Changes in NMR relaxation times of adjacent muscle after implantation of malignant and normal tissue

Magnetic Resonance Imaging of Local Soft Tissue Inflammation Using Gadolinium-DTPA

Chemical inflammation was induced subcutaneously in 10 rats using carrageenan mucopolysaccharide. Dual spin echo (SE) imaging of inflammatory loci was performed employing a 0.35 tesla resistive magnet. In addition, gadolinium-DTPA was administrated intravenously into 5 rats to evaluate the potential benefits of paramagnetic contrast medium for the detection and characterization of inflammatory loci. T2 weighted SE images demonstrated the edematous lesions as zones of high intensity. This was attributed to the increased relaxation times of lesions when compared to the adjacent soft tissue. The inflammation was also delineated on T1 weighted SE images, but only after injection of paramagnetic Gd-DTPA. Carrageenan mucopolysaccharide-in-duced lesions provide a useful experimental model for in vivo evaluation of soft tissue inflammation using magnetic resonance imaging. No special benefit of paramagnetic contrast enhancement was demonstrated in this model of local edema.

Common pharmaceuticals alter tissue proton NMR relaxation properties

Differences in the tissue properties of water are the basis for the detailed anatomic visualization of internal body structures produced by NMR imaging. Physiological and pathological events have the potential to alter proton nuclear magnetic resonance relaxation properties through changes in water environment. In this study, the parenteral injection of pharmaceuticals produced significant changes (12-21%) in proton NMR relaxation times in tissues of treated rats. The extent of relaxation time change was both tissue specific and drug specific. Therefore, the effects of common pharmaceuticals should be considered in the interpretation of T1- and T2-weighted NMR images.

The Wellcome Foundation lecture, 1984. Nuclear magnetic resonance imaging in medicine: medical and biological applications and problems

From early biological work and the first T1 nuclear magnetic resonance (n.m.r.) animal image in 1974, whole-body patient images, by using a two-dimensional Fourier transform method were achieved in Aberdeen in 1980 with a 0.04 T vertical resistive magnet. Different pulse sequences produce images dependent by different amounts on proton density, T1 and T2, and for clinical work it is advantageous to use more than one pulse sequence to image pathology. The slow improvement of spatial resolution with increasing standing magnetic field strength is discussed and information on the T1 and T2 contrast dependence is reviewed: it suggests that the gains from high fields may be less than believed hitherto. Electrocardiogram gating can be used to produce moving images of the beating heart; blood flow can be imaged and surface radiofrequency coils are used for improved detail. N.m.r. imaging has considerable potential for studying response to therapy; mental states and dementia; tissue generation; discriminating body fat and body fluids. Other nuclei such as 23Na can be imaged and the potential to image fluorine-labelled pharmaceuticals could be very exciting; n.m.r. contrast agents are now being developed. Images formed from T1 values measured for each pixel are very useful for diagnosis, but the numerical values themselves are less valuable for distinctive pathological identification. With 15 companies manufacturing n.m.r. imagers and over 200 in use in hospitals, the technique is rapidly becoming established in diagnostic clinical practice and some typical uses are presented.

Changes in NMR relaxation time associated with local inflammatory response

T1 and T2 relaxation values and water contents of rat and rabbit tissues have been measured during the course of local inflammatory reaction to turpentine. For rabbits, NMR transverse sectional images were also obtained by spin-warp imaging. Elevations in T1 values around the injection site occurred within 24 h. In rats, T1 values of fibrosed muscle at the centre of the reaction continued to rise as a cyst formed, encapsulating the turpentine. T1 values of the surrounding muscle decreased towards normal as the reaction progressed. Good correlation between relaxation rate and water content was observed. In the rabbits. T1 values measured in vitro around the injection site were compared with the values obtained from NMR images of living and dead rabbits, T1 values obtained immediately after death were consistently lower than values of the same tissues before death. Factors affecting a comparison of T1 values obtained by the different methods are discussed.