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PubMedDate not supplied

Noninvasive thermometry with a clinical x-ray CT scanner.

A CT scanner yields CT numbers which are proportional to the fractional difference in effective local electron density of the subject material with respect to that of calibration material. A homogeneous water-equivalent material is used as a calibration phantom under isothermal conditions. Any temperature variation (spatial or temporal) in the subject material subsequently scanned, will generate a CT-number shift in the CT image because of density changes due to thermal expansion. The potential use of the thermally generated CT-number shift in noninvasive thermometry during cancer hyperthermia was studied in vitro in samples of water and muscle tissue. The reproducibility of the area-averaged CT-number measurement on our EMI-7070 scanner was found to depend strongly on the time interval between successive counterclockwise scans and on the size of the region of interest used for area averaging. A linear relationship was found between the CT number and water density in the water temperature range from 10 to 55 degrees C. In the hyperthermia temperature range (36-50 degrees C), the relationship between the CT number and temperature itself is linear, with a CT-number thermal shift of about 0.4 and 0.45 HU/degrees C for water and muscle tissue, respectively. The achievable temperature discrimination is a fraction of degree C at spatial resolutions of the order of a centimeter.

Hot Temperature↗
PubMed2003

The effect of a low-frequency sound source (acoustic thermometry of the ocean climate) on the diving behavior of juvenile northern elephant seals, Mirounga angustirostris.

Changes in the diving behavior of individual free-ranging juvenile northern elephant seals, Mirounga angustirostris, exposed to the acoustic thermometry of the ocean climate (ATOC) sound source were examined using data loggers. Data loggers were attached to the animals and measured swim speed, maximum depth of dive, dive duration, surface interval, descent and ascent rate, and descent and ascent angle along with sound pressure level (SPL). The ATOC sound source was at a depth of 939 m and transmitted at 195 dB re: 1 microPa at 1 m centered at 75 Hz with a 37.5-Hz bandwidth. Sound pressure levels (SPL) measured at the seal during transmissions averaged 128 dB and ranged from 118 to 137 dB re: 1 microPa for the 60-90 Hz band, in comparison to ambient levels of 87-107 dB within this band. In no case did an animal end its dive or show any other obvious change in behavior upon exposure to the ATOC sound. Subtle changes in diving behavior were detected, however. During exposure, deviations in descent rate were greater than 1 s.d. of the control mean in 9 of 14 seals. Dive depth increased and descent velocity increased in three animals, ascent velocity decreased in two animals, ascent rate increased in one animal and decreased in another, and dive duration decreased in only one animal. There was a highly significant positive correlation between SPL and descent rate. The biological significance of these subtle changes is likely to be minimal. This is the first study to quantify behavioral responses of an animal underwater with simultaneous measurements of SPL of anthropogenic sounds recorded at the animal.

Acoustics↗
PubMed2003

Primary electronic thermometry using the shot noise of a tunnel junction.

We present a thermometer based on the electrical noise from a tunnel junction. In this thermometer, temperature is related to the voltage across the junction by a relative noise measurement with only the use of the electron charge, Boltzmann's constant, and assumption that electrons in a metal obey Fermi-Dirac statistics. We demonstrate proof-of-concept operation of this primary thermometer over four orders of magnitude in temperature, with as high as 0.1% accuracy and 0.02% precision in the range near 1 kelvin. The self-calibrating nature of this sensor allows for a much faster and simpler measurement than traditional Johnson noise thermometry, making it potentially attractive for metrology and for general use in cryogenic systems.

Journal Article↗
PubMed2006

An evaluation of tympanic thermometry in a paediatric emergency department.

