CAMRT Radiography Practice Exam

In a lateral L5/S1 lumbosacral x-ray, if the central ray is directed 5 cm anterior to the ASIS and 4 cm inferior to the iliac crest, what will be the outcome?

1. The central ray will be well superior to the L5/S1 junction

2. The central ray will be well anterior to the L5/S1 junction

3. The central ray will be well posterior to the L5/S1 junction

4. The central ray will be correctly centered to the L5/S1 junction

The correct answer is: The central ray will be well anterior to the L5/S1 junction

The central ray's positioning is critical in obtaining an optimal lateral L5/S1 lumbosacral x-ray for diagnostic clarity. Directing the central ray 5 cm anterior to the anterior superior iliac spine (ASIS) and 4 cm inferior to the iliac crest typically places it incorrectly in relation to the L5/S1 junction. For lateral views, the L5/S1 junction is generally located just above the level of the sacrum and slightly posterior to the ASIS. By positioning the central ray 5 cm anterior, it is more likely to project over structures that are too far forward in the pelvis, leading to the ray landing well anterior to the targeted L5/S1 region. This misalignment can cause anatomical structures to overlap on the x-ray, potentially obscuring important diagnostic details and making it challenging to assess the lumbosacral junction properly. Therefore, directing the central ray as described would indeed result in it being well anterior to the L5/S1 junction, causing the imaging outcome to be less effective for visualization of that important anatomical area. This positioning emphasizes the critical nature of accurate central ray placement for producing high-quality radiographic images.