Blood T1 Research Articles

Integrating omics techniques and culture-independent systems may improve the detection of persistent candidemia: data from an observational study

IntroductionBlood cultures have low sensitivity for candidemia. Sensitivity can be improved by the culture-independent system T2 Magnetic Resonance (T2). SeptiCyte RAPID is a host response assay quantifying the risk of infection-related inflammation through a scoring system (SeptiScore). We investigate the performance of SeptiScore in detecting persistent candidemia as defined by conventional cultures and T2.MethodsThis is a prospective multicentre observational study on patients with candidemia. Blood cultures and blood samples for assessment by T2 and SeptiCyte were collected for 4 consecutive days after the index culture. The performance of SeptiScore was explored to predict persistent candidemia as defined by (1) positive follow-up blood culture (2) either positive follow-up blood culture or T2 sample.Results10 patients were enrolled including 34 blood collections assessed with the 3 methods. Overall, 4/34 (12%) follow-up blood cultures and 6/34 (18%) T2 samples were positive. A mixed model showed significantly higher SeptiScores associated with persistent candidemia when this was defined as either a positive follow-up blood culture or T2 sample (0.82, 95%CI 0.06 to 1.58) but not when this was defined as a positive follow-up blood culture only (-0.57, 95%CI -1.28 to 0.14). ROC curve for detection of persistent candidemia by SeptiScore at day 1 follow-up showed an AUC of 0.85 (95%CI 0.52-1.00) when candidemia was defined by positive follow-up blood culture, and an AUC of 1.00 (95%CI 1.00–1.00) when candidemia was defined according to both methods.ConclusionIntegrating transcriptome profiling with culture-independent systems and conventional cultures may increase our ability to diagnose persistent candidemia.

Estimating synthetic hematocrit and extracellular volume from native blood pool T1 times at 3 Tesla CMR: Derivation of a conversion equation, accuracy and comparison with published formulas

PurposeCalculation of extracellular volume fraction (ECV), a marker of myocardial fibrosis in cardiac magnetic resonance imaging (CMR), requires hematocrit (Hct). We aimed to correlate Hct levels with native blood T1 times, to derive a formula for estimating synthetic Hct (Hctsyn) and synthetic ECV (ECVsyn), to assess accuracy of ECVsyn and to compare our model with published formulas. MethodIn this retrospective study, a cohort of 250 CMR scans with T1 mapping (3T, MOLLI 5(3)3, endsystolic aquisition), was divided into a derivation and validation cohort. Native T1 times of the left ventricular blood pool (T1native,midLV) were correlated with Hct levels from blood sampling within 24 h (Hct24h) and a formula for calculation of Hctsyn was derived by linear regression. ResultsIn the derivation cohort (n = 167), Hct24h showed a good association with T1native,midLV (r = −0.711, p < 0.001). The resulting regression equation was Hctsyn = 1/T1native,midLV * 1355.52–0.310. In the validation cohort (n = 83), Hctsyn and Hct24h showed good correlation (r = 0.726, p < 0.001), while ECVsyn, and ECV24h demonstrated excellent correlation (r = 0.940, p < 0.001). ECVsyn had a minimal bias of 0.28 % and the misclassification rate (8.8 %) was comparable to the variability introduced by repeated Hct measurements (misclassification in 7.5 %). Applying published formulas in our cohort resulted in incorrect classification in up to 60 %. ConclusionWe provide a formula for estimating Hctsyn from native blood T1 on a 3T scanner. The measurement error of ECVsyn is low and comparable to the error due to retest variability of conventional Hct. Scanner- and sequence-specific formulas should be used.

Sex-and age-related variations in myocardial tissue composition of the healthy heart: a native T1 mapping cohort study.

Cardiovascular diseases manifest differently in males and females, potentially influenced by inherent sex- and age-related differences in myocardial tissue composition. Such inherent differences are not well-established in the literature. With this study using cardiac magnetic resonance (CMR) native T1 mapping, we aim to determine the effect of sex and age on myocardial tissue composition in healthy individuals. CMR native T1 mapping was performed in 276 healthy individuals (55% male, age 8---84 years) on a 1.5 Tesla scanner using a MOLLI 5(3)3 acquisition scheme. Additionally, 30 healthy participants (47% male, age 24-68 years) underwent a 1-year follow-up CMR to assess the longitudinal changes of native T1. Mean native T1 values were 1000 ± 22 ms in males and 1022 ± 23 ms in females [mean difference (MD) = 22 ms, 95% confidence interval (CI) (17, 27)]. Female sex was associated with higher native T1 in multivariable linear regression adjusting for age, heart rate, left ventricular mass index, and blood T1 [β=10 ms, 95% CI (3.4, 15.8)]. There was no significant interaction between sex and age (P = 0.27). Further, age was not associated with native T1 [β=0.1 ms, 95% CI (-0.02, 0.2)], and native T1 did not change during a 1-year period [MD -4 ms, 95% CI (-11, 3)]. Female sex was associated with higher native T1; however, there was no association between age and native T1. Additionally, there was no evidence of an interaction between sex and age. Our findings indicate intrinsic sex-based disparities in myocardial tissue composition.

