Department of Radiology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, USA.
Department of Obstetrics and Gynecology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, USA.
Magn Reson Med. 2018 Apr;79(4):2290-2296. doi: 10.1002/mrm.26885. Epub 2017 Sep 3.
To investigate the feasibility of estimating calibration constants (K and T ) in vivo for converting whole-blood T to blood hemoglobin oxygen saturation (HbO ) according to the Luz-Meiboom model, 1/T2=1/T2o+K(1-HbO2)2, where K and T are relaxivity and transverse relaxation time of fully saturated blood, respectively.
A range of HbO 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 T and HbO at 1.5T. HbO was derived via MR susceptometry, a technique previously validated, and the transverse relaxation time was quantified with an optimized T -prepared balanced steady-state free precession pulse sequence. To evaluate the accuracy of the in vivo calibration method, T and HbO were quantified in the superior sagittal sinus in six additional subjects and compared with susceptometry.
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/T = 41 Hz/260 ms and 26 Hz/280 ms, respectively. The in vivo calibration returned physiologically plausible superior sagittal sinus SvO values (65 ± 5% HbO ), and there was no significant difference between the results from the two methods (average difference -0.3% HbO ).
The results show feasibility of performing in vivo calibration for converting whole-blood T to HbO . 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.
根据 Luz-Meiboom 模型，即 1/T2=1/T2o+K(1-HbO2)2，研究在体估计转换全血 T 至血血红蛋白氧饱和度（HbO）的校准常数（K 和 T）的可行性，其中 K 和 T 分别为弛豫率和完全饱和血液的横向弛豫时间。
通过间歇性袖带阻断对 7 名健康成年人（4 名男性）的股浅静脉中的 HbO 值进行调节，以在 1.5T 下建立血液 T 与 HbO 之间的校准曲线。通过先前验证的 MR 磁化率技术得出 HbO 值，并通过优化的 T -准备平衡稳态自由进动脉冲序列量化横向弛豫时间。为了评估体内校准方法的准确性，在另外 6 名受试者的上矢状窦中量化了 T 和 HbO，并与磁化率进行了比较。
得出了两组性别特异性校准常数，分别对应男性和女性的血细胞比容为 0.47±0.02 和 0.38±0.01，产生 K/T=41Hz/260ms 和 26Hz/280ms。体内校准返回了具有生理意义的上矢状窦 SvO 值（65±5%HbO），并且两种方法的结果之间没有显著差异（平均差异为-0.3%HbO）。
结果表明，对转换全血 T 至 HbO 进行体内校准是可行的。该方法避免了与体外校准相关的复杂和繁琐的过程。磁共振医学 79:2290-2296,2018。©2017 国际磁共振学会。