BACKGROUND AND OBJECTIVES: The consequences of missing fever in children can be grave. Body temperature is commonly recorded at the axilla but accuracy is a problem. This study aimed to evaluate the accuracy of a tympanic thermometer in the paediatric emergency setting. METHOD: In a total of 106 infants, the body temperature was measured in the daytime with an infrared tympanic thermometer, and at the axilla with an electronic thermometer and at the rectum (gold standard for measurement of body temperature). Fever was defined as a rectal temperature of 38.0 degrees C or greater, axillary temperature of 37.5 degrees C or greater, and tympanic temperature of 37.6 degrees C or greater. The temperature readings at the three sites were compared statistically. RESULTS: There was a greater correlation of the tympanic measurement with the rectal measurement than the axillary with the rectal in both febrile and afebrile infants. The mean difference between the tympanic and rectal measurements was lower than that between the axillary and rectal measurements in both groups of infants (tympanic 0.38 degrees C and 0.42 degrees C, and axillary 1.11 degrees C and 1.58 degrees C, respectively). Tympanic measurements had a sensitivity of 76% whereas axillary measurements had a sensitivity of only 24% with rectal temperatures of 38-38.9 degrees C. CONCLUSION: Tympanic thermometry is more accurate than measurement of temperature with an electronic axillary thermometer. It is also quick and safe, and thus it is recommended in the paediatric emergency setting.

Axilla↗
PubMed2000

Usefulness of MR imaging-derived thermometry and dosimetry in determining the threshold for tissue damage induced by thermal surgery in rabbits.

PURPOSE: To investigate in vivo the feasibility of using magnetic resonance (MR) imaging-derived temperature and thermal dose measurements to find the threshold of thermal tissue damage. MATERIALS AND METHODS: Sonications were delivered in rabbit thigh muscles at varying powers. Temperature-sensitive MR images obtained during the sonications were used to estimate the temperature and thermal dose. The temperature, thermal dose, and applied power were then correlated to the occurrence of tissue damage observed on postsonication images. An eight-element phased-array transducer was used to produce spatially flat temperature profiles that allowed for averaging to reduce the effects of noise and the voxel size. RESULTS: The occurrence of tissue damage correlated well with the MR imaging-derived temperature and thermal dose measurements but not with the applied power. Tissue damage occurred at all locations with temperatures greater than 50.4 degrees C and thermal doses greater than 31.2 equivalent minutes at 43.0 degrees C. No tissue damage occurred when these values were less than 47.2 degrees C and 4.3 equivalent minutes. CONCLUSION: MR imaging thermometry and dosimetry provide an index to predict the threshold for tissue damage in vivo. This index offers improved online control over minimally invasive thermal treatments and should allow for more accurate target volume coagulation.

Algorithms↗
PubMed1978

Frontal dynamic thermometry. Improvement in diagnosis of carotid stenosis.

This new method of frontal thermometry is based on a recording of the spontaneous reheating curve of the skin after cooling it to 25 degrees C. In cases of carotid stenosis, a thermal asymmetry of one of the three following kinds can be observed: thermal asymmetry from the start; asymmetry only during the reheating, or asymmetry during reheating and remaining afterwards. The reduction of the blood flow and a vaso-motor factor explain this asymmetry. This method allows better detection of clinical latent carotid stenosis.

Adult↗
PubMed2005

Temporal scanner thermometry: a new method of core temperature estimation in ICU patients.

BACKGROUND AND AIMS: Temperature measurement is a routine task of patient care, with considerable clinical impact, especially in the ICU. This study was conducted to evaluate the accuracy and variability of the Temporal Artery Thermometer (TAT) in ICU-patients. Therefore, a convenience sample of 57 adult patients, with indwelling pulmonary artery catheters (PAC) in a 40-bed intensive care unit in a university teaching hospital was used. METHODS: The study design was a prospective, descriptive comparative analysis. Body temperature was thereby measured simultaneously with the TAT and the Axillary Thermometer (AT), and was compared with the temperature recording of the PAC. The use of vasoactive medication was recorded. RESULTS AND CONCLUSIONS: Mean temperature of all measurements was: PAC: 37.1 degrees C (SD: 0.87), TAT 37.0 degrees C (SD: 0.68) and axillary thermometer: 36.6 degrees C (SD: 0.94). The measurements of the TAT and the PAC were not significantly different (man differnce: 0.14 degrees C; SD: 0.51; p = 0.33); whereas the measurements of the PAC and the AT differed significantly (mean difference: 0.46 degerees C; SD: 0.39; p < 0.001). Mean diference in PAC versus TAT analyses, between patients with vasopressor therapy (0.12 degrees C; SD: 0.55), and without vasopressor therapy (0.19 degrees C; SD: 0.48) was not statistically significant (p = 0.47). CONCLUSION: We can conclude that the temporal scanner has a relatively good reliability with an acceptable accuracy and variability in patients with normothermia. The results are comparable to those of the AT, but they do not seem to be sufficient to prove any substantial benefit compared to rectal, oral or bladder thermometry.

