CAMRT Radiography Practice Exam

Why is a PA projection of the patella preferred over an AP projection?

1. Less OID

2. Less distortion of patella

3. Less magnification of patella

4. All of the above

The correct answer is: All of the above

The preference for a PA projection of the patella over an AP projection stems from several beneficial factors that enhance the quality of the radiographic image. Firstly, the PA projection typically results in less object-to-image distance (OID). This is advantageous because a lower OID minimizes the blurring of the image and enhances the detail of the patella, ultimately improving the diagnostic quality of the radiograph. Secondly, the PA projection allows for less distortion of the patella. The alignment of the x-ray beam and the anatomical structure in the PA view facilitates a more accurate representation of the patellar anatomy. This effect is particularly important for precise evaluations of the patella's shape and position, which are critical for assessing conditions like patellar fractures or dislocations. Thirdly, the PA projection also reduces the magnification of the patella. In an AP projection, the distance between the x-ray tube and the patella is generally greater, which can lead to a larger image size due to magnification. A reduced magnification in the PA projection helps radiologists assess the patella more accurately in terms of its dimensions and spatial relationships with adjacent structures. Collectively, these attributes—reduced OID, distortion, and magnification—contribute to the