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Biomedical subjects

A Koivula

Publications and source records attributed to A Koivula.

46 records · Page 3Linked to original sources
PubMed1981

Epinephrine does not alter human intervillous blood flow during epidural anesthesia.

The effect of epinephrine given epidurally with local anesthetics on uterine blood flow is controversial. Previous work in pregnant ewes demonstrated a transient but significant (14 per cent) decrease in uterine blood flow when 2-chloroprocaine with epinephrine (10 micrograms/l) was used. The authors administered 2-chloroprocaine, 10 ml, with epinephrine (5 micrograms/ml) to 12 healthy women during the first stage of labor. By use of intravenously injected 133Xe, intervillous blood flow was measured before and 15-20 min after epidural anesthesia to a somatic level of at least T10. Intervillous blood flow did not change significantly despite a decrease in mean blood pressure of 11 torr. These conflicting results are probably best explained by methodologic and species differences. It is postulated that human placental vasculature, unlike that of the ewe, undergoes vasodilation when perfusion pressure is decreased to maintain placental blood flow.

Adult↗
PubMed1981

Elimination of extracranial blood flow during dynamic cerebral perfusion studies using diffusible and non-diffusible radioisotope.

The extracranial blood flow seriously complicates the interpretation of dynamic cerebral studies. To eliminate this, we used a blood pressure cuff placed around the head in 50 patients with no evidence of cerebrovascular disease. The pressure in the headband was increased to 30 mmHg above the patient's systolic pressure, and the first 60 sec static scintigram was taken exactly 3 min after the injection of 99mTc-pertechnetate. A second 60 sec static scintigram was taken without pressure in the headband at 6 min after injection. After correction for diffusion of tracer into extravascular compartments we could still show 13% reduction in counting rates over the hemispheric regions and 30% over the convexity regions during application of the pressure headband. With the Xenon method, the application of the headband appears to have insignificant influence on the results of cerebral perfusion. We thus recommend that a headband should be used for dynamic 99mTc-isotope cerebral circulation studies.

Cerebrovascular Circulation↗
PubMed1979

Epidural analgesia and placental blood flow during labour in pregnancies complicated by hypertension.

Placental blood flow was measured during the first stage of labour in pregnancies complicated by essential hypertension or severe pre-eclampsia using a 133Xe clearance technique before and after segmental epidural analgesia. Analgesia was produced with 0.5 per cent plain bupivacaine in six patients with essential hypertension and in 11 patients with severe pre-eclampsia. After segmental epidural analgesia the placental blood flow was slightly but insiginificantly improved in most of the patients with pre-eclampsia and in half of the patients with essential hypertension, thus suggesting this analgesic method to be safe in hypertensive pregnancies in the absence of any substantial change in systemic blood pressure.

Anesthesia, Epidural↗
PubMed1978

Investigation of gynecological cancer with nuclear magnetic relaxation methods.

Nuclear magnetic relaxation times T1 and T2 of cell water protons in benign and malignant uterine cervical tissue (37 samples taken from 22 patients) were measured using a resonance frequency of 19.8 MHz. The means of relaxation times recorded for malignant tissue were (mean +/- S.E.) T1 = 0.89 +/- 0.05 s, T2 = 0.072 +/- 0.009 s, and obtained from corresponding benign tissues (mean +/- S.E.) T1 = 0.72 +/- 0.01 s T2 = 0.056 +/- 0.003 s. The differences are statistically significant (T1:p less than 0.001, and T2:p less than 0.05). The effect of dysplasia and inflammatory changes in mucosa to the relaxation times were examined and the probable sources of error in the present method are discussed.

Carcinoma↗
PubMed1977

An intravenous isotope method for measuring regional cerebral blood flow (rCBF) and volume (rCBV).

The regional cerebral blood flow (rCBF), intial slope index (ISI), transfer time (th) and volume (rCBV) were measured simultaneously in 43 hospital patients using a 133Xe intravenous injection method and quantitative dynamic 99Tcm brain scintigraphy. The measurements were made with a gamma camera and the data processing interfaced with a small digital computer. The following mean values and standard deviations were obtained from 50 control hemispheres standardized to the age of 40 years: (formular): see article. Good agreement was found between the blood flow values determined from the intra-arterial and intravenous injection techniques.

Adolescent↗
PubMed1975

Nuclear magnetic relaxation in the cell.

The authors have measured proton relaxation times of gynecological cancer. T1 and T2 of human tumours are longer than proton relaxation times of corresponding normal tissues. Radiotherapy changes also proton relaxation times T1 and T2 in tissue.

Cell Transformation, Neoplastic↗
PubMedDate not supplied

Image technique optimization in MR imaging of a titanium alloy joint prosthesis.

The purpose of this study was to explore systematically the effect of the imaging parameters changeable by the user in spin-echo (SE) imaging sequences to minimize image distortion when imaging joint prostheses. A titanium alloy hip joint prosthesis was studied at I.O.T. The SE imaging parameters were bandwidth/pixel(BW/ p), TE, strength of encoding gradients (matrix size), echo train length (ETL), and direction of phase and frequency encoding. The effect of ETL in rapid acquisition relaxation enhanced (RARE) sequences was also evaluated with a turbo-SE sequence using a different ETL with the same TR and an effective TE. It is concluded that an optimized image quality can be achieved in SE imaging by using a high bandwidth/pixel value (at least 130 Hz/pixel), a high resolution matrix (256-512), sequences with multiple refocusing, and a frequency-encoding axis parallel to the long axis of the prosthesis. The degree of distortion is reduced with this optimized technique.

Alloys↗