Direct visualization of intracranial tumours in stereotactic and angiographic films by computer calculation of longitudinal CT-sections: a new method for stereotactic localization of tumour outlines

Delineation of brain tumor extent with [11C]L-methionine positron emission tomography: local comparison with stereotactic histopathology

PURPOSE

Methyl-[11C]L-methionine ([11C]MET) positron emission tomography (PET) in brain tumors reflects amino acid transport and has been shown to be more sensitive than magnetic resonance imaging in stereotactic biopsy planning. It remains unclear whether the increased [11C]MET uptake is limited to solid tumor tissue or even detects infiltrating tumor parts.

EXPERIMENTAL DESIGN

In 30 patients, a primary or recurrent brain tumor was suspected on magnetic resonance imaging. Patients were investigated with [11C]MET-PET before stereotactic biopsy. The biopsy trajectories were plotted into the [11C]MET-PET images with a newly designed C-based software program. The exact local [11C]MET uptake was determined within rectangular regions of interest of 4 mm in width and length aligned with the biopsy specimen. Individual histologic specimens were rated for the presence of solid tumor tissue, infiltration area, and nontumorous tissue changes.

RESULTS

Receiver operating characteristics analysis demonstrated a sensitivity of 87% and specificity of 89% for the detection of tumor tissue at a threshold of 1.3-fold [11C]MET uptake relative to normal brain tissue. At this threshold, only 13 of 100 tumor positive specimen were false negative mainly in grade 2 astrocytoma. In grade 2 astrocytoma, mean [11C]MET uptake in the infiltration area was significantly higher than in solid tumor tissue (P < 0.003).

CONCLUSIONS

[11C]MET-PET detects solid parts of brain tumors, as well as the infiltration area at high sensitivity and specificity. High [11C]MET uptake in infiltrating tumor of astrocytoma WHO grade 2 reflects high activity in this tumor compartment. Molecular imaging, with [11C]MET, will guide improved management of patients with brain tumors.

Imaging-guided convection-enhanced delivery and gene therapy of glioblastoma

In a prospective phase I/II clinical study, we treated eight patients suffering from recurrent glioblastoma multiform with stereotactically guided intratumoral convection-enhanced delivery of an HSV-1-tk gene-bearing liposomal vector and systemic ganciclovir. Noninvasive identification of target tissue together with assessment of vector-distribution volume and the effects of gene therapy were achieved using magnetic resonance imaging and positron emission tomography. The treatment was tolerated well without major side effects. In two of eight patients, we observed a greater than 50% reduction of tumor volume and in six of eight patients focal treatment effects. Intracerebral infusion of contrast medium before vector application displayed substantial inhomogeneity of tissue staining indicating the need of test infusions to monitor the mechanical distribution of vectors. Visualization of therapeutic effects on tumor metabolism and documentation of gene expression using positron emission tomography indicated that molecular imaging technology appears to be essential for the further development of biological treatment strategies.

Stereotactic linear accelerater-based radiosurgery for the treatment of patients with glomus jugulare tumors

BACKGROUND

The optimal treatment for patients with glomus jugulare tumor (GJT) of the skull base remains controversial. Surgical excision is associated with a high incidence of cranial nerve injury, decreased quality of life, and high mortality. Fractionated radiotherapy is used to control the majority of these tumors, but disadvantages are a prolonged therapy interval and exposition of adjacent brain tissue to irradiation. The authors present the results of a study on 12 of 14 consecutively admitted patients who were treated using linear accelerator-based radiosurgery (LINAC-RS), an innovative method for the treatment of GJT.

METHODS

From May 1991 to March 2001, 14 patients with GJT were treated with stereotactic LINAC-RS for continued growth of tumor or of remaining tumor after surgery. Twelve patients (9 women and 3 men; age range, 28-71 years; median age, 59 years) with a median follow-up of 4 years (range, 0.8-9,0 years), were selected for retrospective analysis. A median single dose of 15 grays (Gy; range, 11-20 Gy) was applied to the surface of the tumor.

