Dixon Fat Research Articles

3D Dixon water-fat LGE imaging with image navigator and compressed sensing in cardiac MRI

ObjectivesTo evaluate an image-navigated isotropic high-resolution 3D late gadolinium enhancement (LGE) prototype sequence with compressed sensing and Dixon water-fat separation in a clinical routine setting.Material and methodsForty consecutive patients scheduled for cardiac MRI were enrolled prospectively and examined with 1.5 T MRI. Overall subjective image quality, LGE pattern and extent, diagnostic confidence for detection of LGE, and scan time were evaluated and compared to standard 2D LGE imaging. Robustness of Dixon fat suppression was evaluated for 3D Dixon LGE imaging. For statistical analysis, the non-parametric Wilcoxon rank sum test was performed.ResultsLGE was rated as ischemic in 9 patients and non-ischemic in 11 patients while it was absent in 20 patients. Image quality and diagnostic confidence were comparable between both techniques (p = 0.67 and p = 0.66, respectively). LGE extent with respect to segmental or transmural myocardial enhancement was identical between 2D and 3D (water-only and in-phase). LGE size was comparable (3D 8.4 ± 7.2 g, 2D 8.7 ± 7.3 g, p = 0.19). Good or excellent fat suppression was achieved in 93% of the 3D LGE datasets. In 6 patients with pericarditis, the 3D sequence with Dixon fat suppression allowed for a better detection of pericardial LGE. Scan duration was significantly longer for 3D imaging (2D median 9:32 min vs. 3D median 10:46 min, p = 0.001).ConclusionThe 3D LGE sequence provides comparable LGE detection compared to 2D imaging and seems to be superior in evaluating the extent of pericardial involvement in patients suspected with pericarditis due to the robust Dixon fat suppression.Key Points• Three-dimensional LGE imaging provides high-resolution detection of myocardial scarring.• Robust Dixon water-fat separation aids in the assessment of pericardial disease.• The 2D image navigator technique enables 100% respiratory scan efficacy and permits predictable scan times.

Non-invasive assessment of peripheral skeletal muscle weakness in idiopathic pulmonary fibrosis: a pilot study with multiparametric MRI of the rectus femoris muscle

BackgroundTo investigate differences in magnetic resonance imaging (MRI) features of rectus femoris muscle between idiopathic pulmonary fibrosis (IPF) patients and healthy volunteers.MethodsThirteen IPF patients with GAP Index stage II disease were subjected to pulmonary function tests, 6-minute walk test (6MWT), quadriceps femoris muscle strength measurement and MRI of the thigh at rest. At MRI, muscle cross-sectional areas, T2 and T2* relaxometry, and 3-point Dixon fat fraction were measured. The results were compared to those of eight healthy sedentary volunteers.ResultsIPF patients had significantly lower %predicted FVC, FEV1 and DLCO (p<0.001 for the three variables) and walked significantly less in the 6MWT (p=0.008). Mean quadriceps femoris muscle strength also was significantly lower in IPF patients (p=0.041). Rectus femoris muscle T2* measurements were significantly shorter in IPF patients (p=0.027). No significant intergroup difference was found regarding average muscle cross-sectional areas (p=0.790 for quadriceps and p=0.816 for rectus femoris) or rectus femoris fat fraction (p=0.901). Rectus femoris T2 values showed a non-significant trend to be shorter in IPF patients (p=0.055).ConclusionsOur preliminary findings suggest that, besides disuse atrophy, other factors such as hypoxia (but not inflammation) may play a role in the peripheral skeletal muscle dysfunction observed in IPF patients. This might impact the rehabilitation strategies for IPF patients and warrants further investigation.

Feasibility and Robustness of 3T Magnetic Resonance Angiography Using Modified Dixon Fat Suppression in Patients With Known or Suspected Peripheral Artery Disease.

