Dataset Information

In vivo whole-blood T2 versus HbO2 calibration by modulating blood oxygenation level in the femoral vein through intermittent cuff occlusion.

ABSTRACT: PURPOSE:To investigate the feasibility of estimating calibration constants (K and T2o ) in vivo for converting whole-blood T2 to blood hemoglobin oxygen saturation (HbO2 ) according to the Luz-Meiboom model, 1/T2=1/T2o+K(1-HbO2)2, where K and T2o are relaxivity and transverse relaxation time of fully saturated blood, respectively. METHODS:A range of HbO2 values was achieved in the superficial femoral vein with intermittent cuff occlusion in seven healthy adults (four males) to establish a calibration curve between blood T2 and HbO2 at 1.5T. HbO2 was derived via MR susceptometry, a technique previously validated, and the transverse relaxation time was quantified with an optimized T2 -prepared balanced steady-state free precession pulse sequence. To evaluate the accuracy of the in vivo calibration method, T2 and HbO2 were quantified in the superior sagittal sinus in six additional subjects and compared with susceptometry. RESULTS:Two sets of gender-specific calibration constants were derived, one for each gender corresponding to hematocrits of 0.47?±?0.02 for males and 0.38?±?0.01 for females, yielding K/T2o ?=?41?Hz/260 ms and 26?Hz/280 ms, respectively. The in vivo calibration returned physiologically plausible superior sagittal sinus SvO2 values (65?±?5% HbO2 ), and there was no significant difference between the results from the two methods (average difference -0.3% HbO2 ). CONCLUSION:The results show feasibility of performing in vivo calibration for converting whole-blood T2 to HbO2 . The proposed approach bypasses the involved and cumbersome processes associated with in vitro calibration. Magn Reson Med 79:2290-2296, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

SUBMITTER: Langham MC

PROVIDER: S-EPMC5811342 | biostudies-literature | 2018 Apr

REPOSITORIES: biostudies-literature

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In vivo whole-blood T<sub>2</sub> versus HbO<sub>2</sub> calibration by modulating blood oxygenation level in the femoral vein through intermittent cuff occlusion.

Langham Michael C MC Rodríguez-Soto Ana E AE Schwartz Nadav N Wehrli Felix W FW

Magnetic resonance in medicine 20170903 4

<h4>Purpose</h4>To investigate the feasibility of estimating calibration constants (K and T<sub>2o</sub> ) in vivo for converting whole-blood T<sub>2</sub> to blood hemoglobin oxygen saturation (HbO<sub>2</sub> ) according to the Luz-Meiboom model, 1/T2=1/T2o+K(1-HbO2)2, where K and T<sub>2o</sub> are relaxivity and transverse relaxation time of fully saturated blood, respectively.<h4>Methods</h4>A range of HbO<sub>2</sub> values was achieved in the superficial femoral vein with intermittent cuf ...[more]

PMID: 28868660

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Project description:To analyze the contribution of the transverse relaxation parameter (T2), macroscopic field inhomogeneities (B0), and blood volume fraction (BVf) to blood oxygen level-dependent (BOLD)-based magnetic resonance (MR) measurements of blood oxygen saturation (SO2) obtained in a brain tumor model.This study was approved by the local committee for animal care and use. Experiments were performed in accordance with permit 380 820 from the French Ministry of Agriculture. The 9L gliosarcoma cells were implanted in the brain of eight rats. Fifteen days later, 4.7-T MR examinations were performed to estimate T2*, T2, BVf, and T2*ΔB0corrected in the tumor and contralateral regions. MR estimates of SO2 were derived by combining T2, BVf, and T2*ΔB0corrected according to a recently described quantitative BOLD approach. Scatterplots and linear regression analysis were used to identify correlation between parameters. Paired Student t tests were used to compare the tumor region with the contralateral region.No significant correlations were found between T2* and any parameter in either tumor tissue or healthy tissue. T2* in the tumor and T2* in the uninvolved contralateral brain were the same (36 msec±4 [standard deviation] vs 36 msec±5, respectively), which might suggest similar oxygenation. Adding T2 information (98 msec±7 vs 68 msec±2, respectively) alone yields results that suggest apparent hypo-oxygenation of the tumor, while incorporating BVf (5.3%±0.6 vs 2.6%±0.3, respectively) alone yields results that suggest apparent hyperoxygenation. MR estimates of SO2 obtained with a complete quantitative BOLD analysis, although not correlated with T2* values, suggest normal oxygenation (68%±3 vs 65%±4, respectively). MR estimates of SO2 obtained in the contralateral tissue agree with previously reported values.Additional measurements, such as BVf, T2, and B0, are needed to obtain reliable information on oxygenation with BOLD MR imaging. The proposed quantitative BOLD approach, which includes these measurements, appears to be a promising tool with which to map tumor oxygenation.

Dataset Information

In vivo whole-blood T2 versus HbO2 calibration by modulating blood oxygenation level in the femoral vein through intermittent cuff occlusion.

Publications

In vivo whole-blood T<sub>2</sub> versus HbO<sub>2</sub> calibration by modulating blood oxygenation level in the femoral vein through intermittent cuff occlusion.

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