RESULTS

After undergoing LINAC-RS, 8 of 12 patients (67%) reported partial or complete subjective improvement, whereas complaints remained unchanged in 4 patients (33%). Neurologic status improved in 3 patients (25%) and remained unchanged in 8 patients (67%). Magnetic resonance images showed tumor shrinkage in 8 patients (67%) and no further progression in 4 patients (33%).

CONCLUSIONS

LINAC-RS is an effective and safe therapy for patients with GJT and may be used as an alternative to surgical resection. Compared with fractionated radiotherapy, LINAC-RS has some advantages. However, to clarify the question of long-term tumor control, longer observation times are required.

Bilateral high-frequency stimulation in the subthalamic nucleus for the treatment of Parkinson disease: correlation of therapeutic effect with anatomical electrode position

OBJECT

The goal of this study was to relate the degree of clinical improvement and that of energy consumption to the anatomical position of electrode poles used for long-term stimulation.

METHODS

The authors conducted a retrospective analysis of 15 consecutive patients in whom targeting of the subthalamic nucleus (STN) had been performed using ventriculography, three-dimensional (3D) magnetic resonance (MR) imaging, and 3D computerized tomography, together with macrostimulation and teleradiographic control of the electrode position. In these patients the follow-up period ranged from 6 to 12 months. Postoperative improvement in contralateral motor symptoms, which was assessed by assigning a lateralized motor subscore of the Unified Parkinson's Disease Rating Scale (UPDRS), and stimulus intensity required for optimal treatment results were correlated with the intracerebral position of the active electrode pole. Bilateral high-frequency stimulation of the STN improved the UPDRS motor score during the medication-off period by an average of 60.5% compared with that at baseline. Repeated transfer of stereotactic coordinates from postoperative teleradiography to treatment-planning MR images documented the proper localization of the most distal electrode pole (pole 0) in the targeted STN. Nevertheless, in most cases the best clinical improvement was achieved using electrode poles that were located several millimeters above the electrode tip. If the relative improvement in motor symptoms was correlated with the required electrical energy for chronic stimulation, the best coefficient was observed for active electrode poles projecting onto white matter dorsal to the STN.

CONCLUSIONS

This observation makes blocking or activation of large fiber connections arising in the STN or running nearby more likely than electrical interference with cell bodies inside the STN. Anatomical correlates may be the pallidothalamic bundle (including Field H of Forel and the thalamic fascicle), the pallidosubthalamic tract, and/or the zona incerta.

Cystic craniopharyngioma: long-term results after intracavitary irradiation with stereotactically applied colloidal beta-emitting radioactive sources

OBJECTIVE

Long-term follow-up data were analyzed to assess the value of intracavitary irradiation with stereotactically applied beta-emitting radioisotopes for the treatment of craniopharyngioma cysts.

METHODS

Sixty-two of 70 consecutive patients with predominantly cystic craniopharyngiomas were selected for retrospective analysis. Beta-Emitting isotopes were injected intracystically using a computed tomography-guided and computer-assisted three-dimensional stereotactic treatment planning and application system (cumulative dose to the inner surface of the cyst wall, 200 Gy).

RESULTS

The tumor response rate gained with yttrium-90-labeled silicate (66 of 78 cysts) or phosphorous-32-labeled chromic phosphate (8 of 78 cysts) was 79.5%. Four cysts treated with rhenium-186-labeled sulfate did not respond. Mean survival after intracavitary irradiation was 9.0 +/- 0.9 years (median follow-up, 11.9 yr). In patients with solitary cysts, the mean survival was 12.5 +/- 1.4 years (actuarial 5- and 10-yr survival rates, 80 and 64%, respectively). Six months postoperatively, visual deficits (38 of 62 patients) had improved in 23 patients and were stable in 15 patients. The side effects that occurred 6 to 12 months after treatment with yttrium-90 were complete blindness (three patients), worsening of visual field cuts (one patient), third nerve palsy (one patient), and diabetes insipidus and/or panhypopituitarism (three patients).

