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Autologous breast reconstructive surgery with deep inferior epigastric artery (DIEA) perforator flaps has become the mainstay for breast reconstructive surgery. CT angiography and three-dimensional image post processing can depict the number, size, course and location of the DIEA perforating arteries for the pre-operative selection of the best artery to use for the tissue flap. Knowledge of the location and selection of the optimal perforating artery shortens operative times and decreases patient morbidity.
Deep inferior epigastric artery perforator (DIEP) flap surgery for autologous breast reconstruction involves the transfer of the patient's own skin and subcutaneous tissues from the lower abdominal wall to the chest to form the breast mound. The advantage of the DIEP flap technique is that the operation spares the rectus muscle, which results in fewer complications and a faster return to normal activities .
The arterial supply to the lower abdominal wall is from the deep inferior epigastric artery (DIEA) and its perforator branches that pass through the rectus muscle to reach the subcutaneous fat and skin. Selecting the portion of the lower abdominal wall to use for the DIEP flap is based on the location, morphology and size of the perforating arteries present. Because the vascular anatomy of the abdominal wall varies greatly both between individuals and between the right and left abdomen within an individual, pre-operative imaging facilitates the surgical dissection by allowing the selection of the area of the lower abdominal wall with the best arterial supply to use for the breast reconstruction . CT angiography (CTA) with three-dimensional (3D) image reconstruction has been successfully implemented for the pre-operative planning of DIEP flap breast reconstructive surgery. Pre-operative availability of 3D reconstructed CT images improves operative outcomes and shortens operation times [3-5]. The objectives of this article are to review the arterial anatomy of the anterior abdominal wall, describe the features used to select a perforator artery for DIEP flap surgery and present a CT scanning and image post-processing protocol.
There are three general branching patterns of the DIEA: Type 1, a single vessel; Type 2, a bifurcated vessel; and Type 3, a trifurcated vessel (Figure 1). Knowing the branching pattern is important to select the vessel branch to include with the vascular pedicle of the DIEP flap. When several suitable perforators are present, depiction of the DIEA defines whether the suitable perforators emanate from and can be harvested with the same source vessel. Perforator origin is also important for predicting flap perfusion, as perforator arteries originating from a lateral DIEA branch may not provide flap perfusion across the midline.
The vascular pedicle of the harvested DIEP flap can be described as having five possible arterial segments (Figure 2):
Because the perforator size, position and relation to the rectus muscle predict the difficulty of the surgical dissection, demonstrating these features with imaging permits the pre-operative selection and localisation of the optimal perforator. There are five general types of DIEA perforating arteries:
The optimal perforator provides sufficient blood supply to the flap while minimising intramuscular dissection. The desired characteristics of the vascular pedicle for the tissue flap include a large calibre, a central perforator artery location in the flap and a short intramuscular course that is not near a tendinous intersection [6,7].
CTA is currently the preferred imaging modality for mapping the DIEA and its perforators. CT has better spatial resolution than MRI, and is more sensitive than ultrasound .
Our current protocol is based on a 64-channel platform: craniocaudal helical acquisition from the lesser femoral trochanter to 4 cm above the umbilicus, 0.625×40 mm collimation, pitch 1.375:1, and automatic tube current modulation. Tube potential is selected based on the scan field of view (SFOV) used for the patient: 120 kVp for an SFOV ≥34 cm, and 100 kVp for those <34 cm. Scan timing is achieved with a timing bolus at the level of the acetabulum (region of interest placed in an external iliac artery). The diagnostic scan is initiated at timing bolus peak +10 s after the administration of 100 ml of contrast injected at 5 ml s−1.
The objectives of image post processing are to create rendered and reformatted images that depict the DIEA branching pattern, the size and course of the perforators, and present the location of the perforators for the operative dissection . The post-processed images created at our institution include:
CTA with image post processing can be used to depict the branching pattern of the DIEAs and the location, size and course of their perforating arteries. Pre-operative CTA facilitates the selection and intra-operative localisation of the optimal perforator artery by the surgeon, which shortens operative times, improves outcomes and decreases patient morbidity.