Facing successfully high mental workload and stressors: An fMRI study.

The present fMRI study aimed at highlighting patterns of brain activations and autonomic activity when confronted with high mental workload and the threat of auditory stressors. Twenty participants performed a complex cognitive task in either safe or aversive conditions. Our results showed that increased mental workload induced recruitment of the lateral frontoparietal executive control network (ECN), along with disengagement of medial prefrontal and posterior cingulate regions of the default mode network (DMN). Mental workload also elicited an increase in heart rate and pupil diameter. Task performance did not decrease under the threat of stressors, most likely due to efficient inhibition of auditory regions, as reflected by a large decrement of activity in the superior temporal gyri. The threat of stressors was also accompanied with deactivations of limbic regions of the salience network (SN), possibly reflecting emotional regulation mechanisms through control from dorsal medial prefrontal and parietal regions, as indicated by functional connectivity analyses. Meanwhile, the threat of stressors induced enhanced ECN activity, likely for improved attentional and cognitive processes toward the task, as suggested by increased lateral prefrontal and parietal activations. These fMRI results suggest that measuring the balance between ECN, SN, and DMN recruitment could be used for objective mental state assessment. In this sense, an extra recruitment of task-related regions and a high ratio of lateral versus medial prefrontal activity may represent a relevant marker of increased but efficient mental effort, while the opposite may indicate a disengagement from the task due to mental overload and/or stressors.

Tentative fMRI signatures of perceptual echoes in early visual cortex.

The visual Impulse Response Function (IRF) can be estimated by cross-correlating random luminance sequences with concurrently recorded EEG. It typically contains a strong 10 Hz oscillatory component, suggesting that visual information reverberates in the human brain as a "perceptual echo". The neural origin of these echoes remains unknown. To address this question, we recorded EEG and fMRI in two separate sessions. In both sessions, a disk whose luminance followed a random (white noise) sequence was presented in the upper left quadrant. Individual IRFs were derived from the EEG session. These IRFs were then used as "response templates" to reconstruct an estimate of the EEG during the fMRI session, by convolution with the corresponding random luminance sequences. The 7-14 Hz (alpha, the main frequency component of the IRF) envelope of the reconstructed EEG was finally used as an fMRI regressor, to determine which brain voxels co-varied with the oscillations elicited by the luminance sequence, i.e., the "perceptual echoes". The reconstructed envelope of EEG alpha was significantly correlated with BOLD responses in V1 and V2. Surprisingly, this correlation was visible outside, but not within the directly (retinotopically) stimulated region. We tentatively interpret this lack of alpha modulation as a BOLD saturation effect, since the overall stimulus-induced BOLD response was inversely related, across voxels, to the signal variability over time. In conclusion, our results suggest that perceptual echoes originate in early visual cortex, driven by widespread activity in V1 and V2, not retinotopically restricted, but possibly reflecting the propagation of a travelling alpha wave.

Quantitative assessment of tricuspid regurgitation using right and left ventricular stroke volumes obtained from tomographic equilibrium radionuclide ventriculography.

BACKGROUND: Quantitative assessment of valve regurgitation using volumetric method by comparing right and left ventricular stroke volumes is still under investigations. AIMS: To investigate the accuracy of tomographic equilibrium radionuclide ventriculography (t-ERV) for the quantification of tricuspid regurgitation (TR). METHODS AND RESULTS: Sixty-one patients (44 men; mean age 59 ± 12 years) who underwent both t-ERV and transthoracic echocardiography (TTE) studies within 2 weeks for right ventricular systolic function assessment were eligible for inclusion. A sub-group of 22 patients underwent both t-ERV and CMR. Patients with mitral/aortic regurgitation by TTE were excluded of the study. TR regurgitant volume (RVol) was calculated using the proximal isovelocity surface area (PISA) method from TTE and the volumetric method (right ventricular stroke volume minus left ventricular stroke volume) from t-ERV. There was a significant correlation between RVol as assess by ERV and by TTE (R = 0.95, P < 0.0001). Intraclass correlation coefficient between TTE and ERV for TR quantification was 0.95 (P < 0.0001). Among patients who underwent CMR, the correlation between RVol obtained by TTE and by t-ERV and CMR were R = 0.81 and R = 0.75, respectively (all P < 0.0001). CONCLUSION: TR assessment using the t-ERV correlates well with PISA from TTE in patients referred for right ventricular systolic function assessment.

