Physiological effect of caffeine in neurological studies based on Susceptibility Weighted Imaging (SWI)

Introdução – O presente estudo avaliou o efeito da cafeína no valor da razão contraste ruído (CNR) em imagens SWI. Objetivos – Avaliar o efeito da cafeína qualitativamente e quantificado pelo cálculo do valor CNR em imagens de magnitude e MIP para as estruturas: veia cerebral interna, seio sagital superior, tórcula e artéria cerebral média. Metodologia – A população do estudo incluiu 24 voluntários saudáveis que estiveram pelo menos 24h privados da ingestão de cafeína. Adquiriram-se imagens SWI antes e após a ingestão de 100ml de café. Os voluntários foram subdivididos em quatro grupos de seis indivíduos/grupo e avaliados separadamente após decorrido um intervalo de tempo diferente para cada grupo (15, 25, 30 ou 45min pós-cafeína). Utilizou-se um scanner Siemens Avanto 1,5 T com bobine standard de crânio e os parâmetros: T2* GRE 3D de alta resolução no plano axial, TR=49; TE=40; FA=15; FOV=187x230; matriz=221x320. O processamento de imagem foi efetuado no software OsiriX® e a análise estatística no GraphPadPrism®. Resultados e Discussão – As alterações de sinal e diferenças de contraste predominaram nas estruturas venosas e não foram significantes na substância branca, LCR e artéria cerebral média. Os valores CNR pré-cafeína diferiram significativamente do pós-cafeína nas imagens de magnitude e MIP na veia cerebral interna e nas imagens de magnitude do seio sagital superior e da tórcula (p<0,0001). Não se verificaram diferenças significativas entre os grupos avaliados nos diferentes tempos pós-cafeína. Conclusões – Especulamos que a cafeína possa vir a ser usada como agente de contraste nas imagens SWI barato, eficaz e de fácil administração.ABSTRACT: Introduction – The present study investigates the effect of caffeine on contrast-to-noise ratio (CNR) in SWI images. Purpose – Data analyses included qualitative and quantitative measures, specifically the CNR pre and post-ingestion, in magnitude and MIP images. The structures evaluated were internal cerebral vein, superior sagital sinus, torcula, and middle cerebral artery. Methodology – Twenty-four healthy volunteers were enrolled in the study. All the volunteers were caffeine-free for 24h prior to the test. SWI images were acquired before caffeine ingestion and post-ingestion of 100 ml of coffee. The volunteers were divided into four groups of six subjects and evaluated sequentially (15, 25, 30 and 45min after caffeine). High-resolution T2* weighted 3D GRE (SWI) sequence was acquired on the axial plane on a 1.5 T (Siemens Avanto) whole body scanner using the manufacturer’s standard head coil and the following parameters: TR=49; TE=40; FA=15; FOV=187x230; matrix=221x320. Statistics were performed with GraphPad Prism® and image analysis with Osirix®. Results and Discussion – We verified that signal alterations and contrast differences were predominant in venous structures and not significant in white matter, CSF and middle cerebral artery. The CNR values between pre and post-caffeine ingestion in magnitude and MIP images in internal cerebral vein (p<0.0001) and in magnitude images of superior sagittal sinus and tórcula showed significant differences CNR. There were no significant differences between groups evaluated at different times after the ingestion of caffeine. Conclusion – We speculate that caffeine can be used as a cost-effective, safe and easy to administrate contrast agent on SWI images

Efeito fisiológico da cafeína em estudos neurológicos com base na ponderação em susceptibilidade ferromagnética (SWI)

