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Biomedical subjects

A van Aswegen

Publications and source records attributed to A van Aswegen.

At least 37 records · Page 2Linked to original sources
PubMed1987

Comparative radionuclide and thermodilution determinations of cardiac output and stroke volume in the baboon (Papio ursinus).

Thermodilution cardiac output determinations and multigated equilibrium blood-pool scintigraphy were performed in ten healthy chacma baboons (Papio ursinus). The correlation was moderately good between both the radionuclide and thermodilution stroke volume (r = 0.58, SEE = 3 ml; SVth = 0.78SVr + 15.6 ml) as well as the cardiac output (r = 0.72, SEE = 0.2 liter/min; COth = 0.56 Cor + 2.1 liter/min). The attenuation depth dr as determined by radionuclide techniques was found to correlate well with the radiologically determined values dx (r = 0.8, SEE = 0.4 cm; dx = 0.87dr + 0.72 cm) which validated the depth values used in the calculations.

Animals↗
PubMed1986

Radionuclide evaluation of left ventricular function in a distantly located intensive coronary care unit.

Regular evaluation of left ventricular (LV) function is important in assessing patients in an intensive coronary care unit (ICCU). An adapted first-transit (FT) technique was applied to 21 patients for calculation of LV ejection fraction (LVEF). In this method the radionuclide is administered directly into the right pulmonary artery through a Swan-Ganz catheter. High-quality LV images are obtained because of minimal activity in the right ventricle and left lung. Data were acquired on a distantly located on-line computer system to restrict equipment in the ICCU. LVEF from FT compared well with LVEF from gated blood pool studies (r = 0.91) but gave consistently lower values. The adapted FT method ensures improved counting statistics during LVEF determination and facilitates evaluation of LV wall motion in the ICCU patient.

Adult↗
PubMed1986

Radionuclide cholescintigraphic imaging: an evaluation of several 99mTc labelled hepatobiliary radiopharmaceuticals.

Recently, much interest has been shown in the development of 99mTc labelled cholescintigraphic agents for imaging the hepatobiliary tract. In this study six cholescintigraphic agents were compared in rabbits with respect to transit efficiency through the liver and the halftime on the washout portion of the liver time-activity curve. The agents compared were p-butyl-IDA (PBIDA), diisopropyl-IDA (DISIDA), two mebrofenin (MBF) agents and two pyridoxylaminates (PDA). Best transit efficiencies were obtained with MBF (34.1 and 31.2%) followed by PDA (27.7 and 24.9%) while DISIDA (23%) and PBIDA (19.3%) were the lowest. The same phenomenon was observed regarding the washout halftime, with MBF the most rapid (6.3 and 5.9 min), PDA more prolonged (10.1 and 12.0 min) and DISIDA and PBIDA the slowest (23.0 and 23.2 min). This study confirms the difference in physiological behaviour of the various cholescintigraphic agents and shows identical flow patterns for locally produced and imported compounds.

Aniline Compounds↗
PubMed1986

Radionuclide determination of absolute LV volumes: interstudy, interobserver and intraobserver variances.

The results of 22 absolute left ventricular volume (LVV) determinations by a radionuclide (RN) method are compared to the results obtained by contrast ventriculography (CV). Another 10 patients were analysed in order to evaluate the interstudy, interobserver and intraobserver variances. Good correlation was shown between the RN and CV measurements of the end diastolic volume (EDV), end systolic volume (ESV), stroke volume (SV) and ejection fraction (EF), but the RN method overestimates the EDV and ESV. The EF was underestimated, but no difference could be shown for the SV. On the inter- and intraobserver levels, regression analysis yielded excellent correlation (r greater than 0.99 in all cases) with no statistically significant difference (P less than 0.05). The interstudy variance was minimal as indicated by regression analysis (r greater than 0.87) and no statistically significant difference (P less than 0.05) could be shown between studies. The results indicate that the RN method of LVV determination can be used in intervention studies over a limited period.

Adult↗
PubMed1986

Left ventricular function evaluation using radionuclide methods in the intensive coronary care unit.

We describe an adapted first-transit (FT) technique to perform left ventricular ejection fraction (LVEF) measurements on patients with Swan-Ganz catheters in the intensive cardiac care unit (ICCU). The radionuclide is introduced directly into the right pulmonary artery through the catheter. High-quality images of the left ventricle are obtained owing to minimal activity in the right ventricle and left lung. LVEF measurements obtained by FT compared well with measurements obtained from gated blood pool studies (r = 0.91) but gave consistently lower values. The adapted FT method improves LVEF determination and left-ventricular wall motion evaluation in the ICCU patient.

