Chemical Shift Magnetic Resonance Imaging Research Articles

Imaging and prognostic characterization of fat-containing hepatocellular carcinoma subtypes.

Steatohepatitic hepatocellular carcinoma (SH-HCC) is characterized by intratumoral fat with > 50% inflammatory changes. However, intratumoral fat (with or without inflammation) can also be found in not-otherwise specified HCC (NOS-HCC). We compared the imaging features and outcome of resected HCC containing fat on pathology including SH-HCC (> 50% steatohepatitic component), NOS-HCC with < 50% steatohepatitic component (SH-NOS-HCC), and fatty NOS-HCC (no steatohepatitic component). From September 2012 to June 2021, 94 patients underwent hepatic resection for fat-containing HCC on pathology. Imaging features and categories were assessed using LIRADS v2018. Fat quantification was performed on chemical-shift MRI. Recurrence-free and overall survival were estimated. Twenty-one patients (26%) had nonalcoholic steatohepatitis (NASH). The median intra-tumoral fat fraction was 8%, with differences between SH-HCC and SH-NOS-HCC (9.5% vs. 5% p = 0.03). There was no difference in major LI-RADS features between all groups; most tumors were classified as LR-4/5. A mosaic architecture on MRI was rare (7%) in SH-HCC, a fat in mass on CT was more frequently depicted (48%) in SH-HCC. A combination of NASH with no mosaic architecture on MRI or NASH with fat in mass on CT yielded excellent specificity for diagnosing SH-HCC (97.6% and 97.7%, respectively). The median recurrence-free and overall survival were 58 and 87months, with no difference between groups (p = 0.18 and p = 0.69). In patients with NASH, an SH-HCC may be suspected in L4/LR-5 observations with no mosaic architecture at MRI or with fat in mass on CT. Oncological outcomes appear similar between fat-containing HCC subtypes.

Diagnostic performance of hepatic CT and chemical-shift MRI to discriminate lipid-poor adrenal adenomas from hepatocellular carcinoma metastases.

To evaluate the diagnostic performance of multiphase hepatic CT parameters (non-contrast attenuation, absolute and relative washout ratios [APW and RPW, respectively], and relative enhancement ratio [RER]) and chemical-shift MRI (CS-MRI) for discriminating lipid-poor adrenal adenomas (with non-contrast CT attenuation > 10 HU) from metastases in patients with hepatocellular carcinoma (HCC). This retrospective study included HCC patients with lipid-poor adrenal lesions who underwent multiphase hepatic CT between January 2010 and December 2021. For each adrenal lesion, non-contrast attenuation, APW, RPW, RER, and signal-intensity index (SI-index) were measured. Each parameter was compared between adenomas and metastases. The area under the receiver operating characteristic curves (AUCs) and sensitivities to achieve 100% specificity for adenoma diagnoses were determined. 104 HCC patients (78 men; mean age, 71.8 ± 9.6years) with 63 adenomas and 48 metastases were identified; CS-MRI was performed in 66 patients with 49 adenomas and 21 metastases within one year of CT. Lipid-poor adenomas showed lower non-contrast attenuation (22.9 ± 7.1 vs. 37.9 ± 9.4 HU) and higher APW (40.5% ± 12.8% vs. 23.7% ± 17.4%), RPW (30.0% ± 10.2% vs. 12.4% ± 9.6%), RER (329% ± 152% vs. 111% ± 43.0%), and SI-index (43.3 ± 20.7 vs. 10.8 ± 13.4) than HCC metastases (all p < .001). AUC for non-contrast attenuation, APW, RPW, RER, and SI-index were 0.894, 0.786, 0.904, 0.969, and 0.902, respectively. The sensitivities to achieve 100% specificity were 7.9%, 25.4%, 30.2%, 63.5%, and 24.5%, respectively. Combined RER and APW achieved the highest sensitivity of 73.0%. Multiphase hepatic CT allows for better discrimination between lipid-poor adrenal adenomas and metastases relative to CS-MRI, especially when combined with RER and washout parameters.

