Free-breathing dynamic liver examination using a radial 3D T1-weighted gradient echo sequence with moderate undersampling for patients with limited breath-holding capacity

PurposeTo compare free-breathing radial VIBE with moderate undersampling (us-radial-VIBE) with a standard breathhold T1-weighted volumetric interpolated sequence (3D GRE VIBE) in patients unable to suspend respiration during dynamic liver examination.Material and methods23 consecutive patients underwent dynamic liver MR examination using the free-breathing us-radial-VIBE sequence as part of their oncologic follow-up. All patients were eligible for the free-breathing protocol due to severe respiratory artifacts at the planning or precontrast sequences. The us-radial-VIBE acquisitions were compared to the patientś last staging liver MRI including a standard breathhold 3D GRE VIBE.For an objective image evaluation, signal intensity (SI), image noise (IN), signal-to-noise ratio (SNR) and contrast-enhancement ratio (CER) were compared. Representative image quality parameters, including typical artifacts were independently, retrospectively and blindly scored by four readers.ResultsUs-radial-VIBE had significant lower SNR (p < 0.0001) and higher IN (p < 0.0001), whereas SI did not differ (p = 0.62). Temporal resolution assessed with CER in the arterial phase showed higher values for us-radial-VIBE (p = 0.028). Subjective image quality parameters received generally slightly higher scores for 3D GRE VIBE. In a smaller subgroup comprising patients with severe respiratory artifacts also at reference breathhold 3D GRE VIBE examination, us-radial-VIBE showed significantly higher image quality scores. Furthermore, there were generally more severe respiratory artifacts in 3D GRE VIBE, whereas streaking was characteristic in almost all us-radial-VIBE acquisitions but did not affect diagnostic validity.ConclusionFree-breathing dynamic liver imaging using us-radial-VIBE delivers accurate temporal resolution, low motion artifact susceptibility and good image quality and represents a promising alternative in patients unable to suspend respiration.     

Free-breathing dynamic contrast-enhanced MRI of the abdomen and chest using a radial gradient echo sequence with K-space weighted image contrast (KWIC)

Objectives

To evaluate the feasibility of free-breathing, dynamic contrast-enhanced (DCE) MRI of the abdomen and thorax using the radial-gradient-echo sequence with k-space weighted image contrast (KWIC) reconstruction.

Methods

Institutional review board approval was obtained. Fourteen patients underwent free-breathing radial DCE-MRI. Radial MRI yielded full-frame images by gridding all k-space data and time-resolved subframe images by using KWIC reconstruction technique. Using subframe KWIC images, voxel-wise perfusion maps were created. For comparison, the breath-hold conventional Cartesian 3D-gradient-echo sequence (VIBE) was also performed during the equilibrium phase. The image qualities of radial and conventional VIBE images were compared quantitatively and qualitatively.

Results

Radial DCE-MRI provided high spatial resolution (1.4?×?1.4 mm) and temporal resolution (4.1 s for subframe images) allowing voxel-wise perfusion mapping with negligible motion or streaking artefacts. There were no significant differences in SNR between full-frame radial images and conventional VIBE images (79.08 vs 74.80, P?>?0.05). Overall image quality score of full-frame radial images was slightly lower than that of conventional VIBE images (3.88?±?0.59 vs. 4.31?±?0.97, P?<?0.05), but provided clinically useful images.

Conclusions

The free-breathing radial DCE-MRI can provide high spatial and temporal resolution while maintaining reasonably high image quality and thus is a feasible technique for DCE-MRI in the abdomen and thorax.

Key Points

? Dynamic contrast-enhanced magnetic resonance imaging (DCE) MRI is important in oncological imaging ? Radial MRI with k-space weighted image contrast (KWIC) reconstruction offers potential improvements ? Radial DCE-MRI provides good image quality, reduced artefacts and high spatial/temporal resolution     

Free-breathing contrast-enhanced T1-weighted gradient-echo imaging with radial k-space sampling for paediatric abdominopelvic MRI

Objective

To compare the image quality of contrast-enhanced abdominopelvic 3D fat-suppressed T1-weighted gradient-echo imaging with radial and conventional Cartesian k-space acquisition schemes in paediatric patients.

Methods

Seventy-three consecutive paediatric patients were imaged at 1.5 T with sequential contrast-enhanced T1-weighted Cartesian (VIBE) and radial gradient echo (GRE) acquisition schemes with matching parameters when possible. Cartesian VIBE was acquired as a breath-hold or as free breathing in patients who could not suspend respiration, followed by free-breathing radial GRE in all patients. Two paediatric radiologists blinded to the acquisition schemes evaluated multiple parameters of image quality on a five-point scale, with higher score indicating a more optimal examination. Lesion presence or absence, conspicuity and edge sharpness were also evaluated. Mixed-model analysis of variance was performed to compare radial GRE and Cartesian VIBE.

