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Radiofrequency capacitive hyperthermia for deep-seated tumors. I. Studies on thermometry.

The thermometry results of radiofrequency (RF) capacitive hyperthermia for 60 deep-seated tumors in 59 patients are reported. Hyperthermia was administered regionally using two RF capacitive heating equipments which the authors have developed in cooperation with Yamamoto Vinyter Company Ltd., (Osaka, Japan). Intratumor temperatures were measured by thermocouples inserted through angiocatheters which were placed 5 cm to 12 cm deep into the tissues. Tumor center temperatures were measured for 307 treatments in all tumors; thermal distributions within tumors and surrounding normal tissues were obtained for 266 treatments of 53 tumors by microthermocouples. Thermometry results obtained were summarized as follows. A maximum tumor center temperature greater than 43 degrees C and 42 degrees C to 43 degrees C was obtained in 23 (38%) and 14 (23%) of the 60 tumors respectively. The time required to reach 43 degrees C in the tumor center was within 20 minutes after the start of hyperthermia in 87% of tumors heated to more than 43 degrees C. Temperature variations within a tumor exceeded 2 degrees C in 81% of tumors heated to more than 43 degrees C. The lowest tumor temperature greater than 42 degrees C was achieved in six of the 53 tumors (11%). Of 42 tumors in which temperatures of the subcutaneous fat, surrounding normal tissues, and the tumor center were compared, 24 (57%) showed the highest temperature in the tumor center and ten (24%) in the subcutaneous fat. When the heating efficacy was assessed in terms of a maximum tumor center, it great deal depended on the treatment site, tumor size, thickness of subcutaneous fat, and tumor type. Tumors in the head and neck, thorax, lower abdomen, and pelvis could be heated better than tumors in the upper abdomen. Greater heating efficacy was shown in patients with large, hypovascular tumors, and with the subcutaneous fat measuring less than 15 mm thick. The predominant limiting factor for power elevation was pain associated with heating. Systemic signs including increases in pulse rate and body temperature were not serious and seldom became limiting factors for power elevation. Our thermometry results indicate that the advantages of deep RF capacitive heating are its applicability to various anatomic sites and negligible systemic effects. The disadvantages are that its primary usefulness is limited to patients with thin subcutaneous fat and with large or hypovascular tumors.

Adult↗

[MRI-assisted thermometry for regional hyperthermia and interstitial laser thermotherapy].

PURPOSE: To demonstrate the potential of quantitative MRI-assisted thermometry for the treatment of tumor patients with regional hyperthermia (RHT) and interstitial laser thermotherapy (ILTT). METHODS: Two patients and seven tissue samples were investigated using the T1-relaxation time and the chemical shift of the proton resonance frequency (PRF) as temperature sensitive MRI-parameters at 0.2 and 1.5 T. Thermotherapy was applied using either a dedicated MRI-hyperthermia hybrid system or a temperature controlled laser with 830 nm. RESULTS: Both patients were treated successfully showing clinical benefit. T1 and PRF are depending on the applied thermotherapy method and on the MR-system suitable for MRI-assisted thermometry. The clinical application based on phantom results is not necessarily adequate. CONCLUSION: Clinical application and phantom experiments of RHT and ILTT show the potential of MRI-assisted thermometry for further improvement of both minimal invasive thermotherapy methods. Further investigations concerning optimization of the MRI-techniques, the influence of perfusion or the determination of threshold values are necessary.

Adult↗

Adrenal metastases: CT-guided and MR-thermometry-controlled laser-induced interstitial thermotherapy.

