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To assess the value of a T1-3D black-blood turbo spin echo (TSE) sequence for the diagnosis of abdominal large vessel vasculitis (LVV). The study included 20 patients with abdominal LVV and 17 controls, who underwent a 3T-MRI scan using a modified T1-3D volumetric isotropic TSE acquisition and a segmented T1-3D turbo field echo sequence (T1-mVISTA/T1-eTHRIVE). Two radiologists independently analyzed the aorta for concentric contrast enhancement, concentric wall thickening, image quality, and flow artifact intensity (CCE/CWT/IQ/FAI; 4-point scales). The mean aortic wall thickness (MAWT) in post-contrast T1-mVISTA was compared between patients and controls. IQ of T1-mVISTA was rated good to excellent in 91.5% of 282 evaluated vessel segments with no or minor FAI present in 85.5%. The inter-observer reproducibility for the identification of CCE/CWT on T1-mVISTA was 0.92 and 0.93 (p

OBJECTIVELumbosacral radicular syndrome (LRS) is a very common condition, often requiring diagnostic imaging with the aim of elucidating a structural cause when symptoms are longer lasting. However, findings on conventional anatomical MRI do not necessarily correlate with clinical symptoms, and it is primarily performed for the qualitative evaluation of surrounding compressive structures, such as herniated discs, instead of to evaluate the nerves directly. The present study investigated the performance of quantitative imaging by using magnetic resonance neurography (MRN) in patients with LRS.METHODSEighteen patients (55.6% males, mean age 64.4 ± 10.2 years), with strict unilateral LRS matching at least one dermatome and suspected disc herniation, underwent high-resolution 3-T MRN using T2 mapping. On T2 maps, the presumably affected and contralateral unaffected nerves were identified; subsequent regions of interest (ROIs) were placed at preganglionic, ganglionic, and postganglionic sites; and T2 values were extracted. Patients then underwent an epidural steroid injection (ESI) with local anesthetic agents at the site of suspected nerve affection. T2 values of the affected nerves were compared against the contralateral nerves. Furthermore, receiver operating characteristics were calculated based on the measured T2 values and the responsiveness to ESI.RESULTSThe mean T2 value was 77.3 ± 1.9 msec for affected nerves and 74.8 ± 1.4 msec for contralateral nerves (p < 0.0001). In relation to ESI performed at the site of suspected nerve affection, MRN with T2 mapping had a sensitivity/specificity of 76.9%/60.0% and a positive/negative predictive value of 83.3%/50.0%. Signal alterations in affected nerves according to qualitative visual inspection were present in only 22.2% of patients.CONCLUSIONSAs one of the first of its kind, this study revealed elevated T2 values in patients suffering from LRS. T2 values of lumbosacral nerves might be used as more objective parameters to directly detect nerve affection in such patients.

Background We aimed to investigate the clinical value of a 3D-T1w turbo-spin-echo (TSE) sequence and [18F]fluorodeoxyglucose positron emission tomography/computed tomography ([18F]FDG-PET/CT) for the diagnosis of active large vessel vasculitis (LVV) and single-organ vasculitis (SOV) of the aorta. Methods Twenty-four patients with suspected vasculitis who underwent MRI and PET/CT were retrospectively evaluated. MRI was analyzed for concentric contrast enhancement and wall thickening, and flow artifact intensity (4-point-scales). PET/CT analysis comprised qualitative, quantitative and semiquantitative methods. Imaging findings were correlated with final diagnosis derived from the clinical follow-up data. Results Fifteen of 24 patients had a clinically confirmed active vasculitis, two had inactive vasculitis and 7 no vasculitis. [18F]FDG-PET/CT and 3D-T1w TSE-MRI revealed both a high diagnostic accuracy of 88% and 83%, respectively. In patients in whom both PET/CT and MRI showed concordant findings (19 patients), the accuracy increased to 95% with a high positive predictive value (92%) and negative predictive value (100%); thus, a correct diagnosis was obtained in 18 of 19 patients. Among the five patients with discordant findings PET/CT correctly identified the two patients without active vasculitis while rated false positive on MRI. Of the three remaining patients with active vasculitis, two were correctly identified by MRI and one by PET/CT. Conclusions 3D-T1w TSE-MRI and [18F]FDG-PET/CT are both useful in the diagnosis of active vasculitis with high diagnostic accuracies. The diagnostic accuracy was even optimized by combining the two analysis methods. Therefore, there might be substantial potential for the application of whole-body hybrid PET/MRI in the evaluation of vasculitis in future studies.

To investigate the feasibility of fetal phase-contrast (PC)-MR angiography of the descending aorta (AoD) using an MR-compatible Doppler ultrasound sensor (DUS) for fetal cardiac gating and to compare velocimetry with Doppler ultrasound measurements.In this prospective study, 2D PC-MR angiography was performed in 12 human fetuses (mean gestational age 32.8 weeks) using an MR-compatible DUS for gating of the fetal heart at 1.5 T. Peak flow velocities in the fetal AoD were compared with Doppler ultrasound measurements performed on the same day. Reproducibility of PC-MR measurements was tested by repeated PC-MR in five fetuses.Dynamic PC-MR angiography in the AoD was successfully performed in all fetuses using the DUS, with an average fetal heart rate of 140 bpm (range 129-163). Time-velocity curves revealed typical arterial blood flow patterns. PC-MR mean flow velocity and mean flux were 21.2 cm/s (range 8.6-36.8) and 8.4 ml/s (range 3.2-14.6), respectively. A positive association between PC-MR mean flux and stroke volume with gestational age was obtained (r = 0.66, p = 0.02 and r = 0.63, p = 0.03). PC-MR and Doppler ultrasound peak velocities revealed a highly significant correlation (r = 0.8, p 0.002). Peak velocities were lower for PC-MR with 69.1 cm/s (range 39-125) compared with 96.7 cm/s (range 60-142) for Doppler ultrasound (p 0.001). Reproducibility of PC-MR was high (p 0.05).The MR-compatible DUS for fetal cardiac gating allows for PC-MR angiography in the fetal AoD. Comparison with Doppler ultrasound revealed a highly significant correlation of peak velocities with underestimation of PC-MR velocities. This new technique for direct fetal cardiac gating indicates the potential of PC-MR angiography for assessing fetal hemodynamics.• The developed MR-compatible Doppler ultrasound sensor allows direct fetal cardiac gating and can be used for prenatal dynamic cardiovascular MRI. • The MR-compatible Doppler ultrasound sensor was successfully applied to perform intrauterine phase-contrast MR angiography of the fetal aorta, which revealed a highly significant correlation with Doppler ultrasound measurements. • As fetal flow hemodynamics is an important parameter in the diagnosis and management of fetal pathologies, fetal phase-contrast MR angiography may offer an alternative imaging method in addition to Doppler ultrasound and develop as a second line tool in the evaluation of fetal flow hemodynamics.