Results

Radial GRE had significantly (all P?<?0.001) higher scores for overall image quality, hepatic edge sharpness, hepatic vessel clarity and respiratory motion robustness than Cartesian VIBE. More lesions were detected on radial GRE by both readers than on Cartesian VIBE, with significantly higher scores for lesion conspicuity and edge sharpness (all P?<?0.001).

Conclusion

Radial GRE has better image quality and lesion conspicuity than conventional Cartesian VIBE in paediatric patients undergoing contrast-enhanced abdominopelvic MRI.

Key Points

? Numerous techniques are required to provide optimal MR images in paediatric patients. ? Radial free-breathing contrast-enhanced acquisition demonstrated excellent image quality. ? Image quality and lesion conspicuity were better with radial than Cartesian acquisition. ? More lesions were detected on contrast-enhanced radial than on Cartesian acquisition. ? Radial GRE can be used for performing abdominopelvic MRI in paediatric patients.     

Protocol optimization for cardiac and liver iron content assessment using MRI: What sequence should I use?

ObjectiveTo determine the optimal MRI protocol and sequences for liver and cardiac iron estimation in children.MethodsWe evaluated patients ≤18 years with cardiac and liver MRIs for iron content estimation. Liver T2 was determined by a third-party company. Cardiac and Liver T2* values were measured by an observer. Liver T2* values were calculated using the available liver parenchyma in the cardiac MRI. Linear correlations and Bland-Altman plots were run between liver T2 and T2*, cardiac T2* values; and liver T2* on dedicated cardiac and liver MRIs.Results139 patients were included. Mean liver T2 and T2* values were 8.6 ± 5.4 ms and 4.5 ± 4.1 ms, respectively. A strong correlation between liver T2 and T2* values was observed (r = 0.96, p < 0.001) with a bias (+4.1 ms). Mean cardiac bright- and dark-blood T2* values were 26.5 ± 12.9 ms and 27.2 ± 11.9 ms, respectively. Cardiac T2* values showed a strong correlation (r = 0.81, p < 0.001) with a low bias (−1.0 ms). The mean liver T2* on liver and cardiac MRIs were 4.9 ± 4.7 ms and 4.6 ± 3.9 ms, respectively. A strong correlation between T2* values was observed (r = 0.96, p < 0.001) with a small bias (−0.2 ms).ConclusionMRI protocols for iron concentration in the liver and the heart can be simplified to avoid redundant information and reduce scan time. In most patients, a single breath-hold GRE sequence can be used to evaluate the iron concentration in both the liver and heart.     

Intra-individual comparison of CAIPIRINHA VIBE technique with conventional VIBE sequences in contrast-enhanced MRI of focal liver lesions

PurposeTo evaluate the impact of controlled aliasing in parallel imaging results in higher acceleration (CAIPIRINHA) volume interpolated breath-hold examination (VIBE) magnetic resonance imaging (MRI) technique on image quality, reader confidence, and inter-observer agreement for the assessment of focal liver lesions in comparison with the standard VIBE approach.Material and methodsIn this IRB-approved intra-individual comparison study, abdominal arterial and portal-venous contrast-enhanced MRI studies were retrospectively analyzed in 38 patients with malignant liver lesions. Each patient underwent both CAIPIRINHA and conventional VIBE 3 T MRI within 3 months, showing stable disease. Images were evaluated using 5-point rating scales by two blinded radiologists with more than 20 and 5 years of experience in MRI, respectively. Readers scored dignity of liver lesions and assessed which liver segments were affected by malignancy (ranging from 1 = definitely benign/not affected to 5 = definitely malignant/affected by malignancy). Readers also rated overall image quality, sharpness of intrahepatic veins, and diagnostic confidence (ranging from 1 = poor to 5 = excellent).ResultsReviewers achieved a higher inter-observer reliability using CAIPIRINHA when they reported which liver segments were affected by malignancy compared to traditional VIBE series (κ = 0.62 and 0.54, respectively, p < 0.05). Similarly, CAIPIRINHA showed a slightly higher inter-rater agreement for the dignity of focal liver lesions versus the standard VIBE images (κ = 0.50 and 0.49, respectively, p < 0.05). CAIPIRINHA series also scored higher in comparison to standard VIBE sequences (mean scores: image quality, 4.2 and 3.5; sharpness of intrahepatic vessels, 3.8 and 3.2, respectively, p < 0.05) for both reviewers and allowed for higher subjective diagnostic confidence (ratings, 3.8 and 3.2, respectively, p < 0.05).ConclusionCompared to the standard VIBE approach, CAIPIRINHA VIBE technique provides improved image quality and sharpness of intrahepatic veins, as well as higher diagnostic confidence. Additionally, this technique allows for higher inter-observer agreement when reporting focal liver lesions for both dignity and allocation.     

