Which vertebra is positioned at the top of the lumbar spine in DXA imaging?

• A. L1
• B. L2
• C. L3
• D. L4

Answer: (A)

The vertebra positioned at the top of the lumbar spine in Dual-energy X-ray Absorptiometry (DXA) imaging is L1. This is significant because in bone densitometry, particularly when assessing the lumbar spine for osteoporosis or other conditions, L1 serves as the starting reference point for the lumbar spine region.

The lumbar spine consists of five vertebrae (L1 to L5), and the L1 vertebra is the first one in this sequence. In normal evaluation practices, L1 is included in the analysis of bone mineral density (BMD) along with L2, L3, L4, and sometimes L5, but L1 is always at the top of that range. Additionally, accurate localization of L1 is critical, as any error in identifying the correct vertebra can impact BMD measurements and ultimately affect the diagnosis and treatment of conditions like osteoporosis. Understanding the anatomy and position of L1 sets the foundation for interpreting DXA results correctly.