The aim of the study was to evaluate the feasibility, safety and effectiveness of CT-guided and MR-thermometry-controlled laser-induced interstitial thermotherapy (LITT) in adrenal metastases. Nine patients (seven male, two female; average age 65.0 years; range 58.7-75.0 years) with nine unilateral adrenal metastases (mean diameter 4.3 cm) from primaries comprising colorectal carcinoma (n = 5), renal cell carcinoma (n = 1), oesophageal carcinoma (n = 1), carcinoid (n = 1), and hepatocellular carcinoma (n = 1) underwent CT-guided, MR-thermometry-controlled LITT using a 0.5 T MR unit. LITT was performed with an internally irrigated power laser application system with an Nd:YAG laser. A thermosensitive, fast low-angle shot 2D sequence was used for real-time monitoring. Follow-up studies were performed at 24 h and 3 months and, thereafter, at 6-month intervals (median 14 months). All patients tolerated the procedure well under local anaesthesia. No complications occurred. Average number of laser applicators per tumour: 1.9 (range 1-4); mean applied laser energy 33 kJ (range 15.3-94.6 kJ), mean diameter of the laser-induced coagulation necrosis 4.5 cm (range 2.5-7.5 cm). Complete ablation was achieved in seven lesions, verified by MR imaging; progression was detected in two lesions in the follow-up. The preliminary results suggest that CT-guided, MR-thermometry-controlled LITT is a safe, minimally invasive and promising procedure for treating adrenal metastases.

Adrenal Gland Neoplasms↗

Validation of MR thermometry technology: a small animal model for hyperthermic treatment of tumours.

BACKGROUND: Local hyperthermia has been shown to be an effective adjuvant therapy for cancer. However, progress in this treatment modality requires the non-invasive assessment of temperature distribution in the entire tumour to enable administration of an efficient thermal dose to all tumour areas. Magnetic resonance (MR) imaging offers a promising tool to quantify, non-invasively and three-dimensionally, temperature distribution within tumours. An animal model taking into account the complex interrelationship between pathophysiological changes within a tumour during hyperthermia and temperature-sensitive MR parameters is warranted for the development and validation of new MR thermometry technology. METHODS: An experimental set-up was implemented to allow simultaneous measurements of temperature, tumour blood flow and temperature-sensitive MR parameters under standardised conditions in vivo. Local hyperthermia was induced at 44 degrees C for 20 min under inhalation anaesthesia on seven Syrian Golden hamsters bearing an amelanotic melanoma. Fibreoptic probes were used for reference temperature measurements. Laser Doppler flowmetry served for on-line tumour blood flow determination, and MR thermometry was performed using longitudinal T1 relaxation time measurements. RESULTS: The experimental design enables multifunctional MR thermometry. T1 relaxation times of tumours were 1.44 s (1.36, 1.46) and 1.53 s (1. 48, 1.75) at 37 degrees C and during hyperthermia at 44 degrees C, respectively (median, 25% and 75% quartiles, respectively; P<0.05). At the end of 20 min of hyperthermic treatment at 44 degrees C, relative tumour blood flow was reduced to 40.5% (20.7, 43.3) compared to values before treatment (median, 25% and 75% quartiles, respectively; P<0.05). Imaging of T1 relaxation times revealed a heterogeneous distribution in temperature during hyperthermic treatment. CONCLUSION: This novel in vivo model allows standardised investigations for the development and validation of MR thermography methods.

Animals↗

In a systematic review, infrared ear thermometry for fever diagnosis in children finds poor sensitivity.

BACKGROUND AND OBJECTIVES: To investigate sensitivity and specificity of infrared ear thermometry compared to rectal thermometry to detect fever in children. METHODS: Systematic review of studies comparing rectal and infrared ear temperatures in children. RESULTS: Sensitivity and specificity estimates were highly heterogeneous, and displayed an inverse relationship suggestive of a threshold effect, due in part to the different offsets used to obtain adjusted tympanic temperatures depending on the ear thermometer mode. To account for this threshold effect, results from each study were summarized as a diagnostic odds ratio (DOR). These varied extensively across studies, suggesting that heterogeneity between study estimates is not fully explained by the threshold effect. Pooled estimates of sensitivity and specificity from random effects models were 63.7% (95% CI 55.6%, 71.8%) and 95.2% (95% CI 93.5%, 96.9%), respectively. CONCLUSION: Pooled estimates of measures of diagnostic accuracy from these studies suggest that infrared ear thermometry would fail to diagnose fever in three or four out of every 10 febrile children (with fever defined by a rectal temperature of 38 degrees C or above). These findings support our previous concerns about the use of infrared ear thermometers in situations where a failure to detect fever has serious implications.

Adolescent↗

[Otologic determining factors on infra-red tympanic thermometry in children].