Improved clinical workflow for simultaneous whole-body PET/MRI using high-resolution CAIPIRINHA-accelerated MR-based attenuation correction

PurposeTo explore the value and reproducibility of a novel magnetic resonance based attenuation correction (MRAC) using a CAIPIRINHA-accelerated T1-weighted Dixon 3D-VIBE sequence for whole-body PET/MRI compared to the clinical standard.MethodsThe PET raw data of 19 patients from clinical routine were reconstructed with standard MRAC (MRAC_std) and the novel MRAC (MRAC_caipi), a prototype CAIPIRINHA accelerated Dixon 3D-VIBE sequence, both acquired in 19 s/bed position. Volume of interests (VOIs) for liver, lung and all voxels of the total image stack were created to calculate standardized uptake values (SUV_mean) followed by inter-method agreement (Passing-Bablok regression, Bland-Altman analysis). A voxel-wise SUV comparison per patient was performed for intra-individual correlation between MRAC_std and MRAC_caipi. Difference images (MRAC_std-MRAC_caipi) of attenuation maps and SUV images were calculated. The image quality of in/opposed-phase water and fat images obtained from MRAC_caipi was assessed by two readers on a 5-point Likert-scale including intra-class coefficients for inter-reader agreement.ResultsSUV_mean correlations of VOIs demonstrated high linearity (0.95 < Spearman’s rho < 1, p < 0.0001, respectively), substantiated by voxel-wise SUV scatter-plots (1.79 × 10⁸ pixels). Outliers could be explained by different physiological conditions between the scans such as different segmentation of air-containing tissue, lungs, kidneys, metal implants, diaphragm edge or small air bubbles in the gastrointestinal tracts that moved between MRAC acquisitions. Nasal sinuses and the trachea were better segmented in MRAC_caipi. High-resolution T1w Dixon 3D VIBE images were acquired in all cases and could be used for PET/MRI fusion. MRAC_caipi images were of high diagnostic quality (4.2 ± 0.8) with 0.92-0.96 intra-class correlation.ConclusionsThe novel prototype MRAC_caipi extends the value for attenuation correction by providing a high spatial resolution DIXON-based dataset suited for diagnostic assessment towards time-efficient whole-body PET/MRI.     

Free-breathing radial volumetric interpolated breath-hold examination vs breath-hold cartesian volumetric interpolated breath-hold examination magnetic resonance imaging of the liver at 1.5T

AIMTo compare breath-hold cartesian volumetric interpolated breath-hold examination (cVIBE) and free-breathing radial VIBE (rVIBE) and determine whether rVIBE could replace cVIBE in routine liver magnetic resonance imaging (MRI).METHODSIn this prospective study, 15 consecutive patients scheduled for routine MRI of the abdomen underwent pre- and post-contrast breath-hold cVIBE imaging (19 s acquisition time) and free-breathing rVIBE imaging (111 s acquisition time) on a 1.5T Siemens scanner. Three radiologists with 2, 4, and 8 years post-fellowship experience in abdominal imaging evaluated all images. The radiologists were blinded to the sequence types, which were presented in a random order for each patient. For each sequence, the radiologists scored the cVIBE and rVIBE images for liver edge sharpness, hepatic vessel clarity, presence of artifacts, lesion conspicuity, fat saturation, and overall image quality using a five-point scale.RESULTSCompared to rVIBE, cVIBE yielded significantly (P < 0.001) higher scores for liver edge sharpness (mean score, 3.87 vs 3.37), hepatic-vessel clarity (3.71 vs 3.18), artifacts (3.74 vs 3.06), lesion conspicuity (3.81 vs 3.2), and overall image quality (3.91 vs 3.24). cVIBE and rVIBE did not significantly differ in quality of fat saturation (4.12 vs 4.03, P = 0.17). The inter-observer variability with respect to differences between rVIBE and cVIBE scores was close to zero compared to random error and inter-patient variation. Quality of rVIBE images was rated as acceptable for all parameters.CONCLUSIONrVIBE cannot replace cVIBE in routine liver MRI. At 1.5T, free-breathing rVIBE yields acceptable, although slightly inferior image quality compared to breath-hold cVIBE.     

Retrospective Assessment of the Impact of Primary Language Video Instructions on Image Quality of Abdominal MRI

PurposeTo assess the impact of instructional videos in patients’ primary language on abdominal MR image quality for whom English is a second language (ESL).MethodsTwenty-nine ESL patients viewed Spanish or Mandarin Chinese instructional videos (approximately 2.5 min in duration) in the preparation room before abdominal MRI (ESL–video group). Comparison groups included 50 ESL patients who underwent MRI before video implementation (ESL–no video group) and 81 English-speaking patients who were matched for age, sex, magnet strength, and history of prior MRI with patients in the first two groups. Three radiologists independently assessed respiratory motion and image quality on turbo spin-echo T2-weighted images (T2WI) and postcontrast T1-weighted images (T1WI) using 1 to 5 Likert scales. Groups were compared using Kruskal-Wallis tests as well as generalized estimating equations (GEEs) to adjust for possible confounders.ResultsFor T2WI respiratory motion and T2WI overall image quality, Likert scores of the ESL–no video group (mean score across readers of 2.6 ± 0.1 and 2.6 ± 0.1) were lower (all P < .001) compared with English-speaking (3.3 ± 0.2 and 3.3 ± 0.1) and ESL–video (3.2 ± 0.1 and 3.0 ± 0.2) groups. In the GEE model, mean T2WI respiratory motion (both adjusted P < .001) and T2WI overall quality (adjusted P = .03 and .11) were higher in English and ESL–video groups compared with ESL–no video group. For T1WI respiratory motion and T1WI overall image quality, Likert scores were not different between groups (P > .05), including in the GEE model (adjusted P > .05).ConclusionProviding ESL patients with an instructional video in their primary language before abdominal MRI is an effective intervention to improve imaging quality.     

