Emerson Leandro Gasparetto

Pseudoprogression and Pseudoresponse: Imaging Challenges in the Assessment of Posttreatment Glioma

The current standard of care for newly diagnosed cases of high-grade glioma is surgical resection followed by RT with concurrent chemotherapy. The most widely used criteria for assessing treatment response are based on a 2D measurement of the enhancing area on MR imaging known as the Macdonald Criteria. Recently, nontumoral increases (pseudoprogression) and decreases (pseudoresponse) in enhancement have been found, and these can confuse outcome evaluation. Here we review pseudoprogression and pseudoresponse and describe how better understanding of these phenomena can aid interpretation.

Assessment of Breast Lesions With Diffusion-Weighted MRI: Comparing the Use of Different b Values

OBJECTIVE Our purpose was to study the utility of diffusion-weighted MRI in differentiating benign from malignant breast lesions by assessing the best b values. SUBJECTS AND METHODS Forty-five women (mean age, 46.1 years) with 52 focal mass breast lesions underwent diffusion-weighted imaging with different b values. The apparent diffusion coefficient (ADC) value of each lesion was calculated from the ADC maps done using five b values (0, 250, 500, 750, and 1,000 s/mm(2)) and using b values of 0 s/mm(2) with each other b value separately (0 and 250 s/mm(2), 0 and 500 s/mm(2), 0 and 750 s/mm(2), 0 and 1,000 s/mm(2)). The mean ADC values were correlated with imaging findings and histopathologic diagnoses. The cutoff ADC value, sensitivity, and specificity of diffusion-weighted imaging to differentiate benign and malignant lesions were calculated in all b value combinations. A p value of < 0.05 was considered statistically significant. RESULTS The mean ADC value was significantly lower for malignant lesions compared to benign lesions (p < 0.0001) in all b value combinations. No statistical difference was seen between the ADC obtained from different b value combinations (p = 0.2581) in the differentiation between benign and malignant lesions. The ADC calculated from b 0 and 750 s/mm(2) was slightly better than the other b value combinations, showing a sensitivity of 92.3% and a specificity of 96.2%. CONCLUSION Diffusion-weighted imaging is a potential resource as a coadjutant of MRI in the differentiation between benign and malignant lesions. Such imaging can be performed without a significant increase in examination time, especially because it can be done with lower b values.

Susceptibility-Weighted Imaging for the Evaluation of Patients with Familial Cerebral Cavernous Malformations: A Comparison with T2-Weighted Fast Spin-Echo and Gradient-Echo Sequences

BACKGROUND AND PURPOSE: The T2-weighted gradient-echo (GRE) imaging is currently the gold standard MR imaging sequence for the evaluation of patients with cerebral cavernous malformation (CCM) lesions. We aimed to compare the sensitivity of susceptibility-weighted imaging (SWI) with T2-weighted fast spin-echo (FSE) and GRE imaging in assigning the number of CCM lesions in patients with the familial form of the disease. Materials and METHODS: We studied 15 patients (8 men, 7 women; mean age, 34 years) with familial CCM. All patients underwent MR imaging with the following sequences: T1-weighted spin echo, T2-weighted FSE, T2-weighted GRE, and SWI. Two neuroradiologists read the images regarding the number of lesions seen on each sequence. The final decisions were reached by consensus. The number of lesions on the different sequences was compared with analysis of variance, followed by a nonparametric Wilcoxon matched-pairs signed rank test. RESULTS: The number of lesions was higher on T2-weighted GRE than on T2-weighted FSE (P = .001). In addition, more lesions were seen on SWI than on T2-weighted GRE (P = .001) and FSE (P = .001) sequences. CONCLUSION: The sensitivity of SWI in assigning the number of CCM lesions in patients with the familial form of the disease is significantly higher than that of T2-weighted FSE and GRE sequences.

Diffusion Tensor Imaging Findings in School-Aged Autistic Children

To analyze and compare cerebral white matter tracts through diffusion tensor imaging in autistic and normal children.