Cardiac Catheterization↗
PubMed1985

Evaluation of (o)-[77Br]bromohippuran as renal tubular function agent.

(o)-[77Br]bromohippuran (BHIP) was developed as renal tubular function agent due to its favourable chemical and physical properties and compared to (o)-[131I]iodohippuran (IHIP). Renograms obtained from baboons were compared and absorbed radiation dose calculations performed. Although BHIP showed a delayed kidney uptake and washout pattern, good kidney clearance of the radionuclide was obtained after 30 min. Radiation dose values for BHIP were markedly lower than for IHIP indicating that larger activities of BHIP could be administered to increase counting statistics. BHIP imaging in normal volunteers did however not substantiate the favourable behaviour obtained in the primate.

Animals↗
PubMed1985

Persistent left superior vena cava detected with radionuclide angiocardiography.

A 28-year-old man presented with paresthesias, fatigue, central cyanosis, and erythrocytosis. A first pass flow study with Tc-99m as free pertechnetate was done, among other tests, to exclude a central shunt when a persistent left superior vena cava was incidentally detected. The value of radionuclide angiocardiography to examine the central circulation noninvasively was again illustrated in this case.

Adult↗
PubMed1983

Variation in left ventricular ejection fraction determination at rest and during exercise.

The results of multi-gated blood pool imaging (MBPI) for determination of left ventricular ejection fraction (LVEF) in 48 patients at rest and during exercise were analysed in order to evaluate observer variance and interstudy variance. Twenty-three MBPI studies carried out with the patient at rest and 37 studies carried out during graded ergometer exercise were analysed by two independent observers in order to determine intra- and inter-observer variance. On the intra-observer level regression analysis yielded excellent correlation between rest and exercise studies (r = 0,998 at rest, r = 0,964 during exercise), and showed no statistically significant difference (P less than 0,01); this was also true of the inter-observer measurements (r = 0,999 at rest, r = 0,988 during exercise). In order to evaluate interstudy variance, MBPI was repeated in 15 patients at rest. Interstudy variation of the LVEF was minimal as indicated by regression analysis (r = 0,98), and showed no statistically significant difference (P less than 0,01). During the repeat study a mean increase in the LVEF of 2,1% was obtained, but this difference was not statistically significant.

Adolescent↗
PubMed1983

Determination of right ventricular ejection fraction utilising a radionuclide washout technique.

A radionuclide washout technique (WO), for calculation of the right ventricular ejection fraction (RVEF) which is independent of the exact position of the right ventricular region of interest was evaluated and results compared with first pass (FP) and equilibrium gated blood pool (GBP) values. Regression analysis between RVEF values of 24 patients obtained from FP and WO yielded a correlation coefficient (r) of 0.89, while a slightly poorer correlation coefficient was obtained when FP and GBP were compared (r = 0.79) and between WO and GBP (r = 0.71). No significant difference between RVEF values calculated from the three techniques was found (P less than 0.05) on inter- and intraobserver level. The radionuclide washout technique yields an accurate determination of RVEF without the necessity of outlining the RV accurately.

Adult↗
PubMed1982

The imaging of myocardial perfusion with 81mKr during coronary arteriography.

The use of 81mKr was investigated for imaging myocardial perfusion during coronary arteriography using conventional catheters. When the significance of stenosis judged by arteriography is unclear, the effect on tissue perfusion can be established and the contribution to collateral flow by each artery separately evaluated. The distribution of 81mKr, due to its 13-s half-life, represents regional blood flow. In order to evaluate interventions, studies can be repeated at a low radiation risk to patients. A sterile pyrogen-free 81Rb-81Kr generator was developed. With slow infusion, inadequate mixing and streaming takes place due to laminar flow in coronary arteries. Fast intermittent 3-ml 81Kr-dextrose bolus injections convincingly eliminated streaming artefacts. Imaging was performed in 13 patients with a mobile scintillation camera and digital imaging system. Blood flow was calculated using the inert gas washout technique. There was good correlation (r = 0.91) between coronary blood flow determinations using 81mKr and 133Xe respectively. The perfusion images correlated well with the coronary angiograms. Total coronary arterial occlusions as demonstrated by arteriography were all shown as perfusion defects during rest. During atrial pacing myocardial flow was increased two-fold in normal coronary arteries and to a lesser extent in arteries with significant disease. The most critical lesion in a branch of a left coronary artery leads to a redistribution of perfusion during pacing.

