[Gamma knife versus stereotactic linear accelerator irradiation. Implementation, clinical results and cost-benefit relations].
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Brain Neoplasms↗
Biomedical subjects
B Wowra
Publications and source records attributed to B Wowra.
[Profile of ambulatory radiosurgery with the gamma knife system. 1: Method and multicenter irradiation concept].
Radiosurgery represents a minimally invasive radiologic method for the treatment of intracranial tumours and arteriovenous malformations. In 1994 the radiosurgical device 'Leksell Gamma Knife' (LGK) was installed in a dedicated logistic environment for outpatient treatments. High quality requirements have to be met for radiosurgery. The target point accuracy taking into account the whole system was shown to be reliably below 0.5 mm whereas the spatial therapeutic resolution was 0.035 cm3. Quality parameters of the dose plan were evaluated for the first 500 consecutive treatments. These values and examples of dose plans were used to emphasize the advantages of the treatment principle with multiple isocenters. An analysis of data in the literature revealed that there is no uniform standard of treatment available in radiosurgery. A highly significant correlation between a risk prediction model for the stereotactic linear accelerator on the one hand and a different model for the LGK on the other could be shown. This result could be helpful in order to proceed towards a more uniform treatment standard in radiosurgery and to improve overall treatment results.
Ambulatory Surgical Procedures↗
[Profile of ambulatory radiosurgery with the gamma knife system. 2: Report of clinical experiences].
Gamma Knife radiosurgery (GKRS) was applied in 500 consecutive treatments for 445 patients within 2 years. Indications were arterio-venous malformations (93 patients), schwannomas of cranial nerves (75 patients), meningiomas (79 patients; 73 of the tumors involving the skull base), pituitary adenomas (40 patients), craniopharyngiomas (13 cases), gliomas (13 cases), rare indications (12 cases), and brain metastases (126 patients). In arterio-venous malformations two complications were observed whereas two other patients underwent surgery due to intracranial hemorrhage in the latent period after GKRS. In all cases follow-up with MRI showed evidence of an active obliteration process. Out of 24 patients with a follow-up over 1 year, angiography revealed complete obliteration in 9 patients so far. A partial obliteration was evidenced by MRI in 15 cases. In benign tumors (meningiomas and vestibular schwannomas) tumor control rates of 88% and 89% were achieved, respectively. Treatment related side effects were mild and rare; no facial palsy occured after primary Gamma Knife treatment. GKRS was particularly effective in inoperable skull base meningiomas. Cerebral metastases were controlled in 89.5% by a single Gamma Knife treatment. The mean survival period was 11.8 months. In patients receiving a single Gamma Knife treatment the mean survival time was 9.1 months. For patients undergoing multiple (up to 5) sessions of GKRS (because of new tumors) the mean survival period was 17.2 months. MRI showed evidence of adverse radiation reactions in 10/124 patients (8.1%) which were symptomatic in 3 patients (0.8%). The results obtained in patients with cerebral metastases emphasize that GKRS alone is as effective as the combined treatment of these lesions by surgery and fractionated radiotherapy. Our results demonstrated an attractively high therapeutic gain factor of Gamma Knife treatment in key indications of radiosurgery.
Ambulatory Surgical Procedures↗
The role of high-dose, single-fraction irradiation in small and large intracranial arteriovenous malformations.
