On improving the speed and reliability of T₂‐relaxation‐under‐spin‐tagging (TRUST) MRI

Abstract

A T2-Relaxation-Under-Spin-Tagging (TRUST) technique was recently developed to estimate cerebral blood oxygenation, providing potentials for non-invasive assessment of the brain's oxygen consumption. A limitation of the current sequence is the need for long TR, as shorter TR causes an over-estimation in blood R2. The present study proposes a post-saturation TRUST by placing a non-selective 90° pulse after the signal acquisition to reset magnetization in the whole brain. This scheme was found to eliminate estimation bias at a slight cost of precision. To improve the precision, TE of the sequence was optimized and it was found that a modest TE shortening of 3.4ms can reduce the estimation error by 49%. We recommend the use of post-saturation TRUST sequence with a TR of 3000ms and a TE of 3.6ms, which allows the determination of global venous oxygenation with scan duration of 1 minute 12 seconds and an estimation precision of ±1% (in units of oxygen saturation percentage).

Rapid T2- and susceptometry-based CMRO2 quantification with interleaved TRUST (iTRUST)

“…Similar in principle to ASL, tag-control subtraction of each eTE image pair isolates the venous blood signal. A nonselective 90° spoiler RF pulse is applied to reset the magnetization before each tag-control module (Xu et al, 2012b). A two-compartment exchange model is used to relate Y v to T 2 :…”

“…where S 0 is the difference signal at eTE = 0 and a T 1 value of 1.613 seconds is assumed for venous blood (Xu et al, 2012b). …”

The Influence of Noise on Bold-Mediated Vessel Size Imaging Analysis Methods

“…A Malcom-Levitt T 2 preparation was used with a 10 milliseconds Carr-Purcell-Meiboom-Gill time, 27 with effective TEs of 0, 40, 80, and 120 milliseconds, with four tag-control pairs acquired for each preparation time. As per Xu et al, 28 …”

Non-invasive assessment of neonatal brain oxygen metabolism: A review of newly available techniques

“…One recently developed technique that can determine Y v from blood T2 is T2-Relaxation-Under-Spin-Tagging (TRUST) MRI[37–39]. A unique aspect of TRUST MRI is that this method isolates pure venous blood by magnetically labeling the venous blood (using the principle similar to that in ASL MRI), thereby effectively minimizing confounding effects due to partial voluming of surrounding tissue and cerebrospinal fluid[38].…”

“…3A) and CBF measurement by phase-contrast MRI at the brain's feeding arteries (Fig. 3B), provides a whole-brain CMRO2 measurement technique to quantify global CMRO2[24, 39]. This technique is completely non-invasive (no need for any exogenous agents), rapid (<5 min scan time), and reliable (coefficient of variation, CoV<4% in adults)[19].…”