Fractionated, stereotactic proton beam treatment of cerebral arteriovenous malformations.

OBJECTIVES: To evaluate the therapeutic efficiency and adverse effects of stereotactic proton beam treatment of cerebral arteriovenous malformations (AVM). MATERIAL AND METHODS: Twenty-six patients treated in Uppsala during 1991-97 were included (men = 14, women = 12; mean age = 39, range = 23-64). The nidus volumes ranged from 0.3 to 102 ml (mean = 24, median = 13). The follow-up included clinical evaluation, magnetic resonance imaging (and/or computed tomography) every 6-12 months for 3 years and final angiography. RESULTS: The volume changes at final follow-up in AVMs >25 ml were -89, -85, -44, -29, -7, 0, 0, +5 and +18 (%); in AVMs 11-24 ml, -100, -100, -97, -92 and 0 (%); and in AVMs <10 ml, -100, -100, -100, -100, -100, -99, -98, -50, -0 and +40 (%). Two patients were lost to follow-up due to cerebral haemorrhage and myocardial infarction. Radiology displayed significant perifocal oedema in one patient and slight oedema in four patients. Of nine patients with epilepsy, seven became seizure-free after therapy while two continued to suffer from seizures. CONCLUSION: Proton beam irradiation is successful in a relatively high proportion of intermediate and large-sized cerebral AVMs. The adverse effects are acceptable. The advantage of proton treatment compared with gamma knife and LINAC stereotactic irradiation is that protons can irradiate even large volumes with a very sharp dose profile against normal surroundings. Thus, proton beam irradiation is a valuable option in the treatment of AVMs larger than 10 ml.

Endovascular treatment of a spinal arteriovenous malformation in a 21-month-old boy.

Reports of spinal arteriovenous malformations in children are rare. This case report describes a 21-month-old boy whose first symptom was attacks of abdominal pain, followed gradually by neurological symptoms. The diagnosis was made using magnetic resonance imaging and spinal angiography, and the patient was successfully treated with embolization.

Location of electric current sources in the human brain estimated by the dipole tracing method of the scalp-skull-brain (SSB) head model.

Using a realistic, 3-shell head model including the scalp (S), skull (S) and brain (B) with conductivity ratios of 1:1/80:1, respectively, the electrical activity in the human brain recorded by conventional electroencephalography was approximated by 1 or 2 equivalent current dipoles. The dipole locations and vector moments were estimated by minimizing the squared difference between the potentials actually recorded from the scalp and those theoretically calculated from the equivalent dipoles. The validity of this dipole tracing method (the DT of the SSB head model) was tested in patients with focal epileptic seizures undergoing presurgical evaluation with intracranial subdural strip electrodes. Weak currents were passed through 1 or 2 pairs of subdural electrodes to create artificial dipoles. The dipole estimations correctly distinguished between single and double generator sources, but there were certain dislocations of the calculated dipoles. The average error of dislocation was found to be 8.5 mm for the 1-dipole model. That for the 2-dipole model was 6 mm for one of the components and 18 mm for the other. It was concluded that the DT method of the SSB head model can be a valuable clinical tool in 3-dimensional localization of focal epileptic discharges in the human brain.

Patient positioning for fractionated precision radiation treatment of targets in the head using fiducial markers.

When irradiating targets in the brain, an accurately localised dose is often needed. One crucial moment to achieve this is the positioning of the patient. We have developed a positioning method where the patient is immobilised with a bite block and a head mould, and where the position of the target is determined by X-ray imaging of fiducial markers that are placed in the patient's skull. A method for computing the transformation needed to move the target from the observed to the prescribed position and orientation is described. This method uses the information from two orthogonal X-ray images and takes measurement errors and data from three or more markers into account. Results from using the method clinically in proton beam therapy are given.

The rhesus monkey as a model for studies of pregnancy induced changes in metoprolol metabolism.

Five pregnant Rhesus monkeys were catheterized in the hepatic and femoral veins. They were simultaneously given 168 or 176 micrograms of 3H-metoprolol intravenously, and 9 mg of metoprolol per kg body weight orally. The same procedure was repeated a few months after delivery. Analyses of the unlabelled drug in blood were made by gas-chromatography and of the 3H-labelled metoprolol, by liquid scintillation. The apparent volume of distribution as well as the terminal half-lives of metoprolol were in the same range during pregnancy and in non-pregnancy. The oral bioavailability of metoprolol was lower (6-22%) during pregnancy than in non-pregnancy (9-49%). The apparent oral clearance and the intrinsic hepatic clearance were in a similar range although there was a greater variation in the intrinsic clearance values. The former clearance estimate was lower in the non-pregnant state only for three of the five animals. The systemic clearance varied very little and was in the same range during pregnancy and in non-pregnancy. The changes in apparent oral clearance and in oral bioavailability of metoprolol between the pregnant and non-pregnant Rhesus monkey are similar to the changes observed in pregnant women, although the absolute values are different.

Reliability of attenuation measurements in CT of the lumbar spine: evaluation with an anthropomorphic phantom.

A phantom was constructed with the intention of simulating the clinical situation at examination of the spine. Artifacts from bony vertebral structures were analyzed and the uniformity in a body-shaped object was studied. Tests were carried out on eight CT scanners. A considerable variation in uniformity was found between the tested scanner models. The CT numbers within the spinal canal and in a region anterior to the spine were elevated for most of the scanners. The deviation varied considerably, however, between models.

