Three- and four-dimensional computed tomographic angiography and venography for imaging of the microvascular anatomy of perforator flaps

Two-dimensional (2D) contrast radiography utilising the intravascular injection of lead oxide or barium sulphate mixtures is the current gold-standard for investigating the vascular anatomy of surgical flaps. The vascular anatomies of surgical flaps, however, are three-dimensional (3D), and their evaluation is conceptually limited by evaluation in 2D. Static 3D computed tomographic (CT) angiography enables vascular anatomy to be evaluated in the coronal, axial, and sagittal plane, and dynamic fourdimensional (4D) CT angiography (CTA) allows the vascular filling of a surgical flap to be visualized over short time intervals in three dimensions. These methods are also capable of elucidating the vascular anatomy and perfusion of the integument in general. The tissues of the body are perfused by source arteries in 3D blocks. The perforating vessels that provide blood supply to the skin may be dissected from between or through the underlying muscle, and flaps based on these vessels are termed perforator flaps. These flaps have the advantages of reduced donor site morbidity due to preservation of the underlying muscle, versatility to accurately replace the components required at the recipient site, and freedom from orientation of the pedicle. Their development has followed our understanding of the blood supply from a source artery to the skin, which has been achieved due to landmark studies by Manchot, Salmon, Cormack and Lamberty, Taylor, and others. Many articles now attest to the safety and reliability of perforator flaps. The arterial and venous anatomies of the workhorse perforator flaps, which include the anterolateral thigh (LCFAP-v/), the thoracodorsal artery perforator (TAP), and deep inferior epigastric artery perforator (DIEAP) flaps, remain poorly understood, and better understanding may improve the reliability of these flaps, aid in optimal flap design with regards to the vascular anatomy, and may aid in the development of new perforator flapsTo elucidate the 3D and 4D arterial and venous anatomies and perfusion of perforator flaps, this thesis studied the vascular anatomies of the workhorse perforator regions in fresh adult cadavers acquired through the Willed Body Program at the University of Texas Southwestern Medical Center in Dallas using novel 3D imaging techniques. These regions included the thigh, the abdomen, and the back. The techniques consisted of cannulation of the vessels at the level of perforators and their accompanying venae comitantes, followed by either injection of a lead oxide or barium sulphate and gelatin mixture, or by iodinated CT contrast medium injected using a precision pump prior to acquisition of CT images and three-dimensional volume-rendered reconstructions. CT contrast medium has a viscosity similar to that of blood and enabled better physiological modelling of perforator flap perfusion than had been achievable previously.In conclusion this thesis studied novel techniques for acquiring both static and dynamic three-dimensional images of microvascular perforator flap anatomy using CTA and venography (CTV). The information gained has provided a better understanding of how perforator flaps and the integument in general are perfused