Improved calculation of the equilibrium magnetization of arterial blood in arterial spin labeling

Ahlgren, André; Wirestam, Ronnie; Knutsson, Linda; Petersen, Esben Thade

doi:10.1002/mrm.27193

Cited by 5 publications

(4 citation statements)

References 26 publications

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“…Nevertheless, further work is necessary to fully estimate the impact of this strategy on calibration methods. Methods for the estimation of the coil sensitivity profile have been proposed, but these require the acquisition of additional data using imaging sequences that are not widely available. Alternatively, a proton density image acquired with a body coil can also be used to obtained an approximate sensitivity map .…”

Section: Discussionmentioning

confidence: 99%

Calibration of arterial spin labeling data—potential pitfalls in post‐processing

Pinto

Chappell

Okell

et al. 2019

Magnetic Resonance in Med

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Section: Discussionmentioning

confidence: 99%

Calibration of arterial spin labeling data—potential pitfalls in post‐processing

Pinto

Chappell

Okell

et al. 2019

Magnetic Resonance in Med

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“…Furthermore, since the original BBPC mapping technique was adapted to use in mice from a previously established technique in humans, CaSTRR imaging should be rapidly translatable back to the clinical setting (Roberts et al, 1996). In fact, a recently published study on healthy human volunteers demonstrated that an alternative method of correcting CBF maps for BBPC variability also resulted in increased contrast between gray and white matter (Ahlgren et al, 2018). This is consistent with our study and highlights the potential benefit of BBPC correction.…”

Section: Discussionmentioning

confidence: 99%

Novel Calibrated Short TR Recovery (CaSTRR) Method for Brain-Blood Partition Coefficient Correction Enhances Gray-White Matter Contrast in Blood Flow Measurements in Mice

2019

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The goal of the study was to develop a novel, rapid Calibrated Short TR Recovery (CaSTRR) method to measure the brain-blood partition coefficient (BBPC) in mice. The BBPC is necessary for quantifying cerebral blood flow (CBF) using tracer-based techniques like arterial spin labeling (ASL), but previous techniques required prohibitively long acquisition times so a constant BBPC equal to 0.9 mL/g is typically used regardless of studied species, condition, or disease. An accelerated method of BBPC correction could improve regional specificity in CBF maps particularly in white matter. Male C57Bl/6N mice ( n = 8) were scanned at 7T using CaSTRR to measure BBPC determine regional variability. This technique employs phase-spoiled gradient echo acquisitions with varying repetition times (TRs) to estimate proton density in the brain and a blood sample. Proton density weighted images are then calibrated to a series of phantoms with known concentrations of deuterium to determine BBPC. Pseudo-continuous ASL was also acquired to quantify CBF with and without empirical BBPC correction. Using the CaSTRR technique we demonstrate that, in mice, white matter has a significantly lower BBPC (BBPC white = 0.93 ± 0.05 mL/g) than cortical gray matter (BBPC gray = 0.99 ± 0.04 mL/g, p = 0.03), and that when voxel-wise BBPC correction is performed on CBF maps the observed difference in perfusion between gray and white matter is improved by as much as 14%. Our results suggest that BBPC correction is feasible and could be particularly important in future studies of perfusion in white matter pathologies.

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“…It has been reported that a uniform, brain-tissue-type-dependent magnetization image could be generated using a sensitivity calibration (Dai et al, 2011). Another study showed that BBPC can be improved by exploiting the partial-volume data to adjust the ratio between BBPC and the proton density-weighted image (Ahlgren et al, 2018). Furthermore, gray-white matter CBF can be enhanced with background suppression methods (van Osch et al, 2009).…”

Section: Discussionmentioning

confidence: 99%

Brain–Blood Partition Coefficient and Cerebral Blood Flow in Canines Using Calibrated Short TR Recovery (CaSTRR) Correction Method

et al. 2019

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The brain–blood partition coefficient (BBPC) is necessary for quantifying cerebral blood flow (CBF) when using tracer based techniques like arterial spin labeling (ASL). A recent improvement to traditional MRI measurements of BBPC, called calibrated short TR recovery (CaSTRR), has demonstrated a significant reduction in acquisition time for BBPC maps in mice. In this study CaSTRR is applied to a cohort of healthy canines (n = 17, age = 5.0 – 8.0 years) using a protocol suited for application in humans at 3T. The imaging protocol included CaSTRR for BBPC maps, pseudo-continuous ASL for CBF maps, and high resolution anatomical images. The standard CaSTRR method of normalizing BBPC to gadolinium-doped deuterium oxide phantoms was also compared to normalization using hematocrit (Hct) as a proxy value for blood water content. The results show that CaSTRR is able to produce high quality BBPC maps with a 4 min acquisition time. The BBPC maps demonstrate significantly higher BBPC in gray matter (0.83 ± 0.05 mL/g) than in white matter (0.78 ± 0.04 mL/g, p = 0.006). Maps of CBF acquired with pCASL demonstrate a negative correlation between gray matter perfusion and age (p = 0.003). Voxel-wise correction for BBPC is also shown to improve contrast to noise ratio between gray and white matter in CBF maps. A novel aspect of the study was to show that that BBPC measurements can be calculated based on the known Hct of the blood sample placed in scanner. We found a strong correlation (R2 = 0.81 in gray matter, R2 = 0.59 in white matter) established between BBPC maps normalized to the doped phantoms and BBPC maps normalized using Hct. This obviates the need for doped water phantoms which simplifies both the acquisition protocol and the post-processing methods. Together this suggests that CaSTRR represents a feasible, rapid method to account for BBPC variability when quantifying CBF. As canines have been used widely for aging and Alzheimer’s disease studies, the CaSTRR method established in the animals may further improve CBF measurements and advance our understanding of cerebrovascular changes in aging and neurodegeneration.

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Improved calculation of the equilibrium magnetization of arterial blood in arterial spin labeling

Cited by 5 publications

References 26 publications

Calibration of arterial spin labeling data—potential pitfalls in post‐processing

Calibration of arterial spin labeling data—potential pitfalls in post‐processing

Novel Calibrated Short TR Recovery (CaSTRR) Method for Brain-Blood Partition Coefficient Correction Enhances Gray-White Matter Contrast in Blood Flow Measurements in Mice

Brain–Blood Partition Coefficient and Cerebral Blood Flow in Canines Using Calibrated Short TR Recovery (CaSTRR) Correction Method

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