Validation of MRI to TRUS registration for high-dose-rate prostate brachytherapy

PurposeThe objective of this study was to develop and validate an open-source module for MRI to transrectal ultrasound (TRUS) registration to support tumor-targeted prostate brachytherapy.Methods and MaterialsIn this study, 15 patients with prostate cancer lesions visible on multiparametric MRI were selected for the validation. T2-weighted images with 1-mm isotropic voxel size and diffusion weighted images were acquired on a 1.5T Siemens imager. Three-dimensional (3D) TRUS images with 0.5-mm slice thickness were acquired. The investigated registration module was incorporated in the open-source 3D Slicer platform, which can compute rigid and deformable transformations. An extension of 3D Slicer, SlicerRT, allows import of and export to DICOM-RT formats. For validation, similarity indices, prostate volumes, and centroid positions were determined in addition to registration errors for common 3D points identified by an experienced radiation oncologist.ResultsThe average time to compute the registration was 35 ± 3 s. For the rigid and deformable registration, respectively, Dice similarity coefficients were 0.87 ± 0.05 and 0.93 ± 0.01 while the 95% Hausdorff distances were 4.2 ± 1.0 and 2.2 ± 0.3 mm. MRI volumes obtained after the rigid and deformable registration were not statistically different (p > 0.05) from reference TRUS volumes. For the rigid and deformable registration, respectively, 3D distance errors between reference and registered centroid positions were 2.1 ± 1.0 and 0.4 ± 0.1 mm while registration errors between common points were 3.5 ± 3.2 and 2.3 ± 1.1 mm. Deformable registration was found significantly better (p < 0.05) than rigid registration for all parameters.ConclusionsAn open-source MRI to TRUS registration platform was validated for integration in the brachytherapy workflow.     

3 Tesla MRI in diagnosis and follow up of children with pneumonia

PurposeTo investigate the utilization of 3-Tesla (3 T) magnetic resonance imaging (MRI) in detection of pulmonary abnormalities in children with pneumonia.Materials and methodsForty-seven children with pneumonia prospectively underwent 3 T thoracic MRI and posteroanterior (PA) chest radiography (CR). Of these, 15 patients also underwent contrast-enhanced thorax computed tomography (CT) or high-resolution CT (HRCT). The MRI protocol included axial and coronal T2-weighted spectral presaturation with inversion recovery (SPIR) Multivane-XD and axial echo-planar diffusion-weighted imaging (EPI DWI) with respiratory gating. Kappa statistics, Cochran Q, and McNemar tests were used to investigate the results.ResultsAgreement between CR and MRI was substantial in detecting consolidation/infiltration (k = 0.64), peribronchial thickening (k = 0.64), and bronchiectasis (k = 1); moderate in detecting cavity (k = 0.54) and pleural effusion (k = 0.44); and fair in detecting empyema (0.32) and bilateral involvement of lungs (k = 0.23). MRI was superior to CR in detecting bilateral involvement (p < 0.001), lymph node (p < 0.001), pleural effusion (p < 0.001), and empyema (p = 0.003). MRI detected all the consolidation/infiltration also detected on CT imaging. A kappa test showed moderate agreement between MRI and CT in detecting pleural effusion and ground-glass opacity (GGO), and substantial or almost perfect agreement for all other pathologies. No statistically significant difference was observed between MRI and CT for detecting pneumonia-associated pathologies by the McNemar test.ConclusionThoracic 3 T MRI is an accurate and effective technique for evaluating children with pneumonia. MRI detected more pathologies than CR and had similar results to those of thorax CT.     