Objective: Contrast-enhanced magnetic resonance angiography (CE-MRA) is a well-established non-invasive imaging technique for the assessment of peripheral artery disease (PAD). A subtractionless method using modified Dixon (mDixon) fat suppression showed superior image quality at 1.5T over the common subtraction method, using a three-positions stepping table approach with a single dose of contrast agent. The aim of this study was to investigate the feasibility of subtractionless first-pass peripheral MRA at 3T in patients with known or suspected PAD and to compare the performance in terms of vessel-to-background contrast (VBC), signal-to-noise ratio (SNR), and subjective image quality to conventional subtraction MRA.Methods: Ten patients [mean age 69 years ± 12 standard deviation (SD)] with known or suspected PAD were examined on a clinical 3T scanner (Ingenia, Philips Healthcare, Best, Netherlands) at three table positions using subtractionless and subtraction first-pass peripheral MRA. Two readers rated image quality on a four- point scale. Interobserver agreement was expressed in quadratic weighted κ values. VBC was assessed with a semi-automated process and SNR was compared in a healthy volunteer.Results: Subjective image quality was significantly better with the subtractionless method overall (mean image quality for mDixon imaging: 2.88 ± 0.32 SD vs. for subtraction imaging: 2.57 ± 0.48 SD; P < 0.001) and per table position (abdominal position: 2.88 ± 0.32 vs. 2.57 ± 0.48 SD; P < 0.001); upper leg position: (2.97 ± 0.15 SD vs. 2.68 ± 0.37 SD; P < 0.001; lower leg position: 2.60 ± 0.50 SD vs. 2.13 ± 0.60 SD; P < 0.001). Vessel-to-background contrast increased by 22% with the subtractionless method overall (mean VBC for mDixon imaging: 23.16 ± 8.4 SD vs. for subtraction imaging: 19.00 ± 8.1 SD; factor 1.22, P < 0.001). SNR was 82% higher with the subtractionless method (overall SNR gain 1.82; P < 0.001).Conclusion: This study demonstrated the feasibility and robustness of subtractionless first-pass peripheral MRA at 3T in patients with known or suspected PAD using a three- positions stepping table approach with a single dose of contrast agent. It showed increased image quality compared to the conventional subtraction method and superior performance in terms of SNR and vessel-to-background contrast.

Feasibility of free-breathing quantitative myocardial perfusion using multi-echo Dixon magnetic resonance imaging

Dynamic contrast-enhanced quantitative first-pass perfusion using magnetic resonance imaging enables non-invasive objective assessment of myocardial ischemia without ionizing radiation. However, quantification of perfusion is challenging due to the non-linearity between the magnetic resonance signal intensity and contrast agent concentration. Furthermore, respiratory motion during data acquisition precludes quantification of perfusion. While motion correction techniques have been proposed, they have been hampered by the challenge of accounting for dramatic contrast changes during the bolus and long execution times. In this work we investigate the use of a novel free-breathing multi-echo Dixon technique for quantitative myocardial perfusion. The Dixon fat images, unaffected by the dynamic contrast-enhancement, are used to efficiently estimate rigid-body respiratory motion and the computed transformations are applied to the corresponding diagnostic water images. This is followed by a second non-linear correction step using the Dixon water images to remove residual motion. The proposed Dixon motion correction technique was compared to the state-of-the-art technique (spatiotemporal based registration). We demonstrate that the proposed method performs comparably to the state-of-the-art but is significantly faster to execute. Furthermore, the proposed technique can be used to correct for the decay of signal due to T2* effects to improve quantification and additionally, yields fat-free diagnostic images.

MRI Assessment of Chylous and Nonchylous Effusions: Use of Multipoint Dixon Fat Quantification.

Background Diagnosis of chylous effusions normally requires invasive paracentesis. Purpose To assess whether MRI with multipoint Dixon fat quantification allows for noninvasive differentiation of chylous and nonchylous ascites and pleural effusions. Materials and Methods Phantom, ex vivo, and in vivo MRI examinations were performed by using a commercially available multipoint Dixon pulse sequence with a 1.5-T MRI system. Fat fraction values were measured with a region of interest-based approach on reconstructed maps. For phantom evaluation, eight titrated fatty fluid solutions (nonhuman samples) with varying triglyceride content (145-19 000 mg/dL [1.64-214.7 mmol/L]) were examined. For ex vivo evaluation, 15 chylous and five nonchylous study participant fluid samples were examined. In a prospective study performed from June 2016 to February 2018, 29 study participants with known chylous (n = 17) and nonchylous (n = 12) effusions were evaluated with MRI. All clinical samples underwent laboratory testing for triglyceride level, total protein level, white blood cells, and red blood cells. Laboratory values were correlated with fat fraction values; the optimal fat fraction threshold was determined to differentiate chylous and nonchylous fluids. Results Phantom analysis showed that fat fraction values correlated with triglyceride content (r = 0.99, P < .001). In ex vivo studies, multipoint Dixon-derived fat fraction was higher in chylous versus nonchylous fluids (mean, 2.5% ± 1.2 [standard deviation] vs 0.8% ± 0.2; P = .001). Fat fraction was correlated with triglyceride content (r = 0.96, P < .001). For in vivo studies, fat fraction was greater for chylous versus nonchylous fluids (mean, 6.2% ± 4.3 vs 0.6% ± 0.6; P < .001). In vivo fat fraction was correlated with triglyceride content (r = 0.96, P < .001). Use of a fat fraction cutoff value greater than 1.8% yielded a sensitivity of 14 of 17 (82% [95% confidence interval (CI): 57%, 97%]) and a specificity of 12 of 12 (100% [95% CI: 74%, 100%]) for differentiation of chylous and nonchylous effusions. Conclusion MRI can help identify chylous versus nonchylous ascites and pleural effusions through use of multipoint Dixon fat quantification. © RSNA, 2020 Online supplemental material is available for this article.

