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At least 271 records · Page 15Linked to original sources
PubMed1993

Liquid crystal skin thermometry: an accurate reflection of core temperature?

Oesophageal, rectal, bladder, tympanic and pulmonary artery sites are used intraoperatively to measure body temperature. However, the temperatures measured at each site have different physiological and practical importance. The present two-part study sought to compare liquid crystal (CR) skin temperature with other temperature monitors which are used routinely during surgery. The first part compared CR with oesophageal (OS) temperature during general inhalational anaesthesia. The second part compared CR with OS, pulmonary artery (PA), and bladder (BL) temperatures during the periods of rapid temperature change associated with cardiopulmonary bypass (CPB). During the first part, the mean difference between OS and CR was -0.14 +/- 0.85 degrees C; this difference remained consistent over time (P < 0.05 by repeated measures analysis of variance). During the second part, the difference in temperature readings between CR and each of the other monitors remained consistent except for CR vs PA and CR vs OS during the cooling period of CPB, when the iced cardioplegia slush directly affected the PA and OS temperatures. This study suggests that CR, an inexpensive and noninvasive means of temperature monitoring, reflects trends in temperature changes in the clinical setting.

Anesthesia, Endotracheal↗
PubMed1984

Demonstration of a problem in estimating sensible heat loss from the respiratory tract by thermometry.

We have investigated sensible respiratory loss, which is usually taken as the product of expired volume and the temperature difference between inspired and expired air (VE X delta T). Air temperature was measured with a 0.122 mm copper-constantan thermocouple mounted in the mouthpiece of a T-piece breathing system, and expired volume with a pneumotachograph. Changing air temperature (delta T) at the mouth and expired air volume (VE) were recorded simultaneously while the subject voluntarily breathed at different tidal volumes and rates. Inspired temperatures were controlled at 12.05 degrees C, 21.80 degrees C and 25.74 degrees C at a low dewpoint temperature of 4-5 degrees C. Temperature volume "loops" were constructed using an x-y plotter. The areas of each "loop" and enclosing rectangle (VE X delta T) were measured. The difference was divided by the weight of the rectangle to give the percentage of overestimation of sensible heat loss, which ranged from 5.5 to 17.2 per cent. The error increased significantly with decreasing tidal volume and increasing respiratory rate.

Body Temperature Regulation↗
PubMed1983

Differential thermometry as a monitor of blood flow in skin flaps.

An instrument for monitoring the blood flow in skin flaps by temperature measurement is described. This compares the temperature of the flap with adjacent normal skin. An experimental assessment of the technique is presented. Although many of the problems associated with absolute temperature measurement were eliminated, the reaction to circulatory change within a flap was slow. However, with further refinement, the principle may have a place in clinical practice, especially in replantation surgery.

Animals↗
PubMed1994

Theoretical estimation of the temperature dependence of backscattered ultrasonic power for noninvasive thermometry.

The backscattered signal received from an insonified volume of tissue depends on tissue properties, such as attenuation, velocity, density, and backscatter coefficient and on the characteristics of the transducer at the insonified volume. Analysis of scattering in response to a burst of insonification showed that the temperature dependence of backscattered power was dominated by the effect of temperature on the backscatter coefficient. The temperature dependence of attenuation had a small effect on backscattered power. Backscattered power was independent of effects of temperature on velocity. These results were seen in the analysis of two types of inhomogeneity: 1) an aqueous scatterer in a water-based medium and 2) a lipid-based scatterer in the same water-based medium. The temperature dependence of the backscatter coefficient was inferred assuming that the backscatter coefficient was proportional to the scattering cross-section of a small scatterer. Backscattered power increased nearly logarithmically with temperature over the range from 37 degrees to 50 degrees C. Our model predicted a change of 5 dB for the lipid scatterer and a change of up to 3 db for the aqueous-based scatterer over that temperature range. For situations in which temperature dependence of the backscattered power can be calibrated, it may be possible to use the backscattered power level to track temperature distributions in tissue.

Computer Simulation↗
PubMed1991

Experimental brain hyperthermia: techniques for heat delivery and thermometry.

