T2* weighted fetal MRI and the correlation with placental dysfunction.

INTRODUCTION: Transverse relaxation time (T2*) is related to tissue oxygenation and morphology. We aimed to describe T2* weighted MRI in selected fetal organs in normal pregnancies, and to investigate the correlation between fetal organ T2* and placental T2*, birthweight (BW) deviation, and redistribution of fetal blood flow. METHODS: T2*-weighted MRI was performed in 126 singleton pregnancies between 23+6- and 41+3-weeks' gestation. The T2* value was obtained from the placenta and fetal organs (brain, lungs, heart, liver, kidneys, and spleen). In normal BW pregnancies (BW > 10th centile), the correlation between the T2* value and gestational age (GA) at MRI was estimated by linear regression. The correlation between fetal organ Z-score and BW group was demonstrated by boxplots and investigated by analysis of variance (ANOVA) for each organ. RESULTS: In normal BW pregnancies fetal organ T2* was negatively correlated with GA. We found a significant correlation between BW group and fetal organ T2* z-score in the fetal heart, kidney, lung and spleen. A positive linear correlation was demonstrated between fetal organ T2* and outcomes related to placental function such as BW deviation and placenta T2* in all investigated fetal organs except for the fetal liver. In the fetal heart, kidneys, and spleen the T2* value showed a significant correlation with fetal redistribution of blood flow (Middle cerebral artery Pulsatility Index) before delivery. DISCUSSION: Fetal T2* is correlated with BW, placental function, and redistribution of fetal blood flow, suggesting that fetal organ T2* reflects fetal oxygenation and morphological changes related to placental dysfunction.

Biomechanical Properties of Strictures in Crohn's Disease: Can Dynamic Contrast-Enhanced Ultrasonography and Magnetic Resonance Enterography Predict Stiffness?

Strictures and abdominal pain often complicate Crohn's disease (CD). The primary aim was to explore whether parameters obtained by preoperative contrast-enhanced (CE) ultrasonography (US) and dynamic CE MR Enterography (DCE-MRE) of strictures associates with biomechanical properties. CD patients undergoing elective small intestinal surgery were preoperatively examined with DCE-MRE and CEUS. The excised intestine was distended utilizing a pressure bag. Luminal and outer bowel wall cross-sectional areas were measured with US. The circumferential stricture stiffness (Young's modulus E) was computed. Stiffness was associated with the initial slope of enhancement on DCE-MRE (ρ = 0.63, p = 0.007), reflecting active disease, but lacked association with CEUS parameters. For structural imaging parameters, inflammation and stricture stiffness were associated with prestenotic dilatation on US (τb = 0.43, p = 0.02) but not with MRE (τb = 0.01, p = 1.0). Strictures identified by US were stiffer, 16.8 (14.0-20.1) kPa, than those graded as no or uncertain strictures, 12.6 (10.5-15.1) kPa, p = 0.02. MRE global score (activity) was associated with E (ρ = 0.55, p = 0.018). Elastography did not correlate with circumferential stiffness. We conclude that increasing activity defined by the initial slope of enhancement on DCE-MRE and MRE global score were associated with stricture stiffness. Prestenotic dilatation on US could be a potential biomarker of CD small intestinal stricture stiffness.

T2*-weighted placental magnetic resonance imaging: a biomarker of placental dysfunction in small-for-gestational-age pregnancies.

