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Biomedical subjects

R Brennecke

Publications and source records attributed to R Brennecke.

At least 55 records · Page 3Linked to original sources
PubMed1995

[Reconstruction methods for 3D imaging and quantification of intracoronary ultrasound cross-sectional images using biplanar fluoroscopy. Initial experiences in vitro and in vivo].

In this investigation, we studied the feasibility of 3D-reconstruction from 2D cross-sectional intracoronary ultrasound images. A computer-aided, automated 3D-reconstruction was used to generate cylindrical and sagittal format of vessels in vitro (n = 9) and in vivo (n = 48). Ultrasound 2D-images were acquired with a 20 MHz mechanical intracoronary ultrasound catheter (Boston Scientific). A slow pullback (about 1 mm/s) of the catheter was performed during continuous recording of the ultrasound images. The recorded 2D-images were then fed to an image processing computer. Correction and scaling of the axial vessel dimensions was performed by the assessment of the catheter position in the simultaneously recorded biplane fluoroscopy. Digitized data were then processed to 3D-images with use of voxel space modeling. The 3D-views from any plane can be reconstructed. The in-vitro study demonstrated that the reconstructed images were able to correctly portray the pathological changes of the vessel wall in all specimen as proved by pathologic examination. In the in-vivo study, 3D-reconstruction provided not only a spatial visualization of the coronary arterial disorders (such as coronary aneurysm, coronary dissection, spontaneous plaque rupture etc.) but also provides the potential to quantify the mass of lesions. By combining sagittal and cylindrical views, 3D-reconstruction enables longitudinal and orthogonal imaging of the both the vessel lumen and vessel wall, therefore, it has the advantage of cross-sectional viewing as obtained from intracoronary ultrasound and the longitudinal viewing as derived from coronary angiography. These preliminary results of the study indicate that 3D-reconstruction of coronary segments is a promising technique for studying coronary artery disease. Analysis can be based not only on single or multiple cross-sectional images but also on vessel segments facilitating serial studies as for instance studies assessing the progression and regression of atherosclerosis.

Aortic Dissection↗
PubMed1994

[Responsibilities and problems in national health reporting].

Complaints about the inadequate data situation in public health services are not new. However, during the course of the past few years there have been significant developments: the board of experts for concerted action in the public health services requested an improvement to the situation and the Federal Government promoted a preliminary study on the establishment of a national health reporting system (GBE) in Germany. Under the responsibility of the Federal Statistics Office, a national GBE is currently being established through further promotion by the Federal Ministry for Research and Technology (BMFT) and the Federal Health Ministry (BMG); the standard users of this system will be both the general public as well as the bodies responsible for health policy and scientific research. In the public health services there exist complete, but improveable data sources or incomplete sources requiring selection; also, new data sources must be won. In establishing the GBE, it is being assumed that public health services participants willing to cooperate already have at their disposal extensive data that does not need to be newly acquired, but does need improved mutual co-ordination. The GBE can be established on this. Further supplementary data acquisition is only being considered for a later stage.(ABSTRACT TRUNCATED AT 250 WORDS)

Data Collection↗
PubMed1993

Variations in acoustical beam properties of intracoronary Doppler catheters.

The limitations of coronary angiography in assessing the functional significance of coronary obstructions is well known. While the critical variable of coronary blood flow cannot be readily measured, intraluminal Doppler sonography offers useful related functional information on blood flow velocity. In order to fully evaluate Doppler signals it is essential to have exact knowledge of the transducer transmission characteristics and of the ultrasound beam topology. In an experimental set-up, the transmitter-receiver characteristics of five commonly used Doppler catheters were investigated. In comparing the beam characteristics we found inhomogeneities in the lateral beam spread. At a penetration depth of 3.0 mm the beam shape varied from a minimum of 1.25 mm up to a maximum of 3.5 mm. The mean was 2.25 mm. The different beam profiles of the investigated Doppler transducers cause an error in measuring the blood flow velocity. The blood flow velocity tends to be underestimated the more the vessel diameter and the blood flow velocity increase. Contrary to transducer design optimized for imaging, for spectral analysis of the Doppler signal it would be advantageous to have as broad a beam as possible in order to illuminate the entire vessel lumen.

Angioplasty, Balloon, Coronary↗
PubMed1993

[Incidence of psychiatric diseases in the patient sample of a general practitioner--a case study of ambulatory management of psychiatric patients].

