American Society of Radiologic Technologist (ASRT) Practice Exam

In a submentovertical projection of the zygomatic arches, where is the central ray directed?

1. The level of the outer canthus

2. A level 1 inch posterior to the outer canthus

3. The level of the external acoustic meatus (EAM)

4. A level 1 inch posterior to the EAM

The correct answer is: A level 1 inch posterior to the outer canthus

The central ray in a submentovertical projection of the zygomatic arches is directed one inch posterior to the outer canthus. This positioning is critical for accurately visualizing the zygomatic arches because it ensures that the radiographic projection captures the desired structures without distortion. By centering the beam in this manner, the zygomatic arches can be projected clearly across the image, providing essential information for diagnosis and evaluation. This specific angling is based on anatomical landmarks that help to achieve the optimal projection. The outer canthus is a reliable point of reference, allowing radiologic technologists to consistently locate the correct positioning for the central ray. Proper alignment with this landmark minimizes superimposition of structures in the cranial region and ensures that the zygomatic arches are displayed in their true anatomic position. Without this technique, lesser accuracy in localization and potential for increased overlap of other cranial structures could occur, affecting the diagnostic quality of the imaging.