Variability of magnetic resonance parameters in pituitary adenomas at low temperature.

Temperature dependent spin-lattice relaxation time, T1, measurements were carried out on surgically removed pituitary adenoma tissues at low temperature. Differences were found between samples; the temperature dependence of T1 showed a broad minimum below freezing. The measured data were fitted by theoretical lines to determine various parameters such as activation energy, correlation time and intensity.

Progressive saturation relaxation spectroscopy. Investigations on lens nucleus and cortex at low temperature.

A systematic study of the temperature dependence of progressive saturation relaxation spectra was carried out on the nucleus and cortex of normal and cataractous eye lenses at different temperatures below freezing. A more complicated fine structure was detected, than was previously thought. The method utilized may well be applied in tomography as well.

In vitro assessment of MR relaxation properties of pituitary adenomas.

Proton magnetic relaxation times (T1 and T2) and bound water content were measured in vitro in pituitary adenomas from 15 patients using 90 MHz radiofrequency excitation. These data were compared with those measured in normal pituitary glands obtained from four cats and seven fresh human cadavers. The T1 and T2 measured at 24 degrees C in the tumors (mean +/- SD: 1,170 +/- 80 and 123 +/- 35 ms, respectively) were significantly higher than those of cadaver pituitary (830 +/- 200 and 76 +/- 12 ms) and cat pituitary gland (790 +/- 120 and 69 +/- 10 ms). Although the absolute values were lower, similar differences were present in T1 measured at 4 degrees C. Two-dimensional T2 versus T1 plot was particularly helpful in distinguishing tumor from the normal gland. When tumors were grouped according to density on CT, histology or previous treatment (e.g., irradiation or bromocriptine), there were no significant differences in T1 values between the groups. Bound water content was not found to correlate with T1 or T2 values. We concluded that pituitary adenomas can be distinguished from normal pituitary glands by their different relaxation properties when measured at high frequency in vitro MR.

1H nuclear magnetic resonance study of intervertebral discs. A preliminary report.

In vitro 1H pulse nuclear magnetic resonance (NMR) studies on human intervertebral disc tissues were performed to establish the characteristics of relaxation processes. The spin-lattice relaxation time, bound water and dry matter content were measured. Biopsy material from fresh cadavers was taken from different discs along the spinal column and from different sectors of some single discs. It is suggested that the measured parameters correlate with the biomechanical behavior of discs, which in turn is influenced by function, by exposure to physical stresses, or by aging.

In vitro 1H NMR "mapping" of human intervertebral discs.

Human intervertebral discs were investigated by 1H NMR in vitro. The measured parameters of samples differently located in discs give the "maps" of discs. The spin-lattice relaxation-time maps show similar structure to dry matter and bound water maps, which might mean the future possibility to detect certain disc processes via accurate T1 images.

Freezing-thawing hysteresis. I. NMR detection in human lens.

Human eye lenses were investigated by 1H-NMR as a function of temperature around freezing. Wide hysteresis in line intensity and relaxation time has been found. The hysteresis behavior of the phase transition presents a useful possibility for investigating the structure of water in these materials.

Freezing-thawing hysteresis. II. Investigation of human ocular tissues.

The freezing-thawing behavior of cataractous eye lenses and corneas was investigated by 1H-NMR. The corneas have shown hysteresis similarly to the normal lens. No hysteresis could be demonstrated in cataractous lenses. The transparency of lens seems to be correlated with the existence of the freezing-thawing hysteresis.

Combined 1H-NMR and vacuum dehydration study of rat muscles.

Combined NMR and the vacuum dehydration method were used to study the state of water in rat muscle. Comparative studies were carried out on muscles of young and old mature white rats. The spin-lattice relaxation time was measured as a function of water content. The single-exponential behaviour of the relaxation process indicates a normal fast-exchange process between the different fractions. The more elaborate analysis demonstrates the failure of the original fast-exchange model. It is proved that structural changes take place in the macromolecule/ion/bound water system of the muscle even at the beginning of dehydration. All the muscle water seems to be necessary to maintain the normal natural state of the muscle's molecular structure.

Water fractions in normal and senile cataractous eye lenses studied by NMR.

The state of water and water fractions in normal and senile cataractous eye lenses was studied by the NMR method. Combining NMR with vacuum dehydration provided additional information on multifractional samples. A new mathematical procedure is presented which separates the characteristic parameters of the different fractions and helps to determine the relaxation times and amounts of the fractions. The measurement accuracy enables separation of three different water fractions both in normal and in cataractous lenses.