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Biomedical subjects

R D Bucholz

Publications and source records attributed to R D Bucholz.

At least 19 recordsLinked to original sources
PubMed2001

Three-dimensional localization: from image-guided surgery to information-guided therapy.

Image-guided surgery has become the standard of care for intracranial procedures. However, significant development is required before the benefits of this technology are brought to the majority of patients undergoing surgery. This article categorizes the areas wherein progress is needed, and indicates recent advances that may form the basis for the broad acceptance of this exciting technology. Emphasis is placed on a technique whereby preoperative imaging can be updated using low-resolution intraoperative imaging to reflect changes in anatomy caused by surgery, and on transforming image-guided surgery to information-guided therapy, in which diverse sources can be brought to bear at the time of greatest possible benefit, when the patient's anatomy is exposed for therapeutic intervention.

Brain↗
PubMed2001

Comparison of Scientific Calipers and Computer-Enabled CT Review for the Measurement of Skull Base and Craniomaxillofacial Dimensions.

Traditionally, cadaveric studies and plain-film cephalometrics provided information about craniomaxillofacial proportions and measurements; however, advances in computer technology now permit software-based review of computed tomography (CT)-based models. Distances between standardized anatomic points were measured on five dried human skulls with standard scientific calipers (Geneva Gauge, Albany, NY) and through computer workstation (StealthStation 2.6.4, Medtronic Surgical Navigation Technology, Louisville, CO) review of corresponding CT scans. Differences in measurements between the caliper and CT model were not statistically significant for each parameter. Measurements obtained by computer workstation CT review of the cranial skull base are an accurate representation of actual bony anatomy. Such information has important implications for surgical planning and clinical research.

Journal Article↗
PubMed2000

Shape analysis of hippocampal surface structure in patients with unilateral mesial temporal sclerosis.

Structural hippocampal magnetic resonance (MR) imaging-based analysis is helpful in the diagnosis and treatment of mesial temporal epileptic seizures. Computational anatomic techniques provide a framework for objective assessment of three-dimensional hippocampal structure. We applied a previously validated technique of deformation-based hippocampal segmentations in 20 subjects with documented unilateral mesial temporal sclerosis (MTS) and temporal lobe epilepsy. Using composite images, we then measured shape differences between the epileptogenic, smaller hippocampus, and contralateral hippocampus. Final shape differences were projected on the contralateral "normal" side. We calculated results for the left MTS group (10 patients) and right MTS group (10 patients) separately. Both groups showed similar regions of maximal inward deformation in the affected hippocampus, which were the medial and lateral aspect of the head, and posterior aspect of the tail. These results suggest that there are specific three-dimensional patterns of volume loss in patients with mesial temporal epilepsy.

Dominance, Cerebral↗
PubMed2000

Mesial temporal sclerosis and temporal lobe epilepsy: MR imaging deformation-based segmentation of the hippocampus in five patients.

In five patients with mesial temporal sclerosis, the authors verified the precision and reproducibility of hippocampal segmentations with deformation-based magnetic resonance (MR) imaging. The overall percentage overlap between automated segmentations was 92.8% (SD, 3.5%), between manual segmentations was 73.1% (SD, 9.5%), and between automated and manual segmentations was 74.8% (SD, 10.3%). Deformation-based hippocampal segmentations provided a precise method of hippocampal volume measurement in this patient population.

Adult↗
PubMed1996

Therapeutic Intervention Scoring System used in the care of patients in pentobarbital-induced coma to determine nurse-patient ratios.

BACKGROUND: Critical care patients generally require extensive interventions, thereby consuming a large percentage of healthcare resources. Induced pentobarbital coma for the management of increased intracranial pressure is one such intervention, required to maintain patient stability. Quantification of these interventions, as well as the amount of nursing work required, has not been addressed in the literature. OBJECTIVE: To use the Therapeutic Intervention Scoring System to analyze and quantify how interventions affect nurse-patient ratios in the management of patients in pentobarbital coma for refractory increased intracranial pressure. METHODS: The medical records of patients with subarachnoid hemorrhage from aneurysmal rupture and subsequent increased intracranial pressure, in whom pentobarbital coma was salvage therapy, were reviewed retrospectively. The Therapeutic Intervention Scoring System was used to quantify the number of interventions required before, during, and after coma induction. The data were analyzed and daily Therapeutic Intervention Scoring System scores correlated with serum pentobarbital levels. Typically, a critical care nurse can manage a patient caseload of 40 to 50 Therapeutic Intervention Scoring System points. By quantifying the interventions, the score reflected the amount of care required to manage the patient in barbiturate coma. RESULTS: The intensity of interventions correlated with the level of coma, length of time in coma, and associated complications. CONCLUSIONS: The scores indicated the intensity of interventions used in pentobarbital coma and the use of resources. Nursing care and complications involved with this therapy were quantified and nurse-patient ratios were established.

