Direct cerebral and cardiac 17O-MRI at 3 Tesla: initial results at natural abundance

Abstract

Cerebral and cardiac (17)O-MRI at natural abundance is feasible at 3 T.

X‐nuclei imaging: Current state, technical challenges, and future directions

“…). Cardiac 17 O‐imaging has also been demonstrated . Recently, the focus was shifted towards an improvement of the prior knowledge input in the metabolism model and iterative reconstruction with PVC…”

Quantification of oxygen metabolic rates in Human brain with dynamic 17O MRI: Profile likelihood analysis

“…It can be assumed to be linearly correlated with the concentration of 17 O due to the short relaxation times (26,37,49 O concentration in mmol per gram tissue, the 17 O signal intensities before gas inhalation (i.e., during the baseline phase) were normalized using the H 2 17 O natural abundance of 20.56 mmol/g water , water partition coefficients [0.71 g/mL for WM and 0.83 g/mL for GM (50)], and averaged density of brain tissue of 1.038 g/mL (51).…”

“…Unfortunately, UHF MR systems are not widely available and are not yet used in clinical routine. Recently, feasibility of direct 17 O MRI in human brain and heart at clinical field strengths of 3T has been reported (37), which has the ultimate goal of implementing CMRO 2 quantification at clinical MR systems. In the previous studies, a rebreathing (RB) system was implemented for efficient usage of rare and expensive 17 O 2 gas by re-inhalation of the stored 17 O 2 gas in subsequent inhalation cycles (27,33).…”

In vivo 17 O MRS imaging – Quantitative assessment of regional oxygen consumption and perfusion rates in living brain

“…The feasibility of applying the in vivo 17 O MR technique to hearts has been tested in rats at 9.4T [37, 57] and in human hearts at 3T [54]. The preliminary results as displayed in Figure 7 suggest that it is feasible to establish a noninvasive imaging modality with in vivo 17 O MR detection and appropriate quantification modeling for simultaneously imaging the myocardial oxygen metabolic rate (MVO 2 ) and myocardial perfusion [37].…”

“…It has been shown that a few millimeter spatial resolution in preclinical studies [26, 34, 35, 37–39, 48, 50, 51] and close to a centimeter in human studies [32, 45, 53] with ~10–15 sec temporal resolution can be reached with B 0 ≥ 7T. Relatively lower resolutions are expected with lower field magnets, e.g., a 3T clinical scanner, or when large volume coils are employed [30, 36, 54, 56]. It is worth mentioning that while 17 O MR benefits from the sensitivity gain at a higher field, it also requires a larger RF power to achieve the same RF pulse flip angle because of its low γ-ratio.…”