CONCLUSIONS

Intracavitary irradiation using yttrium-90 or phosphorous-32 is highly effective in the treatment of cystic craniopharyngiomas. If applied as initial treatment in patients with solitary cysts, it is the only required therapy over a long period.

Risk analysis of LINAC radiosurgery in patients with arteriovenous malformation (AVM)

The purposes of this analysis were the evaluation of the toxicity of stereotactic single dose irradiation in patients with an arteriovenous malformation (AVM) and the comparison of the authors' own results with already existing risk prediction models. Computed-tomography (CT) or magnetic-resonance (MR) images, and clinical data of patients treated with linear accelerator radiosurgery for an AVM were analysed retrospectively. Using the Cox proportional hazards model (1), the relevance of treatment parameters and dose-volume relationships to the occurrence of radiation-induced tissue changes (oedema and localised blood-brain-barrier breakdown) were assessed. The 81 patients selected for analysis had a mean follow-up of 28.9 months (range: 9.0-65.7 months). Radiation-induced tissue changes (22 out of 81 i.e. 27.2%) were documented on CT or MR images 6.3-33.8 months after radiosurgery (median time: 12.8 months). The actuarial risk at 2 years was 32.1% for the development of neuroradiological changes and 20.1% for the development of symptomatic tissue alteration. The coefficient of total volume receiving a minimum dose of 10 Gy (VTREAT10) reached statistical significance in a Cox proportional hazards model. These results demonstrate the particular vulnerability of normal brain tissue to single dose irradiation. Optimal conformation of the therapeutic isodose line to the 3D configuration of the target volume may help to reduce side effects.

Risk analysis of linear accelerator radiosurgery

PURPOSE

To evaluate the toxicity of stereotactic single-dose irradiation and to compare the own results with already existing risk prediction models.

METHODS AND MATERIALS

Computed tomography (CT) or magnetic-resonance (MR) images, and clinical data of 133 consecutive patients treated with linear accelerator radiosurgery were analyzed retrospectively. Using the Cox proportional hazards model the relevance of treatment parameters and dose-volume relationships on the occurrence of radiation-induced tissue changes (edema, localized blood-brain barrier breakdown) were assessed.

RESULTS

Sixty-two intraparenchymal lesions (arteriovenous malformation (AVM): 56 patients, meningioma: 6 patients) and 73 skull base tumors were selected for analysis. The median follow-up was 28.1 months (range: 9.0-58.9 months). Radiation-induced tissue changes (32 out of 135, 23.7%) were documented on CT or MR images 3.6-58.7 months after radiosurgery (median time: 17.8 months). The actuarial risk at 2 years for the development of neuroradiological changes was 25.8% for all evaluated patients, 38.4% for intraparenchymal lesions, and 14.6% for skull base tumors. The coefficient: total volume recieving a minimum dose of 10 Gy (VTREAT10) reached statistical significance in a Cox proportional hazards model calculated for all patients, intraparenchymal lesions, and AVMs. In skull base tumors, the volume of normal brain tissue covered by the 10 Gy isodose line (VBRAIN10) was the only significant variable.

CONCLUSIONS

These results demonstrate the particular vulnerability of normal brain tissue to single dose irradiation. Optimal conformation of the therapeutic isodose line to the 3D configuration of the target volume may help to reduce side effects.

LINAC-radiosurgery (LINAC-RS) in pituitary adenomas: preliminary results

From 8/90 through 4/94, 32 consecutive patients with recurrent pituitary macroadenoma (PA) were treated with LINAC-RS after tumour resection and/or radiotherapy. Single doses ranging from 8-20 Gy (median: 14.5 Gy) were applied in 14 patients with acromegaly, 5 with Cushing's disease, 4 with Nelson tumours, 5 with prolactinomas and in 4 with nonfunctioning PA's. Retrospective analysis of 26 patients with a follow-up of > or = 6 months revealed no significant endocrinologic response in patients with Cushing's disease, Nelson tumour or prolactinoma. In contrast in 12 evaluated patients with acromegaly within 6-36 months after LINAC-RS the median GH-value decreased significantly. In 3 nonfunctioning PA's a tumour volume reduction has been observed. We conclude, that LINAC-RS with moderate single doses might be a safe and beneficial treatment in patients with acromegaly or nonfunctioning PA's resistant to conventional therapy. In Cushing's disease, Nelson tumours or prolactinomas higher doses seem to be required.