Adult↗
PubMed1996

Image-guided surgical techniques for infections and trauma of the central nervous system.

The value of image-guided stereotactic systems is directly dependent on the ease and speed of their use. In the past, most stereotactic techniques were complicated and timely to set up; thus, they were used exclusively for either resecting neoplasms or for neurologic function. However, current systems equipped with advanced registration techniques are much simpler and faster to employ, and indications for their use are rapidly increasing. We describe an advanced image-guided navigation system and provide examples of its successful use in neurosurgical treatment of central nervous system infection and trauma.

Abscess↗
PubMed1995

Presurgical localization of functional cortex using magnetic source imaging.

The boundaries of somatosensory cortex were localized noninvasively by means of a large-array biomagnetometer in six patients with mass lesions in or near eloquent cortex. The results were used by neurosurgeons and neurologists in preoperative planning and for reference in the operating room. The magnetic source imaging (MSI) localizations from somatosensory evoked potentials were used to predict the pattern of phase reversals measurable intraoperatively on the cortical surface, providing a quantitative comparison between the two measures. The magnetic localizations were found to be predictive in all six cases, with the two sets of localizations falling within an 8-mm distance on average. Somatosensory localizations using MSI offer accuracy in localizing somatosensory cortex stereotactically and in depicting its relationship to lesions. Such data are valuable preoperatively in assessing the risks associated with a proposed surgical procedure and for optimizing subsequent minimum-risk surgical strategy.

Adult↗
PubMed1995

Clinical applications of frameless stereotactic devices in neurotology: preliminary report.

Conventional stereotactic surgery has been utilized primarily for intracranial neuro-surgical procedures. Despite their utility, head-frame systems are restrictive and often inconvenient, thus they have not proved applicable for neurotologic surgery. Recently frameless stereotactic navigational systems have been developed that employ three-dimensional digitizers to transform the coordinates in surgical space to the corresponding image space, without the employment of head frames. This allows the determination of position of a surgical instrument in real time during surgery, and its display on video-projected computed tomography or magnetic resonance imaging scanned images. This preliminary report focuses upon an optoelectric referenced frameless stereo-tactic system, the NeuroStation, as it relates to minimally invasive neurotologic surgery. Clinical applications, limitations, and future directions are discussed, and three representative surgical cases are presented. This device has potential as an adjunctive navigational tool for certain neurotologic procedures.

Adult↗
PubMed1993

Magnetic source imaging: a review of the Magnes system of biomagnetic technologies incorporated.

Magnetic source imaging (MSI) is a new, noninvasive technique for defining the relationship between brain function and structure on a patient-to-patient basis. It achieves this by combining detailed neurophysiological data derived from magnetoencephalography with high-quality neuroanatomical data derived via magnetic resonance imaging. By the use of mathematical models, the spatial locations of those neurons that generate neuromagnetic signals of interest are estimated and subsequently marked on spatially aligned magnetic resonance images. There are three prominent types of clinical MSI examinations. These are: 1) functional mapping examinations in which sensory and motor functions are localized; 2) examinations of interictal epileptiform activity; and 3) examinations of abnormal low-frequency magnetic activity, which has been found to be present in a wide range of pathophysiological conditions. Functional mapping provides useful information regarding the relationship between the cortical representation of eloquent function and the location of pathological lesions that may be surgically resectable. This application is of particular utility in cases of intracortical masses that distort and obscure the local neuroanatomy. By defining the primary sites of interictal epileptiform activity, MSI examinations are useful in the surgical planning for the implantation of depth electrodes and the planning of partial lobectomies. Abnormal low-frequency magnetic activity appears to be a neurophysiological correlate of ischemic penumbra associated with stroke, neoplasms, and vascular malformations. Abnormal low-frequency magnetic activity has also been found to be present in several other conditions, including head trauma and psychiatric dysfunction, although the exact pathophysiological mechanisms are presently unclear.(ABSTRACT TRUNCATED AT 250 WORDS)

Brain Mapping↗
PubMed1993

Variables affecting the accuracy of stereotactic localization using computerized tomography.