PURPOSE: Radiosurgery with external beam irradiation is an accepted treatment for small intracranial vascular malformations. It has been proven effective and safe for lesions with volumes of less than 4 cc. However, there is only some limited clinical data for malformations of grade 4 and grade 5, according to Spetzler and Martin. METHODS AND MATERIALS: At the Heidelberg radiosurgery facility equipped with a linear accelerator, 212 patients with cerebral arteriovenous malformations have been treated since 1984. Thirty-eight percent of the arteriovenous malformations treated were classified inoperable, 14% grade 5, 19% grade 4, and 29% grades 1-3. Radiation doses between 10 and 29 Gy were applied to the 80% isodose contour. RESULTS: Above a threshold dose of 18 Gy, the overall obliteration rate was 72%. After 3 years, the obliteration rates were 83% with volumes of less than 4.2 cc, 75% with volumes of up to 33.5 cc, and 50% with volumes of up to 113 cc. Of the patients presenting with seizures and paresis, 83% and 56%, respectively, showed improvement, which correlated with the degree of obliteration. After a follow-up period of up to 9 years, the rate of radiation-induced severe late complications was 4.3%. In grade 5 lesions, the risk of side effects was 10%. No serious complications occurred if a maximum dose of less than 25 Gy was applied to treatment volumes of less than 33.5 cc. CONCLUSION: The success of stereotactic high-dose irradiation of arteriovenous malformations depends on the dose applied. The incidence of radiation-induced side effects increased with the applied dose and treatment volumes. From our experience, doses of less than 25 Gy and treatment volumes of up to 33.5 cc are safe and effective. In the future, new techniques of radiosurgery with linear accelerators and dynamically reshaped beams will allow us to apply homogenous dose distributions. Additional use of magnetic resonance angiography for 3D treatment planning will help to identify the nidus more easily.
Adolescent↗
Mood changes after surgery for tumors of the cerebral cortex.
OBJECTIVE: To identify cortical lesion sites associated with particular mood states. DESIGN: A prospective study of patients with tumors affecting the cerebral cortex. The patients were examined neuropsychologically 1 to 5 days preoperatively and 2 to 10 days, several months, and several years postoperatively. Only data from the preoperative and the first postoperative examination were considered in this report. SETTING: Neurosurgical department of the University of Heidelberg (Germany). PATIENTS AND SUBJECTS: A consecutive sample of 141 patients with brain tumors (84 female and 57 male) with cortical lesions caused by microsurgical tumor resection; 29 clinical control patients (having undergone surgery for slipped disks); and 18 normal control subjects. MAIN OUTCOME MEASURE: Preoperative and postoperative mood state as measured with an adjective checklist. RESULTS: (1) Patients with lesions of the ventral frontal cortex or lesions of the temporoparietal cortex reported postoperatively significantly (P < .01) worse mood states (anxiety/depression, irritability/anger, fatigue) than did patients in the other lesion and control groups. (2) A more detailed lesion analysis revealed that lesions of heteromodal frontal or parietal association cortexes, combined with paralimbic lesions, were responsible for the negative mood states. Lesions of the sensorimotor cortexes ameliorated the negative effects of heteromodal and paralimbic lesions. (3) Lesion laterality did not influence the mood states. CONCLUSIONS: Heteromodal cortexes may be especially concerned with emotionally relevant operations. A loss of these functions deprives limbic structures of one of their main sources of input and is therefore likely also to produce changes in feelings, that is, emotional states.
Adult↗
Long-term follow-up for brain metastases treated by percutaneous stereotactic single high-dose irradiation.
Surgery is considered the treatment of choice for solitary brain lesions, and radiation therapy is indicated for metastases only in vital or sensitive regions that cannot be excised without risk of disabling neurologic defects. In these cases, radiosurgery may be an alternative to conventionally fractionated radiation therapy. At the Heidelberg linear accelerator-based radiosurgery facility, 69 patients were treated for 102 inoperable brain metastases. The primary tumor sites included non-small cell lung carcinoma (n = 24), renal cell carcinoma (n = 14), melanoma (skin) (n = 14), colorectal carcinoma (n = 6), carcinoma of unknown primary (n = 4), and others (n = 7). Eleven patients were treated for relapse after surgery or after conventional whole-brain irradiation. The doses at the isocenter varied from 15-50 Gy (mean, 21.5 Gy). Ten patients with multiple metastases received a planned combination of whole-brain irradiation plus a single boost of 15 Gy. The median survival time for the entire group was 6 months, with a 1-year-survival of 28.3%. Factors associated with significant improvement of survival were brain metastases without other metastatic disease and good response to radiation therapy. Five of 22 patients (22.9%) with metastases located only in the brain survived longer than 2 years. An improvement in neurologic function was found in 81% within a period of 3 months. With imaging techniques, complete remission was found in 20%, partial remission in 35%, stable disease in 40%, and relapse in 5%. The authors concluded that radiosurgery is an effective and safe therapy for brain metastases. It can be applied as primary treatment, as boost in combination with whole-brain irradiation, or as treatment for patients with relapse in a previously irradiated field.