Value of chemical shift imaging in the evaluation of neural foramen stenosis

BackgroundChemical shift Magnetic Resonance Imaging (MRI) is often routinely acquired to assess a spectrum of spinal lesions due to its ability versatility to obtain rapid sequences at the expense of spatial resolution images. It is one of the quickest sequences to acquire at the expense of spatial resolution. ObjectiveIn this study we assess the diagnostic efficacy of Chemical shift Magnetic Resonance Imaging (MRI) in the evaluation of Neural Foraminal stenosis. Materials and methodsConventional T2, T1 and STIR sagittal and axial images as well as ‘in’ and ‘out’ phase chemical shift sagittal MRI sequences of 25 consecutive patients presenting with back pain and radiculopathy were reviewed. The degree of neural stenosis in the lumbar spine foramina on both sides was graded using the Lee classification on T2 and ‘in’ and ‘out’ phase MRI sequences by two independent MSK radiologists. Statistical analysis was performed using paired T-Test and Cohen's weighted kappa test was applied as a measure of agreement between the two observed raters. ResultsA total of 250 lumbar neural foramina were assessed. There was substantial agreement (Cohen's weighted kappa) for both raters between ‘in’ and ‘out’ phase chemical shift sagittal MRI sequences (rater 1 = 0.699, rater 2 = 0.718), as well as good agreement between raters for both ‘in’ and ‘out’ phase chemical shift sagittal MRI sequences (in phase = 0.656, ‘out’ phase = 0.576). However, when compared to the gold standard rating on a T2 based sequence, ratings on in’ and ‘out’ phase MRI sequences overestimated the degree of stenosis. When comparing ‘in’ and ‘out’ ratings to the T2 ratings, agreement was poor with kappa ranging from 0.132 to 0.202. ConclusionThough both ‘in’ and ‘out’ phase chemical shift sagittal MRI sequences can be used to analyse neural foraminal stenosis, given its propensity to over-estimate the degree of stenosis in comparison to the T2 based images, assessment of the condition on these complementary limited sequences technique should be avoided/should be undertaken with caution.

Evaluation of the parenchymal distribution of renal steatosis in chronic kidney disease using chemical shift magnetic resonance imaging.

Renal steatosis is an abnormal accumulation of fat in the kidney and may cause chronic kidney disease (CKD) or CKD progression. This pilot study aimed to evaluate the quantitative measurability of the parenchymal distribution of lipid deposition in the renal cortex and medulla using chemical shift magnetic resonance imaging (MRI) and investigate its relationship with clinical stages in CKD patients. The study groups included CKD patients with diabetes (CKD-d) (n = 42), CKD patients without diabetes (CKD-nd) (n = 31) and control subjects (n = 15), all of whom underwent a 1.5T MRI of the abdomen using the Dixon two-point method. The fat fraction (FF) values in the renal cortex and medulla were calculated from measurements made on Dixon sequences, and then compared between the groups. The cortical FF value was higher than the medullary FF value in control (0.057 (0.053-0.064) compared to 0.045 (0.039-0.052)), CKD-nd (0.066 (0.059-0.071) compared to 0.063 (0.054-0.071)), and CKD-d (0.081 (0.071-0.091) compared to 0.069 (0.061-0.077)) groups (all p < 0.001). The CKD-d group cortical FF values were higher than those of the CKD-nd group (p < 0.001). The FF values began increasing at CKD stages 2 and 3, and reached statistical significance at stages 4 and 5 in CKD patients (p < 0.001). Renal parenchymal lipid deposition can be quantified separately in the cortex and medulla using chemical shift MRI. Fat accumulation occurred in cortical and medullary parenchyma in CKD patients, though predominantly in the cortex. This accumulation increased proportionally with the disease stage.

Using the “2 standard deviations” rule with Dixon MRI to differentiate renal cell carcinoma types

BackgroundClear cell and non-clear cell renal cell carcinoma (RCC) are distinguishable based on microscopic fat, detectable by chemical shift MRI. However, these assessments are often subjective. Conversely, Dixon MRIs and the “2 standard deviations” rule (2SDR) are quantitative methods that may decrease diagnostic subjectivity. Therefore, this study assessed the value of the 2SDR for detecting microscopic fat and thus differentiating clear cell and non-clear cell RCC using Dixon MRI. MethodsThis retrospective study included patients with RCC who underwent preoperative Dixon MRI. The patients were grouped based on tumor type: clear cell RCC and non-clear cell RCC. The 2SDR value was calculated based on in-phase and opposed-phase images and then compared between the two groups. 2SDR values >0 indicated clear cell RCCs, whereas values <0 indicated non-clear cell RCC. ResultsWe included 151 patients; 114 patients had clear cell RCC, of which 106 had a 2SDR value >0. Furthermore, 37 patients had non-clear cell RCC, of which 3 had a 2SDR value >0. The 2SDR value was significantly higher in the clear cell RCC group than in the non-clear cell RCC group (p = 0.000). Overall, 93.0% (106/114) and 8.1% (3/37) of patients with clear cell and non-clear cell RCC, respectively, had microscopic fat. The evaluation indices for this 2SDR method were: accuracy: 92.72%, sensitivity: 92.98%, specificity: 91.89%, positive predictive value: 97.25%, and negative predictive value: 80.95%. Conclusions2SDR values calculated from Dixon magnetic resonance images can differentiate clear cell from non-clear cell RCCs by detecting microscopic fat. PrecisThe “2 standard deviations” rule value calculated from Dixon MR images differentiates clear cell from non-clear cell renal cell carcinoma with high efficiency by detecting microscopic fat.

Colonic permeability is increased in non-cirrhotic patients with nonalcoholic fatty liver disease.

