The collateral map: prediction of lesion growth and penumbra after acute anterior circulation ischemic stroke.

OBJECTIVES: This study evaluated the collateral map's ability to predict lesion growth and penumbra after acute anterior circulation ischemic strokes. METHODS: This was a retrospective analysis of selected data from a prospectively collected database. The lesion growth ratio was the ratio of the follow-up lesion volume to the baseline lesion volume on diffusion-weighted imaging (DWI). The time-to-maximum (Tmax)/DWI ratio was the ratio of the baseline Tmax > 6 s volume to the baseline lesion volume. The collateral ratio was the ratio of the hypoperfused lesion volume of the phase_FU (phase with the hypoperfused lesions most approximate to the follow-up DWI lesion) to the hypoperfused lesion volume of the phase_baseline of the collateral map. Multiple logistic regression analyses were conducted to identify independent predictors of lesion growth. The concordance correlation coefficients of Tmax/DWI ratio and collateral ratio for lesion growth ratio were analyzed. RESULTS: Fifty-two patients, including twenty-six males (mean age, 74 years), were included. Intermediate (OR, 1234.5; p < 0.001) and poor collateral perfusion grades (OR, 664.7; p = 0.006) were independently associated with lesion growth. Phase_FUs were immediately preceded phases of the phase_baselines in intermediate or poor collateral perfusion grades. The concordance correlation coefficients of the Tmax/DWI ratio and collateral ratio for the lesion growth ratio were 0.28 (95% CI, 0.17-0.38) and 0.88 (95% CI, 0.82-0.92), respectively. CONCLUSION: Precise prediction of lesion growth and penumbra can be possible using collateral maps, allowing for personalized application of recanalization treatments. Further studies are needed to generalize the findings of this study. CLINICAL RELEVANCE STATEMENT: Precise prediction of lesion growth and penumbra can be possible using collateral maps, allowing for personalized application of recanalization treatments. KEY POINTS: • Cell viability in cerebral ischemia due to proximal arterial steno-occlusion mainly depends on the collateral circulation. • The collateral map shows salvageable brain extent, which can survive by recanalization treatments after acute anterior circulation ischemic stroke. • Precise estimation of salvageable brain makes it possible to make patient-specific treatment decision.

Multiphase MR Angiography Collateral Map: Functional Outcome after Acute Anterior Circulation Ischemic Stroke.

Background Collateral circulation determines tissue fate and affects treatment result in acute ischemic stroke. A precise method for collateral estimation in an optimal imaging protocol is necessary to make an appropriate treatment decision for acute ischemic stroke. Purpose To verify the value of multiphase collateral imaging data sets (MR angiography collateral map) derived from dynamic contrast material-enhanced MR angiography for predicting functional outcomes after acute ischemic stroke. Materials and Methods This secondary analysis of an ongoing prospective observational study included data from participants with acute ischemic stroke due to occlusion or stenosis of the unilateral internal carotid artery and/or M1 segment of the middle cerebral artery who were evaluated within 8 hours of symptom onset. Data were obtained from March 2016 through August 2018. The collateral grading based on the MR angiography collateral map was estimated by using six-scale MR acute ischemic stroke collateral (MAC) scores. To identify independent predictors of favorable functional outcomes, age, sex, risk factors, baseline National Institutes of Health Stroke Scale (NIHSS) score, baseline diffusion-weighted imaging (DWI) lesion volume, site of steno-occlusion, collateral grade, mode of treatment, and early reperfusion were evaluated with multiple logistic regression analyses. Results One hundred fifty-four participants (mean age ± standard deviation, 69 years ± 13; 99 men) were evaluated. Younger age (odds ratio [OR], 0.45; 95% confidence interval [CI]: 0.29, 0.70; P < .001), lower baseline NIHSS score (OR, 0.85; 95% CI: 0.78, 0.94; P < .001), MAC score of 3 (OR, 27; 95% CI: 4.0, 179; P < .001), MAC score of 4 (OR, 17; 95% CI: 2.1, 134; P = .007), MAC score of 5 (OR, 27; 95% CI: 2.5, 306; P = .007), and successful early reperfusion (OR, 7.5; 95% CI: 2.6, 22; P < .001) were independently associated with favorable functional outcomes in multivariable analysis. There was a linear negative association between collateral perfusion grades and functional outcomes (P < .001). Conclusion An MR angiography collateral map was clinically reliable for collateral estimation in patients with acute ischemic stroke. This map provided patient-specific pacing information for ischemic progression. © RSNA, 2020.

Feasibility of test-bolus DCE-MRI using CAIPIRINHA-VIBE for the evaluation of pancreatic malignancies.

