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At least 595 records · Page 33Linked to original sources
PubMed2000

A comparative study on accuracy of liquid crystal forehead, digital electronic axillary, infrared tympanic with glass-mercury rectal thermometer in infants and young children.

This study was carried out to assess the accuracy of three devices namely, liquid crystal forehead, digital electronic axillary and infrared tympanic thermometer, using a glass-mercury rectal thermometer as the control. The subjects were two hundred children aged 0-48 months. The mean rectal temperature was 38.0 +/- 0.91 degrees C; forehead, 37.83 +/- 0.94 degrees C; tympanic, 37.77 +/- 0.95 degrees C, and axillary, 37.71 +/- 0.86 degrees C. Compared to the rectal temperature, all values were significantly lower (p < 0.05). Forehead, tympanic and axillary temperature differed from rectal temperature by at least 0.5 degrees C in 33.33 per cent, 23.5 per cent and 31.5 per cent of subjects, and at least 1 degrees C in 22 per cent, 1 per cent and 6 per cent of subjects respectively. Accuracy in detection of fever was 79 per cent for forehead, 85.5 per cent for tympanic and 84 per cent for axillary thermometry. Sensitivity of the three devices was 67-83 per cent in detection of fever and 64-77 per cent in detection of high fever. Tympanic thermometry had the best performance while forehead thermometry had the poorest. After using revised diagnostic threshold temperature by ROC curves, sensitivity of each device improved but accuracy was nearly the same. It is concluded that the three devices are not suitable as a substitute for a glass-mercury rectal thermometer in assessment of fever in infants and young children.

Child, Preschool↗
PubMed2001

[Validity of the tympanic infrared thermometer in geriatric inpatients].

The purpose of this study was to assess the agreement between rectal temperature and infrared emission detection (IRED). The specificity and sensitivity, the positive predictive value and the negative predictive value were calculated. It was a prospective, observational and unblinded study. Thermoscan-pro-1 was used to collect pairs of data in 41 patients, all hospitalised on an acute geriatric ward during a 4-month period. 41% of the patients were febrile. The 'bias' between rectal and tympanic measurement (left ear) was -0.64 degree C (d) and the standard deviation 0.58 degree C (s). The '95% Confidence Interval' for the bias was -0.82 degree C and -0.46 degree C. The '95% limits of agreement' between the rectal measurement and the tympanic measurement (left ear) was -1.78 degrees C and 0.50 degree C. Regression analysis taught us that bias was increasing with increasing temperature. If we take into account one measurement with the IRED ear thermometry, the sensitivity was 41%, the specificity 83%. The positive predictive value was 64% en the negative predictive value 67%. We can conclude that the IRED ear thermometry is not a valuable alternative for the rectal, digital thermometry in the elderly, frail and febrile hospital inpatients.

Aged↗
PubMed2002

Acceptable agreement between tympanic and rectal temperature in acute stroke patients.

Major concerns remain about the reliability of tympanic thermometers. The aim of this study was to investigate the agreement between rectal and tympanic thermometry and compare this with the repeatability of each method in patients with acute stroke. Tympanic temperature readings were from 0.7 degrees C below to 0.8 degrees C above rectal readings. As to repeatability, we found second rectal readings to be between 0.3 degrees C below and 0.4 degrees C above first readings, and second tympanic readings to be between 0.4 degrees C below and 0.5 degrees C above first readings. The agreement between the two methods is acceptable in clinical practice. Tympanic thermometry is useful in serial measurements, whereas, for a single accurate measurement, rectal mercury thermometry remains the method of choice.

Acute Disease↗
PubMed2005

[Thermal dosimetric study on hyperthermia combined with radiotherapy for deep seated pelvic malignancies].

OBJECTIVE: To ascertain a clinically meaningful thermal dose unit-temperature equivalent minute (TEM) 42.5 degrees C and the relationship between TEM 42.5 degrees C and tumor response rate. METHODS: From August 1998 to December 2002, 49 patients with recurrent or metastatic malignancies in the pelvis were treated with hyperthermia combined with conventional radiotherapy. Direct thermometry with high resistance lead needle was used whenever possible to measure the temperature by inserting Teflon catheter into the tumor. TEM 42.5 degrees C was used as the thermal dose unit and the relationship between TEM 42.5 degrees C and tumor response rate was monitored. RESULTS: There was a positive correlation between response rate TEM 42.5 degrees C and the radiation dose. The tumor volume and number of heat treatment showed no influence on response. CONCLUSION: Both univariate analysis and multivariate logistic regression analysis indicate that there is a positive correlation between the response rate, TEM 42.5 degrees C and the radiation dose. TEM 42.5 degrees C may act as a useful thermal dose unit in the combination of hyperthermia and radiotherapy. To lower the incidence of complications in thermometry, direct thermometry with high resistance lead needle can be used to measure the temperature by inserting Teflon catheter into the deep-seated malignancies.