Adult↗
PubMed2004

Temperature measurement in critical care adults: a comparison of thermometry and measurement routes.

PURPOSE: To describe within- and between-subject mean differences between and among temperature sites (oral, axilla, PA) and instruments. METHODS: A convenience sample (N = 35) of volunteering, adult (> or = 18 years), 1st-day postcardiac surgery inpatients was obtained. Temperature-sensing instruments included Geratherm DataTherm and SolarTherm, and Abbott Opticath fiber optic PA catheters. For 21 min, simultaneous temperature readings (degrees C) at 4 temperature sites with 3 thermometry devices were monitored. RESULTS: Mean difference at 21 min PA and between DataTherm axilla and PA = 0.72 degrees C (SD 0.30); between PA and SolarTherm oral = 0.62 degrees C (SD 0.34); and between PA and SolarTherm axilla = 0.46 degrees C (SD 0.16). Temperature levels were not a factor relative to difference scores between study and reference devices. CONCLUSIONS: Both test devices, SolarTherm (an intermittent-use device) and DataTherm (a temperature-monitoring device), performed well, and correlated strongly with PA temperature assessments.

Aged↗
PubMed2005

Non-contact infrared thermometry temperature measurement for screening fever in children.

BACKGROUND: During the SARS epidemic, mass fever screening at border control points and public hospitals was done by measuring forehead temperature by non-contact infrared thermometry. However, its accuracy is not well documented. METHODS: We evaluated the agreement of non-contact infrared forehead temperature (NIFT) measurement by comparing NIFT readings with tympanic temperatures taken in children (1 mth to 18 yrs) admitted to the general paediatric wards of Kwong Wah Hospital, Hong Kong. RESULTS: A total of 567 patients were recruited and 1000 pairs of readings were obtained. The incidence of fever, defined as tympanic temperature (in rectal model) >38 degrees C (100.4 degrees F), was 12.3%. The mean difference between NIFT and tympanic temperature was 2.34 degrees C (4.21 degrees F) and the 95% limit of agreement between NIFT and tympanic temperature was 0.26-4.42 degrees C (0.47-7.96 degrees F). NIFT was significantly lower than tympanic temperature readings. The optimal cut-off point of NIFT derived from the receiver-operator characteristics curve for fever definition was 35.1 degrees C (95.2 degrees F). The sensitivity, specificity, positive predictive value and negative predictive value of this cut-off point for fever screening were 89.4%, 75.4%, 33.7% and 98.1%, respectively. CONCLUSIONS: NIFT measurement has a reasonable accuracy in detecting tympanic fever in children. However, one should be aware of the high false-positive rate of fever screening using NIFT.

Body Temperature↗
PubMed2003

Global rainbow thermometry assessed by Airy and Lorenz-Mie theories and compared with phase Doppler anemometry.

Global rainbow thermometry (GRT) measures the mean size and temperature of an ensemble of spray droplets. The domain of validity of the Airy theory for this technique is established through comparison with Lorenz-Mie theory. The temperature derivation from the inflection points of the Airy rainbow pattern appears to be independent of the type of spray dispersion. Measurements in a water spray are reported. The mean diameter obtained from the rainbow pattern lies between the arithmetic and the Sauter mean diameters measured by phase Doppler anemometry. The temperature measurement by GRT is shown to be accurate within a few degrees Celsius.

Journal Article↗
PubMed2004

Global rainbow thermometry: improvements in the data inversion algorithm and validation technique in liquid-liquid suspension.

Improvements on the validation of a nonintrusive laser-based measurement technique are presented. This new technique, called global rainbow thermometry (GRT), is capable of determining the temperature and the size distributions of liquid droplets dispersed in a liquid or gaseous bulk. We propose a new data inversion algorithm that takes into account the whole rainbow pattern. Experimental validation of the GRT technique is performed for a liquid-liquid suspension. We performed the validation by comparing the measurements obtained with the GRT technique for the mean droplet temperature and size with the results obtained with alternative techniques.