Adult↗
Titanium Riechert head ring for MR stereotaxy. Technical note.
Magnetic Resonance has become the preferred neuro-imaging modality. To fully take advantage of the high anatomical resolution the Riechert stereotactic system was adapted for use in Magnetic Resonance Stereotaxy. The head ring which until recently was made of an aluminum alloy has been replaced by an unsegmented head ring of pure titanium without changing the dimensions and fixation mode. No significant misregistration due to eddy currents has been noticed. Minor distortion induced by the titanium head ring can be corrected mathematically. Thus the geometric information is limited only by the pixel resolution of the MR image.
Artifacts↗
Interstitial irradiation of a large, low grade ependymoma with stereotactically implanted iodine-125 seeds. Case report.
In this case report a patient with a large intraventricular benign ependymoma is presented. The tumour was treated with stereotactically implanted Iodine-125 seeds and interstitial irradiation. Extension (diameter: 6.5 cm) and volume (112.5 ml) of the lesion caused the application of an unusually low dose (tumour surface dose: 40 Gy). The tumour shrank significantly within a few weeks. Follow-up at nearly 5 years shows the patient to be tumour free.
Adult↗
Memory disturbances following anterior communicating artery rupture.
Thirty patients with lesions due to the rupture and repair of an aneurysm of the anterior communicating artery were compared neuropsychologically with 27 patients with ruptures but no lesions and 30 normal control subjects. Patients with combined lesions in the basal forebrain and striatum (n = 5), or basal forebrain, striatum, and ventral frontal cortex (n = 7), had severe memory deficits, whereas patients with lesions in the basal forebrain (n = 7) or the striatum (n = 5) alone showed virtually no deficits. Patients with lesions of the basal forebrain and ventral frontal cortex together (n = 6) showed mild memory deficits. In contrast to the memory effects, emotional changes were most pronounced in patients with striate lesions alone. Basal forebrain or ventral frontal lesions ameliorated rather than aggravated the emotional effects of striate lesions. It is suggested that the basal forebrain and the striatum form links of different pathways related to mnemonic information processing. Both systems may be able to compensate for a dysfunction of the other, but lesions of both systems together may lead to strong and unrecoverable memory deficits.
Affect↗
Intraneoplastic application of metrizamide-containing liposomes: kinetic studies with computed tomography.
Liposomes may serve as drug carriers not only for systemic chemotherapy but also for intraneoplastic drug therapy because they show a sustained drug release. In the present study, the in vivo kinetics of intraneoplastic deposits of large multilamellar vesicles containing metrizamide was followed up in a rat tumor model with computed tomography. The influence of four different lipid compositions on the retardation capacity of large multilamellar liposomes was investigated. By comparing the dynamic data of X-ray attenuation and volume of liposome deposits, a rank order for the in vivo stability of metrizamide containing multilamellar vesicles could be established: the least stable liposomes were made of pure dimyristoyl-phosphatidyl-choline, the most stable type was made of equimolar parts of stearoyl-palmitoyl-phosphatidyl-choline and cholesterol. Of intermediate stability were liposomes made of equimolar parts of dimyristoyl-phosphatidyl-choline and cholesterol, and those made of pure stearoyl-palmitoyl-phosphatidyl-choline. The addition of 50% cholesterol increased the membrane stability of both dimyristoyl-phosphatidyl-choline and stearoyl-palmitoyl-phosphatidyl-choline liposomes. No diffusion of large multilamellar liposomes away from the injection site was observed. The in vivo stability of the liposomes was considerably less than that observed in vitro, suggesting active degradation processes. It is concluded that large, multilamellar liposomes may be suitable carriers for intraneoplastic chemotherapy. The present model is easily adaptable to be transferred into clinical conditions, and may allow direct monitoring of intraneoplastic liposome-mediated chemotherapy in human brain tumors.
