LKnative - Intercostal block 
Intercostal artery (blue Doppler signal and red arrow), pleura (cyan arrows), innermost intercostal muscle (green asterix), internal intercostal muscle (red asterix), external intercostal muscle (cyan asterix), rib (r)
4 – Sonoanatomy: The intercostal nerves
The intercostal nerves are located between the innermost and the internal intercostal muscles
Typically the intercostal nerves are not visible with ultrasound. But the adjacent intercostal arteries and veins can be visualized with Color Doppler