Biomedical subjects

D Anhalt

Publications and source records attributed to D Anhalt.

6 recordsLinked to original sources

PubMed1990

Rapid admixture blood warming: technical advances.

The technique of rapid admixture blood warming of cold erythrocyte units is designed to warm erythrocyte units rapidly (less than 30 sec) while simultaneously providing saline for dilution. However, questions have been raised about the recommended use of a standard 250-ml bolus of 70 degrees C admixture saline, the uniformity and speed of blood unit warming, the difficulties inherent in keeping saline bags at 70 degrees C, and the safety of the methodology. To answer these questions, a series of tests were performed and modifications of the technique were introduced. The mean weight of 1000 successive units of erythrocytes for adult infusion was 305 g (range 220 to 410). The maximum temperature was 44 degrees C, using an internal temperature probe (1-cm temperature gradations; 2-sec recording intervals) when the smallest unit was admixed with a 250 ml 70 degrees C saline bolus; the largest unit had a minimum temperature of 30 degrees C. Plasma Hgb, osmotic fragility, and K of the minimum size erythrocyte unit showed no significant deviation from its control. Both thermographic photographs and the internal temperature recordings of the erythrocyte units demonstrated that solely due to fluid turbulence, uniform mixing occurs within approximately 30 sec of beginning the admixture process. Inverting the blood units caused a thermal layering of fluids and an unacceptable maximum blood temperature of 50 degrees C. There was no difference between the mixing time or efficacy in the presence of standard or large-bore iv tubing or additional in-line filters. Volumes of the 250-ml saline bags for admixture decreased markedly with deviations in electrolyte composition after greater than 2 wk at 70 degrees C.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Transfusion↗

PubMedDate not supplied

The efficiency of clinical microwave applicators measured by a calorimetric method.

When inducing localized hyperthermia for superficial cancer therapy with microwaves there has often been question about the total power output from the applicator. Although specific absorption rates and thermograms are used to obtain localized power distributions and heating patterns, these provide, at best, only an approximation of the total power applied to tissues or phantoms. In this paper a calorimetric technique for obtaining total microwave output power from applicators is described. An experimental apparatus was constructed and it was found to be accurate to approximately +/- 5 W. The power output from four clinical microwave applicators as a function of applied electric power was measured and the efficiency was found to be 40% in average. Along with enhancing quality assurance, the areas of hyperthermia research which may benefit the most from this calorimetric technique are computer modeling and patient treatment planning.

Calorimetry↗

PubMedDate not supplied

Thermocouples--the Arizona experience with in-house manufactured probes.

The performance of several different types of multisensor thermocouple probes have been tested to determine the feasibility of each type for use in the hyperthermia clinic. All of the probes tested were manufactured in-house, and a detailed description of the construction process will be presented. The overall performance of the probes in terms of robustness, calibration, conduction errors, and response time will be described. In particular, this study describes our experience with in-house manufactured thermocouples over the past several years. The results indicate that when strict quality assurance guidelines are followed, in-house manufactured thermocouples perform satisfactorily--thereby providing an alternative to purchasing probes and measurement systems from commercial vendors if the proper resources are available.

Feasibility Studies↗

PubMedDate not supplied

A scanned, focused, multiple transducer ultrasonic system for localized hyperthermia treatments.

A commercial diagnostic ultrasound scanner (Octoson) was modified for performing hyperthermia treatments. The temperature elevations were induced in tissues by four large, focused ultrasonic transducers whose common focal zone was scanned along a computer controlled path as determined from B-scan images. The system is described and the results of preliminary tests demonstrating some of its capabilities are given. Extensive tests with canine thighs and kidneys were performed. The blood flow to the kidneys was controllable, and thus tumours having different blood perfusion rates could be simulated. The results showed that the system is capable of inducing a local temperature maximum deep in tissues (up to 10 cm was tested) and that tissues with high perfusion rates could be heated.

Animals↗

PubMedDate not supplied

The CDRH Helix: an in vivo evaluation.

The Helix is an electromagnetic heating device used to induce regional/systemic hyperthermia for cancer therapy. It is a resonant device operating at about 82 MHz with an aperture size of 60 cm x 40 cm (elliptical) x 40 cm long. The Helix deposits power in tissues (or phantoms) by producing a predominantly axial electric field within its radiating aperture. Five pig experiments were performed to provide in vivo verification of specific absorption rate (SAR) measurements and electric field measurements which were obtained earlier in tissue-equivalent phantom and 0.9% saline, respectively. In addition to verifying the power deposition patterns found in phantoms, the pig experiments provided valuable insight into the capabilities and limitations of electromagnetic regional heating. For example, a kidney with limited blood flow, simulating a necrotic tumor, heated very well-although the highest temperature was not always measured there. Also, fat heating may be a problem, since excessive temperatures in the fat were observed in approximately 20% of the heatings. This paper compares the in vivo temperature measurements in pigs with SARs and electric field measurements obtained in phantoms, and also provides a brief overview of results of the Helix in clinical situations.

Adipose Tissue↗

PubMedDate not supplied

Temperature distributions during clinical scanned, focused ultrasound hyperthermia treatments.

In this study a scanned focused ultrasound (SFUS) system was used to heat 66 tumours at various anatomical locations in 52 patients. A total of 160 treatments were given. On average, temperatures were measured in 14 or 15 locations in the scanned volume. The time-averaged temperatures over the 30 min treatment period in the best treatment of each tumour were 44.0 +/- 2.4 degrees C (mean +/- SD) and 39.6 +/- 1.5 degrees C at the location of the highest and lowest sensor, respectively. On average, 39% of the sensors were above 42.5 degrees C. When only the cases that were judged to be good candidates for the hyperthermia device were analysed, 64% of the sensors reached a temperature over 42.5 degrees C with the highest temperature achieved being 45.9 +/- 2.3 degrees C and the lowest 40.7 +/- 1.4 degrees C. Although the system tested has many technical limitations (for example, fixed frequency, beam geometry and power during the scan cycle), the results demonstrate that therapeutic temperatures can be achieved in many tumours. Significantly better temperatures are expected when all of the theoretical potential of scanned focused ultrasound systems has been used.

Body Temperature↗