Time to enhancement derived from ultrafast breast MRI as a novel parameter to discriminate benign from malignant breast lesions

ObjectivesTo investigate time to enhancement (TTE) as novel dynamic parameter for lesion classification in breast magnetic resonance imaging (MRI).MethodsIn this retrospective study, 157 women with 195 enhancing abnormalities (99 malignant and 96 benign) were included. All patients underwent a bi-temporal MRI protocol that included ultrafast time-resolved angiography with stochastic trajectory (TWIST) acquisitions (1.0 × 0.9 × 2.5 mm, temporal resolution 4.32 s), during the inflow of contrast agent. TTE derived from TWIST series and relative enhancement versus time curve type derived from volumetric interpolated breath-hold examination (VIBE) series were assessed and combined with basic morphological information to differentiate benign from malignant lesions. Receiver operating characteristic analysis and kappa statistics were applied.ResultsTTE had a significantly better discriminative ability than curve type (p < 0.001 and p = 0.026 for reader 1 and 2, respectively). Including morphology, sensitivity of TWIST and VIBE assessment was equivalent (p = 0.549 and p = 0.344, respectively). Specificity and diagnostic accuracy were significantly higher for TWIST than for VIBE assessment (p < 0.001). Inter-reader agreement in differentiating malignant from benign lesions was almost perfect for TWIST evaluation (κ = 0.86) and substantial for conventional assessment (κ = 0.75).ConclusionsTTE derived from ultrafast TWIST acquisitions is a valuable parameter that allows robust differentiation between malignant and benign breast lesions with high accuracy.     

Novel use of ViewRay MRI guidance for high-dose-rate brachytherapy in the treatment of cervical cancer

PurposeTo characterize image quality and feasibility of using ViewRay MRI (VR)–guided brachytherapy planning for cervical cancer.Methods and MaterialsCervical cancer patients receiving intracavitary brachytherapy with tandem and ovoids, planned using 0.35T VR MRI at our institution, were included in this series. The high-risk clinical target volume (HR-CTV), visible gross tumor volume, bladder, sigmoid, bowel, and rectum contours for each fraction of brachytherapy were evaluated for dosimetric parameters. Typically, five brachytherapy treatments were planned using the T2 sequence on diagnostic MRI for the first and third fractions, and a noncontrast true fast imaging with steady-state precession sequence on VR or CT scan for the remaining fractions. Most patients received 5.5 Gy × 5 fractions using high-dose-rate Ir-192 following 45 Gy of whole-pelvis radiotherapy. The plan was initiated at 5.5 Gy to point A and subsequently optimized and prescribed to the HR-CTV. The goal equivalent dose in 2 Gy fractions for the combined external beam and brachytherapy dose was 85 Gy. Soft-tissue visualization using contrast-to-noise ratios to distinguish normal tissues from tumor at their interface was compared between diagnostic MRI, CT, and VR.ResultsOne hundred and forty-two fractions of intracavitary brachytherapy were performed from April 2015 to January 2017 on 29 cervical cancer patients, ranging from stages IB1 to IVA. The median HR-CTV was 27.78 cc, with median D₉₀ HR-CTV of 6.1 Gy. The median time from instrument placement to start of treatment using VR was 65 min (scan time 2 min), compared to 105 min using diagnostic MRI (scan time 11 min) (t-test, p < 0.01). The contrast-to-noise ratio of tumor to cervix in both diagnostic MRI and VR had significantly higher values compared to CT (ANOVA and t-tests, p < 0.01).ConclusionsWe report the first clinical use of VR-guided brachytherapy. Time to treatment using this approach was shorter compared to diagnostic MRI. VR also provided significant advantage in visualizing the tumor and cervix compared to CT. This presents a feasible and reliable manner to image and plan gynecologic brachytherapy.     

Investigation of myocardial extracellular volume fraction in heart failure patients using iodine map with rapid-kV switching dual-energy CT: Segmental comparison with MRI T1 mapping

PurposeTo measure myocardial extracellular volume fraction (ECV) for each region or segment using iodine density image (IDI) with single-source dual-energy computed tomography (DECT) and compare the results with an MRI T1 mapping approach.Materials and methodsFor this prospective study, 79 consecutive heart failure patients referred for MRI were included and 23 patients (14 men, 63 ± 14 years) who underwent both MRI and late contrast enhancement DECT following coronary CT angiography were evaluated. CT-ECV was computed from IDI using late acquisition projection data. MR-ECV was computed from native and post-contrast T1 maps using non-rigid image registration for segments with evaluable image quality from 3.0-T MRI. Regional CT-ECV and MR-ECV were measured based on 16-segment models. CT-ECV and MR-ECV were compared using Pearson correlations. Agreement among methods was assessed using Bland-Altman comparisons.ResultsIn the 368 segments, although all segments were evaluable on IDI, 37 segments were rated as non-evaluable on T1 maps. Overall, 331 segments were analyzed. Mean CT-ECV and MR-ECV were 31.6 ± 9.1 and 33.2 ± 9.1, respectively. Strong correlations were seen between CT-ECV and MR-ECV for each region, as follows: all segments, r = 0.837; septal, r = 0.871; mid-septal, r = 0.895; anterior, r = 0.869; inferior, r = 0.793; and lateral, 0.864 (all p < 0.001). Differences between CT-ECV and MR-ECV were as follows: all segments, 1.13 ± 4.98; septal, −1.51 ± 4.37; mid-septal, −1.85 ± 4.22; anterior, 2.54 ± 4.89; inferior, 1.2 ± 5.78; and lateral, 2.65 ± 3.98.ConclusionECV using DECT and from cardiac MRI showed a strong correlation on regional and segmental evaluations. DECT is useful for characterizing myocardial ECV changes as well as MRI.     