Journal Article↗
PubMed2005

Time-resolved CO2 thermometry for pressures as great as 5 MPa by use of pure rotational coherent anti-Stokes Raman scattering.

Pure rotational coherent anti-Stokes Raman scattering measurements of pure CO2 have been performed in a temperature range from 300 to 773 K and for pressure from 0.1 to 5 MPa for the purpose of time-resolved CO2 thermometry. Particular emphasis was put on the comparison of several line-width approximations to model the experimental spectra. Generally good agreement of the temperature mean values with the thermocouple reference has been found for all models over almost the whole pressure and temperature range investigated. The standard deviations, which increased with temperature, were comparable with or better than the results gained for single-shot measurements of pure N2 or O2-N2 mixtures. Yet for high particle densities close to the critical point of CO2 the limitation of the models became obvious, owing to the strongly increased influence of motional narrowing effects. The characteristics of these effects have been demonstrated by measurements even closer to the critical conditions.

Journal Article↗
PubMed2005

Assessment of refractive index gradients by standard rainbow thermometry.

Up to now the application of rainbow thermometry has been limited to particle systems possessing a uniform refractive index. This is mostly due to the absence of an appropriate data inversion algorithm that takes into account the presence of a refractive index gradient. In this paper, for the first time to our knowledge, exploiting a generalization of the Airy theory, a data inversion algorithm for a single droplet, presenting a parabolic refractive index gradient, is proposed. This data inversion algorithm is used to compute the diameter and the refractive index at the core and at the surface of a simulated burning droplet. The results are compared to the analytical solutions showing a satisfactory agreement.

Journal Article↗
PubMedDate not supplied

The use of implanted closed-tip catheters for the introduction of thermometry probes during local hyperthermia treatment series.

In the past two and a half years custom-made closed-tip catheters have been used to allow extensive temperature monitoring with multi-junction thermocouple probes during local hyperthermia. Data from animal experiments indicate that the use of thermometry probes within such a catheter provides reliable temperature measurements. In order to reduce stress to the patient the catheters were fixed so that they could stay in place during the total treatment series. The catheters, outer diameter 1.22 mm, were introduced through hollow needles under sterile conditions before the first hyperthermia session, and fixed using Histo-acryl (tissue adhesive) and Tegaderm (transparent adhesive). Recently, the data concerning the first 180 catheters placed in 74 treatment areas were evaluated. In one patient, an abscess developed 10 days after removal of the (3) catheters, which required surgical intervention, but it was not clear whether these problems had developed as a result of catheter placement. There were no problems with 139 of the remaining 177 catheters (79 per cent) and in 50 treatment fields (68 per cent), respectively, for a duration of 9-55 (mean 23) days. Ten catheters (6 per cent) were lost during the treatment series after 1-22 (mean 10) days. With 28 catheters (16 per cent) infection was observed, 14-27 (mean 19) days after insertion, which necessitated catheter removal before the last treatment session in 11 cases (6 per cent). The complication rate decreased with increasing experience; from 29 per cent (25/85) in the early period to 14 per cent (13/92) in the later period. We conclude that the use of closed-tip catheters under proper control generally causes few, if any, problems. This results in the acquisition of a substantial amount of reliable temperature data at reproducible sites, and it is well tolerated by the patient.

Adenocarcinoma↗
PubMedDate not supplied

Total implants for hyperthermia application and thermometry.

Tests have been performed in saline phantoms on a 6.78 MHz hyperthermia applicator designed for complete implantation; no conductors would penetrate the skin following the implant procedure. Energy is coupled across the skin from an external to an internal loop antenna: the latter is connected by transmission line to conventional r.f. tissue electrodes which are typically either parallel plates or arrays of cylindrical pins. In phantoms the technique produces deep, localized heating at a selected site without significant hearing at the 'subdermal' receiving antenna near the surface. In addition, the hyperthermia applicator may have potential as an indicator of temperature for the tissue volume at the deep site, since complex impedance at the external antenna is a function of tissue resistivity/temperature at the electrodes. Specifically, temperature at the deep site can be controlled effectively by regulation of the phase angle between voltage and current at the external antenna. A separate passive implantable electromagnetic-reflectance thermometer, energized by external electromagnetic fields, has been designed. This device, also tested in gel and water phantoms, is energized and interrogated by external r.f. fields and tracks a thermocouple to within +/- 0.1 degree C over the range of interest in clinical hyperthermia. The intended application for these devices is repeated, long-term hyperthermic treatment and thermometry of deep-seated malignant tumours following a single invasive procedure.

