Numerical observer for atherosclerotic plaque classification in spectral computed tomography

Preliminary study on the differentiation of vulnerable carotid plaques via analysis of calcium content and spectral curve slope by using gemstone spectral imaging

Growing evidence indicates that vulnerable carotid plaque rupture is an important cause of stroke. However, the role of novel gemstone spectral imaging (GSI) in the assessment of vulnerable carotid plaques has remained to be sufficiently explored. Therefore, the aim of the present study was to provide a comprehensive evaluation of carotid atherosclerotic plaques using both GSI imaging biomarkers and serological biomarkers, and further explore their possible roles in the atherogenic process. The present study analyzed GSI data, including calcium content of carotid atherosclerotic plaques and spectral curve slope, as well as serum high-sensitivity C-reactive protein (Hs-CRP) and monocyte chemotactic protein-1 (MCP-1) levels in patients with a carotid atherosclerotic plaque using GSI-computed tomographic angiography and immunoturbidimetry. Patients with unstable plaque exhibited a significantly lower calcium content and higher spectral curve slope than those of the stable plaque group. In addition, patients with unstable plaque exhibited an increase in Hs-CRP and MCP-1 levels compared with those of the stable plaque and normal control groups. The alteration in GSI calcium content and spectral curve slope reflects a close link between calcification and plaque instability, while aberrant Hs-CRP and MCP-1 expression are involved in the formation or development of vulnerable plaques. Taken together, the present results strongly support the feasibility of using these serological and newly identified imaging parameters as multiple potential biomarkers relevant to plaque vulnerability or stroke progression.

Arrangement of boundary electrodes for detection of frontal lobe disease with electrical impedance tomography

Purpose: Caused by brain trauma or blood vessel abnormality, intracerebral hemorrhage and secondary ischemia have become prevalent and severe neurological diseases. The timely and accurate detection of disease is essential for the recovery of patients. As an emerging visualization technique, electrical impedance tomography (EIT) offers an alternative. It is able to reconstruct the conductivity distribution that reflects the pathological variation of human tissue. Approach: In the EIT-based detection, electrodes are usually in uniform arrangement, which may be not suitable in some conditions. To enhance sensitivity in the region of interest, EIT with a novel offset arrangement of boundary electrodes is proposed to image a simulated frontal lobe hemorrhage and secondary ischemia. To cope with the ill-posed inverse problem, the L1 regularization method is developed during the reconstruction. In addition, the impact of noise with a signal-to-noise ratio of 56 dB is studied. Results: Compared with the traditional uniform electrode arrangement, the results demonstrate that EIT with the proposed offset arrangement of electrodes is more advantageous for imaging frontal lobe disease. Conclusions: The proposed offset arrangement of electrodes is superior to the traditional uniform arrangement in imaging frontal lobe disease, especially under the impact of noise.

The role of extra-foveal processing in 3D imaging

The field of medical image quality has relied on the assumption that metrics of image quality for simple visual detection tasks are a reliable proxy for the more clinically realistic visual search tasks. Rank order of signal detectability across conditions often generalizes from detection to search tasks. Here, we argue that search in 3D images represents a paradigm shift in medical imaging: radiologists typically cannot exhaustively scrutinize all regions of interest with the high acuity fovea requiring detection of signals with extra-foveal areas (visual periphery) of the human retina. We hypothesize that extra-foveal processing can alter the detectability of certain types of signals in medical images with important implications for search in 3D medical images. We compare visual search of two different types of signals in 2D vs. 3D images. We show that a small microcalcification-like signal is more highly detectable than a larger mass-like signal in 2D search, but its detectability largely decreases (relative to the larger signal) in the 3D search task. Utilizing measurements of observer detectability as a function retinal eccentricity and observer eye fixations we can predict the pattern of results in the 2D and 3D search studies. Our findings: 1) suggest that observer performance findings with 2D search might not always generalize to 3D search; 2) motivate the development of a new family of model observers that take into account the inhomogeneous visual processing across the retina (foveated model observers).