Diagnostic and Prognostic Potential of Multiparametric Renal MRI in Kidney Transplant Patients.

Multiparametric MRI provides assessment of functional and structural parameters in kidney allografts. It offers a non-invasive alternative to the current reference standard of kidney biopsy. To evaluate the diagnostic and prognostic utility of MRI parameters in the assessment of allograft function in the first 3-months post-transplantation. Prospective. 32 transplant recipients (54 ± 17 years, 20 females), divided into two groups according to estimated glomerular filtration rate (eGFR) at 3-months post-transplantation: inferior graft function (IGF; eGFR<45 mL/min/1.73 m2 , n = 10) and superior graft function (SGF; eGFR ≥ 45 mL/min/1.73 m2 , n = 22). Further categorization was based on the need for hemodialysis (C1) and decrease in s-creatinine (C2) at 1-week post-transplantation: delayed-graft-function (DGF: n = 4 C1, n = 10 C2) and early graft-function (EGF: n = 28 C1, n = 22 C2). 3-T, pseudo-continuous arterial spin labeling, T1-mapping, and diffusion-weighted imaging. Multiparametric MRI was evaluated at 1-week in all patients and 3-months after transplantation in 28 patients. Renal blood flow (RBF), diffusion coefficients (ADC, ΔADC, D, D, D*, flowing fraction f), T1 and T1 were calculated in cortex and medulla. The diagnostic and prognostic value of these parameters, obtained at 3-months and 1-week post-transplantation, respectively, was evaluated in the cortex to discriminate between DGF and EGF, and between SGF and IGF. Logistic regression, receiver-operating-characteristics, area-under-the-curve (AUC), confidence intervals (CIs), analysis-of-variance, t-test, Wilcoxon-Mann-Whitney test, Fisher's exact test, Pearson's correlation. P-value<0.05 was considered significant. DGF patients exhibited significantly lower cortical RBF and f and higher D*. The diagnostic value of MRI for detecting DGF was excellent (AUC = 100%). Significant differences between patients with IGF and SGF were found in RBF, ∆T1 , and ∆D. Multiparametric MRI showed higher diagnostic (AUC = 95.32%; CI: 88%-100%) and prognostic (AUC = 97.47%, CI: 92%-100%) values for detecting IGF than eGFR (AUC = 89.50%, CI: 79%-100%). Multiparametric MRI may show high diagnostic and prognostic value in transplanted patients, yielding better results compared to eGFR measurements. 2 TECHNICAL EFFICACY: Stage 1.

Relationship of Liver Blood Tests and T1 Relaxation Time With Intra-pancreatic Fat Deposition

Liver is well recognised as a metabolically active organ. While intra-pancreatic fat deposition (IPFD) is emerging as an important player in the whole-body metabolism, the interplay between the liver and IPFD has been poorly investigated. This study aimed to investigate the associations of liver blood tests and non-invasive tests for hepatic fibrosis with IPFD. Participants underwent a 3.0 Tesla magnetic resonance imaging to measure IPFD and map liver T1 (longitudinal relaxation time). Four liver tests were done on the same sample of blood. Hepatic fibrosis risk score (BARD) was calculated. Linear regression models were built, accounting for age, sex, visceral-to-subcutaneous fat ratio, and other covariates. A total of 143 individuals were studied. In the most adjusted model, alkaline phosphatase (P<0.001), alanine aminotransferase (P<0.001), and γ-glutamyl transferase (P=0.042) were significantly positively associated with IPFD. The BARD score was not significantly associated with IPFD in the most adjusted model (P=0.295). T1 relaxation time of the liver was not significantly associated with IPFD in the most adjusted model (P=0.782). Elevated alkaline phosphatase, alanine aminotransferase, and γ-glutamyl transferase are associated with increased IPFD. Hepatic fibrosis does not appear to be associated with IPFD.