Stereotactic localization using computerized tomography (CT) is increasingly employed to guide neurosurgical procedures in crucial areas of the brain such as the brain stem. This technique allows the surgeon to resect a lesion in its entirety while sparing critical areas of the brain. Thus, the parameters used for scanning should be selected for maximum accuracy. While the small pixel size of CT scanners suggests a high degree of precision in localization, there have been few systematic studies of this accuracy. The authors have studied the amount of error in localization created by variables such as CT scan thickness, interscan spacing, size of lesion, and method of computation when using the Brown-Roberts-Wells (BRW) stereotactic system. Over 1000 CT scans were made of a phantom composed of spheres of differing diameter and location. The CT slice thickness was varied from 1.5 to 5.0 mm, and interscan spacing was varied from 0.5 to 3.0 mm. The coordinates of the center of the spheres were calculated independently using the laptop computer supplied with the unit and also by a stereotactic computer which automatically calculates the center of the fiducials. The actual BRW coordinates of the sphere center were obtained using the phantom base and were then compared to the computer-calculated coordinates to determine error in localization. Variables with a significant effect on error included the scan thickness, interscan spacing, and sphere size. The mean error decreased 23% as the scan thickness decreased from 5.0 to 1.5 mm and 45% as the interscan spacing decreased from 3.0 to 0.5 mm. Mean error was greatest for the smallest sphere sizes. The two computational methods did not differ in error. This study suggests that, for critical areas of the brain or for small lesions, a scan thickness of 1.5 mm and interscan spacing of 0.5 mm should be employed.

Brain↗
PubMed1992

Neurologic recovery associated with anterior decompression of spine fractures at the thoracolumbar junction (T12-L1).

Between 1981 and 1990, twenty-two patients with incomplete neurologic deficits after thoracolumbar junction fractures were treated by anterior decompression and stabilization. Two patients were unavailable for follow-up examination, eleven underwent spinal canal decompression within 48 hours of injury (Group A); and nine patients underwent surgical decompression in an average of 61 days after injury (Group B). Neurologic recovery was analyzed by a modified Frankel grading system, the ASIA motor point scale and conus medullaris function. Patients were followed for an average of 3.5 years (range, 6-92 months). No patients had any deterioration in neurologic function after surgery. Patients in Group A had a modified Frankel grade improvement with a median of two grades and a mean American Spine Injury Association motor point improvement of 21.1 +/- 4.1. Four of nine patients with conus medullaris deficits demonstrated complete functional bladder and bowel return postoperatively. Those patients in Group B had a modified Frankel grade improvement with a median of one grade and a mean ASIA motor point improvement of 7.6 +/- 1.7. None of the six patients with conus medullaris injuries showed complete improvement in bladder or bowel function postoperatively. The modified Frankel grade and ASIA motor point score improvements were significant when the two groups were compared (P less than 0.04 and P less than 0.01, respectively). In this series of patients, early anterior decompression for traumatic injuries at the thoracolumbar junction was associated with improved rates of neurologic recovery when compared to late decompression.

Adolescent↗
PubMed1991

Cerebrospinal fluid endothelin-1 and endothelin-3 levels in normal and neurosurgical patients: a clinical study and literature review.

Endothelins are a family of structurally related, potent, long-lasting vasoconstrictor peptides. There are no established normal human levels of endothelin-1 or endothelin-3 in the cerebrospinal fluid. We measured cerebrospinal fluid endothelin-1 and endothelin-3 levels in five groups of patients: normal controls, patients with subarachnoid hemorrhage and cerebral vasospasm, patients with severe head injuries, patients undergoing temporal lobectomy for intractable epilepsy, and a patient with a gunshot injury to the thoracic spine. Endothelin-3 levels were significantly elevated in patients with subarachnoid hemorrhage and may participate in cerebral vasospasm and subsequent neurologic deterioration.

Adult↗