Parenchymal CSF fraction is a measure of brain glymphatic clearance and positively associated with amyloid beta deposition on PET.

INTRODUCTION: Mapping of microscopic changes in the perivascular space (PVS) of the cerebral cortex, beyond magnetic resonance-visible PVS in white matter, may enhance our ability to diagnose Alzheimer's disease (AD) early. METHODS: We used the cerebrospinal fluid (CSF) water fraction (CSFF), a magnetic resonance imaging-based biomarker, to characterize brain parenchymal CSF water, reflecting microscopic PVS in parenchyma. We measured CSFF and amyloid beta (Aß) using 11 C Pittsburgh compound B positron emission tomography to investigate their relationship at both the subject and voxel levels. RESULTS: Our research has demonstrated a positive correlation between the parenchymal CSFF, a non-invasive imaging biomarker indicative of parenchymal glymphatic clearance, and Aß deposition, observed at both individual and voxel-based assessments in the posterior cingulate cortex. DISCUSSION: This study shows that an increased parenchymal CSFF is associated with Aß deposition, suggesting that CSFF could serve as a biomarker for brain glymphatic clearance, which can be used to detect early fluid changes in PVS predisposing individuals to the development of AD. HIGHLIGHTS: Cerebrospinal fluid fraction (CSFF) could be a biomarker of parenchymal perivascular space. CSFF is positively associated with amyloid beta (Aß) deposition at subject level. CSFF in an Aß+ region is higher than in an Aß- region in the posterior cingulate cortex. Correspondence is found between Aß deposition and glymphatic clearance deficits measured by CSFF.

Probing muscle recovery following downhill running using precise mapping of MRI T2 relaxation times.

PURPOSE: Postexercise recovery rate is a vital component of designing personalized training protocols and rehabilitation plans. Tracking exercise-induced muscle damage and recovery requires sensitive tools that can probe the muscles' state and composition noninvasively. METHODS: Twenty-four physically active males completed a running protocol consisting of a 60-min downhill run on a treadmill at -10% incline and 65% of maximal heart rate. Quantitative mapping of MRI T2 was performed using the echo-modulation-curve algorithm before exercise, and at two time points: 1 h and 48 h after exercise. RESULTS: T2 values increased by 2%-4% following exercise in the primary mover muscles and exhibited further elevation of 1% after 48 h. For the antagonist muscles, T2 values increased only at the 48-h time point (2%-3%). Statistically significant decrease in the SD of T2 values was found following exercise for all tested muscles after 1 h (16%-21%), indicating a short-term decrease in the heterogeneity of the muscle tissue. CONCLUSION: MRI T2 relaxation time constitutes a useful quantitative marker for microstructural muscle damage, enabling region-specific identification for short-term and long-term systemic processes, and sensitive assessment of muscle recovery following exercise-induced muscle damage. The variability in T2 changes across different muscle groups can be attributed to their different role during downhill running, with immediate T2 elevation occurring in primary movers, followed by delayed elevation in both primary and antagonist muscle groups, presumably due to secondary damage caused by systemic processes.

Estimation of subvoxel fat infiltration in neurodegenerative muscle disorders using quantitative multi-T2 analysis.

MRI's T2 relaxation time is a valuable biomarker for neuromuscular disorders and muscle dystrophies. One of the hallmarks of these pathologies is the infiltration of adipose tissue and a loss of muscle volume. This leads to a mixture of two signal components, from fat and from water, to appear in each imaged voxel, each having a specific T2 relaxation time. In this proof-of-concept work, we present a technique that can separate the signals from water and from fat within each voxel, measure their separate T2 values, and calculate their relative fractions. The echo modulation curve (EMC) algorithm is a dictionary-based technique that offers accurate and reproducible mapping of T2 relaxation times. We present an extension of the EMC algorithm for estimating subvoxel fat and water fractions, alongside the T2 and proton-density values of each component. To facilitate data processing, calf and thigh anatomy were automatically segmented using a fully convolutional neural network and FSLeyes software. The preprocessing included creating two signal dictionaries, for water and for fat, using Bloch simulations of the prospective protocol. Postprocessing included voxelwise fitting for two components, by matching the experimental decay curve to a linear combination of the two simulated dictionaries. Subvoxel fat and water fractions and relaxation times were generated and used to calculate a new quantitative biomarker, termed viable muscle index, and reflecting disease severity. This biomarker indicates the fraction of remaining muscle out of the entire muscle region. The results were compared with those using the conventional Dixon technique, showing high agreement (R = 0.98, p < 0.001). It was concluded that the new extension of the EMC algorithm can be used to quantify abnormal fat infiltration as well as identify early inflammatory processes corresponding to elevation in the T2 value of the water (muscle) component. This new ability may improve the diagnostic accuracy of neuromuscular diseases, help stratification of patients according to disease severity, and offer an efficient tool for tracking disease progression.