Introdução – O presente estudo avaliou o efeito da cafeína no valor da razão contraste ruído (CNR) em imagens SWI. Objetivos – Avaliar o efeito da cafeína qualitativamente e quantificado pelo cálculo do valor CNR em imagens de magnitude e MIP para as estruturas: veia cerebral interna, seio sagital superior, tórcula e artéria cerebral média. Metodologia – A população do estudo incluiu 24 voluntários saudáveis que estiveram pelo menos 24h privados da ingestão de cafeína. Adquiriram-se imagens SWI antes e após a ingestão de 100ml de café. Os voluntários foram subdivididos em quatro grupos de seis indivíduos/grupo e avaliados separadamente após decorrido um intervalo de tempo diferente para cada grupo (15, 25, 30 ou 45min pós-cafeína). Utilizou-se um scanner Siemens Avanto 1,5 T com bobine standard de crânio e os parâmetros: T2* GRE 3D de alta resolução no plano axial, TR=49; TE=40; FA=15; FOV=187x230; matriz=221x320. O processamento de imagem foi efetuado no software OsiriXâ e a análise estatística no GraphPadPrismâ. Resultados e Discussão – As alterações de sinal e diferenças de contraste predominaram nas estruturas venosas e não foram significantes na substância branca, LCR e artéria cerebral média. Os valores CNR pré-cafeína diferiram significativamente do pós-cafeína nas imagens de magnitude e MIP na veia cerebral interna e nas imagens de magnitude do seio sagital superior e da tórcula (p<0,0001). Não se verificaram diferenças significativas entre os grupos avaliados nos diferentes tempos pós-cafeína. Conclusões – Especulamos que a cafeína possa vir a ser usada como agente de contraste nas imagens SWI barato, eficaz e de fácil administração

Pre-operative tractography of the facial nerve in vestibular schwannomas: inter-observer agreement with surgical findings

Pre-operative diffusion tensor (DT) tractography is currently employed in our institutions. We use it to predict the course of the facial nerve (FN) in the vicinity of vestibular schwannomas (VS) of the cerebellopontine angle (CPA). In this study we were interested to assess the inter-observer reproducibility of this method. Two Neuroradiologists (PMGP and TT) determined independently the location of the FN by tractography and compared the results with in-vivo findings of microsurgery of VS

Structural connectivity of the brain: differences between a normal brain and a brain with pathology

Understanding the large-scale structural network formed by neurons is a major challenge in neuroscience. In this study we analyzed the structural connectivity of the human brain in 22 healthy subjects and in two patients with post-traumatic epilepsy. We evaluated the differences between these two groups. We also investigated differences in connectivity regarding gender and age in healthy individuals. For this purpose, we developed an analysis protocol using specialized software applications and we used graph theory metrics to characterize the structural connectivity between 118 different brain regions. Within the group of healthy subjects we found that men in general are those with higher average values of graph theory metrics. However, there were no significant differences in gender regarding global characterization of the brain. In addition, age was, in general, negatively correlated to the connectivity metrics. The brain regions where the most important differences were observed between healthy individuals and patients were: the Rolandic sulcus, the hippocampus, the pre-cuneus, the thalamus and the cerebellum bilaterally. These differences were consistent with theradiologic images of patients and the studied literature on post-traumatic epilepsy. Developments are expected for the study of the structural connectivity of the human brain, since its potential can be combined with other methods to characterize the disorders of brain circuits

Physiologic effect of caffeine on susceptibility-weighted imaging

Susceptibility-weighted imaging (SWI) is a relatively new contrast in MR imaging. Previous studies have found an effect of caffeine in the contrast generated by SWI images. The present study investigates the effect of caffeine on contrast-to-noise ratio (CNR) in SWI

Surgical proven location of the facial nerve in the vicinity of cerebellopontine angle tumours depicted pre-operatively by tractography

Purpose/Introduction: To determine the clinical utility of pre-operative diffusion tensor (DT) tractography of the facial nerve in the vicinity of cerebellopontine angle (CPA) tumours. The location of the facial nerve was established pre-operatively by tractography and compared with in-vivo electrode stimulation during microsurgery of vestibular schwannomas and rare CPA masses (meningiomas and arachnoid cysts)