Intestinal permeability (IP) plays an important role in the pathophysiology of nonalcoholic fatty liver disease (NAFLD). We assessed site-specific (gastroduodenum, small intestine, colon and whole gut) IP in NAFLD patients and healthy controls (HC) and its association with the degree of hepatic steatosis, hepatic fibrosis and dietary composition in these NAFLD patients. In vivo site-specific IP was analysed with a validated multi-sugar test in NAFLD patients and HC. Furthermore, in NAFLD patients, hepatic steatosis (chemical shift MRI), hepatic fibrosis (transient elastography) and dietary composition (food frequency questionnaire) were assessed. Fifty-two NAFLD patients and forty-six HC were included in this study. Small intestinal (P <0.001), colonic (P=0.004) and whole gut (P <0.001) permeability were increased in NAFLD patients compared to HC. Furthermore, colonic permeability (P=0.029) was significantly higher in NAFLD patients with clinically significant fibrosis compared to those without. Colonic permeability remained positively associated with the presence of clinically significant fibrosis (P=0.017) after adjustment for age, sex and BMI. Colonic permeability is increased in at least a subset of NAFLD patients compared to HC and is independently associated with clinically significant NAFLD fibrosis.

Does Chemical Shift Magnetic Resonance Imaging Improve Visualization of Pars Interarticularis Defect?

Introduction A unilateral or bilateral pars interarticularis defect (spondylolysis) is a leading cause of axial back pain in adolescent athletes. Currently, a spectrum of imaging modalities is used for assessment of pars interarticularis defects. Objectives The aim of this study is to compare the accuracy of chemical shift sequence (magnetic resonance imaging [MRI]) technique to conventional MRI sequences in the detection of pars defects. Patients and Methods Conventional T1, T2, and short tau inversion recovery sagittal and axial, as well as "in-" and "out-" phase chemical shift sagittal MRI sequences of 70 consecutive patients referred for low back pain were reviewed. Demographic details, clinical indication, and presence/diagnosis of pars defects using a 5-point Likert scale on both conventional and chemical shift MRI sequences. Spearman's correlation was used for statistical analysis. Intraclass correlation coefficient analysis was evaluated to assess the intraclass reliability between observers. Data were analyzed using DATAtab web-based statistics software (2022). Results A total of 70 patients with an average age of 54.34 years with a female predominance were included. There were 11 pars defects in the cohort. Both in and out phases of chemical shift imaging were able to identify pars defect and intact pars. However, out phase was relatively better in delineating pars defects, while the in phase was superior in identifying an intact pars, though this was not statistically significant. There was good intra- and interobserver reliabilities. Conclusion Chemical shift MRI sequence is a quicker, complementary technique to assess and analyze pars interarticularis confidently than conventionally utilized MRI sequences in patients being evaluated for axial back pain.

Multiparametric magnetic resonance imaging for characterizing renal tumors: A validation study of the algorithm presented by Cornelis et al.

In the last decade, the incidence of renal cell carcinoma (RCC) has been rising, with the greatest increase observed for solid tumors. Magnetic resonance imaging (MRI) protocols and algorithms have recently been available for classifying RCC subtypes and benign subtypes. The objective of this study was to prospectively validate the MRI algorithm presented by Cornelis et al. for RCC classification. Over a 7-month period, 38 patients with 44 renal tumors were prospectively included in the study and received an MRI examination in addition to the conventional investigation program. The MRI sequences were: T2-weighted, dual chemical shift MRI, diffusion-weighted imaging (DWI), and dynamic contrast-enhanced T1-weighted in wash-in and wash-out phases. The images were evaluated according to the algorithm by two experienced, blinded radiologists, and the histopathological diagnosis served as the gold standard. Of 44 tumors in 38 patients, only 8 tumors (18.2%) received the same MRI diagnosis according to the algorithm as the histopathological diagnosis. MRI diagnosed 16 angiomyolipoma, 14 clear cell RCC (ccRCC), 12 chromophobe RCC (chRCC), and two papillary RCC (pRCC), while histopathological examination diagnosed 24 ccRCC, four pRCC, one chRCC, and one mixed tumor of both pRCC and chRCC. Malignant tumors were statistically significantly larger than the benign (3.16 ± 1.34 cm vs. 2.00 ± 1.04 cm, P = 0.006). This prospective study could not reproduce Cornelis et al.'s results and does not support differentiating renal masses using multiparametric MRI without percutaneous biopsy in the future. The MRI algorithm showed few promising results to categorize renal tumors, indicating histopathology for clinical decisions and follow-up regimes of renal masses are still required.

