Empirical model of human blood transverse relaxation at 3 T improves MRI T<sub>2</sub>oximetry

Bush, Adam; Borzage, Matthew; Detterich, John; Kato, Roberta M.; Meiselman, Herbert J.; Coates, Thomas D.; Wood, John C.

doi:10.1002/mrm.26311

Cited by 37 publications

(114 citation statements)

References 34 publications

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“…The remaining CPMG T 2 preparation sequence parameters included a repetition time of 1978 ms, 110 cm FOV, 5‐mm slice thickness and in plane resolution of 1.7 mm. These modifications did not alter the fundamental measured T 2b .…”

Section: Methodsmentioning

confidence: 88%

“…Following completion of the ex vivo T 2b measurements, T 2b was derived by applying monoexponential fitting to the blood pool signal and the values were fit to a bilinear relationship of hematocrit (Hct) and oxygen saturation (Y) as follows:

\frac{1}{T_{2 b}} = A_{1} H c t {(1 - Y)}^{2} + A_{2} {(1 - Y)}^{2} + A_{3} H c t + A_{4}

where A 1 , A 2, A 3 , and A 4 are empirically determined coefficients .…”

Section: Methodsmentioning

confidence: 99%

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Diminished cerebral oxygen extraction and metabolic rate in sickle cell disease using T2 relaxation under spin tagging MRI

Bush

Coates

Wood

2017

Magnetic Resonance in Med

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Purpose T2 MRI oximetry can non-invasively determine oxygen saturation (Y) but requires empirical MR calibration models to convert the measured blood transverse relaxation (T2b) into Y. The accuracy of existing T2b models in the presence of blood disorders such as sickle cell disease (SCD) remains unknown. Methods A Carr Purcell Meiboom Gill T2 preparation sequence was used to make 83 whole blood measurements from 11 subjects with SCD in order to derive an ex-vivo hemoglobin S (HbS) T2b model. Forearm venous blood gas, sagittal sinus T2 (T2 Relaxation Under Spin Tagging) and total brain blood flow (phase contrast MRI) were measured in 37 healthy controls and 33 SCD subjects (age 24.6 ± 10.2 years). Cerebral oxygen saturation, extraction fraction and metabolic rate estimates were calculated using three separate T2b models. Cerebral and forearm oxygen extraction fraction were compared. Results Ex-vivo, SCD blood had greater saturation dependent relaxivity than control blood, with a weak dependence on HbS and no dependence on hematocrit. In-vivo, the HbS T2b model predicted Yv values with lowest coefficient of variation (compared to existing T2b models) and the strongest correlation with peripheral venous oximetry (r2=.29). The HbS T2b model predicted systematically higher Yv measurements in SCD patients (73 ± 5 and 61 ± 6, p<0.0001) which was mirrored by peripheral venous measurements (75 ± 20 and 45 ± 20, p<0.0001). Conclusion Cerebral and peripheral oxygen extraction are decreased in SCD patients, suggesting either blood flow is increased beyond metabolic demands or the presence of physiological arterial-venous shunting.

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Section: Methodsmentioning

confidence: 88%

\frac{1}{T_{2 b}} = A_{1} H c t {(1 - Y)}^{2} + A_{2} {(1 - Y)}^{2} + A_{3} H c t + A_{4}

where A 1 , A 2, A 3 , and A 4 are empirically determined coefficients .…”

Section: Methodsmentioning

confidence: 99%

Diminished cerebral oxygen extraction and metabolic rate in sickle cell disease using T2 relaxation under spin tagging MRI

Bush

Coates

Wood

2017

Magnetic Resonance in Med

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135

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“…Numerical simulations revealed that velocity and B1 + strength were the strongest contributors to diminished labeling efficiency and resultant errors between PCASL and PC CBF measurements. At typical carotid velocities and oxygen saturations, differences in T 2 values for healthy and anemic subjects (200ms-300ms) contributed <1.5% to labeling efficiency(10). …”

Section: Resultsmentioning

confidence: 99%

“…The model parameters used were chosen similar to arterial human blood including T 2 = 200ms(10), T 1 = 1600ms(9). Numerical simulations were performed on resonance, in the rotating frame with a numerical step size of 3.6 μs.…”

Section: In Vivo Imagingmentioning

confidence: 99%

“…Anemic subjects have elevated CBF(6), high blood velocities(7), shorter vascular transit times(8) and longer blood relaxation times(9,10). In sickle cell disease (SCD), quantification is complicated further by abnormal blood properties (shorter T1 for a given hematocrit(11)) and cerebrovascular disease (stroke(12,13), vessel tortuosity(14)).…”

Section: Introductionmentioning

confidence: 99%

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Pseudo continuous arterial spin labeling quantification in anemic subjects with hyperemic cerebral blood flow

