scholarly journals Parameter Space Mapping for Blood Oxygenation Measurement with Low Field NMR

2021 ◽  
Author(s):  
◽  
Dion Thomas
Keyword(s):  
Magnetic Resonance ◽  
Oxygen Saturation ◽  
Clinical Importance ◽  
Blood Oxygenation ◽  
Physiological Parameter ◽  
T2 Relaxation ◽  
Low Field ◽  
Echo Time ◽  
High Fields ◽  
Field Device

<p><b>Blood oxygenation is a critical physiological parameter for patient health. The clinical importance of this parameter means that measurement of blood oxygenation is a routine part of care. Magnetic resonance provides a way to measure blood oxygenation through the paramagnetic effect of deoxy-haemoglobin, which decreases the T2 relaxation time of blood. This effect has been well characterised at high fields (>1:5 T) for use in Magnetic Resonance Imaging, and it is a contributing factor to the Blood Oxygenation Level Dependent contrast used in functional MRI. However there are relatively few studies of this effect at low magnetic fields, and these have only looked at extreme levels of oxygenation/deoxygenation. To study this effect for potential application in a low-field device, we measured this effect to determine how factors such as oxygenation, field strength and CPMG echo time affect the T2 of blood.</b></p> <p>A continuous flow circuit, similar to a cardiopulmonary bypass circuit, was used to control parameters such as oxygen saturation and temperature, before the blood sample flowed into a variable field magnet (set at fields between 5-40 MHz), where a series of CPMG experiments with echo times ranging from 1 ms to 20 ms were performed to measure the T2. Additionally, the oxygen saturation was continually monitored by an optical sensor, for comparison with the T2 changes. This allowed us to test the sensitivity of this effect at low fields.</p> <p>These results show that at low fields, the T2 relaxation change still follows the trends shown in the literature, with a dependence on B0 squared, and on the fraction of deoxyhaemoglobin squared. Additionally, these results were also compared with two theoretical models for the dependence on echo time, which have previously been tested at high fields: the Luz-Meiboom equation, and the Jensen and Chandra model. Both models gave good agreement with the data measured at low fields. These experiments show that the T2 changes in blood due to oxygenation are still visible at low field, and that this technique should be feasible in a low field device.</p>

scholarly journals Parameter Space Mapping for Blood Oxygenation Measurement with Low Field NMR

2021 ◽  
Author(s):  
◽  
Dion Thomas
Keyword(s):  
Magnetic Resonance ◽  
Oxygen Saturation ◽  
Clinical Importance ◽  
Blood Oxygenation ◽  
Physiological Parameter ◽  
T2 Relaxation ◽  
Low Field ◽  
Echo Time ◽  
High Fields ◽  
Field Device

<p><b>Blood oxygenation is a critical physiological parameter for patient health. The clinical importance of this parameter means that measurement of blood oxygenation is a routine part of care. Magnetic resonance provides a way to measure blood oxygenation through the paramagnetic effect of deoxy-haemoglobin, which decreases the T2 relaxation time of blood. This effect has been well characterised at high fields (>1:5 T) for use in Magnetic Resonance Imaging, and it is a contributing factor to the Blood Oxygenation Level Dependent contrast used in functional MRI. However there are relatively few studies of this effect at low magnetic fields, and these have only looked at extreme levels of oxygenation/deoxygenation. To study this effect for potential application in a low-field device, we measured this effect to determine how factors such as oxygenation, field strength and CPMG echo time affect the T2 of blood.</b></p> <p>A continuous flow circuit, similar to a cardiopulmonary bypass circuit, was used to control parameters such as oxygen saturation and temperature, before the blood sample flowed into a variable field magnet (set at fields between 5-40 MHz), where a series of CPMG experiments with echo times ranging from 1 ms to 20 ms were performed to measure the T2. Additionally, the oxygen saturation was continually monitored by an optical sensor, for comparison with the T2 changes. This allowed us to test the sensitivity of this effect at low fields.</p> <p>These results show that at low fields, the T2 relaxation change still follows the trends shown in the literature, with a dependence on B0 squared, and on the fraction of deoxyhaemoglobin squared. Additionally, these results were also compared with two theoretical models for the dependence on echo time, which have previously been tested at high fields: the Luz-Meiboom equation, and the Jensen and Chandra model. Both models gave good agreement with the data measured at low fields. These experiments show that the T2 changes in blood due to oxygenation are still visible at low field, and that this technique should be feasible in a low field device.</p>

Advances in Magnetic Resonance Imaging of the Pelvis at 0.15 Tesla

1986 ◽  
Vol 27 (4) ◽  
pp. 369-377 ◽  
Author(s):  
D. J. Hamlin ◽  
H. Pettersson ◽  
J. O. Johnson ◽  
J. R. Fitzsimmons
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Resonance ◽  
Relaxation Times ◽  
Resonance Imaging ◽  
T2 Relaxation ◽  
Low Field ◽  
Radiofrequency Coils ◽  
Magnetic Resonance Imaging Mri ◽  
Mass Lesions

The recent development of improved commercial radiofrequency coils and multiecho, multislice software for low field strength magnetic resonance systems has markedly increased the clinical utility of magnetic resonance imaging (MRI) of the pelvis at low field strengths. An evaluation of 70 patients with a variety of pelvic lesions and 14 normal volunteers who were studied using 0.15 T resistive magnet scanner revealed that anatomic structures and a variety of mass lesions could be clearly depicted in transaxial, sagittal and coronal planes using this updated system. Accurate characterization of lesions was possible in many instances using T2 weighted multiecho scans with echo time (TE) ranging from 30 ms to 120 ms (45 ms–180 ms using a reduced bandwidth technique). T1 weighted multislice scans demonstrated anatomic structures to best adantage and calculation of T1 and T2 relaxation times frequently facilitated more accurate differential diagnosis, particularly in the case of ovarian lesions.

scholarly journals Low-Field Nuclear Magnetic Resonance Characteristics of Biofilm Development Process

2021 ◽  
Vol 9 (12) ◽  
pp. 2466
Author(s):  
Yajun Zhang ◽  
Yusheng Lin ◽  
Xin Lv ◽  
Aoshu Xu ◽  
Caihui Feng ◽  
...  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Biofilm Formation ◽  
Development Process ◽  
Bacterial Cells ◽  
T2 Relaxation ◽  
Biofilm Growth ◽  
Low Field ◽  
Biofilm Development ◽  
Nuclear Magnetic

To in situ and noninvasively monitor the biofilm development process by low-field nuclear magnetic resonance (NMR), experiments should be made to determine the mechanisms responsible for the T2 signals of biofilm growth. In this paper, biofilms were cultivated in both fluid media and saturated porous media. T2 relaxation for each sample was measured to investigate the contribution of the related processes to T2 relaxation signals. In addition, OD values of bacterial cell suspensions were measured to provide the relative number of bacterial cells. We also obtained SEM photos of the biofilms after vacuum freeze-drying the pure sand and the sand with biofilm formation to confirm the space within the biofilm matrix and identify the existence of biofilm formation. The T2 relaxation distribution is strongly dependent on the density of the bacterial cells suspended in the fluid and the stage of biofilm development. The peak time and the peak percentage can be used as indicators of the biofilm growth states.

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