Which projection of the chest is best for demonstrating the retrocardiac space?

The best projection of the chest for demonstrating the retrocardiac space is the right anterior oblique (RAO) position. This projection allows for a clear visualization of the region behind the heart, where the retrocardiac space lies. In the RAO position, the heart is slightly rotated away from the film, which can help reduce the cardiac silhouette's shadow and provide a better view of the retrocardiac areas.

Additionally, the RAO position can enhance the visibility of other structures such as the aortic arch and the right lung's hilar region, further assisting in thorough examination of mediastinal structures. This is particularly important in evaluating conditions such as tumors or lymphadenopathy in that area. Thus, the RAO projection is most effective for assessing the retrocardiac space detailedly compared to other chest projections.