BACKGROUND: The antenatal identification of placental dysfunction in small-for-gestational-age fetuses with normal fetal Doppler flows remains an obstetrical challenge. In a significant fraction of such pregnancies, placental dysfunction is revealed by clinical manifestations such as preeclampsia, preterm delivery, or severe small-for-gestational-age at birth or by abnormal findings in the postnatal placental histologic examination. Therefore, new methods to identify placental function directly in pregnancy at the time of small-for-gestational-age diagnosis is highly needed. T2*-weighted placental magnetic resonance imaging is sensitive to changes in placental morphology and oxygenation and is thereby related to placental function. Previous studies have demonstrated that pregnancies complicated by low birthweight and preeclampsia are characterized by low placental T2* values. However, the specific performance of placental T2* in the prediction of placenta-related outcomes in small-for-gestational-age pregnancies with normal fetal Doppler flows remains to be explored. OBJECTIVE: In small-for-gestational-age pregnancies with normal fetal Doppler flows, we aimed to evaluate T2*-weighted placental magnetic resonance imaging as an antenatal biomarker of placental dysfunction. In addition, we aimed to investigate the correlation between placental T2* and Doppler flow measurements of fetal and uterine arteries at the time of magnetic resonance imaging. STUDY DESIGN: In this prospective cohort study, the inclusion criterion was suspected small-for-gestational-age (ultrasound estimated fetal weight Z-score ≤-2.0 [2.3rd centile]) with normal fetal Doppler flows (middle cerebral artery pulsatility index Z-score > -2.0 and umbilical artery pulsatility index Z-score <2.0). The T2*-weighted placental magnetic resonance imaging scan was performed at inclusion in a 1.5 T system. The outcomes was placental dysfunction at birth defined by low birthweight (Z-score ≤-2.0), preeclampsia, preterm delivery (gestational age<37 weeks), or abnormal placental histologic examination such as placental vascular malperfusion according to the Amsterdam Consensus Statement. RESULTS: We included 92 pregnancies at 26+5 to 39+6 weeks gestation. The median time interval between the magnetic resonance imaging scan and birth was 4.6 weeks (interquartile range, 2.7-7.8 weeks). At birth, 55% (51/92) of pregnancies revealed at least 1 sign of placental dysfunction; 49% (40/81) had abnormal placental histologic examination, 29% (27/92) were born with low birthweight, 13% (12/92) were delivered preterm, and 7% (6/92) had preeclampsia. When adjusted for gestational age at magnetic resonance imaging, the placental T2* Z-score was a significant predictor of abnormal placental histologic examination (area under the curve, 0.73; P=.001), small-for-gestational-age at birth (area under the curve, 0.63; P=.030), preeclampsia (area under the curve, 0.88; P=.005), and preterm delivery (area under the curve, 0.81; P=.001). The placental T2* was reduced in pregnancies with a combination of clinical manifestations and abnormal placental histologic examination (T2* Z-score=-1.52±1.35 [mean±standard deviation]; P=.0001) and in clinically uneventful pregnancies with abnormal placental histologic examination (T2* Z-score=-0.79±0.97; P=.045). At the time of magnetic resonance imaging, the placental T2* Z-score showed a significant linear correlation with the uterine artery pulsatility index Z-scores (r=-0.24; P=.016) and the middle cerebral artery pulsatility index Z-scores (r=0.29; P=.017) but not with the umbilical artery pulsatility index Z-scores (r=0.18; P=.17) and the cerebroplacental ratio (r=0.03; P=.77). CONCLUSION: This study indicates that placental dysfunction is frequent in small-for-gestational-age fetuses with normal fetal Doppler flows. In this cohort, T2*-weighted placental magnetic resonance imaging is a sensitive biomarker of placental dysfunction regardless of the clinical manifestations. This finding supports a paradigm shift in the conception of placental dysfunction that may cover a wide spectrum of clinical and subclinical manifestations.

Perfusion fraction derived from IVIM analysis of diffusion-weighted MRI in the assessment of placental vascular malperfusion antenatally.