Gliomas and the vascular fragility of the blood brain barrier

Astrocytes, members of the glial family, interact through the exchange of soluble factors or by directly contacting neurons and other brain cells, such as microglia and endothelial cells. Astrocytic projections interact with vessels and act as additional elements of the Blood Brain Barrier (BBB). By mechanisms not fully understood, astrocytes can undergo oncogenic transformation and give rise to gliomas. The tumors take advantage of the BBB to ensure survival and continuous growth. A glioma can develop into a very aggressive tumor, the glioblastoma (GBM), characterized by a highly heterogeneous cell population (including tumor stem cells), extensive proliferation and migration. Nevertheless, gliomas can also give rise to slow growing tumors and in both cases, the afflux of blood, via BBB is crucial. Glioma cells migrate to different regions of the brain guided by the extension of blood vessels, colonizing the healthy adjacent tissue. In the clinical context, GBM can lead to tumor-derived seizures, which represent a challenge to patients and clinicians, since drugs used for its treatment must be able to cross the BBB. Uncontrolled and fast growth also leads to the disruption of the chimeric and fragile vessels in the tumor mass resulting in peritumoral edema. Although hormonal therapy is currently used to control the edema, it is not always efficient. In this review we comment the points cited above, considering the importance of the BBB and the concerns that arise when this barrier is affected.

Potential Role of Diffusion Tensor MRI in the Differential Diagnosis of Mild Cognitive Impairment and Alzheimer's Disease

OBJECTIVE The purpose of this study was to evaluate the fractional anisotropy values of several white matter tracts with the aim of differentiating a healthy population from persons with mild cognitive impairment or Alzheimers disease. SUBJECTS AND METHODS Seventy-nine patients with memory impairment and 16 volunteer controls participated in the study. MRI was performed with a 1.5-T system. Conventional MR images and diffusion tensor images were obtained for all participants. The diffusion tensor imaging data were postprocessed, and low b-value, fractional anisotropy, and fractional anisotropy color-coded maps were calculated. With the three maps as an anatomic reference, fractional anisotropy was measured for hippocampal formations, superior longitudinal fascicles, posterior cingulate gyri, and the splenium of the corpus callosum. Kruskal-Wallis and Steel-type multiple-comparison nonparametric tests were performed for the statistical analysis. RESULTS The fractional anisotropy values for the splenium of the corpus callosum, bilateral posterior cingulate gyri, and bilateral superior longitudinal fascicles of patients with mild cognitive impairment and those with probable Alzheimers disease were significantly lower than the values of controls. No differences were found in hippocampal formations in any group. No significant difference was found in fractional anisotropy values in comparisons of mild cognitive impairment versus possible Alzheimers disease and probable Alzheimers disease or comparisons of probable Alzheimers disease and possible Alzheimers disease. CONCLUSION Diffusion tensor imaging is a promising technique for the evaluation of patients with probable mild cognitive impairment. Early detection of the disease expands the treatment options, increasing the likelihood of a good clinical response and enhancing the quality of life of patients and their relatives. Further studies with larger populations are needed to confirm the role of diffusion tensor imaging in the evaluation of memory impairment.

Optimized labeling of bone marrow mesenchymal cells with superparamagnetic iron oxide nanoparticles and in vivo visualization by magnetic resonance imaging