OBJECTIVES: To evaluate the feasibility of test-bolus dynamic contrast-enhanced (DCE) MRI with CAIPIRINHA-VIBE for pancreatic malignancies. METHODS: Thirty-two patients underwent DCE-MRI with CAIPIRINHA-VIBE after injection of 2 mL gadolinium. From the resulting time-intensity curve (TIC), we estimated the arterial (AP) and portal venous phase (PVP) scan timing for subsequent multiphasic MRI. DCE-MRI perfusion maps were generated, and perfusion parameters were calculated. The image quality was rated on a 5-point scale (1: poor, 5: excellent). Goodness-of-fit of the TIC was evaluated by Pearson's χ2 test. RESULTS: Test-bolus DCE-MRIs with high temporal (3 s) and spatial resolution (1 × 1 × 4 mm3) were acquired with good-quality perfusion maps of Ktrans and iAUC (mean score 4.313 ± 0.535 and 4.125 ± 0.554, respectively). The mean χ2 values for fitted TICs were 0.115 ± 0.082 for the pancreatic parenchyma and 0.784 ± 0.074 for pancreatic malignancies, indicating an acceptable goodness-of-fit. Test-bolus DCE-MRI was highly accurate in estimating the proper timing of AP (90.6 %) and PVP (100 %) of subsequent multiphasic MRI. Between pancreatic adenocarcinomas and neuroendocrine tumours, there were significant differences in the Ktrans (0.073 ± 0.058 vs. 0.308 ± 0.062, respectively; p = 0.007) and iAUC (1.501 ± 0.828 vs. 3.378 ± 0.378, respectively; p = 0.045). CONCLUSIONS: Test-bolus DCE-MRI using CAIPIRINHA-VIBE is feasible for incorporating perfusion analysis of pancreatic tumours into routine multiphasic MRI. KEY POINTS: • Test-bolus DCE-MRI using CAIPIRINHA-VIBE is feasible for perfusion analysis of pancreatic tumours. • CAIPIRINHA-VIBE enables DCE-MRI with high temporal and spatial resolution. • Test-bolus DCE-MRI is highly accurate in estimating the proper timing of multiphasic MRI.

Intravoxel incoherent motion diffusion-weighted MR imaging of the liver: effect of triggering methods on regional variability and measurement repeatability of quantitative parameters.

PURPOSE: To compare the influence of triggering methods for diffusion-weighted imaging (DWI) on apparent diffusion coefficient (ADC) and intravoxel incoherent motion (IVIM) parameters in the liver, as well as regional variability and measurement repeatability. MATERIALS AND METHODS: In this institutional review board-approved prospective study, 12 healthy volunteers (six women, six men; mean age, 30 years) underwent 1.5-T DWI of the liver by using nine b values twice with free breathing (FB) without triggering (mean acquisition time ± standard deviation, 3.7 minutes ± 0), respiratory triggering (RT) (mean acquisition time, 6.8 minutes ± 1.4), and echocardiography triggering (ET) (mean acquisition time, 8.3 minutes ± 2.0) after providing written informed consent. ADC and IVIM parameters, including pure diffusion coefficient (D), perfusion fraction (f), and perfusion-related diffusion coefficient (D*), were measured by using 15 regions of interest (ROIs). Regional variability of ADC and IVIM parameters and measurement repeatability were evaluated by using the coefficient of variation (CV) across ROIs and within-subject CV, respectively. RESULTS: ET DWI (range of CV across ROIs, 6.69%-20.0%) resulted in significantly decreased regional variability of ADC, D, and f, compared with FB DWI (13.86%-35.8%) and RT DWI (15.15%-35.91%, P ≤. 049). ET DWI showed better repeatability of ADC measurement (within-subject CV range, 3.17%-4.12% for ET DWI; 4.15%-4.74% for FB DWI; and 2.33%-6.96% for RT DWI), D (4.05%-5.34% for ET DWI, 4.11%-12.51% for FB DWI, and 3.19%-16.17% for RT DWI), and f (7.6%-9.86% for ET DWI, 13.83%-16.81% for FB DWI, and 10.05%-12.10% for RT DWI), compared with FB DWI and RT DWI, with significant differences in within-subject CV for D in the left hepatic lobe compared with RT DWI (P = .023) and for f compared with FB DWI (P ≤ .032). For all three imaging techniques, D* showed the worst repeatability (within-subject CV, 57.05%-156.61%) among ADC and IVIM parameters. CONCLUSION: ET DWI is more effective for decreasing regional variability of ADC and IVIM parameters than FB DWI or RT DWI; it may improve measurement repeatability by reducing cardiac motion-induced measurement error.

Intravoxel incoherent motion MRI for liver fibrosis assessment: a pilot study.

