There has been a move towards increasingly refined techniques for autologous breast reconstruction, and given the substantial inter-individual variability of perforator anatomy, the need for reliable, accurate methods of vascular imaging has been sought. Computed tomographic angiography (CTA) can offer a range of applications in autologous breast reconstruction to aid surgical planning and improved outcomes. This article explores the utility of CTA in imaging perforators, pedicles and recipient vessels across a wide range of flap types and donor sites. CTA has a range of clinical applications in autologous breast reconstruction, and can aid operative planning and improve outcomes.
The use of preoperative imaging for planning free flap operations has been enthusiastically received by most reconstructive surgeons, with advances in both operative techniques and imaging techniques highlighting the benefits of such imaging. Computed tomographic angiography (CTA) in particular, has emerged as a beneficial aid in the planning of perforator flaps, with proven efficacy in improving operative outcomes and allowing for accurate and appropriate preoperative decision making. Its role has emerged for many perforator flap operations, and many centers have now published large series of data to show these outcomes. In addition to modifying flap planning, preoperative imaging has been explored as a means to planning the optimal mode of dissection and to minimize donor site morbidity. With further technological improvements in imaging techniques, these aims have become increasingly realized.
In its role for preoperative planning, CTA is able to detect perforators at any potential donor site, and with modern high-resolution scanners allows for detection of almost all vessels more than 0.3 mm in size. This accuracy makes CTA the most accurate technology currently available for the preoperative mapping of perforators. In addition to this accuracy, CTA is able to evaluate more than 1 potential donor site simultaneously, allowing the surgeon flexibility in donor site selection as well as perforator selection within a single scan.
Perforator flap surgery is currently a mainstay in the management of breast reconstruction, with a range of donor sites commonly used for both partial and total breast reconstruction. Given the potential for overall improvements in both flap vascularity and survival, as well as donor site morbidity, a range of applications of CTA in the setting of autologous breast reconstruction have emerged. These applications include donor site selection, flap selection, and perforator selection for free tissue transfer, as well as flap and perforator selection for locoregional perforator flap options. Other applications for CTA that have become useful include the appraisal of recipient vessels for free tissue transfer and the screening for comorbidities, such as metastatic disease or incidental findings that may influence operative care. These and other useful techniques are explored in this article.
Technique
The process of scanning a patient to obtain images that can be used for preoperative planning is not complicated, and a range of scanning protocols can be used to achieve equally good visualization of perforators. In general, the aim is to achieve arterial phase scans, which eliminate venous contamination, avoid confusion between different structures, and maximize arterial filling. We thus recommend triggering the scan from the origin of the pedicle, and scanning in the direction of blood flow through the perforating vessels. For example, for deep inferior epigastric artery perforator (DIEP) flaps, the scan is triggered from the external iliac/common femoral artery junction and the scan is performed in a caudocranial direction. This technique is modified for each donor site.
Analysis of CTA images can similarly be performed using a range of techniques, with the raw scan data through axial slices able to show all of the important information; however, visual appreciation of the vascular anatomy is best achieved with the use of software-generated three-dimensional (3D) reconstructions. These reconstructions are easy to interpret by surgeons and show the anatomic relationships of each vessel in a single 3D image. There are a variety of software applications that are able to generate suitable images for operative planning. Each generated image can be saved for reference during the operation, with only several images required for easy intraoperative reference. Rather than referral to a radiologist for all image analysis, we have found that many surgeons prefer to see or generate the 3D reconstructions themselves, because appreciation of the 3D course of a perforator on a saved image can be difficult.
Free flap donor sites
Preoperative imaging of a donor site with CTA can achieve 2 global aims: first, to confirm that a proposed donor site is suitable in that role, and second, to select the most appropriate vasculature from that donor site as the basis of flap design. All potential donor sites for free flap breast reconstruction can be investigated with CTA to determine the exact nature of their vasculature. A variety of potential donor sites have been used for autologous breast reconstruction, with many of these still in widespread use; however, the anterior abdominal wall has remained the first choice because of the superior cosmesis of its donor site. Abdominal wall flaps used in this role include the free transverse rectus abdominis myocutaneous (TRAM) flap, muscle-sparing variants of the TRAM flap, the DIEP flap, and the superficial inferior epigastric artery (SIEA) flap. Although the abdominal wall is versatile and suitable in most cases, several other free flap donor sites are suitable as first-line or particularly where the abdominal wall is unsuitable (eg, if there is scarring). These sites include the superior and inferior gluteal artery perforator flaps (SGAPs and IGAPs, respectively) and the transverse upper gracilis (TUG) flap.