BackgroundStem cell therapy has emerged as a promising addition to traditional treatments for a number of diseases. However, harnessing the therapeutic potential of stem cells requires an understanding of their fate in vivo. Non-invasive cell tracking can provide knowledge about mechanisms responsible for functional improvement of host tissue. Superparamagnetic iron oxide nanoparticles (SPIONs) have been used to label and visualize various cell types with magnetic resonance imaging (MRI). In this study we performed experiments designed to investigate the biological properties, including proliferation, viability and differentiation capacity of mesenchymal cells (MSCs) labeled with clinically approved SPIONs.ResultsRat and mouse MSCs were isolated, cultured, and incubated with dextran-covered SPIONs (ferumoxide) alone or with poly-L-lysine (PLL) or protamine chlorhydrate for 4 or 24 hrs. Labeling efficiency was evaluated by dextran immunocytochemistry and MRI. Cell proliferation and viability were evaluated in vitro with Ki67 immunocytochemistry and live/dead assays. Ferumoxide-labeled MSCs could be induced to differentiate to adipocytes, osteocytes and chondrocytes. We analyzed ferumoxide retention in MSCs with or without mitomycin C pretreatment. Approximately 95% MSCs were labeled when incubated with ferumoxide for 4 or 24 hrs in the presence of PLL or protamine, whereas labeling of MSCs incubated with ferumoxide alone was poor. Proliferative capacity was maintained in MSCs incubated with ferumoxide and PLL for 4 hrs, however, after 24 hrs it was reduced. MSCs incubated with ferumoxide and protamine were efficiently visualized by MRI; they maintained proliferation and viability for up to 7 days and remained competent to differentiate. After 21 days MSCs pretreated with mitomycin C still showed a large number of ferumoxide-labeled cells.ConclusionsThe efficient and long lasting uptake and retention of SPIONs by MSCs using a protocol employing ferumoxide and protamine may be applicable to patients, since both ferumoxides and protamine are approved for human use.

Biodistribution of bone marrow mononuclear cells after intra-arterial or intravenous transplantation in subacute stroke patients

AIMS To assess the biodistribution of bone marrow mononuclear cells (BMMNC) delivered by different routes in patients with subacute middle cerebral artery ischemic stroke. PATIENTS & METHODS This was a nonrandomized, open-label Phase I clinical trial. After bone marrow harvesting, BMMNCs were labeled with technetium-99m and intra-arterially or intravenously delivered together with the unlabeled cells. Scintigraphies were carried out at 2 and 24 h after cell transplantation. Clinical follow-up was continued for 6 months. RESULTS Twelve patients were included, between 19 and 89 days after stroke, and received 1-5 × 10(8) BMMNCs. The intra-arterial group had greater radioactive counts in the liver and spleen and lower counts in the lungs at 2 and 24 h, while in the brain they were low and similar for both routes. CONCLUSION BMMNC labeling with technetium-99m allowed imaging for up to 24 h after intra-arterial or intravenous injection in stroke patients.

High-Resolution CT Findings of 77 Patients with Untreated Pulmonary Paracoccidioidomycosis

OBJECTIVE The objective of our study was to describe the high-resolution CT findings of 77 patients with pulmonary paracoccidioidomycosis (PCM) who had not yet been treated for PCM. MATERIALS AND METHODS The high-resolution CT scans of 77 consecutive patients with proven pulmonary PCM were reviewed by two chest radiologists, and decisions regarding the CT findings were reached by consensus. Seventy-one of the patients were men and six were women, with an average age of 49 years. The criteria for interpretation of the high-resolution CT scans are defined in the Fleischner Societys Glossary of Terms. RESULTS The most frequent high-resolution CT findings were ground-glass attenuation areas (58.4%), small centrilobular nodules (45.5%), cavitated nodules (42.9%), large nodules (41.6%), parenchymal bands (33.8%), areas of cicatricial emphysema (33.8%), interlobular septal thickening (31.2%), and architectural distortion (29.9%). Most of these high-resolution CT findings predominated at the periphery (53%) and posterior (88%) regions involving all lung zones, with discrete predominance in the middle zones (35%). CONCLUSION The high-resolution CT findings of patients with pulmonary PCM who have not yet been treated consist of ground-glass attenuation areas associated with small centrilobular nodules, cavitated nodules, large nodules, parenchymal bands, and areas of cicatricial emphysema. These abnormalities are usually distributed in the posterior and peripheral regions of the lungs, with discrete predominance in the middle lung zones.

Evaluation of hippocampal volume based on MR imaging in patients with bipolar affective disorder applying manual and automatic segmentation techniques.

To compare the hippocampal volumes in patients with bipolar disorder (BD) and healthy controls, obtained by applying different segmentation methods (manual, Freesurfer [FS], and FSL).