[Cardiac magnetic resonance stress perfusion: a single-center study]. / Ressonância magnética cardíaca de perfusão em stress: a experiência de um centro nacional.

INTRODUCTION AND OBJECTIVES: Myocardial ischemia can be assessed with cardiac magnetic resonance perfusion imaging (MRPI). This study aimed to analyze the clinical utility of MRPI in the diagnosis of significant coronary artery disease. METHODS: Fifty-five patients were examined with a 1.5 T MR scanner (Siemens Symphony), with a first pass of 0.10 mmol/kg gadolinium chelate, at rest and during adenosine vasodilatation (140µg/kg/min for 4min) using an inversion recovery steady-state free precession sequence. The results were compared with coronary angiography and with SPECT myocardial perfusion images. Agreement for qualitative diagnosis was measured by the kappa coefficient, taking statistical significance as 95%. Minimum clinical follow-up was 12 months. RESULTS: In 19 patients (34.5%) MRPI was negative for myocardial ischemia and necrosis, in 17 (30.9%) it was negative for ischemia but positive for necrosis, in 7 (12.7%) only ischemia was present and in 12 (21.8%) the ischemic area was larger than the necrotic area. The correlation between MRPI and coronary angiography for ischemia detection by coronary artery territory was very good: left anterior descending and right coronary - k=0.8571 (0.59-1), circumflex - k=0.8108 (0.59-1). By contrast, there was no correlation in terms of myocardial ischemia detection between MRPI and SPECT. CONCLUSIONS: MRPI is able to diagnose significant coronary disease in a high risk population, by detection of myocardial ischemia.

ICA decomposition of EEG signal for fMRI processing in epilepsy.

In this study, we introduce a new approach to process simultaneous Electroencephalography and functional Magnetic Resonance Imaging (EEG-fMRI) data in epilepsy. The method is based on the decomposition of the EEG signal using independent component analysis (ICA) and the usage of the relevant components' time courses to define the event related model necessary to find the regions exhibiting fMRI signal changes related to interictal activity. This approach achieves a natural data-driven differentiation of the role of distinct types of interictal activity with different amplitudes and durations in the epileptogenic process. Agreement between the conventional method and this new approach was obtained in 6 out of 9 patients that had interictal activity inside the scanner. In all cases, the maximum Z-score was greater in the fMRI studies based on ICA component method and the extent of activation was increased in 5 out of the 6 cases in which overlap was found. Furthermore, the three cases where an agreement was not found were those in which no significant activation was found at all using the conventional approach.

Specific retinotopically based magnocellular impairment in a patient with medial visual dorsal stream damage.

We report here retinotopically based magnocellular deficits in a patient with a unilateral parieto-occipital lesion. We applied convergent methodologies to study his dorsal stream processing, using psychophysics as well as structural and functional imaging. Using standard perimetry we found deficits involving the periphery of the left inferior quadrant abutting the horizontal meridian, suggesting damage of dorsal retinotopic representations beyond V1. Retinotopic damage was much more extensive when probed with frequency-doubling based contrast sensitivity measurements, which isolate processing within the magnocellular pathway: sensitivity losses now encroached on the visual central representation and did not respect the horizontal meridian, suggesting further damage to dorsal stream retinotopic areas that contain full hemi-field representations, such as human V3A or V6. Functional imaging revealed normal responses of human MT+ to motion contrast. Taken together, these findings are consistent with a recent proposal of two distinct magnocellular dorsal stream pathways: a latero-dorsal pathway passing to MT+ and concerned with the processing of coherent motion, and a medio-dorsal pathway that routes information from V3A to the human homologue of V6. Anatomical evidence was consistent with sparing of the latero-dorsal pathway in our patient, and was corroborated by his normal performance in speed, direction discrimination and motion coherence tasks with 2D and 3D objects. His pattern of dysfunction suggests damage only to the medio-dorsal pathway, an inference that is consistent with structural imaging data, which revealed a lesion encompassing the right parieto-occipital sulcus.

USPIO-enhanced magnetic resonance imaging for nodal staging in patients with head and neck cancer.

PURPOSE: To determine the accuracy of ultrasmall superparamagnetic iron oxide (USPIO)-enhanced magnetic resonance imaging (MRI) for nodal staging in patients with head and neck cancer. MATERIALS AND METHODS: Twenty patients with carcinomas of the upper aerodigestive tract were prospectively enrolled. MRI was performed before and 24-36 hours after intravenous infusion of an USPIO agent, ferumoxtran-10 (Sinerem; Guerbet, France; and Combidex; Advanced Magnetics) at a dose of 2.6 mg Fe/kg using T2-weighted spin-echo and gradient-echo sequences. Surgery was performed the same day or the day after the ferumoxtran-10-enhanced MR examination. Based on MRI, selected nodes were surgically removed and directly correlated with pathology using hematoxylin-eosin (H&E) and Perls stainings. RESULTS: A total of 63 nodes were studied; 36 were nonmetastatic, 25 metastatic, and two inflammatory. Ferumoxtran-10-enhanced MRI allowed diagnosis of 24 metastatic and 30 nonmetastatic nodes, yielding a sensitivity of 96%, a specificity of 78.9%, a positive predictive value of 75%, and a negative predictive value of 96.8%, compared to 64%, 78.9%, 66.6%, and 76.9%, respectively, for nonenhanced MRI. Accuracy of ferumoxtran-10-enhanced MRI was 85.7%. The gradient-echo T2-weighted sequence was the most accurate to detect signal loss in nonmetastatic nodes. CONCLUSION: USPIO-enhanced MRI is useful for nodal staging of patients with head and neck cancers.