With the long axis of the ultrasound probe held against the long axis of the spinal column, the probe is then moved along that axis to view the spinous processes and inter-vertebral spaces as though looking down at a picket fence as you move along its length.
To see a short video clip of a longitudinal scan of the lumbar and lower thoracic vertebrae with audio narration, click on the picture below.
The spinous processes produce characteristic shadows as they block the ultrasound energy, and then as the probe passes them and is over the intervertebral space the ultrasound energy “illuminates” the structures lying below. Note again at about 5 cms. in depth in the intervertebral space the appearance of the bright hyperechoic band of the ligamentum flavum.
Towards the end of the clip you can see the area below the ligamentum flavum illuminated showing the dark band of the thecal space and the distal bright band of the ventral dura.