American Registry of Radiologic Technologists (ARRT) Practice Exam

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Prepare for the American Registry of Radiologic Technologists Test with engaging quizzes and detailed explanations. Boost your test readiness with multiple-choice questions designed to enhance your knowledge and confidence.

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When do the petrous ridges fill the orbits?

PA view
Caldwell at 25 degrees
Anterior-posterior view
Basic view

The correct answer is: PA view

The petrous ridges fill the orbits in the posteroanterior (PA) view. This occurs because in the PA projection, the x-ray beam passes perpendicular to the orbit, allowing the petrous part of the temporal bone to project directly into the orbits. The orientation of the skull in this view is such that the petrous ridges are located at the highest point, projecting more horizontally across the orbits than in other views. In other projections, such as the Caldwell projection at 25 degrees, the petrous ridges typically do not fill the orbits because the beam is angled, allowing them to project below the level of the orbits. Similarly, in the anterior-posterior view and basic views, the angles and positions of the skull and the x-ray beam do not align in a way that the petrous ridges fill the orbits. Understanding the anatomy and projection principles helps in recognizing the relationship between the position of the x-ray tube, the patient, and the resultant image.