BACKGROUND: There has been a growing need for an imaging method for the accurate diagnosis and staging of liver fibrosis as a non-invasive alternative to liver biopsy. PURPOSE: To evaluate the feasibility of intra-voxel incoherent motion (IVIM) imaging for classifying the severity of liver fibrosis. MATERIAL AND METHODS: Fifty-seven patients who underwent navigator-triggered, diffusion-weighted imaging (DWI) of the liver on a 1.5-T system using nine b-values and had a reliable reference standard for the diagnosis of liver fibrosis (histopathologic findings [n = 27] or clinical findings for normal [n = 18] or cirrhotic liver [n = 12]), were included in our study. Liver apparent diffusion coefficient (ADC), pure diffusion (Dslow), perfusion fraction (f), and perfusion-related diffusion (Dfast), and the product f · Dfast were compared with the liver fibrosis stages (F). The accuracies of these parameters in diagnosing severe liver fibrosis (F ≥3) were evaluated using the receiver-operating characteristic (ROC) curve analysis. RESULTS: The liver fibrosis stages had the strongest negative correlation with f · Dfast (ρ = -0.52). All of the parameters, except for Dslow, were significantly lower in patients with F ≥3 than in those with F ≤2 (P ≤ 0.001). The area under the ROC curve for diagnosing severe fibrosis was the largest for f · Dfast (0.844) with an overall accuracy of 79.0% (45/57) at the optimal cutoff value and followed by f (0.834), Dfast (0.773), ADC (0.762), and Dslow (0.656). CONCLUSION: IVIM imaging is a promising method for classifying the severity of liver fibrosis, with the product f · Dfast being the most accurate parameter.

Parallel imaging improves the image quality and duct visibility of breathhold two-dimensional thick-slab MR cholangiopancreatography.

PURPOSE: To evaluate the effect of parallel imaging (PI) with different acceleration factors on the image quality and duct visibility of breathhold two-dimensional (2D) thick-slab single-shot turbo spin-echo (SSTSE) MR cholangiopancreatography (MRCP) images. MATERIALS AND METHODS: Breathhold 2D thick-slab SSTSE MRCP was performed three times, i.e., without PI, with PI factor 2, and with PI factor 3, at 1.5 Tesla (T) for each of 85 patients. Two, independent readers evaluated the image quality and the visibility of five duct segments and ranked their preference of the three MRCP sequences. The data were analyzed using the repeated-measures analysis of variance test, the Friedman test, and the linear-by-linear chi-square test. RESULTS: MRCP sequences with PI factor 2 or 3 generated better image quality (P < 0.001) and an improved duct visibility for all duct segments (P ≤ 0.01), while no significant difference was noted between the MRCP sequences with PI factor 2 and PI factor 3 (P > 0.05). Among the three sequences, both readers most often preferred the MRCP with PI factor 3, followed by the MRCP with PI factor 2 (P < 0.001). CONCLUSION: The application of PI improves the image quality and duct visibility in breathhold 2D thick-slab SSTSE MRCP.

Using intravoxel incoherent motion MR imaging to evaluate cortical defects in the first episode of upper urinary tract infections: preliminary results.

PURPOSE: To compare intravoxel incoherent motion diffusion weight imaging IVIM-DWI MRI with DMSA for the evaluation of cortical defect in pediatric upper urinary tract infection (UTI) patients. MATERIALS AND METHODS: Forty-three kidneys of 22 pediatric patients with the first episode of febrile upper UTI were evaluated. DWI using IVIM model was performed with eight b factors. The presence of cortical defect was evaluated on apparent diffusion coefficient (ADC) map. DMSA was used as the standard of reference. ADC, true diffusion coefficient (D), pseudo-diffusion coefficient (D*), and perfusion fraction (F) in both defect and nondefect area were calculated and compared. RESULTS: Cortical defects were detected in 14 kidneys by IVIM-DWI. The sensitivity, specificity, positive predictive value, and negative predictive value of IVIM-DWI MRI for the detection of defects was 93.3%, 100%, 100%, and 96.5%, respectively. Mean values of ADC, D, D*, and F were 1.12 ± 0.15, 1.05 ± 0.10, 33 ± 17 (× 10(-3) mm(2) /s), and 0.14 ± 0.09 in the defect foci. In normal foci, ADC, D, D*, and F were 1.37 ± 0.09, 1.31 ± 0.10, 43 ± 19 (× 10(-3) mm(2) /s), and 0.12 ± 0.04, respectively. ADC and D were significantly lower in defect group than nondefect group (P < 0.01). CONCLUSION: IVIM-DWI can allow both direct visualization and quantitative measurement of cortical defects.

Associations of Longitudinal Multiparametric MRI Findings and Clinical Outcomes in Intra-Articular Injections for Knee Osteoarthritis.