Spatial distribution of dose in computed tomography with special reference to thin-slice techniques.

The spatial dose distribution in a cylindrical polystyrene phantom with a diameter of 200 mm was measured for seven computed tomography (CT) scanners. The measurements were performed in the head mode and mainly for narrow slices in the range 1.5 to 4 mm. Both radial and axial dose profiles were measured and the dose distribution for multiple-scan procedures was calculated. The ratio between the surface and centre doses for a single scan varied between the extremes of 1.8 and 4.3 and was generally higher for narrow than for wide slices. With multiple nominally contiguous scans the difference in absorbed dose between surface and centre locations in the object decreased, on account of scattered radiation. The CT dose index for centre locations varied considerably between the tested scanners, with a range from 5.6 to 27.2 mGy per nominal 100 mAs. For a simulated multiple-scan procedure, comparable to a CT examination of the orbits, the multiple-scan average dose varied between 4.3 and 16.4 mGy per nominal 100 mAs.

Positron emission tomography: an animal model of spinal distribution of drugs after intrathecal administration.

An animal model has been developed in the Rhesus monkey for noninvasive monitoring of CSF transport of drugs by external detectors i.e. positron emission tomography. The model compromises the cannulation of the subarachnoid space (with a spinal needle), and has been used without any damage to the monkey. With the method it was shown that injection rate had a major influence on the transport rate of 68GaCl3 in the CSF. Injection of 0.5 ml over 60 sec gave the highest radioactivity near the injection site, whereas an injection rate of this volume over 10 sec resulted in high radioactivity more rostrally shortly after injection. This method have been of value for the determination of drug kinetics after spinal administration.

Deep-frozen biologic phantom for performance evaluation of CT scanners.

A test method with use of a biologic phantom--a deep-frozen specimen of a human cadaver--was developed in an attempt to simulate the clinical setting in CT of the spine. The quality of both soft tissue and bone images in the absence of motion artifacts was evaluated for seven scanner models. Special attention was paid to identification of the pattern and extent of artifacts. The phantom consisted of a spine with surrounding muscles. The images were evaluated subjectively and comparisons were made between the different scanners. Examples of these results are presented. A biologic phantom is a valuable supplement to artificial phantoms and increases the ability to evaluate and compare the performance of CT scanners.

Eye lens dose in cranial computed tomography with reference to the technical development of CT scanners.

The continuous technical development of cranial CT and the accumulation of clinical experience with this method, have resulted in the use of an increasing number of scan protocols for different clinical situations. An investigation was undertaken to find out how this change has influenced the dose delivered to the patient. The eye lens dose was measured at CT examinations in 245 patients, with appropriate scan protocols, and also at corresponding examinations in an anthropomorphic head phantom. One CT scanner of early (EMI CT 1010) and one of modern design (Siemens Somatom DR2) were investigated. The range of the eye lens dose was wide, namely 4 to 206 mGy for EMI CT 1010 and 6 to 124 mGy for Somatom DR2. In patient groups with comparable scan protocols the mean eye lens dose was higher with the Somatom DR2, mostly on account of a different spatial distribution of the dose in the scan plane. The dose varied less with this scanner, however, mainly because of the possibilities for more accurate positioning.

Artifacts in computed tomography of the posterior fossa: a comparative phantom study.

A phantom consisting of a human skull fixed in a cylinder containing water was used to study the occurrence of artifacts and their influence on image quality in CT of the posterior fossa. Only minor differences in interpetrous bone artifact and in deviation in CT numbers in other parts of the posterior fossa were found between eight tested scanner models. Interpetrous bone artifact was not significantly affected by slice thickness but it could be reduced to some extent by proper selection of the scan angle and almost eliminated by application of a dual-energy technique. Other bone-related artifacts, however, were found to be dependent on slice thickness.

Liposarcoma of the orbit: a clinicopathological case report.

Liposarcoma is a very rare primary tumour of the orbit. The present report describes changes seen by computed tomography, carotid angiography, and histopathology and gives a review of the literature.

Rapid regression of pituitary tumours during bromocriptine treatment of women with hyperprolactinaemia.

Four hyperprolactinaemic women with large pituitary adenomas with suprasellar extension were given primary tumour therapy with bromocriptine. The treatment resulted in rapid tumour regression in all the women, as verified by repeated computerized tomography (CT) scans. Pronounced visual field defects were present in three of the four women before treatment. All of them had marked improvement of vision within a few days after the initiation of bromocriptine therapy and they regained normal or nearly normal visual fields during the treatment. The raised serum prolactin concentrations decreased to normal levels in all the women. Thus, medical treatment with bromocriptine can induce rapid tumour regression in patients with hyperprolactinaemia and large pituitary tumours.

Cerebral computed tomography in methanol intoxication.

In four of six patients with methanol intoxication, computed tomography (CT) showed necrotic changes in the area of the putamina. Hemorrhages were also seen in some cases. There was a clear relationship between the severity of the clinical symptoms and the CT findings, indicating the potential of CT for prognosis and possible therapy guidance.

Technique of cervical myelography with metrizamide.

A technically simple modification of the prone posture technique for cervical myelography with use of metrizamide (Amipaque) after lumbar puncture is described. The procedure is well tolerated by the patients.