INTRODUCTION: Specific placental pathologies that may impact fetal development, such as vascular malperfusion, are diagnosed postpartum. We aimed to evaluate if placental perfusion fraction (f) derived from intravoxel incoherent motion (IVIM) analysis of diffusion-weighted magnetic resonance imaging (DWI) can be used to identify specific types of placental vascular malperfusion antenatally. METHOD: 93 women who underwent placental DWI with multiple b-values at 23.9-41.3 week's gestation and postpartum histological examination were identified in the local placental MRI research database. Based on the placental examination, 44 were defined as normal controls and 49 cases had placental vascular malperfusion. Vascular malperfusion was subdivided into fetal vascular malperfusion (n = 13), maternal vascular malperfusion (n = 30) or both (n = 6). For each placenta, regions of interest were drawn on three placental slices and their mean f was estimated using intravoxel incoherence motion analysis. RESULTS: In normal placentas mean f was 26.0 ± 4.6% (mean ± SD) and no linear correlation between f and gestational age was found, r = -0.05, p = 0.72. Placentas with fetal vascular malperfusion showed a significantly lower f (22.7 ± 4.4%) compared to normal controls, p = 0.03. In cases of maternal vascular malperfusion (25.2 ± 6.4%), no significant difference in f was revealed, p = 0.55. CONCLUSIONS: These results indicate that placental DWI-derived f may identify fetal vascular malperfusion in vivo. This study confirms a previous pilot study and provides initial evidence that fetal and maternal vascular malperfusion have different MRI signatures. Future studies are needed to further explore the clinical significance of this interesting finding.

Placental MRI: Longitudinal relaxation time (T1) in appropriate and small for gestational age pregnancies.

OBJECTIVE: The antenatal detection of small for gestational age (SGA) pregnancies is a challenge, which may be improved by placental MRI. The longitudinal relaxation time (T1) is a tissue constant related to tissue morphology and tissue oxygenation, thereby placental T1 may be related to placental function. The aim of this study is to investigate placental T1 in appropriate for gestational age (AGA) and SGA pregnancies. METHODS: A total of 132 singleton pregnancies were retrieved from our MRI research database. MRI and ultrasound estimated fetal weight (EFW) was performed at gestational week 20.6-41.7 in a 1.5 T system. SGA was defined as BW ≤ -15% of the expected for gestational age (≤10th centile). A subgroup of SGA pregnancies underwent postnatal placental histological examination (PHE) and abnormal PHE was defined as vascular malperfusion. The placental T1 values were converted into Z-scores adjusted for gestational age at MRI. The predictive performance of placental T1 and EFW was compared by receiver operating curves (ROC). RESULTS: In AGA pregnancies, placental T1 showed a negative linear correlation with gestational age (r = -0.36, p = 0.004) Placental T1 was significantly reduced in SGA pregnancies (mean Z-score = -0.34) when compared to AGA pregnancies, p = 0.03. Among SGA pregnancies placental T1 was not reduced in cases with abnormal PHE, p = 0.84. The predictive performance of EFW (AUC = 0.84, 95% CI, 0.77-0.91) was significantly stronger than placental T1 (AUC = 0.62, 95% CI, 0.52-0.72) (p = 0.002). DISCUSSION: A low placental T1 relaxation time is associated with SGA at birth. However, the predictive performance of placental T1 is not as strong as EFW.

T2* weighted placental MRI in relation to placental histology and birth weight.

INTRODUCTION: Placental dysfunction may be found among normal birth weight (BW) pregnancies, as indicated by abnormal histological findings in postnatal placental examination in some of these pregnancies. T2* weighted placental MRI provides non-invasive information on placental oxygenation and thereby placental function. The aim of this study was to investigate the correlation between placental T2*, BW and placental histology. METHODS: A total of 63 pregnant women underwent T2* weighted placental MRI at 15-40 week's gestation and a standardized placental histological examination (PHE). Abnormal PHE was defined by vascular malperfusion according to the Amsterdam workshop consensus. The correlation between PHE, BW z-score and T2* z-score was analyzed by logistic regression. RESULTS: Abnormal PHE was revealed in 28 pregnancies. Multiple logistic regression revealed a significant correlation between abnormal PHE and T2* z-score (OR = 0.34, p = 0.008), whereas BW z-score did not add significantly to the correlation of placental histology (OR = 0.52, p = 0.115). In BW z-score≥0, PHE was normal in 100% of pregnancies. In BW z-score ≤ -2, PHE was abnormal in 89% of pregnancies. In intermediate BW (z-score between -2 and 0), PPE was abnormal in 35% of pregnancies. In this intermediate group, placental T2* z-score was reduced (-1.52 ± 1.22 (mean SD)) when compared to normal PHE pregnancies (-0.28 ± 1.17), p = 0.006. DISCUSSION: This study demonstrates a correlation between abnormal placental histology and low placental T2* value regardless of fetal size. This indicates that T2* provides information of placental function in vivo even when fetal size is normal. This finding highlights that fetal size alone is not a valid marker of placental dysfunction.

