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PubMed1989

Design for an ultrasound-based instrument for measurement of tissue blood flow.

Quantitative measurement of tissue blood flow is of importance for many reasons: detection of capillary flow disturbances, evaluating indications for amputation, investigating vasospastic conditions, and evaluating vasoactive drugs or the effect of sympathectomy. Methods of investigating tissue blood flows include skin thermometry, thermal conductance or clearance, transcutaneous PO2, laser doppler flux, and photoplethysmographic techniques. A major reason that ultrasound has not previously been applied to this problem is that at the very low blood velocities in the capillaries (0.1 to 1 mm/sec) the Doppler shift is small (on the order of 1 Hz/MHz of carrier signal). Advantages of ultrasound are a noninvasive procedure and penetration depths greater than that possible with optical techniques. This paper discusses the development of a Doppler ultrasound instrument which allows spectral resolution of the velocities in tissue blood flow. Briefly, a low phase noise oscillator at 7.5 Mhz is used with two transducers to obtain the shifted signal. After mixing with the fundamental, the resulting low frequency signal is fed into a high resolution spectrum analyzer for analysis.

Biomedical Engineering↗
PubMed1994

Non-invasive physiology: 19F NMR of perfluorocarbons.

Ever since it was shown that the 19F NMR spin-lattice relaxation rates (R1) of perfluorocarbon (PFC) emulsions are highly sensitive to oxygen tension (pO2), there has been a developing interest in the use of PFCs to probe tissue physiology. Oxygen is required for efficient function by most tissues and hypoxia leads to rapid cellular dysfunction and damage. In addition, hypoxic tumor cells are refractory to radiotherapy. Thus, the opportunity to measure tissue oxygen tension non-invasively may be significant in understanding mechanisms of tissue function and in clinical prognosis. PFC NMR parameters are also sensitive to temperature, facilitating NMR thermometry with potential applications in hyperthermia studies. I will review the development of experimental techniques, applications to specific tissues and discuss the challenges and opportunities presented by 19F NMR of perfluorocarbons.

Fluorine↗
PubMed1997

Supplementation of nicotinic acid for lactating Holstein cows under heat stress conditions.

Twenty-six lactating Holstein cows (90 d of lactation) were blocked according to milk production, parity, and days of lactation for assignment to one of two dietary treatments. Diets included a control diet with no supplemental niacin and a diet supplemented with increasing concentrations of niacin (12, 24, or 36 g/d per cow over three consecutive 17-d periods. Cows were housed in a covered free-stall barn and were fed and milked twice daily. Mean maximum air temperatures and temperature-humidity indexes were 28.5, 31.4, and 25.2 degrees C and 79.6, 85.1, and 75, respectively, for the three periods. Rectal temperature was measured with a rectal probe, tail and rump temperatures by infrared thermometry, and respiratory rate by visual observation. Measurements were made daily at 0800, 1600, and 2200 h. Rectal temperature was not affected by treatment. Comparison of skin temperatures for control cows and cows fed niacin showed higher temperatures at the tail (34.0 vs. 33.7 degrees C at 0800 h; 35.1 vs. 34.8 degrees C at 1600 h, respectively) and rump (34.1 vs. 33.7 degrees C at 0800 h; 35.3 vs. 35.0 degrees C at 1600 h, respectively) for control cows during period 1. No differences in thermal responses were observed during period 3. Niacin did not significantly increase milk production but decreased skin temperatures during periods of mild or severe heat stress.

Animals↗
PubMed1986

Interstitial hyperthermia and iridium brachytherapy in treatment of malignant glioma. A phase I clinical trial.

An oncolytic effect of hyperthermia in the 42 degrees to 43 degrees C range has been previously demonstrated in cell culture and animal models. To apply this modality clinically, an interstitial microwave antenna array system has been developed for the delivery of controlled hyperthermia to an intracranial tumor volume, and a Phase I clinical trial involving six patients with malignant gliomas was undertaken. The protocol to study technical feasibility and patient tolerance combined interstitial iridium-192 irradiation and interstitial hyperthermia with 60-minute hyperthermia sessions immediately before and after brachytherapy. After-loading catheters suitable for both treatment modalities were implanted using a computerized tomography-assisted technique. Thermometry data confirmed the ability of a microwave antenna system to achieve reliable temperature distributions, and reasonable patient tolerance was documented.

