Analysis of IVIM Perfusion Fraction Improves Detection of Pancreatic Ductal Adenocarcinoma.

The purpose of this study was to evaluate whether intravoxel incoherent motion (IVIM) parameters can enhance the diagnostic performance of MRI in differentiating normal pancreatic parenchyma from solid pancreatic adenocarcinomas. This study included 113 participants: 66 patients diagnosed with pancreatic adenocarcinoma and 47 healthy volunteers. An MRI was conducted at 1.5 T MR unit, using nine b-values. Postprocessing involved analyzing both conventional monoexponential apparent diffusion coefficient (ADC) and IVIM parameters (diffusion coefficient D-pure molecular diffusion coefficient, perfusion-dependent diffusion coefficient D*-pseudodiffusion coeffitient, and perfusion fraction coefficient (f)) across four different b-value selections. Significantly higher parameters were found in the control group when using high b-values for the pure diffusion analysis and all b-values for the monoexponential analysis. Conversely, in the study group, the parameters were affected by low b-values. Most parameters could differentiate between normal and cancerous tissue, with D* showing the highest diagnostic performance (AUC 98-100%). A marked decrease in perfusion in the patients with pancreatic cancer, indicated by the significant differences in the D* medians between groups, was found. In conclusion, standard ADC maps alone may not suffice for a definitive pancreatic cancer diagnosis, and incorporating IVIM into MRI protocols is recommended, as the reduced tissue perfusion detected by the IVIM parameters is a promising marker for pancreatic adenocarcinoma.

Unfavorable Changes of Platelet Reactivity on Clopidogrel Therapy Assessed by Impedance Aggregometry Affect a Larger Volume of Acute Ischemic Lesions in Stroke.

BACKGROUND: High on-treatment platelet reactivity or its equivalent-resistance to the antiplatelet agent-significantly reduces the efficacy of the therapy, contributing to a negative impact on stroke course. Previous studies demonstrated that aspirin resistance is associated with a larger size of acute ischemic infarct. Due to the increasing use of clopidogrel in the secondary prevention of stroke, we aimed to assess the impact of clopidogrel resistance on the size and extent of ischemic lesions, both acute and chronic. METHODS: This prospective, single-center and observational study involved 74 ischemic stroke subjects, treated with 75 mg of clopidogrel. We used impedance aggregometry to determine platelet reactivity 6-12 h after a dose of clopidogrel as a first assessment and 48 h later as the second measurement. A favorable dynamics of platelet reactivity over time was the decrease in the minimum value equal to the median in the entire study. The volume of acute ischemic infarct was estimated within 48 h after onset in diffusion-weighted imaging and fluid-attenuated inversion recovery sequences of magnetic resonance and the severity of chronic vascular lesions by Fazekas scale. RESULTS: Subjects with mild severity of chronic vascular lesions (Fazekas 1) exhibited a significant decrease of platelet reactivity over time (p = 0.035). Dynamics of platelet reactivity over time differed between subjects with large, moderate, mild and insignificant size of acute ischemic lesion (Kruskall-Wallis H = 3.2576; p = 0.048). In multivariate regression models, we reported unfavorable dynamics of platelet reactivity alone and combined with a high initial value of platelet reactivity as independent predictors of higher risk of a significant ischemic infarct volume (OR 7.16 95%CI 1.69-30.31, p = 0.008 and 26.49 95%CI 1.88-372.4, p = 0.015, respectively). CONCLUSIONS: We emphasized that unfavorable dynamics of platelet reactivity over time during clopidogrel therapy in acute phase of stroke affect the volume of acute infarct and the severity of chronic vascular lesions.

Cortical presentation of language functions in patients after total laryngectomy: a fMRI study.

PURPOSE: The aim of this study is to use functional magnetic resonance (fMRI) to analyse the cortical presentation of selected language functions in patients after a total laryngectomy. METHODS: Eighteen patients after total laryngectomy treated with electrolarynx speech and 18 volunteers were included. The mean number of patients' post-operative speech rehabilitation sessions was five (range of 3-8 sessions). Four paradigms were used, including noun generation, pseudoword reading, reading phrases with pseudowords, and nonliteral sign reproduction. RESULTS: In noun, the most significant difference between the groups was the stronger activation of both lingual gyri in the volunteers. Pseudoword reading resulted in stronger activations in patients than in volunteers in the lingual gyri, the right cerebellum, the right Broca's area, and the right parietal operculum. Reading phrases with pseudowords involved different parts of the Brodmann area 40. During nonliteral sign reproduction, there was a stronger activation of the left Broca's area in volunteers and a stronger activation of the left premotor cortex in patients. CONCLUSION: This study provides evidence of altered cortical activation in response to language tasks in patients after a laryngectomy compared with healthy volunteers, which may be considered brain plasticity in response to a laryngectomy.