Pattern of myocardial 99mTc-HMDP uptake and impact on myocardial function in patients with transthyretin cardiac amyloidosis.

AIMS: The purpose of the study was to describe the pattern of 99mTc-labeled phosphate agents myocardial uptake by scintigraphy and explore its impact on left ventricular (LV) functions in transthyretin cardiac amyloidosis (TTR-CA). METHODS: Fifty patients with TTR-CA underwent 99mTc- hydroxymethylene-diphosphonate (99mTc-HMDP) scintigraphy and echocardiography with measure of LV thickness, longitudinal strain (LS), systolic and diastolic functions. Cardiac retention by scintigraphy was assessed by visual scoring and the heart/whole body (H/WB) ratio was calculated by dividing counts in the heart by counts in late whole-body images. RESULTS: The mean population age was 79 ± 10 years. Mean H/WB ratio was 12 ± 7. Myocardial 99mTc-HMDP uptake on segments 5, 6, 7, 8, 11, 12, 13, 14, 16, and 17 was correlated with H/WB ratio. Mean LVEF and global LS were 51 ± 10% and - 10 ± 3%, respectively. H/WB ratio was correlated with global LS (R = 0.408, P = .003), Ea (R = - 0.566, P < .001) and mean left ventricular wall thickness (R = 0.476, P < .001) but not with LVEF (R = - 0.109, P = .453). Segmental myocardial uptake was slightly correlated with segmental LS (R = 0.152, P < .001). H/WB ratio was not correlated with NT-proBNP levels (R = 0.219, P = .148) neither E/Ea ratio (R = 0.204, P = .184). CONCLUSION: These findings show the relationship between bone tracer myocardial uptake and LV functions in patients with TTR cardiac amyloidosis.

What is the most useful imaging parameter to explore the prognostic value of the right ventricular function at the time of multimodality cardiovascular imaging?

BACKGROUND: Right ventricular (RV) function is a powerful independent predictor of adverse heart failure outcomes. The aim of this study was to compare the predictive value of main RV systolic imaging parameters for outcome. METHODS: Seventy-nine patients underwent comprehensive cardiovascular imaging modalities including transthoracic echocardiography, cardiac magnetic resonance (CMR) imaging, and tomographic equilibrium radionuclide ventriculography (ERV) for the assessment of RV function. The composite primary endpoint (CPE) was defined by the occurrence of death, heart transplantation, implantation of a left ventricular assist device, or new-onset acute heart failure. RESULTS: During a mean follow-up of 13 ± 9 months, 15 (19%) patients reached the CPE. The areas under the receiver operator characteristic curves for the prediction of the CPE were 0.922 (P < .001), 0.913 (P < .001), 0.906 (P < .001), 0.849 (P = .002), 0.837 (P = .003), 0.799 (P = .009), 0.792 (P = .011), 0.753 (P = .026), 0.720 (P = .053), and 0.608 (P = .346) for integral systolic S' wave tricuspid annular velocity, RV free wall longitudinal strain (RVFWLS), RV fractional area change, tricuspid annular plane systolic excursion, RV ejection fraction (RVEF) by CMR using the 4-chamber slices, peak systolic S' wave tricuspid annular velocity, RVEF by CMR using short-axis slices, RVEF by ERV, RV myocardial performance index, and RV myocardial acceleration during isovolumic contraction, respectively. CONCLUSION: Echocardiographic parameters, and particularly integral systolic S' wave tricuspid annular velocity and RVFWLS, have the best prognostic performance.

Prognostic impact of myocardial perfusion single photon emission computed tomography in patients with major extracardiac findings by computed tomography for attenuation correction.

