OPERA: a novel method to reduce ghost and aliasing artifacts.

OBJECTIVE: A method for Orthogonal Phase Encoding Reduction of Artifact (OPERA) was developed and tested. MATERIALS AND METHODS: Because the position of ghosts and aliasing artifacts is predictable along columns or rows, OPERA combines the intensity values of two images acquired using the same parameters, but with swapped phase-encoding directions, to correct the artifacts. Simulations and phantom experiments were conducted to define the efficacy, robustness, and reproducibility. Clinical validation was performed on a total of 1003 images by comparing the OPERA-corrected images and the corresponding image standard in terms of Signal-to-Noise Ratio (SNR) and Contrast-to-Noise Ratio (CNR). The method efficacy was also rated using a Likert-type scale response by two experienced independent radiologists using a single-blinded procedure. RESULTS: Simulations and phantom experiments demonstrated the robustness and effectiveness of OPERA in reducing artifacts strength. OPERA application did not significantly change the SNR [+ 4.16%; inter-quartile range (IQR): 2.72-5.01%] and CNR (+ 4.30%; IQR: 2.86-6.04%) values. The two radiologists observed a total of 893 original images with artifacts (89.03% of the total images), a reduction in the perceived artifacts of 82.0% and 83.9% (p < 0.0001), and an improvement in the perceived SNR (82.8% and 88.5%; K = 0.714) and perceived CNR (86.9-88.9%; K = 0.722). DISCUSSION: The study demonstrated that OPERA reduces MR artifacts and improves the perceived image quality.

A Case of Fatal Cerebral Air Embolism After Blunt Lung Trauma: Postmortem Computed Tomography and Autopsy Findings.

Cerebral air embolism is caused by gas bubbles in the vascular system. These bubbles can cause cerebral ischemia by obstructing encephalic blood vessels. It is frequently associated with blunt and penetrating chest trauma as well as iatrogenic interventions. Lung trauma involving laceration of the respiratory tract, lung parenchyma, and blood vessels may result in direct communication of these structures, driving air or gas into the pulmonary venous system. We report a case of a blunt chest trauma that led to massive arterial air embolism that was possible to recognize with the help of postmortem computed tomographic scan examination.