Biomedical Engineering Reference
In-Depth Information
Fig. 9.9
Automated temperature tracking in the new portable
NMR system
.(
a
)Aflowdiagram
of the temperature compensation engine. The tracking routine searches for the Larmor frequency
f
0
at a given environmental setting, using the successive tracking routines (coarse and fine). Once
f
0
is determined, a full NMR measurement is performed. (
b
) Temperature tracking algorithm. For
a given RF excitation with the frequency f , a spin echo signal is measured and transformed into the
frequency domain via fast Fourier transform (FFT). The coarse search mode checks whether the
amplitude (P) of a peak in the spectral power is larger than the predefined value (P
TH
). In the next
stage, the fine search mode iteratively tunes f until the frequency offset f
d
.
Dj
f
f
0
j
/ reaches the
optimal offset value (
3 kHz). (
c
) The effectiveness of temperature compensation was evaluated
using an MNP solution (T
2
100 ms). When the tracking routine was turned off (
square
), the
T
2
variation was >200 % of its initial value. With the tracking routine turned on (
circle
), the
fluctuation was significantly reduced (<1%). (
d
) The robustness of NMR measurements across
a broad range of temperature (4-50
ı
C) was demonstrated. The
dotted line
indicates a theoretical
prediction (Reproduced from [
57
]. Copyright 2011 RSC Publishing)
9.6
Biological Applications
9.6.1
Cancer Detection and Profiling
Sensitive detection and rapid characterization of tumor cells in minimally processed
biological samples will have significant impact on both biomedical research and
clinical practice. Using the first-generation DMR device (NMR-1)[
22
], DMR