Feasibility of self-gated isotropic radial late-phase MR imaging of the liver

Objective

To evaluate feasibility of a 3D-isotropic self-gated radial volumetric interpolated breath-hold examination (VIBE) for late-phase MRI of the liver.

Material and methods

70 patients were included and underwent liver MRI at 1.5 T. Depending on the diagnosis, either Gd-EOB-DTPA (35 patients) or gadobutrol (35 patients) were administered. During late (gadobutrol) or hepatocyte-specific phase (Gd-EOB-DTPA), a radial prototype sequence was acquired and reconstructed using (1) self-gating with 40 % acceptance (rVIBE₄₀); (2) with 100 % acceptance of the data (rVIBE₁₀₀) and compared to Cartesian VIBE (cVIBE). Images were assessed qualitatively (image quality, lesion conspicuity, artefacts; 5-point Likert-scale: 5?=?excellent; two independent readers) and quantitatively (coefficient-of-variation (CV); contrast-ratio) in axial and coronal reformations.

Results

In eight cases only rVIBE provided diagnostic image quality. Image quality of rVIBE₄₀ was rated significantly superior (p?<?0.05) in Gd-EOB-DTPA-enhanced and coronal reformatted examinations as compared to cVIBE. Lesion conspicuity was significantly improved (p?<?0.05) in coronal reformatted Gd-EOB-DTPA-enhanced rVIBE₄₀ in comparison to cVIBE. CV was higher in rVIBE₄₀ as compared to rVIBE₁₀₀/cVIBE (p?<?0.01). Gadobutrol-enhanced rVIBE₄₀ and cVIBE showed higher contrast-ratios than rVIBE₁₀₀ (p?<?0.001), whereas no differences were found in Gd-EOB-DTPA-enhanced examinations.

Conclusion

Self-gated 3D-isotropic rVIBE provides significantly superior image quality compared to cVIBE, especially in multiplanar reformatted and Gd-EOB-DTPA-enhanced examinations.

Key Points

? Radial VIBE acquisition reduces motion artefacts. ? Gd-EOB-DTPA-enhanced scans provide improved image quality. ? Non-diagnostic liver MRI examinations may be reduced by radial k-spaces sampling.

     

Chest MRI Using Multivane-XD,a Novel T2-Weighted Free Breathing MR Sequence

ObjectiveTo compare image quality of free-breathing T2-weighted MultiVane-XD (MVXD) sequence (non-Cartesian k-space filling using radial rectangular blades) with conventional MR sequences (short tau inversion recovery [STIR],balanced true field echo [BTFE], T1 in phase fast field echo [T1 FFE], and T1-fat saturated postgadolinium [T1PG]) in MR imaging of chest.Materials and MethodsTwenty-one patients (10 men and 11 women) underwent chest MRI including T2W MVXD, STIR, BTFE (18/21), T1 FFE, T1PG (10/21) sequences at 1.5 T. Two reviewers (A.S.B and M.J. with 20 and 10 years of experience in pulmonary imaging, respectively) evaluated each sequence with respect to overall image quality, image sharpness, definition of mediastinal vessels including the aorta, pulmonary arteries, superior vena cava, intrapulmonary vessels; trachea, main bronchi, intrapulmonary airways; lung-mediastinal interface, pulmonary lesion detection, and artefacts in the upper, middle, and lower third of chest using 5-point scales. No sedation was given. Pairwise comparisons between T2W MVXD and the 4 conventional sequences were made using unpaired student's t test.ResultsMean age of patients was 30.67 years (range: 6-60 years). T2 MVXD showed significantly better overall image quality and sharpness than STIR, T1 FFE, and T1PG (P < 0.01) while it was comparable to BTFE. Mediastinal vessels were significantly better visualized on T2 MVXD as compared to STIR and T1 (P < 0.003). However, BTFE and T1PG were superior to T2 MVXD for visualization of great vessels, SVC, and intrapulmonary vessels (P < 0.01). Visualization of trachea, major bronchi, intrapulmonary airways as well as intrapulmonary lesion detection was significantly better on T2 MVXD images in comparison to any of the other 4 sequences (P < 0.03). Intrapulmonary artifacts were significantly lesser in BTFE images as compared to T2 MVXD (P < 0.01). No significant difference was found between the severity of intrapulmonary artifacts in other MR sequences as compared to T2 MVXD.ConclusionsBy virtue of its better overall image quality, sharpness, superior visualization of mediastinal airways, and lesion detection, T2 MultiVane-XD promises to be a robust addition in the armamentarium of thoracic radiologists.     