A prevalence study carried out in Berlin aimed at determining the incidence and distribution of psychiatric diseases among the patients treated by a general practitioner. A questionnaire had to be completed by the patient and by the physician at every consultation. This form comprised not only questions regarding the patient's main concern and self-assessment in respect of physical and mental complaints, but also a list of actual signs and symptoms of physical and mental disorders as well as questions on demographic and social variables. The physician was asked to state details on findings, principal and secondary diagnoses, kinds of therapy and also the time the consultation lasted. The results show clearly that psychiatric diseases occur in the general practitioner's consultation-room and in his practice in a proportion that is large indeed; and that the patients' self-assessment regarding the predominantly" or exclusively" mentally conditioned nature of their complaints and the formulation of their main mental concern of frequent affirmative answers in the list of mental complaints largely correlated with the statements regarding mental or psychiatric findings or principal diagnosis made by the physician. There were also clear interrelations with demographic and social variables, particularly in connection with the kinds of therapy that had been selected. On the whole, this study showed once again clearly that mentally diseased patients do not receive all the satisfactory and appropriate treatment of which they stand in need.

Adult↗
PubMed1992

Intravascular ultrasound imaging of arterial wall architecture.

Intravascular ultrasound (IVUS) is a promising new technique for assessing vascular morphology and structure. Controversy exists whether the three-layer appearance of the arterial wall correctly reflects the histologic structures of the intima, media, and adventitia. We performed an experimental study to clarify the three-layer appearance. The vessel wall architecture was analyzed by IVUS on eight different kinds of plastic cylinders, 24 normal blood vessels from pigs, and 59 human arterial segments. A distinct three-layer appearance was observed on all the plastic cylinders when the ultrasound beam was perpendicular to the wall. A three-layer appearance was also seen in the arterial wall, in the muscular (iliac, femoral artery) and elastic types (aorta), when the echo beam was perpendicular to the vessel wall. The three-layer pattern was even observed on the arterial wall when the intima was removed. Furthermore, the removed intima itself provided a three-layer image. Histologic examination showed that there was no correspondence between the IVUS three-layer appearance and the intima, media, and adventitia. Moreover, we also performed IVUS on nine patients who suffered from aortic dissection. Intravascular ultrasonic visualization of the dissected intima showed a distinct three-layer pattern. The pattern disappeared when: (1) the echo beam was not perpendicular to the vessel wall; (2) there was connective tissue around the vessel wall; (3) there was arterial wall calcification; or (4) the vessel wall was too thick or the distance between the ultrasound transducer and the vessel wall was too large.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

[Acceptance of social security by the German population].

Against the background of persistent problems of financing and monitoring the system of social security as practised in the Federal Republic of Germany, empirical research into preferences and acceptance has gained increasing importance. The acceptance of social security by the population has been checked empirically by means of data of the Socio-Economic Panel. The following questions have been studied: Which degree of acceptance applies generally speaking to the existing system? Are there differences in respect of acceptance regarding the various subdivisions of social insurance and how are they to be explained? What are the conclusions that can be arrived on the basis of these results? Overall assessment of the indicators employed shows that on the whole a high degree of acceptance is accorded to the existing security system. It cannot be concluded from the results that a fundamental reorganisation of the entire system towards security mainly on the individual's own responsibility would be in accordance with the preferences of the great majority of the population. Reorganisation would have to reckon with a low acceptance level. However, the monthly contributions--especially in respect of sickness insurance--are considered to be too high by part of the population.

Germany↗
PubMed1991

[The effect of PTCA on clinical outcome in patients with coronary single vessel disease].

We evaluated a 3-year clinical follow-up in 53 patients with unsuccessful PTCA, due to failure to reach the lesion (control-group) in comparison to a "matched pairs" group of 53 patients, in whom PTCA had been performed (PTCA-group). There were no deaths in the PTCA-group compared to 3 deaths (5.7%) in the control-group (ns). Two patients (3.8%) and three patients (5.7%), respectively, suffered an acute transmural myocardial infarction during the follow-up period (ns). Coronary artery bypass grafting (CABG) had been performed in five patients (9.4%) following PTCA, and in 17 patients (32.1%) of the control-group (p less than 0.002). The overall rate of serious cardiac events (death, myocardial infarction or CABG) amounted to 13.2% (seven patients) in the PTCA-group and to 43.4% (23 patients) in the control-group (p less than 0.002). Only in the PTCA-group was a repeat PTCA performed in 15 patients (28.3%) with restenosis (p less than 0.00003). 35 of 53 patients in the PTCA-group (66%) and 27 of 50 survivors in the control-group were free of symptoms at the end of follow-up (ns). These results demonstrate that PTCA in patients with single-vessel disease is followed by a marked reduction of serious cardiac events, predominantly of bypass-operations, but the necessity of a second PTCA-procedure in case of restenosis has to be considered.

