Evaluating the effectiveness of different perceptual training methods in a difficult visual discrimination task with ultrasound images.

Recent work has shown that perceptual training can be used to improve the performance of novices in real-world visual classification tasks with medical images, but it is unclear which perceptual training methods are the most effective, especially for difficult medical image discrimination tasks. We investigated several different perceptual training methods with medically naïve participants in a difficult radiology task: identifying the degree of hepatic steatosis (fatty infiltration of the liver) in liver ultrasound images. In Experiment 1a (N = 90), participants completed four sessions of standard perceptual training, and participants in Experiment 1b (N = 71) completed four sessions of comparison training. There was a significant post-training improvement for both types of training, although performance was better when the trained task aligned with the task participants were tested on. In both experiments, performance initially improves rapidly, with learning becoming more gradual after the first training session. In Experiment 2 (N = 200), we explored the hypothesis that performance could be improved by combining perceptual training with explicit annotated feedback presented in a stepwise fashion. Although participants improved in all training conditions, performance was similar regardless of whether participants were given annotations, or underwent training in a stepwise fashion, both, or neither. Overall, we found that perceptual training can rapidly improve performance on a difficult radiology task, albeit not to a comparable level as expert performance, and that similar levels of performance were achieved across the perceptual training paradigms we compared.

Opercular perivascular cysts: A proposed new subtype of dilated perivascular spaces.

PURPOSE: Dilated perivascular spaces are a common finding on brain MRI, traditionally classified into three types based on location and relationship to vessels. Recent studies have characterised an additional variant of dilated perivascular spaces that arise within the anterior temporal lobe and have unique neuroimaging features. These particular perivascular spaces are associated with a vascular loop of a branch of the middle cerebral artery (MCA) and commonly demonstrate perilesional T2/FLAIR signal. To our knowledge, these have not previously been described in the frontal lobe. METHOD: Dilated perivascular spaces associated with a vascular loop of a branch of the middle cerebral artery (MCA) identified at our institution were reviewed for imaging characteristics and anatomical location. RESULTS: 18 cases were identified. 16 were located in the anterior temporal lobe and two were located in the frontal operculum. All demonstrated internal signal characteristics identical to CSF on all sequences, with no contrast enhancement or susceptibility artefact and variable perilesional T2/FLAIR signal. CONCLUSIONS: We report further evidence of a distinct subtype of dilated perivascular spaces occurring in the anterior temporal lobe in association with a vascular loop of a branch of the MCA. In addition, we have demonstrated that these may also occur in the frontal operculum. We therefore suggest that these dilated perivascular spaces of the operculum be recognised as a separate, fourth, subtype of perivascular space and propose the term "opercular perivascular cyst".

An ovine model of cerebral catheter venography for implantation of an endovascular neural interface.

OBJECTIVE Neural interface technology may enable the development of novel therapies to treat neurological conditions, including motor prostheses for spinal cord injury. Intracranial neural interfaces currently require a craniotomy to achieve implantation and may result in chronic tissue inflammation. Novel approaches are required that achieve less invasive implantation methods while maintaining high spatial resolution. An endovascular stent electrode array avoids direct brain trauma and is able to record electrocorticography in local cortical tissue from within the venous vasculature. The motor area in sheep runs in a parasagittal plane immediately adjacent to the superior sagittal sinus (SSS). The authors aimed to develop a sheep model of cerebral venography that would enable validation of an endovascular neural interface. METHODS Cerebral catheter venography was performed in 39 consecutive sheep. Contrast-enhanced MRI of the brain was performed on 13 animals. Multiple telescoping coaxial catheter systems were assessed to determine the largest wide-bore delivery catheter that could be delivered into the anterior SSS. Measurements of SSS diameter and distance from the motor area were taken. The location of the motor area was determined in relation to lateral and superior projections of digital subtraction venography images and confirmed on MRI. RESULTS The venous pathway from the common jugular vein (7.4 mm) to the anterior SSS (1.2 mm) was technically challenging to selectively catheterize. The SSS coursed immediately adjacent to the motor cortex (< 1 mm) for a length of 40 mm, or the anterior half of the SSS. Attempted access with 5-Fr and 6-Fr delivery catheters was associated with longer procedure times and higher complication rates. A 4-Fr catheter (internal lumen diameter 1.1 mm) was successful in accessing the SSS in 100% of cases with no associated complications. Complications included procedure-related venous dissection in two major areas: the torcular herophili, and the anterior formation of the SSS. The bifurcation of the cruciate sulcal veins with the SSS was a reliable predictor of the commencement of the motor area. CONCLUSIONS The ovine model for cerebral catheter venography has generalizability to the human cerebral venous system in relation to motor cortex location. This novel model may facilitate the development of the novel field of endovascular neural interfaces that may include preclinical investigations for cortical recording applications such as paralysis and epilepsy, as well as other potential applications in neuromodulation.