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Background: A novel technique of thermoablation, using a microtube to deliver pulses of hot water vapour, was tested on a large animal model in order to evaluate its efficacy and potential adverse effects., Materials and Methods: The medical device consisted of a microtube extension connected to a hydropneumatic pump. Pulses of pure water were injected though the microtube where they were heated and delivered as vapour into the target zone. The method was tested on the liver of 12 healthy pigs, either during open surgery or percutaneously under ultrasounds., Results: The technique was efficient and well-tolerated by the animals. Large volumes of necrotic tissue were created in a significantly short time compared to concurrent thermoablative techniques., Conclusion: Anticipating human application, this experimental study demonstrated a safe and efficient innovative thermoablation technique. The first human applications have been successfully performed and will be reported soon.

This paper describes the development of a Polyvinyl alcohol hydrogel (PVA-H) model for calibration and measurement of temperature using image contrast on MRI using DMSO/H_2O as a solvent to alter the freezing and melting points of PVA-H. Tissues exposed to temperature changes above 41 degrees C or below 0 degrees C exhibit increasingly extensive and irreversible damage, depending on the exposure duration. MR images can provide a map of temperature if there is sufficient tissue signal. To evaluate treatment principles using temperature changes (hyperthermia, cryotherapy), a model simulating tissue may be useful to provide a reproducible test environment. PVA-H is water soluble and can be seen on MRI. It can be used to construct complicated shapes such as vascular structure, soft tissues, and so on. Therefore, PVA-H can be useful to measure temperatures and assume the distribution of temperature under treatment. In this paper, we applied PVA-H as a temperature detector and calibrated temperature from image contrast. The results exhibit good capability as a temperature detector not only of high temperature (around 41 degrees C), but also of low temperature (as low as -23 degrees C).

Background: A new method of thermoablation with hot water vapour based on a new type of microtube was developed. This approach allows tumours, with volume and anatomical positions not accessible to other techniques (cryoablation, radiofrequency ablation, laser ablation) to be treated., Materials and Methods: The method was tested on a human colon carcinoma grafted subcutaneously in Swiss nude mice and the experiment monitored under magnetic resonance imaging., Results: It was found that 2.52 cal s(-1) per cm3 of tumour were necessary to reduce tumour size. The microtube is built to withstand a large range of temperatures and pressures and is biocompatible., Conclusion: A specific feature of this technique is that, besides hot vapour, several types of drugs can be delivered through the same microtube depending of the location, type or size of the tumour. These properties make it a unique device for multi-therapeutic treatments.

A human model allowing the non-invasive study of bone marrow haemodynamics has been developed. A decrease in postischaemic tissue reperfusion capability (postischaemic hyperaemia) as a function of age (range 25-72 years) was observed both in the human tibia and tibialis anterior muscle. In the tibia bone marrow the reperfusion capability started to decrease after 50 years and was lower than for muscle for all the age range. Mean basal muscle O(2) saturation (80.8% at 25 years) decreases as a function of age (-0.35%+/-0.13% per year) whereas it remains constant for bone marrow (84.8+/-2.8%). A Monte Carlo simulation has been performed to evaluate the accuracy of the derived O(2) saturation measurements and has shown that this parameter is robust even in the presence of substantial noise. It has also been demonstrated that it is necessary to use a multi wavelength NIR spectrometer and a second derivative based fitting algorithm to obtain reliable measurements from the bone marrow, and that the tissue scattering changes occurring during the protocol do not allow the use of the standard near infrared spectroscopy algorithms. The human tibia bone marrow model presented here and the related measurement technique should enable access to new areas of physiological research.

Human tibia bone marrow (BM) and tibialis anterior muscle (TA) perfusion index (PI) was assessed non-invasively by near infrared spectroscopy. A decrease in the postis-chaemic reperfusion capability of the human tibia BM and TA muscle was observed for increasing age i.e., PI increases linearly as a function of age, starting from 30 years, both for BM (0.062 %/year, from -4.185 to -0.967 %/s) and TA muscle (0.046 %/year, from -5.760 to -3.883 %/s). The results define a "normal" baseline and demonstrate the sensitivity of the method to PI changes. The present technique should allow one to investigate physio-pathological effects induced by microgravity on tibia BM blood perfusion.

The present work was aimed at measuring intramuscular oxygen consumption (O(2)) as a function of temperature (T), in human forearm, during rest and aerobic isometric exercise (4% of the maximal voluntary contraction, MVC). Based upon results from in vitro experiments performed on isolated mitochondria of animal species, it was hypothesised that, during isometric exercise, the O(2)-T curve should display a maximum for some 'optimal' T. Intramuscular T and measurements were performed using a combined deep body temperature/near infrared probe during muscle cooling. At rest, O(2) increased non-linearly and monotonically as a function of T (n=8). O(2) increased approximately 2 times when going from 26 to 36 degrees C. A log(O(2))-T plot or a log(O(2))-1/T did not linearise the data. During isometric contraction, O(2) values at 26.8+/-0.6, 28.6+/-0.9, 31.9+/-0.9 and 35.9+/-0.9 degrees C were 3.04+/-1.26, 7.60+/-1.64, 4.43+/-1.95, and 6.64+/-1.37 micromol 100 g(-1) min(-1), respectively (n=6). The O(2) value at 28.6 degrees C was significantly higher (P<0.05) than that at 26.8 and 31.9 degrees C. The 'sudden' O(2) change at 28.6 degrees C is compatible with the phenomenon observed at the mitochondrial level.