BACKGROUND: Attenuation correction computed tomography (CT) contributes to an improvement in the diagnostic accuracy of myocardial perfusion imaging (MPI) by single photon emission tomography (SPECT). The aim of this study was to explore the prognosis of patients with major findings by CT according to the results of MPI. METHODS AND RESULTS: 1506 patients who underwent MPI by SPECT were retrospectively included. Attenuation correction CT images were systematically analyzed for major and minor abnormalities. 830 (55.1%) and 212 (14.1%) patients had minor and major extracardiac findings, respectively. Among patients with major extracardiac findings, the abnormality was previously unknown in 113 (53.3%) patients. 90 (41.9%) had abnormal MPI, 73 (34.4%) had a myocardial infarction scar, 55 (25.9%) had myocardial ischemia, and 38 (17.7%) patients had both myocardial infarction scar and myocardial ischemia. Among the 201 patients available for survival analysis, there were 67 (31.2%) deaths over a follow-up period of 3.2±1.3 years. There was no significant impact on survival arising from MPI, whatever the result. The results were the same among the 103 patients with previously unknown major extracardiac findings. CONCLUSION: Extracardiac findings by CT during MPI are frequent. Patients with major extracardiac findings have a poor mid-term outcome, whatever the results of the myocardial perfusion imaging. Extracardiac findings should be systematically checked when attenuation correction CT is performed.

Feasibility and accuracy of gated blood pool SPECT equilibrium radionuclide ventriculography for the assessment of left and right ventricular volumes and function in patients with left ventricular assist devices.

BACKGROUND: Left ventricular assist devices (LVADs) require serial assessment of right and left ventricular (RV & LV) volumes and function. Because the RV is not assisted, its function is a critical determinant of the hemodynamic and contributes significantly to postoperative morbidity and mortality. We evaluated the feasibility and the accuracy of tomographic-equilibrium radionuclide ventriculography (t-ERV) for the assessment of patients with LVADs. METHODS: Twenty-four patients with LVAD underwent t-ERV. Because of the limited acoustic window, transthoracic echocardiography (TTE) was only feasible in 19 patients. Functional evaluation including six-minute walk test (6MWT) and peak oxygen consumption (POC) was performed in 18 patients. Nine patients underwent a cardiac multidetector computed tomography (MDCT). Eight patients underwent a second evaluation by ERV 4.3 ± 1.4 months later. RESULTS: Reliability between t-ERV and MDCT for LV end-diastolic volume, LV end-systolic volume, LV ejection fraction, RV end-diastolic volume, RV end-systolic volume, and RV ejection fraction (RVEF) was 0.900 (P = .001), 0.911 (P = .001), 0.765 (P = .021), 0.728 (P = .042), 0.875 (P = .004), and 0.781 (P = .023), respectively. There was no correlation between t-ERV and RV systolic parameters assessed by TTE. RVEF was correlated with POC (R = 0.521; P = .027). A cut-off value of 40% for RVEF measured by t-ERV could discriminate patients with poor functional status (P = .048 for NYHA stage; P = .016 for 6MWT and P = .007 for POC). CONCLUSION: t-ERV is a simple, reproducible, and an accurate technique for the assessment of RV function in patients with LVADs and warrants consideration in the evaluation and monitoring of symptomatic patients.

Response Assessment in Neuro-Oncology criteria, contrast enhancement and perfusion MRI for assessing progression in glioblastoma.

PURPOSE: The purpose of the study was to evaluate Response Assessment in Neuro-Oncology (RANO) criteria in glioblastoma multiforme (GBM), with respect to the Macdonald criteria and changes in contrast-enhancement (CE) volume. Related variations in relative cerebral blood volume (rCBV) were investigated. METHODS: Forty-three patients diagnosed between 2006 and 2010 were included. All underwent surgical resection, followed by temozolomide-based chemoradiation. MR images were retrospectively reviewed. Times to progression (TTPs) according to RANO criteria, Macdonald criteria and increased CE volume (CE-3D) were compared, and the percentage change in the 75th percentile of rCBV (rCBV75) was evaluated. RESULTS: After a median follow-up of 22.7 months, a total of 39 patients had progressed according to RANO criteria, 32 according to CE-3D, and 42 according to Macdonald. Median TTPs were 6.4, 9.3, and 6.6 months, respectively. Overall agreement was 79.07% between RANO and CE-3D and 93.02% between RANO and Macdonald. The mean percentage change in rCBV75 at RANO progression onset was over 73% in 87.5% of patients. CONCLUSIONS: In conclusion, our findings suggest that CE-3D criterion is not yet suitable to assess progression in routine clinical practice. Indeed, the accurate threshold is still not well defined. To date, in our opinion, early detection of disease progression by RANO combined with advanced MRI imaging techniques like MRI perfusion and diffusion remains the best way to assess disease progression. Further investigations that would examine the impact of treatment modifications after progression determined by different criteria on overall survival would be of great value.