BACKGROUND: Osteoarthritis (OA) is a complex disease marked by the degradation of articular cartilage. OBJECTIVE: This study aimed to explore the relationship between cartilage volume/thickness and clinical outcomes in knee OA patients treated with intra-articular injections over one year. METHODS: Twenty-four patients with mild-to-moderate OA were retrospectively analyzed using knee MRI. OA features were assessed semiquantitatively with the Whole-Organ Magnetic Resonance Imaging Score (WORMS), while cartilage thickness and volume in the medial femoral condyle (MFC) and medial tibial plateau (MTP) were measured. T1ρ and T2 values for MFC cartilage were also recorded. Clinical outcomes were evaluated using the Korean Western Ontario and McMaster Universities (K-WOMAC) and Knee Injury Osteoarthritis Outcomes (KOOS) scores. Spearman's rank test assessed the associations between imaging changes and clinical outcomes. RESULTS: The baseline MTP and MFC cartilage thickness and MTP cartilage volume showed significant correlations with clinical outcomes. Additionally, less progressive cartilage loss in the medial femorotibial joint (MFTJ) and overall joint was linked to a better clinical response over 12 months. CONCLUSIONS: In conclusion, thicker baseline MFTJ cartilage and minimal cartilage loss were associated with favorable clinical outcomes in knee OA patients receiving intra-articular injections.

Functional Magnetic Resonance Imaging and Diffusion Tensor Imaging for Language Mapping in Brain Tumor Surgery: Validation With Direct Cortical Stimulation and Cortico-Cortical Evoked Potential.

OBJECTIVE: Functional magnetic resonance imaging (fMRI) and diffusion tensor imaging-derived tractography (DTI-t) contribute to the localization of language areas, but their accuracy remains controversial. This study aimed to investigate the diagnostic performance of preoperative fMRI and DTI-t obtained with a simultaneous multi-slice technique using intraoperative direct cortical stimulation (DCS) or corticocortical evoked potential (CCEP) as reference standards. MATERIALS AND METHODS: This prospective study included 26 patients (23-74 years; male:female, 13:13) with tumors in the vicinity of Broca's area who underwent preoperative fMRI and DTI-t. A site-by-site comparison between preoperative (fMRI and DTI-t) and intraoperative language mapping (DCS or CCEP) was performed for 226 cortical sites to calculate the sensitivity and specificity of fMRI and DTI-t for mapping Broca's areas. For sites with positive signals on fMRI or DTI-t, the true-positive rate (TPR) was calculated based on the concordance and discordance between fMRI and DTI-t. RESULTS: Among 226 cortical sites, DCS was performed in 100 sites and CCEP was performed in 166 sites. The specificities of fMRI and DTI-t ranged from 72.4% (63/87) to 96.8% (122/126), respectively. The sensitivities of fMRI (except for verb generation) and DTI-t were 69.2% (9/13) to 92.3% (12/13) with DCS as the reference standard, and 40.0% (16/40) or lower with CCEP as the reference standard. For sites with preoperative fMRI or DTI-t positivity (n = 82), the TPR was high when fMRI and DTI-t were concordant (81.2% and 100% using DCS and CCEP, respectively, as the reference standards) and low when fMRI and DTI-t were discordant (≤ 24.2%). CONCLUSION: fMRI and DTI-t are sensitive and specific for mapping Broca's area compared with DCS and specific but insensitive compared with CCEP. A site with a positive signal on both fMRI and DTI-t represents a high probability of being an essential language area.

Quantitative evaluation of liver cirrhosis using T1 relaxation time with 3 tesla MRI before and after oxygen inhalation.

PURPOSE: To quantify liver T1 relaxation times before and after oxygen inhalation in patients with and without liver cirrhosis using a 3 Tesla (T) MRI. MATERIALS AND METHODS: Institutional Review Board approval and written informed consent were obtained. Ninety-two noncirrhotic patients and 87 patients with hepatitis B viral liver cirrhosis (72 Child-Pugh class A and 15 Child-Pugh class B or C) underwent MRI with a 3.0T system before and after the supply of 100% oxygen at a rate of 15 L/min by means of a nonrebreather ventilation mask for 3 min. T1 maps were acquired using three-dimensional spoiled gradient echo sequences with two different flip angles (2° and 14°) and a fixed TR/TE (2.54 ms/0.95 ms). Liver T1 values were obtained using a T1 processing tool (MapIT software). The mean baseline T1 values of three groups (control, Child-Pugh class A, and Child-Pugh class B/C) were compared using an analysis of variance test. Liver T1 value before and after oxygenation was compared using a paired t-test for each group. RESULTS: The baseline liver T1 value was significantly higher in the control group (941 ± 136 ms) than in Child-Pugh A (858 ± 143 ms) and Child-Pugh B/C (783 ± 164 ms) group (P < 0.001 and P < 0.0001). The reduction in the liver T1 value after oxygen inhalation was significant in the control group (P = 0.012) but not significant in Child-Pugh class A (P = 0.079) and Child-Pugh class B/C (P = 0.752). CONCLUSION: The baseline liver T1 relaxation time was significantly different between the patients with and without liver cirrhosis. The shortening effect of oxygen on the liver T1 value was significant in the control group but not in the cirrhotic patients.

