Action Observation Responses Are Influenced by Movement Kinematics and Target Identity.

In order to inform the debate whether cortical areas related to action observation provide a pragmatic or a semantic representation of goal-directed actions, we performed 2 functional magnetic resonance imaging (fMRI) experiments in humans. The first experiment, involving observation of aimless arm movements, resulted in activation of most of the components known to support action execution and action observation. Given the absence of a target/goal in this experiment and the activation of parieto-premotor cortical areas, which were associated in the past with direction, amplitude, and velocity of movement of biological effectors, our findings suggest that during action observation we could be monitoring movement kinematics. With the second, double dissociation fMRI experiment, we revealed the components of the observation-related cortical network affected by 1) actions that have the same target/goal but different reaching and grasping kinematics and 2) actions that have very similar kinematics but different targets/goals. We found that certain areas related to action observation, including the mirror neuron ones, are informed about movement kinematics and/or target identity, hence providing a pragmatic rather than a semantic representation of goal-directed actions. Overall, our findings support a process-driven simulation-like mechanism of action understanding, in agreement with the theory of motor cognition, and question motor theories of action concept processing.

Dual-Energy Computed Tomography as an Adjunct in the Evaluation of Peripheral Chronic Total Occlusions: A Feasibility Study.

This study investigated the role of dual-energy computed tomography (CT) for lesion characterization in patients with peripheral arterial disease manifesting with chronic total occlusions (CTOs). Forty-one symptomatic patients with CTOs underwent dual-energy CT angiography before endovascular treatment. The lesions were subsequently analyzed in a dedicated workstation, and 2 indexes-dual-energy index (DEI) and effective Z (Zeff)-were calculated, ranging from 0.0027 to 0.321 and from 6.89 to 13.02, respectively. Statistical analysis showed a significant correlation between the DEI and Zeff values (P < .001). The interobserver intraclass correlation coefficient was 0.91 for the mean Zeff values and 0.86 for the mean DEI values. This technique could potentially provide useful information regarding the composition of a CTO.

Introduction of a new simple dynamic phantom for physical BOLD effect simulation.

OBJECTIVE: To propose a new method of simulating the BOLD contrast using a dynamic, easy to construct and operate, low-cost physical phantom. MATERIALS AND METHODS: A structure of thin pipelines passing through a gel volume was used to simulate blood vessels in human tissue. Quantitative T2*, R2* measurements were used to study the signal change of the phantom. BOLD fMRI experiments and analysis were performed to evaluate its potential use as an fMRI simulator. RESULTS: Experimental T2*, R2* measurements showed similar behavior with published references. BOLD contrast was successfully achieved with the proposed method. In addition, there were several proposed parameters, like the angle of the phantom relative to B0, which can easily adjust the signal change and the activation area. Coefficients of variation showed good reproducibility within a month period. Statistical t maps were produced with in-house software for the BOLD measurements. DISCUSSION: T2*maps and BOLD images confirm the potential use of this phantom as an fMRI simulator and also as a tool for studying sensitivity and specificity of BOLD sequences/algorithms.

Radiomics and machine learning to predict aggressive type 2 endoleaks after endovascular aneurysm repair: a proof of concept.

BACKGROUND: Persistent type 2 endoleaks (T2EL) require lifelong surveillance to avoid potentially life-threatening complications. PURPOSE: To evaluate the performance of radiomic features (RF) derived from computed tomography angiography (CTA), for differentiating aggressive from benign T2ELs after endovascular aneurysm repair (EVAR). MATERIAL AND METHODS: A prospective study was performed on patients who underwent EVAR from January 2018 to January 2020. Analysis was performed in patients who were diagnosed with T2EL based on the CTA of the first postoperative month and were followed at six months and one year. Patients were divided into two groups according to the change of aneurysm sac dimensions. Segmentation of T2ELs was performed and RF were extracted. Feature selection for subsequent machine-learning analysis was evaluated by means of artificial intelligence. Two support vector machines (SVM) classifiers were developed to predict the aneurysm sac dimension changes at one year, utilizing RF from T2EL at one- and six-month CTA scans, respectively. RESULTS: Among the 944 initial RF of T2EL, 58 and 51 robust RF from the one- and six-month CTA scans, respectively, were used for the machine-learning model development. The SVM classifier trained on one-month signatures was able to predict sac expansion at one year with an area under curve (AUC) of 89.3%, presenting 78.6% specificity and 100% sensitivity. Similarly, the SVM classifier developed with six-month radiomics data showed an AUC of 95.5%, specificity of 90.9%, and sensitivity of 100%. CONCLUSION: Machine-learning algorithms utilizing CTA-derived RF may predict aggressive T2ELs leading to aneurysm sac expansion after EVAR.