Effect of Feeding Common Carp with Different Quantities of a Certified Commercial Feed on Haematological Parameters, Blood Indicators and Cortisol Hormone Levels

This study was conducted at fish laboratory affiliated to the department of animal production/ college of agriculture/ University of Anbar. The experiment lasted eight weeks (5 /Sep / 2022-31 /Oct / 2022) in Aquatic Recirculating System (ARS), to examine the appropriate effect of feeding common carp with different quantities of a certified commercial feed on hematological parameters, blood indicators, and cortisol hormone levels revealed that significant differences among the treatments. In the second treatment (T2), there was significant improvement (P≤0.05) in red blood cell count, hematocrit, hemoglobin, and white blood cell count compared to the other experimental treatments. Treatment four (T4) showed superiority in lymphocyte count, while treatment three (T3) exhibited higher values in both monocytes count and monocyte to lymphocyte ratio (P≤0.05). regarding the biochemical blood parameters, treatments T6, T5, T4, T2, and T1 demonstrated significant superiority (P≥0.05) over treatment three (T3) in terms of cholesterol, triglycerides, low-density lipoprotein, very low-density lipoprotein, ALT enzyme, and AST enzyme. However, high-density lipoprotein exhibited significant differences (P≤0.05) in treatments T5 and T4. As for cortisol levels, treatment two (T2) displayed significant superiority over the other experimental treatments (P>0.05).

Diurnal oscillations of MRI metrics in the brains of male participants

Regulation of biological processes according to a 24-hr rhythm is essential for the normal functioning of an organism. Temporal variation in brain MRI data has often been attributed to circadian or diurnal oscillations; however, it is not clear if such oscillations exist. Here, we provide evidence that diurnal oscillations indeed govern multiple MRI metrics. We recorded cerebral blood flow, diffusion-tensor metrics, T1 relaxation, and cortical structural features every three hours over a 24-hr period in each of 16 adult male controls and eight adult male participants with bipolar disorder. Diurnal oscillations are detected in numerous MRI metrics at the whole-brain level, and regionally. Rhythmicity parameters in the participants with bipolar disorder are similar to the controls for most metrics, except for a larger phase variation in cerebral blood flow. The ubiquitous nature of diurnal oscillations has broad implications for neuroimaging studies and furthers our understanding of the dynamic nature of the human brain.

Factors affecting performance of fetal blood T2 measurements for noninvasive estimation of oxygen saturation.

To ultimately make accurate and precise fetal noninvasive oxygen saturation (sO2 ) measurements by T2 -prepared bSSFP more widely available by systematically assessing error sources in order to potentially reduce perinatal mortality in cardiovascular malformations and fetal growth restriction. T2 -prepared bSSFP data were acquired in phantoms; in flowing blood in adults in the superior sagittal sinus, ascending and descending aorta, and main pulmonary artery; and in the fetal descending aorta and umbilical vein. T2 was assessed in relation to T2 two- or three-parameter curve-fitting techniques, SSFP readout, refocusing time delay (τ), constant and pulsatile blood flow, and impact of T1 recovery. Further, fetal T2 and sO2 variability were quantified in the descending aorta and umbilical vein in healthy fetuses and fetuses with cardiovascular malformation (gestational weeks 32-38). In phantoms, three-parameter fitting was accurate irrespective of phase FOV (<4 ms; i.e., <2%), and T2 was overestimated (up to 23 ms/10%; p = 0.001) beyond ±30 Hz off-resonance. In the adult aorta, T2 was underestimated during higher blood flow velocities and pulsatility for τ = 16 ms (-41 ms/-17%; p = 0.008). In fetuses, two-parameter fitting overestimated T2 compared with three-parameter fitting (+33 ms/+18%; p = 0.03). T2 variability was 18 ms/15% in the fetal descending aorta and 28 ms/14% in the umbilical vein. The resulting estimated sO2 variability was ∼10% (15% of sO2 value) in the fetal descending aorta. Errors due to T2 -fitting techniques, off-resonance, flow velocity, and insufficient T1 recovery between image acquisitions could be mitigated by using three-parameter fitting with included saturation-prepared images approximating infinite T2 -preparation time, adequate shimming covering the fetus and placenta, and by modifying acquisition parameters. Variability in fetal blood T2 and sO2 , however, indicate that it is currently not feasible to use these methods for prediction of disease.

Evaluation of methemoglobin as an intravascular contrast agent: T1 relaxation time effect in a rabbit model

