Intracranial arteriovenous malformations

AbstractIntracranial arteriovenous malformations (AVM) are rare lesions that are often discovered fortuitously. They should be identified on CT scan and MRI before resorting to angiography; the latter is used to prepare the treatment. This article describes the various types of subpial or dural AVM and the specific characteristics that enable their differentiation with non-invasive imaging. The factors that determine the severity of these lesions, whether discovered before or after a haemorrhage, are described, as well as prognostic indicators

Direct and inverse pumping in flows with homogeneous and non-homogeneous swirl

The conditions in which meridional recirculations appear in swirling flows above a fixed wall are analysed. In the classical Bodew\"adt problem, where the swirl tends towards an aysmptotic value away from the wall, the well-known "tea-cup effect" drives a flow away from the plate at the centre of the vortex. Simple dimensional arguments applied to a single vortex show that if the intensity of the swirl decreases away from the wall, the sense of the recirculation can be inverted, and that the associated flow rate scales with the swirl gradient. Only if the flow is quasi-2D, does the classical tea-cup effect take place. This basic theory is confirmed by numerical simulations of a square array of steady, electrically driven vortices. Experiments in the turbulent regimes of the same configuration reveal that these mechanisms are active in the average flow and in its fluctuating part. The mechanisms singled out in this letter provide an explanation for previously observed phenomena in electrolyte flows. They also put forward a possible mechanism for the generation of helicity in flows close to two-dimensionality, which plays a key role in the transition between 2D and 3D turbulence

Importance of histological tumor response assessment in predicting the outcome in patients with colorectal liver metastases treated with neo-adjuvant chemotherapy followed by liver surgery

Background: The purpose of the study was to characterize histological response to chemotherapy of hepatic colorectal metastases (HCRM), evaluate efficacy of different chemotherapies on histological response, and determine whether tumor regression grading (TRG) of HCRM predicts clinical outcome. Patients and methods: TRG was evaluated on 525 HCRM surgically resected from 181 patients, 112 pretreated with chemotherapy. Disease-free survival (DFS) and overall survival (OS) were correlated to TRG. Results: Tumor regression was characterized by fibrosis overgrowing on tumor cells, decreased necrosis, and tumor glands (if present) at the periphery of HCRM. With irinotecan/5-fluorouracil (5-FU), major (MjHR), partial (PHR), and no (NHR) histological tumor regression were observed in 17%, 13%, and 70% of patients, respectively. With oxaliplatin/5-FU, MjHR, PHR, and NHR were observed in 37%, 45%, and 18% of patients, respectively. Five patients, treated with oxaliplatin, had complete response in all their metastases. MjHR was associated with an improved 3-year DFS compared with PHR or NHR. MjHR and PHR were associated with an improved 5-year OS compared with NHR. Conclusion: Histological tumor regression of HCRM to chemotherapy corresponds to fibrosis overgrowth and not to increase of necrosis. TRG should be considered when evaluating efficacy of chemotherapy for HCRM. Histological tumor regression was most common among oxaliplatin-treated patients and associated with better clinical outcom

Severe hepatic sinusoidal obstruction associated with oxaliplatin-based chemotherapy in patients with metastatic colorectal cancer

Background: In advanced metastatic colorectal adenocarcinoma, the addition of a neo-adjuvant systemic treatment to surgery might translate into a survival advantage, although this is yet to be confirmed by ongoing randomized trials. The objective of this study was to assess the effects of preoperative systemic chemotherapy on the morphology of non-tumoral liver. Patients and methods: A large series of surgically resected liver metastases (n = 153) was selected. Light microscopy, electron microscopy, and immunohistochemistry using antibodies against endothelial cells (CD31) and hepatic stellate cells (α-SM actin, CRBP-1) were performed to identify sinusoidal wall integrity. Results: We found that 44 (51%) of the 87 post-chemotherapic liver resection specimens had sinusoidal dilatation and hemorrhage, related to rupture of the sinusoidal barrier. In contrast, the 66 livers treated by surgery alone remained normal. In 21 out of the 44 post-chemotherapy patients (48%), perisinusoidal and veno-occlusive fibrosis also developed. Sinusoidal injury persisted several months after end of chemotherapy, and fibrosis may progress. Development of lesions was strongly correlated to the use of oxaliplatin; 34 out of 43 patients (78%) treated with this drug showed striking sinusoidal alterations. Conclusions: Systemic neo-adjuvant chemotherapy in metastatic colorectal cancer frequently causes morphological lesions involving hepatic microvasculature. Sinusoidal obstruction, complicated by perisinusoidal fibrosis and veno-occlusive lesion of the non-tumoral liver revealed by this study, should be included in the list of the adverse side-effects of colorectal systemic chemotherapy, in particular related to the use of oxaliplati

