Purpose To evaluate feasibility and reproducibility of liver diffusion‐weighted (DW) MRI using cardiac‐motion‐robust, blood‐suppressed, reduced‐distortion techniques. Methods DW‐MRI data were acquired at 3T in an anatomically accurate liver phantom including controlled pulsatile motion, in eight healthy volunteers and four patients with known or suspected liver metastases. Standard monopolar and motion‐robust (M1‐nulled, and M1‐optimized) DW gradient waveforms were each acquired with single‐shot echo‐planar imaging (ssEPI) and multishot EPI (msEPI). In the motion phantom, apparent diffusion coefficient (ADC) was measured in the motion‐affected volume. In healthy volunteers, ADC was measured in the left and right liver lobes separately to evaluate ADC reproducibility between the two lobes. Image distortions were quantified using the normalized cross‐correlation coefficient, with an undistorted T2‐weighted reference. Results In the motion phantom, ADC mean and SD in motion‐affected volumes substantially increased with increasing motion for monopolar waveforms. ADC remained stable in the presence of increasing motion when using motion‐robust waveforms. M1‐optimized waveforms suppressed slow flow signal present with M1‐nulled waveforms. In healthy volunteers, monopolar waveforms generated significantly different ADC measurements between left and right liver lobes (p=0.0078$$ p=0.0078 $$, reproducibility coefficients (RPC) = 470prefix×10prefix−6$$ 470\times 1{0}^{-6} $$ mm2$$ {}^2 $$/s for monopolar‐msEPI), while M1‐optimized waveforms showed more reproducible ADC values (p=0.29$$ p=0.29 $$, RPC=220prefix×10prefix−6$$ \mathrm{RPC}=220\times 1{0}^{-6} $$ mm2$$ {}^2 $$/s for M1‐optimized‐msEPI). In phantom and healthy volunteer studies, motion‐robust acquisitions with msEPI showed significantly reduced image distortion (p<0.001$$ p<0.001 $$) compared to ssEPI. Patient scans showed reduction of wormhole artifacts when combining M1‐optimized waveforms with msEPI. Conclusion Synergistic effects of combined M1‐optimized diffusion waveforms and msEPI acquisitions enable reproducible liver DWI with motion robustness, blood signal suppression, and reduced distortion.

A case of congenitally corrected transposition of the great arteries in a 64-old-woman is presented. Diagnosis was missed by invasive angiocardiography. Electrocardiographic-gated multislice computed tomography not only demonstrated switching of the aortic root and pulmonary trunk but clearly identified fine morphologic details of the cardiac chambers, including the atypical coronary artery pattern.

Background 3D chemical shift‐encoded (CSE)‐MRI techniques enable assessment of ferumoxytol concentration but are unreliable in the presence of motion. Purpose To evaluate a motion‐robust 2D‐sequential CSE‐MRI for R2* and B0 mapping in ferumoxytol‐enhanced MRI of the placenta. Study Type Prospective. Animal Model Pregnant rhesus macaques. Field Strength/Sequence 3.0T/CSE‐MRI. Assessment 2D‐sequential CSE‐MRI was compared with 3D respiratory‐gated CSE‐MRI in placental imaging of 11 anesthetized animals at multiple timepoints before and after ferumoxytol administration, and in ferumoxytol phantoms (0 μg/mL–440 μg/mL). Motion artifacts of CSE‐MRI in 10 pregnant women without ferumoxytol administration were assessed retrospectively by three blinded readers (4‐point Likert scale). The repeatability of CSE‐MRI in seven pregnant women was also prospectively studied. Statistical Tests Placental R2* and boundary B0 field measurements (ΔB0) were compared between 2D‐sequential and 3D respiratory‐gated CSE‐MRI using linear regression and Bland–Altman analysis. Results In phantoms, a slope of 0.94 (r2 = 0.99, concordance correlation coefficient ρ = 0.99), and bias of –4.8 s‐1 (limit of agreement [LOA], –41.4 s‐1, +31.8 s‐1) in R2*, and a slope of 1.07 (r2 = 1.00, ρ = 0.99) and bias of 11.4 Hz (LOA –12.0 Hz, +34.8 Hz) in ΔB0 were obtained in 2D CSE‐MRI compared with 3D CSE‐MRI for reference R2* ≤390 s‐1. In animals, a slope of 0.92 (r2 = 0.97, ρ = 0.98) and bias of –2.2 s‐1 (LOA –55.6 s‐1, +51.3 s‐1) in R2*, and a slope of 1.05 (r2 = 0.95, ρ = 0.97) and bias of 0.4 Hz (LOA –9.0 Hz, +9.7 Hz) in ΔB0 were obtained. In humans, motion‐impaired R2* maps in 3D CSE‐MRI (Reader 1: 1.8 ± 0.6, Reader 2: 1.3 ± 0.7, Reader 3: 1.9 ± 0.6), while 2D CSE‐MRI was motion‐free (Reader 1: 2.9 ± 0.3, Reader 2: 3.0 ± 0, Reader 3: 3.0 ± 0). A mean difference of 0.66 s‐1 and coefficient of repeatability of 9.48 s‐1 for placental R2* were observed in the repeated 2D CSE‐MRI. Data Conclusion 2D‐sequential CSE‐MRI provides accurate R2* and B0 measurements in ferumoxytol‐enhanced placental MRI of animals in the presence of respiratory motion, and motion‐robustness in human placental imaging. Level of Evidence: 1 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2020;51:580–592.

Objectives To evaluate the reproducibility of liver R2* measurements between a 2D cardiac ECG-gated and a 3D breath-hold liver CSE-MRI acquisition for liver iron quantification. Methods A total of 54 1.5 T MRI exams from 51 subjects (18 women, 36 men, age 35.2 ± 21.8) were included. These included two sub-studies with 23 clinical MRI exams from 19 patients identified retrospectively, 24 participants with known or suspected iron overload, and 7 healthy volunteers acquired prospectively. The 2D cardiac and the 3D liver R2* maps were acquired in the same exam. Either acquisitions were reconstructed using a complex R2* algorithm that accounts for the presence of fat and residual phase errors due to eddy currents. Data were analyzed using colocalized ROIs in the liver. Results Linear regression analysis demonstrated high Pearson’s correlation and Lin’s concordance coefficient for the overall study and both sub-studies. Bland–Altman analysis also showed good agreement, except for a slight increase of the mean R2* value above ~ 400 s−1. The Kolmogorow–Smirnow test revealed a non-normal distribution for (R2* 3D–R2* 2D) values from 0 to 600 s−1 in contrast to the 0–200 s−1 and 0–400 s−1 subpopulations. Linear regression analysis showed no relevant differences other than the intercept, likely due to only 7 measurements above 400 s−1. Conclusions The results demonstrate that R2*-measurements in the liver are feasible using 2D cardiac R2* maps compared to 3D liver R2* maps as the reference. Liver R2* may be underestimated for R2* > 400 s−1 using the 2D cardiac R2* mapping method.