To compare the influence of two different regions of interest (ROIs) on diffusion tensor metrics in dystrophic thigh muscles using a custom-made (whole muscle) ROI including and a selective ROI excluding areas of fatty replacement. Diffusion tensor imaging (DTI) and chemical-shift-encoded water-fat magnetic resonance imaging (MRI) of the thigh was conducted on a 3-Tesla system in 15 cases with muscular dystrophy and controls. The ROIs were chosen according to patterns of fatty replacement on co-registered axial DTI and gradient echo sequence (GRE) images. Fractional anisotropy (FA), apparent diffusion coefficient (ADC), fiber track length (FTL), and muscle fat fractions (MFF) were compared between both ROI segmentations. These comparisons, muscle-specific correlation coefficients, and the influence of ROI localization on tensor metrics were derived based on linear mixed effects regression models. In the cases a high correlation was observed for ADC and FA with MFF using a custom ROI. The correlation was weaker but still significant with a selective ROI method. Using the custom ROI, FTL correlated significantly with MFF in 3 out of 4 muscles (r ≤ −0.51). A correlation was not found for the selective ROI method. Interaction analysis revealed that the association of ADC and FA with MFF was not significantly influenced by the ROI localization. For FTL the ROI localization significantly reduced the negative association with MFF. The DTI metrics and FTL of custom ROI segmentation are significantly influenced by MFF. Contrary to ADC and FA, the effect of MFF on FTL is significantly reduced when applying selective ROI segmentation, which could therefore be a better option for MR tractography.

Purpose Isotropic high-resolution three-dimensional (3D) magnetic resonance neurography (MRN) is increasingly used to depict even small and highly oblique nerves of the lumbosacral plexus (LSP). The present study introduces a T2 mapping sequence (T2-prepared 3D turbo spin echo) that is B1-insensitive and enables quantitative assessment of LSP nerves. Methods In this study 15 healthy subjects (mean age 28.5 ± 3.8 years) underwent 3 T MRN of the LSP area three times. The T2 values were calculated offline on a voxel-by-voxel basis and measured at three segments (preganglionic, ganglionic, postganglionic) of three LSP nerves (S1, L5, L4) by two independent investigators (experienced and novice). Normative data for the different nerves were extracted and intraclass correlation coefficients (ICCs) were calculated to assess reproducibility and interobserver reliability of T2 measurements. Results The T2 mapping showed excellent reproducibility with ICCs ranging between 0.99 (S1 preganglionic) and 0.89 (L5 postganglionic). Interobserver reliability was less robust with ICCs ranging between 0.78 (S1 preganglionic) and 0.44 (L5 postganglionic) for S1 and L5. A mean T2 value of 74.6 ± 4.7 ms was registered for preganglionic segments, 84.7 ± 4.1 ms for ganglionic and 65.4 ± 2.5 ms for postganglionic segments, respectively. There was a statistically significant variation of T2 values across the nerve (preganglionic vs ganglionic vs postganglionic) for S1, L5, and L4. Conclusion Our approach enables isotropic high-resolution and B1-insensitive T2 mapping of LSP nerves with excellent reproducibility. It might reflect a robust and clinically useful method for future diagnostics of LSP pathologies. Electronic supplementary material The online version of this article (10.1007/s00062-017-0658-9) contains supplementary material, which is available to authorized users.

The aim of this study was to assess the diagnostic accuracy of a modified high-resolution whole-brain three-dimensional T1-weighted black-blood sequence (T1-weighted modified volumetric isotropic turbo spin echo acquisition [T1-mVISTA]) in comparison to a standard three-dimensional T1-weighted magnetization-prepared rapid gradient echo (MP-RAGE) sequence for detection of contrast-enhancing cerebral lesions in patients with relapsing-remitting multiple sclerosis (MS).After institutional review board approval and informed consent, 22 patients (8 men; aged 31.0 ± 9.2 years) with relapsing-remitting MS were included in this monocentric prospective cohort study.Contrast-enhanced T1-mVISTA and MP-RAGE, both with 0.8 mm resolution, were performed in all patients. In a substudy of 12 patients, T1-mVISTA was compared with a T1-mVISTA with 1.0 mm resolution (T1-mVISTA_1.0). Reference lesions were defined by an experienced neuroradiologist using all available sequences and served as the criterion standard. T1-mVISTA, T1-mVISTA_1.0, and MP-RAGE sequences were read in random order 4 weeks apart. Image quality, visual contrast enhancement, contrast-to-noise-ratio (CNR), diagnostic confidence, and lesion size were assessed and compared by Wilcoxon and Mann-Whitney U tests.Eleven of 22 patients displayed contrast-enhancing lesions. Visual contrast enhancement, CNR, and diagnostic confidence of contrast-enhancing MS lesions were significantly increased in T1-mVISTA compared with MP-RAGE (P0.001). Significantly more contrast-enhancing lesions were detected with T1-mVISTA than with MP-RAGE (71 vs 39, respectively; P0.001). With MP-RAGE, 25.6% of lesions were missed in the initial reading, whereas only 4.2% of lesions were missed with T1-mVISTA. Increase of the voxel volume from 0.8 mm to 1.0 mm isotropic in T1-mVISTA_1.0 did not affect the detectability of lesions, whereas scan time was decreased from 4:43 to 1:55 minutes.Three-dimensional T1-mVISTA improves the detection rates of contrast-enhancing cerebral MS lesions compared with conventional 3D MP-RAGE sequences by increasing CNR of lesions and might, therefore, be useful in patient management.

Objective The assessment of fatty infiltration and edema in the musculature of patients with neuromuscular diseases (NMDs) typically requires the separate performance of T-1-weighted and fat-suppressed T-2-weighted sequences. T-2-weighted Dixon turbo spin echo (TSE) enables the generation of T-2-weighted fat- and water-separated images, which can be used to assess both pathologies simultaneously. The present study examines the diagnostic performance of T-2-weighted Dixon TSE compared with the standard sequences in 10 patients with NMDs and 10 healthy subjects. Methods Whole-body magnetic resonance imaging was performed including T-1-weighted Dixon fast field echo, T-2-weighted short-tau inversion recovery, and T-2-weighted Dixon TSE. Fatty infiltration and intramuscular edema were rated by 2 radiologists using visual semiquantitative rating scales. To assess intermethod and interrater agreement, weighted Cohen's coefficients were calculated. Results The ratings of fatty infiltration showed high intermethod and high interrater agreement (T-1-weighted Dixon fast field echo vs T-2-weighted Dixon TSE fat image). The evaluation of edematous changes showed high intermethod and good interrater agreement (T-2-weighted short-tau inversion recovery vs T-2-weighted Dixon TSE water image). Conclusions T-2-weighted Dixon TSE imaging is an alternative for accelerated simultaneous grading of whole-body skeletal muscle fat infiltration and edema in patients with NMDs.