Comparison of image quality of subtracted and nonsubtracted breath hold VIBE and free breathing GRASP in the evaluation of renal masses

ObjectiveTo compare the image quality of subtracted and nonsubtracted images obtained using volumetric interpolated breath-hold exam (VIBE) and free breathing T1 weighted Golden-angle Radial Sparse Parallel (GRASP).MethodsWe retrospectively evaluated 27 consecutive patients who underwent MRI for the evaluation of renal masses. Contrast enhanced VIBE and free breathing GRASP imaging were performed, and subtraction images generated. Two radiologists performed quantitative and qualitative evaluations of image quality of nonsubtracted and subtracted data sets. Statistical analysis was performed using the Wilcoxon signed-rank test, paired t-test and kappa statistics.ResultsVIBE images scored statistically higher for the following parameters in the coronal and axial plane: sharpness, streak artifact, image noise, and overall image quality for standard and subtracted images (all P values P < 0.001). GRASP images had significantly less subtraction artifact in the coronal (P = 0.042) plane with a similar trend in the axial plane (P = 0.079). Interreader Kappa values for qualitative images scores were fair to good (0.23–0.71). Quantitative subtracted GRASP images had significant less subtraction artifact compared to VIBE in the anterior-posterior (3.9 mm SD 2.6 mm versus 5.8 mm SD 3.6 mm, P = 0.010), and craniocaudal direction (4.4 mm SD 2.9 mm versus 7.0 mm SD 5.3 mm, P = 0.010); a trend was seen in the left-right direction (2.6 mm SD 1.4 mm versus 4.0 mm SD 3.9 mm, P = 0.084).ConclusionVIBE images have significantly better image quality than free breathing GRASP images, however free breathing GRASP images have significantly less subtraction artifact.     

Semi-quantitative myocardial perfusion MRI in heart transplant recipients at rest: repeatability in healthy controls and assessment of cardiac allograft vasculopathy

BackgroundCardiac Allograft Vasculopathy (CAV) is a major cause of chronic cardiac allograft failure. Invasive coronary angiography (ICA) and intravascular ultrasound (IVUS) are the current diagnostic methods. Myocardial perfusion MRI has become a promising non-invasive method to evaluate myocardial ischemia, but has not been thoroughly validated in CAV. Our objective was to assess the repeatability of myocardial rest-perfusion MRI in healthy volunteers and its feasibility in detecting CAV in transplant patients (Tx).MethodsTwelve healthy volunteers and twenty transplant patients beyond the first year post- transplant underwent cardiac MRI at 1.5 T at rest including first-pass perfusion imaging in short axis (base, mid, apex) after injection of gadolinium. Volunteers underwent repeated cardiac MRI on different days (interval = 15.6 ± 2.4 days) to assess repeatability. Data analysis included semi-automatic contouring of endocardial and epicardial borders of the left ventricle (LV) and quantification of peak perfusion, time-to-peak (TTP) perfusion, and upslope of the perfusion curve.ResultsBetween scans and re-scans in healthy volunteers, peak signal intensity, slope, and TTP demonstrated moderate agreement (ICC = 0.53, 0.48, and 0.59, respectively; all, p < .001). Peak signal intensity, slope, and TTP were moderately variable with COV values of 23%, 42%, and 35%, respectively. Peak perfusion was significantly reduced in CAV positive (n = 9 Tx patients) compared to CAV negative (n = 11 Tx patients) groups (90.7 ± 27.0 vs 139.5 ± 30.2, p < .001).ConclusionCardiac MRI is a moderately repeatable method for the semi-quantitative assessment of first-pass myocardial perfusion at rest. Semi-quantitative surrogate markers of LV perfusion could play a role in CAV detection.     

Contrast-enhanced free-breathing 3D T1-weighted gradient-echo sequence for hepatobiliary MRI in patients with breath-holding difficulties

Objective

Evaluate the image quality and diagnostic performance of a free-breathing 3D-gradient-echo sequence with radial acquisition (rGRE) compared with a Cartesian breath-hold 3D-GRE (cGRE) sequence on hepatobiliary phase MRI in patients with breath-holding difficulties.

Methods

Twenty-eight consecutive patients (15 males; mean age 61?±?11.9 years) were analysed in this retrospective IRB-approved study. Breath-holding difficulties during gadoxetate-disodium-enhanced liver MRI manifested as breathing artefacts during dynamic-phase imaging. MRI included axial and coronal cGRE and a radially sampled rGRE sequence during the hepatobiliary phase. Two radiologists independently evaluated cGRE and rGRE images for image quality, liver lesion detection and conspicuity, and bile duct conspicuity on a four-point scale.

Results

Liver edge sharpness was significantly higher on rGRE images (P?<?0.001). Overall image quality was slightly but significantly higher for rGRE than for cGRE (P?<?0.001 and P?=?0.039). Bile duct conspicuity scores of rGRE and cGRE were not significantly different. Sensitivity for detection of the 26 liver lesions was similar for rGRE and cGRE (81-77 % and 73-77 %, P?=?0.5 and 1.0). Lesion conspicuity scores were significantly higher for rGRE for one reader (P?=?0.012).