RF24 | PSUN126 A Very-Low Calorie Diet Can Reduce Insulin Resistance and Cause Remission of Diabetes Mellitus and Hypertriglyceridemia in a Patient With Familial Partial Lipodystrophy Type 2

Abstract Background Lipodystrophy syndromes are associated with inadequate adipocyte capacity that results in an earlier threshold for ectopic deposition and metabolic dysfunction. We have previously reported that patients with familial partial lipodystrophy (FPLD) present with metabolic severity equivalent to what is observed at 8-12 BMI points higher in a population with common obesity. Currently, there is no strong evidence that any specific diet is the preferred treatment, but bariatric surgery has been reported to improve metabolic outcomes in a few patients. Here, we report the effect of an aggressive calorie-restricted diet in a patient with FPLD who showed remarkable benefit after 16 weeks of the intervention. Clinical Case This is a 38-year-old female diagnosed with FPLD type 2, with LMNA p. R482Q mutation who had a history of recurrent pancreatitis, NAFLD, impaired ovulation, and diabetes mellitus. She had a short-term goal of improving her metabolic state rapidly to achieve pregnancy by IVF. Upon presentation, body weight was 81.6kg, BMI 23.2kg/m2, HbA1c 7.7% and triglycerides 215mg/dL. She was started on very-low calorie diet (VLCD) (800 kcal/day) employing a formula total liquid diet meal replacement: 160 kcal per shake (18g total carbohydrates, 15g net carbohydrates, 3.5g fat, and 16g protein) with the goal to reduce body weight by 15% as has been described for patients in the University of Michigan Weight Management Program. After 1 week on diet, she discontinued glucose and lipid lowering therapies. After 12-weeks of VLCD followed by 4 weeks of transition to low-calorie diet (incorporating 3 meal replacements, one meal, and ad libitum non-starchy vegetables), we observed 12.3kg of body weight and a 1.4% decrease in HbA1c. Insulin resistance was reduced by 66.7 and 61.5% (HOMA-IR and ADIPO-IR, respectively). Fasting insulinemia was reduced by 64.2%. We also performed an OGTT with 75g of glucose for 180 min and observed a decrease in the area under the curve of insulin (-33.2%), triglycerides (-40.7%), and free fatty acids (-34%). DEXA scan showed a reduction in total body fat of 16%. Liver fat via the chemical shift MRI method was reduced from 10±2% to 2±1%. She did not experience any adverse events during the intervention. More importantly, her egg retrieval rate and egg quality during IVF were far superior to past attempts. Conclusion This case illustrates the strong effect and safety of a VLCD intervention in a patient with lipodystrophy. We observed rapid reduction in body weight, and in insulin resistance leading to the remission of diabetes mellitus, hypertriglyceridemia and fatty liver disease. Moreover, there was improved response to ovulation induction. Our data encourage the use of this medical approach for other patients with similar metabolic and reproductive abnormalities due to adipose tissue distribution abnormalities. Presentation: Sunday, June 12, 2022 12:30 p.m. - 2:30 p.m., Sunday, June 12, 2022 12:36 p.m. - 12:41 p.m.

Prevalence of Malignancy in Adrenal Nodules With Heterogeneous Microscopic Fat on Chemical-Shift MRI: A Multiinstitutional Study.

BACKGROUND. Homogeneous microscopic fat within adrenal nodules on chemical-shift MRI (CS-MRI) is diagnostic of benign adrenal adenoma, but the clinical relevance of heterogeneous microscopic fat is not well established. OBJECTIVE. This study sought to determine the prevalence of malignancy in adrenal nodules with heterogeneous microscopic fat on dual-echo T1-weighted CS-MRI. METHODS. We performed a retrospective study of adult patients with adrenal nodules detected on MRI performed between August 2007 and November 2020 at seven institutions. Eligible nodules had a short-axis diameter of 10 mm or larger with heterogeneous microscopic fat (defined by an area of signal loss of < 80% on opposed-phase CS-MRI). Two radiologists from each center, blinded to reference standard results, determined the signal loss pattern (diffuse, two distinct parts, speckling pattern, central loss, or peripheral loss) within the nodules. The reference standard used was available for 283 nodules (pathology for 21 nodules, ≥ 1 year of imaging follow-up for 245, and ≥ 5 years of clinical follow-up for 17) in 282 patients (171 women and 111 men; mean age, 60 ± 12 [SD] years); 30% (86/282) patients had prior malignancy. RESULTS. The mean long-axis diameter was 18.7 ± 7.9 mm (range, 10-80 mm). No malignant nodules were found in patients without prior cancer (0/197; 95% CI, 0-1.5%). Four of the 86 patients with prior malignancy (hepatocellular carcinoma [HCC], renal cell carcinoma [RCC], lung cancer, or both colon cancer and RCC) (4.7%; 95% CI, 1.3-11.5%) had metastatic nodules. Detected patterns were diffuse heterogeneous signal loss (40% [114/283]), speckling (28% [80/283]), two distinct parts (18% [51/283]), central loss (9% [26/283]), and peripheral loss (4% [12/283]). Two metastases from HCC and RCC showed diffuse heterogeneous signal loss. Lung cancer metastasis manifested as two distinct parts, and the metastasis in the patient with both colon cancer and RCC showed peripheral signal loss. CONCLUSION. Presence of heterogeneous microscopic fat in adrenal nodules on CS-MRI indicates a high likelihood of benignancy, particularly in patients without prior cancer. This finding is also commonly benign in patients with cancer; however, caution is warranted when primary malignancies may contain fat or if the morphologic pattern of signal loss may indicate a collision tumor. CLINICAL IMPACT. In the absence of prior cancer, adrenal nodules with heterogeneous microscopic fat do not require additional imaging evaluation.

