Proton magnetic relaxation of water sorbed by methaemoglobin crystals

P. m. r. relaxation times ( T 1 and T 2 ) have been measured as a function of regain and temperature for water sorbed by lyophilized methaemoglobin. The purpose of the work was to gain information regarding the nature and extent of water binding by the protein molecules. The T 1 results are interpreted in terms of an exchange between the sixth ligand position of the Fe (III) and other adsorption sites on the protein. At high temperatures the relaxation rate at a given regain reaches a limiting value which allows the fraction of ferric ions hydrated to be calculated. Above 16% regain all the Fe (III) is hydrated. At 21 and 35% regains a maximum appears in the relaxation rate at about -46 °C indicating a contribution from a more mobile phase which produces a T 1 minimum at that temperature. The T 2 data are consistent with a model in which the main contribution to the transverse relaxation rate comes from a tightly bound fraction of the water with ω 0 Ƭ c ≫1. The temperature dependence of T 2 exhibits three different regions: ( a ) a low temperature region where lg T 2 ∝ T -1 ; ( b ) an intermediate region with a steeper increase of T 2 with temperature; and ( c ) a high temperature where T 2 levels off.

Download Full-text

Apparent transverse relaxation rate in human brain varies linearly with tissue iron concentration at 4.7 T

Magnetic Resonance in Medicine ◽

10.1002/mrm.21373 ◽

2007 ◽

Vol 58 (5) ◽

pp. 1054-1060 ◽

Cited By ~ 20

Author(s):

Fumiyuki Mitsumori ◽

Hidehiro Watanabe ◽

Nobuhiro Takaya ◽

Michael Garwood

Keyword(s):

Human Brain ◽

Relaxation Rate ◽

Iron Concentration ◽

Transverse Relaxation Rate ◽

Transverse Relaxation ◽

Tissue Iron

Download Full-text

In Vivo Quantification of Cerebral R2*-Response to Graded Hyperoxia at 3 Tesla

Journal of Clinical Imaging Science ◽

10.4103/2156-7514.150439 ◽

2015 ◽

Vol 5 ◽

pp. 1 ◽

Cited By ~ 2

Author(s):

Grigorios Gotzamanis ◽

Roman Kocian ◽

Pinar S. Özbay ◽

Manuel Redle ◽

Spyridon Kollias ◽

...

Keyword(s):

Magnetic Resonance ◽

Relaxation Rate ◽

Tumor Therapy ◽

Cerebrovascular Reactivity ◽

Oxygen Intake ◽

Transverse Relaxation Rate ◽

Dependent Manner ◽

Relaxation Rates ◽

Transverse Relaxation ◽

Arterial Blood

Objectives: This study aims to quantify the response of the transverse relaxation rate of the magnetic resonance (MR) signal of the cerebral tissue in healthy volunteers to the administration of air with step-wise increasing percentage of oxygen. Materials and Methods: The transverse relaxation rate (R2*) of the MR signal was quantified in seven volunteers under respiratory intake of normobaric gas mixtures containing 21, 50, 75, and 100% oxygen, respectively. End-tidal breath composition, arterial blood saturation (SaO2), and heart pulse rate were monitored during the challenge. R2* maps were computed from multi-echo, gradient-echo magnetic resonance imaging (MRI) data, acquired at 3.0T. The average values in the segmented white matter (WM) and gray matter (GM) were tested by the analysis of variance (ANOVA), with Bonferroni post-hoc correction. The GM R2*-reactivity to hyperoxia was modeled using the Hill's equation. Results: Graded hyperoxia resulted in a progressive and significant (P < 0.05) decrease of the R2* in GM. Under normoxia the GM-R2* was 17.2 ± 1.1 s-1. At 75% O2 supply, the R2* had reached a saturation level, with 16.4 ± 0.7 s-1 (P = 0.02), without a significant further decrease for 100% O2. The R2*-response of GM correlated positively with CO2 partial pressure (R = 0.69 ± 0.19) and negatively with SaO2 (R = -0.74 ± 0.17). The WM showed a similar progressive, but non-significant, decrease in the relaxation rates, with an increase in oxygen intake (P = 0.055). The Hill's model predicted a maximum R2* response of the GM, of 3.5%, with half the maximum at 68% oxygen concentration. Conclusions: The GM-R2* responds to hyperoxia in a concentration-dependent manner, suggesting that monitoring and modeling of the R2*-response may provide new oxygenation biomarkers for tumor therapy or assessment of cerebrovascular reactivity in patients.