Comparative overwiew of brain perfusion imaging techniques

Background and Purpose - Numerous imaging techniques have been developed and applied to evaluate brain hemodynamics. Among these are positron emission tomography, single photon emission computed tomography, Xenon-enhanced computed tomography, dynamic perfusion computed tomography, MRI dynamic susceptibility contrast, arterial spin labeling, and Doppler ultrasound. These techniques give similar information about brain hemodynamics in the form of parameters such as cerebral blood flow or cerebral blood volume. All of them are used to characterize the same types of pathological conditions. However, each technique has its own advantages and drawbacks. Summary of Review - This article addresses the main imaging techniques dedicated to brain hemodynamics. It represents a comparative overview established by consensus among specialists of the various techniques. Conclusions - For clinicians, this article should offer a clearer picture of the pros and cons of currently available brain perfusion imaging techniques and assist them in choosing the proper method for every specific clinical setting

Comparative overview of brain perfusion imaging techniques Epub

Background and Purpose - Numerous imaging techniques have been developed and applied to evaluate brain hemodynamics. Among these are positron emission tomography, single photon emission computed tomography, Xenon-enhanced computed tomography, dynamic perfusion computed tomography, MRI dynamic susceptibility contrast, arterial spin labeling, and Doppler ultrasound. These techniques give similar information about brain hemodynamics in the form of parameters such as cerebral blood flow or cerebral blood volume. All of them are used to characterize the same types of pathological conditions. However, each technique has its own advantages and drawbacks. Summary of Review - This article addresses the main imaging techniques dedicated to brain hemodynamics. It represents a comparative overview established by consensus among specialists of the various techniques. Conclusions - For clinicians, this article should offer a clearer picture of the pros and cons of currently available brain perfusion imaging techniques and assist them in choosing the proper method for every specific clinical setting

Analysis of two human pre-ribosomal factors, bystin and hTsr1, highlights differences in evolution of ribosome biogenesis between yeast and mammals

Recent studies reveal that maturation of the 40S ribosomal subunit precursors in mammals includes an additional step during processing of the internal transcribed spacer 1 (ITS1), when compared with yeast Saccharomyces cerevisiae, even though the protein content of the pre-40S particle appears to be the same. Here, we examine by depletion with siRNA treatment the function of human orthologs of two essential yeast pre-ribosomal factors, hEnp1/bystin and hTsr1. Like their yeast orthologs, bystin is required for efficient cleavage of the ITS1 and further processing of this domain within the pre-40S particles, whereas hTsr1 is necessary for the final maturation steps. However, bystin depletion leads to accumulation of an unusual 18S rRNA precursor, revealing a new step in ITS1 processing that potentially involves an exonuclease. In addition, pre-40S particles lacking hTsr1 are partially retained in the nucleus, whereas depletion of Tsr1p in yeast results in strong cytoplasmic accumulation of pre-40S particles. These data indicate that ITS1 processing in human cells may be more complex than currently envisioned and that coordination between maturation and nuclear export of pre-40S particles has evolved differently in yeast and mammalian cells

AJNR Am J Neuroradiol

Accurate quantification of WM lesion load is essential for the care of patients with multiple sclerosis. We tested whether the combination of accelerated 3D-FLAIR and denoising using deep learning-based reconstruction could provide a relevant strategy while shortening the imaging examination. Twenty-eight patients with multiple sclerosis were prospectively examined using 4 implementations of 3D-FLAIR with decreasing scan times (4 minutes 54 seconds, 2 minutes 35 seconds, 1 minute 40 seconds, and 1 minute 15 seconds). Each FLAIR sequence was reconstructed without and with denoising using deep learning-based reconstruction, resulting in 8 FLAIR sequences per patient. Image quality was assessed with the Likert scale, apparent SNR, and contrast-to-noise ratio. Manual and automatic lesion segmentations, performed randomly and blindly, were quantitatively evaluated against ground truth using the absolute volume difference, true-positive rate, positive predictive value, Dice similarity coefficient, Hausdorff distance, and F1 score based on the lesion count. The Wilcoxon signed-rank test and 2-way ANOVA were performed. Both image-quality evaluation and the various metrics showed deterioration when the FLAIR scan time was accelerated. However, denoising using deep learning-based reconstruction significantly improved subjective image quality and quantitative performance metrics, particularly for manual segmentation. Overall, denoising using deep learning-based reconstruction helped to recover contours closer to those from the criterion standard and to capture individual lesions otherwise overlooked. The Dice similarity coefficient was equivalent between the 2-minutes-35-seconds-long FLAIR with denoising using deep learning-based reconstruction and the 4-minutes-54-seconds-long reference FLAIR sequence. Denoising using deep learning-based reconstruction helps to recognize multiple sclerosis lesions buried in the noise of accelerated FLAIR acquisitions, a possibly useful strategy to efficiently shorten the scan time in clinical practice.Translational Research and Advanced Imaging Laborator