Multiplet resonances in MRS data from normal and cancerous prostate - Signal Processing in MRS with Biomedical Applications - page 356

The total absorption shape spectra reconstructed by the FPT (−) at the
same two partial signal lengths: N P = 54 (top panel (i)) and N P = 800
(bottom panel (ii)) for the normal stromal prostate are presented in Fig.
11.5 . Just as in the component spectrum, at N P = 54 the peaks at the
two extremes of the spectrum were resolved and the heights were close to
being correct (lactate and alanine at 1.33 ppm and 1.49 ppm respectively and
myoinositol and lactate at 4.07 ppm and 4.12 ppm, respectively). The peak
near 2.5 ppm, however, appears as a singlet at N P = 54, when it should have a
double serration. A very low amplitude bump appears around 2.85 ppm, this
is asymmetric with a higher right side. At around 3.05 ppm there is a creatine
peak which is wider with a lower amplitude with respect to the creatine peak
on the converged total shape spectrum. A single, wide peak is seen at about
3.25 ppm at N P = 54, but there should be four peaks with a serrated structure
to the left. On the total shape spectrum at N P = 54 the peaks at 3.35
ppm (scylloinositol) and the triply serrated structure corresponding to taurine
centered at 3.43 ppm are completely absent. There are two single peaks near
3.56 ppm and at 3.64 ppm corresponding to myoinositol, but they should be
triply serrated. The polyamine structures expected at around 3.10 ppm and
3.14 ppm are absent. On the bottom panel of Fig. 11.5 the converged total
absorption shape spectrum at N P = 800 for normal stromal prostate shows
that all the 27 resonances are resolved.
The converged absorption component shape spectrum (top panel (i)) and
total absorption shape spectrum (bottom panel (i)) at N P = 800 are com
pared within the expanded region from 2.40 ppm to 3.70 ppm for the normal
stromal prostate ( Fig. 11.6 ). As was true for normal glandular prostate,
phosphocholine at 3.23 ppm and glycerophosphocholine at 3.24 ppm are fully
resolved in the component shape spectrum. However, only one resonance is
seen on the total shape spectrum. Only the converged component spectrum
can be used to determine the actual number of resonances with confidence.
The polyamine peaks are very small in the normal stromal prostate. From
the total shape spectrum it would therefore be even more tenuous than for
the glandular case to ascertain that there are precisely two polyamine com
ponents.
11.3.3 Malignant prostate tissue: MR spectral information
reconstructed by FPT
Table 11.6 displays the Padereconstructed data for prostate cancer at the
two partial signal lengths N P = 500 and N P = 600. At N P = 500 (upper
panel (i)), before convergence, 26 of the 27 resonances were identified. Peak
k = 13, the component of the taurine triplet at 3.250298 ppm was missing.
At N P = 500 the computed concentrations for resonances k = 1−8 and
k = 23−27 were fully correct and all the spectral parameters were exact
for lactate at 1.330148 ppm (k = 1) and at 4.12042 (k = 27), and for the
myoinositol singlet (k = 26) at 4.079235 ppm.