Correlation of Quantitative Versus Semiquantitative Measures of Supraspinatus Intramuscular Fatty Infiltration to Shoulder Range of Motion and Strength: A Pilot Study

PurposeThe relationship of magnetic resonance imaging (MRI) measures of rotator cuff intramuscular fatty infiltration (FI) to shoulder range of motion (ROM) and strength are not well understood. Our purpose was to determine if supraspinatus quantitative Dixon fat fraction has superior correlation to shoulder ROM and strength as compared to semiquantitative Goutallier grade. MethodsThirty-seven study subjects received shoulder MRI; and measurement of ipsilateral shoulder forward flexion ROM, abduction ROM and abduction strength. Supraspinatus Dixon fat fraction was measured on 6-point Dixon MRI by 2 diagnostic radiology residents. Supraspinatus Goutallier grade was assessed on T1-weighted MRI by 2 musculoskeletal radiologists. Questionnaires recorded demographics. Based on characteristics, study subjects were divided into 3 groups: Group 1, neither shoulder pain nor full-thickness supraspinatus tendon (SST) tear (n = 17; mean age, 63.0 ± 10.1 years); Group 2, positive complaint of shoulder pain but without full-thickness SST tear (n = 7; mean age, 57.4 ± 9.9 years); Group 3, positive complaint of shoulder pain and full-thickness SST tear (n = 13; mean age, 63.6 ± 8.1 years). One-way analysis of variance compared groups. Spearman (rho) rank order correlation was performed to determine correlation of supraspinatus Dixon fat fraction, or Goutallier grade, with measures of ROM and strength for the study population. Reliability analyses were performed for Dixon fat fraction and Goutallier grade. ResultsNo significant differences were present among groups for age. Significant differences existed among groups for forward flexion ROM (P= 0.001), abduction ROM (P < 0.001), Dixon fat fraction (P = 0.004) and Goutallier grade (P = 0.012). Dixon fat fraction showed statistically significant inverse correlations with forward flexion ROM (rho = −0.47; P = 0.005), abduction ROM (rho = −0.35, P = 0.041), and abduction strength (rho = −0.42; P = 0.013). Goutallier grade demonstrated weak inverse correlation that lacked statistical significance (P > 0.05) for the same measures. Dixon fat fraction showed strong interobserver and intraobserver reliability with intraclass correlation coefficients of 0.956 and 0.999, respectively. Goutallier grade showed poor interobserver (kappa, 0.188) and moderate intraobserver (kappa, 0.608) reliability. ConclusionSupraspinatus Dixon fat fraction has superior correlation to shoulder ROM and strength relative to Goutallier grade on MRI.

Magnetic resonance imaging correlates with electrical impedance myography in facioscapulohumeral muscular dystrophy.

Electrical impedance myography (EIM) has been proposed as a noninvasive biomarker of muscle composition in facioscapulohumeral muscular dystrophy (FSHD). Here we determine the associations of EIM variables with muscle structure measured by MRI. We evaluated 20 patients with FSHD at two centers, comparing EIM measurements (resistance, reactance, and phase at 50, 100, and 211 kHZ) recorded from bilateral vastus lateralis, tibialis anterior, and medial gastrocnemius muscles to MRI skin and subcutaneous fat thickness, MRI T1-based muscle severity score (T1 muscle score), and MRI quantitative intramuscular Dixon fat fraction (FF). While reactance and phase both correlated with FF and T1 muscle score, 50 kHz reactance was most sensitive to muscle structure alterations measured by both T1 score (ρ = -0.71, P < .001) and FF (ρ = -0.74, P < .001). This study establishes the correlation of EIM with structural MRI features in FSHD and supports further evaluation of EIM as a potential biomarker in FSHD clinical trials.

