Optimization of NQR Pulse Parameters using Feedback Control

Schiano, J.L.; Blauch, A.J.; Ginsberg, Mark D.

doi:10.1515/zna-2000-1-213

Cited by 11 publications

(5 citation statements)

References 2 publications

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“…Incrementing of the transmitter frequency requires re-tuning and/or re-configuration of the probe, which can be extremely time consuming. Automated NQR systems capable of scanning a wide range of frequencies have been developed to address this problem [45][46][47][48][49], though they are not widely available. Both manual and automated experiments benefit from broadband excitation pulses, which serve to reduce the number of frequency increments, and may aid in mapping out broad distributions of quadrupolar frequencies.…”

Section: Introductionmentioning

confidence: 99%

The application of frequency swept pulses for the acquisition of nuclear quadrupole resonance spectra

Rossini

Hamaed

Schurko

2010

Journal of Magnetic Resonance

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Section: Introductionmentioning

confidence: 99%

The application of frequency swept pulses for the acquisition of nuclear quadrupole resonance spectra

Rossini

Hamaed

Schurko

2010

Journal of Magnetic Resonance

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“…The approach that was taken in this study could furthermore be used to optimize other types of image contrasts, such as that obtained with (double) inversion recovery or fluid‐attenuated inversion recovery (FLAIR). Finally, the FBL mechanism offers a flexible framework that could be used to optimize a wide variety of scan parameters, besides inversion times, on the fly 25–28 . This could help to improve the image quality for scan protocols that are sensitive to system imperfections and other intersubject differences, 29 such as in the case of diffusion‐weighted imaging.…”

Section: Discussionmentioning

confidence: 99%

“…Finally, the FBL mechanism offers a flexible framework that could be used to optimize a wide variety of scan parameters, besides inversion times, on the fly. [25][26][27][28] This could help to improve the image quality for scan protocols that are sensitive to system imperfections and other intersubject differences, 29 such as in the case of diffusion-weighted imaging.…”

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confidence: 99%

Subject‐specific optimization of background suppression for arterial spin labeling magnetic resonance imaging using a feedback loop on the scanner

et al. 2022

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Background suppression (BGS) in arterial spin labeling (ASL) magnetic resonance imaging leads to a higher temporal signal-to-noise ratio (tSNR) of the perfusion images compared with ASL without BGS. The performance of the BGS, however, depends on the tissue relaxation times and on inhomogeneities of the scanner's magnetic fields, which differ between subjects and are unknown at the moment of scanning. Therefore, we developed a feedback loop (FBL) mechanism that optimizes the BGS for each subject in the scanner during acquisition. We implemented the FBL for 2D pseudo-continuous ASL scans with an echo-planar imaging readout. After each dynamic scan, the acquired ASL images were automatically sent to an external computer and processed with a Python processing tool. Inversion times were optimized on the fly using 80 iterations of the Nelder-Mead method, by minimizing the signal intensity in the label image while maximizing the signal intensity in the perfusion image. The performance of this method was first tested in a four-component phantom. The regularization parameter was then tuned in six healthy subjects (three males, three females, age 24-62 years) and set as λ = 4 for all other experiments. The resulting ASL images, perfusion images, and tSNR maps obtained from the last 20 iterations of the FBL scan were compared with those obtained without BGS and with standard BGS in 12 healthy volunteers (five males, seven females, age 24-62 years) (including the six volunteers used for tuning of λ). The FBL resulted in perfusion images with a statistically significantly higher tSNR (2.20) compared with standard BGS (1.96) (p < 5 x 10 À3 , two-sided paired t-test). Minimizing signal in the label image furthermore resulted in control images, from which approximate changes in perfusion signal can directly be appreciated. This could be relevant to ASL applications that require a high temporal resolution. Future work is needed to minimize the Abbreviations used: ASL, arterial spin labeling; BGS, background suppression; EPI, echo-planar imaging; FBL, feedback loop; FLAIR, fluid-attenuated inversion recovery; TSE, turbo-spin-echo; tSNR, temporal signal-to-noise ratio; XTC, eXTernal Control.

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“…In [25] a feedback algorithm that automatically adjusts NQR pulse parameters to increase SNR was experimentally shown. In the proposed method, the measurements of NQR response (specifically the signal power) between RF pulses were used to optimize pulse parameters (pulse duration and frequency of excitation) in real time.…”

Section: Signal Processing Algorithmsmentioning

confidence: 99%

“…Although by using fixed pulse parameters the detected signal strength is sacrificed, tests in [25][26][27] were made under controlled conditions in the absence of MAPER. The presence of such signals could degrade the performance of the control system since they are added to the signal power that is used for feedback.…”

Section: Signal Processing Algorithmsmentioning

confidence: 99%

Nuclear quadrupole resonance for explosive detection

Cardona

Jiménez

Vanegas

2015

Ingeniare. Rev. chil. ing.

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Nuclear quadrupole resonance (NQR) is a spectroscopic technique that can detect explosives of high chemical specificity and therefore it is very suitable for the landmine detection problem. There are several factors affecting the relation of noise signal ratio with NQR: molecular dynamics of relaxation, interference signals, thermal noise, explosive amount, distance, temperature and the design of the detecting system. Literature has searched ways for solving one or more of these factors, but since not all the work has been focused on landmine detection, many have only been tested in simulation or with data obtained under controlled laboratory conditions, where the detection is not remote (there is no separation between the sample and the detection system). This paper makes a review of the state of art in NQR, analyzing its relevance to the landmine detection problem and concluding about unsolved problems that could be the focus of future research.Keywords: Nuclear quadrupole resonance, landmine detection, explosive detection, landmine, demining. RESUMEN

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Optimization of NQR Pulse Parameters using Feedback Control

Cited by 11 publications

References 2 publications

The application of frequency swept pulses for the acquisition of nuclear quadrupole resonance spectra

The application of frequency swept pulses for the acquisition of nuclear quadrupole resonance spectra

Subject‐specific optimization of background suppression for arterial spin labeling magnetic resonance imaging using a feedback loop on the scanner

Nuclear quadrupole resonance for explosive detection

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