Extraocular Muscle Volumetry for Assessment of Thyroid Eye Disease.

BACKGROUND: In this study we evaluate the diagnostic accuracy of extraocular muscle volumetry in detecting thyroid eye disease and to compare the results with simple measurements of maximal medial rectus (MR) diameter. METHODS: Cross-sectional study that included 47 eyes of 47 patients with thyroid eye disease and 47 healthy controls. Patients underwent slitlamp examination and imaging consisting of computed tomography scans. Image segmentation and volume measurements were performed by 2 independent researchers. Intraobserver and interobserver reliability testing was also conducted. RESULTS: Total extraocular muscle volume was 7.31 ± 1.88 cm3 and medial volume was 2.38 ± 0.73 cm3 in the study group. In this group, the maximum measured diameter of the MR was 6.67 ± 0.35 mm. MR volume was statistically associated with maximum MR diameter (r = 9.78; P < 0.001). Both MR volume and maximum MR diameter measurements showed good predictive efficacy as shown using receiver operator characteristic curve analysis. CONCLUSIONS: Complications of thyroid eye disease are often sight threatening, and timely diagnosis is crucial for the management of the entity and its sequelae. The results of this study imply that simple measurements of maximum MR diameter are sensitive enough to establish diagnosis.

Occupational electromagnetic spectrum hazards and the significance of artificial optical radiation: country report for Greece.

BACKGROUND: The electromagnetic spectrum spans over an enormous range from 0 up to more than 1020 Hz in the deep ionizing region, significant exposures exist in specific occupational environments. Between the ionizing and the electromagnetic fields (EMF) part of the spectrum, the 'optical radiation' (OR) region has specific properties. Comparative and concise evaluation enables action prioritization. METHODS: Following the transposition and implementation periods of the artificial optical radiation (AOR) and EMF European Directives, the Hellenic Ministry of Labour in collaboration with the Greek Atomic Energy Commission (EEAE) and the National Technical University of Athens, conducted thorough occupational exposure investigation in Greece. Using dedicated measuring equipment and procedures, the majority of EMF emitting installations in Greece and also AOR emitting installations including arc welding, lasers and PC monitors has been assessed. RESULTS: Measurement results from occupational settings reveal that it is the non-coherent metal arc welding AOR that can pose even sub-second overexposures. Rare EMF overexposures are manageable and EMF concern is not justified. Maintenance procedures demand proper attention. Preliminary laser safety assessment reveals OHS gaps and potential eye and skin hazards. Blue light exposure from computer monitors is well below safety limits. CONCLUSIONS: This electromagnetic spectrum risk assessment conducted in Greece enables the justification of the real occupational hazards, in this sense: i) EMF exposure assessment has to be concentrated to maintenance procedures; ii) AOR measuring setups are challenging and standardized measurement procedures are missing, and iii) AOR overexposures from arc welding pose significant eye and skin hazards.

T2 Relaxometry Evidence of Microstructural Changes in Diffusely Abnormal White Matter in Relapsing-Remitting Multiple Sclerosis and Clinically Isolated Syndrome: Impact on Visuomotor Performance.