Linac radiosurgery in brain metastases

Brain metastases are usually well-circumscribed and more or less spherical lesions. These conditions meet the criteria for radiosurgery (RS). A pilot study initiated by our group in 1983, demonstrated the effectiveness of Linac-RS in the treatment of solitary brain metastases with low radiosensitivity. A second trial including patients with 1-3 metastases started in 1990. By April 1993, 46 patients had been treated in this series. The radiation doses delivered to the tumour margin ranged from 10 to 25 Gy, and were chosen with respect to size, number and location of the tumours or previous whole brain radiotherapy (WBRT), decreasing mainly with increasing tumour volumes. 34/46 patients had a follow-up of more than 12 weeks. In 7/46 patients the disease progressed rapidly during the first weeks after RS and follow-up examinations were not performed. 5/46 patients had a follow-up of less than 6 weeks and follow-up CT/MR-examinations were not available. 14/46 patients received WBRT before RS. The regularly performed follow-up examinations (clinical status, CT-/MR-examinations in 6 or 12 weekly intervals) revealed tumour progression in 5/34 patients. Permanent cessation of the growth (11/34), tumour shrinkage (18/34) and decrease of surrounding oedema together with clinical amelioration have been observed a few weeks after radiosurgery. The median follow-up was 50 weeks. 14/46 patients died due to generalized progression of their disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Correlation of glucose consumption and tumor cell density in astrocytomas. A stereotactic PET study

To determine histological correlates of the variability of glucose consumption in astrocytomas, the authors performed positron emission tomography (PET) with 18F-2-fluoro-2-deoxy-D-glucose (FDG) and matched the PET scans three-dimensionally with computerized tomography scans obtained in a stereotactic frame before biopsy. Ten patients with astrocytomas of World Health Organization Grade 2 or 3 were studied; patients with glioblastomas, oligodendrogliomas, or oligoastrocytomas were excluded from the study to avoid any confounding effects of different cell types and necroses. In samples of pure tumor, glucose consumption correlated significantly with cell density, but not with nuclear polymorphism. It is concluded that tumor cell density is a major determinant of glucose consumption in astrocytomas. The use of PET with FDG may help to locate the highest cell density and thus improve the diagnostic yield of stereotactic biopsy.

CT-guided and computer assisted stereotactic biopsy. Technique, results, indications

On the base of a stereotactic device originally described by Riechert and Mundinger a three-dimensional localization and treatment planning system for CT-guided computer assisted stereotactic procedures has been developed. The experience with 338 patients, in which image guided stereotaxy has been used for the assessment of various intracerebral lesions, is presented. In 54 of these patients the cannula was introduced with a 20 MHz Doppler-probe positioned at the tip of the needle. A comparison of tissue specimens taken stereotactically with tissue material after tumour resection and/or autopsy was performed in 35 patients. The accuracy of the histological diagnosis was 88%. Bleeding as a complication due to the stereotactic intervention occurred in 8 patients (2.4%). Two of these patients had a fatal outcome (mortality: 0.6%). The morbidity (transient and permanent deterioration of the clinical status) was 1.2%.

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.

Interstitial irradiation of cerebral gliomas with stereotactically implanted iodine-125 seeds

Ninety-seven consecutive patients with primarily inoperable or only partially resectable gliomas have been analysed retrospectively. Mean tumour surface doses of 70 Gy (low grade gliomas) and 56 Gy (high grade gliomas) have been applied with stereotactically implanted Iodine-125 seeds at low dose rates. Patients with a glioma grade III or grade IV and permanent seed implantation additionally received a fractionated external beam irradiation. With mean follow-up times of 55.8 months (glioma grade I), 51 months (glioma grade II) and 59.6 months (glioma grade III) the estimated mean survival probabilities are 105 months, 102 months and 65.7 months respectively. In the glioma grade IV group the estimated mean survival time has been 15.6 months after continuous interstitial irradiation (response rate: 36%). Temporary interstitial irradiation in cases with a glioma grade IV (dose rate: 2.1 Gy/day) caused initial tumour shrinkage in 77%. Neurological deficits following radiation induced vasogenic oedema were reversible in 2 patients and irreversible in another 2 patients. 6 years after the Iodine-125 implantation and continuous interstitial irradiation 1 patient developed a severe localised radiation necrosis.