Bush

Chai

Choi

et al. 2018

Magnetic Resonance Imaging

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Purpose To investigate possible sources of quantification errors in global cerebral blood flow (CBF) measurements by comparing pseudo continuous arterial spin labeling (PCASL) and phase contrast (PC) MRI in anemic, hyperemic subjects. Methods All studies were performed on a Philips 3T Achieva MRI scanner. PC and PCASL CBF examinations were performed in 10 healthy, young adult subjects and 18 young adults with chronic anemia syndromes including sickle cell disease and thalassemia. CBF estimates from single and two compartment ASL kinetic models were compared. Numerical simulation and flow phantom experiments were used to explore the effects of blood velocity and B1+ on CBF quantification and labeling efficiency. Results PCASL CBF underestimated PC in both populations using a single compartment model (30.1±9.2% control, 45.2±17.2% anemia). Agreement substantially improved using a two-compartment model (−8.0 ± 6.0% control, 11.7 ± 12.3% anemia). Four of the anemic subjects exhibited venous outflow of ASL signal, suggestive of cerebrovascular shunt, possibly confounding PC-PCASL comparisons. Additionally, sub-study experiments demonstrated that B1+ was diminished at the labeling plane (82.9 ± 5.1%), resulting in suboptimal labeling efficiency. Correcting labeling efficiency for diminished B1+, PCASL slightly overestimated PC CBF in controls (−15.4 ± 6.8%) and resulted in better matching of CBF estimates in anemic subjects (0.7 ± 10.0% without outflow, 10.5 ± 9.4% with outflow). Conclusions This work demonstrates that a two-compartment model is critical for PCASL quantification in hyperemic subjects. Venous outflow and B1+ under-excitation may also contribute to flow underestimation, but further study of these effects is required.

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Cerebral oxygen metabolism in adults with sickle cell disease

et al. 2020

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In sickle cell disease (SCD), oxygen delivery is impaired due to anemia, especially during times of increased metabolic demand, and cerebral blood flow (CBF) must increase to meet changing physiologic needs. But hyperemia limits cerebrovascular reserve (CVR) and ischemic risk prevails despite elevated CBF. The cerebral metabolic rate of oxygen (CMRO2) directly reflects oxygen supply and consumption and may therefore be more insightful than flow‐based CVR measures for ischemic risk in SCD. We hypothesized that adults with SCD have impaired CMRO2 at rest and that a vasodilatory challenge with acetazolamide would improve CMRO2. CMRO2 was calculated from CBF and oxygen extraction fraction (OEF), measured with arterial spin labeling and T2‐prepared tissue relaxation with inversion recovery (T2‐TRIR) MRI. We studied 36 adults with SCD without a clinical history of overt stroke, and nine healthy controls. As expected, CBF was higher in patients with SCD versus controls (mean ± SD: 74 ± 16 versus 46 ± 5 mL/100 g/min, P < .001), resulting in similar oxygen delivery (SCD: 377 ± 67 versus controls: 368 ± 42 μmol O2/100g/min, P = .69). OEF was lower in patients versus controls (27 ± 4 versus 35 ± 4%, P < .001), resulting in lower CMRO2 in patients versus controls (102 ± 24 versus 127 ± 20 μmol O2/100g/min, P = .002). After acetazolamide, CMRO2 declined further in patients (P < .01) and did not decline significantly in controls (P = .78), indicating that forcing higher CBF worsened oxygen utilization in SCD patients. This lower CMRO2 could reflect variation between healthy and unhealthy vascular beds in terms of dilatory capacity and resistance whereby dysfunctional vessels become more oxygen‐deprived, hence increasing the risk of localized ischemia.

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Empirical model of human blood transverse relaxation at 3 T improves MRI T₂oximetry

Cited by 37 publications

References 34 publications

Diminished cerebral oxygen extraction and metabolic rate in sickle cell disease using T2 relaxation under spin tagging MRI

Diminished cerebral oxygen extraction and metabolic rate in sickle cell disease using T2 relaxation under spin tagging MRI

Pseudo continuous arterial spin labeling quantification in anemic subjects with hyperemic cerebral blood flow

Cerebral oxygen metabolism in adults with sickle cell disease

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Empirical model of human blood transverse relaxation at 3 T improves MRI T2oximetry

Cited by 37 publications

References 34 publications

Diminished cerebral oxygen extraction and metabolic rate in sickle cell disease using T2 relaxation under spin tagging MRI

Diminished cerebral oxygen extraction and metabolic rate in sickle cell disease using T2 relaxation under spin tagging MRI

Pseudo continuous arterial spin labeling quantification in anemic subjects with hyperemic cerebral blood flow

Cerebral oxygen metabolism in adults with sickle cell disease

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Empirical model of human blood transverse relaxation at 3 T improves MRI T₂oximetry