Monoexponential and Biexponential Fitting of Diffusional Magnetic Resonance Imaging Signal Analysis for Prediction of Liver Fibrosis Severity.

OBJECTIVE: The objective of this study is to compare the value of monoexponential and biexponential approach to the diffusion-weighted magnetic resonance imaging signal in the prediction of the liver fibrosis. METHODS: Forty patients with hepatitis C were included. Quantification of the apparent diffusion coefficient (ADC) and pure molecular diffusion (D), pseudodiffusion (D*), and perfusion fraction (f) was performed using 9 b values (b = 0, 20, 50, 100, 200, 400, 600, 800, 1000 s/mm). RESULTS: Significant fibrosis was found in 14 subjects. Monoexponentally derived ADC parameters were significantly correlated. Apparent diffusion coefficient calculated from all b values and ADC based on high b values were significantly related to the fibrosis grade (P < 0.02), and none of intravoxel incoherent motion parameters presented such an association. Apparent diffusion coefficient based on high b values was the best predictor of significant fibrosis with area under the curve of 0.81, sensitivity of 0.57, and specificity of 0.92. CONCLUSION: Intravoxel incoherent motion parameters did not allow for prediction of the liver fibrosis. Apparent diffusion coefficient calculated based on high b values presents considerable specificity in predicting significant fibrosis.

Noninvasive evaluation of renal tissue oxygenation with blood oxygen level-dependent magnetic resonance imaging early after transplantation has a limited predictive value for the delayed graft function.

PURPOSE: The aim of this study was to evaluate the feasibility of renal oxygenation assessment using blood oxygen level-dependent (BOLD) magnetic resonance imaging (MRI) in the early period after kidney transplantation and to estimate its prognostic value for delayed graft function. MATERIAL AND METHODS: Examinations were performed in 50 subjects: 40 patients within a week after the kidney transplantation and 10 healthy controls, using T2*-weighted sequence. Measurements in transplant patients were correlated to basic laboratory parameters in the early period after transplantation and at follow-up. RESULTS: Examinations of seven patients (18%) were rejected due to their poor technical quality. Mean R2* values in transplant recipients were lower than in controls (11.6 vs. 15.9 Hz; p = 0.0001). An R2* value of 0.28 Hz was calculated as the minimal detectable change. There was no relation between R2* values and laboratory parameters. However, patients eGFR ≥ 40 ml/min/1.73 m2 presented higher R2* values than recipients eGFR < 40 ml/min/1.73 m2 (12.0 vs. 11.1 Hz; p = 0.0189). In ROC analysis R2* of ≤ 11.7 predicted an early reduced graft function with 0.82 sensitivity and 56% specificity (AUC = 0.708; p = 0.024) but was not useful for delayed graft function prediction (p > 0.7). CONCLUSIONS: Evaluation of renal graft oxygenation using BOLD MRI is technically challenging in the early period after transplantation. An R2* value of 0.28 Hz may in practice be considered as the minimal detectable change. The delayed graft function seems not to be dependent on early oxygenation values. Further, large-scale studies are necessary to confirm the latter observation.

Whole-organ and segmental stiffness measured with liver magnetic resonance elastography in healthy adults: significance of the region of interest.

PURPOSE: MR elastography (MRE) is a recent non-invasive technique that provides in vivo data on the viscoelasticity of the liver. Since the method is not well established, several different protocols were proposed that differ in results. The aim of the study was to analyze the variability of stiffness measurements in different regions of the liver. METHODS: Twenty healthy adults aged 24-45 years were recruited. The examination was performed using a mechanical excitation of 64 Hz. MRE images were fused with axial T2WI breath-hold images (thickness 10 mm, spacing 10 mm). Stiffness was measured as a mean value of each cross section of the whole liver, on a single largest cross section, in the right lobe, and in ROIs (50 pix.) placed in the center of the left lobe, segments 5/6, 7, 8, and the parahilar region. RESULTS: Whole-liver stiffness ranged from 1.56 to 2.75 kPa. Mean segmental stiffness differed significantly between the tested regions (range from 1.55 ± 0.28 to 2.37 ± 0.32 kPa; P < 0.0001, ANOVA). Within-method variability of measurements ranged from 14 % for whole liver and segment 8-26 % for segment 7. Within-subject variability ranged from 13 to 31 %. Results of measurement within segment 8 were closest to the whole-liver method (ICC, 0.84). CONCLUSIONS: Stiffness of the liver presented significant variability depending on the region of measurement. The most reproducible method is averaging of cross sections of the whole liver. There was significant variability between stiffness in subjects considered healthy, which requires further investigation.