Animals↗
Correction of spatial distortion in magnetic resonance angiography for radiosurgical treatment planning of cerebral arteriovenous malformations.
A treatment planning system based on magnetic resonance (MR) angiographic imaging data for the radiosurgery of inoperable cerebral arteriovenous malformations is reported. MR angiography was performed using a three-dimensional (3D) velocity-compensated fast imaging with steady-state precession (FISP) sequence. Depending on the individual MR system, inhomogeneities and nonlinearities induced by eddy currents during the pulse sequence can distort the images and produce spurious displacements of the stereotactic coordinates in both the x-y plane and the z axis. If necessary, these errors in position can be assessed by means of two phantoms placed within the stereotactic guidance system--a "2D-phantom" displaying "pincushion" distortion in the image, and a "3D-phantom" displaying displacement, warp, and tilt of the image plane itself. The pincushion distortion can be "corrected" (reducing displacements from 2-3 mm to 1 mm) by calculations based on modeling the distortion as a fourth order 2D polynomial. Displacement, warp, and tilt of the image plane may be corrected by adjustment of the gradient shimming currents. After correction, the accuracy of the geometric information is limited only by the pixel resolution of the image (= 1 mm). Precise definition of the target volume could be performed by the therapist either directly in the MR images or in calculated projection MR angiograms obtained by a maximum intensity projection algorithm. MR angiography provides a sensitive, noninvasive 3D method for defining target volume and critical structures, and for calculating precise dose distributions for radiosurgery of cerebral arteriovenous malformations.
Humans↗
[Stereotactic convergent-beam irradiation: its current prospects based on clinical results].
"Radiosurgery" is the term for a special concept in radiotherapy. It describes a percutaneous, stereotactically guided irradiation delivering a single high dose with collimated narrow beams. The precise stereotactic localization of the target point and a steep dose gradient outside the target volume allow the administration of high doses to a lesion without damage to adjacent normal tissue. Risk of necrosis, due to a dose volume relationship represents the limits of radiosurgery. Units for radiosurgery were designed at Stockholm using multiple external cobalt-60-gamma sources, at Boston operating with protons of a cyclotron, at Berkeley operating with helium ions accelerated by a synchrocyclotron. An attractive alternative to these complicated and expensive facilities is the use of a modified linear accelerator. At the German Cancer Research Center in Heidelberg such a system was developed and has been available for the treatment of patients since 1984. Though, data of over 100,000 patients with vascular malformations and cancer disease are available worldwide, the indication for this therapy is validated only for a minority of entities. In cases of inoperable arteriovenous malformations favourable results in achieving obliteration range between 60% and 100% were obtained. Median survival for solitary brain metastases with controlled, extracerebral tumor diseases were between nine and twelve months. Up to now, advantages of stereotactic irradiation for benign tumor masses could not be proven. Therefore, randomized trials should be initiated in this field, considering decisive improvements in local tumor control with techniques of microsurgery and fractionated, postoperative radiotherapy during the last few years.
Brain↗
Three-dimensional time-of-flight MR-angiography and the surgical indication of brainstem cavernomas.
This study was designed to assess the diagnostic value of 3D time-of-flight MR-angiography in cerebral cavernomas. In seven patients, nine out of ten cavernomas were removed by microsurgery. While MR-angiography demonstrated well branches of brain arteries adjacent to the lesions, no flow signal in the vascular malformations was observed. On the other hand, there was a high intensity signal induced by methaemoglobin in those three patients with brainstem cavernomas who had experienced a significant bleeding attack seven months prior to admission. It had a spotted appearance in MR-angiography with volumes of the largest spots around 1.8 cm3. It is suggested that this spot signal could be used as a path marker for the surgical approach in brainstem cavernomas.
Adult↗
[MR tomography and MR angiography in cerebral arteriovenous malformations].
Av malformations are cerebral abnormalities with a high risk of bleeding. The role of MRI and MR angiography (MRA) for demonstrating these congenital vascular malformations has been studied. It has been shown that MRI/MRA can provide a rapid and certain diagnosis. MRA can demonstrate arteries to the second set of branches beyond the main cerebral vessels. It has the advantage of being able to produce rapidly and noninvasively 3-D images and, unlike conventional angiography, it can be repeated at will. The disadvantage is the limited special resolution and the difficulty in distinguishing between arteries and veins.