Adenocarcinoma↗
PubMed1998

Concepts of fever.

If asked to define fever, most physicians would offer a thermal definition, such as "fever is a temperature greater than...." In offering their definition, many would ignore the importance of the anatomic site at which temperature measurements are taken, as well as the diurnal oscillations that characterize body temperature. If queried about the history of clinical thermometry, few physicians could identify the source or explain the pertinacity of the belief that 98.6 degrees F (37.0 degrees C) has special meaning vis-à-vis normal body temperature. Fewer still could cite the origin of the thermometer or trace the evolution of modern concepts of clinical thermometry. Although many would have some knowledge of the fundamentals of thermoregulation and the role played by exogenous and endogenous pyrogens in the induction of fever, few would have more than a superficial knowledge of the broad biological activities of pyrogenic cytokines or know of the existence of an equally complex and important system of endogenous cryogens. A distinct minority would appreciate the obvious paradoxes inherent in an enlarging body of data concerned with the question of fever's adaptive value. The present review considers many of these issues in the light of current data.

Cytokines↗
PubMed1998

Magnetic resonance imaging: controlled interstitial laser therapy in children with vascular malformations.

BACKGROUND AND OBJECTIVE: Interstitial laser therapy (ILT) is a minimally invasive treatment method for congenital vascular malformations (CVM). This study was intended to show whether or not open magnetic resonance imaging (MRI) offers a means of on-line thermometry and procedure control. STUDY DESIGN/PATIENTS AND METHODS: ILT using a bare fiber and an Nd:YAG laser was applied in 20 children with CVM under open MR control. RESULTS: With the open MR systems, needle placement and advancement was excellent in all cases. On-line thermometry was possible in 90% of the therapy spots. The 6 week MR follow-up revealed a 76% reduction in tumor size in 14 patients. Clinical symptoms improved in 85% of the patients. CONCLUSION: MR-guided ILT could become a safe method to treat selected types or selected regions of CVM.

Adolescent↗
PubMed1999

Fast lipid-suppressed MR temperature mapping with echo-shifted gradient-echo imaging and spectral-spatial excitation.

The water proton resonance frequency (PRF) is temperature dependent and can thus be used for magnetic resonance (MR) thermometry. Since lipid proton resonance frequencies do not depend on temperature, fat suppression is essential for PRF-based temperature mapping. The efficacy of echo-shifted (TE > TR) gradient-echo imaging with spectral-spatial excitation is demonstrated, resulting in accurate and rapid, lipid-suppressed, MR thermometry. The method was validated on phantoms, fatty duck liver, and rat thigh, demonstrating improvements in both the speed and precision of temperature mapping. Heating of a rat thigh with focused ultrasound was monitored in vivo with an accuracy of 0.37 degree C and a time resolution of 438 msec.

Animals↗
PubMed2002

Quantification and evaluation of Joule heating in on-chip capillary electrophoresis.

We present the use of a novel, picoliter volume interferometer to measure, for the first time, the extent of Joule heating in chip-scale capillary electrophoresis (CE). The simple optical configuration for the on-chip interferometric backscatter detector (OCIBD) consists of an unfocused laser, an unaltered silica chip with a half-cylinder channel and a photodetector. Using OCIBD for millidegree-level noninvasive thermometry, temperature changes associated with Joule heating (2.81 degrees C above ambient) in on-chip CE have been observed in 90 microm wide and 40 microm deep separation channels. The temporal response of Joule heating in isotropically etched channels was exponential, with it taking an excess of 2.7 s to reach equilibrium. Buffer viscosity changes have also been derived from empirical on-chip thermometry data, allowing for the determination of diffusion coefficients for solutes when separated in heated buffers. In addition, OCIBD has allowed the reduction in separation efficiency to be estimated in the absence of laminar flow and due to increased molecular diffusion and lower buffer viscosity. A 7% reduction in separation efficiency was determined for a high current drawing buffer such as Tris-boric acid under an applied field of just 400 V/cm. Results indicate that heating effects in on-chip CE have been underestimated and there is a need to readdress the theoretical model.

Buffers↗
PubMed2006

Investigation of proton density for measuring tissue temperature.