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.

Placental T2* estimated by magnetic resonance imaging and fetal weight estimated by ultrasound in the prediction of birthweight differences in dichorionic twin pairs.

INTRODUCTION: Intertwin birthweight (BW) difference is associated with an increased risk of adverse outcome. Ultrasound estimated fetal weight (EFW) is the current method to predict intertwin BW difference, however, the sensitivity is poor. Therefore, new methods are needed. Placental T2* estimated by magnetic resonance imaging (MRI) provides non-invasive information about the placental function. This study aimed to investigate placental T2* difference as a new predictor of BW difference, and to compare it to the EFW. METHODS: We included 25 dichorionic twin pairs at 19-38 weeks' gestation. Placental T2* was obtained by MRI and EFW by ultrasound. Correlations between each predictor and BW difference were examined by simple linear regression, and the combined model was analyzed by multiple linear regression and likelihood ratio test. RESULTS: Strong positive correlations were demonstrated between intertwin differences in placental T2* and BW (r = 0.80, p < 0.005), and EFW and BW (r = 0.64, p < 0.005). Placental T2* difference was a strong independent predictor of BW difference (p < 0.001), and the combined model performed better than each predictor alone (p < 0.0001). DISCUSSION: This pilot study demonstrates that placental T2* difference may be a predictor of intertwin BW difference irrespectively of fetal size. The clinical potential of this method deserves further investigation in a larger clinical study.

Placental baseline conditions modulate the hyperoxic BOLD-MRI response.

OBJECTIVES: Human pregnancies complicated by placental dysfunction may be characterized by a high hyperoxic Blood oxygen level-dependent (BOLD) MRI response. The pathophysiology behind this phenomenon remains to be established. The aim of this study was to evaluate whether it is associated with altered placental baseline conditions, including a lower oxygenation and altered tissue morphology, as estimated by the placental transverse relaxation time (T2*). METHOD: We included 49 normal pregnancies (controls) and 13 pregnancies complicated by placental dysfunction (cases), defined by a birth weight < 10th percentile in combination with placental pathological signs of vascular malperfusion. During maternal oxygen inhalation, we measured the relative ΔBOLD response ((hyperoxic BOLD - baseline BOLD)/baseline BOLD) from a dynamic single-echo gradient-recalled echo (GRE) MRI sequence and the absolute ΔT2* (hyperoxic T2*- baseline T2*) from breath-hold multi-echo GRE sequences. RESULTS: In the control group, the relative ΔBOLD response increased during gestation from 5% in gestational week 20 to 20% in week 40. In the case group, the relative ΔBOLD response was significantly higher (mean Z-score 4.94; 95% CI 2.41, 7.47). The absolute ΔT2*, however, did not differ between controls and cases (p = 0.37), whereas the baseline T2* was lower among cases (mean Z-score -3.13; 95% CI -3.94, -2.32). Furthermore, we demonstrated a strong negative linear correlation between the Log10 ΔBOLD response and the baseline T2* (r = -0.88, p < 0.0001). CONCLUSION: The high hyperoxic ΔBOLD response demonstrated in pregnancies complicated by placental dysfunction may simply reflect altered baseline conditions, as the absolute increase in placental oxygenation (ΔT2*) does not differ between groups.

Validity of Contrast-enhanced Ultrasonography and Dynamic Contrast-enhanced MR Enterography in the Assessment of Transmural Activity and Fibrosis in Crohn's Disease.

