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Biomedical subjects

B Pike

Publications and source records attributed to B Pike.

28 records · Page 2Linked to original sources
PubMed1987

Combined use of digital subtraction angiography and MRI for radiosurgery and stereoencephalography.

The authors report their experience with the combined use of digital subtraction angiography (DSA) and magnetic resonance imaging (MRI) for the stereotactic placement of intracerebral electrodes in epilepsy and for the radiosurgical treatment of otherwise inoperable arteriovenous malformations of the brain. Both imaging techniques, when used in conjunction, have been found most useful and complementary. For deep electrode placement, they permit optimal visualization of the cerebral structures to be reached by the electrode array while allowing the avoidance of vessels in the vicinity. For radiosurgery of arteriovenous malformations, DSA provides optimal visualization of the feeders and of the malformation itself, while the MRI reveals the cerebral structures to be spared by the photon beam of the linear accelerator. A discussion of their respective roles is presented, with the specific question as to whether MRI alone could be used for both procedures.

Cerebral Angiography↗
PubMed1987

Physical aspects of dynamic stereotactic radiosurgery.

Dynamic stereotactic radiosurgery is a radiosurgical technique based on a medium-energy isocentric linear accelerator and a stereotactic frame. The technique uses concurrent and continuous rotations of both the gantry (300 degrees, from 30 to 330 degrees) and the couch (150 degrees, from 75 to -75 degrees). It gives a uniform dose (+/- 5%) within the target volume and dose fall-offs outside the target volume comparable to those obtained from presently known radiosurgical techniques.

Humans↗
PubMed1987

Stereotactic external beam calculations for radiosurgical treatment of brain lesions.

Radiosurgical techniques are becoming increasingly popular for the selective destruction of brain lesions. To ensure precision in the procedure, set-up and treatment of lesions in this manner, we have adopted standard stereotactic methods to allow one to calculate accurately the absorbed dose and also to preserve accuracy in locating the target site in three dimensions. At McGill University, radiosurgery is performed using the dynamic technique, which utilizes the concurrent rotation of both the 10-MV photon beam linear accelerator (from 30 to 330 degrees) and the patient couch (from 75 to -75 degrees) about a common point centered on the target within the lesion. A three-dimensional treatment planning system for the calculation of dose distributions implemented in conjunction with CT, MRI and DSA stereotactic image analysis systems is presented.

Brain Neoplasms↗
PubMed1985

Effect on feed intake of infusing sodium propionate or sodium acetate into a mesenteric vein of cattle.

Solutions containing sodium propionate or sodium acetate were infused into a mesenteric vein of eight steers in order to examine the effect of increasing the entry rate of these metabolites on feed intake. Infusion of propionate inhibited feed intake to varying degrees, but acetate infused at equivalent rates had no effect. Rate of entry of propionate into the visceral circulation may be a physiological mechanism for controlling feed intake in cattle, but it is mainly effective when the animal has eaten close to its voluntary maximum intake.

Acetates↗
PubMed1983

Reliability of faculty assessments of student case histories: a problem in chiropractic education.

A competency based educational model necessitates reliable evaluation. This study examined faculty reliability in assessing students' case histories at one chiropractic college. Previous studies have found great variation in faculty assessment of clinical performance in medical residents. In this study, sixteen faculty members at the Canadian Memorial Chiropractic College evaluated three case histories by completing five rating scales on each one. The study found little faculty agreement in judging the case histories. Faculty evaluations ranged from extremely poor to extremely excellent for the same case history. In addition, the data indicate that the faculty's ratings were influenced by a halo effect. Evaluators made a general judgement, which influenced the ratings on the five scales. It is suggested that meetings of clinical instructors to standardize criteria of assessment may be beneficial.

Chiropractic↗
PubMedDate not supplied

Dose distributions in dynamic stereotactic radiosurgery.

A treatment planning technique for calculation of dose distributions in dynamic stereotactic "radiosurgery" with a 10-MV isocentrically mounted linear accelerator is presented. The treatment planning for dynamic radiosurgery is a three-dimensional problem, since during treatment both the gantry and the couch rotate simultaneously, the gantry from 30 degrees to 330 degrees and the couch from 75 degrees to - 75 degrees. The patient surface and anatomical information is obtained from a family of computed tomography or magnetic resonance scans, and a stereotactic frame is used for target localization, treatment setup, and patient immobilization during the treatment. The dose calculational algorithm follows the gantry and couch rotation in an incremental fashion, and relies on measured stationary beam central axis percentage depth doses and dose profiles to calculate the normalized tissue-maximum-ratio distributions over a matrix of points defined on one of three orthogonal planes (transverse, sagittal, or coronal). The dose calculation algorithm is discussed in detail and calculated dose distributions for single plane and dynamic radiosurgery compared with measured data.

Brain Diseases↗
PubMedDate not supplied

A four-dimensional probabilistic atlas of the human brain.

The authors describe the development of a four-dimensional atlas and reference system that includes both macroscopic and microscopic information on structure and function of the human brain in persons between the ages of 18 and 90 years. Given the presumed large but previously unquantified degree of structural and functional variance among normal persons in the human population, the basis for this atlas and reference system is probabilistic. Through the efforts of the International Consortium for Brain Mapping (ICBM), 7,000 subjects will be included in the initial phase of database and atlas development. For each subject, detailed demographic, clinical, behavioral, and imaging information is being collected. In addition, 5,800 subjects will contribute DNA for the purpose of determining genotype- phenotype-behavioral correlations. The process of developing the strategies, algorithms, data collection methods, validation approaches, database structures, and distribution of results is described in this report. Examples of applications of the approach are described for the normal brain in both adults and children as well as in patients with schizophrenia. This project should provide new insights into the relationship between microscopic and macroscopic structure and function in the human brain and should have important implications in basic neuroscience, clinical diagnostics, and cerebral disorders.

Adolescent↗