Which of the following access sheath sizes is considered to be the largest?

The largest access sheath size among the options is 11 French (fr). In interventional radiology, access sheaths are often measured in French units, with one French unit equivalent to 1/3 mm in diameter. Therefore, an 11 fr sheath has a diameter of approximately 3.67 mm, making it the largest choice provided.

Access sheaths serve as a conduit for instruments and catheters during various procedures, allowing for easier access and manipulation within the vascular system. The larger the sheath, the more instruments can be accommodated, which can be particularly beneficial in complex procedures requiring several tools or larger devices.

The other sheath sizes—8 fr, 9 fr, and 7 fr—are smaller in diameter compared to the 11 fr option, meaning they cannot facilitate the same range of devices or instruments. Hence, the presence of smaller units limits their utility in certain situations where larger access may be required. In summary, 11 fr is recognized as the largest access sheath option, providing greater versatility for procedural interventions.