Multivoxel Object Representations in Adult Human Visual Cortex Are Flexible: An Associative Learning Study.

Learning associations between co-occurring events enables us to extract structure from our environment. Medial-temporal lobe structures are critical for associative learning. However, the role of the ventral visual pathway (VVP) in associative learning is not clear. Do multivoxel object representations in the VVP reflect newly formed associations? We show that VVP multivoxel representations become more similar to each other after human participants learn arbitrary new associations between pairs of unrelated objects (faces, houses, cars, chairs). Participants were scanned before and after 15 days of associative learning. To evaluate how object representations changed, a classifier was trained on discriminating two nonassociated categories (e.g., faces/houses) and tested on discriminating their paired associates (e.g., cars/chairs). Because the associations were arbitrary and counterbalanced across participants, there was initially no particular reason for this cross-classification decision to tend toward either alternative. Nonetheless, after learning, cross-classification performance increased in the VVP (but not hippocampus), on average by 3.3%, with some voxels showing increases of up to 10%. For example, a chair multivoxel representation that initially resembled neither face nor house representations was, after learning, classified as more similar to that of faces for participants who associated chairs with faces and to that of houses for participants who associated chairs with houses. Additionally, learning produced long-lasting perceptual consequences. In a behavioral priming experiment performed several months later, the change in cross-classification performance was correlated with the degree of priming. Thus, VVP multivoxel representations are not static but become more similar to each other after associative learning.

Ultra-small superparamagnetic iron oxide enhancement is associated with higher loss of brain tissue structure in clinically isolated syndrome.

BACKGROUND: Macrophages are important components of inflammatory processes in multiple sclerosis, closely linked to axonal loss, and can now be observed in vivo using ultra-small superparamagnetic iron oxide (USPIO). In the present 1-year longitudinal study, we aimed to determine the prevalence and the impact on tissue injury of macrophage infiltration in patients after the first clinical event of multiple sclerosis. METHODS: Thirty-five patients, 32 years mean age, were imaged in a mean of 66 days after their first event using conventional magnetic resonance imaging, gadolinium (Gd) to probe blood-brain barrier integrity, USPIO to study macrophage infiltration and magnetization transfer ratio (MTR) to assess tissue structure integrity. Statistics were performed using two-group repeated-measures ANOVA. Any patient received treatment at baseline. RESULTS: At baseline, patients showed 17 USPIO-positive lesions reflecting infiltration of macrophages present from the onset. This infiltration was associated with local higher loss of tissue structure as emphasized by significant lower MTRnorm values (p<0.03) in USPIO(+)/Gd(+) lesions (n=16; MTRnormUSPIO(+)/Gd(+)=0.78 at baseline, MTRnormUSPIO(+)/Gd(+)=0.81 at M12) relative to USPIO(-)/Gd(+) lesions (n=67; MTRnormUSPIO(-)/Gd(+)=0.82 at baseline, MTRnormUSPIO(-)/Gd(+)=0.85 at M12). No interaction in MTR values was observed during the 12 months follow-up (lesion type × time). CONCLUSION: Infiltration of activated macrophages evidenced by USPIO enhancement, is present at the onset of multiple sclerosis and is associated with higher and persistent local loss of tissue structure. Macrophage infiltration affects more tissue structure while tissue recovery during the following year has a similar pattern for USPIO and Gd-enhanced lesions, leading to relative higher persistent local loss of tissue structure in lesions showing USPIO enhancement at baseline.

