Demonstration of the course of the posterior intercostal artery on CT angiography: relevance to interventional radiology procedures in the chest.

PURPOSE To document the course of the posterior intercostal artery (PIA) within the intercostal space (IS) in vivo using computed tomography angiography (CTA). MATERIALS AND METHODS A review of 428 IS from CTA of the chest was performed. Using multiplanar reconstruction (MPR) algorithms, the course of the PIA within the IS and the maximum distance of the PIA from the undersurface of the rib were determined in the 4th to 8th IS at three clinically relevant points: the posterior paravertebral area (PPV), angle of the rib (AR), and 25 mm lateral to the angle of the rib (LAR). Tortuosity of the vessels was graded from coronal three-dimensional images. RESULTS The mean maximum distances of the PIA within the IS from the undersurface of the rib were as follows: PPV, 7.2±0.512 mm (P = 0.0027); AR, 5.5±0.535 mm (P = 0.0487); and LAR, 2.3±0.366 mm (P = 0.0052). At the PPV, the PIA lies halfway between the two ribs within the IS and lies one third of the way from the undersurface of the rib at the AR and comes to lie within the subcostal groove toward the mid-axillary line. The tortuosity of the vessel was highly variable and was independent of both age and gender. CONCLUSION Considerable variability in vessel position was noted within the IS, with the PIA lying furthest from the undersurface of the rib in the PPV. To avoid injury, our data support the dictum "choose a site above the rib below," and additional caution should be taken to avoid the posterior paravertebral area.