Automated hippocampal subfield segmentation in amnestic mild cognitive impairments.

Although a few automated hippocampal subfield segmentation methods have been developed, the effects of amnestic mild cognitive impairment (aMCI) on the hippocampal subfield volumes on magnetic resonance imaging (MRI) are not clear. The aim of this study was to investigate the hippocampal subfield volume changes and their relationships with various neuropsychological tests in aMCI using an automated hippocampal subfield segmentation technique. Forty-five subjects with aMCI and 49 group-matched healthy control subjects underwent 3-tesla MRI scanning, and hippocampal subfield volumes were measured and compared. Additionally, we explored the correlation pattern between hippocampal subfield volumes and the Korean version of the Consortium to Establish a Registry for Alzheimer's Disease (CERAD-K) neuropsychological test scores in aMCI subjects. Subjects with aMCI exhibited significant hippocampal volume reductions in the presubiculum, subiculum and cornu ammonis 2-3 areas compared with healthy subjects. In addition, we also found significant positive correlations between presubiculum and subicular area volumes and the CERAD-K verbal and visuospatial delayed recall scores in aMCI. This study was the first to explore the relationships between hippocampal subfield volumes and various types of cognitive performances in aMCI. These structural changes might be at the core of the underlying neurobiological mechanisms of hippocampal dysfunction in aMCI.

The Association between the Magnetic Resonance Imaging Findings of Adhesive Capsulitis and Shoulder Muscle Fat Quantification Using a Multi-Echo Dixon Method.

Objective: To investigate the association between the magnetic resonance imaging (MRI) findings of adhesive capsulitis and shoulder muscle fat percentages using a multi-echo Dixon method. Materials and Methods: Twenty-four patients with clinical diagnoses of adhesive capsulitis and either intact rotator cuffs or Ellman grade 1 partial tears as indicated by MRI scans were included. Two radiologists independently evaluated MRI scans of adhesive capsulitis as follows: presence or absence of axillary recess capsular and extracapsular hyperintensities; thickness of the coracohumeral ligament; thickness of abnormal rotator interval soft tissue; and thickness of glenoidal/humeral axillary recess capsules. Fat quantifications of the supraspinatus, infraspinatus, teres minor, subscapularis, teres major and posterior deltoid muscles were performed using multi-echo Dixon imaging at three locations. Inter-rater agreement was assessed. Differences in fat percentages were assessed and correlations between fat percentages and quantitative measurements were evaluated. Results: The fat percentage of the supraspinatus was significantly higher in patients with extracapsular hyperintensity (present, 3.00 ± 1.74%; absent, 1.81 ± 0.80%; p = 0.022). There were positive correlations between the fat percentage of the teres minor and the thicknesses of the abnormal rotator interval soft tissue (r = 0.494, p = 0.014) and the glenoidal axillary recess capsule (r = 0.475, p = 0.019). After controlling for the effects of age, sex and clinical stage, the relationship between the teres minor fat percentage and the thickness of the abnormal rotator interval soft tissue was statistically significant (r = 0.384, p = 0.048). Inter-rater agreement was almost perfect for fat quantification (intraclass correlation coefficients [ICC] > 0.9) and qualitative analyses (k = 0.824), but were variable for quantitative measurements (ICC, 0.170-0.606). Conclusion: Several MRI findings of adhesive capsulitis were significantly related to higher fat percentages of shoulder muscles.

The Effects of Breathing Motion on DCE-MRI Images: Phantom Studies Simulating Respiratory Motion to Compare CAIPIRINHA-VIBE, Radial-VIBE, and Conventional VIBE.