Confined placental mosaicism: placental size and function evaluated on magnetic resonance imaging.

OBJECTIVES: Evidence regarding placental function in pregnancies complicated by confined placental mosaicism (CPM) is conflicting. We aimed to compare placental function between CPM and non-CPM pregnancies prenatally and at birth. A secondary objective was to evaluate the relationship between placental function and chromosomal subtype of CPM. METHODS: This was a retrospective study of pregnancies with CPM and control pregnancies delivered at a tertiary hospital in Denmark between 2014 and 2017. Placental volume and placental transverse relaxation time (T2*) were estimated on magnetic resonance imaging (MRI), fetal weight and uterine artery pulsatility index (UtA-PI) were estimated on ultrasound and fetoplacental ratio was assessed on MRI and at birth. These estimates of placental function were adjusted for gestational age and compared between groups using the Wilcoxon rank-sum test. Within the group of CPM pregnancies, measures of placental function were compared between those at high risk (chromosome numbers 2, 3, 7, 13 and 16) and those at low risk (chromosome numbers 5, 18 and 45X). RESULTS: A total of 90 pregnancies were included, of which 12 had CPM and 78 were controls. MRI and ultrasound examinations were performed at a median gestational age of 32.6 weeks (interquartile range, 24.7-35.3 weeks). On MRI assessment, CPM placentae were characterized by a lower placental T2* Z-score (P = 0.004), a lower fetoplacental ratio (P = 0.03) and a higher UtA-PI Z-score (P = 0.03), compared with non-CPM placentae. At birth, the fetoplacental ratio was significantly lower (P = 0.02) and placental weight Z-score was higher (P = 0.01) in CPM pregnancies compared with non-CPM pregnancies. High-risk CPM pregnancies showed a reduced placental T2* Z-score (P = 0.003), lower birth-weight Z-score (P = 0.041), earlier gestational age at delivery (P = 0.019) and higher UtA-PI Z-score (P = 0.028) compared with low-risk CPM pregnancies. Low-risk CPM pregnancies did not differ in any of these parameters from non-CPM pregnancies. CONCLUSIONS: CPM pregnancies are characterized by an enlarged and dysfunctional placenta. Placental function was highly related to the chromosomal type of CPM; placental dysfunction was seen predominantly in high-risk CPM pregnancies in which chromosomes 2, 3, 7, 13 or 16 were involved. © 2023 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Study of T2 mapping in quantifying and discriminating uterine lesions under different magnetic field strengths: 1.5 T vs. 3.0 T.