PURPOSE: To examine the temperature dependence of the proton density (PD) in both adipose and muscle tissues, and the application of the PD as a thermometry parameter in breast tissues. MATERIALS AND METHODS: Porcine fat samples and bovine muscle samples were successively heated to temperatures ranging from 30 degrees C to 76 degrees C and then cooled. They were then imaged with a dual-echo spin-echo sequence. T1 and T2 effects were carefully corrected from the images. The apparent PD (APD) in regions of interest (ROIs) and the sum of the APD in all pixels (Sum_APD) were measured and analyzed by linear regression. RESULTS: APD in adipose tissue is linear and reversible, and changes with a 0.3%/ degrees C to 0.45%/ degrees C temperature variation. The temperature coefficient of Sum_APD in adipose tissue is approximately 0.29%/ degrees C, as predicted from the Boltzmann distribution. However, the results in muscle tissue are more variable. There is an offset in both APD and Sum_APD between heating and cooling phases, as well as different temperature coefficients between these two phases. CONCLUSION: The Sum_APD in adipose tissue validates the 1/T dependence on temperature. The APD is a potentially useful parameter for fat thermometry; however, its application in muscle tissue requires further investigation.

Adipose Tissue↗
PubMed2005

Intraluminal high intensity ultrasound treatment in the esophagus under fast MR temperature mapping: in vivo studies.

New curative and palliative treatments are needed to respond to the poor prognosis of esophageal cancer. The purpose of this study was to determine whether magnetic resonance imaging (MRI) and MR thermometry can be used to monitor the thermal ablation induced by an intraluminal high-intensity ultrasound applicator positioned in the esophagus. Experiments were performed in vivo in 2 pig esophagi (25 thermal lesions per pig). Respiratory gated or cardiac gated MR thermometry was performed with segmented echo-planar imaging gradient echo sequences. All MR acquisitions were performed without susceptibility artifacts or radiofrequency interference with the ultrasound device. The experimental procedure proposed for accurate measurement of temperature in the esophagus was found to achieve an SD of +/- 1.5 degrees C for respiratory gating and +/- 3.1 degrees C for cardiac gating. Gd-enhanced T(1)-weighted images were used to depict coagulation necrosis. Autopsy was performed immediately after the treatment. Ultrasound effects were inspected visually, and the dimensions of the lesions in the liver neighboring the esophagus were compared with those determined on the MRI images. The visually assessed thermal lesions showed good correlation with the MRI data (10% mean volume difference). The feasibility of esophageal thermal ablation using intraluminal high-intensity ultrasound and of on-line MR temperature monitoring was demonstrated.

Animals↗
PubMed2006

Non-invasive temperature imaging with thulium 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetramethyl-1,4,7,10-tetraacetic acid (TmDOTMA-).

Non-invasive thermometry using hyperfine-shifted MR signals from paramagnetic lanthanide complexes has attracted attention recently because the chemical shifts of these complexes are many times more sensitive to temperature than the water 1H signal. Among all the lanthanide complexes examined thus far, thulium tetramethyl-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetate (TmDOTMA-) appears to be the most suitable for MR thermometry. In this paper, the feasibility of imaging the methyl 1H signal from TmDOTMA- using a frequency-selective radiofrequency excitation pulse and chemical shift-selective (CHESS) water suppression is demonstrated. A temperature imaging method using a phase-sensitive spin-echo imaging sequence was validated in phantom experiments. A comparison of regional temperature changes measured with fiber-optic probes and the temperatures calculated from the phase shift near each probe showed that the accuracy of imaging the temperature with TmDOTMA- is at least 0.1-0.2 degrees C. The feasibility of imaging temperature changes in an intact rat at 0.5-0.6 mmol/kg dose in only a few minutes is demonstrated. Similar to commonly used MRI contrast agents, the lanthanide complex does not cross the blood-brain barrier. TmDOTMA- may prove useful for temperature imaging in many biomedical applications but further studies relating to acceptable dose and signal-to-noise ratio are necessary before clinical applications.

Animals↗
PubMed1985

Hyperthermia for cancer: a practical perspective.