Download Full-text

Sodium cation complexation by large crown ethers: sodium-23 NMR chemical shifts and longitudinal and transverse relaxation rate studies of sodium tetraphenylborate-dibenzo-24-crown-8 complexes in nitromethane

Journal of the American Chemical Society ◽

10.1021/ja00300a014 ◽

1985 ◽

Vol 107 (14) ◽

pp. 4167-4171 ◽

Cited By ~ 22

Author(s):

Harald D. H. Stoever ◽

Alfred Delville ◽

Christian Detellier

Keyword(s):

Relaxation Rate ◽

Crown Ethers ◽

Chemical Shifts ◽

Sodium Cation ◽

Transverse Relaxation Rate ◽

Sodium Tetraphenylborate ◽

Cation Complexation ◽

Transverse Relaxation ◽

Nmr Chemical Shifts

Download Full-text

NIMG-60. IDH MUTANT GLIOMAS WITH 1p/19q CO-DELETION ARE LESS ACIDIC THAN NON-CO-DELETED GLIOMAS AS MEASURED WITH PH-WEIGHTED AMINE CEST-MRI AND AMINO ACID PET

Neuro-Oncology ◽

10.1093/neuonc/noz175.729 ◽

2019 ◽

Vol 21 (Supplement_6) ◽

pp. vi174-vi175

Author(s):

Jingwen Yao ◽

David Nathanson ◽

William H Yong ◽

Noriko Salamon ◽

Albert Lai ◽

...

Keyword(s):

Amino Acid ◽

Relaxation Rate ◽

Acid Concentration ◽

Amino Acid Concentration ◽

Transverse Relaxation Rate ◽

Transverse Relaxation ◽

T2 Relaxometry ◽

Amino Acid Pet ◽

Grade Ii ◽

Grade Iii

Abstract 1p/19q co-deleted gliomas are known to have slower growth rates and are more sensitive to chemotherapy and radiotherapy. This may be partially explained by the lower tumor acidosis compared to non-co-deleted gliomas, as extracellular acidosis is one of the driving forces toward tumor invasion and resistance to treatments. Amine CEST-EPI is a fast chemical exchange saturation transfer (CEST) imaging technique sensitive to decreased extracellular pH, transverse relaxation rate, and amino acid concentration. In the current study, we demonstrated that 1p/19q co-deleted gliomas are less acidic than non-co-deleted gliomas, using a combination of pH-sensitive amineCEST-EPI, T2 relaxometry, and 18F-FDOPA (18[F] fluorodopa) amino acid PET. 70 histologically-confirmed glioma patients (World Health Organization WHO grade II, N=35; grade III, N=35) received amine CEST-EPI scans. Among them, 16 patients received 18F-FDOPA PET scan and 45 patients received T2 relaxometry quantification. Mann-Whitney u-test is performed to evaluate the differences. Median MTRasym at 3ppm (magnetization transfer ratio asymmetry at amine proton resonance frequency) within T2 hyperintense lesions was significantly lower in 1p/19q co-deleted gliomas compared to non-co-deleted ones (co-deleted 1.19±0.31%; non-co-deleted 1.66±0.45%; p< 0.0001). The significantly lower MTRasym persists when comparing within grade II (p=0.003), grade III (p=0.031), IDH1 mutated gliomas (p=0.002), and gliomas exhibiting classical oligodendroglial histology (p=0.0007). The ROC analysis shows that the prediction of 1p/19q status using MTRasym has area under the curve (AUC) of 0.80 (sensitivity 75.6%. specificity 72.7%). Median FDOPA and T2 in T2-hyperintense lesions were not different between 1p/19q co-deleted and non-co-deleted tumors (FDOPA p=0.84; T2 p=0.63). Results suggest 1p/19q co-deleted gliomas have notably lower acidity compared with non-co-deleted gliomas, as indicated by lower MTRasym and no differences in amino acid concentration or transverse relaxation rate. Further, data indicate the 1p/19q co-deleted gliomas may have distinct metabolic characteristics and tumor microenvironment that can be measured using pH-sensitive amineCEST-MRI at 3T.

Download Full-text