Magnetic resonance elastography (MRE) shows significant reduction of thigh muscle stiffness in healthy older adults

Determining the effect of ageing on thigh muscle stiffness using magnetic resonance elastography (MRE) and investigate whether fat fraction and muscle cross-sectional area (CSA) are related to stiffness. Six healthy older adults in their eighth and ninth decade and eight healthy young men were recruited and underwent a 3 T MRI protocol including MRE and Dixon fat fraction imaging. Muscle stiffness, fat fraction and muscle CSA were calculated in ROIs corresponding to the four quadriceps muscles (i.e. vastus lateralis (VL), vastus medialis (VM), vastus intermedius (VI), rectus femoris (RF)), combined quadriceps, combined hamstrings and adductors and whole thigh. Muscle stiffness was significantly reduced (p < 0.05) in the older group in all measured ROIs except the VI (p = 0.573) and RF (p = 0.081). Similarly, mean fat fraction was significantly increased (p < 0.05) in the older group over all ROIs with the exception of the VI (p = 0.059) and VL muscle groups (p = 0.142). Muscle CSA was significantly reduced in older participants in the VM (p = 0.003) and the combined quadriceps (p = 0.001), hamstrings and adductors (p = 0.008) and whole thigh (p = 0.003). Over the whole thigh, stiffness was significantly negatively correlated with fat fraction (r = − 0.560, p = 0.037) and positively correlated with CSA (r = 0.749, p = 0.002). Stepwise regression analysis revealed that age was the most significant predictor of muscle stiffness (p = 0.001). These results suggest that muscle stiffness is significantly decreased in healthy older adults. Muscle fat fraction and muscle CSA are also significantly changed in older adults; however, age is the most significant predictor of muscle stiffness.

Automatic quantification of fat infiltration in paraspinal muscles using T2-weighted images: An OsiriX application

Fat infiltration of paraspinal muscles has been related with low back pain and quantified using T2w MR images and manual segmentation techniques. This methodology is time consuming and has low reproducibility. Moreover, the accuracy of T2w images to quantify fat has not been validated. This paper presents the development and validation of an OsiriX application to semi-automatically segment infiltrated fat on T2w images. This software was also utilized to validate the quantification of muscle fat infiltration with T2w images, considering Dixon fat images assessments as a gold standard.Two databases have been considered: 1)T2w images of 37 patients for comparison between manual and semi-automatic segmentations; 2)T2w and Dixon fat images of 10 healthy volunteers and 10 patients to validate the use of T2w images. The OsiriX application was based on automatic thresholding techniques. The fat infiltration fraction was measured in 4 muscle groups (erector spinae and multifidus) and in 5 cross-sectional areas (from L1-L2 to L5-S1) for both databases. From the 37 patients, we randomly selected 15 patients to assess reproducibility of the measurements.Manual and automatic fat quantifications using T2w images showed a correlation of 0.86, no statistical differences, bias of 0.05 % of the muscle area, and limits of agreement of [-12.52, 12.63]% of muscle area. Fat quantifications using Dixon and T2w images showed correlation of 0.94, no statistical differences, bias of 0.38 % of the muscle area, and limits of agreement of [-8.64, 9.41]% of the muscle area.T2w images segmented with this new OsiriX application are reliable and accurate for quantifying fat infiltration in paraspinal muscles.

UTE-mDixon-based thorax synthetic CT generation.

Accurate photon attenuation assessment from MR data remains an unmet challenge in the thorax due to tissue heterogeneity and the difficulty of MR lung imaging. As thoracic tissues encompass the whole physiologic range of photon absorption, large errors can occur when using, for example, a uniform, water-equivalent or a soft-tissue-only approximation. The purpose of this study was to introduce a method for voxel-wise thoracic synthetic CT (sCT) generation from MR data attenuation correction (AC) for PET/MR or for MR-only radiation treatment planning (RTP). Acquisition: A radial stack-of-stars combining ultra-short-echo time (UTE) and modified Dixon (mDixon) sequence was optimized for thoracic imaging. The UTE-mDixon pulse sequence collects MR signals at three TE times denoted as UTE, Echo1, and Echo2. Three-point mDixon processing was used to reconstruct water and fat images. Bias field correction was applied in order to avoid artifacts caused by inhomogeneity of the MR magnetic field. Water fraction and R2* maps were estimated using the UTE-mDixon data to produce a total of seven MR features, that is UTE, Echo1, Echo2, Dixon water, Dixon fat, Water fraction, and R2*. A feature selection process was performed to determine the optimal feature combination for the proposed automatic, 6-tissue classification for sCT generation. Fuzzy c-means was used for the automatic classification which was followed by voxel-wise attenuation coefficient assignment as a weighted sum of those of the component tissues. Performance evaluation: MR data collected using the proposed pulse sequence were compared to those using a traditional two-point Dixon approach. Image quality measures, including image resolution and uniformity, were evaluated using an MR ACR phantom. Data collected from 25 normal volunteers were used to evaluate the accuracy of the proposed method compared to the template-based approach. Notably, the template approach is applicable here, that is normal volunteers, but may not be robust enough for patients with pathologies. The free breathing UTE-mDixon pulse sequence yielded images with quality comparable to those using the traditional breath holding mDixon sequence. Furthermore, by capturing the signal before T2* decay, the UTE-mDixon image provided lung and bone information which the mDixon image did not. The combination of Dixon water, Dixon fat, and the Water fraction was the most robust for tissue clustering and supported the classification of six tissues, that is, air, lung, fat, soft tissue, low-density bone, and dense bone, used to generate the sCT. The thoracic sCT had a mean absolute difference from the template-based (reference) CT of less than 50 HU and which was better agreement with the reference CT than the results produced using the traditional Dixon-based data. MR thoracic acquisition and analyses have been established to automatically provide six distinguishable tissue types to generate sCT for MR-based AC of PET/MR and for MR-only RTP.

