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Biomedical subjects

R Guiraud

Publications and source records attributed to R Guiraud.

At least 19 recordsLinked to original sources
PubMed1990

[A simulation method for studying scintillation camera collimators].

This paper presents a computer simulation of photon interaction with collimator septa, which allows the point spread function of scintillation camera collimators to be calculated. The method simulates photon attenuation along their propagation direction in a determinist way. Using this simulation, the spatial resolution, geometric efficiency and penetration index of collimators may be easily assessed. Results obtained with this method are presented and compared with those obtained from standard formulae. We show the usefulness of the simulation which precisely accounts for effects of septum penetration. Measurements performed on two collimators with 131I and 99Tcm point sources provide results consistent with those obtained from the simulation method. In conclusion we show that this method is an accurate tool to assist conception of collimators for nuclear medicine.

Computer Simulation↗
PubMed1989

Human brain and spinal cord scan after intracerebroventricular administration of iodine-123 morphine.

[123I]iodomorphine (IMPH) was administered intracerebroventriculary (i.c.v.) in eight patients treated by i.c.v. morphinotherapy (i.c.v.m.). Scans obtained by gamma-scintigraphy over 1 h post-injection showed only a slight diffusion of IMPH beyond the ventricular system, particular attention being paid to the spinal cord. These data agree well with induced i.c.v.m. analgesia (mean latency 20 min) and biological results such as HPLC assay of morphine in the lumbar cerebrospinal fluid, supporting the action of morphine only on the central opiate receptors.

Brain↗
PubMed1988

[Acupuncture meridians demythified. Contribution of radiotracer methodology].

Radioactive trajectories can be visualized by injecting a radioactive tracer, technetium 99 m, at the site of acupuncture points. To determine the exact nature of these trajectories we performed several experiments on healthy volunteers, and our results may be summarized as follows. The target organs of technetium 99 m, and notably the thyroid gland, were always visualized. The circulating radioactivity, visible on scintiscans and confirmed by venous blood counts, was not negligible. The radioactive trajectories we observed were often divided at their starting point and did not extend along the whole length of the acupuncture meridians they might have made visible. The radioactive trajectories disappeared after venous blockade to reappear when the blockade was lifted. Finally, the radioactive trajectories obtained were very similar after injection at the acupuncture point and at a control point. These findings indicate a lymphatic and venous drainage of the radioactive tracer at the site of injection followed by transportation through the veins, rather than visualization of acupuncture meridians as suggested by some authors.

Acupuncture Therapy↗
PubMed1988

[Quantitative renal scintigraphy with technetium-labelled dimercaptosuccinic acid in children].

Separate measurement of renal function is essential in children with urinary tract disease. This can be done satisfactorily by means of kidney scintigraphy with technetium 99m-labelled dimercaptosuccinic acid. A retrospective study of the records of 415 children, which comprised renal function tests, radiology and scintigraphy, confirmed the value of the radioisotope technique. Graphs of height, kidney uptake and kidney uptake density in relation to age were established, showing highly significant correlations with renal function tests and intravenous urography results, but many dissociations were encountered. Separate renal function evaluation by radioisotope scintigraphy seems to be more reliable than evaluation extrapolated from measurement of the cortical areas at intravenous urography. In vesico-ureteral reflux scintigraphy makes it possible to detect reflux nephropathy at an earlier stage than with other methods.

Age Factors↗
PubMed1988

Influence of the menopause and aging on spinal density in French women.

Dual photon absorptiometry (DPA) was used to measure the bone mineral density (BMD) of the lumbar spine in 510 normal women from the south of France. Long-term precision was 2.2%. BMD was stable in young adults and again in women over 70 years of age. Perimenopausal women at an average age of 51 years already evidenced a slight bone diminution (5%) compared to young adults and women within 2 years of the menopause already had a 10% diminution. The average rate of apparent bone loss in this cross-sectional study was 1% per year from age 45 to 65 years, but about 75% of this decrease occurred in the first decade after the menopause. Spinal BMD in our normal French population appears to be 5-10% lower than US values.

Adult↗
PubMed1976

Activity of anti-inflammatory drugs on an experimental model of osteoarthritis.

Osteoarthritis was induced in the rabbit by a single intra-articular injection of 0.1 ml of a 1% solution of papain. Degeneration of the cartilage was studied 3 hours, 1, 3 and 8 days after the injection by transmission electron microscopy (TEM) and quantified by measuring the fixed charge density (FCD) and 35S incorporation into glycosaminoglycans. TEM observations of chondrocytes revealed a close correlation between the development of this experimental degenerative joint disease and human osteoarthritis. The administration of CH3-prednisolone (0.1 mg/kg on the 2nd and 5th days, i.a.), of indomethacin (1 mg/kg per day X 7, i.v.), and of catalase (50,000 IU/kg per day X 7, i.m.) modified the biochemical parameters measured 8 days after the papain injection. The corticoid potentiated the action of papain (fall in GAG content and synthesis). None of the non-steroid anti-inflammatory drugs modified the FCD. On the other hand, the increase of 35S incorporation was low after indomethacin and very high after acetylsalicylic acid. Catalase brought about an almost complete recovery of GAG content, together with an important increase in 35S incorporation. This arthropathy could be widely used in experimental pharmacology as a selective test and as a means of studying the mechanism of action of osteoarthritic drugs.

Animals↗
PubMed1975

[Use of leukocytes labelled with 99m Technetium sulfide colloids for the detection of experimental aseptic inflammatory foci].

The authors propose a technique of labelling of leukocytes based on the phagocytic power of these cells with regard to sulphide particles in the colloidal state labelled with 90mmTc. These labelled leukocytes maintain their normal function and can be detected in the inflammatory foci created in experimental animals in the form of an abscess. Satisfactory results were thus obtained by scintiscanning after auto and allo-transfusion of labelled leukocytes. The role of hyperemia in the results obtained is eliminated by comparative study using non-diffusible vascular tracers. The type of vector, tracer and marker, the innocuity of the method suggest that it may be used in human clinical medicine for the early diagnosis of certain inflammatory foci.

Abscess↗
PubMed1975

[Muscular work and its hyperemic phase in the patient with arteritis].

Already users of a method of functional assessment of the muscular circulation in the patients with peripheral artery disease by Xenon 133, the authors propose a radical modification of the performance of the exercise test. A quantified exercise test leads to a new and more objective interpretation of the radio-active tracer elimination curve. This new method permits the measurement of the total quantity of blood which passed during the hyperhaemic stage and its time distribution. The aim of this test is to form an opinion on the tenacity and the efficiency of the supplementary mechanisms when there is an occlusion of the arterial axis.

Adult↗