Reformatted imaging to define the intercommissural line for CT-guided stereotaxic functional neurosurgery.

Functional stereotaxic neurosurgery has traditionally required definition of the line between the anterior and posterior commissures as the basis for defining the target site for a procedure such as stereotaxic thalamotomy. While axial computed tomographic (CT) imaging precisely defines the third ventricle and the commissures, the planes of the axial images are not necessarily parallel to the important intercommissural line. A technique is described in which coronal oblique reformations are obtained, with the reformations passing through both the anterior and posterior commissures. Stereotaxic coordinates of the target obtained from this reformatted image are directly transferable to the CT-compatible Leksell frame. Both imaging and surgery are performed on the scanner, which is located in an operating room especially designed for CT-guided surgical procedures.

The development of a xenon/computed tomography cerebral blood flow quality assurance phantom.

A simple, easy to use, quality assurance and performance test phantom was developed for the xenon/computed tomography (CT) cerebral blood flow method. The phantom combines an inhalation system which allows for the simulation of xenon buildup or washout in the arterial blood as well as a multisection translatable cylinder in which several sections can be scanned during a preselected protocol to simulate the CT enhancement in brain tissue during a study. The phantom and scanning protocol are described and their use is demonstrated. The results compare favorably to the theoretically expected fast, intermediate, and slow "flow" values designed into the phantom.

Errors associated with single-scan determinations of regional cerebral blood flow by xenon enhanced CT.

Possible errors in the determination of xenon concentrations in arterial blood, and uncertainties in CT tissue enhancements during inhalation of xenon-oxygen mixtures, are used to assess errors in the determination of regional cerebral blood flow by the in vivo autoradiographic (single-scan) technique. The results of this study indicate that errors associated with the determination of xenon concentrations in arterial blood decrease rapidly as the time of scanning after the initiation of xenon inhalation is increased. Analysis of errors caused by statistical uncertainties in image enhancement indicate that time of scanning is optimal between 1.5 and 2.5 min for determination of fast flow, while errors in slow-flow determinations gradually decrease as the time of scanning increases.

Xenon and iodine enhanced cerebral CT: A closer look.

Xenon and iodine enhanced dynamic computerized tomography (CT) have been used experimentally to obtain both qualitative and quantitative information on local cerebral blood flow in both normal and infarcted tissue. Direct comparisons between Xenon enhancement, iodine enhancement and pathological findings demonstrate significant differences between results derived from each of the 2 in vivo techniques. While iodine enhanced dynamic CT yields valuable information concerning the patency and density of vasculature, xenon enhanced studies can provide highly focal information on cerebral tissue perfusion.

Xenon enhanced dynamic computed tomography: multilevel cerebral blood flow studies.

Xenon enhanced computed tomography with a fast scanning mode and interscan table incrementation was used to derive local cerebral blood flow in a nonhuman primate 19 days following infarction. The in vivo autoradiographic methodology was used to derive blood flow in normal and diseased tissue at four different brain levels (slices) during a single inhalation study.

Regional pulmonary ventilation measurements by xenon enhanced dynamic computed tomography: an update.

New developments in computed tomographic technology permit rapid, serial images that may yield information concerning tracer kinetics through a large tissue volume. One possible application of these developments is the derivation of local lung ventilation by observing the temporal changes of stable xenon concentrations. Preliminary results from six multilevel ventilation studies in dogs demonstrate that the lung may be repeatedly imaged during reproducible phases of respiration even when interscan table incrementation is employed to survey a number of tissue segments and breathing is permitted between scans. In addition, subanesthetic xenon concentrations provide adequate enhancement for possible quantification.

Three-dimensional computed tomography of acetabular fractures.

Computer programs that produce 3D surface reformations from sets of contiguous axial CT scans were used in evaluating a variety of acetabular fractures in 20 patients. The 3D images were easily correlated with plain radiographs, and new views were produced that provided a unique perspective not obtainable by conventional radiography. The 3D images were useful in complex displaced fractures in cases in which the interpretation of plain radiographs was difficult. Plain radiographs and conventional CT scans were more sensitive than the 3D images in detecting undisplaced fractures.

Digital radiography of the chest by self-scanning linear diode arrays.

Diode array digital radiography DADR is a method of radiographic imaging that combines the advantages of computer technology with self-scanning linear diode arrays. These digital images are superior to those obtained by film in recording and displaying information in the lightest and the darkest areas of the film, resulting in a balanced image of the entire thorax without compromising detail, and at reduced radiation dose. This is a direct result of the wide dynamic range, high contrast sensitivity, fiber optic coupling, small diode size, short exposure time, and rejection of scattered x-rays of the system coupled with digital post-processing enhancement of the image displayed at 1024 X 1024 pixels.

Diode array digital radiography: initial clinical experience.

Initial clinical results are described for a new method of digital radiography based on high-detail self-scanning linear diode arrays which overcome many of the limitations of present film or other digital methods. The technique uses a fan-shaped x-ray beam to produce a nearly scatter-free image on a phosphor strip that is fiber-optically coupled to six self-scanning arrays of light-sensitive diodes spaced 0.025 mm, thus providing 6,144 discrete sensors across the field of view. Because these diodes have a greatly expanded dynamic range and operate at very low noise, it becomes possible to visualize small density differences or contrast below 1% both in the light and dark areas of the image. Because of the efficiency of detection and display, radiation doses can be reduced for a given information content. Our preliminary clinical studies have shown to broad application of our method in examining the chest and abdomen and in performing intravenous digital arteriography.