Electricity: measuring and testing – Particle precession resonance – Using a nuclear resonance spectrometer system
Patent
1994-04-11
1996-01-23
O'Shea, Sandra L.
Electricity: measuring and testing
Particle precession resonance
Using a nuclear resonance spectrometer system
324307, G01R 3348
Patent
active
054867630
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to a method to display with combined color quantitative images of tissue parameters obtained with nuclear magnetic resonance (quantitative magnetic color imaging, QMCI).
More particularly, this invention relates to a method to synthetically represent tissue parameters by means of pseudonatural color images to be employed with nuclear magnetic resonance.
The documents mentioned herein with a reference numeral are listed at the end of this disclosure.
Nuclear magnetic resonance (NMR) or magnetic resonance imaging (MRI) is largely employed for tissue investigations for diagnostic purposes (1).
The signal obtained in spin-echo sequences, which are those most commonly employed in NMR, is given by the function: are meant, said sequences consisting in the repetition of a set of two radiofrequency pulses, which are called the 90.degree. and 180.degree. pulses, the set being characterized by the time of repetition TR equal to the interval between the 90.degree. pulses and by the time of echo TE which is equal to twice the distance between the 90.degree. and the 180.degree. pulse, that generates a NMR signal which is called the echo at an interval TE from the 90.degree. pulse; T1 and T2 are the longitudinal and transverse relaxation times which are characteristic for the voxel of the tissue to be analyzed, N(H) is the number of the hydrogen atoms, TR and TE are the repetition time and the echo time respectively that characterize the sequence of pulses which is employed for the acquisition of the image, K is an efficiency constant that varies with the experimental conditions. The voxel is the volume element that contributes to the formation of the image element.
The expression 1) does not take into account second-order effects such as diffusion, chemical shift etc. The NMR image is thus not like the X-ray computerized tomography (CT), a map of one only physical parameter (e.g. the electronic density), but it is a function of a number of parameters that characterize the tissue under examination. The main parameters among those mentioned above are the T1 and the T2. The proton density, which is a signal multiplication factor, in most soft tissues has an almost constant value, so that it is not a significative parameter as far as the tissue characterization is concerned.
Users of such methodologies, in order to formulate a diagnosis, carry out at present a number of acquisition sequences of said tissues varying the TR and the TE so as to obtain a number of images with different weights of T1 and T2. Thus a global evaluation is performed of such parameters or of parameters depending on them. Such evaluation is not absolute, but it is relative to reference tissues such as fatty parts, muscles, the brain parenchyma, the cerebrospinal fluid, and so on. The remainder of the diagnostic information comes from the morphology of the observed tissues. Moreover, it is to be remarked from the expression 1) that in the NMR image the T2 gives a direct contribution to the formation of the signal, whereas the T1 gives an inverse contribution. Accordingly, with the same values of T1, tissues having a longer T2 show brighter than tissues having a shorter T2, whereas with the same values of T2, tissues having a longer T1 show darker than those having a shorter T1. Such king of representation which is that usually employed in the present NMR technology is not necessarily the best one from the diagnostic standpoint.
Methods for the production of color images as applied also to magnetic resonance are disclosed in the technical literature, but in many cases the images employed are those of the MR signal (2-5). In order to modulate with different information the chromatic components of color images, different acquisition sequences are employed. The results are not much reproducible, and in addition they are difficult to interpret and of poor iconographic quality.
Setting forth in advance that by the term pixel it is to be understood the image element, i.e. the matrix element which is represen
REFERENCES:
patent: 4789831 (1988-12-01), Mazo, Jr.
patent: 5332968 (1994-07-01), Brown
Klamman et al, "Unified Multiple Feature Color Display for MR Images", Mag Res in Med vol. 9 No. 2 (Feb. 1989).
Kuhn et al, "Interactive MR Image Synthesis" Phillips Tech Rev vol. 43 No. 4 pp. 95-103 (Feb. 1987).
Consiglio Nazionale Delle Ricerche
Mah Raymond Y.
O'Shea Sandra L.
LandOfFree
Method to display with combined color multiple quantitative imag does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method to display with combined color multiple quantitative imag, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method to display with combined color multiple quantitative imag will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1506922