Multiscale extraction of hypodensity in hyperacute stroke

Stroke is a syndrome characterized by a sudden neurological deficit caused by cerebral ischemia. Computed tomography (CT) plays a crucial role in the evaluation of stroke patients even though it is not sufficient enough to extract the hypodense area corresponding to the infracted cerebral tissues in hyperacute stage. Careful selection of patients for thrombolytic therapy is fundamental to improve safety and efficacy; therefore the authors propose an additional, wavelet-based post-processing method for extracting hypodensity in CT scans in hyperacute stroke patients.

A retrospective evaluation of 52 sets of examinations conducted in patients admitted with symptoms suggestive of stroke was undertaken by four radiologists unaware of the final clinical findings. All of the selected cases were considered as having no direct signs of hyperacute ischemia in the localization corresponding with clinical manifestation and follow-up studies. In the first stage, only CTs performed at admission were evaluated; a month later the same scans were reevaluated with additional use of a "stroke monitor". All sets were evaluated independently. Follow-up CT exam and/or the clinical picture confirmed or excluded the diagnosis.

Higher AUC values were found for the "stroke monitor"-aided radiological diagnosis for all the radiologists and the differences were significant for all subgroups (p<0.05) apart from the subgroup in which CT scans of patients with significant cerebral atrophy were excluded.

Combining the results of CT and the "stroke monitor" provided a better diagnosis of stroke, especially in atrophic brains. Planned prospective studies will allow evaluation of the impact on the further treatment of hyperacute stroke patients.