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Biomedical subjects

M von Ardenne

Publications and source records attributed to M von Ardenne.

At least 19 recordsLinked to original sources
PubMed1979

On the optimization of local hyperthermy in tumors based on a new radiofrequency procedure. Local hyperthermy of large body areas using the CMT selectotherm method.

A new radiofrequency procedure, i.c., the CMT Selectotherm technique, permits to convey large heat quantities per volume unit also to deep-seated tumor tissues without causing thermal lesions in healthy tissues near or at the body surface. The improved spatial homogeneity of energy supply attainable by this method is demonstrated by measurements at a gelatine phantom and, in particular, by in vivo measurements on pigs. The appliability of local hyperthermy to tumors localized in different parts of the body is substantially improved (a) by the principle of superimposing local hyperthermy on an elevated temperature level of metabolically induced whole-body hyperthermy (CMT-spontaneous hyperthermy at 40 degrees C) and (b) by the principle of selective increasing the thermal sensitivity of tumor tissues by decreasing the pH in these areas (the CMT main step). It is shown that the temperature dose T. deltat necessary for the selective occlusion of the vasculature in tumor tissues can be obtained by the CMT Selectotherm process also in deep-seated tumors. This process is part of the 1977 CMT concept. The fundamentals of optimizing local hyperthermy with consideration of heat dissipation from the tissue by heat conduction and convection via the blood stream are demonstrated. Temperature profiles are calculated for some practice-relevant, typical examples (inner and outer parts of sphero-symmetrically shaped tumors). Finally, in vivo measurements and calculations on the time course of temperature under certain conditions and for different tissue layers are discussed.

Bioelectric Energy Sources↗
PubMed1979

[Tumor hyperacidification through glucose infusion enhanced by local hyperthermia (author's transl)].

Local tumor hyperthermia (42--43 degrees C) during moderate whole body hyperthermia (40 degrees C) and hyperglycemia (5 . 10(-3) g ml-1) led to an amplification of tumor hyperacidification of deltapH = 0,47 +/- 0,19 In 12 from 20 animals. As cause of this phenomenon the stimulation of glycolysis by temperature increase (van't Hoff's law) and the stop of microcirculation by hyperthermia plus decrease of erythrocyte flexibility was discussed 5 tumors regressed totally.

Animals↗
PubMed1979

[Calculation of the dynamic heating process in multilayer model tissues during local hyperthermy using the CMT Selectotherm technique (author's transl)].

The hyperthermic dose necessary for triggering the mechanism of irreversible occlusion of vessels in cancer tissues was assessed to be in the order of 42 degrees C--30 min. (Compare: using hyperthermy without adjuvant measures, the temperature dose needed is at least 42.5 degrees C--140 min) In order to avoid any impairment of skintight tissue and to apply the temperature dose 42 degrees C--30 min also to deep-seated tumors which might be surrounded by normal tissue well supplied with blood, we developed a two-stage local hyperthermy technique with homogenized energy supply to different body sections according to the CMT Selectotherm scanning principle. The method and the results of heat-theoretical calculations made for understanding the dynamic heating process in multilayer tissue models are reported. Employing an electronic computer we succeeded in calculating convenient parameters for an improved applicator system of our CMT Selectotherm device as well as in determining the time course of the spatial temperature topography in three--or fourlayered model tissues under different conditions. It follows from the calculated data that the therapeutic applicability of his new local hyperthermic method can be decisively improved by intensive skin cooling and by short-term manipulation of blood-flow parameters (e.g., by unbloody localized blood pressure reduction). Finally, it is emphasized that the empirical use of hyperthermy in cancer treatment, as it has been employed by other clinical research groups up to now, seems to be no longer responsible. Due to the complicated interrelationships of therapeutically relevant factors, only a solid theoretical standpoint based on and controlled by many thousands of experiments (measurements) provides both an useful procedure adapted to every individual case and the maximum prospects of success.

Blood Flow Velocity↗
PubMed1978

[Manipulated hyperacidification of autochthonous tumors].