Adult↗
PubMed1988

Quantification of thermal asymmetry. Part 2: Application in low-back pain and sciatica.

Temperature differences between the lower extremities were measured using a computerized thermometric scanning system in order to compare the degree of thermal asymmetry in 144 patients with low-back pain. The patients displayed highly significant thermal asymmetries, with the involved limb being cooler (p less than 0.001). When asymmetries exceeded 1 standard deviation from the mean temperature of homologous regions measured in 90 normal control subjects, the positive predictive value of thermometry in detecting root impingement was 94.7% and the specificity was 87.5%. These values indicate that calculation of temperature asymmetry is particularly effective in evaluating reported pain in psychosocially affected patient populations in whom the chance of positive myelography or impaired root function is low. In this group of patients, thermometric study provides physicians with important information for proper decision making. The test can be performed to avoid more invasive and probably less revealing diagnostic or exploratory surgical procedures.

Adult↗
PubMed1989

Cerebral blood flow and the thermal properties of the brain: a preliminary analysis.

Safe and effective use of hyperthermia for the treatment of brain tumors requires precise control of the distribution of temperatures (that is, the thermal field) within the tumor and within the adjacent brain. Major influences upon the distribution of temperatures include the passive thermal properties of the brain, such as its specific heat (Cb), and the contribution of cerebral blood flow (CBF). Recently, an electrical-mechanical analog model of heat flow within the brain has been developed from which an expression for CBF has been derived: CBF = Cb/(tau rho c) where tau is the thermal decay constant, rho is the density of blood, and c is its specific heat. To test this model a series of experiments was carried out in adult dogs in which stereotaxically implanted microwave antennas operating at 2450 MHz, fluoro-optical thermometry probes, and platinum electrodes were used to simultaneously measure CBF by thermal washout and hydrogen clearance techniques. The correlation coefficient for estimates of CBF derived by the two methods in 52 paired observations was 0.89. Measurements of CBF were more reliable at increased distances from the microwave antenna, since CBF is sensitive to the degree of temperature elevation (delta T). The ratio of post-heating CBF to pre-heating CBF varies linearly with delta T and has a correlation coefficient of 0.86. When values of CBF determined by the hydrogen clearance method were employed in the above equation, it was possible to derive Cb as 0.70 +/- 0.08 cal/gm-degrees C. Use of this value for Cb in this equation produces estimates of CBF by thermal clearance that are within 10% of the values for CBF as measured by the hydrogen clearance method. It is concluded that this model of thermal flow within the brain may have heuristic value for treatment planning and that microwave antennas and fluoro-optical probes may represent a new methodology for the clinical estimation of CBF. These methods have recently been employed in patients undergoing combined hyperthermia and chemotherapy.

Animals↗
PubMed1993

[Relationship between external auditory canal temperature and caloric nystagmus--the problem with the ordinary cold-warm caloric test].

The cold-warm caloric test is performed with water irrigation, using a hot temperature of 44 degrees C and a cold temperature of 30 degrees C, which are thermally equidistant from the body temperature 37 degrees C. However, the 30 degrees C irrigation nearly always produces a stronger nystagmic response than that of the 44 degrees C stimulation. The purpose of this study is to investigate the difference in nystagmic response between cold and hot stimulation. The achieved hot (44 degrees C) and cold (30 degrees C) water samples were prepared, and irrigation was with a disposable plastic syringe. Temperature changes in the external auditory canal were monitored by tympanic thermometry during the cold-warm caloric test. Maximal slow phase velocity and the duration of induced nystagmus were recorded on an electro-nystagmograph. The following conclusions were drawn; 1) The average normal external auditory canal temperature was 36.8 degrees C, and there was no side difference between the right and left ears. External canal temperature was higher than that of the axilla. 2) When 20 ml of 30 degrees C water was instilled the temperature change in the external canal was larger than that in response to the 44 degrees C water and the maximal slow phase velocity of nystagmus for cold stimulation was stronger than that for hot. However, the duration of nystagmus for the cold was not significantly longer than that of the hot stimulation.

Adult↗
PubMedDate not supplied

Effect of a nitroglycerin patch on perfusion to the foot in healthy subjects.