BACKGROUND: Although diffusely abnormal white matter (DAWM) is commonly seen in multiple sclerosis (MS), it is rarely considered in clinical/imaging studies. PURPOSE: To evaluate quantitative markers of microstructural changes in DAWM of patients with clinically isolated syndrome (CIS) and relapsing-remitting MS (RR-MS) in relation to MS lesions and degree of neurocognitive impairment, by using a multi-echo spin echo (MESE) Proton Density PD-to-T2 sequence. STUDY TYPE: Prospective, cross-sectional. POPULATION: Thirty-seven RR-MS patients, 33 CIS patients, and 52 healthy controls. FIELD STRENGTH/SEQUENCE: 1.5 T/T1-, T2-weighted, fluid-attenuated inversion recovery, and MESE sequences. ASSESSMENT: Long T2, short T2, and myelin water fraction (MWF) values were estimated as indices of intra/extracellular water content and myelin content, respectively, in DAWM, posterior periventricular normal appearing white matter (NAWM), and focal MS lesions, classified according to their signal intensity on T1 sequences. Patients were, also, administered a battery of neuropsychological tests. STATISTICAL TESTS: Comparisons of T2 and MWF values in DAWM, NAWM, and MS lesions were examined, using two-way mixed analyses of variance. Associations of Grooved Pegboard performance with T2 and MWF values in DAWM and NAWM were assessed using Pearson correlation coefficients. RESULTS: T2 and MWF values of DAWM were intermediate between the respective values of NAWM and T1 hypointense focal lesions, while there was no difference between the respective values of DAWM and T1-isointense lesions. T2 values in DAWM were strongly associated with visuomotor performance in CIS patients. DATA CONCLUSION: Intra/extracellular water and myelin water content of DAWM are similar to those of T1-isointense lesions and predict visuomotor performance in CIS patients. LEVEL OF EVIDENCE: 2 TECHNICAL EFFICACY: Stage 2.

Discrimination of High-Risk Type-2 Endoleak after Endovascular Aneurysm Repair through CT Perfusion: A Feasibility Study.

A type-2 endoleak after an endovascular aneurysm repair is the most prevalent type of endoleak, but as the clinical consequence of its diagnosis is uncertain, at present, management decisions are solely based on aneurysm sac growth. The aim of this study was to investigate the potential of various computed tomography perfusion parameters for their ability to distinguish high-risk type-2 endoleaks from low-risk type-2 endoleaks after an endovascular aneurysm repair.

Age-related deep white matter changes in myelin and water content: A T2 relaxometry study.

BACKGROUND: According to the retrogenesis hypothesis, the rate of age-related changes in white matter (WM) myelin content varies between early myelinating (parietal, occipital) and late myelinating (prefrontal, lateral-posterior temporal) areas. The multiecho spin echo (MESE), PD-to-T2 -weighted sequence provides an index of myelin content (myelin water fraction [MWF]) derived from measurements of myelin water (via the short T2 component [10-50 msec]) and intra- and extracellular water (via the long T2 component [>50-200 msec]). PURPOSE: To assess the shape and regional variations in the rate of age-related myelin and water content changes in deep WM regions using the MESE sequence. STUDY TYPE: Prospective, cross-sectional. POPULATION: In all, 90 healthy adults aged 22-81 years. FIELD STRENGTH/SEQUENCE: 1.5T/ T1 w, T2 w, fluid attenuated inversion recovery (FLAIR), MESE sequences. ASSESSMENT: Short T2 , long T2 , and MWF values were measured in prefrontal, parietal, lateral-posterior temporal, and occipital normal-appearing WM (NAWM) areas. STATISTICAL TESTS: Linear and quadratic effects of age on long T2 and MWF were assessed through regression analyses. Regional variations in the effect of age on long T2 and MWF values at both the individual and group level were examined, using regression and analysis of covariance (ANCOVA) analyses, respectively, controlling for total WM volume. RESULTS: The rate of age-related changes in long T2 and MWF was higher for older persons and a significant increase or decline, respectively, was first noted at 60-69 years (P < 0.0033). MWF values peaked earlier (at 30 years of age) and displayed a steeper age-related reduction in prefrontal and lateral-posterior temporal NAWM as compared with the occipital lobes (P < 0.05). The opposite pattern of age-related effect was found for long T2 values. DATA CONCLUSION: Significant age-related reductions in myelin content were closely followed by corresponding increases in intra- and extracellular water content. These changes were more pronounced among elderly people and followed an anterior-posterior pattern. LEVEL OF EVIDENCE: 2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2019;50:1393-1404.

Ex vivo orbital volumetry using stereology and CT imaging: A comparison with manual planimetry.