Conclusion

In patients with breath-holding difficulties, overall image quality and liver lesion conspicuity on hepatobiliary phase MRI can be improved using the rGRE sequence.

Key Points

? Patients with diminished breath-holding capacities present a major challenge in abdominal MRI. ? A free-breathing sequence for hepatobiliary-phase MRI can improve image quality. ? Further advances are needed to reduce acquisition time of the free-breathing gradient-echo sequence.     

Optical coherence tomography angiography findings in transfusion-dependent beta-thalassemia patients with and without splenectomy

BackgroundOcular involvement is common in transfusion-dependent beta-thalassemia (TDβ-T) patients. We aimed to investigate the effect of splenectomy on optical coherence tomography angiography (OCTA) findings in TDβ-T patients.MethodsThe study is a prospective cross-sectional study. A total of 45 eyes of 23 patients with splenectomy (34.04±8.83 years), 18 eyes of 9 patients without splenectomy (27.44±5.43 years), and 54 eyes of 27 controls (33.22±6.44 years) were included. Vessel density in superficial capillary plexus, deep capillary plexus and radial peripapillary capillary, foveal avascular zone, choriocapillaris flow area, choroidal and retinal thickness detected by OCTA were evaluated. p < 0.05 was considered significant.ResultsVessel density of superficial capillary plexus and deep capillary plexus were similar in patients with and without splenectomy, and controls. Choriocapillaris flow area was significantly decreased in patients with splenectomy than that in those without splenectomy and controls (2.02±0.12 vs. 2.17±0.1 and 2.14±0.12; p < 0.001). Choroidal thickness was significantly lower in patients without splenectomy than in patients with splenectomy and controls (260.05±61.02 vs. 305.11±42.13 and 298.89±29.14, p = 0.008). Parafoveal and perifoveal thickness of the full retina and outer retina were significantly lower in patients without splenectomy than in patients with splenectomy and controls (301.06±10.0, 279.78±10.28 vs. 311.04±14.89, 290.87±13.67 and 316.63±13.57, 289.56±9.31, p < 0.001 and p = 0.002; 174.72±7.81, 167.17±6.21 vs. 182.87±8.81, 173.60±7.09 and 185.11±9.26, 173.96±6.79, p = 0.001 and p < 0.001, respectively).ConclusionsOCTA findings can provide information about the microvascular effects of splenectomy on the retina of patients with TDβ-T.     

Utility of diffusion-weighted MRI in the diagnosis of bladder carcinoma

BackgroundThe purposes of our study were to investigate the feasibility of diffusion-weighted imaging in the detection of malignant bladder tumors, with comparison to the high-resolution thin-section fast spin-echo (FSE) T2-weighted MRI, and also to compare the apparent diffusion coefficient (ADC) values of the bladder tumors with the surrounding structures.Material and MethodsFifty-three consecutive patients consisting of 44 males and 9 females who presented with a bladder mass were prospectively enrolled in this study. Mean age was 62.53±12.03 (age range, 33–86 years). These patients were evaluated by high-resolution thin-section FSE T2-weighted and diffusion-weighted MRI for the detection of bladder masses. Following MRI, within 2 weeks, all patients were subjected to either surgery or cystoscopic biopsy, and the obtained histopathological proofs were used as the reference standard. Furthermore, ADC values of the bladder tumors, urine, the normal bladder wall, the central and peripheral zones of the prostate, the seminal vesicule, and the uterus outer myometrium were also calculated. ADC values of the bladder carcinomas and the related surrounding structures were compared as to whether a statistically significant difference was present or not.ResultsIn a total of 47 patients, consisting of 39 males and 8 females, bladder carcinomas were clearly shown as having conspicuous high and intermediate signal intensity masses, relative to the surrounding structures on diffusion-weighted and T2-weighted images, respectively. An 89% sensitivity and a 100% positive predictive value were obtained for both FSE T2-weighted and diffusion-weighted MRI in the diagnosis of bladder carcinoma. Mean ADC values and standard deviations of the bladder tumors and the surrounding structures were as follows: bladder carcinomas (n= 47): 1.28±0.31, normal bladder wall (n= 47): 1.98±0.41, urine (n= 47): 3.12±0.24, seminal vesicle (n= 39): 1.82±0.33, peripheral zone of prostate (n= 39): 1.80±0.29, central zone of prostate (n= 39): 1.55±0.33, and uterus outer myometrium (n= 8): 1.53±0.19. It can be clearly seen that the mean ADC values of the bladder carcinomas were significantly lower than the surrounding structures (P< .05).Conclus?onHigh-resolution thin-section FSE T2 and diffusion-weighted MRI show high diagnostic performance and are comparable in the detection of bladder tumors. Diffusion-weighted MRI provides high quality images of the malignant bladder tumors against a suppressed background signal. Diffusion-weighted MRI using ADC measurements may be useful in the evaluation of tumor invasion to the adjacent organs.