconstructed using a bone-tendon-bone graft (PT) and a synthetic augmentation device (LAD). Prescribed levels of total graft force and load-sharing between the autograft and LAD were set under a standardized external joint load. Immediately after fixation, the set force declined an average of 9 and 3% in the LAD and PT, respectively. After three subsequent exercise sequences, the set forces fell from their initial level by an average of 25% for the LAD and 28% for the PT. An analysis of variance did not show the loss of force with exercise to be statistically significant. We conclude from this in vitro study that our method can be used to set forces in an ACL reconstruction with reasonable maintenance of load-sharing but that losses of approximately 30% of total graft force after exercise of the reconstructed joint are to be expected.

Animals↗
PubMed1993

Postradiation volume changes in gamma unit-treated cerebral arteriovenous malformations.

Postradiation changes in angiographically determined nidus volume were quantitatively studied in 22 arteriovenous malformation (AVM) cases treated by gamma unit radiosurgery. The postradiosurgical decrease was statistically significant by post-treatment year 2 (p < .05). In children, AVMs tended to be obliterated more quickly than in adults. Volume reduction was more rapid in nidi receiving 25 Gy or more than in those receiving less than 25 Gy (p < .01). However, there were no significant differences in nidus volume decrease between these two dose groups at the second or third postradiosurgical year. Dose response curves were obtained 1, 2, and 3 years following treatment.

Adolescent↗
PubMed1993

MEG localization of interictal epileptic focal activity and concomitant stereotactic radiosurgery. A non-invasive approach for patients with focal epilepsy.

Two patients with complex partial epilepsy and tumour of the temporal lobe scheduled for gamma knife radiosurgery were evaluated pre- and postoperatively by multichannel magnetoencephalography (MEG). Centers of epileptic dipole activity found preoperatively disappeared after the focal irradiation as did the epileptic seizures. Thus, to combine stereotactic MEG and gamma knife radiosurgery seems to be a non-invasive alternative to the conventional neurosurgery in focal epilepsy.

Adult↗
PubMed1993

Cost accounting the Gamma Knife.

The cost of the three dominant technologies for delivering radiosurgery to the brain are compared. Included in the analysis is the cost of the equipment and labor costs for each procedure. Once a unit is treating more than 100 patients per year the Gamma Knife becomes the most cost-effective technology by a factor of almost 100%. These findings are primarily a result of the greater labor input required for alternate technologies.

Brain Neoplasms↗
PubMed1993

Gamma Knife surgery for cerebral metastases. Implications for survival based on 16 years experience.

Our experience with radiosurgery of brain metastases is based on 160 patients with 235 tumors treated over a 16-year period. In this material, 94% growth control was achieved. Radiosurgery appears to be an effective, low-morbidity substitute for surgical resection followed by whole brain radiotherapy and even indicated for multiple metastases and distant new tumors. More patients receive an effective treatment with less neurologically related deaths.

Brain↗
PubMed1993

Determination of target point magnification rate on stereotactic angiography for radiosurgery--technical note.

We describe here a new method of calculating the target point magnification rate for radiosurgery by stereotactic angiography using a Leksell frame. As the distance (D) between the x-ray focus and the film plane is constant in each facility, the magnification rate (M) is determined by the equation: M = D/[D/Mp + t], where Mp is the magnification rate of the proximal (to the x-ray focus) frame projected on the film plane and t is the distance between the proximal frame plane and the target point. The t value is given by the three-dimensionally determined stereotactic coordinates of the target point. Only the Mp value on the stereotactic angiogram must be measured. This method is theoretically more correct and has less risk of human error than the conventional, graphically determined method which necessitates measuring both the distal and proximal frame magnification rates. Furthermore, the inherent theoretical error of the conventional method is largest around the frame center, which is frequently selected as the target point for radiosurgical treatment, possibly causing serious error in accurate dose planning.

Angiography↗
PubMed1993

Radiosurgery for venous angiomas.

Radiosurgical treatment with the gamma knife for venous angiomas was used as an alternative to microsurgical removal in order to avoid abrupt cessation of venous drainage, which may be shared by the venous angioma and important parts of the brain. Thirteen cases of venous angioma were treated between 1977 and 1991. In two cases cavernous angiomas were also present and in one case a distant arteriovenous malformation (AVM) was also found. In two cases the angioma shared the venous drainage with an adjoining AVM; this is the first description of such pathology. For venous angiomas irradiation was prescribed to cover at least the convergence of the medullary veins. For AVM's close to a venous angioma the treatment was exclusively prescribed to the AVM nidus. After treatment, complete obliteration of the venous angioma was observed in one case, partial obliteration was observed in three cases, and five venous angiomas were unaffected by the treatment. Undue effects of radiation occurred in four cases: one focal edema and three radionecroses. Extirpation of the radionecrotic tissue 6 months after radiosurgery was necessary in one case. In the other three cases, the venous angioma was observed to be completely or partially obliterated, or unaffected by the treatment (one case each). In two cases of combined AVM and venous angioma, complete obliteration of the treatment AVM nidus was obtained. It is concluded that radiosurgery for venous angioma, although conceptually attractive, still does not fulfill the rigid criteria of minimal risk which must be set for the treatment of a lesion with a benign natural history.

Adult↗
PubMed1993

High recurrence rate following aspiration of colloid cysts in the third ventricle.