BACKGROUND: MRI is the best imaging tool for the evaluation of uterine tumors, but conventional MRI diagnosis results rely on radiologists and contrast agents (if needed). As a new objective, reproducible and contrast-agent free quantification technique, T2 mapping has been applied to a number of diseases, but studies on the evaluation of uterine lesions and the influence of magnetic field strength are few. Therefore, the aim of this study was to systematically investigate and compare the performance of T2 mapping as a nonenhanced imaging tool in discriminating common uterine lesions between 1.5 T and 3.0 T MRI systems. METHODS: A total of 50 healthy subjects and 126 patients with suspected uterine lesions were enrolled in our study, and routine uterine MRI sequences with additional T2 mapping sequences were performed. T2 maps were calculated by monoexponential fitting using a custom code in MATLAB. T2 values of normal uterine structures in the healthy group and lesions (benign: adenomyosis, myoma, endometrial polyps; malignant: cervical cancer, endometrial carcinoma) in the patient group were collected. The differences in T2 values between 1.5 T MRI and 3.0 T MRI in any normal structure or lesion were compared. The comparison of T2 values between benign and malignant lesions was also performed under each magnetic field strength, and the diagnostic efficacies of the T2 value obtained through receiver operating characteristic (ROC) analysis were compared between 1.5 T and 3.0 T. RESULTS: The mean T2 value of any normal uterine structure or uterine lesion under 3.0 T MRI was significantly lower than that under 1.5 T MRI (p < 0.05). There were significant differences in T2 values between each lesion subgroup under both 1.5 T and 3.0 T MRI. Moreover, the T2 values of benign lesions (71.1 ± 22.0 ms at 1.5 T and 63.4 ± 19.1 ms at 3.0 T) were also significantly lower than those of malignant lesions (101.1 ± 4.5 ms at 1.5 T and 93.5 ± 5.1 ms at 3.0 T) under both field strengths. In the aspect of differentiating benign from malignant lesions, the area under the curve of the T2 value under 3.0 T (0.94) was significantly higher than that under 1.5 T MRI (0.90) (p = 0.02). CONCLUSION: T2 mapping can be a potential tool for quantifying common uterine lesions, and it has better performance in distinguishing benign from malignant lesions under 3.0 T MRI.

Optimized Unilateral Magnetic Resonance Sensor with Constant Gradient and Its Applications in Composite Insulators.

In this study, an optimized unilateral magnetic resonance sensor with a three-magnet array is presented for assessing the aging of composite insulators in power grids. The sensor's optimization involved enhancing the static magnetic field strength and the homogeneity of the RF field while maintaining a constant gradient in the direction of the vertical sensor surface and maximizing homogeneity in the horizontal direction. The center layer of the target area was positioned 4 mm from the coil's upper surface, resulting in a magnetic field strength of 139.74 mT at the center point of the area, with a gradient of 2.318 T/m and a corresponding hydrogen atomic nuclear magnetic resonance frequency of 5.95 MHz. The magnetic field uniformity over a 10 mm × 10 mm range on the plane was 0.75%. The sensor measured 120 mm × 130.5 mm × 76 mm and weighed 7.5 kg. Employing the optimized sensor, magnetic resonance assessment experiments were conducted on composite insulator samples utilizing the CPMG (Carr-Purcell-Meiboom-Gill) pulse sequence. The T2 distribution provided visualizations of the T2 decay in insulator samples with different degrees of aging.

Placental transverse relaxation time (T2) estimated by MRI: Normal values and the correlation with birthweight.

INTRODUCTION: Placental transverse relaxation time (T2) assessed by MRI may have the potential to improve the antenatal identification of small for gestational age. The aims of this study were to provide normal values of placental T2 in relation to gestational age at the time of MRI and to explore the correlation between placental T2 and birthweight. MATERIAL AND METHODS: A mixed cohort of 112 singleton pregnancies was retrieved from our placental MRI research database. MRI was performed at 23.6-41.3 weeks of gestation in a 1.5T system (TE (8): 50-440 ms, TR: 4000 ms). Normal pregnancies were defined by uncomplicated pregnancies with normal obstetric outcome and birthweight deviation within ±1 SD of the expected for gestational age. The correlation between placental T2 and birthweight was investigated using the following outcomes; small for gestational age (birthweight ≤-2 SD of the expected for gestational age) and birthweight deviation (birthweight Z-scores). RESULTS: In normal pregnancies (n = 27), placenta T2 showed a significant negative linear correlation with gestational age (r = -.91, P = .0001) being 184 ms ± 15.94 ms (mean ± SD) at 20 weeks of gestation and 89 ms ± 15.94 ms at 40 weeks of gestation. Placental T2 was significantly reduced among small-for-gestational-age pregnancies (mean Z-score -1.95, P < .001). Moreover, we found a significant positive correlation between placenta T2 deviation (Z-score) and birthweight deviation (Z-score) (R2  = .26, P = .0001). CONCLUSIONS: This study provides normal values of placental T2 to be used in future studies on placental MRI. Placental T2 is closely related to birthweight and may improve the antenatal identification of small-for-gestational-age pregnancies.