Comparison of image quality and depiction of microscopic fat at 2-D and 3-D T1-Weighted (T1W) chemical shift (dual-echo) MRI for evaluation of adrenal adenomas.

To compare image quality and detection of microscopic fat in adrenal adenomas imaged with 2-D and 3-D chemical shift imaging (CSI) and, to derive parameters which best match 2-D and 3-D-CSI. This two-phase, retrospective, and phantom + prospective study was IRB approved. First, a retrospective assessment of 50 consecutive adrenal adenomas imaged at 1.5T with 2-D (TR minimum, Flip Angle [FA] 70°, TE 2.2/4.4ms.) and 3-D (TR minimum, FA 10°, TE 2.2/4.4ms.] CSI was performed. Second, phantom (varied fat: water concentration) experiments guided a prospective assessment of 12 consecutive adrenal adenomas imaged at 1.5T with 3-D CSI (FA 10°, 18°). Two blinded radiologists independently evaluated: image quality, signal intensity (SI) cancellation (5-point Likert scale), and CSI-index ([SI.In.Phase-SI.Opposed.Phase/SI.In.Phase]*100). 2-D-CSI yielded higher image quality (p < 0.001) and, subjectively (p < 0.001) and quantitatively (p < 0.001) had more SI cancellation from microscopic fat. Proportion of adenomas with no detectable microscopic fat (3-D; 26-36% subjectively, 18-24% quantitatively [CSI-index < 16.5%] versus 2-D; 20-22% subjectively, 6-8% quantitatively) differed (p = 0.008-0.08 subjectively, 0.008-0.03 quantitatively) by CSI technique. Phantom experiments indicated 18°FA 3-D-CSI compared favorably to 70° 2-D-CSI for fat detection between 5% and 50%. In vivo, there was no differences in subjective or quantitative SI cancellation comparing 18°3D-CSI and 2D-CSI (p = 0.16-0.56 and 0.73-0.60). Greater SI cancellation occurred with 18°3D compared to 10°3D-CSI evaluated subjectively (p = 0.003-0.01). 2-D CSI has subjectively higher image quality and shows more signal intensity loss from microscopic fat in adrenal adenomas compared to 10° flip angle 3-D-CSI. Increasing the 3-D flip angle to 18° more closely matches depiction of microscopic fat to 2-D-CSI at 1.5T.

Lumbar Spine Bone Mineral Density Measurement: Comparison of Dual-Energy X-Ray Absorptiometry and Fat Content Evaluation by Dixon Chemical Shift MRI.

BackgroundTo assess whether the fat signal intensity and fat fraction (FF) of the lumbar vertebrae as measured on the Dixon chemical shift magnetic resonance imaging (MRI) technique can be correlated with the lumbar vertebra bone mineral density (BMD) measured using dual-energy X-ray absorptiometry (DXA).MethodsForty-five patients were retrospectively collected, and 180 lumbar vertebral bodies (L1-L4) were included. All patients underwent DXA and MRI examinations of the lumbar spine. Taking the T value of DXA as the gold standard and using the diagnostic criteria of the World Health Organization: T score ≥ −1.0SD as normal, −1.0 ~ −2.5SD as osteopenia, and ≤ −2.5SD as osteoporosis. Meanwhile, the signal intensity on T2WI was measured, and FF of L1-L4 vertebral bodies was calculated on MRI images. Bone marrow fat FF calculation formula: FF = [Mfat/(Mfat + Mwater)] × 100% (Mwater and Mfat refer to the total pixel signal intensity value of the region of interest in water image and lipid image, respectively). Finally, the association of signal intensity and FF with DXA was evaluated.ResultsTotally 180 vertebral bodies in 45 patients were enrolled. According to the T value, they were divided into the normal group (n = 70), osteopenia group (n = 40), and osteoporosis group (n = 70). The fat signal intensity of the normal group, osteopenia group, and osteoporosis group were 96.6 ± 21.8, 154.5 ± 48.7, 216.3 ± 92.6, and the FF were 30.1 ± 6.2%, 52.6 ± 7.6%, 77.5 ± 7.9%, respectively. Among the three groups, the lumbar T2 fat signal intensity and FF had statistical differences (P < 0.01). Besides, the lumbar fat signal intensity and FF were negatively related to DXA (r =−0.65 and −0.93, P < 0.01).ConclusionThe fat content calculated using the Dixon chemical shift MRI had an inverse relation with BMD. Moreover, the Dixon chemical shift MRI might provide complementary information to osteoporosis-related research fields.