Angioplasty, Balloon, Coronary↗
PubMed1990

Analysis of risk factors for restenosis after PTCA.

To identify risk factors for restenosis, we evaluated data in 473 patients with single-vessel percutaneous transluminal coronary angioplasty (PTCA) and control angiography after 6 months. Restenosis, defined as (1) loss greater than 50% of the initial gain, and (2) stenosis greater than 50% was found in 138 patients (29.2%). Univariate analysis revealed eight factors related to restenosis: (1) duration of symptoms less than 1 month (P = 0.005), (2) unstable angina (P = 0.004), (3) high-grade stenosis before PTCA (P = 0.014), (4) large residual stenosis after PTCA (P = 0.001), (5) insufficient improvement of stenosis (P = 0.042), (6) prolonged single inflation time (P = 0.017), (7) prolonged total inflation time (P = 0.055), and (8) low inflation pressure (P = 0.028). Multivariate analysis revealed four factors significantly related to restenosis: (1) large residual stenosis after PTCA (P = 0.0001), (2) prolonged single inflation time (P = 0.0047), (3) unstable angina (P = 0.0127), and (4) high-grade stenosis before PTCA (P = 0.0179). Modification of procedural factors might be helpful to reduce the risk of restenosis after successful PTCA.

Aged↗
PubMed1990

Parametric assessment of myocardial perfusion during interventional cardiac catheterization by means of X-ray densitometry-short-and long-term results.

X-ray densitometric evaluation of digital subtraction angiocardiograms allows an assessment of myocardial perfusion by means of the parameter 'MEAN RISE TIME' (MRT), defined as the time from the onset of local myocardial contrast medium opacification to the point of maximum opacification. Best results are obtained when the response of that parameter is compared before and after stimulation of coronary flow by papaverine. A prolongation of this parameter, especially after papaverine, was indicative of an impairment of myocardial perfusion, when compared to the results of TL-201 scintigraphy. In 50 patients with single vessel coronary artery disease the results of MRT pre and post papaverine before and after coronary angioplasty, as well as after 6 months were evaluated for 204 post-stenotic regions-of-interest. Before angioplasty papaverine induced a significant prolongation of post-stenotic MRT was measured 2.3 s +/- 0.9 s vs 3.1s +/- 0.8s; p less than 0.01), while after successful angioplasty post-stenotic MRT was measured significantly shorter after stimulation of coronary flow (2.6s +/- 1.0s vs. 1.9s +/- 0.9s; p less than 0.01). This indicated an improvement in myocardial perfusion. Nevertheless, 16/50 patients still presented pathological results of post-stenotic MRT after papaverine, although angioplasty was regarded successful. These patients presented a markedly higher rate of restenosis (14/16 patients after 6 months), a higher rate of dissections at the dilation site and a higher rate of dilated vessels, supplying myocardial areas after a Q-wave myocardial infarction. Thus, these results demonstrate the additional information about the short-and long-term outcome of an angioplasty procedure by densitometric myocardial perfusion analysis.

Absorptiometry, Photon↗
PubMed1990

Short- and long-term outcome after PTCA in patients with stable and unstable angina.