Effectiveness of High-Speed T2-Corrected Multiecho MR Spectroscopic Method for Quantifying Thigh Muscle Fat Content in Boys With Duchenne Muscular Dystrophy.

OBJECTIVE. The purpose of this study was to investigate the potential of high-speed T2-corrected multiecho (HISTO) MR spectroscopy (MRS) for rapidly quantifying the fat content of thigh muscles in children with Duchenne muscular dystrophy (DMD). SUBJECTS AND METHODS. This study prospectively enrolled 58 boys with DMD (mean age, 7.5 years; range, 4-11 years) and 30 age-matched healthy boys (mean age, 7.2 years; range, 4-11 years) at one institution over a 1-year period. T1- and T2-weighted, multiecho Dixon, and HISTO sequences were performed on the right adductor magnus and vastus lateralis muscles. The fat fractions of these muscles were acquired from HISTO and multiecho Dixon images. An experienced radiologist graded the degree of fat infiltration of the adductor magnus and vastus lateralis muscles on axial T1-weighted images. The Bland-Altman method was used to assess the consistency and repeatability of the HISTO sequence. Pearson linear correlation analysis was used to determine the correlation coefficient relating HISTO fat fraction to multiecho Dixon fat fraction values. Spearman rank correlation analysis was used to assess the relation between the HISTO fat fraction values and T1-weighted image fat infiltration grades. The independent t test was used to compare the HISTO fat fraction values of the boys with DMD with those of the healthy control subjects. RESULTS. Bland-Altman analysis showed that 95.5% of the HISTO fat fraction values of the adductor magnus were within the 95% CI. HISTO fat fraction and multiecho Dixon fat fraction values of the adductor magnus and vastus lateralis muscles were highly positively correlated (adductor magnus, r = 0.983; vastus lateralis, r = 0.967; p < 0.0001). HISTO fat fraction values were also highly positively correlated with the grades of fat infiltration on T1-weighted images (adductor magnus, r = 0.911; vastus lateralis, r = 0.937; p < 0.0001). The HISTO fat fraction of the adductor magnus muscle was 33.3% ± 22.6% and of the vastus lateralis muscle was 25.6% ± 20.3% in patients with DMD. The corresponding values were 2.9% ± 2.1% and 2.3% ± 1.9% in the control group. The differences were statistically significant (p < 0.0001). CONCLUSION. The HISTO sequence is a rapid and feasible noninvasive MRS technique for quantifying the fat infiltration of thigh muscles in children with known or suspected DMD. It is useful for diagnosis and for assessment of disease activity and prognosis.

Prospective respiratory triggering improves high-resolution brachial plexus MRI quality.

