Resolution enhancement as a key step towards clinical implementation of Padé-optimized magnetic resonance spectroscopy for diagnostic oncology

Abstract

Our overall aim is for the full potential of magnetic resonance spectroscopy (MRS) and magnetic resonance spectroscopic imaging (MRSI) to be realized in oncology. This requires mathematics, without which encoded MRS data are entirely uninterpretable. Mathematics based on the conventional approach, the fast Fourier transform (FFT), and ambiguous fittings of Fourier spectra cannot fulfill the rigorous demands of oncology. It is vital to go beyond the FFT and fitting, to obtain reliable quantitative information via MRS about the metabolic content of tissue. None of the available MRS fitting algorithms could provide the clinically needed information with certainty, namely, the metabolite concentrations. Our more advanced method, the fast Pade transform (FPT) is firmly established as a stable, high-resolution processor, with which metabolite concentrations are unequivocally generated for in vitro MRS data associated with prostate, breast and ovarian cancer. Validation of the FPT has also been performed for in vivo MRS of normal human brain from clinical magnetic resonance scanners (1.5 T) as well as from 4 to 7 T scanners. The FPT successfully handles major problems hindering more widespread clinical application of MRS and MRSI, such as separation of noise from signal, resolution of very dense spectra with multiplet resonances (prostate) and overlapping metabolite resonances (breast, brain). In the present paper, we focus upon the implications of resolution enhancement by the FPT. We conclude that the manner by which the FPT achieves its high resolution accuracy dictates a major reformulation of the concept of data acquisition by encoding a small number of short transient time signals to secure good signal-noise ratio. Pade-guided MRS has distinct clinical advantages in combining improved diagnostic accuracy of MRS with shorter examination times. This shortens turn-around time for patients, making MRS efficient and cost-effective. With Pade-based quantification plus FPT-guided encoding of MRS and MRSI data, MRS can become a reliable, cost-effective tool for diagnostics and various aspects of patient care within oncology.