Background: To characterize the effect of phase errors on the magnitude and the phase of the diffusion-weighted (DW) signal acquired with diffusion-prepared turbo spin echo (dprep-TSE) sequences. Methods: Motion and eddy currents were identified as the main sources of phase errors. An analytical expression for the effect of phase errors on the acquired signal was derived and verified using Bloch simulations, phantom, and in vivo experiments. Results: Simulations and experiments showed that phase errors during the diffusion preparation cause both magnitude and phase modulation on the acquired data. When motion-induced phase error (MiPe) is accounted for (e.g., with motion-compensated diffusion encoding), the signal magnitude modulation due to the leftover eddy-current-induced phase error cannot be eliminated by the conventional phase cycling and sum-of-squares (SOS) method. By employing magnitude stabilizers, the phase-error-induced magnitude modulation, regardless of its cause, was removed but the phase modulation remained. The in vivo comparison between pulsed gradient and flow-compensated diffusion preparations showed that MiPe needed to be addressed in multi-shot dprep-TSE acquisitions employing magnitude stabilizers. Conclusions: A comprehensive analysis of phase errors in dprep-TSE sequences showed that magnitude stabilizers are mandatory in removing the phase error induced magnitude modulation. Additionally, when multi-shot dprep-TSE is employed the inconsistent signal phase modulation across shots has to be resolved before shot-combination is performed.

To evaluate the diagnostic value of a contrast-enhanced 3D T1-weighted-modified volumetric isotropic turbo spin-echo acquisition sequence (T1-mVISTA) in comparison with a conventional 3D T1-weighted magnetization-prepared rapid gradient-echo (T1-MP-RAGE) sequence for the detection of meningeal enhancement in patients with meningitis. Thirty patients (infectious meningitis, n = 12; neoplastic meningitis, n = 18) and 45 matched controls were enrolled in this retrospective case-control study. Sets of randomly selected T1-mVISTA and T1-MP-RAGE images (both with 0.8-mm isotropic resolution) were read separately 4 weeks apart. Image quality, leptomeningeal and dural enhancement, grading of visual contrast enhancement, and diagnostic confidence were compared using the Kruskal-Wallis rank sum test. Image quality was rated to be good to excellent in 75 out of 75 cases (100%) for T1-mVISTA and 74 out of 75 cases (98.7%) for T1-MP-RAGE. T1-mVISTA detected significantly more patients with leptomeningeal enhancement (p = 0.006) compared with T1-MP-RAGE (86.7 vs. 50.0%, p

Purpose To remove the confounding effect of unsuppressed fat on the imaging-based apparent diffusion coefficient (ADC) of the vertebral bone marrow water component when using spectrally selective fat suppression and to compare and validate the proposed quantification strategy against diffusion-weighted magnetic resonance spectroscopy (DW-MRS). Methods Twelve subjects underwent diffusion-weighted imaging (DWI) and DW-MRS of the vertebral bone marrow. A theoretical model was developed to take into account and correct the effects of residual fat on ADC, incorporating additional measurements for proton density fat fraction (PDFF) and water T2 (T2w). Uncorrected and corrected DWI-based ADC was compared with DW-MRS–based ADC using the Bland–Altman method. Results There was a systematic bias equal to 0.118 ± 0.116 × 10−3 mm2/s between DWI and DW-MRS when no correction was performed. Taking into account measured PDFF and constant T2w reduced the bias to 0.006 ± 0.128 × 10−3 mm2/s. Using the proposed approach with both individually measured PDFF and T2w reduced both the bias and the limits of agreement between DWI and DW-MRS (0.018 ± 0.065 × 10−3 mm2/s). Conclusion By taking into account the presence of residual fat in a modified signal model that incorporates additional individual measurements of PDFF and T2w, good agreement of imaging-based ADC with MRS-based ADC can be achieved in vertebral bone marrow. Magn Reson Med, 2016. © 2016 International Society for Magnetic Resonance in Medicine.

Purpose To propose a phase error correction scheme for monopolar time-interleaved multi-echo gradient echo water–fat imaging that allows accurate and robust complex-based quantification of the proton density fat fraction (PDFF). Methods A three-step phase correction scheme is proposed to address a) a phase term induced by echo misalignments that can be measured with a reference scan using reversed readout polarity, b) a phase term induced by the concomitant gradient field that can be predicted from the gradient waveforms, and c) a phase offset between time-interleaved echo trains. Simulations were carried out to characterize the concomitant gradient field-induced PDFF bias and the performance estimating the phase offset between time-interleaved echo trains. Phantom experiments and in vivo liver and thigh imaging were performed to study the relevance of each of the three phase correction steps on PDFF accuracy and robustness. Results The simulation, phantom, and in vivo results showed in agreement with the theory an echo time-dependent PDFF bias introduced by the three phase error sources. The proposed phase correction scheme was found to provide accurate PDFF estimation independent of the employed echo time combination. Conclusion Complex-based time-interleaved water–fat imaging was found to give accurate and robust PDFF measurements after applying the proposed phase error correction scheme. Magn Reson Med 78:984–996, 2017. © 2016 International Society for Magnetic Resonance in Medicine.

Purpose We aimed to determine the agreement between quantitative susceptibility mapping (QSM)-based biomagnetic liver susceptometry (BLS) and confounder-corrected R2* mapping with superconducting quantum interference device (SQUID)-based biomagnetic liver susceptometry in patients with liver iron overload. Methods Data were acquired from two healthy controls and 22 patients undergoing MRI and SQUID-BLS as part of routine monitoring for iron overload. Magnetic resonance imaging was performed on a 3T system using a three-dimensional multi-echo gradient-echo acquisition. Both magnetic susceptibility and R2* of the liver were estimated from this acquisition. Linear regression was used to compare estimates of QSM-BLS and R2* to SQUID-BLS. Results Both QSM-BLS and confounder-corrected R2* were sensitive to the presence of iron in the liver. Linear regression between QSM-BLS and SQUID-BLS demonstrated the following relationship: QSM-BLS = (−0.22 ± 0.11) + (0.49 ± 0.05) · SQUID-BLS with r2 = 0.88. The coefficient of determination between liver R2* and SQUID-BLS was also r2 = 0.88. Conclusion We determined a strong correlation between both QSM-BLS and confounder-corrected R2* to SQUID-BLS. This study demonstrates the feasibility of QSM-BLS and confounder-corrected R2* for assessing liver iron overload, particularly when SQUID systems are not accessible. Magn Reson Med 78:264–270, 2017. © 2016 International Society for Magnetic Resonance in Medicine

To evaluate the feasibility of T1w-3D black-blood turbo spin echo (TSE) sequence with variable flip angles for the diagnosis of thoracic large vessel vasculitis (LVV). Thirty-five patients with LVV, diagnosed according to the current standard of reference, and 35 controls were imaged at 3.0T using 1.2 × 1.3 × 2.0 mm3 fat-suppressed, T1w-3D, modified Volumetric Isotropic TSE Acquisition (mVISTA) pre- and post-contrast. Applying a navigator and peripheral pulse unit triggering (PPU), the total scan time was 10–12 min. Thoracic aorta and subclavian and pulmonary arteries were evaluated for image quality (IQ), flow artefact intensity, diagnostic confidence, concentric wall thickening and contrast enhancement (CWT, CCE) using a 4-point scale. IQ was good in all examinations (3.25 ± 0.72) and good to excellent in 342 of 408 evaluated segments (83.8 %), while 84.1 % showed no or minor flow artefacts. The interobserver reproducibility for the identification of CCE and CWT was 0.969 and 0.971 (p