ObjectiveAlternative contrast agents for MRI are needed for individuals who may respond adversely to gadolinium, and need an intravascular agent for specific indications. One potential contrast agent is intracellular methemoglobin, a paramagnetic molecule that is normally present in small amounts in red blood cells. An animal model was used to determine whether methemoglobin modulation with intravenous sodium nitrite transiently changes the T1 relaxation of blood. MethodsFour adult New Zealand white rabbits were treated with 30 mg intravenous sodium nitrite. 3D TOF and 3D MPRAGE images were acquired before (baseline) and after methemoglobin modulation. T1 of blood was measured with 2D ss EPl acquisitions with inversion recovery preparation performed at two-minute intervals up to 30 min. T1 maps were calculated by fitting the signal recovery curve within major blood vessels. ResultsBaseline T1 was 1758 ± 53 ms in carotid arteries and 1716 ± 41 ms in jugular veins. Sodium nitrite significantly changed intravascular T1 relaxation. The mean minimum value of T1 was 1126 ± 28 ms in carotid arteries 8 to 10 min after the injection of sodium nitrite. The mean minimum value of T1 was 1171 ± 52 ms in jugular veins 10 to 14 min after the injection of sodium nitrite. Arterial and venous T1 recovered to baseline after a period of 30 min. ConclusionMethemoglobin modulation produces intravascular contrast on T1-weighted MRI in vivo. Additional studies are needed to safely optimize methemoglobin modulation and sequence parameters for maximal tissue contrast.

T1 mapping in population ageing

Abstract Funding Acknowledgements Type of funding sources: None. Background The world’s population is ageing: every country is experiencing growth in both the size and the proportion of older people. Common health states in older age mainly include cardiovascular disease. To ensure that our health system is ready to face this demographic shift, we investigated native and post-contrast T1 mapping as a quantitative method to appraise its clinical potential in older people. Purpose This article aimed to provide reference values of T1 mapping for quantification of the expansion of the extracellular matrix in older people. Methods We retrospectively selected subjects ranged in age from 86 to 101 years old that underwent contrast cardiac magnetic resonance (CMR). All subjects were imaged on a 1.5 T system. T1 measurements were performed with a Modified Look Lockers Inversion (MOLLI) recovery sequence. Regions of interest (ROI) were drawn in the left ventricle for blood T1 measurement and in the interventricular septum. We used T1 data obtained before and after contrast injection. We also measured the volume and function of both ventricles. Rho di Spearman was used for correlations. Results We analysed 29 patients (mean age 88.58±3.13 years old). Mean value of T1 in the blood pool (T1bp) was 1647.43±107.66 before contrast and 357.18±63.94 after contrast. Mean value of T1 in the septum (T1s) was 1012.86±38.41 before contrast and 488.68±69.29 after contrast. Left ventricle (LV) EDVI was 48.11±15.29 ml/m2 and ESVI 16.49±8.59 ml/m2, LV ejection fraction (EF) and stroke volume (SV) were 66.38±9.65 % and 52.39±18.84 ml respectively. Right ventricle (RV) EDVI was 46.44±13.19 ml/m2 and ESVI 16.97±5.93 ml/m2, LV ejection fraction (EF) and stroke volume (SV) were 63.46±8.65 % and 49.29±18.63 ml respectively. A significant negative correlation was found between age and T1s before contrast (r=-0.405 and p = 0.015). Positive correlations were found also between T1s before contrast and LV volumes. Conclusions This study shows a correlation between T1 mapping and population ageing.

Functional magnetic resonance imaging reveals dysfunction of the paraspinal muscles in patients with chronic low back pain: a cross-sectional study.

Patients with chronic low back pain (CLBP) undergo structural changes of the paraspinal muscles; however, it is unclear if functional changes also occur. This study aimed to examine the metabolic and perfusion function changes in the paraspinal muscles of patients with CLBP as indirectly reflected by blood oxygen level-dependent (BOLD) imaging and T2 mapping. All participants were consecutively enrolled at our local hospital from December 2019 to November 2020. Patients were diagnosed with CLBP in the outpatient clinic, and asymptomatic participants were considered to be those with no CLBP or other diseases. This study was not registered on a clinical trial platform. Participants underwent BOLD imaging and T2 mapping scans at the L4-S1 disc level. The effective transverse relaxation rate (R2* values) and transverse relaxation time (T2 values) of the paraspinal muscles were measured on the central plane of the L4/5 and L5/S1 intervertebral discs. Finally, the independent samples t-test was used to assess the differences in R2* and T2 values between the 2 groups, while Pearson correlation analysis was used to determine their correlation with age. A total of 60 patients with CLBP and 20 asymptomatic participants were enrolled. The paraspinal muscles of the CLBP group had higher total R2* values [46.7±2.9 vs. 44.0±2.9 s-1; 95% confidence interval (CI): 1.2-4.2; P=0.001] and lower total T2 values (45.4±4.2 vs. 47.1±3.7 ms; 95% CI: -3.8 to 0.4; P=0.109) than did the asymptomatic participants. For the different muscles, R2* values for the erector spinae (ES) (L4/5: 45.5±2.6 vs. 43.0±3.0 s-1, 95% CI: 1.1-4.0, P=0.001; L5/S1: 48.5±4.9 vs. 45.9±4.2 s-1; 95% CI: 0.2-5.1; P=0.035) and the R2* values of the multifidus (MF) muscles (L4/5: 46.4±2.9 vs. 43.7±3.5 s-1, 95% CI: 1.1-4.3, P=0.001; L5/S1: 46.3±3.5 vs. 42.5±2.8 s-1, 95% CI: 2.1-5.5, P<0.001) of the CLBP group at both spinal levels were higher than those of the asymptomatic participants. In the patients with CLBP, the R2* values at the L4/5 (45.9±2.1 s-1) were lower than those at the L5/S1 (47.4±3.6 s-1; 95% CI: -2.6 to -0.4; P=0.007). The R2* values were positively correlated with age in both groups (CLBP group: r=0.501, 95% CI: 0.271-0.694, P<0.001; asymptomatic group: r=0.499, 95% CI: -0.047 to 0.771; P=0.025). The R2* values were higher in the paraspinal muscles of patients with CLPB and may suggest metabolic and perfusion dysfunction of the paraspinal muscles in these patients.