A causal relationship between hyperpyrexia and tumor regression was first suggested in 1866, when Busch reported the cure of a histologically diagnosed sarcoma in a middle-aged woman, following a bout of erysipelas. Over the years, interest in the effect of heat on cancer has remained alive, but this interest has increased dramatically in recent years. The literature on this subject is broadly reviewed and the clinical results discussed. It is apparent from clinical studies thus far that it is a relatively simple undertaking to treat superficial neoplasms with hyperthermia. However, the major challenges in clinical thermotherapy pertain to patients with deeply situated tumors. The lack of safe and reliable methods of monitoring temperature in deep tissues is a major impediment to a thorough understanding of thermal dosimetry in clinical hyperthermia, and routine thermal dosimetry in clinical hyperthermia will have to await the development of reliable noninvasive thermometry. As responses have been reported with modest levels of hyperthermia, the need for thermometry is somewhat lessened, given that invasive monitoring is imperfect and somewhat risky when used in deeply seated tumours. The eventual place of thermotherapy in the treatment of malignant tumours in man is as yet unclear and must be rigourously and thoroughly assessed in well-designed, prospective, randomized patient trials.

Animals↗
PubMed1998

NMR temperature measurements using a paramagnetic lanthanide complex.

NMR thermometry has previously suffered from poor thermal resolution owing to the relatively weak dependence of chemical shift on temperature in diamagnetic molecules. In contrast, the shifts of nuclear spins near a paramagnetic center exhibit strong temperature dependencies. The chemical shifts of the thulium 1,4,7, 10-tetraazacyclododecane-1,4,7,10-tetrakis(methylene phosphonate) complex (TmDOTP5-) have been studied as a function of temperature, pH, and Ca2+ concentration over ranges which may be encountered in vivo. The results demonstrate that the 1H and 31P shifts in TmDOTP5- are highly sensitive to temperature and may be used for NMR thermometry with excellent accuracy and resolution. A new technique is also described which permits simultaneous measurements of temperature and pH changes from the shifts of multiple TmDOTP5- spectral lines.

Calcium↗
PubMed1987

Patient monitoring during and after open heart surgery by an improved deep body thermometer.

The deep body thermometer developed by Fox was improved by Togawa by thermal insulation of the probe. The present status of medical progress in clinical thermometry through the improved deep body thermometer was reviewed from the view point of cardiac surgery. The forehead and sole temperatures obtained by this improved thermometer were monitored and recorded by a multipotentiometric recorder continuously up to 12 days in the patients admitted to the ICU who underwent open heart surgery. The forehead tissue temperature measured by this thermometer is slightly lower than and parallel to the rectal temperature, being close to the pulmonary arterial blood temperature. On the other hand, the sole tissue temperature fluctuates from room temperature to the forehead tissue temperature, sometimes showing rhythmic changes. The former seems to be the core temperature and the latter, the shell temperature. The dissociation when the two temperatures are more than 7 degrees C apart from each other suggests that the hemodynamical condition is worse than in the convergence when they remain within 2 degrees C. A state of shock can be diagnosed when the arterial systolic pressure is less than 90 mmHg and the urine output less than 1 ml/min/mg in addition to the dissociation. The effect of treatment and the prognosis for the patient are predictable according to the trends of the two temperatures as divergent or convergent. The dynamic thermometry by this thermometer is very informative and the procedure is noninvasive without discomfort to the patient.

Adult↗
PubMed1996

Residual analysis in the determination of factors affecting the estimates of body heat storage in clothed subjects.

Body heat storage can be estimated by calorimetry (from heat gains and losses) or by thermometry [from changes (delta) in mean body temperature (T b) calculated as a weighted combination of rectal (Tre) and mean skin temperatures (T sk)]. If an invariant weighting factor of Tre and T sk were to be used (for instance, delta T b = 0.8.delta Tre + 0.2 delta T sk under hot conditions), body heat storage could be over- or underestimated substantially relative to calorimetry, depending on whether the subject was wearing light or protective clothing. This study investigated whether discrepancies between calorimetry and thermometry arise from methodological errors in the calorimetric estimate of heat storage, from inappropriate weightings in the thermometric estimate, or from both. Residuals of calorimetry versus thermometric estimates were plotted against individual variables in the standard heat balance equation, applying various weighting factors to Tre and T sk. Whether light or protective clothing was worn, the calorimetric approach generally gave appropriate estimates of heat exchange components and thus heat storage. One exception was in estimating latent heat loss from sweat evaporation. If sweat evaporation exceeded 650 g.h-1 when wearing normal clothing, evaporative heat loss was overestimated and thus body heat storage was underestimated. Nevertheless, if data beyond this ceiling were excluded from the analyses, the standard 4:1 weighting matched calorimetric heat storage estimates quite well. When wearing protective clothing, the same 4:1 weighting approximated calorimetric heat storage with errors of less than approximately 10%, but only if environmental conditions allowed a subject to exercise for more than 90 min. The best thermometric estimates of heat storage were provided by using two sets of relative weightings, based upon the individual's metabolic heat production (M in kilojoules per meter squared per hour): (4 - [(M - x).x-1].2): 1 for an initial, thermoneutral environment and (4 + [(M - x).x-1].5):1 for a final, hot environment, the optimal value of x lay between 450 and 500 kJ.m-2.h-1. We concluded that the accuracy of thermometric estimates of heat storage can be improved by modifying weighting factors of Tre and T sk according to the environment, type of clothing, and metabolic rate.