OBJECTIVE: To compare the breathing effects on dynamic contrast-enhanced (DCE)-MRI between controlled aliasing in parallel imaging results in higher acceleration (CAIPIRINHA)-volumetric interpolated breath-hold examination (VIBE), radial VIBE with k-space-weighted image contrast view-sharing (radial-VIBE), and conventional VIBE (c-VIBE) sequences using a dedicated phantom experiment. MATERIALS AND METHODS: We developed a moving platform to simulate breathing motion. We conducted dynamic scanning on a 3T machine (MAGNETOM Skyra, Siemens Healthcare) using CAIPIRINHA-VIBE, radial-VIBE, and c-VIBE for six minutes per sequence. We acquired MRI images of the phantom in both static and moving modes, and we also obtained motion-corrected images for the motion mode. We compared the signal stability and signal-to-noise ratio (SNR) of each sequence according to motion state and used the coefficients of variation (CoV) to determine the degree of signal stability. RESULTS: With motion, CAIPIRINHA-VIBE showed the best image quality, and the motion correction aligned the images very well. The CoV (%) of CAIPIRINHA-VIBE in the moving mode (18.65) decreased significantly after the motion correction (2.56) (p < 0.001). In contrast, c-VIBE showed severe breathing motion artifacts that did not improve after motion correction. For radial-VIBE, the position of the phantom in the images did not change during motion, but streak artifacts significantly degraded image quality, also after motion correction. In addition, SNR increased in both CAIPIRINHA-VIBE (from 3.37 to 9.41, p < 0.001) and radial-VIBE (from 4.3 to 4.96, p < 0.001) after motion correction. CONCLUSION: CAIPIRINHA-VIBE performed best for free-breathing DCE-MRI after motion correction, with excellent image quality.

Comparison of T1rho and T2 Mapping of Knee Articular Cartilage in an Asymptomatic Population.

OBJECTIVE: To analyze subregional differences in T1rho (T1ρ) and T2 values and their correlation in asymptomatic knee cartilage, and to evaluate angular dependence with magic angles. MATERIALS AND METHODS: Six asymptomatic volunteers underwent knee MRI with T1ρ and T2 mapping. T1ρ and T2 values were measured by two radiologists independently, at nine subregions in the medial femoral condyle (MFC) cartilage, at angles of ± 0°, 15°, 35°, 55°, 75° respective to a vertical line (B0) bisecting the width of the distal femur, and at two locations in the patella. Subregional values of T1ρ and T2 were analyzed and significant differences in three divided portions of the MFC (anterior, central, and posterior) were statistically evaluated. Correlation between T1ρ and T2 and angular dependence with magic angles were also assessed for statistical significance. RESULTS: T1ρ values were lowest at +15° and highest at -55°. T2 values were lowest at +75° and highest at +35°. Both T1ρ and T2 were higher in superior patella than inferior patella. T1ρ showed significant differences in the three divided portions of the MFC, while T2 showed significant differences only between central and posterior portions. There was a weak correlation between T1ρ and T2 (r = 0.217, p = 0.127). T1ρ showed more angular dependence than T2. CONCLUSION: T1ρ and T2 showed different subregional values and angular dependence in asymptomatic knee cartilage with a weak correlation. Awareness of these differences will aid in assessment of cartilage in a specific subregion of the knee.

Comparison of CAIPIRINHA-VIBE, Radial-VIBE, and conventional VIBE sequences for dynamic contrast-enhanced (DCE) MRI: A validation study using a DCE-MRI phantom.

OBJECTIVE: To validate radial acquisition of volumetric interpolated breath hold examination (Radial-VIBE) and the controlled aliasing in parallel imaging results in higher acceleration (CAIPIRINHA-VIBE) sequences for dynamic contrast-enhanced MRI (DCE-MRI) by comparing them to conventional VIBE sequence using a phantom. METHODS: On a DCE-MRI phantom containing various concentrations of NiCl2 solutions, six minutes of dynamic series and T1 mapping with variable flip angle methods were acquired using conventional VIBE, Radial-VIBE, and CAIPIRINHA-VIBE sequences on 3.0-T scanners. Signal stability and signal linearity were tested for dynamic series and the precision of R1 values were tested for T1 mapping series. The scans were repeatedly performed at two weeks and three months to test repeatability/reproducibility, assessed by within-subject coefficient of variation (WSCV). RESULTS: Signal stability over six minutes was excellent in all three sequences. Regarding the signal linearity, CAIPIRINHA-VIBE demonstrated the highest linear correlation (r=0.963), followed by conventional VIBE (r=0.959) and Radial-VIBE (r=0.953). Regarding the R1 precision, CAIPIRINHA-VIBE (r=0.985) was the most accurate, followed by conventional VIBE (r=0.861) and Radial-VIBE (r=0.442). CAIPIRINHA-VIBE showed excellent repeatability/reproducibility (WSCV, 1.79-6.71%) compared with Radial-VIBE (WSCV, 2.04-67.2%) and conventional VIBE (WSCV, 3.4-31.9%). CONCLUSION: In terms of signal stability, signal linearity, R1 precision, and repeatability/reproducibility, CAIPIRINHA-VIBE demonstrated outstanding performance for DCE-MRI compared with Radial-VIBE and conventional VIBE.

