Rudolf Schosser

MIC-III — an integrated software package to support experiments using the radioactive microsphere technique

MIC-III is a versatile program system to support gamma spectrometry data management and data collection for experiments using the radioactive microsphere technique. It is mainly written in PASCAL and running on a minicomputer. Hierarchical organ dissection schemes are used for unique classification and identification of samples. For each series of experiments, up to 12 different nuclides and up to 20 different organ dissection schemes can be handled simultaneously. Sample weights are collected on-line and sample radioactivities are measured automatically by gamma spectrometry under process control. The spectra with a resolution of 1022 channels are analyzed using a modified linear regression technique and a strategy to compensate for global spectrum shifts. The spectrum deconvolution algorithm was evaluated by calculating the recovery indices for known nuclide mixtures and compared to the stripping method, matrix method and a linear regression technique using window counts. Recovery values produced by MIC-III are better balanced than those of the other methods. MIC-III showed the smallest dispersion of the recovery index and exhibited least error accumulation in case of spectrum shift. MIC-III computes regional blood flow and arterio-venous shunt, and provides interfaces to customized programs or statistical software packages for further analysis. It has successfully been employed in more than 140 experiments.

Open chest and open pericardium affect the distribution of myocardial blood flow in the right ventricle

SummaryWe have investigated the effects of open chest and open pericardium on the distribution of myocardial blood flow assessed with the radioactive microsphere technique (15 μm). Five dogs with intact thorax served as controls (group I) and six dogs were studied after a right-sided thoracotomy and pericardiotomy (group II). Global myocardial blood flow (mean±S.D.) was 0.73±0.17 ml·min−1·g−1 in group I and 1.22±0.09 ml·min−1·g−1 in group II (p<0.05). Analysis of transmural blood flow distribution revealed that flow was 44% higher in the right and 60% higher in the left ventricular endocardial layers in the open-chest animals, whereas epicardial flow increased by 105% and 90%, respectively. As a result of the preferential blood flow to the epicardial layers of the right ventricle, the endo/epi ratio was reduced from 1.30±0.26 in group I to 0.86±0.11 in the open-chest group (p<0.05). Left ventricular endo/epi ratio was 1.27±0.16 and 1.06±0.11 (n.s.), respectively. External work and diastolic filling pressure of the right ventricle did not differ between the two groups and therefore cannot account for the redistribution of myocardial blood flow. It is concluded that the distribution of myocardial blood flow, particularly in the RV, is severely disturbed by thoracotomy and pericardiotomy. This is an important aspect for the planning and evaluation of studies under open-chest/open-pericardium conditions.

Perfusion of the interventricular septum during ventilation with positive end-expiratory pressure.

ObjectiveTo determine whether regional hypoperfusion of the interventricular septum occurs during ventilation with positive end-expiratory pressure. DesignAnimal study. AnimalsAnesthetized, closed chest dogs (n = 8). InterventionsInduction of experimental adult respiratory distress syndrome (ARDS) and then ventilation with 10,15, and 20 cm H2O of positive end-expiratory pressure. Measurements and Main ResultsCardiac output and regional interventricular septum blood flow ‘were assessed at control, at induction of experimental ARDS, and at each level of positive end-expiratory pressure. Ventilation with 20 cm H2O of positive end-expiratory pressure decreased cardiac output (-32% vs. control, p <.05), and did not change absolute, but increased relative (to cardiac output) interventricular septum blood flow. During experimental ARDS and ventilation at 20 cm H2O end-expiratory pressure, there was a redistribution of flow toward the right ventricular free wall (+93%, p < .001) and the right ventricular part of the interventricular septum (+68%, p < .01), while flow to the left ventricular interventricular septum and to the left ventricular free wall remained unchanged. Locally hypoperfused interventricular septum areas or findings indicative of interventricular septum ischemia were not observed during positive end-expiratory pressure. ConclusionsThe decrease in cardiac output during positive end-expiratory pressure is not caused by impaired interventricular septum blood supply. The preferential perfusion of the right ventricular interventricular septum indicates increased local right ventricular interventricular septum oxygen-demand and suggests that during positive end-expiratory pressure, this part of the interventricular septum functionally dissociates from the left ventricular interventricular septum and the left ventricular free wall to support the stressed right ventricle.

Right ventricular tissue PO2 in dogs. Effects of hemodilution and acute right coronary artery occlusion.