Do perfusion and diffusion MRI predict glioblastoma relapse sites following chemoradiation?

To assess the value of T2* dynamic-susceptibility contrast MRI (DSC-MRI) and diffusion-weighted imaging (DWI) to predict the glioblastoma relapse sites after chemoradiation. From a cohort of 44 patients, primarily treated with radiotherapy (60 Gy) and concomitant temozolomide for glioblastoma, who were included in the reference arm of a prospective clinical trial (NCT01507506), 15 patients relapsed and their imaging data were analyzed. All patients underwent anatomical MRI, DSC-MRI and DWI before radiotherapy and every 2 months thereafter until relapse. Voxels within the sites of relapse were correlated with their perfusion and/or diffusion abnormality (PDA) pretreatment status after rigid co-registration. The relative cerebral blood volume (rCBV) and apparent diffusion coefficient (ADC) were used as biomarkers. Several PDA areas were thresholded: hyperperfused voxels using a 1.75 fixed rCBV threshold (HPt); hypoperfused (hPg) and hyperperfused (HPg) voxels using a histogram-based Gaussian method; diffusion-restricted voxels (DRg); and HPg voxels with diffusion restriction (HPg&DRg). Two sets of voxels (2,459,483 and 2,073,880) were analyzed according to these thresholding methods. Positive predictive values (PPV) of PDA voxels were low (between 9.5 and 31.9 %). The best PPV was obtained with HPg&DRg voxels within the FLAIR hyperintensity, as 18.3 % of voxels without initial PDA were within relapse sites, versus 31.9 % with initial PDA (p < 0.0001). This prospective study suggests that DSC and/or DWI-MRI do not predict the glioblastoma relapse sites. However, further investigations with new methodological approaches are needed to better understand the role of these modalities in the prediction of glioblastoma relapse sites.

Voxel-based evidence of perfusion normalization in glioblastoma patients included in a phase I-II trial of radiotherapy/tipifarnib combination.

We previously showed that the farnesyl transferase inihibitor, Tipifarnib induced vascularization normalization, oxygenation and radiosensitization in a pre-clinical glioblastoma (GBM) model. The aim of this study was to assess by dynamic-susceptibility-contrast MRI (DSC-MRI) the effect of radiotherapy (RT) and Tipifarnib combination on tumor perfusion in GBM patients. Eighteen patients with newly diagnosed GBM, enrolled in a phase I-II clinical trial associating RT with Tipifarnib, underwent anatomical MR imaging and DSC-MRI before (M0) and two months after treatment (M2). Anatomic volumes of interest (VOIs) were delineated according to contrast-enhanced and hyper-intense signal areas on T1-Gd and T2 images, respectively. Perfusion variations between M0 and M2 were assessed with median relative cerebral blood volume (rCBV) inside these VOIs. Another voxel by voxel analysis of CBV values classified 405,117 tumor voxels into High_, Normal_ and Low_CBVTUMOR according to the distribution of CBV in the contralateral normal tissue. These three categories of CBVTUMOR voxels were color-coded over anatomical MRI. Variations of median rCBV were significantly different for two groups of patients (P < 0.013): rCBV decreased when initial rCBV was ≥ 1.0 (Group_rCBV_M0 > 1) and rCBV increased when initial rCBV was < 1.0 (Group_rCBV_M0 < 1). Mapping of color-coded voxels provided additional spatial and quantitative information about tumor perfusion: Group_rCBV_M0 > 1 presented a significant decrease of High_CBVTUMOR volume (P = 0.015) simultaneously with a significant increase of Normal_CBVTUMOR volume (P = 0.009) after treatment. Group_rCBV_M0 < 1 presented a decrease of Low_CBVTUMOR volume with an increase of Normal_ and High_CBV TUMOR volume after treatment. Pre and post-treatment CBV measurements with DSC-MRI characterized tumor perfusion evolution in GBM patients treated with RT combined to Tipifarnib; showing variations in favour of tumor perfusion normalization in agreement with our pre-clinical results of vascular normalization.