OBJECTIVE: To evaluate the influence of different otoscopic findings on body thermometry in children using an infra-red tympanic thermometer. PATIENTS AND METHODS: Body temperature was measured on healthy right and left ear canals with Thermoscan systems. Moreover, it was determined on children with altered otoscopy, companng to normal contralateral ear. To assess its diagnostic fiability, accuracy ratios were calculated in different temperatures. RESULTS: Temperature measured bilaterally did not offer differences, and intra/interassay variation ratios were always less than 0.34%. Acute otitis externa increased tympanic thermometry a mean of 0.36 degrees C (p < 0.001), and cerumen and previously radical surgery decreased a mean of 0.62 and 0.53 degrees C, respectively (p < 0.001). CONCLUSIONS: The conditions mentioned before modify body thermometry if measured by infra-red tympanic thermometer. So, this system must be avoided in these circumstances. Otitis media, fluid in middle ear, tympanic perforation and ventilation tubes did not modify thermometric results.

Child↗

[Measurement of tympanic temperature by infrared and thermocouple thermometry. A comparative study].

OBJECTIVE: To compare tympanic temperatures obtained with an infrared thermometer Core Check 2090A (IVAC), non in contact with the tympanic membrane, to values obtained with a thermocouple thermometer Mon-A-Therm (Mallinckrodt) in contact with it, and to assess whether the differences depend on the person measuring the temperature. STUDY DESIGN: Prospective comparative open study. PATIENTS: The study included 150 adults in whom the tympanic temperatures were measured at their admission to recovery room by 10 nurse anaesthetists. METHODS: Each thermometer was inserted in the same patient into an external acoustic meatus. The median and range of the temperature differences were used to assess the bias and the accuracy of the measures. Their reliability was analyzed with consideration of the measuring person and the presence of irrelevant values, defined as a temperature difference over 0.3 degrees C. RESULTS: The temperatures obtained with both devices were similar (36.2 +/- 0.7 degrees C with IVAC thermometer vs 36.2 +/- 0.8 degrees C with Mallinckrodt thermometer). The median value of the differences was 0 degrees C, with a range of 2.5 degrees C (maximum value + 1.5 degrees C, minimum value: -1 degree C). Nineteen patients could be qualified as hypothermic (temperature < 36.5 degrees C) with one thermometer and normothermic (temperature > or = 36.5 degrees C) with the other. Among them, only 9 (6%) had temperature differences above 0.3 degrees C. The temperature differences were not different according to the measuring nurse. Nevertheless two of them obtained major differences or irrelevant figures. CONCLUSIONS: As compared to the thermocouple thermometry, infrared thermometry has no bias but a low precision. The measurement error does not allow the recognition of hypothermia in 6% of patients. The error may be made by the measuring person and/or related to the anatomy and the patency of the external acoustic meatus. Tympanic infrared thermometry seems to be a convenient method for temperature measurements at short time intervals in the recovery room, provided its limitations are kept in mind.

Adult↗

[Static and dynamic infrared thermometry and thermography in malignant melanoma of the uvea and conjunctiva].

BACKGROUND: Thermometry and -graphy prove asymmetries of the circulation. Contact-free thermometry of the cornea is applied to find out whether this method can contribute to differential diagnosis of ocular melanomas. MATERIALS AND METHODS: Under standardized conditions the temperature of the cornea was measured in 30 patients with malignant melanoma of the choroid and the conjunctiva and 35 healthy subjects. The instruments were a handpyrometer (HPM, Messgerätewerk, Magdeburg) and the thermovision camera of AGA Infrared System, Sweden, with dynamic recording in colour. RESULTS: In healthy subjects there are no significant asymmetries in temperature under standardized conditions. The temperature of the cornea is elevated in both malignant melanomas of the choroid and the conjunctiva. CONCLUSIONS: Thermometry and -graphy of the cornea can contribute to the differentiation of malignant ocular melanomas from other ophthalmological diseases. They are also suited in long term observation of the course of the melanomas.

Body Temperature Regulation↗

A thermometry system for quality assurance and documentation of whole body hyperthermia procedures.