OBJECTIVES: To evaluate the applicability of stereology and planimetry in orbital volume measurements using computed tomography (CT) and to compare the results between the two measurements. METHODS: Experimental study using sheep craniums for CT imaging. Water filling measurements were performed, as the validation technique. Quantification techniques were also evaluated in five human subjects. To examine the proportion of agreement among measurements, we tested intra- and inter-observer agreement. RESULTS: For stereology customization, a 1/8 systematic sampling scheme was considered as optimal; this resulted in a low coefficient of error (2.59 %) and low measurement time (1.9 mins). In sheep craniums, mean volume measured by water displacement, planimetry and stereology was 17.81 ± 0.59 cm3, 17.87 ± 0.68 cm3 and 17.54 ± 0.49 cm3, respectively. Total volumes, obtained by stereology, were highly correlated with the water-filling method (r=0.893; p = 0.001) and a paired t-test showed significant difference between methods (t=3.047; p = 0.014). Planimetry results displayed a high correlation with the water-filling method (r=0.957; p ≈ 0.001) but no statistically significant difference was found (p = 0.154). Mean difference using planimetry and stereology was 0.332 ± 0.322 cm3. In human subjects, using stereology, the estimated volume ranged between 18.57 cm3 and 19.27 cm3, and the mean orbital volume was 19.05 ± 0.50 cm3 with CE=3.75 ± 0.16 %. Mean measure time was 2.1 ± 0.1 mins. CONCLUSIONS: Stereological measurements were superior to manual planimetry in terms of user effort and time spent. Stereology sampling of 1/8 was successfully applied in human subjects and yielded a strong correlation with manual planimetry. KEY POINTS: • Stereology can be applied to measure the orbital volume using computed tomography. • Stereological measurements display high correlation with gold standard planimetry and combine low coefficient of error (2.59%) with low measurement time (1.9 min). • Stereology is superior in terms of user effort and time spent.

CT Foot Perfusion Examination for Evaluation of Percutaneous Transluminal Angioplasty Outcome in Patients with Critical Limb Ischemia: A Feasibility Study.

PURPOSE: To evaluate foot perfusion in patients with critical limb ischemia (CLI) using quantitative perfusion multi-detector-row CT and estimate perfusion parameter changes before and after percutaneous transluminal angioplasty (PTA). MATERIALS AND METHODS: This prospective study investigated 13 patients (10 men; median age, 72 y; range, 51-84 y) with CLI who underwent CT foot perfusion examinations with a 128-slice dual-energy CT scanner 1 day before and 1 week after PTA. Key parameters such as permeability surface (PS), blood volume (BV), and blood flow (BF) were analyzed and compared statistically. The studies were also examined by a second observer to determine interobserver reproducibility. RESULTS: Revascularization was technically successful in all patients, and mean ankle-brachial index increased from 0.36 ± 0.16 to 0.75 ± 0.22. After revascularization, mean BV increased from 1.55 mL/100 g ± 0.83 to 4.51 mL/100 g ± 1.53, BF increased from 16.28 mL/100 g/min ± 4.97 to 31.49 mL/100 g/min ± 6.86, and PS increased from 3.1 mL/min/100 g ± 1.95 to 8.67 mL/min/100 g ± 3.85 (P < .05). Patients with poor response to revascularization who finally underwent amputation presented lower post-PTA perfusion parameters values than patients with significant clinical improvement (P < .05). All measurements demonstrated very good interobserver reproducibility, and intraclass correlation coefficients were 0.91 for BV, 0.94 for BF, and 0.95 for PS. The mean effective dose of the examination was estimated at 0.29 mSv. CONCLUSIONS: CT foot perfusion is a reproducible technique that may be a useful modality for the estimation of PTA outcome. Significant restitution of perfusion parameters was observed after successful revascularization.

Myelin content changes in probable Alzheimer's disease and mild cognitive impairment: Associations with age and severity of neuropsychiatric impairment.

BACKGROUND: Existing indices of white matter integrity such as fractional anisotropy and magnetization transfer ratio may not provide optimal specificity to myelin content. In contrast, myelin water fraction (MWF) derived from the multiecho T2 relaxation time technique may serve as a more direct measure of myelin content. PURPOSE/HYPOTHESIS: The goal of the present study was to identify markers of regional demyelination in patients with probable Alzheimer's disease (AD) and mild cognitive impairment (MCI) in relation to age and severity of neuropsychiatric impairment. POPULATION: The sample included patients diagnosed with probable AD (n = 25) or MCI (n = 43), and cognitively intact elderly controls (n = 33). FIELD STRENGTH/SEQUENCE ASSESSMENT: Long T2 , short T2 , and MWF values were measured with a 1.5T scanner in periventricular and deep normal-appearing white matter (NAWM), serving as indices of intra/extracellular water content and myelin content. A comprehensive neuropsychological and neuropsychiatric assessment was administered to all participants. STATISTICAL TESTS, RESULTS: AD patients displayed higher age-adjusted long and short T2 values and reduced MWF values in left temporal/parietal and bilateral periventricular NAWM than controls and MCI patients (P < 0.004; one-way analysis of covariance [ANCOVA] tests). Short T2 /MWF values in temporal, frontal, and periventricular NAWM of controls and/or MCI patients were significantly associated with episodic and semantic memory performance and depressive symptomatology (P < 0.004; partial correlation indices). The impact of age on memory performance was significantly (P < 0.01; mediated linear regression analyses) mediated by age-related changes in short T2 and MWF values in these regions. DATA CONCLUSION: Age-related demyelination is associated with memory impairment (especially in prodromal dementia states) and symptoms of depression in an anatomically specific manner. LEVEL OF EVIDENCE: 1 Technical Efficacy: Stage 3 J. Magn. Reson. Imaging 2018;47:1359-1372.