Arteritic anterior ischemic optic neuropathy (A-AION) caused by inflammatory occlusion of the posterior ciliary arteries is the most common reason for irreversible vision loss in patients with giant cell arteritis. Atypical clinical presentation and negative funduscopy can delay systemic high-dose corticosteroid therapy to prevent impending permanent blindness and involvement of the contralateral eye.The purpose of this study was to assess the diagnostic accuracy of 3-dimensional (3D) high-resolution T1-weighted black-blood magnetic resonance imaging (T1-BB-MRI) for the detection of posterior ciliary artery involvement in patients with giant cell arteritis and funduscopic A-AION.After institutional review board approval and informed consent, 27 patients with suspected giant cell arteritis and vision disturbances were included in this monocentric prospective cohort study. Giant cell arteritis was diagnosed in 18 patients according to the diagnostic reference standard (6 men, 73.8 [69.0-78.0] years); 14 of those were positive for A-AION. Precontrast and postcontrast 3D T1-BB-MRI was performed in all 27 patients. Two radiologists separately assessed image quality and local fat suppression (4-point scale), visual contrast enhancement (3-point scale), and diagnostic confidence (5-point scale) regarding arteritic posterior ciliary artery involvement. Magnetic resonance imaging findings were assessed in comparison to funduscopy. Statistical analysis included accuracy parameters and interrater agreement.Sensitivity of 3D T1-BB-MRI was 92.9% (95% confidence interval, 66.1%-99.8%) and specificity was 92.3% (95% confidence interval, 64.0%-99.8%) for detection of A-AION-positive patients. Image quality and local fat suppression were assessed with 3.2 ± 0.8 (median 3) and 3.8 ± 0.5 (median 4). Visual contrast enhancement with 2.3 ± 0.8 (median 3) and diagnostic confidence was rated at 4.7 ± 0.5 (median 5). Interrater agreement was high (κ = 0.85, P0.001). Three-dimensional T1-BB-MRI displayed bilateral findings in 50% of the cases, whereas only unilateral A-AION was detected in funduscopy as a possible indication for the contralateral eye at risk.Three-dimensional T1-BB-MRI allows accurate detection of arteritic posterior ciliary artery involvement in patients with A-AION. Further, 3D T1-BB-MRI seems to display arteritic involvement of the posterior ciliary arteries earlier than funduscopy and might, therefore, display "vision-at-risk" in patients with visual impairment and suspected giant cell arteritis but unremarkable funduscopy.

To assess the diagnostic value of multiparametric magnetic resonance imaging (MRI) including dynamic Gd-EOB-DTPA-enhanced (DCE) and diffusion-weighted (DW) imaging for diagnosis and staging of hepatic fibrosis in primary sclerosing cholangitis (PSC) using transient elastography as a standard reference.Multiparametric MRI was prospectively performed on a 3.0-Tesla scanner in 47 patients (age 43.9±14.3 years). Transient elastography derived liver stiffness measurements (LSM), DCE-MRI derived parameters (hepatocellular uptake rate (Ki), arterial (Fa), portal venous (Fv) and total (Ft) blood flow, mean transit time (MTT), and extracellular volume (Ve)) and the apparent diffusion coefficient (ADC) were calculated. Correlation and univariate analysis of variance with post hoc pairwise comparison were applied to test for differences between LSM derived fibrosis stages (F0/F1, F2/3, F4). ROC curve analysis was used as a performance measure.Both ADC and Ki correlated significantly with LSM (r= -0.614; p0.001 and r= -0.368; p=0.01). The ADC significantly discriminated fibrosis stages F0/1 from F2/3 and F4 (p0.001). Discrimination of F0/1 from F2/3 and F4 reached a sensitivity/specificity of 0.917/0.821 and 0.8/0.929, respectively. Despite significant inter-subject effect for classification of fibrosis stages, post hoc pairwise comparison was not significant for Ki (p0.096 for F0/1 from F2/3 and F4). LSM, ADC and Ki were significantly associated with serum-based liver functional tests, disease duration and spleen volume.DW-MRI provides a higher diagnostic performance for detection of hepatic fibrosis and cirrhosis in PSC patients in comparison to Gd-EOB-DTPA-enhanced DCE-MRI.• Both ADC and hepatocellular uptake rate (Ki) correlate significantly with liver stiffness (r= -0.614; p0.001 and r= -0.368; p=0.01). • The DCE-imaging derived quantitative parameter hepatocellular uptake rate (Ki) fails to discriminate pairwise intergroup differences of hepatic fibrosis (p0.09). • DWI is preferable to DCE-imaging for discrimination of fibrosis stages F0/1 to F2/3 (p0.001) and F4 (p0.001).

Purpose To study the effects of refocusing angle modulation with 3D turbo spin echo (TSE) on signal and sharpness of small oblique nerves embedded in muscle and suppressed fat in the lumbar plexus. Materials and Methods Flip angle trains were generated with extended phase graphs (EPG) for a sequence parameter subspace. Signal loss and width broadening were simulated for a single-pixel nerve embedded in muscle and suppressed fat to prescribe a flip angle modulation that gives the best compromise between signal and sharpness of small nerves. Two flip angle trains were defined based on the simulations of small embedded nerves: design denoted A, predicting maximum global signal, and design denoted B, predicting maximum signal for minimum width broadening. In vivo data of the lumbar plexus in 10 healthy volunteers was acquired at 3.0T with 3D TSE employing flip angle trains A and B. Quantitative and qualitative analyses of the acquired data were made to assess changes in width and signal intensity. Results Changing flip angle modulation from A to B resulted in: 1) average signal losses of 23% in (larger) L5 nerves and 9% in (smaller) L3 nerves; 2) average width reductions of 4% in L5 nerves and of 16% in L3 nerves; and 3) statistically significant sharpness improvement (P = 0.005) in L3 nerves. Conclusion An optimized flip angle train in 3D TSE imaging of the lumbar plexus considering geometry-specific blurring effects from both the nerve and the surrounding tissue can improve the delineation of small nerves. J. Magn. Reson. Imaging 2015.

Bone marrow fat fraction mapping using chemical shift encoding-based water-fat separation is becoming a useful tool in investigating the association between bone marrow adiposity and bone health and in assessing cancer treatment-induced bone marrow damage. Vertebral bone marrow is characterized by short T2* relaxation times, which are in general different for the water and fat components and can confound fat quantification. The purpose of the present study is to compare different approaches to T2* correction in chemical shift encoding-based water-fat imaging of vertebral bone marrow using single-voxel MRS as reference. Eight-echo gradient-echo imaging and single-voxel MRS measurements were made on the spine (L3-L5) of 25 healthy volunteers. Different approaches were evaluated for correction of T2* effects: (a) single-T2* correction, (b) dual-T2* correction, (c) T2' correction using the a priori-known T2 from the MRS at each vertebral body and (d) T2' correction using the a priori-known T2 equal to previously measured average values. Dual-T2* correction resulted in noisier imaging fat fraction maps than single-T2* correction or T2' correction using a priori-known T2. Linear regression analysis between imaging and MRS fat fraction showed a slope significantly different from 1 when using single-T2* correction (R(2) = 0.96) or dual-T2* correction (R(2) = 0.87). T2' correction using the a priori-known T2 resulted in a slope not significantly different from 1, an intercept significantly different from 0 (between 2.4% and 3%) and R(2) = 0.96. Therefore, a T2' correction using a priori-known T2 can remove the fat fraction bias induced by the difference in T2* between water and fat components without degrading noise performance in fat fraction mapping of vertebral bone marrow.