Angiography↗
PubMed1981

[Radionuclide exercise gated studies in female patients with positive exercise electrocardiogram].

Radionuclide left ventricular ejection fraction (LVEF) has been determined in a group of 14 female patients at rest and during graded supine bicycle exercise. One group consisted of 9 patients complaining of chest pain and demonstrating positive exercise electrocardiography (EECG), but with normal contrast angiographic results. The second group of 5 patients had a normal response to EECG and was used as a control group. LVEF increased markedly in both groups during exercise. This study confirms the known fact of high false-positive EECG in female patients and that exercise radionuclide LVEF response can be used as a final screening test for cardiac catheterization in female patients demonstrating positive EECG.

Adult↗
PubMed1980

Temporal resolution requirements for left ventricular time-activity curves.

To investigate framing rate requirements for left ventricular (LV) time-activity curves, ECG-synchronized blood pool studies of 33 patients were compared to independent techniques for evaluation of LV function. There were no significant differences in LV ejection fractions determined using different framing rates. Systolic time intervals calculated from 64- and 32-point curves were similar and correlated well with those obtained by standard methods (r = 0.81, p less than 0.001). Results from 16-point curves were worse (p less than 0.02). There were no differences between peak ejection and filling rates obtained with 64- and 32-point curves compared to angiography, but the rates calculated using 16-point curves were significantly slower (p less than 0.05). The findings suggest that LV time-activity curves acquired at 16 frames per RR interval do not provide optimum quantification of LV function indexes other than the ejection fraction.

Electrocardiography↗
PubMed1979

Global and regional assessment of cardiac performance by ECG-gated radionuclide blood pool imaging.

A non-invasive method for evaluation of regional and global ventricular function by ECG-gated radionuclide blood pool imaging was developed. Cinematic image display is a sensitive method for evaluating wall motion to detect regional ventricular abnormalities and chamber size. A value of r = 0,86 and 0,85 was found for both fixed and variable area radionuclide methods when these ejection fraction values were correlated with cardio-angiographic ejection fraction values in normal subjects and in patients with myocardial infarction. The fixed area method underestimated the ejection fraction in patients with mitra valve stenosis, but this problem can be overcome with the variable area method. The technique developed cannot be used in patients with severe arrhythmias (r = 0,49 and 0,44).

Blood Circulation↗
PubMed1979

A krypton-81m generator for organ ventilation and perfusion investigations.

A sterile pyrogen-free generator for ultra-short half-life 81mKr has been developed. During initial loading, the binding efficiency of 81Rb is 90--99%. The count rate during perfusion is 3 x 10(5) counts per minute for a 1,9 GBq (50 mCi) 81Rb generator. The generator has been used for routine and special investigations of lung perfusion and ventilation and for myocardial perfusion during catheterization.

Heart↗
PubMed1979

Noninvasive evaluation of ventricular function in cystic fibrosis.

The cardiac function of 21 patients with cystic fibrosis was studied using radionuclides and M-mode echocardiography. The patients (mean age 13.2 years, range 4 to 27) had a wide range of clinical and pulmonary function abnormalities (mean Shwachman-Kulczycki score 62.1). Decreased right ventricular ejection fraction was found in 13 of 18 patients (72%); an additional four patients had abnormal septal motion on ECHO. Left ventricular ejection fraction was abnormal at rest in four patients (19%); an additional four patients had borderline low LVEF. The LV pre-ejection period to ejection time ratio increased significantly (i.e., worsening LV performance) with deterioration of S-K score, chest radiograph score, and forced expiratory volume in 1 second. Three of eight patients with normal LVEF at rest had an abnormal response to supine bicycle exercise: LVEF fell in two patients and was unchanged in one. Thus evidence of LV dysfunction was observed in seven of 21 (33%) of the patients; four at rest and in three only during exercise.

Adolescent↗
PubMed1977

Bone marrow imaging with 59Fe.

Commerically available collimators are not suitable for the visual demonstration of the kinetics of 59Fe, because of its physical properties. A locally designed collimator, that provides integral visual information of the whole body distribution of erythropoietic marrow, is discussed. Wholebody scans of 4 individuals are also included to demonstrate the capabilities of the collimator.

Adult↗