BACKGROUND AND AIMS: Increased small intestinal wall thickness correlates with both inflammatory activity and fibrosis in Crohn's disease [CD]. Assessment of perfusion holds promise as an objective marker distinguishing between the two conditions. Our primary aim was to determine if relative bowel wall perfusion measurements correlate with histopathological scores for inflammation or fibrosis in CD. METHODS: A total of 25 patients were investigated before elective surgery for small intestinal CD. Unenhanced ultrasonography [US] and magnetic resonance enterography [MRE] were applied to describe bowel wall thickness. Perfusion was assessed with contrast-enhanced US [CEUS] and dynamic contrast-enhanced MRE [DCE-MRE]. Histopathology was used as gold standard. RESULTS: Compared with histopathology, the mean wall thickness was 0.4 mm greater on US [range -0.3 to 1.0, p = 0.24] and 1.4 mm greater on MR [0.4 to 2.3, p = 0.006]. No correlation was found between the severity of inflammation or fibrosis on histopathology, and either DCE-MRE [r = -0.13, p = 0.54 for inflammation and r = 0.41, p = 0.05 for fibrosis] or CEUS [r = 0.16, p = 0.45 for inflammation and r = -0.28, p = 0.19 for fibrosis]. Wall thickness assessed with US was correlated with both histological inflammation [r = 0.611, p = 0.0012] and fibrosis [r = 0.399, p = 0.048]. The same was not true for MR [r = 0.41, p = 0.047 for inflammation and r = 0.29, p = 0.16 for fibrosis]. CONCLUSIONS: Bowel wall thickness assessed with US is a valid marker of inflammation in small intestinal CD. However, relative contrast enhancement of US or of MRE cannot distinguish between inflammatory activity and fibrosis.

Cerebral Oxygenation Measurements by Magnetic Resonance Imaging in Fetuses With and Without Heart Defects.

BACKGROUND: Children with major congenital heart defects are risking impaired cerebral growth, delayed cerebral maturation, and neurodevelopmental disorders. We aimed to compare the cerebral tissue oxygenation of fetuses with major heart defects to that of fetuses without heart defects as estimated by the magnetic resonance imaging modality T2*. T2* is low in areas with high concentrations of deoxyhemoglobin. METHODS AND RESULTS: At gestational age mean 32 weeks (early) and mean 37 weeks (late), we compared the fetal cerebral T2* in 28 fetuses without heart defects to that of 15 fetuses with major heart defects: transposition of the great arteries (n=7), coarctation of the aorta/hypoplastic aortic arch (n=5), tetralogy of Fallot (n=1), hypoplastic right heart (n=1), and common arterial trunk (n=1). The women were scanned with a 1.5 T Philips scanner using a breath-hold multiecho gradient echo sequence. Among fetuses without heart defects, the mean T2* value was 157 ms (95% confidence interval [CI], 152-163) early and 125 ms (95% CI, 120-130) late. These figures were significantly lower (mean 14 ms; 95% CI, 6-22; P<0.001) among fetuses with heart defects 143 ms (95% CI, 136-150) early and 111 ms (95% CI, 104-118) late. CONCLUSIONS: Our findings indicate that fetal cerebral T2* is measurable and that fetal cerebral tissue oxygenation measured by T2* is lower in fetuses with heart defects compared with fetuses without heart defects. This corroborates the hypothesis that tissue hypoxia may be a potential pathogenic factor that possibly affects brain development in fetuses with heart defects.

Dynamic Contrast-Enhanced Magnetic Resonance Enterography and Dynamic Contrast-Enhanced Ultrasonography in Crohn's Disease: An Observational Comparison Study.