The utility of MRI for measuring hematocrit in fetal anemia.

BACKGROUND: Doppler ultrasound measurements of the peak systolic velocity of the middle cerebral artery can be used to noninvasively diagnose fetal anemia but are less precise following fetal blood transfusion and in late gestation. We have previously demonstrated the feasibility of estimating fetal hematocrit in vitro using magnetic resonance imaging relaxation times. Here we report the use of magnetic resonance imaging as a noninvasive tool to accurately detect fetal anemia in vivo. OBJECTIVES: This study has 2 objectives: (1) to determine the feasibility and accuracy of magnetic resonance imaging in estimating hematocrit in anemic fetuses and (2) to compare magnetic resonance imaging and middle cerebral artery Doppler in detecting moderate to severe fetal anemia. STUDY DESIGN: Fetuses undergoing fetal blood sampling or transfusion underwent magnetic resonance imaging examinations prior to and following their procedures at 1.5 Tesla (Siemens Avanto). A modified Look-Locker inversion pulse sequence and T2 preparation sequence were applied for T1 and T2 mapping of the intrahepatic umbilical vein. Estimated fetal hematocrit was calculated using a combination of T1 and T2 values and compared with conventional hematocrit obtained from fetal blood samples and middle cerebral artery Doppler measurements. RESULTS: Twenty-three fetuses were assessed during 33 magnetic resonance imaging scans. The mean absolute difference between the laboratory and magnetic resonance imaging-estimated hematocrit was 0.06 ± 0.05 with a correlation of 0.77 (P < .001) determined by a multilevel, mixed-effects model adjusting for the repeated measurements from the same participants, multiple gestation pregnancies, and the scan type (ie, before or after transfusion scan). Bland-Altman analysis revealed a systematic bias of -0.03 between the magnetic resonance imaging and fetal blood sampling measurements. Magnetic resonance imaging and middle cerebral artery Doppler had similar sensitivities of approximately 90% to detect moderate to severe anemia. However, magnetic resonance imaging had a higher specificity (93% [13/14], 95% confidence interval, 66-100%) than Doppler (71% [10/14], 95% confidence interval, 42-92%). CONCLUSION: Moderate to severe fetal anemia can be detected noninvasively by magnetic resonance imaging with high sensitivity and specificity. Our results suggest an adjunct role for magnetic resonance imaging in fetuses with suspected anemia, particularly following previous transfusion and in late gestation.

Detection of muscle activity with forearm pronation exercise using T2-map MRI.

[Purpose] We aimed to detect muscle activity during a forearm pronation exercise using a 0.2 T MRI system. [Participants and Methods] We recruited healthy adult volunteers (7 males, 4 females). Transverse relaxation time (T2) values for 10 forearm muscles were obtained from transverse multiple-spin-echo MR images of one-third of the ulna, lengthwise from the olecranon, in the resting state and after isotonic forearm pronation exercise at three strength levels (5, 15, and 25% of the maximum voluntary contraction). Z values were calculated as (T2e - T2r)/SDr, where T2e, T2r and SDr were T2 after exercise, 34 ms, and 3 ms, respectively. A Z value of 2.56 was used as the threshold for defining muscle activation. [Results] T2 values increased significantly in the pronator teres muscle (agonist), while those in the supinator muscle (antagonist) showed no change. The sensitivity and specificity values obtained were high and low, respectively, for all of the three exercise strength levels employed. In some of the participants, activity was detected in the flexor carpi radialis, extensor carpi ulnaris, and extensor digitorum. [Conclusion] Using T2-map MRI, we detected activity in primary and secondary mover muscles. We also found individual variations in the use of forearm muscles during pronation.

Radiographically normal knees with contralateral joint space narrowing display greater change in cartilage transverse relaxation time than those with normal contralateral knees: a model of early OA? - data from the Osteoarthritis Initiative (OAI).