Hepatic Arterial Phase in Gadoxetic Acid-Enhanced Liver Magnetic Resonance Imaging: Analysis of Respiratory Patterns and Their Effect on Image Quality.

OBJECTIVE: The aims of this study were to objectively evaluate patient respiration and breathing change after contrast injection and to assess its potential impact on image quality for the hepatic arterial phase in gadoxetic acid-enhanced magnetic resonance imaging. MATERIALS AND METHODS: This retrospective study was approved by the institutional review board, and the requirement for informed consent was waived. One hundred fifty-four patients underwent gadoxetic acid-enhanced liver magnetic resonance imaging with a 13-second breath-hold hepatic arterial phase. During the acquisition of precontrast and hepatic arterial phases, the respiratory motion signal was acquired and graded on a 4-point scale based on the SD of the respiratory waveform, with the highest grade indicating the worst breath-hold. Breath-holding grades 3 and 4 for the hepatic arterial phases were considered as breath-holding difficulty during the hepatic arterial phase. Gadoxetic acid-related dyspnea was defined as when the SD value of respiratory waveform during the hepatic arterial phase was 200 greater than that of the precontrast image. Then, the precontrast and hepatic arterial phase images were evaluated with respect to overall image quality and motion artifact using a 5-point scale, with the highest score indicating the worst image quality. In the hepatic arterial phase, the correlation between breath-holding degree and image quality parameters was evaluated using Pearson correlation. The differences in mean image quality scores between patients with and without gadoxetic acid-related dyspnea were evaluated using Student t test. RESULTS: Based on the analysis of the respiratory waveforms, the incidence of breath-holding difficulty during the hepatic arterial phase was 23.4% (33/154), and the incidence of gadoxetic acid-related dyspnea was 6.5% (10/154). By image analysis, the incidence of a degraded hepatic arterial phase (overall image quality score ≥4) was 5.2% (8/154). During the hepatic arterial phase, the breath-holding degree correlated with overall image quality and motion artifacts (r = 0.564 and 0.578, respectively). Patients with gadoxetic acid-related dyspnea showed significantly worse image qualities of the hepatic arterial phase than patients without gadoxetic acid-related dyspnea (all, P < 0.001), although image qualities for the precontrast image were not statistically significant between the 2 groups (all, P > 0.05). CONCLUSIONS: The objective analysis of respiratory patterns during a breath-hold is feasible and useful for evaluating gadoxetic acid-related dyspnea and its effect on image quality analysis.

Accuracy of Diffusion Tensor Imaging for Diagnosing Cervical Spondylotic Myelopathy in Patients Showing Spinal Cord Compression.

OBJECTIVE: To assess the performance of diffusion tensor imaging (DTI) for the diagnosis of cervical spondylotic myelopathy (CSM) in patients with deformed spinal cord but otherwise unremarkable conventional magnetic resonance imaging (MRI) findings. MATERIALS AND METHODS: A total of 33 patients who underwent MRI of the cervical spine including DTI using two-dimensional single-shot interleaved multi-section inner volume diffusion-weighted echo-planar imaging and whose spinal cords were deformed but showed no signal changes on conventional MRI were the subjects of this study. Mean diffusivity (MD), longitudinal diffusivity (LD), radial diffusivity (RD), and fractional anisotropy (FA) were measured at the most stenotic level. The calculated performance of MD, FA, MD∩FA (considered positive when both the MD and FA results were positive), LD∩FA (considered positive when both the LD and FA results were positive), and RD∩FA (considered positive when both the RD and FA results were positive) in diagnosing CSM were compared with each other based on the estimated cut-off values of MD, LD, RD, and FA from receiver operating characteristic curve analysis with the clinical diagnosis of CSM from medical records as the reference standard. RESULTS: The MD, LD, and RD cut-off values were 1.079 × 10(-3), 1.719 × 10(-3), and 0.749 × 10(-3) mm(2)/sec, respectively, and that of FA was 0.475. Sensitivity, specificity, positive predictive value and negative predictive value were: 100 (4/4), 44.8 (13/29), 20 (4/20), and 100 (13/13) for MD; 100 (4/4), 27.6 (8/29), 16 (4/25), and 100 (8/8) for FA; 100 (4/4), 58.6 (17/29), 25 (4/16), and 100 (17/17) for MD∩FA; 100 (4/4), 68.9 (20/29), 30.8 (4/13), and 100 (20/20) for LD∩FA; and 75 (3/4), 68.9 (20/29), 25 (3/12), and 95.2 (20/21) for RD∩FA in percentage value. Diagnostic performance comparisons revealed significant differences only in specificity between FA and MD∩FA (p = 0.003), FA and LD∩FA (p < 0.001), FA and RD∩FA (p < 0.001), MD and LD∩FA (p = 0.024) and MD and RD∩FA (p = 0.024). CONCLUSION: Fractional anisotropy combined with MD, RD, or LD is expected to be more useful than FA and MD for diagnosing CSM in patients who show deformed spinal cords without signal changes on MRI.