Histopathologic Validation of Stress T1 Mapping in Myocardial Ischemia: Another Step toward Clinical Translation?

Histopathologic Validation of Stress T1 Mapping in Myocardial Ischemia: Another Step toward Clinical Translation?

Venous Blood Oxygenation Measurements Using TRUST and T2-TRIR MRI During Hypoxic and Hypercapnic Gas Challenges.

Oxygen extraction fraction (OEF) and cerebral metabolic rate of oxygen (CMRO2 ) may serve as biomarkers in several diseases. OEF and CMRO2 can be estimated from venous blood oxygenation (Yv ) levels, which in turn can be calculated from venous blood T2 values (T2b ). T2b can be measured using different MRI sequences, including T2-relaxation-under-spin-tagging (TRUST) and T2-prepared-blood-relaxation-imaging-with-inversion-recovery (T2-TRIR). The latter measures both T2b and T1 (T1b ) but was found previously to overestimate T2b compared to TRUST. It remained unclear, however, if this bias is constant across higher and lower oxygen saturations. To compare TRUST and T2-TRIR across a range of O2 saturations using hypoxic and hypercapnic gas challenges. Prospective. Twelve healthy volunteers (four female, age 36 ± 10 years). A 3T; turbo-field echo-planar-imaging (TFEPI), echo-planar-imaging (EPI), and fast-field-echo (FFE). TRUST- and T2-TRIR-derived T2b , Yv , OEF, and CMRO2 were compared across different respiratory challenges. T1b from T2-TRIR was used to estimate Hct (HctTRIR ) and compared with venipuncture (HctVP ). Shapiro-Wilk, one-sample and paired-sample t-test, repeated measures ANOVA, Friedman test, Bland-Altman, and correlation analysis. Bonferroni multiple-comparison correction was performed. Significance level was 0.05. A significant bias was observed between TRUST- and T2-TRIR-derived T2b , Yv , and OEF values (-13 ± 11 msec, -5.3% ± 3.5% and 5.9 ± 4.1%, respectively). For Yv and OEF, this bias was constant across the range of measured values. T1b was significantly lower during severe hypoxia and hypercapnia compared to baseline (1712 ± 86 msec and 1634 ± 79 msec compared to 1757 ± 90 msec). While no significant bias was found between HctVP and HctTRIR (0.02% ± 0.06%, P = 0.20), the correlation between these Hct values was significant but weak (r = 0.19). Given the constant bias, TRUST- and T2-TRIR-derived venous T2b values can be used interchangeably to estimate Yv , OEF, and CMRO2 across a broad range of oxygen saturations. Hct from T2-TRIR-derived T1-values only weakly correlated with Hct from venipuncture. 2 TECHNICAL EFFICACY: Stage 2.

Right and left ventricular blood pool T2 ratio on cardiac magnetic resonance imaging correlates with hemodynamics in patients with pulmonary hypertension