A machine learning approach to distinguishing between non-functioning and autonomous cortisol secreting adrenal incidentaloma on magnetic resonance imaging using texture analysis.

To investigate the possibility of distinguishing between nonfunctioning adrenal incidentalomas (NFAI) and autonomous cortisol secreting adrenal incidentalomas (ACSAI) with a model created with magnetic resonance imaging (MRI)-based radiomics and clinical features. In this study, 100 adrenal lesions were evaluated. The lesions were segmented on unenhanced T1-weighted in-phase (IP) and opposed-phase (OP) as well as on T2-weighted (T2-W) 3Tesla MRIs. The LASSO regression model was used to select potential predictors from 108 texture features for each sequence. Subsequently, a combined radiomics score and clinical features were created and compared. A significant difference was found between median rad-scores for ACSAI and NFAI in training and test sets (p < 0.05 for all sequences). Multivariate logistic regression analysis revealed that the length of the tumor (OR = 1.09, p = 0.007) was an independent risk factor related to ACSAI. Multivariate logistic regression analysis was used for building clinical-radiomics (combined) models. The Op, IP, and IP plus T2-W model had a higher performance with area under curve (AUC) 0.758, 0.746, and 0.721 on the test dataset, respectively. ACSAI can be distinguished from NFAI with high accuracy on unenhanced MRI. Radiomics analysis and the model constructed by machine learning algorithms seem superior to another radiologic assessment method. The inclusion of chemical shift MRI and the length of the tumor in the radiomics model could increase the power of the test.

Inter-individual comparison of diagnostic accuracy of adrenal washout CT compared to chemical shift MRI plus the T2-weighted (T2W) adrenal MRI calculator in indeterminate adrenal masses: a retrospective non-inferiority study.

To compare diagnostic accuracy of washout (WO)-CT to chemical shift (CS)-MRI + T2W adrenal MRI Calculator (T2W-Calculator) to diagnose adrenal adenoma in indeterminate adrenal masses. This retrospective, cross-sectional, non-inferiority study evaluated 40 consecutive indeterminate adrenal masses; each with WO-CT and MRI. Two blinded radiologists independently evaluated in mixed order: pre-contrast attenuation (Hounsfield Units, HU) and absolute WO ([Peak.HU-Delay.HU]/[Peak.HU-Pre.HU] × 100%), Chemical Shift Signal Intensity (CS-SI) Index, T2W SI ratio, and Entropy (which were imputed into the T2W-Calculator). Diagnostic accuracy for adrenal adenoma was tabulated using 2 × 2 tables. True -positive diagnoses of adenoma were CT = Pre-HU < 10 or absolute WO ≥ 60%, MRI = SI index ≥ 16.5% or T2W-Calculator < 0.631. There were 73% (29/40) adenomas and 27% (11/40) other masses (5 pheochromocytoma, 3 solitary fibrous tumor, 1 metastasis, 1 cavernous hemangioma, and 1 adrenocortical carcinoma). Sensitivity, specificity, and accuracy for diagnosis of adenoma using CT-WO were 78% (95% confidence intervals [CI] 56-93%), 35% (14-62%), and 57% (42-71%) Reader 1 and 72% (53-87%), 46% (17-77%), and 59% (41-76%) Reader 2. Sensitivity, specificity, and accuracy for diagnosis of adenoma using MRI were 100% (88-100%), 64% (34-90%), and 82% (67-97%) Reader 1 and 86% (68-96%), 73% (39-94%), and 80% (64-95%) Reader 2. MRI had higher overall accuracy (p = 0.02 Reader 1, 0.05 Reader 2) compared to CT-WO. Chemical shift MRI combined with the T2W adrenal MRI calculator is not inferior to CT Washout for diagnosis of adrenal adenoma among indeterminate adrenal masses.

The Utility of Multiparametric MRI or Difffferentiating Adrenal Adenomas from Adrenal Metastases