Gated blood pool SPECT: The estimation of right ventricular volume and function is algorithm dependent in a clinical setting.

BACKGROUND: Gated blood pool SPECT (GBPS) requires further validation for the assessment of the right ventricle (RV). This study evaluated three algorithms: BP-SPECT, QBS, and TOMPOOL (results are referred using this order). We compared (1) their "quantitative-accuracy": estimation of RV ejection fraction (EF), end-diastolic volume (EDV), and cardiac output (CO); (2) their "qualitative-accuracy": threshold values allowing diagnosing an impairment of the RV function; (3) their reproducibility: inter-observer relative variability (IOV). METHODS AND RESULTS: Forty-eight consecutive patients underwent GBPS. Recommended reference standards were used: cardiac magnetic resonance imaging (CMR) (EDV, EF, n = 48), catheter measurements from thermodilution (TD) (CO, n = 25). (1) "Quantitative-accuracy": r = 0.42, 0.30, 0.42 for RVEF (CMR); r = 0.69, 0.77, 0.53 for RVEDV (CMR); 0.32, 0.36, 0.52 for RCO (TD). (2) "Qualitative-accuracy": optimal thresholds were 54.7%, 38.5%, 45.2% (AUC: 0.83, 0.80, 0.79) for RVEF; 229, 180, 94 mL (AUC: 0.83, 0.81, 0.81) for RVEDV; 4.1, 4.4, 2.6 L·minute(-1) (AUC: 0.73, 0.77, 0.80) for RCO. (3) Reproducibility: IOV was 5% ± 6%, 8% ± 12%, 17% ± 18% for RVEF; 6% ± 8%, 4% ± 4%, 21% ± 18% for RVEDV; 8% ± 8%, 11% ± 15%, 24% ± 20% for RCO. CONCLUSION: Diagnostic accuracies are similar. A CMR-based calibration is required for a quantitative-analysis (cautious interpretation) or an accurate qualitative analysis (thresholds must be adjusted). Automatic procedures (BP-SPECT, QBS) offer the best compromise accuracy/reproducibility.

Is TOMPOOL (gated blood-pool SPECT processing software) accurate to diagnose right and left ventricular dysfunction in a clinical setting?

BACKGROUND: The assessment of right ventricular function is crucial for management of heart disease. TOMPOOL is a software that processes data acquired with Tomographic Equilibrium Radionuclide Ventriculography. In this report, TOMPOOL's diagnostic accuracy and inter-observer reproducibility were assessed in a cohort of patients with various etiologies of ventricular dysfunction. METHODS AND RESULTS: End-diastolic volume (EDV), ejection fraction (EF), and cardiac output (CO) were calculated for the right ventricle (RV) and the left ventricle (LV) using TOMPOOL in 99 consecutive patients. Thirty-five patients underwent cardiac magnetic resonance imaging (CMR) considered as the reference-standard to measure EDV and EF; the Spearman's rho correlation coefficients were r = 0.73/0.80 and 0.67/0.73 for right/left EF and EDV, respectively. Twenty-one patients had thermodilution measurements of right CO (reference-standard), the correlation was r = 0.57. The best cut-off points (sensitivity/specificity) in order to diagnose a ventricular dysfunction or enlargement were 46% for RVEF (67%/89%), 62% for LVEF (100%/90%), 94 mL for RVEDV (77%/73%), and 84 mL for LVEDV (100%/91%). The areas under the ROC curve were, respectively, 0.79, 0.91, 0.83, and 0.99. Inter-observer reproducibility was r = 0.81/0.94, 0.77/0.90, and 0.78/0.75 for Right/Left EF, EDV, and CO, respectively. CONCLUSION: TOMPOOL is accurate: measurements of EDV, EF, and CO are reproducible and correlate with CMR and thermodilution. However, thresholds must be adjusted.

Prediction of all-cause mortality from gated-SPECT global myocardial wall thickening: comparison with ejection fraction and global longitudinal 2D-strain.