OBJECTIVE: To develop a model of early osteoarthritis, by examining whether radiographically normal knees with contralateral joint space narrowing (JSN), but without contralateral trauma history, display greater longitudinal cartilage composition change (transverse relaxation time; T2) than subjects with bilaterally normal knees. METHODS: 120 radiographically normal knees (Kellgren Lawrence grade [KLG] 0) from the Osteoarthritis Initiative were studied. 60 case knees displayed definite contralateral radiographic knee osteoarthritis (KLG ≥ 2) whereas 60 reference subjects were bilaterally KLG0, and were matched 1:1 to cases based on age, sex, and BMI. All had multi-echo spin-echo MRI acquired at year (Y) 1 and 4 follow-up, with cartilage T2 being determined in superficial and deep cartilage layers across 16 femorotibial subregions. T2 across all regions was considered the primary analytic focus. RESULTS: Of 60 KLG0 case knees (30 female, age: 65.0 ± 8.8 y, BMI: 27.6 ± 4.4 kg/m2), 21/22/13/4 displayed contralateral JSN 0/1/2/3, respectively. The longitudinal increase in the deep layer cartilage T2 between Y1 and Y4 was significantly greater (P = 0.03; Cohen's D 0.50) in the 39 KLG0 case knees with contralateral JSN (1.2 ms; 95% confidence interval [CI] [0.4, 2.0]) than in matched KLG0 reference knees (0.1 ms; 95% CI [-0.5, 0.7]). No significant differences were identified in superficial T2 change. T2 at Y1 was significantly greater in case than in reference knees, particularly in the superficial layer of the medial compartment. CONCLUSIONS: Radiographically normal knees with contralateral, non-traumatic JSN represent an applicable model of early osteoarthritis, with deep layer cartilage composition (T2) changing more rapidly than in bilaterally normal knees. CLINICALTRIALS. GOV IDENTIFICATION: NCT00080171.

Shortening of apparent transverse relaxation time of inorganic phosphate as a breast cancer biomarker.

Phosphorus MRS offers a non-invasive tool for monitoring cell energy and phospholipid metabolism and can be of additional value in diagnosing cancer and monitoring cancer therapy. In this study, we determined the transverse relaxation times of a number of phosphorous metabolites in a group of breast cancer patients by adiabatic multi-echo spectroscopic imaging at 7 T. The transverse relaxation times of phosphoethanolamine, phosphocholine, inorganic phosphate (Pi ), glycerophosphocholine and glycerophosphatidylcholine were 184 ± 8 ms, 203 ± 17 ms, 87 ± 8 ms, 240 ± 56 ms and 20 ± 10 ms, respectively. The transverse relaxation time of Pi in breast cancer tissue was less than half that of healthy fibroglandular tissue. This effect is most likely caused by an up-regulation of glycolysis in breast cancer tissue that leads to interaction of Pi with the GAPDH enzyme, which forms part of the reversible pathway of exchange of Pi with gamma-adenosine tri-phosphate, thus shortening its apparent transverse relaxation time. As healthy breast tissue shows very little glycolytic activity, the apparent T2 shortening of Pi due to malignant transformation could possibly be used as a biomarker for cancer.

In vivo measurement of T1 and T2 relaxation times in awake pigeon and rat brains at 7T.

PURPOSE: Establishment of regional longitudinal (T1 ) and transverse (T2 ) relaxation times in awake pigeons and rats at 7T field strength. Regional differences in relaxation times between species and between two different pigeon breeds (homing pigeons and Figurita pigeons) were investigated. METHODS: T1 and T2 relaxation times were determined for nine functionally equivalent brain regions in awake pigeons and rats using a multiple spin-echo saturation recovery method with variable repetition time and a multi-slice/multi-echo sequence, respectively. Optimized head fixation and habituation protocols were applied to accustom animals to the scanning conditions and to minimize movement. RESULTS: The habituation protocol successfully limited movement of the awake animals to a negligible minimum, allowing reliable measurement of T1 and T2 values within all regions of interest. Significant differences in relaxation times were found between rats and pigeons but not between different pigeon breeds. CONCLUSION: The obtained T1 and T2 values for awake pigeons and rats and the optimized habituation protocol will augment future MRI studies with awake animals. The differences in relaxation times observed between species underline the importance of the acquisition of T1 /T2 values as reference points for specific experiments. Magn Reson Med 79:1090-1100, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

Quantitative in vivo T2 mapping using fast spin echo techniques - A linear correction procedure.

