Grayscale Inversion to aid Diagnosis of Acute Occlusive and Chronic Pulmonary Embolism on CT

Pulmonary embolism (PE) is a potentially life-threatening disease requiring accurate diagnosis and treatment. CT pulmonary angiography (CTPA) has high accuracy for detecting PE.[1] CT is therefore the first-line diagnostic imaging modality in patients suspected of having acute PE. There are several tools described in the literature to improve our accuracy and confidence in diagnosing PE. For example, it is important to select an optimal display window width (W) and level (L) for evaluating the pulmonary arteries.[2] A filling defect representing PE can be masked in standard soft tissue window display setting around W:400, L:40; therefore, radiologists prefer to manually adjust it to a PE-specific window that is unique to each exam. This is done by widening the width and increasing the level, arriving close to the double-half setting (W: 2×, L: 0.5×) where × is the mean attenuation in Hounsfield units within the main pulmonary artery.[3]