Acute results and follow-up data over a period of 36 months after attempted PTCA in 406 patients with stable angina and 202 patients with unstable angina are reported. The rate of acute complications (death, myocardial infarction and bypass grafting (CABG) amounted to 1.5% in stable and 6.4% in unstable patients (P less than 0.005). Within the first week after PTCA a significantly lower percentage (1.7% vs 10.4%) of cardiac events (death, myocardial infarction, CABG and repeat PTCA) was observed in the stable group (P less than 0.001). During a 12-month follow-up period, another 16.3% of the patients in the stable group and 30.7% of unstable patients suffered a new cardiac event (P less than 0.001). The long-term follow-up of 36 months revealed no significant difference in the event rate between stable and unstable patients (5.4% in both groups). The cumulative rate of myocardial infarction within 3 years after PTCA was significantly lower (3.7% vs 9.4%) in the stable group (P less than 0.005). The cumulative mortality amounted to 3.0% in stable and 6.4% in unstable patients (P less than 0.05) and the incidence of repeated PTCA was 8.1% and 19.3% respectively (P less than 0.001). The crossover rate to CABG was 10.1% in stable and 17.8% in unstable patients (P less than 0.01). The total rate of any cardiac event thus amounted to 24.9% in stable and 53.0% in unstable patients (P less than 0.001) within a 3-year follow-up period. At the end of follow-up, 74% of the stable patients were asymptomatic, compared with 60% of unstable patients (P less than 0.01). 45% of the stable group patients and 28% of the unstable patients were not on antianginal treatment (P less than 0.01). We conclude that PTCA in unstable angina carries a markedly enhanced risk of acute complications and cardiac events in the early phase after PTCA. In the long run, patients with stable angina have a better quality of life with regard to medical treatment and angina symptoms.

Adult↗
PubMed1989

[Possibilities and limits of 2-dimensional echocardiography in quantitative image analysis].

By two-dimensional echocardiography left ventricular volumes can be measured and ejection fraction can be calculated. But volume and ejection fraction determination are combined with a systematic underestimation despite high correlation in comparison to "true volume", whereas cineventriculography systematically overestimates true volume. This echocardiographic methodological problem is related not only to tangential scanning but also to low lateral resolution yielding a reduced endocardial border delineation. Meanwhile, advanced transducer technology and digital imaging techniques with zoom and cineloop possibilities have improved endocardial border detection. In comparison to cineventriculography, volume determination by two-dimensional echocardiography has improved significantly in comparison to results in 1983; this improvement was mainly due to a better determination of endsystolic volume. Similarly, left ventricular contrast echocardiography using color coding with statistical analysis of digitized images enhanced the accuracy of analysis of global and regional left ventricular function. Transesophageal echocardiography will be used when there is reduced image quality of transthoracic echocardiography, for example, in obese patients or those with pulmonary emphysema or mechanical ventilation. Transthoracic echocardiography has become a routine method for assessing global and regional left ventricular function. Echoventriculography can be used in patients with renal insufficiency, anaphylactic reaction to contrast medium, and poor left ventricular function.

Algorithms↗
PubMed1989

[The status of echocardiography imaging].

After several decades of gradual technical improvement of echocardiographic imaging, these methods have now attained a level of performance that is not so much dictated by technical limitations as it is determined by constraints imposed by the underlying physical principles. Image quality of echocardiographic imagers is discussed in terms of the spatial, temporal, and graylevel resolution provided. The level of technical performance obtained recently improves essentially the clinical value of echocardiography. Application of contrast material requires new techniques of image display such as color superposition imaging. Image quality in Doppler or color flow imaging is essentially described in terms of spatial, temporal, and velocity resolution. Phantom studies are proposed for routine testing of the image quality provided by clinical echocardiographic instruments. We mention some expected developments concerning archival image storage and the integration of echocardiograms into cardiological databases or complete departmental information systems.

Echocardiography↗
PubMed1989

[Right heart ventriculography using Gelifundol].

Forty patients (14 women, 26 men, mean age 58 years) with suspected anomaly of the right heart and suspected tricuspid insufficiency or atrial septal defect were given four injections of Gelifundol in five-minute intervals via the right cubital vein. Before, during, and after each injection an echocardiogram was obtained (four-chamber-view). One subcostal view was recorded. Contrast echocardiograms were analyzed according to a subjective score scheme by two independent observers and by video-intensitometry. After injection of contrast medium no patient showed ECG changes, nor did any patient report side effects after the injection of Gelifundol. Concerning the subjective parameters there were no significant differences between both observers. Score points varied between 5.2 to 5.5, intensitometric maxima lay between 54.6 and 58.0 relative intensity units, and the half-time of the intensity maximum (T1/2) varied between 7.2 s and 8.1 s. There were no statistical differences between the two observers. In all patients a diagnotic improvement could be achieved. A tricuspid insufficiency which was not diagnosed in the native echocardiogram could be diagnosed in 13 patients with Gelfundol. Thus, Gelifundol seems well suited for the assessment of right ventricular lesions in man.

Adolescent↗