Purpose e Cross-sectional imaging methods are important for objective evaluationof small intestinal inflammationinCrohn'sdisease(CD).The primary aim was to compare relative parameters of intestinal perfusion between contrast-enhanced ultrasonography (CEUS) and dynamic contrast-enhanced magnetic resonance enterography (DCE-MRE) in CD. Furthermore, we aimed at testing the repeatability of regions of interest (ROIs) for CEUS. Methods This prospective study included 25 patients: 12 females (age: 37, range: 19-66) with moderate to severe CD and a bowel wall thickness>3mm evaluated with DCE-MRE and CEUS. CEUS bolus injection was performed twice for repeatability and analyzed in VueBox®. Correlations between modalities were described with Spearman's rho, limits of agreement(LoA) and intraclass correlation coefficient(ICC). ROIrepeatability for CEUS was assessed. Results s The correlation between modalities was good and very good for bowel wall thickness (ICC=0.71, P<0.001) and length of the inflamed segment (ICC=0.89, P<0.001). Moderate-weak correlations were found for the time-intensity curve parameters: peak intensity (r=0.59, P=0.006), maximum wash-in-rate (r=0.62, P=0.004), and wash-in perfusion index (r=0.47, P=0.036). Best CEUS repeatability for peak enhancement was a mean difference of 0.73 dB (95% CI: 0.17 to 1.28, P=0.01) and 95% LoA from -3.8 to 5.3 dB. Good quality of curve fit improved LoA to -2.3 to 2.8 dB. Conclusion The relative perfusion of small intestinal CD assessed with DCE-MRE and CEUS shows only a moderate correlation. Applying strict criteria for ROIs is important and allows for good CEUS repeatability.

Prediction of low birth weight: Comparison of placental T2* estimated by MRI and uterine artery pulsatility index.

OBJECTIVE: Neonates at low birth weight due to placental dysfunction are at high risk of adverse outcomes. These outcomes can be substantially improved by prenatal identification. The Magnetic Resonance Imaging (MRI) constant, placental T2* reflects placental structure and oxygenation and thereby placental function. Therefore, we aimed to evaluate the performance of placental T2* in the prediction of low birth weight using the uterine artery (UtA) pulsatility index (PI) as gold standard. METHODS: This was a prospective observational study of 100 singleton pregnancies included at 20-40 weeks' gestation. Placental T2* was obtained using a gradient recalled multi-echo MRI sequence and UtA PI was measured using Doppler ultrasound. Placental pathological examination was performed in 57 of the pregnancies. Low birth weight was defined by a Z-score ≤ -2.0. RESULTS: The incidence of low birth weight was 15%. The median time interval between measurements and birth was 7.3 weeks (interquartile range 3.0, 13.7 weeks). Linear regression revealed significant associations between birth weight Z-score and both placental T2* Z-score (r = 0.68, p < 0.0001) and UtA PI Z-score (r = -0.43, p < 0.0001). Receiver operating characteristic curves demonstrated a significantly higher performance of T2* (AUC of 0.92; 95% CI, 0.85-0.98) than UtA PI (AUC of 0.74; 95% CI, 0.60-0.89) in the prediction of low birth weight (p = 0.010). Placental pathological findings were closely related to the T2* values. CONCLUSIONS: In this population, placental T2* was a strong predictor of low birth weight and it performed significantly better than the UtA PI. Thus, placental T2* is a promising marker of placental dysfunction which deserves further investigation.

Assessment of subchondral bone marrow lesions in knee osteoarthritis by MRI: a comparison of fluid sensitive and contrast enhanced sequences.

BACKGROUND: Bone marrow lesions (BMLs) in knee osteoarthritis (OA) can be assessed using fluid sensitive and contrast enhanced sequences. The association between BMLs and symptoms has been investigated in several studies but only using fluid sensitive sequences. Our aims were to assess BMLs by contrast enhanced MRI sequences in comparison with a fluid sensitive STIR sequence using two different segmentation methods and to analyze the association between the MR findings and disability and pain. METHODS: Twenty-two patients (mean age 61 years, range 41-79 years) with medial femoro-tibial knee OA obtained MRI and filled out a WOMAC questionnaire at baseline and follow-up (median interval of 334 days). STIR, dynamic contrast enhanced-MRI (DCE-MRI) and fat saturated T1 post-contrast (T1 CE FS) MRI sequences were obtained. All STIR and T1 CE FS sequences were assessed independently by two readers for STIR-BMLs and contrast enhancing areas of BMLs (CEA-BMLs) using manual segmentation and computer assisted segmentation, and the measurements were compared. DCE-MRIs were assessed for the relative distribution of voxels with an inflammatory enhancement pattern, Nvoxel, in the bone marrow. All findings were compared to WOMAC scores, including pain and overall symptoms, and changes from baseline to follow-up were analyzed. RESULTS: The average volume of CEA-BML was smaller than the STIR-BML volume by manual segmentation. The opposite was found for computer assisted segmentation where the average CEA-BML volume was larger than the STIR-BML volume. The contradictory finding by computer assisted segmentation was partly caused by a number of outliers with an apparent generally increased signal intensity in the anterior parts of the femoral condyle and tibial plateau causing an overestimation of the CEA-BML volume. Both CEA-BML, STIR-BML and Nvoxel were significantly correlated with symptoms and to a similar degree. A significant reduction in total WOMAC score was seen at follow-up, but no significant changes were observed for either CEA-BML, STIR-BML or Nvoxel. CONCLUSIONS: Neither the degree nor the volume of contrast enhancement in BMLs seems to add any clinical information compared to BMLs visualized by fluid sensitive sequences. Manual segmentation may be needed to obtain valid CEA-BML measurements.