ObjectivesOur objective is to compare the right/left ventricular blood pool T1 ratio (RVT1/LVT1), and right/left ventricular blood pool T2 ratio (RVT2/LVT2) on Cardiac Magnetic Resonance Imaging (CMR) between patients with pulmonary hypertension (PH) and normal controls, to analyze the correlation of RVT1/LVT1, RVT2/LVT2 and hemodynamics measured with right heart catheterization (RHC) in patients with PH.MethodsForty two patients with PH and 40 gender-and age-matched healthy controls were prospectively included. All patients underwent RHC and CMR within 24 h. The right and left ventricular blood pool T1 and T2 values were respectively measured, and RVT1/LVT1 and RVT2/LVT2 between the PH group and the healthy control were compared. Meanwhile, the correlation between RVT1/LVT1, RV/LVT2 ratio and hemodynamic parameters in patients with PH respectively was analyzed.ResultsIn the control group, RVT2 was significantly lower than LVT2 (t = 6.782, p < 0.001) while RVT1 also was lower than LVT1 (t = 8.961, p < 0.001). In patients with PH, RVT2 was significantly lower than LVT2 (t = 9.802, p < 0.001) while RVT1 was similar to LVT1 (t = − 1.378, p = 0.176). RVT2/LVT2 in the PH group was significantly lower than that in the control group (p < 0.001). RVT1/LVT1 in PH patients increased in comparison with the control group (p < 0.001). RVT2/LVT2 negatively correlated with pulmonary vascular resistance (r = − 0.506) and positively correlated with cardiac index (r = 0.521), blood oxygen saturation in Superior vena cava, right atrium, right ventricle and pulmonary artery (r = 0.564, 0.603, 0.648, 0.582).ConclusionsRVT2/LVT2 on T2 mapping could be an additional CMR imaging marker that may assist to evaluate the severity of PH.

Increased cardiac involvement in Fabry disease using blood-corrected native T1 mapping

Fabry disease (FD) is a rare lysosomal storage disorder resulting in myocardial sphingolipid accumulation which is detectable by cardiovascular magnetic resonance as low native T1. However, myocardial T1 contains signal from intramyocardial blood which affects variability and consequently measurement precision and accuracy. Correction of myocardial T1 by blood T1 increases precision. We therefore deployed a multicenter study of FD patients (n = 218) and healthy controls (n = 117) to investigate if blood-correction of myocardial native T1 increases the number of FD patients with low T1, and thus reclassifies FD patients as having cardiac involvement. Cardiac involvement was defined as a native T1 value 2 standard deviations below site-specific means in healthy controls for both corrected and uncorrected measures. Overall low T1 was 135/218 (62%) uncorrected vs. 145/218 (67%) corrected (p = 0.02). With blood-correction, 13/83 previously normal patients were reclassified to low T1. This reclassification appears clinically relevant as 6/13 (46%) of reclassified had focal late gadolinium enhancement or left ventricular hypertrophy as signs of cardiac involvement. Blood-correction of myocardial native T1 increases the proportion of FD subjects with low myocardial T1, with blood-corrected results tracking other markers of cardiac involvement. Blood-correction may potentially offer earlier detection and therapy initiation, but merits further prospective studies.

Value of Right and Left Ventricular T1 and T2 Blood Pool Mapping in Patients with Chronic Thromboembolic Hypertension before and after Balloon Pulmonary Angioplasty

Parametric imaging has taken a steep rise in recent years and non-cardiac applications are of increasing interest. Therefore, the aim of our study was to assess right (RV) and left ventricular (LV) blood pool T1 and T2 values in patients with chronic thromboembolic pulmonary hypertension (CTEPH) compared to control subjects and their correlation to pulmonary hemodynamic. 26 patients with CTEPH (mean age 64.8 years ± 12.8 SD; 15 female), who underwent CMR and right heart catheterization (RHC) before and 6-months after balloon pulmonary angioplasty (BPA), were retrospectively included. Ventricular blood pool values were measured, compared to control subjects (mean age 40.5 years ± 12.8 SD; 16 female) and correlated to invasive measures (CI, mPAP, PVR). In both, control subjects and CTEPH patients, RVT1 and RVT2 were significantly reduced compared to LVT1 and LVT2. Compared to control subjects, RVT2 was significantly reduced in CTEPH patients (p = 0.0065) and increased significantly after BPA (p = 0.0048). Moreover, RVT2 was positively correlated with CI and negatively correlated with mPAP and PVR before (r = 0.5155, r = -0.2541, r = -0.4571) and after BPA (r = 0.4769, r = -0.2585, r = -0.4396). Ventricular blood pool T2 mapping might be novel non-invasive CMR imaging marker for assessment of disease severity, prognosis, follow-up and even therapy monitoring in PH.

MRI assessment of cerebral oxygen extraction fraction in the medial temporal lobe