A method is presented for correcting the effects of stimulated and indirect echoes on quantitative T2 mapping data acquired with multiple spin echo techniques, such as turbo spin echo. In contrast to similar correction techniques proposed in the literature, the method does not require a priori knowledge of the radio frequency (RF) pulse profiles. In a first step, for the T2 mapping protocol under investigation, signal decay curves S(TE) are simulated for a range of different RF pulse profiles. The actual signal decay S(TE) is then measured on a phantom with known T2, so the approximate RF pulse profiles can be derived via comparison with the simulated decay curves. In a second step, with the RF pulses obtained from step one, signal decay curves S(TE) are simulated for different T2 values and fitted mono-exponentially, thus allowing to deduce the relationship between true T2 and the apparent T2 (T2app) values. Results show that this relationship is approximately linear, allowing for a direct correction of T2app maps. If the amplitude of the transmitted RF field (B1) does not exceed the nominal value by more than 10%, it is shown that a B1-independent correction of T2app maps yields sufficiently accurate results for T2. A B1-dependent version is also presented. The method is tested in vitro on a phantom with different T2 values and in vivo on healthy subjects.

Water T2 as an early, global and practical biomarker for metabolic syndrome: an observational cross-sectional study.

BACKGROUND: Metabolic syndrome (MetS) is a highly prevalent condition that identifies individuals at risk for type 2 diabetes mellitus and atherosclerotic cardiovascular disease. Prevention of these diseases relies on early detection and intervention in order to preserve pancreatic ß-cells and arterial wall integrity. Yet, the clinical criteria for MetS are insensitive to the early-stage insulin resistance, inflammation, cholesterol and clotting factor abnormalities that characterize the progression toward type 2 diabetes and atherosclerosis. Here we report the discovery and initial characterization of an atypical new biomarker that detects these early conditions with just one measurement. METHODS: Water T2, measured in a few minutes using benchtop nuclear magnetic resonance relaxometry, is exquisitely sensitive to metabolic shifts in the blood proteome. In an observational cross-sectional study of 72 non-diabetic human subjects, the association of plasma and serum water T2 values with over 130 blood biomarkers was analyzed using bivariate, multivariate and logistic regression. RESULTS: Plasma and serum water T2 exhibited strong bivariate correlations with markers of insulin, lipids, inflammation, coagulation and electrolyte balance. After correcting for confounders, low water T2 values were independently and additively associated with fasting hyperinsulinemia, dyslipidemia and subclinical inflammation. Plasma water T2 exhibited 100% sensitivity and 87% specificity for detecting early insulin resistance in normoglycemic subjects, as defined by the McAuley Index. Sixteen normoglycemic subjects with early metabolic abnormalities (22% of the study population) were identified by low water T2 values. Thirteen of the 16 did not meet the harmonized clinical criteria for metabolic syndrome and would have been missed by conventional screening for diabetes risk. Low water T2 values were associated with increases in the mean concentrations of 6 of the 16 most abundant acute phase proteins and lipoproteins in plasma. CONCLUSIONS: Water T2 detects a constellation of early abnormalities associated with metabolic syndrome, providing a global view of an individual's metabolic health. It circumvents the pitfalls associated with fasting glucose and hemoglobin A1c and the limitations of the current clinical criteria for metabolic syndrome. Water T2 shows promise as an early, global and practical screening tool for the identification of individuals at risk for diabetes and atherosclerosis.

Relaxation properties of human umbilical cord blood at 1.5 Tesla.