Nitric oxide is an endogenous gas released by endothelial cells that induces vasodilatation and plays other important roles in the wound-healing process. Nitroglycerin preparations are liberators of nitric oxide. Podiatric physicians have used nitroglycerin paste and patches on patients in an attempt to increase perfusion to the foot. However, the drug's efficacy seems to be largely anecdotal. A prospective, randomized, placebo-controlled, double-blind study was conducted to investigate the efficacy of a nitroglycerin patch in locally increasing perfusion to the foot. Twenty-two healthy subjects were randomly assigned to either a drug group (nitroglycerin patch, 0.2 mg/h) or a placebo group (adhesive patch without active ingredient). The patch was applied to the plantar arch of the foot. Objective and subjective measures were then used to detect changes in perfusion to the foot after a 2-hour experimental period. The objective measures, cutaneous thermometry and photoplethysmography, found no significant measurable difference in perfusion to the foot between the drug and placebo groups (P > .05). A subjective questionnaire used to assess changes in temperature or sensation detected by the subject yielded similar results. Thus a nitroglycerin patch dose of 0.2 mg/h showed no measurable ability to increase perfusion to the foot. Further research is needed to validate the indications for this therapy.

Administration, Cutaneous↗
PubMed1995

Contralateral limb during total contact casting. A dynamic pressure and thermometric analysis.

The authors draw attention to the importance of evaluation of the contralateral limb when treating unilateral sequelae secondary to distal symmetrical polyneuropathy. Plantar pressure measurements of the contralateral limb during total contact casting are reviewed. The results of thermometric evaluation before and after initiation of repetitive stress were reviewed. The results suggest that the patient walking in a total contact cast may experience a reduced focal pressure on the contralateral limb when compared with uncasted walking and three-point walking with crutches. Dermal thermometry may be a highly sensitive tool in evaluating even mild increases in repetitive stress. To explain this decrease in contralateral stress, the authors examine the features inherent to the total contact cast and propose the concept of proprioceptive stability.

Casts, Surgical↗
PubMed2005

A magnetic resonance imaging-compatible, large-scale array for trans-skull ultrasound surgery and therapy.

OBJECTIVE: Advances in ultrasound transducer array and amplifier technologies have prompted many intriguing scientific proposals for ultrasound therapy. These include both mildly invasive and noninvasive techniques to be used in ultrasound brain surgery through the skull. In previous work, it was shown how a 500-element hemisphere-shaped transducer could correct the wave distortion caused by the skull with a transducer that operates at a frequency near 0.8 MHz. Because the objective for trans-skull focusing is its ultimate use in a clinical context, a new hemispheric phased-array system has now been developed with acoustic parameters that are optimized to match the values determined in preliminary studies. METHODS: The transducer was tested by focusing ultrasound through ex vivo human skulls and into a brain phantom by means of a phase-adaptive focusing technique. Simultaneously, the procedure was monitored by the use of magnetic resonance guidance and thermometry. RESULTS: The ultrasound focus of a 500-element 30-cm-diameter, 0.81-MHz array could be steered electronically through the skull over a volume of approximately 30 x 30 x 26 mm. Furthermore, temperature monitoring of the inner and outer surfaces of the skull showed that the array could coagulate targeted brain tissue without causing excessive skull heating. CONCLUSIONS: The successful outcome of these experiments indicates that intensities high enough to destroy brain tissue can be produced without excessive heating of the surrounding areas and without producing large magnetic resonance noise and artifacts.

Artifacts↗
PubMed1999

The diabetic neuropathic ulcer: an overview.

The leading cause of amputation in patients with diabetes is the nonhealing foot wound and its complications. The effects of peripheral neuropathy, peripheral vascular disease, and infection often combine to facilitate ulcer development that can lead to gangrene and amputation. In many instances, foot ulcers and amputation can be prevented. The literature over the past 5 years has included information on the infrared thermometry in the diagnosis of infection and acute Charcot change. Pressure downloading has been facilitated by computerized foot scanning systems and the use of prefabricated pneumatic walkers as an alternative to the contact cast. Local wound care is enforced by repeated sharp debridement. Nonhealing ulcers can benefit from biologicals: platelet-derived growth factors and a human dermal replacement containing viable fibroblasts. The most successful outcomes are achieved when interdisciplinary teams are formed to provide coordinated care. The goal of this article is to provide healthcare professionals with an overview of the risks of neuropathic foot injury and to offer strategies for prevention, protection, and reduction of recurrences of the diabetic foot ulcer.