Adolescent↗
[Aspergillosis of the central nervous system in glioblastoma multiforme].
A 45 year-old male with a butterfly glioma received stereotactic biopsy for histologic confirmation of the clinical diagnosis. Microscopically, the results were controversial since some biopsy specimens showed distinct inflammatory changes, while others displayed typical features of a malignant glioma. The patient died four days after the stereotactic approach due to therapy-resistant intracranial pressure rise. In addition to a large butterfly glioblastoma originating from the frontal part of the corpus callosum, neuropathologic examination revealed a mycotic encephalitis with formation of numerous fungi-containing inflammatory foci in all parts of the brain and in the glioma. General autopsy disclosed pulmonary aspergillosis as the source of the inflammatory spread. A previous steroid medication over several weeks for treatment of increased intracranial pressure may be considered as an important factor in the origin of the pulmonary aspergillosis complicating the butterfly glioma.
Aspergillosis↗
Interstitial chemotherapy of experimental gliomas.
Two new approaches of interstitial (intratumoral) chemotherapy of gliomas are presented. Using s.c.-transplanted rat gliomas (G616) the therapeutic activity of biologically degradable polylactide rods as carriers for methotrexate was investigated. Carrier-mediated intratumoral chemotherapy was superior both to a systemic treatment and an intratumoral treatment with the free drug. The activity of the alkyllysophospholipids Et-18-OCH3 and BM 41.440 and of the alkylphosphocholine He-PC was investigated in a human glioma xenograft (T 406). All three compounds were highly active following intratumoral administration.
Animals↗
Stereotactic single high dose radiation therapy of benign intracranial meningiomas.
Seventeen patients with intracranial meningiomas were treated with single high dose irradiation at the German Cancer Research Center in Heidelberg. Indications for radiosurgery included unresected tumors, gross disease remaining despite surgery, and recurrences. Therapy was carried out by a technique using multiple non-coplanar arc irradiations from a 15 MeV linear accelerator. This technique coupled with secondary tungsten collimators allowed a high concentration of the dose in the target volume with an extremely steep dose gradient at the field borders. The patients were treated with a single irradiation dose ranging from 10 to 50 Gy (mean of 29 Gy). Four of 17 patients died: one death was tumor-related and not attributable to the treatment, one died of a treatment related complication, and two patients died of intercurrent diseases. The remaining 13 of the 17 patients with a median follow-up time of 40 months have no evidence of tumor relapse. Late severe side effects include five patients with a large area of brain edema, three of which were concurred with tumor necrosis. We conclude from these initial data that single high doses of irradiation concentrated to the tumor volume by stereotaxic methods can achieve local tumor control. It is also clear from these data that the effective therapeutic dose range must be better defined.
Adult↗
Incidence of late radiation necrosis with transient mass effect after interstitial low dose rate radiotherapy for cerebral gliomas.
Late radiation necroses constitute a hazard in low dose rate interstitial irradiation for inoperable gliomas. An incidence of 40% (8/20 patients) was found after permanent implantation of Iodine-125 seeds. This finding may even underestimate the real frequency, because follow-up of unaffected patients was shorter than in patients with radiation necrosis. The necrotic reactions caused a transient mass effect, which lead to a significant deterioration of performance scores. Further manifestations of late delayed radiation damage were observed in two patients. The occurrence of radiation necrosis was correlated with total radiation dose, amount of implanted radioactivity, and with velocity of tumour shrinkage. A mechanism underlying the development of radiation necrosis is proposed: A rapid shrinkage of tumour after interstitial Iodine-125 implantation may cause a significant irradiation of surrounding brain tissue, which was initially lying outside the target volume. Since most patients affected by radiation necrosis were children or adolescents, the risk of radiation damage should be minimized. This could probably be achieved either by reduction of irradiation dose, or by using temporary implants of Iodine-125.
Adolescent↗