Usefulness of controlled aliasing in parallel imaging results in higher acceleration in gadoxetic acid-enhanced liver magnetic resonance imaging to clarify the hepatic arterial phase.

PURPOSE: We aimed to determine whether the controlled aliasing in parallel imaging results in higher acceleration (CAIPIRINHA) technique could improve the image quality of the hepatic arterial phase of gadoxetic acid-enhanced liver magnetic resonance (MR) imaging. MATERIALS AND METHODS: A total of 320 patients underwent gadoxetic acid-enhanced liver MR imaging: a conventional protocol (a fixed scan delay and 2-mL/s injection) using a standard 3-T MR system (Trio-Tim; Siemens, commercialized since 2005) (group A), an optimized protocol (bolus tracking and 1-mL/s injection) using a standard 3-T MR (group B), an optimized protocol using a new 3-T MR (Skyra; Siemens, commercialized since 2012) (group C), and an optimized protocol with CAIPIRINHA using a new 3-T MR (group D). The image quality of the hepatic arterial phase was graded using a 4-point rating scale from 1 (no artifacts) to 4 points (non-diagnostic images with severe artifacts). The differences in image quality scores among the 4 groups were evaluated. In addition, the detection rates of hypervascular hepatocellular carcinomas among the 4 groups were evaluated. RESULTS: Scores of 4 points were observed in groups A (n = 7), B (n = 5), and C (n = 3) but not in group D. The median image quality score was 2 in groups A and B and 1 in groups C and D. From group A to group D, the median image quality score decreased significantly (P = 0.0001). The median image quality score was significantly lower in group D than in groups A and B (P = 0.0001 and 0.001, respectively), whereas there was no significant difference observed between groups C and D (P = 0.656). The detection rates of hypervascular hepatocellular carcinomas on the hepatic arterial phase were not significantly different among the groups (all P > 0.03), except between groups A and D (P = 0.007). CONCLUSIONS: The CAIPIRINHA technique improved the image quality of hepatic arterial phase imaging with gadoxetic acid, reducing the number of non-diagnostic arterial phase studies.

Using intravoxel incoherent motion (IVIM) MR imaging to predict lipiodol uptake in patients with hepatocellular carcinoma following transcatheter arterial chemoembolization: a preliminary result.

PURPOSE: To assess the usefulness of intravoxel incoherent motion diffusion weighted imaging (IVIM-DWI) for predicting lipiodol uptake in patients with hepatocellular carcinoma (HCC) after transcatheter arterial chemoembolization (TACE). MATERIALS AND METHODS: The institutional review board approved this study. 44 HCC patients underwent IVIM-DWI and Gd-EOB-DTPA-enhanced MRI prior to TACE. Using post-TACE CT as a reference standard, each HCC was classified into either lipiodol good uptake (LGU) or poor uptake (LPU) group. Apparent diffusion coefficient (ADC), true diffusion coefficient (D), perfusion coefficient (D*), and perfusion fraction (f) in HCC were calculated. Arterial enhancement ratio (AER) and IVIM parameters were compared between those two groups using the Mann-Whitney U test. RESULTS: Of the 51 HCCs, 37 (72.5%) were LGU group and 14 (27.5%) were LPU group. AER of HCC was significantly higher in LGU than LPU (0.99±0.54 and 0.67±0.45; P=.034). ADC, D, and f values were not significantly different (P=.073, .059, and .196, respectively) between these two groups. D* was significantly elevated in LGU than LPU (48.10±15.33 and 26.75±9.55; P=.001). CONCLUSION: Both AER derived from contrast enhanced MRI and D* values derived from IVIM-DWI for HCC were significantly higher in LGU than in LPU. These parameters would be helpful for predicting the lipiodol uptake.

Severe edema of the eyes and lips as rare side effects of eye ointment for protection of eyes under general anesthesia -A case report-.

Patients undergoing non-ocular surgery under general anesthesia may suffer from ocular complications because of the loss of protective reflexes. Simple taping of the eyelids closed, the instillation of ointments into the conjunctival sac, and the use of protective goggles have been recommended for eye protection. We observed a case of a 6-year-old child undergoing tonsillectomy and adenoidectomy who experienced severe edema after application of an ointment (Terramycin ophthalmic ointment) to the orbits and upper lip. After several days of steroid and antihistamine administration, the edema of the orbits and lip returned to normal. Therefore, we suggest that unexpected edema in the orbits and lip following surgery can be due to hypersensitivity to the ointment.