Purpose: To evaluate the possibility of multiparametric MRI in the differential diagnosis of benign adrenal adenomas and adrenal metastases.Material and methods: In our study we evaluated 27 adenomas and 13 adrenal metastases using MRI in 35 patients who underwent examination and treatment at the basis of the N.N. Blokhin National Research Center of Oncology during the follow-up period from 2019 to 2021. The following parameters were evaluated: contours, homogeneity (homogeneous and heterogeneous), T2-weighted SI ratio (isointensive, moderately hyperintensive or sharply hyperintensive) relative to muscle and spleen, signal intensity (SI) decrease on chemical-shift MRI, measurement of the chemical-shift SI index, adrenal-to-spleen SI ratio, areas under the ROC curve (AUC) for contrast-enhanced MRI, absolute and relative percentage wash-out. Sensitivity, specificity, and positive and negative predictive values were calculated. DWI with b-values 400 and 800 s/mm2 and ADCs imaging were measured in adrenal lesions.Results: Metastases were subjectively more heterogeneous than adenomas (76.9 % vs 63 % of cases, p = 0.0181). Adenomas had higher T2-weighted SI (average value = 228; range from 91 to 732) than metastases (average value = 331; range from 114 to 581), both quantitatively (p = 0.0326) and subjectively by visual assessment (p = 0.0171).According to the T1-WI out-of-phase data, a more intense MR signal was observed in metastases (average value 162; range from 102 to 242) compared with adenomas (average value = 74; range from 17 to 183) (p &lt; 0.0001), which was confirmed by normalization to muscle (p &lt; 0.0001) and spleen (p = 0.0002). Adrenal metastases were characterized by a significantly lower chemical shift index (average value = 3.8; range from –16.4 to 47.8; p &lt; 0.0001) compared with adenomas (average value 55.4; range from –4.2 to 85.5), and a higher chemical shift index in the ratio adrenal gland/spleen (p = 0.0079). There were no significant difference in the value of ADC-cards of adenomas and adrenal metastases. However, a higher level of SI on DWI at b = 800 s/ mm2 without normalization (p = 0.0262) and with normalization to muscle (p = 0.0064) and spleen (p = 0.0007) was evaluated in metastases, as well as on DWI at b = 400 s/mm2 with normalization for muscle (p = 0.0086) and spleen (p = 0.035). On native T1-WI FS, there was a lower level of SI revealed in adenomas compared to adrenal metastases (p = 0.0025), which was confirmed by normalization to the muscle (p = 0.0028) and spleen (p = 0.0035). In the venous and delayed phases of scanning the SI in adenomas was also lower than in metastases both without normalization (p = 0.0123 and p = 0.007, respectively), and with normalization to the muscle (p = 0.013 and p = 0.0011, respectively) and the spleen (p = 0.0084 and p = 0.0012, respectively). However, the SI in the arterial phase of scanning with and without normalization, the accumulation of MRCS in all phases of MRI scanning, the absolute and relative percentage wash-out of MRCS and the area under the MRCS accumulation curve in the groups had no statistically significant difference.

Reliability and agreement of lumbar multifidus volume and fat fraction quantification using magnetic resonance imaging

IntroductionMagnetic resonance imaging (MRI) is the standard to quantify size and structure of lumbar muscles. Three-dimensional volumetric measures are expected to be more closely related to muscle function than two-dimensional measures such as cross-sectional area. Reliability and agreement of a standardized method should be established to enable the use of MRI to assess lumbar muscle characteristics. ObjectivesThis study investigates the intra- and inter-processor reliability for the quantification of (1) muscle volume and (2) fat fraction based on chemical shift MRI images using axial 3D-volume measurements of the lumbar multifidus in patients with low back pain. MethodsTwo processors manually segmented the lumbar multifidus on the MRI scans of 18 patients with low back pain using Mevislab software following a well-defined method. Fat fraction of the segmented volume was calculated. Reliability and agreement were determined using intra-class correlation coefficients (ICC), Bland-Altman plots and calculation of the standard error of measurement (SEM) and minimal detectable change (MDC). ResultsExcellent ICCs were found for both intra-processor and inter-processor analysis of lumbar multifidus volume measurement, with slightly better results for the intra-processor reliability. The SEMs for volume were lower than 4.1 cm³. Excellent reliability and agreement were also found for fat fraction measures, with ICCs of 0.985–0.998 and SEMs below 0.946%. ConclusionThe proposed method to quantify muscle volume and fat fraction of the lumbar multifidus on MRI was highly reliable, and can be used in further research on lumbar multifidus structure.

Can MRI chemical shift imaging replace thymic biopsy in myasthenia gravis patients?

BackgroundMyasthenia gravis is a neuromuscular junction autoimmune condition characterized by muscle weakness. Many people with myasthenia gravis have thymic abnormalities, such as thymic lymphoid hyperplasia and thymic tumors, therefore, the thymus plays a significant role in the disease. The imaging properties of thymic hyperplasia and thymoma on CT and conventional MRI are very similar, yet, MRI has recently revealed promising capability by adding novel sequences. Chemical shift MRI was demonstrated to consistently distinguish thymic hyperplasia from thymus gland tumors. The aim of this study was to determine the value of chemical shift MRI imaging in characterizing thymic lesions in patients diagnosed with myasthenia gravis and its ability to differentiate thymic hyperplasia from thymoma.ResultsMRI showed that thymic lymphoid hyperplasia was more common to be convex in shape while thymoma was more likely to be round or irregular (P = 0.004). Paired comparison between histopathology and chemical shift MRI showed that MRI had 90% sensitivity and 100% specificity in detecting thymoma with overall diagnostic accuracy 93.3% (P = 0.5). MRI chemical shift ratio showed 100% sensitivity by using > 0.85 as a cut off value for diagnosis of thymoma, with specificity 83.3% (P = 0.0001). There was statistically significant difference in chemical shift ratio between thymic lymphoid hyperplasia and thymoma groups, as thymoma group had a higher chemical shift ratio of 1.06 ± 0.06 compared to 0.48 ± 0.13 in thymic hyperplasia group (P = 0.0001).ConclusionMRI chemical shift imaging with chemical shift ratio offers a highly sensitive and specific tool in assessment of thymus lesions in myasthenia gravis patients and it can differentiate between thymic hyperplasia and thymoma using cutoff value of > 0.85, hence, unwarranted invasive procedures as thymic biopsy or thymectomy can be avoided and proper management could be planned.

