[Reconstruction of capside structures in isometrical viruses with an equidensites rotation method (author's transl)].
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Densitometry↗
Biomedical subjects
K R Peters
Publications and source records attributed to K R Peters.
A Canadian cohort study of cognitive impairment and related dementias (ACCORD): study methods and baseline results.
The overall objective of the Canadian Collaborative Cohort of Related Dementias (ACCORD) study is to describe the diagnostic distribution, natural history and treatment outcomes of individuals referred from the community to dementia clinics in Canada. Between 1997 and 1999, an inception cohort of 1,136 subjects entered into this longitudinal study. At the baseline assessment, 10.9% of the subjects were classified as "not cognitively impaired" (NCI), 30.1% as "cognitively impaired not demented" (CIND), and 59% as demented. A subclassification of CIND included amnestic 25.1%, vascular cognitive impairment 18.1%, psychiatric 17.2%, neurologic 7.3%, medical/toxic metabolic 3.5%, mixed 7.6% and not specified 19.0%. The percentage of the cohort referred with dementia increased progressively each decade, while the proportions of CIND and NCI decreased. Within the dementia group, Alzheimer's disease accounted for 47.2% of the subjects, mixed dementias 33.7%, vascular dementia 8.7%, frontotemporal degenerations 5.4%, dementia with Lewy bodies 2.5%, and unclassifiable 1.8%. The ACCORD cohort will allow a detailed study of the longitudinal course of CIND, and the longer-term outcomes of both treated and untreated dementia subjects.
Adult↗
Effective dose equivalents to patients undergoing cerebral angiography.
PURPOSE: To determine values of the effective dose equivalent, HE, for patients undergoing diagnostic cerebral angiography and compare these values with radiation doses received by patients undergoing other diagnostic examinations of the head. METHODS: The radiographic techniques for ten patients undergoing cerebral angiography were recorded and used to obtain the product of the entrance skin dose and the x-ray beam cross-sectional area. These measured dose-area product data were converted into effective dose equivalents employing published conversion factors which take into account the part of the patient anatomy irradiated and the radiographic technique factors employed. RESULTS: The average patient HE value was 10.6 mSv, with a range of 2.7-23.4 mSv. Fluoroscopy contributed approximately 67% of the total HE, with cut films and digital subtraction angiography contributing 26% and 7%, respectively. CONCLUSIONS: The radiation doses (HE) to patients undergoing diagnostic cerebral angiography are comparable to the patient doses in nuclear medicine brain studies where the typical HE is approximately 10 mSv. In CT, the patient dose is approximately 2 mSv, whereas in plain skull x-ray examinations, the patient dose is much lower at approximately 0.15 mSv.
Angiography, Digital Subtraction↗
Intraarterial use of sodium methohexital for provocative testing during brain embolotherapy.
PURPOSE AND METHODS: To assess its vascular effects and safety, we used sodium methohexital (Brevital)--an ultrashort-acting barbiturate--as the provocative intraarterial agent in a series of 30 patients with arteriovenous malformations at a 1% concentration and at doses of less than 5 mg per injection. Digital vascular imaging was performed just prior to and just after the injections. RESULTS: No angiographic or clinical evidence of apparent vasospasm occurred in the trial population (66 vascular pedicle injections in 30 patients). When functional tissue was perfused with 1-6 mg of the 1% Brevital solution, evidence of altered neurologic status became immediately apparent, but cleared within 2 minutes in all cases. None of the patients experienced either prolongation of the induced clinical symptoms or seizures to suggest any adverse effects related to either crystallization of the Brevital or the effects of injecting an alkaline solution in the cerebral circulation. CONCLUSION: Though the full effects of methohexital in the cerebral circulation remain to be elucidated, existing reports suggest it is a safe provocative agent for use prior to embolotherapy for brain arteriovenous malformations.
Cerebral Angiography↗