Reduced placental oxygenation during subclinical uterine contractions as assessed by BOLD MRI.

OBJECTIVES: During placental Blood Oxygen Level Dependent (BOLD) Magnetic Resonance Imaging (MRI), we have observed spontaneous reductions in placental oxygenation lasting 2-4 min. We hypothesize, that these reductions in placental oxygenation are caused by subclinical uterine contractions. METHODS: We evaluated placental oxygenation during a five-minute placental BOLD MRI in 56 normal pregnancies (gestational week 23-40) and observed a spontaneous reduction in eight cases. The 56 BOLD MRIs were systematically analyzed for signs of uterine contractions, i.e. visual changes in uterus shape and reductions in the number of pixels within Regions of interest (ROI) covering the outline of the entire uterus. RESULTS: The eight reductions in the BOLD signal lasted for 217 ± 51 (mean ± SD) seconds with an average signal loss of 17 ± 5%. They were all associated with a contraction, which started 43 ± 21 s prior to the start of the reduction and ended 71 ± 30 s prior to the end of the reduction. In the remaining 48 MRIs, we observed no contraction. CONCLUSION: We suggest that the observed spontaneous reductions in placental oxygenation are caused by uterine contractions. According to our data, subclinical uterine contractions occur regularly and have a markedly impact on placental oxygenation. Therefore, uterine contractions need to be considered in the interpretation of placental MRI as they may interfere with the MRI results.

Placental oxygen transport estimated by the hyperoxic placental BOLD MRI response.

Estimating placental oxygen transport capacity is highly desirable, as impaired placental function is associated with fetal growth restriction (FGR) and poor neonatal outcome. In clinical obstetrics, a noninvasive method to estimate the placental oxygen transport is not available, and the current methods focus on fetal well-being rather than on direct assessment of placental function. In this article, we aim to estimate the placental oxygen transport using the hyperoxic placental blood oxygen level-dependent (BOLD) magnetic resonance imaging (MRI) response. In 21 normal pregnancies and in four cases of severe early onset FGR, placental BOLD MRI was performed in a 1.5 Tesla MRI system (TR:8000 msec, TE:50 msec, Flip angle:90). Placental histological examination was performed in the FGR cases. In normal pregnancies, the average hyperoxic placental BOLD response was 12.6 ± 5.4% (mean ± SD). In the FGR cases, the hyperoxic BOLD response was abnormal only in cases with histological signs of maternal hypoperfusion of the placenta. The hyperoxic placental BOLD response is mainly derived from an increase in the saturation of maternal venous blood. In the normal placenta, the pO2 of the umbilical vein is closely related to the pO2 of the uterine vein. Therefore, the hyperoxic placental BOLD response may reflect the placental oxygen supply to the fetus. In early onset FGR, the placental oxygen transport is reduced mainly because of the maternal hypoperfusion, and in these cases the placental BOLD response might be altered. Thus, the placental BOLD MRI might provide direct noninvasive assessment of placental oxygen transport.