Basic tasks of signal processing in spectroscopy - Signal Processing in MRS with Biomedical Applications - page 26

linear combination of the fundamental Voigt time profiles exp (−γ k t−σ k t 2 /4)

K

d k e −γ k t−σ k t 2 /4 . c(t) = (1.18)

k=1

Here, γ k ≡ω k and d k are complex fundamental frequencies and amplitudes,
whereas the damping factors σ k /4 mimic the magnetic field inhomogeneities.
We will now proceed to address the relevance of signal processing through
MRS as it applies to medical diagnostics.

1.4 Why is this topic relevant for biomedical researchers
and clinical practitioners?
At first glance, this topic might seem far afield from the concerns and purview
of biomedical researchers and clinical practitioners, including especially oncol
ogists. However, with a second look coupled with reflection about the actual
barriers to reliable applications of MRS and MRSI for cancer diagnostics, a
different perspective can emerge.
Nowadays, many clinical MR scanners offer the possibility of automatically
generating MR spectra. This opportunity is naturally welcomed by diagnos
ticians who increasingly recognize that the anatomic information provided
by MRI, while invaluable, is still insu cient for unequivocal identification
and characterization of malignancy and its clear distinction from various be
nign pathologies. Indeed, in the recent period, the role of in vivo MRS for
cancer diagnostics has been highlighted in e.g. Refs. [7], [101]-[113], espe
cially for neurooncology [101, 108], [113]-[115] and prostate cancer [101]-
[104]. Breast cancer detection and prediction of response to chemotherapy
have also been improved by MRS [101, 106, 107, 111], [116]-[118]. Unfortu
nately, however, when one examines these automaticallygenerated spectra,
innumerable dilemmas arise. The interpretation of these spectra is frequently
shrouded by confusion and ambiguity. In actual clinical practice, the outcome
of this endeavor is all too often frustration, and retreat to the familiar realm
of customary anatomical diagnostic modalities. As a consequence, among the
potentially most valuable diagnostic information is left by the wayside. In
fact, MRS has yet to become a standard diagnostic tool in the area where it
is needed the most, for clinical oncology, including especially cancer screening
and surveillance.
Technological improvements have been sought in attempts to solve these
dilemmas. Needless to say, meticulous attention to coil design, shimming,
water suppression, as well as the use of appropriate encoding sequences are
a prerequisite for proper acquisition of MR time signals.

Albeit at higher