Since December 2001, the Department of Oncology and Medical Physics, Haukeland University Hospital, Norway has been conducting whole body hyperthermia (WBH) studies, treating patients with either ovarian carcinoma or non-Hodgkin lymphomas. Accurate and reliable thermometry instrumentation is important in all types of hyperthermia procedures, particularly in WBH, where the target patient body temperature is 41.8 degrees C. Reliable documentation of side-effects in clinical studies is also dependent on precise temperature monitoring, since in this temperature range even small, but systematic, inaccuracies (0.1-0.2 degrees C) in the temperature monitoring is expected to affect the amount of side effects. Readily available heating and temperature data from previous treatment sessions of the same patient is also valuable for precise temperature control in future treatment sessions. The WBH thermometry system implemented at Haukeland University Hospital is described. It is based on commercially available components, including standard medical thermistor probes, and includes a temperature calibration and verification facility. The thermometry system is accurate, reliable, easy to use, comfortable for the patient and relatively inexpensive. By implementing the Steinhart-Hart polynomial fit to standard medical thermistor probe data, it is shown that the WBH treatment thermometers used can measure the patient body temperatures with a short- and long-term accuracy of +/- 0.01 degrees C.

Body Temperature↗

Noninvasive thermometry using hyperfine-shifted MR signals from paramagnetic lanthanide complexes.

MR thermometry techniques based on the strong water 1H signal provide high spatial and temporal resolution and have shown promise for applications such as laser surgery and RF ablation. However, these techniques have low temperature sensitivity for hyperthermia applications and are greatly influenced by local motion and susceptibility variations. 1H NMR signals from paramagnetic lanthanide complexes of Pr3+, Yb3+ and Tm3+ show up to 300-fold stronger temperature dependence compared to the water 1H signal. In addition, 1H chemical shifts of many of these complexes are insensitive to other factors such as the concentration of the paramagnetic complex, pH, [Ca2+], and the presence of plasma macro-molecules and ions. Applications of lanthanide complexes for temperature measurement in intact animals and the feasibility of mapping temperatures in phantoms have been demonstrated. Among all the lanthanide complexes examined so far, thulium 1, 4, 7, 10-tetramethyl-1, 4, 7, 10-tetraazacyclododecane-1, 4, 7, 10-tetraacetate (TmDOTMA-) appears to be the most attractive for in vivo MR thermometry. The 1H signal from the methyl groups on this complex is relatively intense because of 12 equivalent protons and provides high temperature sensitivity because of the large paramagnetic shifts induced by thulium. The possibility of imaging TmDOTMA2--in intact animals at physiologically safe concentrations has recently been demonstrated. Overall, MR thermometry methods based on hyperfine-shifted MR signals from paramagnetic lanthanide complexes appear promising for animal applications, but further studies relating to acceptable dose and signal-to-noise ratio are necessary before clinical use.

Animals↗

Comparison of thermal damage calculated using magnetic resonance thermometry, with magnetic resonance imaging post-treatment and histology, after interstitial microwave thermal therapy of rabbit brain.

Clinical application of high-temperature thermal therapy as a treatment for solid tumours requires an accurate and close to real-time method for assessing tissue damage. Imaging methods that detect structural changes during heating may underestimate the extent of thermal damage. This is due to the occurrence of delayed damage manifested at tissue locations exposed to temperatures lower than those required to cause immediate structural changes. An alternative approach is to measure temperature and then calculate the expected damage based on the temperature history at each tissue location. Magnetic resonance (MR) imaging methods now allow temperature maps of the target and surrounding tissues to be generated in almost real-time. The aim of this work was to evaluate whether thermal damage zones calculated on the basis of MR thermometry maps measured during heating correspond to actual tissue damage as measured after treatment by histological methods and MR imaging. Four male rabbits were treated with high-temperature thermal therapy delivered in the brain by a single microwave antenna operating at 915 MHz. MR scanning was performed before, during and after treatment in a 1.5 T whole-body scanner. Temperature maps were produced using the proton resonance frequency (PRF) shift method of MR thermometry. In addition, conventional T1-weighted and T2-weighted spin-echo images were acquired after treatment. Thermal damage zones corresponding to cell death, microvascular blood flow stasis and protein coagulation were calculated using an Arrhenius analysis of the MR temperature/time course data. The calculated zones were compared with the lesions seen on histopathological examination of the brains which were removed within 6-8 h of treatment. The results showed that calculated damage zones based on MR thermometry agreed well with areas of damage as assessed using histology after heating was completed. The data suggest that real-time calculations of final expected thermal damage based on an Arrhenius analysis of MR temperature data may provide a useful method of real-time monitoring of thermal therapy when combined with conventional T2-weighted images taken after treatment.