PURPOSE: To characterize the MRI relaxation properties of human umbilical cord blood at 1.5 Tesla. METHODS: Relaxometry measurements were performed on cord blood specimens (N = 88, derived from six caesarean deliveries) spanning a broad range of hematocrits (Hct = 0.19-0.76) and oxygen saturations (sO2 = 4-100%), to characterize the dependence of T1 and T2 on these blood properties. Adult blood data (N = 31 specimens, derived from two volunteers) were similarly studied to validate our experimental methods by comparison with existing literature. Using biophysical models previously developed for adult blood, new model parameters were estimated, which relate Hct and sO2 to the observed cord blood relaxation times. RESULTS: Fitted biophysical models explained more than 90% of the variation in T1 and T2 . In general, T2 relaxation times of cord blood were longer (by up to 35%) than those of adult blood, whereas T1 relaxation times were slightly shorter (by up to 10%). CONCLUSIONS: The models and fitted parameters presented here can be used for calibration of future MRI investigations of fetal and neonatal blood physiology. This study is an important step in facilitating accurate, noninvasive assessments of fetal blood oxygen content, a valuable diagnostic parameter in the identification and treatment of fetal hypoxia. Magn Reson Med 77:1678-1690, 2017. © 2016 International Society for Magnetic Resonance in Medicine.

Proton and phosphorus magnetic resonance spectroscopy of the healthy human breast at 7 T.

In vivo water- and fat-suppressed 1 H magnetic resonance spectroscopy (MRS) and 31 P magnetic resonance adiabatic multi-echo spectroscopic imaging were performed at 7 T in duplicate in healthy fibroglandular breast tissue of a group of eight volunteers. The transverse relaxation times of 31 P metabolites were determined, and the reproducibility of 1 H and 31 P MRS was investigated. The transverse relaxation times for phosphoethanolamine (PE) and phosphocholine (PC) were fitted bi-exponentially, with an added short T2 component of 20 ms for adenosine monophosphate, resulting in values of 199 ± 8 and 239 ± 14 ms, respectively. The transverse relaxation time for glycerophosphocholine (GPC) was also fitted bi-exponentially, with an added short T2 component of 20 ms for glycerophosphatidylethanolamine, which resonates at a similar frequency, resulting in a value of 177 ± 6 ms. Transverse relaxation times for inorganic phosphate, γ-ATP and glycerophosphatidylcholine mobile phospholipid were fitted mono-exponentially, resulting in values of 180 ± 4, 19 ± 3 and 20 ± 4 ms, respectively. Coefficients of variation for the duplicate determinations of 1 H total choline (tChol) and the 31 P metabolites were calculated for the group of volunteers. The reproducibility of inorganic phosphate, the sum of phosphomonoesters and the sum of phosphodiesters with 31 P MRS imaging was superior to the reproducibility of 1 H MRS for tChol. 1 H and 31 P data were combined to calculate estimates of the absolute concentrations of PC, GPC and PE in healthy fibroglandular tissue, resulting in upper limits of 0.1, 0.1 and 0.2 mmol/kg of tissue, respectively.

[Analyze moisture transformation and transport rules during processing of Paeoniae Radix Alba by using low-field NMR].

Moisture status and content during the processing of Paeoniae Radix Alba were studied by nuclear magnetic resonance (NMR) and nuclear magnetic resonance imaging (MRI) to investigate the changes of transverse relaxation time (T 2) and MRI images during boiling and drying processes of Paeoniae Radix Alba. The results showed that water in Paeoniae Radix Alba fresh products was major of free water, and in the boiling process, the content of free water increased whereas the content of bound water declined. At the end of boiling, content of free water reached over 90%. During the drying process, T 2 moved to the left, and moisture mobility was reduced. The MRI image directly showed that moisture transfer was outside-in process for both increase and decrease. At the end of drying, remaining moisture was mainly present in inner layer of Paeoniae Radix Alba. Quality and appearance were affected by the change of moisture during processing process of medicinal herbs. NMR and MRI could provide direct reference evidence for its moisture changes, and the results of this study could provide direct references and technical support for optimization of processing process of root medicinal materials and evaluation of Chinese herbal pieces.

Changes in T2-weighted MRI of supinator muscle, pronator teres muscle, and extensor indicis muscle with manual muscle testing.