Electromagnetic Fields↗
PubMedDate not supplied

Non-invasive thermometry using magnetic resonance diffusion imaging: potential for application in hyperthermic oncology.

The proposition to use non-invasive thermometry based on magnetic resonance diffusion imaging for applications in therapeutic hyperthermia is examined. The measurement of proton motion predominantly associated with the self-diffusion of water can be characterized by a Boltzmann temperature dependence (i.e. e-Ea/kT). The activation energy (Ea) is on the order of 0.2 eV and, for a restricted range (approximately 30 degrees) at a base temperature of approximately 300 K, the relationship between the effective diffusion coefficient and temperature is approximately linear. This response has been empirically demonstrated in water-based gel phantoms using magnetic resonance imaging (MRI). Additionally, it is feasible to have compatibility between radiofrequency (RF) heating devices and MRI equipment. An MRI-compatible heating applicator that includes a hexagonal array of coherently phased dipoles was assembled. This heating array easily fits into a standard 1.5 T head imaging coil (diameter 28 cm). The RF fields associated with heating (130 MHz) and imaging (64 MHz) were decoupled using bandpass filters providing isolation in excess of 100 dB. This isolation was sufficient to allow simultaneous imaging and RF heating without deterioration of the image signal-to-noise ratio. In this report temperature, spatial and time resolution achieved in phantom are examined in order to assess the potential for using this non-invasive temperature measurement in applications of hyperthermic oncology. Using this system and conventional multi-slice imaging techniques, 0.5 degrees C resolution in a voxel size of less than 1 cm3 has been achieved using an acquisition time of 4.15 min.

Diffusion↗
PubMedDate not supplied

Radiofrequency capacitive heating of deep-seated tumours using pre-cooling of the subcutaneous tissues: results on thermometry in Dutch patients.

The capacity of a radiofrequency, 13.56 MHz, capacitive hyperthermia system using extensive pre-cooling of the subcutaneous tissue to induce locoregional deep heating has been investigated in 11 patients. Tumour location was presacral in nine--and eccentric towards the lateral side of the pelvis in two patients. For thermometry multiple catheters (mean 2.7) were inserted into the treatment volume. The mean numbers of temperature measuring points per treatment were 9.4 in tumour, 5.5 in muscle and 7.2 in subcutaneous fat. RF energy was applied after 30 min of cooling through two flexible boli perfused with saline water at 5-10 degrees C. Patient tolerance to pre-cooling was very good and after some initial discomfort the patient became rapidly accustomed to the cold water boli. For some patients better temperatures were achieved when the conventional anterior-posterior applicator set-up was replaced by a set-up with an applicator on each lateral side of the patient. As patients can tolerate temperatures within the fat tissue as high as 45.5 degrees C without complaining it appears important to monitor the temperature at the transition of fat to muscle tissue to prevent subcutaneous burns. The study shows that pre-cooling cannot avoid preferential heating at the interface from fat to muscle tissue. In this patient group the quality of the hyperthermia treatment appeared to be rather poor: 60% of the measured tumour temperatures were below 40 degrees D.

Adipose Tissue↗
PubMedDate not supplied

On the accuracy of noninvasive thermometry using molecular diffusion magnetic resonance imaging.

Temperature measurement using magnetic resonance imaging (MRI) of water self-diffusion is investigated. Diffusion images and derived temperatures are obtained in polyacrylamide gel phantom. The temperatures measured from MRI are compared with those from temperature probes to verify their accuracy. In general, the difference between temperatures determined from MRI diffusion images over 0.3 cm3 regions of interest and from temperature probes were 0.2 degrees C. It is concluded that current MRI technology allows noninvasive temperature tomography that is comparable with invasive thermometry with respect to temperature accuracy, has spatial and time resolutions that would be useful in hyperthermic oncology.

Body Temperature↗