Background: The internal mammary artery perforator flap has been used in head and neck reconstruction. Although anatomical and perfusion studies with ink have been performed previously, the authors now use three- and four-dimensional computed tomographic angiography to precisely visualize vascular anatomy of individual perforators (perforasomes) and the axiality of perfusion. Methods: Eleven hemichest adipocutaneous flaps were dissected from cadavers. Measurements were recorded, such as the distance of each internal mammary artery perforator from the sternal edge, diameter of vessels, and number and location of internal mammary artery perforators per hemichest. Single internal mammary artery perforator injections with Isovue contrast were carried out, and the flaps were subjected to dynamic computed tomographic scanning. Static computed tomographic scanning was also undertaken using a barium-gelatin mixture. Images were viewed using both General Electric and TeraRecon systems, allowing the appreciation of vascular territory (three-dimensional), and analysis of perfusion flow (four-dimensional). Results: Each hemichest flap had one to three internal mammary artery perforators, most commonly in intercostal spaces 1, 2, and 3. Twenty-six internal mammary artery perforators were dissected, and 19 perforator arteries and six perforator veins were injected with contrast. The internal mammary artery perforator in the second intercostal space had the largest mean diameter and a large vascular territory. Linking vessels, both direct and indirect, communicate between perforators and can enlarge perforasomes. Linking vessels were also found between internal mammary artery perforators and the lateral thoracic artery. Conclusions: Three- and four-dimensional computed tomographic angiography allows detailed analysis of vascular anatomy. Important information such as internal mammary artery perforator flap dimensions, linking vessels, and axiality of perfusion is elucidated, thus contributing to a better understanding of perforator flaps.