SummaryRight ventricular (RV) epicardial tissue oxygen pressure (PtO2) was measured polarographically by means of a platinum multiwire surface electrode on the in situ beating heart of ten anesthetized dogs prior to and after moderate (Hct 28%) normovolemic hemodilution (HD) with dextran 60. In five dogs the effect of acute occlusion of the right coronary artery (RCA) on PtO2 was analyzed.The PtO2 histograms at baseline revealed a bell-shaped configuration and a mean PtO2 of 46.2 ± 7.1 mm Hg which coincides with the PtO2 on the left ventricle (LV) reported by others. After HD mean PtO2 increased to 51.4 ± 8.5 mm Hg (P = 0.02) without alterations of the histograms configuration. Hemodynamics and blood gas analyses were unchanged after HD. RCA ligature was followed by non-uniform changes in the PtO2 pattern.Thus, despite marked differences in external work and O2 consumption, the PtO2 in both RV and LV myocardium are similar at rest. The increase of PtO2 in the RV at reduced Hct values, which is not seen in the LV myocardium, can be related to differences in functional capillary density between both ventricles.

Blood flow measurements by means of radioactive microspheres. A useful technique in malignant tumors

MEASUREMENTS of blood flow in lymphatic metastases of the SMT-2A mammary adenocarcinoma in W/Fu rats were recently reported by R. L. Jirtle [1]. Twenty-five/~m microspheres (MS), labelled with either 57Co or 113Sn, were used to differentiate between flow to the outer and central regions of tumor and tumor metastases. Even though such studies should be essential for planning and evaluating tumor treatment, there are three main drawbacks in the above study concerning the technique of utilizing radioactively labelled MS: (1) For this method to determine blood flow, MS should all be trapped in the terminal vascular bed without deteriorating the circulation. Consequently, to assess the proportion of trapped and still circulating MS, simultaneous reference sampling from the arterial and venous line is inevitable [2]. With a venous reference sample, one could distinguish between nutritional and non-nutritional flow in a malignant tumor. This differentiation has not been performed in the above study, although effective tumor treatment depends on nutritional blood flow only. (2) 240 g rats received approximately 70,000 MS. Cardiac output (CO) was calculated according to

Digital-image communication in the EC-project TELEMED

A pan-European telemedicine environment has been established in the frame of the EC- sponsored TELEMED project. Remote expert consultation in radiology using digital image communication has been developed and implemented as a demonstrator for advanced telecommunication applications in medicine. Eight European university hospitals have been interconnected using 384 kbit/s ISDN and 2 Mbit/s broadband networks. A set of requirements was derived and software for image and text communication, for image display and manipulation and for synchronization of remote workstations was developed. The benefits of digital image communication were demonstrated in evaluation experiments.

Videoconference as a tool for European interhospital consultations in radiology

In the frame of the EC-sponsored TELEMED project, videoconferencing was evaluated as a tool for Remote Expert Consultation (REC) in radiology. The REC environment has been established as a pan-European demonstrator for advanced telecommunication applications in medicine. Five European university hospitals have been interconnected using broadband networks at a speed of 2 Mbit/s and 140 Mbit/s. Videoconference was evaluated in more than 120 sessions. In the experiments, videoconference proved to be a useful tool for teleconsultations, providing a set of requirements identified as indispensable for medical videoconference such as remotely adjustable iris for the document camera are fulfilled. Diagnostic reliability of images recorded with our equipment proved acceptable for digitally acquired images while reliability is limited for conventional images with a high demand of spatial and contrast resolution. Regional spin-off applications that have been established at some participating sites underline the potential of videoconference in health care.

Results of a Remote Expert Consultation Project

The application pilot “Remote Expert Consultation in Radiology” has been implemented between 8 university hospitals in 7 European countries as part of the EC-sponsored TELEMED project (R1086). Advanced telecommunication services like videoconference (VC) and digital image communication (DIC) have been evaluated regarding their usability for remote consultations. For this purpose ISDN and satellite or terrestrial networks at 2 Mbit/s or 140 Mbit/s line speed were utilized. In a prospective multicenter study, videoconference proved to be a reliable tool for diagnosing digitally recorded images while some classes of conventional images are subject to a significant loss of information and diagnostic accuracy. Digital image communication promises image transmission free-of-loss but still needs more development effort before being fully fit for use in clinical routine.

Remote expert consultation in radiology — The TELEMED project

A pan-European telemedicine environment has been established in the frame of the EC-sponsored TELEMED project. Eight European university hospitals have been interconnected using broadband networks from 2 Mbitls to 14 Mbitls. The application pilot is realized and evaluated in three steps of technical and functional integration, namely videoconference (VC), digital image communication (DIC), and access to an image reference data base. More than 120 ves have been conducted to evaluate radiological applications. In the experiments a number of requirements such as a remotely adjustable iris of the document camera have been identified as indispensable for medical VC.

The evaluation of radioactive microsphere data: remarks on the use of the BMDP and SAS statistical software packages.

We investigated the suitability of BMDP and SAS as an integrated tool for the evaluation of regional blood flow data obtained from the radioactive microsphere technique. Both packages were applied to a recent study on muscle blood flow with a 3-factorial design. The organization of data and files, the strategy of data reduction, and the evaluation by means of statistical and graphical techniques are shown. The method may be applied to any microsphere study design. A considerable amount of time can be saved and data integrity may be improved. The statistical quality of the results may benefit from the broad spectrum of statistical tests available.