The medial temporal lobe (MTL) is a key area implicated in many brain diseases, such as Alzheimer's disease. As a functional biomarker, the oxygen extraction fraction (OEF) of MTL may be more sensitive than structural atrophy of MTL, especially at the early stages of diseases. However, there is a lack of non-invasive techniques to measure MTL-OEF in humans. The goal of this work is to develop an MRI technique to assess MTL-OEF in a clinically practical time without using contrast agents. The proposed method measures venous oxygenation (Yv) in the basal veins of Rosenthal (BVs), which are the major draining veins of the MTL. MTL-OEF can then be estimated as the arterio-venous difference in oxygenation. We developed an MRI sequence, dubbed arterial-suppressed accelerated T2-relaxation-under-phase-contrast (AS-aTRUPC), to quantify the blood T2 of the BVs, which was then converted to Yv through a well-established calibration model. MTL-OEF was calculated as (Ya−Yv)/Ya × 100%, where Ya was the arterial oxygenation. The feasibility of AS-aTRUPC to quantify MTL-OEF was evaluated in 16 healthy adults. The sensitivity of AS-aTRUPC in detecting OEF changes was assessed by a caffeine ingestion (200 mg) challenge. For comparison, T2-relaxation-under-spin-tagging (TRUST) MRI, which is a widely used global OEF technique, was also acquired. The dependence of MTL-OEF on age was examined by including another seven healthy elderly subjects. The results showed that in healthy adults, MTL-OEF of the left and right hemispheres were correlated (P=0.005). MTL-OEF was measured to be 23.9±3.6% (mean±standard deviation) and was significantly lower (P<0.0001) than the OEF of 33.3±2.9% measured in superior sagittal sinus (SSS). After caffeine ingestion, there was an absolute percentage increase of 9.1±4.0% in MTL-OEF. Additionally, OEF in SSS measured with AS-aTRUPC showed a strong correlation with TRUST OEF (intra-class correlation coefficient=0.94 with 95% confidence interval [0.91, 0.96]), with no significant bias (P=0.12). MTL-OEF was found to increase with age (MTL-OEF=20.997+0.100 × age; P=0.02). In conclusion, AS-aTRUPC MRI provides non-invasive assessments of MTL-OEF and may facilitate future clinical applications of MTL-OEF as a disease biomarker.

Cerebral Oxygen Metabolism in Patients with Mild and Severe Sickle Cell Disease and Thalassemia

Introduction Studies in patients with severe (HbSS and HbSβ0) sickle cell disease (SCD) have reported reduced oxygen metabolism compared to controls despite the preserved oxygen delivery (OD). Whereas previous studies have found similar lesion load in mild SCD patients (HbSC and HbSβ+), oxygen metabolism has not been studied in this group. Interestingly, we previously showed that CBF values in mild SCD patients were lower compared to severe SCD, and comparable with healthy controls. Here, we assessed the OD, oxygen extraction fraction (OEF), cerebral metabolic rate of oxygen (CMRO2) and lesion volumes in adult patients with severe and mild SCD and compared our results with thalassemia patients as anemic controls and healthy controls. In addition, the effect of a vasodilatory stimulus on the cerebral parameters was studied to test if increased CBF influences oxygen consumption. Methods In this study, 75 patients with severe SCD (64 HbSS and 11 HbSβ0), 26 patients with mild SCD (16 HbSC and 10 HbSβ+), 17 patients with thalassemia (7 NTDT and 10 TDT) and 30 healthy controls were included. Venous blood T2 was measured using T2-Relaxation-Under-Spin-Tagging (TRUST). Whole brain (WB) CBF was measured using time-encoded pseudo-continuous ASL (te-ASL). TRUST and te-ASL scans were performed before and after acetazolamide (ACZ) administration as a vasodilatory stimulus. Fluid-Attenuated Inversion Recovery (FLAIR) scans were acquired for the assessment and segmentation of lesions. OEF was calculated from arterial saturation measured by pulse oximetry and venous saturation calculated from blood T2 using a sickle cell-specific calibration model and a healthy control model. CMRO2 was calculated from the WB CBF, OEF and oxygen content (calculated from hemoglobin and arterial saturation). To test the effect of ACZ-induced vasodilation, ∆CBF, ∆OD, ∆OEF and ∆CMRO2 were calculated. A one-way analysis of covariance (ANCOVA) was conducted (or a nonparametric alternative) with posthoc Bonferroni correction to test for statistically significant differences in cerebral parameters between the participating groups controlling for age and sex. For ∆CBF, ∆OD, ∆OEF and ∆CMRO2, baseline values were added as additional covariates. Results CBF was significantly higher in severe SCD compared to other groups and significantly higher in thalassemia patients compared to mild SCD and healthy controls (Table 1). No significant differences were found in OD between the groups. OEF was significantly lower in severe SCD patients compared to other groups and significantly lower in thalassemia patients compared to mild SCD patients and healthy controls (Table 1). CMRO2 was significantly lower in severe SCD and thalassemia patients compared to mild SCD patients and healthy controls (Table 1). ∆CBF upon ACZ administration was not significantly different between the groups. ∆OD was significantly higher in controls compared to severe SCD and thalassemia patients (Table 1). Infusion of ACZ impaired the OEF and CMRO2 more in severe SCD compared to the other groups (Table 1: ∆OEF and ∆CMRO2). Lesion volume was significantly larger in the severe SCD group compared to the healthy controls but no significant differences were found between the other groups (Fig. 1). Conclusion Our results show that OEF and CMRO2 were significantly higher in mild SCD patients, and no different from healthy controls, compared to severe SCD and thalassemia patients, illustrating a more balanced oxygen supply versus demand in these less anemic patients. Furthermore, the finding that ACZ-induced elevated CBF significantly reduced the CMRO2 in severe SCD, but not in the other groups, suggests that functional shunting may play a role in severely affected SCD patients. Despite the large differences in cerebral oxygen metabolism between severe and mild SCD, no difference in lesion volume could be observed between these groups. One possible mechanism that might be responsible for the lesion load in mild SCD patients could be the higher blood viscosity in this group that has been hypothesized to cause other complications such as retinopathy, particularly in patients with HbSC. Another explanation could be that lesion volume is more related to deep brain hypoxia than whole brain oxygen metabolism which could be confirmed by further studies investigating deep brain oxygenation. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Multiparametric renal magnetic resonance imaging: A reproducibility study in renal allografts with stable function.