Algorithms↗
PubMedDate not supplied

Accuracy of tympanic temperature readings in children under 6 years of age.

PURPOSE: Infrared tympanic thermometry (ITT) is increasingly used as a convenient, noninvasive assessment method for febrile children. However, the accuracy of ITT for children has been questioned, particularly in relation to specificity and sensitivity. This study was designed to (a) determine the correlation and extent of agreement between rectal temperature (RT) readings obtained by electronic thermometer and ear-based temperature readings obtained by ITT, and (b) determine the accuracy of detecting fever in children under 6 years of age. METHODS: This correlational study used a sample of 241 paired ear and rectal temperatures obtained in the emergency department (ED) of a 920-bed regional hospital. All children under the age of 6 years who routinely received a rectal temperature measurement were eligible to participate. According to the ED protocol, rectal temperatures were obtained on all patients less than 3 years or patients 3-6 years that presented with a complaint of fever. For the study, tympanic measurements were also taken. RESULTS: Correlation between rectal and tympanic temperature readings was statistically significant (r = 0.84, p < .001). The mean difference between rectal and tympanic temperatures was -0.60 degrees C. Threshold-adjusted accuracy in screening for fever was determined by sensitivity (80%), specificity (85%), positive predictive value (87%), and negative predictive value (85%). CONCLUSIONS: Sensitivity, specificity, positive predictive value, and negative predictive value are unacceptably low and the number of children with fever who would be missed by screening with a tympanic thermometer is unacceptable. Findings of this study do not support the use of tympanic thermometers to detect fever in children under 6 years of age.

Age Factors↗
PubMedDate not supplied

[Dynamic radiation telethermometry in the diagnosis of acute appendicitis].

Density was studied of heat flow from the area of the anterior abdominal wall in 167 patients with acute appendicitis. A novel methodological approach has been developed to the diagnosis of acute appendicitis making use of remote thermometry with the unit "Radiation heat flows meter". Recording of heat flows from the region of the anterior abdominal wall helps in the diagnosis of acute appendicitis, allows some preliminary judgement about the degree of affection of the organ, permits choosing relevant policy of managing a particular patient. The method can be employed in planned and urgent surgery.

Abdominal Muscles↗
PubMedDate not supplied

[Methods for vascular exploration in man: microcirculation and veins].

The pharmacodynamic evaluation of venotropic compounds deals mainly with vascular reactivity and fluid exchanges. At the microvascular level, three kinds of approaches can be used: (1) clinimetric measurements of cutaneous temperature (thermometry), skin colour (chromametry) and leg volume; (2) indirect physical parameters evaluating the haemodynamic or nutritional efficacy of the microcirculation (TcPO2 and laser doppler); (3) capillaroscopy with digital image analysis, which allows a quantification of the microvascular bed, of some kinds of transcapillary exchanges and of lymphatic microcirculation. At the venous level, they are also several usable techniques: (1) US duplex, which allows measurements of venous diameter variations; (2) plethysmography, which evaluates the compliance of the venous system from pressure/volume curves.

Capillaries↗
PubMedDate not supplied

[Neurophysiological study of thin myelinated and unmyelinated fibers].

INTRODUCTION: Standard neurophysiological techniques evaluate thick myelinated fibers. Yet, peripheral nerves are equally composed of thin myelinated and unmyelinated fibers. The latter are responsible for autonomic function as well as temperature and pain perception. DEVELOPMENT: Microneurographic studies are restricted to investigation laboratories. Since the techniques are complex and invasive, their performance is still poor for clinical purposes and some of the components to be analyzed, such as cardiovagal, cannot be directly recorded. The clinical need to evaluate the functions regulated by the autonomic nervous system (ANS) had led to devising a series of tests which, in most cases, rely on reflex responses evoked by already known standardize stimuli. The battery chosen has to be non invasive, reproducible, specific, providing relevant data to the investigated function, with a readily available technology, which has to be managed being aware of the physiological and pathological factors that might bear an influence on the results. The recent development of heart rate and blood pressure power spectral analysis, provides a new interesting insight for quantification of ANS abnormalities. The study of thermography and thermometry of body surface brings forward evidence on the activity of other thin and unmyelinated fibers components of the peripheral nerve spectrum. CONCLUSION: The adequate management of the above mentioned tests gives rise to a more extensive and appropriate knowledge of the whole peripheral nerve fiber spectrum.