Normal Magnetic Resonance Imaging Anatomy of the Anterolateral Knee Ligament With a T2/T1-Weighted 3-Dimensional Sequence: A Feasibility Study.

PURPOSE: The anatomy of the lateral knee compartment has been recently further explored with description of the anterolateral knee ligament (ALL). The purpose of this study was to confirm the presence of ALL on cadaveric knees and to describe its normal anatomy in young healthy volunteers, utilizing a high-resolution 3-dimensional (3D) pulse sequence. METHODS: Dissection was performed on 9 cadaveric knees in order to confirm the presence of ALL. Conventional 2-dimensional sequences of 10 knees at 1.5 T and 10 knees at 3 T, with a slice thickness of 2-4 mm, were reviewed for the presence of ALL. A 3D T2/T1-weighted gradient echo sequence (constructive interference in steady state [CISS]), yielding in-plane resolution of 0.4 mm × 0.4 mm × 0.4 mm, was applied in 14 healthy volunteers (26 knees). All 3D images were manipulated using multiplanar reconstruction (MPR) and the presence and width of ALL were recorded. RESULTS: Cadaveric dissection disclosed the presence of ALL in 8 of 9 knees. Conventional knee MR imaging depicted ALL only on coronal images (18 of 20) whereas the CISS revealed ALL on 24 of 26 studied knees (92.3%). ALL has a mean thickness of 1.1 ± 0.27 mm measured on coronal MR images. CONCLUSIONS: ALL can be thoroughly assessed in young healthy individuals with the use of high-resolution 3D MR imaging with MPR at 1.5 T.

Novel Synthesis of Ultra-Small Dextran Coated Maghemite Nanoparticles for MRI and CT Contrast Agents via a Low Temperature Co-Precipitation Reaction.

Ultra-small dextran coated maghemite nanoparticles are synthesized via a low temperature modified co-precipitation method. A monoethylene glycol/water solution of 1:1 molar ratios and a fixed apparatus is used at a constant temperature of 5-10 degrees C. The growth of nanoparticles is prohibited due to low temperature synthesis and differs from usual thermal decomposition methods via Ostwald ripening. Strict temperature control and reaction timing of less than 20 minutes are essential to maintain narrow distribution in particle size. These nanoparticles are water-dispersible and biocompatible by capping with polyethylene glycol ligands. The aqueous suspensions are tested for cytotoxic activity on normal human skin fibroblasts. There is no reduction of the cells' viability at any concentration tested, the highest being 1% v/v of the suspension in culture medium, corresponding to the highest concentrations to be administered in vivo. Initial comparison with a T1 MRI contrast agent in sale shows that maghemite nanoparticles exhibit high r1 and r2 relaxivities in MRI tomography and strong contrast in computed tomography, demonstrating that these nanoparticles can be efficient T1, T2 and CT contrast agents.

Utility of Dual-Energy Computed Tomography in lesion characterization and treatment planning for peripheral Chronic Total Occlusions: A comprehensive analysis of crossing difficulty.