The age dependence of human gastrocnemius Mg2+ concentration is demonstrated. To quantitate Mg2+ concentration, an original and accurate fitting algorithm using quantum mechanics-based prior knowledge is detailed. In a group of 28 volunteers (14 females) in the age range 5-80 years, pH, PCr/ATP and Pi/ATP values in the gastrocnemius were 7.02 +/- 0.02 pH, 4.16 +/- 0.33 and 0.13 +/- 0.02, respectively and independent of age and sex. By contrast, intracellular Mg2+ concentration (mM) decreased linearly (p < 0.05) with age (Mg2+ = 0.7803 +/- 0.0247-0.0027 +/- 0.0005 * age). No difference was found between sexes. From these results, it follows that care must be taken when comparing muscle Mg2+ data from subjects of different age. The hypothesis can be put forward that during aging insufficient intake and/or increased depletion of Mg2+ (e.g., intestinal hypoabsorption or urinary leakage) may affect the musculoskeletal system.

Rationale and Objectives: The authors investigated the usefulness of dynamic phosphorus-31 magnetic resonance (MR) spectroscopy in the assessment of hepatic function by studying the effect of a fructose load on a rat model of liver cirrhosis., Methods: In vivo P-31 MR liver spectra of eight rats with bile duct ligature and 10 control rats were obtained every 4.6 minutes before and after intraperitoneal fructose load (10 mmol per kilogram of body weight)., Results: In the basal spectra of the experimental group, the phosphomonoester peak was higher than in the control group (P = .026). After the fructose load, the phosphomonoester peak increase and the inorganic phosphate peak decrease were significantly less marked in the experimental group (P = .003). There was a linear correlation between the serum level of bilirubin and the phosphomonoester increase (r = .61, P < .001)., Conclusion: Dynamic P-31 MR spectroscopy may be useful in the assessment of hepatic function in chronic liver disease.

Rationale and Objectives: We examined the effects of arterial ischemia on the phagocytic activity of the hepatic macrophage-monocytic phagocytic system (MMPS)., Methods: Six minipigs were studied before and 24 hr after complete arterial devascularization of the liver. Magnetic resonance (MR) imaging was performed at 1.5 T using superparamagnetic iron oxide (SPIO) particles (18 mumol Fe/kg body weight) as an MMPS-specific contrast agent. Hepatobiliary scintigraphy, measurements of serum liver enzymes, and histology also were obtained., Results: On MR imaging, the postcontrast-to-precontrast ratios of the arterially devascularized livers were significantly higher than the corresponding baseline values (p < .01). The greatest difference (52%) between the baseline and the postoperative values was observed on gradient-echo (GE) images. Scintigraphy, laboratory analyses, and histology results indicate that the MR imaging findings were probably predominantly attributable to a reduction in phagocytic activity of the hepatic MMPS., Conclusion: SPIO particles have already proved useful for improving detection of liver neoplasms on MR imaging, but they also may provide a novel way of evaluating the function of the hepatic MMPS in liver diseases.

In order to show that for a possible application in medical diagnosis NMR-relaxation experiments at low Larmor frequencies (v0 less than or equal to 20 kHz) are more sensitive than the up to now done high field measurements in the MHz-range, we present dispersion curves (v0 = 50 Hz to 50 MHz) of the proton longitudinal relaxation time T1 and values of the transversal relaxation time T2 for the example of amniotic fluids. Only for Larmor frequencies below congruent to 100 kHz the relaxation times for healthy amniotic fluid and pathological meconium solutions are significantly different, whereas at high Larmor frequencies, i.e. in the conventional MHz-range, the observed changes are rather small.

Dispersion curves of the longitudinal relaxation T1 of protons in healthy amniotic fluid in a meconium solution are distinct at low Larmor frequencies (V0 less than 100 kHz). We are thus able to distinguish these fluids by T1 measurements in this range.

Measurements are reported of NMR relaxation times (T2) on hydrogen in water of isotonic NaCl solutions and of normal human amniotic fluid in which known concentrations of meconium (fetal feces) were dissolved. Magnetic fields for resonance of 23.5 X 10(3) and 0.6 oersteds were used. From the measured T2 values, reliable estimates of meconium concentrations could be obtained that might be considered estimates of fetal distress. Observed minor variation of T2 values was probably due to the mucopolysaccharides comprising 80% of the meconium weight. Advantages of this technique for possible clinical use in obstetrics include small volume of sample required (0.1 ml), lack of necessity for sample filtration or centrifugation, and shortness of time required for analysis (less than 30 min).