Measurement on 3,4-benzopyrene- and methylcholanthrene-induced tumours of the rat (and mouse) showed that the multiple established manipulated hyperacidification of transplantation tumours to values about pH 6 is possible also on autochthonous tumours.

Animals↗
PubMed1978

[The time lapse of the cytostatic effect of ifosfamide].

The time lapse of the effect of ifosfamid on the solid DS carcinosarcoma has been studied using 204 Wistar rats. The main results and the conclusions are as follows: 1. The transplantability of the tumor is abolished two hours after the i.v. application of 180 mg/kg isofamid (cessation of tumor cell proliferation). 2. Yet, the tumor tissue to be grafted is not damaged thoroughly by this treatment. It is possible that the still viable tumor cells were killed by the non-suppressed immune system of the recipients. 3. As determined by trypan blue dye exclusion and registration of glycolytic activity, the main part of tumor cells remains viable. As lately as 4 days after the therapy 80% of the cells incorporate trypan blue and the glycolytic activity is inhibited in the order of 80%. 4. It is to be expected that within two hours, a period sufficient for proliferation inhibition of tumor cells, only 30% of the active form of the drug administered can be found in the tumor. In this context the toxification (activation) kinetics of ifosfamid is discussed and an optimized, programmed infusion is considered. 5. The treatment with ifosfamid does not affect at least up to the third day the tumor hyperacidification attainable by a long-lasting glucose infusion.

Animals↗
PubMed1978

[Principles and 1977 concept of cancer multistep therapy. Physiological fundamentals of the new timing. Selectotherm local hyperthermy (author's transl)].

A report is given on the further development of the Cancer Multistep Therapy (CMT) Concept. With a clinically applied blood glucose concentration of 5 . 10(-3) g ml-1 the pH value in tumour tissue reduces to about 6.0 which, in turn, causes an increase in thermal sensitivity of cancer cells by approximately 2 degrees C. At the same time, their proliferation ceases almost completely. In addition, the pH value at the venous end of capillaries in tumour tissue increases to about 6.5 so that the flexibility of the erythrocytes gets lost in a selective mode. From this it follows that, under CMT conditions, there will be a total decrease of microcirculation in tumour tissues. All the aforementioned facts have been considered by a new timing: applying cancerostatic drugs and/or ionizing radiation prior to the said drop of microcirculations and of cancer cell proliferation rate. The begin of the hyperthermy step is then planned to take place immediately after the decrease of microcirculation in tumour tissue since the action of the discussed local hyperthermy then becomes very strong (pronounced selective reduction of convection cooling by the blood stream; further enhanced thermal sensitivity of cancer cells). Local hyperthermy then is performed by superposing the Selectotherm Process on 40 degrees C whole-body hyperthermy which allows high power densities also with deep-seated tumour tissues. Finally calculated temperature profiles in tumour tissue of various diameters are discussed together with the practice-considered parameters used in the respective equations.

Antineoplastic Agents↗
PubMed1978

[Overacidified tissue and microcirculation (author's transl)].

A discussion of physiological fundamentals with respect to the inhibition of blood microcirculation in (tumor) tissue at reduced pH values around 6.0 is followed by a report on principles, design and results obtained with a light probe array which permits to determine in vivo reference values of the relative intensity of microcirulation in both normal and tumor tissues under various conditions. An analysis of the discussed records has shown that--as compared to a value of 80-66% without glucose infusion--the relative mean intensity of microcirculation in tumor tissue drops to approximately 8-4% about 300 min after the onset of glucose infusion under CMT administration at 37 degrees C. By adding the CMT step of hyperthermy, the relative mean intensity of microcirculation--compared to normal tissue at 37 degrees C--will further drop below 1%. With such a decline of microcirculation--and an adequate duration of, say, 8 hours--local hyperthermy at 41-42 degrees C is likely to cause a very pronounced damaging action on tumor tissue because the then noticeably reduced substrate offer proves to be insufficient to ensure the structure-maintaining metabolic rate of cancer cells.

Animals↗