Oblique sagittal MRI sequences, orthogonal to the longitudinal axis of the brachial plexus, can reliably depict morphologic and signal abnormalities. However, nerve visualization may be obscured by ghosting artifact from periodic respiratory motion. Respiratory triggering (RT) with a thoracoabdominal bellows can reduce ghosting artifact, but it is not routinely used for brachial plexus MRI. Furthermore, the efficacy of prospective RT for brachial plexus imaging has not yet been reported. To compare brachial plexus MRI sequences acquired with and without respiratory triggering. Prospective. Five volunteers and 20 patients were included. Each subject was imaged with and without RT during the same session. Proton density or T2 -weighted Dixon fat suppressed sequences were obtained at 3.0T using receive-only 16-channel flexible array coils. Three musculoskeletal radiologists blindly evaluated each sequence using subjective scoring criteria for ghosting artifact, nerve conspicuity, and diagnostic confidence. Nerve conspicuity scores at three distinct plexus levels were summed to calculate an overall image quality score. Marginal proportional odds logistic regression models were used to compare all scores between RT and non-RT. Gwet's agreement coefficient was used to assess interobserver and intraobserver reliability. Mean scan time per sequence increased from 4:25 minutes (95% confidence interval [CI], 4:02-4:49 min) with non-RT to 6:09 minutes (95% CI, 5:42-6:35 min) with RT. RT reduced ghosting artifact (odds ratio [OR] = 0.21, 95% CI: 0.09-0.46, P < 0.001), improved overall image quality (OR = 4.88, 95% CI: 2.18-10.95, P < 0.001), and increased diagnostic confidence (OR = 3.72, 95% CI: 1.61-8.63, P = 0.002) for all readers. Interobserver agreement for ghosting artifact and image quality was substantial to almost perfect (AC2 = 0.74-0.85). Interobserver agreement for all other scores was moderate to almost perfect (AC2 = 0.61-0.82). Intraobserver agreement was substantial to almost perfect for all parameters (AC2 = 0.76-1.0). Prospective RT with bellows can effectively minimize ghosting artifact and improve image quality for brachial plexus MRI within clinically optimal acquisition times. 1 Technical Efficacy: Stage 2.

Differentiation and quantification of fibrosis, fat and fatty fibrosis in human left atrial myocardium using ex vivo MRI.

BackgroundAtrial fibrillation is associated with an atrial cardiomyopathy composed mainly of fibrosis and adipose tissue accumulation. We hypothesized that MRI, when used in an optimal ex vivo setting allowing high spatial resolution without motion artifacts, can help characterizing the complex 3D left atrial (LA) wall composition in human myocardial samples, as compared to histology.MethodsThis prospective case-control study was approved by the institutional review board. 3D MRI acquisitions including saturation-recovery T1 mapping and DIXON imaging was performed at 4.0 T on 9 human LA samples collected from patients who underwent cardiac surgery. Histological quantification of fibrosis and fat was obtained. MRI T1 maps were clustered based on a Gaussian Mixture Model allowing quantification of total, interstitial and fatty fibrosis components. Fat maps were computed from DIXON images and fat fractions were calculated. MRI measurements were performed on the same location as the histological analysis (plane) and on the entire sample volume (3D).ResultsHigh correlations and levels of agreement were observed between MRI and histology for total (r = 0.93), interstitial (r = 0.93) and fatty fibrosis (r = 0.98) and fat (r = 0.96). Native T1 correlated with the amount of fibrosis from MRI and histology. The 3D MRI total, interstitial and fatty fibrosis ranges were between 6% and 23%, 4% and 17.3%; and 1.4% and 19.7% respectively.ConclusionHigh Field ex vivo MRI was able to quantify different LA myocardial components with high agreement in 2D with histology and moreover to provide 3D quantification of such components whereas in vivo application remains a challenge.

The utility of chemical shift imaging and related fat suppression as standalone technique in cryptorchidism using low field MRI

Cryptorchidism is failure of one or both testes to descend completely into the scrotum. The testis can be located anywhere along its journey of descent, between the lower pole of the kidney and the inguinal canal. Objective: The aim of this study was to assess the effectiveness of chemical shift imaging and Dixon based fat suppression using low field MRI in non-palpable undescended testicle. Patients and methods: From July 2017 through February 2018, Twenty eight boys, presented by either unilateral or bilateral cryptorchidism, with total number of forty testicles, underwent MRI study using low field machine in T1-weighted dual gradient-echo in-phase and opposed-phase sequence with Dixon based fat suppression. Results: Based on the laparoscopic/operative data, twenty one testes were located at the inguinal region, whereas fifteen testes were pelvi-abdominal and four were absent. The whole image sets of CSI and Dixon fat suppression had the highest specificity and positive predictive value (100%) and the highest overall accuracy (95%) for detection of undescended testes. Conclusion: chemical shift imaging combined with Dixon based fat suppression is reliable imaging tool as a standalone technique for evaluating cryptorchidism, providing high specificity and diagnostic accuracy.