BACKGROUND: The aim of this study was to assess the correlation between global wall thickening (GWT) obtained by gated-single photon emission computed tomography (SPECT) and echocardiographic measures [ejection fraction (EF), global longitudinal strain (GLS), and strain rate (GLSR)] and to compare their prognostic value for all-cause mortality. METHODS AND RESULTS: Seventy-four patients with referral for dipyridamole myocardial perfusion SPECT were prospectively included and underwent transthoracic echocardiography to measure left ventricular EF, GLS, and GLSR. The strongest correlation with GWT was for EF (R = 0.63, P < .001), followed by GLSR (R = -0.57, P < .001) and GLS (R = -0.53, P < .001). There were ten deaths over a period of 14.6 ± 5.7 months. Using the multivariate Cox analysis, summed stress score (HR 1.108; P = .023), EF (HR 1.01, P = .031), GLS (HR 1.593, P = .001), and GWT (HR 0.898, P = .034) remained independent predictors of mortality. Mean survival rate evaluated by Kaplan-Meier analysis was longer in patients with GWT ≥ 24% (21.9 ± 0.6 months) than those with GWT < 24% (13.6 ± 2.7 months; P < .001). CONCLUSIONS: GWT assessed is a highly sensitive tool to detect early myocardial systolic dysfunction and may bring additional prognostic information.

New concept of myocardial longitudinal strain reserve assessed by a dipyridamole infusion using 2D-strain echocardiography: the impact of diabetes and age, and the prognostic value.

AIMS: Although dipyridamole is a widely used pharmacological stress agent, the direct effects on myocardium are not entirely known. Diabetic cardiomyopathy can be investigated by 2D-strain echocardiography. The aim of this study was to assess myocardial functional reserve after dipyridamole infusion using speckle-tracking echocardiography. METHODS: Seventy-five patients referred for dipyridamole stress myocardial perfusion gated SPECT (MPGS) were examined by echocardiography to assess a new concept of longitudinal strain reserve (LSR) and longitudinal strain rate reserve (LSRR) respectively defined by the differences of global longitudinal strain (GLS) and longitudinal strain rate between peak stress after dipyridamole and rest. Twelve patients with myocardial ischemia were excluded on the basis of MPGS as gold standard. RESULTS: Mean LSR was -2.28±2.19% and was more important in the 28 (44%) diabetic patients (-3.27±1.93%; p=0.001). After multivariate analyses, only diabetes improved LSR (p=0.011) after dipyridamole infusion and was not associated with glycaemic control (p=0.21), insulin therapy (p=0.46) or duration of the disease (p=0.80). Conversely, age (p=0.002) remained associated with a decrease in LSR. LSSR was also correlated to age (p=0.005). Patients with a LSR<0% have a better survival after 15 months (log-rank p=0.0012). CONCLUSION: LSR explored by 2D speckle-tracking echocardiography after dipyridamole infusion is a simple and new concept that provides new insights into the impact of diabetes and age on the myocardium with a potential prognostic value.

Adaptation of stimulation duration to enhance auditory response in fNIRS block design.

Functional near-infrared spectroscopy (fNIRS) is an increasingly popular method in hearing research. However, few studies have considered efficient stimulation parameters for the auditory experimental design of fNIRS. The objectives of our study are (1) to identify the most effective paradigm for the stimulation blocks with increasing duration (8s, 10s, 15s, 20s) in terms of response amplitude, i.e., the most-efficient stimulation duration; (2) to assess the linearity/nonlinearity of the hemodynamic responses with respect to increasing block durations; and (3) to generalize results to more ecological environmental stimuli. We found that cortical activity is augmented following the increments in stimulation durations and reaches a plateau after about 15s of stimulation. The linearity analysis showed that this augmentation due to stimulation duration is not linear in the auditory cortex, non-linearity being more pronounced for shorter durations (15s and 20s). The 15s block duration that we propose as the most suitable precludes signal saturation and is associated with a high response amplitude and a relatively short total experimental duration. Moreover, the distribution of stimuli among the 15s blocks, which is the most effective for white noise stimulation, also provides a comparably strong response for environmental sounds. The sum of these findings suggests that 15s stimulation duration used in the appropriate experimental setup allows researchers to acquire optimal fNIRS signal quality.