Right adrenal vein identification using unenhanced magnetic resonance imaging.

Unenhanced magnetic resonance imaging (MRI) is known to be useful in characterizing adrenal adenomas through the implementation of in-phase (IPI) and opposed-phase imaging (OPI) based on chemical shift artifacts. However, whether unenhanced MRI can contribute to the identification of right adrenal vein (RAV) remains unclear. The aim of this study was to evaluate the feasibility of unenhanced MRI for the identification of RAV. This retrospective study reviewed 30 patients (16 men; median age 60 years; range 34-76 years) who underwent MRI and subsequent adrenal venous sampling (AVS). Chemical shift MRI was acquired using echo times of 2.3 ms (OPI) and 4.6 ms (IPI) with a slice thickness of 3 mm and a gap of 1 mm. T2-weighted imaging (T2WI) was also performed. Identification of RAVs was performed by 2 independent radiologists. Inter-observer agreement on a 3-point rating scale was evaluated using κ statistics. The identification rate of RAVs was compared between OPI, IPI, and T2WI using McNemar's test. Good inter-observer agreement was found for the OPI (κ = 0.744), whereas fair agreement was obtained for both other sequences (IPI: κ = 0.375; T2WI: 0.348). For both raters, the identification rate of RAVs was higher with OPI (36/60; 60.0%) than with other sequences (IPI: 16/60, 26.7%; T2WI: 9/60, 15.0%; p < 0.05, each). OPI may play a screening role in the identification of RAVs preceding AVS, which could reduce the required radiation exposure and doses of contrast agent.

Triglyceride Saturation in Patients at Risk of NASH and NAFLD: A Cross-Sectional Study

Chemical shift magnetic resonance imaging (MRI) is commonly used to estimate the amount of fat in tissues, namely the proton density fat fraction (PDFF). In addition to PDFF, the type of fat can be inferred and characterized in terms of the number of double bonds (NDB), number of methylene-interrupted double bonds (NMIDB) and the chain length (CL) of the fatty acid chains. The saturation index is potentially a marker for metabolic disorders. This study assesses the feasibility of estimating these parameters independently or in a constrained manner. Correlations with spectroscopy were measured in 109 subjects’ subcutaneous and visceral fat depots (p = 2 × 10−28), and with the NAFLD Activity Score (NAS) from histological evaluation of biopsies. The findings indicate that imaging estimates are comparable to spectroscopy (p = 0.0002), but there is no significant association of NDB with NAS (p = 0.1).

MRI assessment of epaxial myosteatosis in dogs with intervertebral disc extrusions and associations with patient factors and outcome.

Fat infiltration of skeletal muscle (myosteatosis) is a characteristic of reduced muscle quality. Objectives of this retrospective, observer agreement, methods comparison, cross-sectional study were to compare epaxial myosteatosis of dogs with surgically confirmed intervertebral disc extrusion (IVDE) using a visual semi-quantitative method and quantitative 2-point Dixon fat-water chemical-shift separation MRI method. Thoracolumbar MRI studies of 86 dogs were reviewed. Assessed locations were the site of extrusion and the adjacent intervertebral disc space immediately cranial. A visual fat score (VFS) was assigned to fat infiltration of the epaxial muscles. Quantitative assessment of fat infiltration was determined by calculating a muscle-fat fraction (MFF). There was moderate agreement between the two reviewers for VFS assessment (weighted Kappa 0.60, 95%CI 0.53-0.66) with moderate to strong correlation between scoring methods (P≤.001). Both VFS (P=.023, P=.02) and MFF (P=.041, P=.043) were significantly correlated with neurologic grade at presentation for the erector spinae muscle group at both sites. Higher VFS in the multifidus muscle increased the odds of a successful outcome when assessed at the extrusion site (odds ratio and 95%CI 4.3 (1.02-78.7), P=.0461). In summary, the visual and Dixon method of epaxial muscle-fat assessment are feasible in dogs with IVDE with moderate to strong correlation. Increased VFS of myosteatosis in the multifidus muscle at the extrusion site significantly increased the odds of a successful outcome. Further studies are indicated to assess the utility of myosteatosis as an MRI imaging biomarker in the preoperative imaging assessment of dogs with IVDE.