An experimental canine brain model was developed to assess the effects of hyperthermia for a range of time and temperature endpoints, delivered within a specified distance of an interstitial microwave antenna in normal brain. The target temperature location was defined radially at 5.0 or 7.5 mm from the microwave source at the longitudinal location of maximum heating along the antenna in the left cerebral cortex. Temperatures were measured with fiberoptic probes in a coronal plane at this location in an orthogonal catheter at 1.0 mm intervals. Six antennas were evaluated, including dipole, modified dipole, and four shorted helical antennas with coil lengths from 0.5 to 3.9 cm. Antenna performance evaluated in tissue equivalent phantom by adjusting frequency at a fixed insertion depth of 7.8 cm or adjusting insertion depth at 915 MHz showed dipoles to be much more sensitive to insertion depth and frequency change than helical antennas. Specific absorption rate (SAR) was measured in a brain/skull phantom and isoSAR contours were plotted. In vivo temperature studies were also used to evaluate antenna performance in large and small canine brain tissues. A helical antenna with a 2.0 cm coil length driven at 915 MHz was chosen for the beagle experiments because of tip heating characteristics, well-localized heating along the coil length, and heating pattern appropriate to the smaller beagle cranial vault. Verification of lesion dimensions in 3-D was obtained by orthogonal MRI scans and histology to document the desired heat effect, which was to obtain an imagable lesion with well-defined blood-brain-barrier breakdown and necrotic zones. The desired lesion size was between 1.5 to 2.5 cm diameter radially, in the coronal plane with the greatest diameter.

Animals↗
PubMed1994

Thermometry of interstitial hyperthermia given as an adjuvant to brachytherapy for the treatment of carcinoma of the prostate.

PURPOSE: Recurrence in the prostatic gland remains a significant problem in the management of locally advanced prostatic cancer. Transperineal thermobrachytherapy has been utilized in an attempt to improve local tumor control. The purpose of this study was to quantitate the temperature distributions obtained in carcinoma of the prostate treated with interstitial radiofrequency-induced hyperthermia given in conjunction with 192Ir brachytherapy in a Phase I study. METHODS AND MATERIALS: From 1987 until 1992, 36 patients (5 with locally recurrent, 15 with Stage B, and 16 Stage C prostate cancers) were treated with interstitial brachytherapy implants supplemented with radiofrequency-induced hyperthermia. An array of 7-32 stainless steel trocar electrodes (outer diameter = 1.5 mm, interelectrode spacing = 8 mm) were implanted into the prostate gland through a perineal approach utilizing a specially designed template. Each trocar was electrically insulated along the length which traversed surrounding normal tissues. One to three additional plastic catheters were implanted for automated temperature mapping. Thirty-four of these procedures were performed following lymph node sampling. However, the last two removable interstitial hyperthermic prostate implants were done by the transperineal route under ultrasound guidance. A hyperthermia treatment (goal of 43 degrees C for 45 minutes) was given immediately prior to the insertion and immediately following the removal of the 192Ir. A computer-controlled radiofrequency-based generator (freq. 0.5 MHz) implementing electrode multiplexing was used to induce and maintain elevated temperatures. RESULTS: Transient local pain was the most common treatment limiting factor. The average values of the measured minimum, mean, and maximum temperatures were 38.9 degrees C, 41.9 degrees C, and 45.7 degrees C in tumor, and 37.7 degrees C, 39.8 degrees C, and 42.9 degrees C in surrounding normal tissue, respectively. The percentages of mapped temperatures exceeding 41 degrees C, 42 degrees C, and 43 degrees C were 67%, 46%, and 27% in tumor, and 26%, 11%, and 4% in normal surrounding tissue, respectively. CONCLUSION: From this study we conclude that heterogeneous temperature distributions were induced in the prostate; significant normal tissue protection was realized in part through the selective insulation of sections of each electrode; and interstitial radiofrequency-induced hyperthermia of the prostate is feasible and well tolerated, with further technical developments warranted.

Adenocarcinoma↗
PubMedDate not supplied

Impact of operator technique and device on infrared emission detection tympanic thermometry.

Preliminary data on the use of infrared emission detection (IRED) tympanic thermometers suggest that operator technique may be important in IRED readings. No systematic investigation of specific technique and available IRED devices has previously been performed. In a prospective, blinded trial, 40 healthy adult subjects using six IRED thermometers with two techniques were examined in random sequence. Differences between IRED tympanic, oral, and rectal temperatures were compared using ANOVA. Significant differences were observed between all temperatures, the IRED devices, and the method of probe insertion. Differences between oral or rectal temperatures and IRED tympanic readings were reduced by an ear tug (as for routine otoscopy) for all but one device. An "ear tug" results in increased IRED readings that may improve accuracy of tympanic thermometers using IRED.

Adult↗