Animals↗

Comparison of digital infrared thermal imaging (DITI) with contact thermometry: pilot data from a sleep research laboratory.

Body temperature regulation is associated with changes in sleep propensity; therefore, sleep research often necessitates concomitant assessment of core and skin surface temperatures. Attachment to thermistors may limit the range of movement and comfort, introducing a potential confound that may prolong sleep initiation or increase wakefulness after sleep onset. It has been suggested that contact thermometry may artificially increase temperatures due to insulation. We report here on a method of remote sensing skin temperatures using a digital infrared thermal imaging (DITI) system, which can reduce these potential confounds. Using data from four healthy young adult volunteers (age = 26.8 +/- 2.2 years; mean +/- SEM), we compared measures of skin temperature using a DITI system with contact thermometry methods already in use in our sleep laboratory. A total of 416 skin temperature measurements (T(sk)) were collected from various sites, resulting in an overall correlation coefficient of R = 0.99 (p < 0.0001) between both methods. Regression analyses for individuals resulted in correlation coefficients between 0.80 and 0.97. These pilot results suggest that DITI can assess skin surface temperatures as accurately as contact thermometry, provided the interest is in relative and not absolute temperature changes. This and some other important limitations are discussed in more detail hereafter.

Adult↗

Use of computerized digital thermometry for diagnosis of Raynaud's phenomenon.

The authors have used computerized digital thermometry for the instrumental diagnosis of Raynaud's phenomenon; such a technique enables them to evaluate the temperature of the ten fingers of the hands separately in baseline conditions, during and after the "cold test." In baseline conditions the mean digital skin temperature was 31.2 degrees C (SD 1.67) in control subjects and 26.8 degrees C (SD 2.84) in patients suffering from Raynaud's phenomenon (p less than 0.001). During the cold test the mean skin temperature decreased to 12.7 degrees C (SD 1.94) in control subjects and to 13.0 degrees C (SD 1.67) in patients (p = n.s.). The mean final skin temperature, at the end of the recovery period after the cold test, was 31.1 degrees C (SD 1.76) in controls and 21.9 degrees C (SD 2.78) in patients (p less than 0.001). The sensitivity of the computerized digital thermometry was high (63.6% and 92.7% for basal and final temperature, respectively), while the specificity was 100% for both values. In conclusion, computerized digital thermometry is a useful technique for the diagnosing and quantifying the extent of Raynaud's phenomenon.

Adult↗

Relationship of symptomatology with closed chamber infrared thermometry and humidity in dry eyes.

PURPOSE: To evaluate the relationship of symptoms of dry eye with closed chamber infrared thermometry and humidity measurements. METHODS: The authors studied 54 patients (108 eyes) with dry eye disorders of different grades of clinical severity (mean age 35.75+/-14.37 years), 31 cases (62 eyes) with normal eyes (mean age 33.68+/-14.42 years), and 10 cases (20 eyes) with epidemic conjunctivitis (mean age 33.68+/-14.42 years). The symptoms and the clinical tests (Schirmer-1 test, fluorescein tear break up time, Lissamine green stain; closed chamber infrared thermometry and humidity) were used to establish the diagnosis of dry eyes. The closed chamber humidity difference was used to classify the groups of dry eye. RESULTS: The authors noted no temperature difference from closed to open eye position in dry eyes as compared to 0.10 +/- 0.00 degrees C difference in normal eyes and epidemic conjunctivitis. Four groups of cases were identified by difference in values of humidity: Group 1 = <0.9 relative humidity (RH)% to 1 RH%; Group 2 = >1 RH% to 1.5 RH%; Group 3 = >1.5 RH% to 2 RH %; and Group 4 = >2 RH%. The symptomatology was measured in the eyes using Oxford scale (0-4) and correlated with the humidity groups. The grading of symptoms with the humidity showed a statistically significant relationship (p<0.0001) in each group. The severity of the symptoms showed an increase in frequency and severity from Group 1 to Group 4, which was statistically significant (p<0.0001). The mean sum total of global symptomatology score was statistically significant (p<0.0001): 3.43 +/- 0.31 in Group 1, 4.65+/-0.42 in Group 2, 8.56 +/- 0.78 in Group 3, and 13.35+/-1.21 in Group 4. However, total symptomatology score in epidemic conjunctivitis did not show a statistically significant value (p=0.20). CONCLUSIONS: The closed chamber humidity and thermometry measurements showed statistical correlation in all four groups of dry eyes to total mean symptomatology score (p<0.001) and showed an increase in value with increasing severity of symptoms. However, all individual symptoms fail to show any conclusive relationship.