[Purpose] In order to detect muscle activity with manual muscle testing, T2-weighted magnetic resonance (T2w-MR) images were detected by a 0.2 T compact MRI system. [Subjects and Methods] The subjects were 3 adult males. Transverse T2-weighted multi-slice spin-echo images of the left forearm were measured by a 39 ms echo-time with a 2,000 ms repetition time, a 9.5 mm slice thickness, 1 accumulation and a total image acquisition time of 4 min 16 s. First, T2w-MR images in the resting condition were measured. Then, manipulative isometric contraction exercise (5 sec duration) to the supinator muscle, the pronator teres muscle or the extensor indicis muscle was performed using Borg's rating of perceived exertion (RPE) scale of 15-17. The T2w-MR images were measured immediately after the exercise. [Results] T2w-MR image intensities increased significantly in the supinator muscle, the pronator teres muscle and the extensor indicis muscle after the exercise. However, the image intensities in the rest of the muscle did not change. [Conclusion] Using T2w-MR images, we could detect muscle activity in a deep muscle, the supinator muscle, and a small muscle, the extensor indicis muscle. These results also support the reliability of the manual muscle testing method.

T1 and T2 values of human neonatal blood at 3 Tesla: Dependence on hematocrit, oxygenation, and temperature.

PURPOSE: Knowledge of blood T1 and T2 is of major importance in many applications of MRI in neonates. However, to date, there has not been a systematic study to examine neonatal blood T1/T2 relaxometry. This present study aims to investigate this topic. METHODS: Using freshly collected blood samples from human umbilical cord, we performed in vitro experiments under controlled physiological conditions to measure blood T1 and T2 at 3 Tesla (T) and their dependence on several factors, including hematocrit (Hct), oxygenation (Y) and temperature. RESULTS: The arterial T1 in neonates was 1825 ± 184 ms (Hct = 0.42 ± 0.08), longer than that of adult blood. Neonatal blood T1 was strongly dependent on Hct (P < 0.001) and Y (P = 0.005), and the dependence of T1 on Y was more prominent at higher Hct. The arterial T2 of neonatal blood was 191 ms at an Hct of 0.42, which was also longer than adult blood. Neonatal blood T2 was positively associated with blood oxygenation and negatively associated with hematocrit level, and can be characterized by an exchange model. Neonatal blood T1 was also positively associated with temperature (P < 0.001). CONCLUSION: The values provided in this report may provide important reference and calibration information for sequence optimization and quantification of in vivo neonatal MRI studies.

Placental magnetic resonance imaging T2* measurements in normal pregnancies and in those complicated by fetal growth restriction.

OBJECTIVES: The magnetic resonance imaging (MRI) variable transverse relaxation time (T2*) depends on multiple factors, one important one being the presence of deoxyhemoglobin. We aimed to describe placental T2* measurements in normal pregnancies and in those with fetal growth restriction (FGR). METHODS: We included 24 normal pregnancies at 24-40 weeks' gestation and four FGR cases with an estimated fetal weight below the 1(st) centile. Prior to MRI, an ultrasound examination, including Doppler flow measurements, was performed. The T2* value was calculated using a gradient echo MRI sequence with readout at 16 different echo times. In normal pregnancies, repeat T2* measurements were performed and interobserver reproducibility was assessed in order to estimate the reproducibility of the method. Placental histological examination was performed in the FGR cases. RESULTS: The method was robust regarding the technical and interobserver reproducibility. However, some slice-to-slice variation existed owing to the heterogeneous nature of the normal placenta. We therefore based T2* estimations on the average of two slices from each placenta. In normal pregnancies, the placental T2* value decreased significantly with increasing gestational age, with mean ± SD values of 120 ± 17 ms at 24 weeks' gestation, 84 ± 16 ms at 32 weeks and 47 ± 17 ms at 40 weeks. Three FGR cases had abnormal Doppler flow, histological signs of maternal hypoperfusion and a reduced T2* value (Z-score < -3.5). In the fourth FGR case, Doppler flow, placental histology and T2* value (Z-score, -0.34) were normal. CONCLUSIONS: The established reference values for placental T2* may be clinically useful, as T2* values were significantly lower in FGR cases with histological signs of maternal hypoperfusion. Copyright © 2015 ISUOG. Published by John Wiley & Sons Ltd.