Efficacy of 3D VIBE Dixon fat quantification for differentiating clear-cell from non-clear-cell renal cell carcinoma

To assess the efficacy of three-dimensional (3D) volumetric interpolated breath-hold examination (VIBE) magnetic resonance imaging (MRI) with Dixon quantification for differentiating clear-cell from non-clear-cell types of renal cell carcinoma (RCC). The 3D VIBE Dixon renal MRI examinations of 44 patients with 45 histologically confirmed RCCs was analysed. The fat fractions and signal intensity indexes (SIindex) of the solid portions of clear-cell and non-clear-cell RCCs were measured and compared using Student's t-test and receiver operating characteristic (ROC) curves. The agreement of measurements among observers was evaluated by the intraclass correlation coefficient (ICC), and Bland-Altman plots. The mean values of fat fraction (13.16±7.16%) and SIindex (22.64±15.7%) in clear-cell RCCs were significantly higher than that in non-clear-cell RCCs (7.7±2% and 7.9±4.8%; p<0.001, respectively). With the area under the ROC curve (AUC) of the fat fraction at 0.811, 75% (95% CI: 55.1-89.43%) sensitivity and 76.5% (95% CI: 50.1-93.2%) specificity for diagnosing clear-cell RCC were obtained at a cut-off fat fraction value of 8.9%. With a cut-off value of 8.89%, the diagnostic sensitivity and specificity were 85.7% (95% CI: 67.3-96%) and 70.6% (95% CI: 44-89.7%), respectively. The AUC of the SIindex was 0.870 (0.766-0.973). ICC and Bland-Altman plots show excellent agreement of the tumour fat fraction and SIindex measurement between the two observers. Intracellular lipid content analysis using the 3D Dixon technique can help to differentiate clear-cell from non-clear-cell RCCs.

Determination of an Optimized Weighting Factor of Liver Parenchyma for Six-point Interference Dixon Fat Percentage Imaging Accuracy in Nonalcoholic Fatty Liver Disease Rat Model

The aim of this study was to determine the optimal weighting factor (WF) for precise quantification using six-point interference Dixon fat percentage imaging by analyzing changes in WFs of fatty acid metabolites (FMs) in high-fat-induced fatty liver disease rat model. Individual FM-related WFs were calculated based on concentration ratios of integrated areas of seven peak FMs with four phantom series. Ten 8-week-old male Sprague-Dawley rats were used for baseline quantification of fat in liver magnetic resonance imaging or magnetic resonance spectroscopy data. These seven lipid metabolites were then quantitatively analyzed. Spearman test was used for correlation analysis of different lipid proton concentrations. The most accurate WF for six-point interference Dixon fat percentage imaging was then determined. The seven lipid resonance WF values obtained from magnetic resonance spectroscopy data for three different oils (oleic, linoleic, and soybean) were different from each other. In lipid phantoms, except for the phantom containing oleic acid, changes in FP values were significantly different when WFs were changed in six-point interference Dixon fat percentage image. The seven lipid resonance WF values for the nonalcoholic fatty liver animal model were different from human subcutaneous adipose tissue lipid WF values. WF affected the calculation of six-point interference Dixon-based fat percentage imaging value in phantom experiment. If WF of liver parenchyma FM which is specific to each liver disease is applied, the accuracy of six-point interference Dixon fat percentage imaging can be further increased.

PERBEDAAN INFORMASI CITRA DIAGNOSTIK ANTARA SEKUEN T2 TSE STIR DAN T2 TSE DIXON PADA PEMERIKSAAN MRI LUMBAL POTONGAN SAGITAL DENGAN KASUS RADICULOPATHY

Backgroud: T2 Weighted Image Turbo Spin Echo Short Tau Inversion Recovery (T2 TSE STIR) is a sequence to get the image pathologic which can reveal of tissue along surrounding pathology with fat suppresion technique. T2 Weighted Image Turbo Spin Echo Dixon is a sequence to get the image pathologic whic can reveal of tissue along surrounding pathology with fat and water suppresion technique. Based on observations at Dr. Hasan Sadikin Bandung Hospital, in the examination of MRI Lumbal using T2 TSE sequence with Dixon fat suppresion technique, while according to The American College of Radiology (2012), using STIR fat suppresion technique. The purpose of this research was to know the difference of information diagnostic image that is produced between T2 TSE STIR and T2 TSE Dixon sequences on the examination of MRI lumbal sagittal slice with Radiculopathy case.&#x0D; Methods: This research of type is experiment. The study was conducted with a 1,5 Tesla MRI at Installation Radiology of General Hospital Dr. Hasan Sadikin Bandung. The research took from of the 22 images of MRI lumbal sagittal slice from T2 TSE STIR and T2 TSE Dixon sequences with Radiculopathy cases. Assesment of the image was done by two respondents and Kappa test was conducted. Furthermore, the results of respondents assessment was analyzed by Wilcoxon different test.&#x0D; Results: The results showed that the research result Ho rejected and Ha accepted which mean there is a differences of information diagnostic image between T2 TSE STIR and T2 TSE Dixon sequences on the examination of MRI lumbal sagittal slices with Radiculopathy case with p value = 0,001 (p &lt;0,05).&#x0D; Conclusion: T2 Sequence TSE Dixon can produce MRI images with more specific and homogeneous fat suppresion, thus providing more informative diagnostic information than T2 TSE STIR sequences.

