Biomedical subjects

A J Blauch

Publications and source records attributed to A J Blauch.

3 recordsLinked to original sources

PubMed2000

Detection of nuclear resonance signals: modification of the receiver operating characteristics using feedback.

The performance of a nuclear resonance detection system can be quantified using binary detection theory. Within this framework, signal averaging increases the probability of a correct detection and decreases the probability of a false alarm by reducing the variance of the noise in the average signal. In conjunction with signal averaging, we propose another method based on feedback control concepts that further improves detection performance. By maximizing the nuclear resonance signal amplitude, feedback raises the probability of correct detection. Furthermore, information generated by the feedback algorithm can be used to reduce the probability of false alarm. We discuss the advantages afforded by feedback that cannot be obtained using signal averaging. As an example, we show how this method is applicable to the detection of explosives using nuclear quadrupole resonance.

Algorithms↗

PubMed1999

Optimization of offset frequency in the SORC pulse sequence using feedback.

The low signal-to-noise ratio (SNR) of nuclear quadrupolar resonance measurements has motivated research on signal enhancement methods, including multipulse sequences that facilitate signal averaging, the development of interlaced pulse sequences, and super-Q coils. More recently, it has been shown that feedback can be used to automatically optimize pulse sequence parameters, maximizing the SNR. This paper extends this work by using feedback to optimize the offset frequency in the strong off-resonant comb pulse sequence. Analysis and results are presented for a sample of sodium nitrite at both liquid nitrogen and room temperatures.

Magnetic Resonance Spectroscopy↗

PubMed1999

Feedback optimization of pulse width in the SORC sequence.

A method for increasing the signal-to-noise ratio (SNR) of nuclear quadrupole resonance (NQR) measurements by automatically adjusting a pulse parameter in real-time is presented. This approach is useful in situations where the optimal pulse parameters cannot be chosen beforehand due to lack of knowledge regarding the system. For example, NQR provides a means for detecting explosives by revealing the presence of (14)N. In this particular application, the distance between the search coil and the explosive, as well as the temperature of the explosive, is unknown. As a result, a fixed set of pulse parameters will not yield the largest SNR for all possible search applications. This paper describes a feedback algorithm that uses measurements of the NQR signal to automatically adjust the pulse width in the strong off-resonant comb sequence to maximize the SNR of the NQR measurement. Experimental results obtained using a sample of sodium nitrite are presented.

Algorithms↗