Biomedical Engineering Reference
In-Depth Information
Fig. 9.8 Overview of the clinical NMR system . The entire system was redesigned for robust
operation in clinics. The NMR probe accepts samples sealed in disposable tubes to prevent probe
contamination ( left ). NMR coils are embedded into the polymer support to open up the entire coil
bore, and a thin-walled (thickness
65m) tube is used to minimize loss in filling factor. Block
diagram of the NMR electronics for sample excitation and NMR signal reception ( middle ). The
electronics is highly programmable and can be controlled via external terminals. Functional view
of NMR software that processes data and shows graphical output of NMR measurements ( right )
the data to be transferred and consequently decreases the data acquisition time
via USB/Bluetooth connections by more than 10-fold. Transferred NMR data are
then processed to obtain T 2 relaxation time. The overall signal pattern is displayed,
and the data is stored in the terminal device. In addition, wireless communication
module is embedded in the software for data logging/sharing over an encrypted
wireless network, promoting usability in a remote clinical site.
To ensure stable and reliable T 2 relaxation time measurements, a temperature
compensation engine has been implemented to run independently from the main
thread. This temperature compensation engine transforms NMR data from time
domain to frequency domain using fast Fourier transformation (FFT) and detects
any changes in the NMR frequency due to environmental temperature fluctuation
(described below).
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