Arrhythmias, Cardiac↗
PubMed2000

Temperature measurement in critically ill adults: a comparison of tympanic and oral methods.

BACKGROUND: Despite increasing use of tympanic thermometers in critically ill patients who do not have a pulmonary artery catheter in place, variations in measurements obtained with the thermometers are still a problem. OBJECTIVE: To compare the range of variability between tympanic and oral electronic thermometers. METHODS: Subjects were a convenience sample of 72 patients admitted to a 24-bed adult medical-surgical intensive care unit. For each patient, temperatures were measured concurrently (within a 1-minute period) with an oral (Sure Temp 678) thermometer, a pulmonary artery catheter (Baxter VIP Swan-Ganz Catheter), and 2 tympanic (FirstTemp Genius II and ThermoScan Ear Pro-1) thermometers. Each subject was used up to 3 times for data collection. Measurements obtained with the oral and tympanic thermometers were compared with those obtained with the pulmonary artery catheter. Nonparametric analysis of data was used. RESULTS: The magnitude of error for the ThermoScan tympanic thermometer differed significantly from that of the Genius II tympanic thermometer and the SureTemp oral thermometer (P < .001). Application of the Bland and Altman method to frame the data on the basis of an accuracy tolerance zone of +/-0.5 degrees C indicated variability with both the oral and tympanic methods. The overall degree of variability was lower for the oral thermometer. CONCLUSIONS: Oral thermometers provide less variable measurements than do tympanic thermometers. Use of oral thermometry is recommended as the best practice method for temperature evaluation in critical care patients when measurement of core temperature via a pulmonary artery catheter is not possible.

Adult↗
PubMed2000

External beam radiotherapy and hyperthermia in the treatment of patients with locally advanced prostate carcinoma.

BACKGROUND: The current study was conducted to evaluate the combination of external beam radiation therapy and hyperthermia in the treatment of patients with locally advanced prostate carcinoma. METHODS: Twenty-six patients were treated on a Phase I/II protocol between June 1990 and April 1993. The median age of the patients was 69 years. Nine patients had well differentiated adenocarcinoma, ten patients had moderately differentiated adenocarcinoma, and six patients had poorly differentiated adenocarcinoma. All patients had American Urologic Society Stage C2-D1 adenocarcinoma. The median pretreatment prostate specific antigen (PSA) level was 29 ng/mL (range, 6-104 ng/mL). All patients received external beam radiation therapy using a four-field technique. The median radiation dose was 6,800 centigrays (cGy) given in 200-cGy fractions. Hyperthermia was administered concurrently with radiation therapy to temperatures of 42.5 degrees C for 30 minutes using a transrectal ultrasound applicator with 3 thermometry probes, given as either a single treatment (9 patients) or as two treatments (17 patients). Overall survival (OS) and biochemical no evidence of disease (bNED) status were calculated using Kaplan-Meier analysis. A consensus conference definition of PSA failure was used. The Cox proportional hazards model was used for multivariate analysis. The median follow-up for all patients was 71 months. RESULTS: The median time to PSA nadir was 15 months with a median PSA nadir value of 1.0 ng/mL. The median and 5-year OS was 88 months and 73%, respectively, and the median and 5-year bNED survival was 36 months and 35%, respectively. Multivariate analysis revealed only the pretreatment PSA level (P = 0.03) and the PSA nadir reached (P < 0.01) to be significant predictors of bNED survival. The duration of hyperthermia therapy showed a trend toward significance for OS (P = 0.06). CONCLUSIONS: The current Phase I/II protocol evaluating the combination of prostate hyperthermia and external beam radiation therapy for the treatment of patients with locally advanced prostate carcinoma suggests prostate hyperthermia to be feasible with no apparent significant increased toxicity, although there was no significant improvement in treatment outcome when compared with other studies reported in the literature evaluating external beam radiation therapy with or without androgen suppression. However, further investigation into the duration as well as the temperature of the hyperthermia with a greater number of patients is warranted.

Adenocarcinoma↗
PubMed2000

[A comparative evaluation of different methods of esophagoplasty].

Intraoperative comparative oxyhemo- and thermometry of fragments of the gastrointestinal tract used for creation of the artificial esophagus were performed in 41 patients. The relationship of the degree of ischemic alterations in the transplant tissues and the development of postoperative complications was determined.

Body Temperature↗