Left Atrial Epicardial Fat Volume Is Associated With Atrial Fibrillation: A Prospective Cardiovascular Magnetic Resonance 3D Dixon Study.

BackgroundRecent studies demonstrated a strong association between atrial fibrillation (AF) and epicardial fat around the left atrium (LA). We sought to assess whether epicardial fat volume around the LA is associated with AF, and to determine the additive value of LA‐epicardial fat measurements to LA structural remodeling for identifying patients with AF using 3‐dimensional multi‐echo Dixon fat–water separated cardiovascular magnetic resonance.Methods and ResultsA total of 105 subjects were studied: 53 patients with a history of AF and 52 age‐matched patients with other cardiovascular diseases but no history of AF. The 3‐dimensional multi‐echo Dixon fat‐water separated sequence was performed for LA‐epicardial fat measurements. AF patients had significantly greater LA‐epicardial fat (28.9±12.3 and 14.2±7.3 mL for AF and non‐AF, respectively; P<0.001) and LA volume (110.8±38.2 and 89.7±30.3 mL for AF and non‐AF, respectively; P=0.002). LA‐epicardial fat adjusted for LA volume was still higher in patients with AF compared with those without AF (P<0.001). LA‐epicardial fat and hypertension were independently associated with the risk of AF (odds ratio, 1.17; 95% confidence interval, 1.10%–1.25%, P<0.001, and odds ratio, 3.29; 95% confidence interval, 1.17%–9.27%, P=0.03, respectively). In multivariable logistic regression analysis adjusted for body surface area, LA‐epicardial fat remained significant and an increase per mL was associated with a 42% increase in the odds of AF presence (odds ratio, 1.42; 95% confidence interval, 1.23%–1.62%, P<0.001). Combined assessment of LA‐epicardial fat and LA volume provided greater discriminatory performance for detecting AF than LA volume alone (c‐statistic=0.88 and 0.74, respectively, DeLong test; P<0.001).ConclusionsCardiovascular magnetic resonance 3‐dimensional Dixon‐based LA‐epicardial fat volume is significantly increased in AF patients. LA‐epicardial fat measured by 3‐dimensional Dixon provides greater performance for detecting AF beyond LA structural remodeling.

Time-resolved contrast-enhanced MR angiography with single-echo Dixon fat suppression.

Dixon-based fat suppression has recently gained interest for dynamic contrast-enhanced MRI, but multi-echo techniques require longer scan times and reduce temporal resolution compared to single-echo alternatives without fat suppression. The purpose of this work is to demonstrate accelerated single-echo Dixon imaging with high spatial and temporal resolution. Real-valued water and fat images can be obtained from a single measurement if the shared initial phase and that due to ΔB0 are assumed known a priori. An expression for simultaneous sensitivity encoding (SENSE) unfolding and fat-water separation is derived for the general undersampling case, and simplified under the special case of uniform Cartesian undersampling. In vivo experiments were performed in extremities and brain with SENSE acceleration factors of up to R = 8. Single-echo Dixon reconstruction of highly undersampled data was successfully demonstrated. Dynamic contrast-enhanced water and fat images provided high spatial and temporal resolution dynamic images with image update times shorter than previous single-echo Dixon work. Time-resolved contrast-enhanced MRI with single-echo Dixon fat suppression shows high image quality, improved vessel delineation, and reduced sensitivity to motion when compared to time-subtraction methods.

Fat suppression in magnetic resonance imaging of the head and neck region: is the two-point DIXON technique superior to spectral fat suppression?

The aim of our study was to systematically compare two-point Dixon fat suppression (FS) and spectral FS techniques in contrast enhanced imaging of the head and neck region. Three independent readers analysed coronal T1 weighted images recorded after contrast medium injection with Dixon and spectral FS techniques with regard to FS homogeneity, motion artefacts, lesion contrast, image sharpness and overall image quality. 85 patients were prospectively enrolled in the study. Images generated with Dixon-FS technique were of higher overall image quality and had a more homogenous FS over the whole field of view compared with the standard spectral fat-suppressed images (p < 0.001). Concerning motion artefacts, flow artefacts, lesion contrast and image sharpness no statistically significant difference was observed. The Dixon-FS technique is superior to the spectral technique due to improved homogeneity of FS and overall image quality while maintaining lesion contrast. Advances in knowledge: T1 with Dixon FS technique offers, compared to spectral FS, significantly improved FS homogeneity and over all image quality in imaging of the head and neck region.