Sixteen patients treated between 1969 and 1989 for a colloid cyst of the foramen of Monro by stereotactically guided aspiration (not stereotactic extirpation) were evaluated to assess the long-term outcome of the procedure. Thirteen of these patients required reoperation due to an acute comatose state, failure to achieve permanent reduction of the cyst, or symptomatic hydrocephalus. Of these 13, six were treated twice and two were treated three times by stereotactic aspiration. Five patients underwent microsurgical extirpation and three had a shunt placed following a failed aspiration. Failure of the first procedure was detected within the first 2 months after treatment in eight patients and after more than 6 years in seven. Following stereotactic aspiration, three patients experienced a temporary memory deficit and confusion and one patient suffered a central pain syndrome. Eleven of the 26 procedures were followed by a recurrence 6 to 15 years after treatment; seven recurrent cysts were detected after more than 8 years. Of the patients with recurrences, three did not undergo repeat surgery but showed an increase in cyst size at the latest follow-up examination. It is suggested that radical removal by open or stereotactically guided microsurgery is the method of choice since stereotactic aspiration fails to offer a radical or permanent treatment for colloid cysts of the third ventricle.

Adolescent↗
PubMed1993

Combined embolization and gamma knife radiosurgery for cerebral arteriovenous malformations.

In a study of 46 patients with cerebral arteriovenous malformations (AVMs) the value of combining embolization and gamma knife radiosurgery was assessed. In 35 patients with large grade III to V AVMs (Spetzler-Martin system) staged combined treatment was planned. In 11 patients, radiosurgery complemented embolization for a residual AVM. The number of embolization sessions ranged from 1 to 7 (median 2). Twenty-six patients needed multiple embolization sessions. In 28 patients the grade of AVMs decreased as a result of embolization. In 16 patients collateral feeding vessels developed after embolization which made delineation of the residual nidus difficult. The time lag between the last embolization and radiosurgery ranged from 1 to 24 months (median 4). Nineteen of 35 large grade III to V AVMs were possible to treat by radiosurgery following embolization. In the 46 patients complications occurred in 9 from embolization and in 2 from radiosurgery. Two patients had transient and 9 had permanent neurologic deficits. It is concluded that embolization facilitates radiosurgery for some large AVMs and therefore this combined treatment has a role in the management of AVMs.

Adolescent↗
PubMed1993

Target delineation in radiosurgery for cerebral arteriovenous malformations. Assessment of the value of stereotaxic MR imaging and MR angiography.

A study of 6 selected arteriovenous malformation (AVM) patients was performed to investigate the feasibility of delineating an AVM on MR images and to compare the AVM volume outlined on different images. Conventional stereotaxic angiograms, stereotaxic MR images and MR angiograms using several different pulse sequences were obtained prior to radiosurgery. Treatment plans were made from the conventional stereotaxic angiograms. These plans were then transferred to a separate dose planning computer which displayed the MR images with the superimposed isodose lines. The radiated volumes of AVM and brain tissue were measured from these MR images. Last, an assessment was made of the radiation volume needed for an appropriate treatment of the AVM if the treatment plan was made from the MR images rather than from the conventional stereotaxic angiogram. It was possible to delineate medium and large size AVM nidi on stereotaxic MR images based on an integration of information obtained from various pulse sequences. The estimated volumes of the AVM nidi were found to be larger on the conventional stereotaxic angiograms than on the stereotaxic MR images. Consequently, a dose plan based on a conventional stereotaxic angiogram would result in a higher integral dose to the brain with the same target dose. By using reliable MR information it is expected that the volume of brain exposed to radiation could be decreased and the adverse effects of stereotactic radiosurgery for AVM thereby minimized.

Adult↗
PubMed1992

Biomechanical effect of a two-segment anterior cruciate ligament graft with separate femoral attachments and differing levels of prescribed load sharing.

The objective of this study was to analyze the biomechanical effect of varying the level of prescribed load sharing between two segments of an anterior cruciate ligament (ACL) graft, and of separating the femoral attachments of these segments. Total anterior-posterior (AP) laxity was measured using an instrumented spatial linkage. Forces in graft segments were measured using buckle transducers. The two-segment graft was formed using the middle third of the patellar tendon with bone blocks and a synthetic augmentation device. Proximal fixation was obtained using a fixture which allowed changing the individual locations of the femoral attachments of the tendon and augmentation segments. Distal fixation was achieved using a force-setting device which allowed the loads in each segment to be set to prescribed levels. Total graft force, load sharing, and total AP laxity were recorded during the application of 100-N AP tibial loads at 0 degrees, 30 degrees, 60 degrees, 90 degrees, and 110 degrees flexion, for various combinations of load sharing set at extension and locations of femoral attachment sites. The load sharing, total graft force, and AP laxity during AP loading at the five test flexion angles were not significantly affected by changing the prescribed level of load sharing set at extension for a given femoral attachment configuration. However, varying the separate hole locations of the graft segments for a given level of load sharing significantly affected load sharing, total graft force, and AP laxity. If the tendon graft was located posteriorly (on the medial surface of the lateral femoral condyle) and the augmentation segment proximally, the augmentation carried a greater portion of the total force in flexion. If the augmentation segment was changed to a more posterosuperior location and the tendon posteroinferior, the tendon carried a higher percentage of the total force in flexion. AP laxity in most reconstruction states was significantly greater than in the normal joint with an intact ACL. The nature of the load sharing between the graft segments under AP tibial load over the flexion range can be controlled by the appropriate choice of the segments' femoral attachment locations.

Analysis of Variance↗