Monitoring renal allograft function after transplantation is key for the early detection of allograft impairment, which in turn can contribute to preventing the loss of the allograft. Multiparametric renal MRI (mpMRI) is a promising noninvasive technique to assess and characterize renal physiopathology; however, few studies have employed mpMRI in renal allografts with stable function (maintained function over a long time period). The purposes of the current study were to evaluate the reproducibility of mpMRI in transplant patients and to characterize normal values of the measured parameters, and to estimate the labeling efficiency of Pseudo-Continuous Arterial Spin Labeling (PCASL) in the infrarenal aorta using numerical simulations considering experimental measurements of aortic blood flow profiles. The subjects were 20 transplant patients with stable kidney function, maintained over 1 year. The MRI protocol consisted of PCASL, intravoxel incoherent motion, and T1 inversion recovery. Phase contrast was used to measure aortic blood flow. Renal blood flow (RBF), diffusion coefficient (D), pseudo-diffusion coefficient (D*), flowing fraction ( ), and T1 maps were calculated and mean values were measured in the cortex and medulla. The labeling efficiency of PCASL was estimated from simulation of Bloch equations. Reproducibility was assessed with the within-subject coefficient of variation, intraclass correlation coefficient, and Bland-Altman analysis. Correlations were evaluated using the Pearson correlation coefficient. The significance level was p less than 0.05. Cortical reproducibility was very good for T1, D, and RBF, moderate for , and low for D*, while medullary reproducibility was good for T1 and D. Significant correlations in the cortex between RBF and (r = 0.66), RBF and eGFR (r = 0.64), and D* and eGFR (r = -0.57) were found. Normal values of the measured parameters employing the mpMRI protocol in kidney transplant patients with stable function were characterized and the results showed good reproducibility of the techniques.

Noncontrast time-resolved pulmonary magnetic resonance angiography with consecutive beam saturation pulse and variable flip angles using three-dimensional fast spin echo: A preliminary study

To develop and validate a novel noncontrast time-resolved magnetic resonance angiography (NC TR-MRA) using consecutive beam pulses with variable flip angles for visualizing hemodynamics in the pulmonary artery, we performed phantom and volunteer studies and applied the novel NC TR-MRA to a 51-year-old woman with pulmonary arteriovenous malformation (PAVM).The novel NC TR-MRA sequence utilized consecutive multiple-beam saturation pulses with variable flip angles considering venous blood T1 relaxation to alter the visualized blood signal length. The flowing blood signal length is suppressed according to the number of beam saturation pulses. NC TR-MRA in each flow phase was assessed by subtracting the images with and without beam saturation pulses. In the flow phantom study, three flow velocities were used to simulate physiological pulmonary arterial blood flow. Signal profiles along the flow direction were evaluated in each flow phase. In the volunteer study, five healthy volunteers were recruited, and NC TR-MRA was applied to evaluate relationships between the flow-saturated time and signal enhancement rates. Four regions of interest (ROIs) were determined on the proximal and distal portions of the right basal artery. A patient with PAVM was included to validate whether a PAVM lesion could be visualized using NC TR-MRA. The visualized flow signal lengths extended proportionally with the number of beam saturation pulses in the steady-flow phantom at all velocities. In the volunteer study, NC TR-MRA images showed signal enhancement from the proximal to distal portions of the right basal artery with increase in the flow-saturated time. Signal enhancement rates in all ROIs were significantly positively correlated with the flow-saturated time (p < 0.001 in all ROIs). Further, the lesion and its hemodynamics could be explicitly visualized in the patient with PAVM. Hence, NC TR-MRA using beam saturation pulse can visualize the hemodynamics of the pulmonary artery and may be useful for diagnosing and following patients with PAVM.