Pad´e quantification of malignant and benign ovarian MRS data - Signal Processing in MRS with Biomedical Applications - page 280

the lowest value (3.09) for a highgrade ovarian cancer and the highest value
(3.15) for a benign ovarian lesion.
It is still technically di cult to encode good quality time signals in vivo from
the ovary, due to motion artefacts from respiratory and peristaltic movements
[335]. Because of the small size and motion of this organ, in vivo MRS of the
ovary is mired by problems of resolution and SNR. Nevertheless, initial results,
particularly at higher magnetic field strength and with meticulous attention
to technical considerations such as voxel placement and localized shimming
suggest that in vivo MRS [339] could potentially yield clinically important
information for ovarian cancer diagnostics.

9.2 Insights for ovarian cancer diagnostics from in vitro

MRS

There are quite a bit more published data on ovarian cancer using in vitro
MRS. The findings from these investigations generally indicate a better dis
tinction between malignant from benign ovarian lesions. Moreover, insights
can be gleaned about molecular mechanisms.
Wallace et al. [340] analyzed 19 normal ovarian samples, 3 that had bor
derline pathology and 37 ovarian carcinomas. Their analysis was based upon
amplitude ratios of peaks at 0.9 ppm (lipid methyl), 1.3 ppm (lipid methy
lene), 1.7 ppm (lysine and polyamines) and 3.2 ppm (choline). The normal
or benign samples were distinguished from borderline and neoplastic ovarian
samples with a sensitivity of 95% and specificity of 86% [340].
Smith and Blandford [341] distinguished normal and benign from borderline
and cancerous ovary with 95% sensitivity and 86% specificity. They used lin
ear discriminant analysis training using leaveoneout (12 normal, 22 cancer)
for analysis of 7 normal and 15 cancer specimens from the ovary. There were
six discriminating peaks: 1.47 ppm (fatty acid), 1.68 ppm (lysine), 2.80 ppm
(fatty acid), 2.97 ppm (creatine), 3.17 ppm (choline) and 3.34 ppm (taurine).
In their study of fluid samples from 9 malignant and 19 ovarian cysts, Mas
souger et al. [342] reported higher concentrations of lactate, isoleucine, valine,
methionine and alanine in the cancerous specimens, but generally with wide,
overlapping ranges. These authors also found higher 3hydroxybutyrate and
pyruvic acid in the malignant ovarian cyst fluid, noting that rapid cellular
metabolism will lead to elevated 3hydroxybutyric acid. The high concentra
tions of branched chain amino acids (isoleucine, leucine, and valine) were con
sidered to be protein breakdown products related to proteolysis and necrosis.
This investigation [342] also included an endometrioma located in the adnexal
region, whose fluid showed much higher levels of isoleucine, valine, threonine,
alanine, lysine, methionine, and glycine than did the cancerous ovarian cysts.