PURPOSE: To investigate whether Dual-Energy Computed Tomography (DECT) could be useful in the lesion characterization and endovascular treatment planning of symptomatic patients with peripheral arterial disease (PAD) due to Chronic Total Occlusions (CTO). MATERIALS AND METHODS: Between 2018 and 2022, 60 symptomatic patients (52 male, age 71 years) with peripheral arterial CTO underwent DECT angiography before percutaneous endovascular treatment. Patients were classified, according to guidewire crossing difficulty into four categories, which were subsequently correlated with DECT values, including Dual Energy Index (DEI) and Effective Z (Zeff). DECT values were also corelated with crossing time. The crossing difficulty was further correlated with the Trans-Atlantic Inter-Society Consensus Document (TASC II) classification. RESULTS: Technical success, defined as perceived antegrade true lumen or subintimal crossing, was achieved in 76.7 %. Among the cases, 20 were deemed easy, 14 moderate, 12 hard and 14 were failed attempts. Statistical analysis revealed a significant correlation between DEI, Zeff values, and the crossing difficulty categories (p < 0.001). Additionally, there was also a correlation between crossing time and DECT values. However, no significant correlation was recorded between difficulty categories and TASC II classification. CONCLUSION: Pre-procedural DECT angiography provides valuable information for patient selection and planning of the revascularization strategy. Moreover, it is helpful in the selection of the appropriate PTA materials, based on the lesion characteristics. Further research should be invested in this important field, to determine the optimal treatment approach in patients suffering from PAD due to CTOs.

Chronic Mild Traumatic Brain Injury: Aberrant Static and Dynamic Connectomic Features Identified Through Machine Learning Model Fusion.

Traumatic Brain Injury (TBI) is a frequently occurring condition and approximately 90% of TBI cases are classified as mild (mTBI). However, conventional MRI has limited diagnostic and prognostic value, thus warranting the utilization of additional imaging modalities and analysis procedures. The functional connectomic approach using resting-state functional MRI (rs-fMRI) has shown great potential and promising diagnostic capabilities across multiple clinical scenarios, including mTBI. Additionally, there is increasing recognition of a fundamental role of brain dynamics in healthy and pathological cognition. Here, we undertake an in-depth investigation of mTBI-related connectomic disturbances and their emotional and cognitive correlates. We leveraged machine learning and graph theory to combine static and dynamic functional connectivity (FC) with regional entropy values, achieving classification accuracy up to 75% (77, 74 and 76% precision, sensitivity and specificity, respectively). As compared to healthy controls, the mTBI group displayed hypoconnectivity in the temporal poles, which correlated positively with semantic (r = 0.43, p < 0.008) and phonemic verbal fluency (r = 0.46, p < 0.004), while hypoconnectivity in the right dorsal posterior cingulate correlated positively with depression symptom severity (r = 0.54, p < 0.0006). These results highlight the importance of residual FC in these regions for preserved cognitive and emotional function in mTBI. Conversely, hyperconnectivity was observed in the right precentral and supramarginal gyri, which correlated negatively with semantic verbal fluency (r=-0.47, p < 0.003), indicating a potential ineffective compensatory mechanism. These novel results are promising toward understanding the pathophysiology of mTBI and explaining some of its most lingering emotional and cognitive symptoms.

White matter and deep gray matter hemodynamic changes in multiple sclerosis patients with clinically isolated syndrome.

The dynamic susceptibility contrast magnetic resonance imaging perfusion technique was used to investigate possible hemodynamic changes in normal appearing white matter and deep gray matter (DGM) of 30 patients with clinically isolated syndrome (CIS) and 30 patients with relapsing-remitting multiple sclerosis. Thirty normal volunteers were studied as controls. Cerebral blood volume, cerebral blood flow (CBF), and mean transit time values were estimated. Normalization was achieved for each subject with respect to average values of CBF and mean transit time of the hippocampi's dentate gyrus. Measurements concerned three regions of normal white matter of normal volunteers, normal appearing white matter of CIS and patients with relapsing-remitting multiple sclerosis, and DGM regions, bilaterally. All measured normal appearing white matter and DGM regions of the patients with CIS had significantly higher cerebral blood volume and mean transit time values, while averaged DGM regions had significantly lower CBF values, compared to those of normal volunteers (P < 0.001). Regarding patients with relapsing-remitting multiple sclerosis, all measured normal appearing white matter and DGM regions showed lower CBF values than those of normal volunteers and lower cerebral blood volume and CBF values compared to patients with CIS (P < 0.001). These data provide strong evidence that hemodynamic changes--affecting both white and DGM--may occur even at the earliest stage of multiple sclerosis, with CIS patients being significantly different than relapsing-remitting multiple sclerosis patients.