Purpose To determine changes in the bone marrow fat fraction (BMFF) in obesity after dietary intervention in comparison with changes in abdominal fat, liver fat, and serum lipids. Materials and methods Twenty obese (BMI 34.92 ± 3.8 kg/m(2) ) women participated in a 4-week dietary intervention of 800 kcal/d plus additional vegetables. They underwent anthropometric and blood value measurements before and after the intervention. Abdominal 3T MRI was performed to measure changes in subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT) volume and single-voxel magnetic resonance spectroscopy (MRS) to measure fat content changes in the liver and L5 vertebral body. Results The greatest relative change after dietary intervention was found in the liver (-40.3%), followed by VAT volume (-15.1%), serum lipids (-12.6 to -14.5%), and SAT volume (-8.5%). There were no statistically significant changes in BMFF after dietary intervention (P = 0.39), but absolute changes in the BMFF were positively associated with SAT volume (r = 0.489) and negatively associated with nonadipose tissue volume (r = -0.493) before dietary intervention. Conclusion Bone marrow behaves differently compared to SAT volume, VAT volume, liver fat, and serum lipids after a 4-week dietary intervention in obesity and BMFF changes depend on abdominal tissue volumes before intervention.

Purpose To propose and optimize diffusion-weighted stimulated echo acquisition mode (DW-STEAM) for measuring fat unsaturation in the presence of a strong water signal by suppressing the water signal based on a shorter T2 and higher diffusivity of water relative to fat. Methods A parameter study for point-resolved spectroscopy (PRESS) and STEAM using oil phantoms was performed and correlated with gas chromatography (GC). Simulations of muscle tissue signal behavior using DW-STEAM and long–echo time (TE) PRESS and a parameter optimization for DW-STEAM were conducted. DW-STEAM and long-TE PRESS were applied in the gastrocnemius muscles of nine healthy subjects. Results STEAM with TE and mixing time (TM) up to 45 ms exhibited R2 correlations above 0.98 with GC and little T2-weighting and J-modulation for the quantified olefinic/methylene peak ratio. The optimal parameters for muscle tissue using DW-STEAM were b-value = 1800 s/mm2, TE = 33 ms, TM = 30 ms, and repetition time = 2300 ms. In vivo measured mean olefinic signal-to-noise ratios were 72 and 40, mean apparent olefinic water fractions were 0.19 and 0.11 for DW-STEAM and long-TE PRESS, respectively. Conclusion Optimized DW-STEAM MR spectroscopy is superior to long-TE PRESS for measuring fat unsaturation, if a strong water peak prevents the olefinic fat signal's quantification at shorter TEs and water's tissue specific ADC is substantially higher than fat. Magn Reson Med 75:32–41, 2016. © 2015 Wiley Periodicals, Inc.

BACKGROUND Susceptibility weighted imaging and assessment of intratumoral susceptibility signal (ITSS) morphology is used to identify high-grade glioma (HGG) in patients with suspected brain neoplasm. PURPOSE The aim of this study was to outline variations in ITSS-morphology and their relationship to location as well as volume of the lesion in patients with glioblastoma (GB). MATERIALS AND METHODS Contrast-enhanced SWI (CE-SWI) images of 40 patients with histologically confirmed GB were analyzed retrospectively with particular attention to ITSS-morphology dividing all lesions into two groups. Considering the location of the lesion within brain parenchyma, lesions with and without involvement of the subventricular zone (SVZ+/SVZ−) were discerned. Additionally, the contrast-enhancing tumor volume was evaluated. Statistical analysis was based on a classification analysis resulting in a classification rule (tree) as well as Mann-Whitney-U test. RESULTS The distribution of ITSS-scores showed differences between the SVZ+ and SVZ− groups. While SVZ-GB showed only fine-linear or dot-like ITSS, in SVZ+ GB the ITSS-morphology changed with the tumor volume, that is, in larger tumors dense and conglomerated ITSS were the predominant finding. CONCLUSION Our findings indicate that ITSS-morphology is not a random phenomenon. Location of GB, as well as tumor volume, appear to be factors contributing to ITSS morphology.

Vertebral bone marrow fat quantification using single-voxel MRS is confounded by overlapping water-fat peaks and the difference in T2 relaxation time between water and fat components. The purposes of the present study were: (i) to determine the proton density fat fraction (PDFF) of vertebral bone marrow using single-voxel multi-TE MRS, addressing these confounding effects; and (ii) to investigate the implications of these corrections with respect to the age dependence of the PDFF. Single-voxel MRS was performed in the L5 vertebral body of 86 subjects (54 women and 32 men). To reliably extract the water peak from the overlying fat peaks, the mean bone marrow fat spectrum was characterized based on the area of measurable fat peaks and an a priori knowledge of the chemical triglyceride structure. MRS measurements were performed at multiple TEs. The T2 -weighted fat fraction was calculated at each TE. In addition, a T2 correction was performed to obtain the PDFF and the T2 value of water (T2w ) was calculated. The implications of the T2 correction were investigated by studying the age dependence of the T2 -weighted fat fractions and the PDFF. Compared with the PDFF, all T2 -weighted fat fractions significantly overestimated the fat fraction. Compared with the age dependence of the PDFF, the age dependence of the T2 -weighted fat fraction showed an increased slope and intercept as TE increased for women and a strongly increased intercept as TE increased for men. For women, a negative association between the T2 value of bone marrow water and PDFF was found. Single-voxel MRS-based vertebral bone marrow fat quantification should be based on a multi-TE MRS measurement to minimize confounding effects on PDFF determination, and also to allow the simultaneous calculation of T2w , which might be considered as an additional parameter sensitive to the composition of the water compartment. Copyright © 2015 John Wiley& Sons, Ltd.

