Phase contrast cine magnetic resonance imaging: normal cerebrospinal fluid oscillation and applications to hydrocephalus.

Two-dimensional cine phase contrast (2D-cine PC) magnetic resonance (MR) imaging is an imaging technique that sensitizes MR images to velocity changes in a specific direction while cancelling signals from stationary protons and from motion in other directions. This article reviews the technique, conventions, and applications of this imaging technique to hydrocephalus. 2D-Cine PC and additional more rapid MR imaging methods now in development will allow clinicians to measure CSF velocity, pulsation, and bulk flow noninvasively in normal individuals and in patients with a variety of pathologic conditions. It is hoped that these measurements may be correlated with intracranial pressures to develop clinical tests of brain compliance and improved management of patients with hydrocephalus.

Radiosurgery target point alignment errors detected with portal film verification.

Stereotactic radiosurgery with a linear accelerator requires an accurate match of the therapeutic radiation distribution to the localized target volume. Techniques for localization of the target volume using CT scans and/or angiograms have been described. Alignment of the therapeutic radiation distribution to the intended point in stereotactic space is usually accomplished using precision mechanical scales which attach to the head ring. The present work describes a technique used to verify that the stereotactic coordinates of the center of the intended radiation distribution are in agreement with the localized target point coordinates. This technique uses anterior/posterior and lateral accelerator portal verification films to localize the stereotactic coordinates of the center of the radiation distribution with the patient in the treatment position. The results of 26 cases have been analyzed. Alignment errors of the therapeutic radiation distribution in excess of 1 mm have been found using the portal film verification procedure.

Stereotactic radiosurgery: dose-volume analysis of linear accelerator techniques.

Stereotactic radiosurgery of the brain may be accomplished with a linear accelerator by performing several noncoplanar arcs of a highly collimated beam focused at a point. The shape of the radiation distribution produced by this technique is affected by the beam energy, field size, and the number and size of the arcs. The influence of these parameters on the resulting radiation distributions was analyzed by computing dose volume histograms for a typical brain. Dose volume functions were computed for: (a) the energy range of 4-24 MV x rays; (b) target sizes of 1-4 cm; and (c) 1-11 arcs and dynamic rotation. The dose volume histograms were found to be dependent on the number of arcs for target sizes of 1-4 cm. However, these differences were minimal for techniques with 4 arcs or more. The influence of beam energy on the dose volume histogram was also found to be minimal.

Improved linac dose distributions for radiosurgery with elliptically shaped fields.

Stereotactic radiosurgery techniques for a linear accelerator typically use circular radiation fields to produce an essentially spherical radiation distribution with a steep dose gradient. Target volumes are frequently irregular in shape, and circular distributions may irradiate normal tissues to high dose as well as the target volume. Improvements to the dose distribution have been made using multiple target points and optimizing the dose per arc to the target. A retrospective review of 20 radiosurgery patients has suggested that the use of elliptically shaped fields may further improve the match of the radiation distribution to the intended target volume. This hypothesis has been verified with film measurements of the radiation distribution obtained using elliptical radiation beam in a head phantom. Reductions of 40% of the high dose volume have been obtained with elliptical fields compared to circular fields without compromising the dose to the target volume.

Stereotactic target point verification of an X ray and CT localizer.

Stereotactic radiosurgery with a linear accelerator requires the accurate determination of a target volume and an accurate match of the therapeutic radiation dose distribution to the target volume. X ray and CT localizers have been described that are used to define the target volume or target point from angiographic or CT data. To verify the accuracy of these localizers, measurements were made with a target point simulator and an anthropomorphic head phantom. The accuracy of determining a known, high contrast, target point with these localizers was found to be a maximum of +/- 0.5 mm and +/- 1.0 mm for the X ray and CT localizer, respectively. A technique using portal X rays taken with a linear accelerator to verify the target point is also described.

Brain biopsies in patients with acquired immune deficiency syndrome.

Seven brain biopsies from patients with the acquired immune deficiency syndrome (AIDS) were reviewed. Toxoplasmic encephalitis was diagnosed in five patients, neurotuberculosis in one patient, and no diagnosis was made in the seventh patient. Frozen sections and smears enabled a rapid diagnosis to be made in four patients. Routine histochemical analysis was diagnostic in five patients, and the immunoperoxidase technique for Toxoplasma gondii was required for diagnosis in an additional case. Brain biopsy is a valuable and safe method in the evaluation of mass lesions in patients with AIDS.

Analysis of the effect of kinetic therapy on intracranial pressure in comatose neurosurgical patients.

The use of oscillating beds in the management of immobilized patients has been reported to minimize some of the complications associated with immobility. In this study, 10 patients admitted with a clinical presentation of raised intracranial pressure (ICP) underwent monitoring of their ICP while receiving kinetic therapy as provided by the Roto-Rest treatment table. An analysis of the possible effect that the constant change in position might have on the ICP was carried out. ICP readings were obtained with the patient in each of three bed positions (extreme left, extreme right, and supine) every half hour. Results from correlational analyses indicated that changes in bed position did not differentially affect ICP. The results of this study suggest that the presence of raised ICP should not limit the use of kinetic therapy in an attempt to minimize the complications of immobility in comatose neurosurgical patients.

Diagnosis of intracranial space-occupying lesions with DTPA-Sn-99mTc.

DTPA-Sn-99 mTc is an excellent radionuclide for brain scintigraphy procedures with a rapid blood clearance through glomerular filatration. No previous preparation of the patient is necessary. We have studied forty nine patients with primary or metastatic brain tumours as well as calvarium metastases. There have been five false negatives. We have found three types of scintigraphic patterns depending on whether the lesion is better visualized in early or late images, or does not change throughout the study. The sequential brain study, obtaining views at five minutes, and at one and two hours post-injection allows for an adequate morphological characterization of the lesion and occasionally, a histological diagnosis.