Perfusion parameters analysis of the vertebral bone marrow in patients with Ph¹â» chronic myeloproliferative neoplasms (Ph(neg) MPN): a dynamic contrast-enhanced MRI (DCE-MRI) study.

PURPOSE: To evaluate perfusion parameters of the vertebral bone marrow in patients with Philadelphia negative chronic myeloproliferative neoplasms (Ph(neg) MPN) using dynamic contrast-enhanced MRI (DCE-MRI). MATERIALS AND METHODS: The study enrolled 24 patients with Ph(neg) MPN: 12 patients with myelofibrosis (Group A), 6 with essential thrombocythemia (ET), and 6 with polycythemia vera (PV) (Group B) who underwent DCE-MRI of the lumbosacral spine. Twelve normal individuals served as control group (Group C). Wash-in (WIN), wash-out (WOUT), maximum contrast-enhancement (CE max), time-to-peak (TTPK), time-to-maximum slope (TMSP), and the WIN/TMSP ratio (WTSP) were calculated. RESULTS: WIN, CE(max) , and WTSP parameters were higher in Group A than in Group C (P < 0.05). These parameters were significant (P < 0.0001) in discriminating patients with myelofibrosis from normal individuals with sensitivities 74.14%, 87.93%, 74.14%, and specificities 91.07%, 83.93%, 91.07%, respectively. WIN, WOUT, CE(max) , and WTSP parameters were higher in Group A than in Group B (P < 0.05). Group B exhibited no differences in perfusion parameters as compared with Group C with the exception of WOUT. CONCLUSION: Patients with myelofibrosis exhibited increased perfusion parameters in vertebral bone marrow, which could be consisted with increased vascularity, probably related to neoangiogenesis as opposed to ET or PV patients showing no increased perfusion. DCE-MRI may be of value in discriminating subgroups of Ph(neg) MPN patients and in indicating those progressing to myelofibrosis.

Perfusion imaging techniques in lower extremity peripheral arterial disease.

Lower limb peripheral arterial disease (PAD) characterizes the impairment of blood flow to extremities caused by arterial stenoses or occlusions. Evaluation of PAD is based on clinical examination, calculation of ankle-brachial index and imaging studies such as ultrasound, CT, MRI and digital subtraction angiography. These modalities provide significant information about location, extension and severity of macrovasular lesions in lower extremity arterial system. However, they can be also used to evaluate limb perfusion, using appropriate techniques and protocols. This information may be valuable for assessment of the severity of ischemia and detection of hypoperfused areas. Moreover, they can be used for planning of revascularization strategy in patients with severe PAD and evaluation of therapeutic outcome. These techniques may also determine prognosis and amputation risk in patients with PAD. This review gives a basic overview of the perfusion techniques for lower limbs provided by imaging modalities such as ultrasound, CT, MRI, digital subtraction angiography and scintigraphy and their clinical applications for evaluation of PAD and revascularization outcome.

Microvasculopathy-Related Hemorrhagic Tissue Deposition of Iron May Contribute to Fibrosis in Systemic Sclerosis: Hypothesis-Generating Insights from the Literature and Preliminary Findings.

Microvascular wall abnormalities demonstrated by nailfold capillaroscopy in systemic sclerosis (SSc) may result in microhemorrhagic deposition of erythrocyte-derived iron. Such abnormalities precede fibrosis, which is orchestrated by myofibroblasts. Iron induces endothelial-to-mesenchymal transition in vitro, which is reversed by reactive oxygen species (ROS) scavengers. The conversion of quiescent fibroblasts into profibrotic myofibroblasts has also been associated with ROS-mediated activation of TGF-ß1. Given that iron overload predisposes to ROS formation, we hypothesized that the uptake of erythrocyte-derived iron by resident cells promotes fibrosis. Firstly, we show that iron induces oxidative stress in skin-derived and synovial fibroblasts in vitro, as well as in blood mononuclear cells ex vivo. The biological relevance of increased oxidative stress was confirmed by showing the concomitant induction of DNA damage in these cell types. Similar results were obtained in vivo, following intravenous iron administration. Secondly, using magnetic resonance imaging we show an increased iron deposition in the fingers of a patient with early SSc and nailfold microhemorrhages. While a systematic magnetic resonance study to examine tissue iron levels in SSc, including internal organs, is underway, herein we propose that iron may be a pathogenetic link between microvasculopathy and fibrosis and an additional mechanism responsible for increased oxidative stress in SSc.