Adult↗
PubMed2006

Quantitative magnetic resonance temperature mapping for real-time monitoring of radiofrequency ablation of the liver: an ex vivo study.

We evaluated the feasibility and accuracy of real-time magnetic resonance (MR) thermometry for monitoring radiofrequency (RF) ablation in the liver. Continuous MR temperature mapping was used to monitor bipolar RF ablations performed in ex vivo livers with and without flow using two parallel electrodes. Macroscopic inspection of ablation zones was compared with thermal dose maps (TDm) and T1-weighted inversion recovery turbo spin echo (IR-TSE) images for their size and shape and the influence of flow. Pearson's correlation (r), Bland and Altman tests and kappa (chiK) tests were performed. The mean differences in ablation zone size between macroscopic and TDm and IR-TSE measurements were +4 mm and -2 mm, respectively. TDm was well correlated with macroscopy (r=0.77 versus r=0.44 for IR-TSE). TDm was found to be more precise for shape recognition (chiK=0.73 versus chiK=0.55 for IR-TSE) and for detection of an intact ring of liver due to the cooling effect of flow which was impossible with IR-TSE. Simultaneous monitoring of RF ablation by MR thermometry is feasible and reliable for predicting the shape of ablation zones and the impact of the heat-sink effect of flow. Further studies are needed to confirm these results in vivo.

Animals↗
PubMed2002

Thermoradiotherapy for local control of chest wall invasion in patients with advanced non-small cell lung cancer.

BACKGROUND: We tested the feasibility of hyperthermia combined with concurrent radiotherapy (thermoradiotherapy) for pain relief and local control of non-small cell lung cancer (NSCLC) invading to the chest wall. METHODS: Thirteen patients with advanced NSCLC (eight stage IIIB and five stage IV) and severe pain caused by chest wall invasion of tumor were treated with thermoradiotherapy. During the conventional fractionated radiotherapy period, 8-MHz radiofrequency capacitive hyperthermia was administered once or twice per week for a total of three to nine treatment sessions. Pain relief, objective tumor response, thermometry, and toxicity were evaluated. RESULTS: Twelve of the 13 patients (92%) experienced satisfactory pain relief, and objective tumor shrinkage was observed in 11 of the 13 patients (85%), including complete regression in two. The thermometry parameters of minimum and maximum intratumor temperatures, mean of all intratumor temperatures, and rate of the time during which intratumor temperature was 41 degrees C or higher were 37.6 +/- 0.8 degrees C, 42.4 +/- 0.7 degrees C, 40.3 +/- 0.3 degrees C, and 80.1 +/- 8.6%, respectively. Adverse reactions included local transient skin pain in three patients, but no major toxicity was observed. CONCLUSION: Concurrent thermoradiotherapy for chest wall invasion by advanced NSCLC was feasible, with tolerable toxicity, and it may be effective for pain relief and local tumor control. Further studies comparing thermoradiotherapy and radiotherapy alone for such patient populations are warranted.

Aged↗
PubMed2006

Monitoring and correcting spatio-temporal variations of the MR scanner's static magnetic field.

The homogeneity and stability of the static magnetic field are of paramount importance to the accuracy of MR procedures that are sensitive to phase errors and magnetic field inhomogeneity. It is shown that intense gradient utilization in clinical horizontal-bore superconducting MR scanners of three different vendors results in main magnetic fields that vary on a long time scale both spatially and temporally by amounts of order 0.8-2.5 ppm. The observed spatial changes have linear and quadratic variations that are strongest along the z direction. It is shown that the effect of such variations is of sufficient magnitude to completely obfuscate thermal phase shifts measured by proton-resonance frequency-shift MR thermometry and certainly affect accuracy. In addition, field variations cause signal loss and line-broadening in MR spectroscopy, as exemplified by a fourfold line-broadening of metabolites over the course of a 45 min human brain study. The field variations are consistent with resistive heating of the magnet structures. It is concluded that correction strategies are required to compensate for these spatial and temporal field drifts for phase-sensitive MR protocols. It is demonstrated that serial field mapping and phased difference imaging correction protocols can substantially compensate for the drift effects observed in the MR thermometry and spectroscopy experiments.

Brain↗