Computerized optimization of 125I implants in brain tumors

A computer program for treatment planning for the interstitial radiotherapy of brain tumors with 125I stereotactic implants is presented. To minimize brain traumatization only 1-3 catheters loaded with several seeds are implanted. It is possible to position the catheters very accurately due to CT guided stereotactic techniques. Precise treatment planning is necessary because of the high dose gradient of the radiation field. Two planning methods are available: conventional planning with interactive optimization of source configurations and an automatic optimization procedure. The goal of optimization is to identify source parameters (catheter positions and seed activities) for which a prescribed dose at the target surface is approximated as closely as possible.

Diagnostic value of the stereotactic approach to focal lesions in the deep brain of children and adolescents

Since it is relatively harmless, stereotactic biopsy has become in recent years a useful method for the diagnostic assessment of lesions deep in the brain, which are not accessible to open surgery. With the aid of stereotaxis, focal lesions only a few millimeters in diameter can be approached in every location in the brain with high precision. Since stereotaxis does not require general anesthesia, or at most requires only a very shallow anesthesia, it can also be applied to young infants or persons of advanced age. Experience with stereotactic biopsy exploration of lesions of various kinds in the deep brain of 74 children and adolescents, out of a sample of 260 patients of all age groups who received stereotactic biopsy, is reported. Our aim is to demonstrate and discuss the advantage of this contemporary method for child neurology and neurosurgery. In many medical centers in the world where stereotactic tumor biopsy has been established, it has become an important criterion for the choice of treatment.

Stereotactic computer tomography with a modified Riechert-Mundinger device as the basis for integrated stereotactic neuroradiological investigations

For stereotactic biopsy, intracavitary and interstitial irradiation of intracranial tumours, stereotactic CT investigations are of utmost importance. Target-points within a tumour as well as the tumour-outlines have to be transferred precisely from transverse and longitudinal CT sections to stereotactic X-ray images. For this purpose, the stereotactic apparatus of Riechert and Mundinger has been equipped with a fixation system of carbon fibre and a measuring phantoma of plexiglass with embedded steel wires allowing stereotactic CT scanning without artefacts. The stereotactic coordinates (x, y, z) of any target point can be taken directly from transverse CT images with high accuracy. The tumour outlines can be transferred to the stereotactic coordinate system from longitudinal CT reconstructions using special computer programmes. Precise transfer is possible if the CT investigation is performed stereotactically.

Computer tomography (CT) orientated rotary stereotactic system. A technical note

The system consists of an inverted U-shaped frame with right angled corners, so mounted that it can be adjusted vertically, antero-posteriorly and made to rotate on an axis ("the axis of the frame") formed by its free ends. The frame carries an arc probe carrier whose probe holder slides on an arc which is centered on the axis of the frame. The centre of the probe holder and axis of fram lie in one plane "The plane of probe". After positioning the patient in the frame on the CT table, using either table indexing or laser positioning light, the plane of the probe is brought in the CT plane of the target. Once in this CT plane, direct measurements can be obtained so as to bring the axis of the frame passing through the target and centering the arc on the target. The frame can then be rotated to any desired angle and the probe holder can be moved to any position on the arc without altering the direction of the probe with respect to the target. As the structures in the probe plane are constructed of plastic, it can be used within the scanner with practically no artifacts, and direct measurements can be obtained without any calculations. This system can be used in any total body scanner with standard features and no special computer programming is necessary. This is a simple and truly CT-oriented stereotactic system with a high degree of accuracy.