Quantitative and reproducibility study of four tractography algorithms used in clinical routine.

PURPOSE: To evaluate fiber tracking strategy in terms of acquisition schemes in conjunction with four algorithms used in clinical routine, we studied one of the major tracts, anatomically well known, and which should be preserved as much as possible during neurosurgery: the corticospinal tract. MATERIALS AND METHODS: Two identical exams, composed of three DTI acquisition schemes (6, 15, and 32 gradient directions), were performed on 12 healthy subjects during two different sessions. For each subject, intra-operator, and inter-exam reproducibility was quantitatively calculated from different fiber tracking algorithms: three deterministic and a probabilistic one. Inter-exam reproducibility was evaluated comparing fiber tracking results from the repetition of the same acquisition one month apart and variation of the fiber density distribution percentile. RESULTS: For each fiber tracking algorithm, the best reproducibility result is obtained in case of 50% of fiber density and for the number of directions equal to 32. The reproducibility is improved using the probabilistic algorithm. CONCLUSION: This study highlights increased reliability of reproducibility results based on the number of directions used during the acquisition. The method of tractography used and the choice of adequate density fiber tract greatly improve the results.

Evaluation of a trainer phantom in the learning phase of sentinel lymph node identification in breast cancer.

BACKGROUND: The concept of a learning phase is difficult to implement in a university setting, as it is unacceptable to subject a patient who requires only lymphadenectomy to axillary dissection for the purpose of training surgeons. We therefore sought to evaluate intraoperative sentinel node detection using a phantom, the Senti-Trainer. Learning phases on the Senti-Trainer and detection rate were assessed in order to determine whether the proficiency of surgeons in training improved with the number of procedures. METHODS: Twenty residents each performed 30 detection procedures of a sentinel node on the silicon phantom. Each resident was evaluated at each procedure, and an observation report was made every five procedures. Evaluation was single-blind as the surgeons did not know the result of the previous detection and were aware of the results only after the thirtieth procedure. RESULTS: The mean detection rate was 75% during the first procedure and reached 95% (or 5% detection errors) at the 30th procedure (p<0.0001; OR=6.33 with a 95% CI=[2.31; 17.33]). Proficiency in sentinel lymph node (SLN) identification also increased with the number of procedures performed. The ability to localize SLN improved during the learning phase with the increasing number of procedures performed. Mean detection time during the 30 procedures was 150 s (range: 115-210 s). CONCLUSIONS: Training on a phantom showed that this is a valuable teaching tool that enables surgeons to become familiar with gamma probes. It cannot replace the clinical training phase, but is an important aid to proficiency in intraoperative detection.

Impact of pulmonary perfusion defects by scintigraphy on pulmonary vascular resistances, functional capacity and right ventricular systolic function in patients with chronic thromboembolic pulmonary hypertension.

Chronic thromboembolic pulmonary hypertension (CTEPH) is a major cause of chronic pulmonary hypertension leading to right heart failure and death. Ventilation/perfusion single photon emission computed tomography (V/Q SPECT) is the screening test of choice showing mismatch in at least one segment or two sub-segments. Our aim was to investigate the relationship between the extent of pulmonary perfusion defects and hemodynamic, echocardiographic, biological and functional parameters. Between 2012 and 2019, 46 patients with CTEPH were retrospectively enrolled in the study. The diagnosis of pulmonary hypertension was made by the referral team of the expert center according to the European guidelines. All patients underwent pulmonary V/Q SPECT, right heart catheterization, transthoracic echocardiography (TTE), functional tests and natriuretic peptides assays. There was a slight correlation between the extent of pulmonary perfusion defects and pulmonary vascular resistances (R=0.510, P < 0.001). However, there was no correlation between the extent of pulmonary perfusion defects and NYHA stage, NT-proBNP level, functional parameters (6 minutes-walk distance-6 MWD), right ventricular function assessed by TTE. Pulmonary perfusion defects extension by V/Q lung SPECT are correlated with pulmonary vascular resistances in CTEPH. However, it is not correlated with right ventricular function and functional parameters.