The assessment of bone marrow composition has recently gained significant attention due to its association with bone loss pathophysiology and cancer therapy-induced bone marrow damage. The purpose of our study was to investigate the anatomical variation of the vertebral bone marrow fat using chemical shift-encoding based water-fat MRI and to assess the repeatability of these measurements.Chemical shift-encoding based water-fat MRI of the whole spine was performed in 28 young, healthy subjects (17 males, 11 females, 26 ± 4 years). Six subjects were scanned three times with repositioning to assess the repeatability of these measurements. Proton density fat fraction (PDFF) maps were computed and manually segmented to obtain PDFF of C3-L5.Mean PDFF of all subjects significantly increased from C3 to L5 (P< 0.05) with r = 0.88 (P< 0.05). PDFF averaged over C3-7, T1-6, T7-12, and L1-5 of males and females amounted to 31.7 ± 7.9% and 23.0 ± 7.8% (P = 0.002), 33.8 ± 6.8% and 24.6 ± 8.8% (P = 0.005), 33.8 ± 6.4% and 26.1 ± 6.4% (P = 0.023), and 38.8 ± 7.6% and 31.5 ± 12.4% (P = 0.063), respectively. The repeatability for PDFF measurements expressed as absolute precision error was 1.7% averaged over C3-L5.Whole spine vertebral bone marrow fat could be reproducibly assessed by using chemical shift-encoding based water-fat MRI and showed anatomical variations.

Background Diffusion tensor imaging (DTI) of peripheral nerves may provide additional information about nerve involvement in muscular disorders, but is considered difficult due to different optimal scan parameters tailored to magnetic resonance (MR) signal properties of muscle and neural tissues. Purpose To assess the feasibility of sciatic nerve DTI using two different approaches of region of interest (ROI)-localization in DTI scans with b-values 500 s/mm2, in participants with muscular disorders and in controls. Material and Methods DTI of the thigh was conducted on a 3T system in ten patients (6 men, 4 women; mean age =54 ± 15 years) with neuromuscular disorders and ten controls. T1-weighted (T1W) images were co-registered to fractional anisotropy (FA) color-encoded images. The apparent diffusion coefficient (ADC), FA, and fiber track length (FTL) were analyzed by two operators using a freehand ROI and a single-point ROI covering the sciatic nerve. Interclass correlation coefficient (ICC) and Bland–Altman analysis were used for evaluation of inter-operator and inter-technical agreement, respectively. Results Three-dimensional visualization of sciatic nerve fiber was achievable using both techniques. The ICC of DTI metrics showed excellent inter-operator agreement both in patients and controls. Bland–Altman analysis revealed good agreement of both techniques. A maximum FTL was achieved using the single-point ROI technique, but with a lower inter-operator agreement (ICC = 0.99 vs. 0.83). The ADC and maximum FTL were significantly decreased in patients compared to controls. Conclusion Both ROI localization techniques are feasible to analyze the sciatic nerve in the setting of muscular disease. A maximum FTL is reached using the single-point ROI, however, at the cost of lower inter-operator agreement.

A blood oxygenation level-dependent (BOLD)-based apparent relative oxygen extraction fraction (rOEF) as a semi-quantitative marker of vascular deoxygenation has recently been introduced in clinical studies of patients with glioma and stroke, yielding promising results. These rOEF measurements are based on independent quantification of the transverse relaxation times T2 and T2* and relative cerebral blood volume (rCBV). Simulations demonstrate that small errors in any of the underlying measures may result in a large deviation of the calculated rOEF. Therefore, we investigated the validity of such measurements. For this, we evaluated the quantitative measurements of T2 and T2* at 3 T in a gel phantom, in healthy subjects and in healthy tissue of patients with brain tumors. We calculated rOEF maps covering large portions of the brain from T2, T2* and rCBV [routinely measured in patients using dynamic susceptibility contrast (DSC)], and obtained rOEF values of 0.63 ± 0.16 and 0.90 ± 0.21 in healthy-appearing gray matter (GM) and white matter (WM), respectively; values of about 0.4 are usually reported. Quantitative T2 mapping using the fast, clinically feasible, multi-echo gradient spin echo (GRASE) approach yields significantly higher values than much slower multiple single spin echo (SE) experiments. Although T2* mapping is reliable in magnetically homogeneous tissues, uncorrectable macroscopic background gradients and other effects (e.g. iron deposition) shorten T2*. Cerebral blood volume (CBV) measurement using DSC and normalization to WM yields robust estimates of rCBV in healthy-appearing brain tissue; absolute quantification of the venous fraction of CBV, however, is difficult to achieve. Our study demonstrates that quantitative measurements of rOEF are currently biased by inherent difficulties in T2 and CBV quantification, but also by inadequacies of the underlying model. We argue, however, that standardized, reproducible measurements of apparent T2, T2* and rCBV may still allow the estimation of a meaningful apparent rOEF, which requires further validation in clinical studies.

Purpose To calculate regional fetal brain oxygen saturation (sO2) during hypoxia in sheep. Materials and Methods Eight pregnant ewes were examined at a 3T MR-scanner using blood oxygenation level-dependent magnetic resonance imaging (BOLD-MRI) to measure signal intensity changes of the fetal brain during a control period and a period of induced hypoxia. Regions of interest were placed in the fetal cerebrum to assess ΔR2* from GRE signal intensity plateaus (Scontrol, Shypoxia) and the relation between ΔR2* and ΔpO2 was analyzed. A probe was placed surgically in the fetal brain to directly measure local pO2 as a reference standard. Baseline and hypoxic pO2 values were recorded and compared (ΔpO2). Results Mean fetal brain pO2 decreased from 14.3 mmHg (95% confidence interval [CI]: 10–19) to 3.4 mmHg (95% CI: 2–5) during hypoxia (mean ΔpO2 = 10.9 mmHg and ΔR2* = −5s−1). A significant correlation between ΔR2* and ΔpO2 was noted (r = 0.93, P

Hypoxia plays a central role in tumor stem cell genesis and is related to a more malignant tumor phenotype, therapy resistance (e.g. in anti-angiogenic therapies) and radio-insensitivity. Reliable hypoxia imaging would provide crucial metabolic information in the diagnostic work-up of brain tumors. In this study, we applied a novel BOLD-based MRI method for the measurement of relative oxygen extraction fraction (rOEF) in glioma patients and investigated potential benefits and drawbacks. Forty-five glioma patients were examined preoperatively in a pilot study on a 3T MR scanner. rOEF was calculated from quantitative transverse relaxation rates (T2, T2*) and cerebral blood volume (CBV) using a quantitative BOLD approach. rOEF maps were assessed visually and by means of a volume of interest (VOI) analysis. In six cases, MRI-targeted biopsy samples were analyzed using HIF-1α-immunohistochemistry. rOEF maps could be obtained with a diagnostic quality. Focal spots with high rOEF values were observed in the majority of high-grade tumors but in none of the low-grade tumors. VOI analysis revealed potentially hypoxic tumor regions with high rOEF in contrast-enhancing tumor regions as well as in the non-enhancing infiltration zone. Systematic bias was found as a result of non-BOLD susceptibility effects (T2*) and contrast agent leakage affecting CBV. Histological samples demonstrated reasonable correspondence between MRI characteristics and HIF-1α-staining. The presented method of rOEF imaging is a promising tool for the metabolic characterization of human glioma. For the interpretation of rOEF maps, confounding factors must be considered, with a special focus on CBV measurements in the presence of contrast agent leakage. Further validation involving a bigger cohort and extended immuno-histochemical correlation is required.