Adolescent↗

Is tympanic membrane thermometry the best method for recording temperature in children?

Tympanic membrane thermometry has become increasingly popular for measuring temperature in children. The aim of this review is to ascertain the most appropriate, research-based thermometry method for use with children in acute healthcare settings. The following are considered: Concerns regarding the accuracy of the tympanic membrane thermometer. Whether comparison of the tympanic membrane thermometer with temperature measurement at other body sites is appropriate. How choice of thermometer may be influenced by children's and nurses' preferences, technique, the age of the child, ear size and children with otitis media, perforated eardrums, cerumen (ear wax), ear pain or grommets in-situ. Children's preferences and rectal thermometry in relation to children's rights, which have not been reviewed so far.

Adolescent↗

Use of manganin-constantan thermocouples in thermometry units designed for copper-constantan thermocouples.

Commercial ultrasound hyperthermia systems typically include thermometry units designed for copper-constantan thermocouples. Replacing these copper-constantan thermocouples with manganin-constantan thermocouples is advantageous in reducing the measurement error caused by the conduction of heat along the copper wire, but their performance in these thermometry units is uncertain. The accuracy of manganin-constantan thermocouples in the Labthermics LT-100, Clini-Therm TS1200/TM100, and Physitemp TM-12 thermometry units was investigated using a temperature controlled circulating water bath monitored by a mercury thermometer having a calibration traceable to NIST. The results demonstrate that an accuracy of +/- 0.2 degrees C can be achieved with manganin-constantan thermocouples over the range 35-55 degrees C without hardware modification provided specific calibration procedures are followed. With the Labthermics LT-100, a double point calibration should be carried out at 35 and 55 degrees C. With the Clini-Therm TS1200/TM100, a self-calibration of the unit using its internal calibration well plus a single point calibration using an external temperature standard provides sufficient accuracy. The Physitemp TM-12 requires an external computer for read out and the user must provide additional software to correct for the error by either a single or multiple point calibration.

Copper↗

Tympanic thermometry in Nigerian children.

Rectal and aural temperatures were recorded at the same time in 378 children aged < or = 60 months and were found to be similar across the various age groups, correlation coefficients (r) ranging from 0.61 to 0.91. The mean differences between rectal and aural temperatures varied between -0.06 and 0.25 degree C. Concordance between the two methods ranged from 88.9% to 98% across the temperature range. Tympanic thermometry is simpler, safer and quicker than rectal thermometry and these findings justify the use of aural thermometry in any busy clinical facility for children.

Aging↗

[Measurement of fever in children--is infrared tympanic thermometry reliable?].

BACKGROUND: Our objective was to determine whether infrared tympanic thermometry is as reliable as the rectal digital thermometer. Earlier reports have given conflicting results on the issue. MATERIAL AND METHODS: 199 children aged 1 month to 12 years were included in the study. Rectal temperature and the temperature in at least one ear were obtained from all of the children. Children with perforated otitis media, intracranial tumours or treated with immunosuppressive medication were excluded from the study. RESULTS: The mean temperature in the rectum was 0.4 degree C higher than in the ear. The tympanic and the rectal readings were strongly correlated (r = 0.83, p = 0.01). With a definition of fever as rectal temperature > or = 38 degrees C the sensitivity of the tympanic thermometry was 71%, the specificity 95%, the positive predictive value 93%, and the negative predictive value 78%. INTERPRETATION: Infrared tympanic thermometry has obvious advantages compared to rectal measurements: It is more hygienic, faster and less painful for the child. However, its sensitivity is rather low when used in an emergency department. This means that a number of children with fever will not be diagnosed as such.

Body Temperature↗