SWI can help to identify high-grade gliomas (HGG). The objective of this study was to analyse SWI and CE-SWI characteristics, i.e. the relationship between contrast-induced phase shifts (CIPS) and intratumoral susceptibility signals (ITSS) and their association with tumour volume in patients with glioblastoma multiforme (GBM). MRI studies of 29 patients were performed to evaluate distinct susceptibility signals comparing SWI and CE-SWI characteristics. The relationship between these susceptibility signals and CE-T1w tumour volume was analysed by using Spearman’s rank correlation coefficient and Kruskal-Wallis-test. Tumour biopsies of different susceptibility signals were performed in one patient. Comparison of SWI and CE-SWI demonstrated different susceptibility signals. Susceptibility signals visible on SWI images are consistent with ITSS; those only seen on CE-SWI were identified as CIPS. Correlation with CE-T1w tumour volume revealed that CIPS were especially present in small or medium-sized GBM (Spearman’s rho r = 0.843, P

To assess changes in diffusion properties in the fetal lung after cortisone administration with diffusion-weighted imaging (DWI) in fetal sheep.DWI was performed on 11 pregnant sheep with singleton pregnancies on a 1.5-T MRI scanner. Four animals received cortisone injections before baseline imaging. Seven animals served as controls. Apparent diffusion coefficient (ADC) was measured on DWI in the fetal lungs by two independent readers. The Pearson test was used to correlate ADC and gestational age. A t-test was performed to compare differences in ADC values at the baseline and follow-up images within and between groups. Inter-rater reliability was calculated.In the cortisone group, ADC values increased about 10 % between the baseline and follow-up images (P = 0.039). Comparing the cortisone and control groups, ADC values of the baseline images did not differ; whereas in the follow-up imaging, ADC values were significantly higher in the cortisone group (P = 0.024). Lung ADC values did not correlate with gestational age (P = 0.970). Inter-rater reliability was high (0.970, P = 0.000).In this experimental model, MR-DWI can detect cortisone-induced changes in diffusion properties of the fetal lung.• Corticosteroids are frequently administered antenatally to prevent fetal lung immaturity at birth • DWI can detect changes in the fetal lung after corticosteroid administration • Changes can be detected as early as 5 days after treatment • Fetal MRI may offer a non-invasive method of monitoring lung maturation.

The purpose of this work was to investigate the performance of the modified BIR-4 T

To design a preparation module for vessel signal suppression in MR neurography of the extremities, which causes minimal attenuation of nerve signal and is highly insensitive to eddy currents and motion.The orthogonally combined motion- and diffusion-sensitized driven equilibrium (OC-MDSDE) preparation was proposed, based on the improved motion- and diffusion-sensitized driven equilibrium methods (iMSDE and FC-DSDE, respectively), with specific gradient design and orientation. OC-MDSDE was desensitized against eddy currents using appropriately designed gradient prepulses. The motion sensitivity and vessel signal suppression capability of OC-MDSDE and its components were assessed in vivo in the knee using 3D turbo spin echo (TSE). Nerve-to-vessel signal ratios were measured for iMSDE and OC-MDSDE in 7 subjects.iMSDE was shown to be highly sensitive to motion with increasing flow sensitization. FC-DSDE showed robustness against motion, but resulted in strong nerve signal loss with diffusion gradients oriented parallel to the nerve. OC-MDSDE showed superior vessel suppression compared to iMSDE and FC-DSDE and maintained high nerve signal. Mean nerve-to-vessel signal ratios in 7 subjects were 0.40 ± 0.17 for iMSDE and 0.63 ± 0.37 for OC-MDSDE.OC-MDSDE combined with 3D TSE in the extremities allows high-near-isotropic-resolution imaging of peripheral nerves with reduced vessel contamination and high nerve signal. Magn Reson Med 79:407-415, 2018. © 2017 Wiley Periodicals, Inc.

PURPOSE:To propose a T2-prepared 3D turbo spin echo (T2prep 3D TSE) sequence for B1-insensitive skeletal muscle T2 mapping and compare its performance with 2D and 3D multi-echo spin echo (MESE) for T2 mapping in thigh muscles of healthy subjects. METHODS:The performance of 2D MESE, 3D MESE and the proposed T2prep 3D TSE in the presence of transmit B1 and B0 inhomogeneities was first simulated. The thigh muscles of ten young and healthy subjects were then scanned on a 3 T system and T2 mapping was performed using the three sequences. Transmit B1-maps and proton density fat fraction (PDFF) maps were also acquired. The subjects were scanned three times to assess reproducibility. T2 values were compared among sequences and their sensitivity to B1 inhomogeneities was compared to simulation results. Correlations were also determined between T2 values, PDFF and B1. RESULTS:The left rectus femoris muscle showed the largest B1 deviations from the nominal value (from 54.2% to 92.9%). Significant negative correlations between T2 values and B1 values were found in the left rectus femoris muscle for 3D MESE (r = -0.72, p

To remove the confounding effect of unsuppressed fat on the imaging-based apparent diffusion coefficient (ADC) of the vertebral bone marrow water component when using spectrally selective fat suppression and to compare and validate the proposed quantification strategy against diffusion-weighted magnetic resonance spectroscopy (DW-MRS).Twelve subjects underwent diffusion-weighted imaging (DWI) and DW-MRS of the vertebral bone marrow. A theoretical model was developed to take into account and correct the effects of residual fat on ADC, incorporating additional measurements for proton density fat fraction (PDFF) and water TThere was a systematic bias equal to 0.118 ± 0.116 × 10By taking into account the presence of residual fat in a modified signal model that incorporates additional individual measurements of PDFF and T

To propose a phase error correction scheme for monopolar time-interleaved multi-echo gradient echo water-fat imaging that allows accurate and robust complex-based quantification of the proton density fat fraction (PDFF).A three-step phase correction scheme is proposed to address a) a phase term induced by echo misalignments that can be measured with a reference scan using reversed readout polarity, b) a phase term induced by the concomitant gradient field that can be predicted from the gradient waveforms, and c) a phase offset between time-interleaved echo trains. Simulations were carried out to characterize the concomitant gradient field-induced PDFF bias and the performance estimating the phase offset between time-interleaved echo trains. Phantom experiments and in vivo liver and thigh imaging were performed to study the relevance of each of the three phase correction steps on PDFF accuracy and robustness.The simulation, phantom, and in vivo results showed in agreement with the theory an echo time-dependent PDFF bias introduced by the three phase error sources. The proposed phase correction scheme was found to provide accurate PDFF estimation independent of the employed echo time combination.Complex-based time-interleaved water-fat imaging was found to give accurate and robust PDFF measurements after applying the proposed phase error correction scheme. Magn Reson Med 78:984-996, 2017. © 2016 International Society for Magnetic Resonance in Medicine.

To develop a fully automatic algorithm for abdominal organs and adipose tissue compartments segmentation and to assess organ and adipose tissue volume changes in longitudinal water-fat magnetic resonance imaging (MRI) data.Axial two-point Dixon images were acquired in 20 obese women (age range 24-65, BMI 34.9±3.8kg/m(2)) before and after a four-week calorie restriction. Abdominal organs, subcutaneous adipose tissue (SAT) compartments (abdominal, anterior, posterior), SAT regions along the feet-head direction and regional visceral adipose tissue (VAT) were assessed by a fully automatic algorithm using morphological operations and a multi-atlas-based segmentation method.The accuracy of organ segmentation represented by Dice coefficients ranged from 0.672±0.155 for the pancreas to 0.943±0.023 for the liver. Abdominal SAT changes were significantly greater in the posterior than the anterior SAT compartment (-11.4%±5.1% versus -9.5%±6.3%, p

Introduction: To investigate the feasibility of diffusion-weighted imaging (DWI) MRI for detecting pulmonary nodules at 1.5 Tesla in comparison with standard multidetector computed tomography (MDCT). Methods: Twenty patients with disseminated cancer disease in which MDCT had assured the presence of at least one pulmonary nodule were examined using a respiratory-gated DWI MR-sequence. Grey scale inverted source images and coronal maximum intensity projection (MIP) images were consensually analysed by two experienced radiologists. Size and location of any nodule detected were assessed. Additionally, the readers evaluated each hemithorax for the presence of at least one nodule and applied a four-point conspicuity scale (1-hemithorax definitely affected; 4-hemithorax definitely not affected). MDCT data served as reference. Results: At MDCT, a total of 71 pulmonary noduIes was found (size 3–5 mm, n = 16; 6–9 mm, n = 22; ≥10 mm, n = 33). For the DWI MR-sequence, a sensitivity of 86.4% was calculated for nodules ranging 6–9 mm and 97% for nodules ≥10 mm. In contrast, only 43.8% of lesions ≤5 mm was detected. The separate analysis of each hemithorax for the presence of at least one pulmonary nodule revealed a specificity rate, PPV and NPV of DWI-MR of 92.3%, 96% and 80%, respectively. Conclusions: The presented study is the first to confirm the diagnostic potential of DWI-MR in the detection of solid lung nodules. This technique allows for the detection of nodules ≥6 mm with reasonably high sensitivity rates (>86%). The observation of false positive findings decreases the accuracy of this approach compared with MDCT.

The purpose of this study was to assess the feasibility to determine fetal blood oxygen saturation (sO(2)) with T(2)-weighted MR sequences using a fetal sheep model. T(2) measurements were performed on a 1.5-T scanner using a T(2) preparation pulse in combination with a three-dimensional balanced steady-state free precession sequence repeated at different echo times. Eight sheep fetuses were examined during a control, hypoxic, and recovery phase to perform T(2)-weighted scans of the fetal blood in the heart. Signal intensities in the left and right ventricle were measured to calculate the MR blood sO(2). During each phase, fetal carotid artery sO(2) was directly measured and correlated with MR sO(2). A Bland-Altman plot was performed. Fetal carotid artery sO(2) was 69% sO(2) during control, 16% sO(2) during hypoxemia, and 67% sO(2) during recovery. Mean values of the MR sO(2) were 49% sO(2) and 40% sO(2) for control, 6% sO(2) and 3% sO(2) for hypoxemia, and 51% sO(2) and 43% sO(2) for recovery in left ventricle and right ventricle, respectively. Mean values of fetal carotid artery sO(2) and MR sO(2) were highly correlated (left ventricle: r = 0.87, right ventricle: r = 0.89). According to the Bland-Altman plot, MR sO(2) was lower compared to fetal carotid artery sO(2) (left ventricle: 15%, right ventricle: 20%). Based on our preliminary results, it seems to be possible to assess fetal sO(2) with MR oximetry.

To investigate the feasibility of fetal blood oxygen level-dependent magnetic resonance (MR) imaging at 1.5 T and to compare DeltaR2* in the brains of fetal sheep during hypoxia at 3.0 T with that at 1.5 T.All experimental protocols were reviewed and approved by the local authorities on animal protection. Between January 2006 and May 2006, fetal brain measurements were performed in eight pregnant ewes with 1.5-T and 3.0-T MR imaging units after fetal paralysis was achieved by administering pancuronium bromide. With both imaging units, a T2*-weighted single-shot gradient-echo echo-planar imaging sequence (echo time, 30 msec at 3.0 T and 50 msec at 1.5 T) was used to measure T2* signal changes (DeltaR2*) in the fetal brain in control conditions and during hypoxia (maternal oxygenation, 50%-70%). A carotid catheter was placed and maintained in the fetuses to enable measurement of the fetal arterial oxygen saturation (SaO(2)). DeltaR2* was correlated with fetal SaO(2), and linear regression analysis was performed. A paired t test was used to evaluate differences, with a significance level of P.05.At both field strengths, a signal intensity decrease on T2*-weighted images during hypoxia was detected. At 1.5 T, mean fetal SaO(2) was reduced from 65.4% +/- 9.2 (standard deviation) during control conditions to 17.7% +/- 6.2 during hypoxia. DeltaR2* and fetal SaO(2) correlated significantly (r = 0.98, P = .018). At 3.0 T, fetal SaO(2) was reduced from 62.4% +/- 7.5 during control conditions to 18% +/- 7.5 during hypoxia. DeltaR2* and fetal SaO(2) also correlated significantly (r = 0.95, P = .012). A linear fit resulted in a slope value of 0.084 +/- 0.003 for 1.5 T and 0.166 +/- 0.016 for 3.0 T. This means a doubled sensitivity of DeltaR2* for oxygen saturation variations at 3.0 T compared with 1.5 T.MR imaging at 3.0 T is more sensitive than that at 1.5 T in the detection of DeltaR2* in the fetal brain during hypoxia. However, there was a signal decrease in the fetal brain in all 1.5-T experiments during hypoxia. Thus it is possible to measure fetal DeltaR2* at 1.5 T, which may be of more practical relevance for the evaluation of pregnant women.

The purpose of this prospective study was to determine the oxygen saturation of blood in the fetal brain based on T2 and T2* measurements in a fetal sheep model. Five sheep fetuses were investigated during normoxia and hypoxia by 3T MRI. Multi-echo gradient-echo and turbo-spin-echo sequences were performed on the fetal brain. MR-determined oxygen saturation (MR-sO(2)) of blood in the fetal brain was calculated based on T2 and T2* values. Fetal arterial blood oxygen saturation (blood-sO(2)) was measured during the two experimental phases. The slope of MR-sO(2) as a function of blood-sO(2) was estimated and tested for compatibility using the one-sample t-test. During normoxia, mean values for carotid blood oxygen saturation were 67%, 83 ms for T2*, 202 ms for T2 and 96% for MR-sO(2). During hypoxia, arterial blood oxygen saturation, T2* and calculated MR-sO(2) decreased to 22%, 64 ms, and 68% respectively. The one-sample t-test revealed the slope to be significantly different from 0 (T = 5.023, df = 4, P = 0.007). It is feasible to perform quantitative T2 and T2* measurements in the fetal brain. MR-sO(2) and fetal arterial blood oxygen saturation correlated significantly. However, based on these data a reliable quantification of fetal brain tissue oxygenation is not possible.