Anterior Abdominal Wall Flaps (TRAM, DIEP, and SIEA Flaps)
Free flaps based on the lower anterior abdominal wall integument have progressed in techniques in a donor-site–sparing fashion, which has simultaneously increased surgical complexity and decision making. From inclusion of all deep inferior epigastric artery (DIEA) perforators in the TRAM flap, to the selection of the optimal perforators in the DIEP flap, preoperative imaging can substantially improve decision-making ability. For the SIEA flap, where anatomic variation is widespread and a suitable SIEA is present in only 10% of patients, preoperative planning is of utmost importance. The abdominal wall vasculature is highly variable, potentially more than most other body regions. The DIEAs originate from the external iliac artery, and ascend within the rectus sheath on the deep surface of rectus abdominis, distributing musculocutaneous perforators to supply the overlying integument. Perforator variability is not only in location but also in size and course. The ability of this anatomy to cause operative havoc led to the use of the external Doppler prove for perforator mapping from the early days of such surgery. However, with low sensitivity and specificity in this role, the development of advanced perforator imaging technique arose in response to this uncertainty.
For perforator mapping in the anterior abdominal wall, CTA has become established as the gold standard, shown to be highly accurate in both cadaveric and clinical studies, with a sensitivity and specificity in such mapping approaching 100%. It has been shown to accurately identify the DIEA ( Fig. 1 ), all of its major branches, and its musculocutaneous perforating branches. In addition to the location and size of these vessels, a 3D appreciation of the course of the perforators can be shown ( Fig. 2 ). The relative dominance of the superficial arterial system can also be determined ( Fig. 3 ). The use of CTA to show this anatomy can directly aid selection of the hemiabdominal wall of choice for dissection, the approximate volume of tissue supplied per perforator, and the perforators of choice for supply to the flap. CTA has been compared with other modalities such as color duplex (ecocolor Doppler) ultrasonography and magnetic resonance angiography (MRA), with superior results in such studies. Furthermore, improvements in outcomes have been shown with statistical significance, with faster dissection times and reduced operating times, improved flap vascularity and survival, and improved donor site morbidity all shown. These benefits have propelled CTA into increasingly widespread use. A wealth of information is gained from an abdominal wall CTA that contributes to the superior advantage of this modality. Not only does an abdominal wall CTA show the DIEA and its branches, but it also shows other vessels supplying the abdominal wall, including the SIEA, superficial superior epigastric artery, deep superior epigastric artery, deep circumflex iliac artery, superficial circumflex iliac artery, intercostal arteries (lateral and posterior), and lumbar arteries. The SGA and IGA are also shown within the same scan range, offering consideration of alternative donor site options. In addition to the vasculature (which can rarely show abdominal wall perforators coming from a direct intra-abdominal source vessel), the soft tissues and fascial layers of the abdominal wall and the abdominal contents are also included within the scan data. The use of all of this information can directly assist and change operative planning.
There are significant differences in scanning protocols between abdominal wall perforator CTA and routine abdominal CTA. Without these changes, perforators are not adequately imaged and scans are unlikely to be suitable or worthwhile. Our usual protocol requires adequate positioning of the patient (to match the supine operative position) without compressive clothing, and scanning the range of the flap only (pubic symphysis to 4 cm above the umbilicus). We scan at the level of the common femoral artery and trigger the scan when it opacifies to greater than 100 Hounsfield units (HU), scanning the patient in the caudocranial direction (to match filling of the DIEA).
GAP Flaps
The gluteal region provides a highly advantageous donor site for autologous breast reconstruction, with good available flap volume and reliable vasculature. Just as CTA is helpful for perforator imaging in the abdominal wall, so too can it show the vasculature of the gluteal region. CTA can allow for choice of the optimal flap and donor vessel (SGA vs IGA); choice of the optimal perforator within that flap; optimization of flap design and orientation to create a more aesthetic scar position. Often SGAP and IGAP flaps are planned with the use of multiple perforators, and CTA can select those perforators that can minimize muscle sacrifice between selected perforators.
CTA can show the entire course of the donor vasculature, from regional source to skin ( Figs. 4 and 5 ). The SGA is the largest branch of the internal iliac artery, originating as the continuation of the posterior division of that vessel. It passes out of the pelvis through the greater sciatic foramen and divides almost immediately into deep and superficial branches. The superficial branch enters the gluteus maximus on its deep surface, and often divides several times within this muscle, sending multiple perforators to supply the skin over the gluteus maximus and the sacrum. The angiosome extends well beyond the edge of the gluteus maximus, and most prefer taking a more lateral flap to gain extra perforator length. The branching pattern of the SGA within the gluteus maximus is extremely variable, and can make it difficult to raise the flap on more than 1 perforator if the anatomy is not known before surgery. Previously, some investigators advocated a single perforator for the flap, with additional perforators selected if favorable anatomy was discovered intraoperatively. It has been our experience that CTA almost always allows for multiple perforators to be selected if wanted, and for those perforators to be traced on imaging to their source (virtual surgery), ensuring that they originate from the same pedicle.
The IGA arises as one of the terminal branches of the anterior division of the internal iliac artery. It also passes through the greater sciatic foramen to exit the pelvis, although unlike the SGA, it runs inferior to the piriformis. Although its main course is to descend in the interval between the greater trochanter and the ischial tuberosity, it sends a few perforating branches to supply the inferior portion of the gluteus maximus and the overlying skin, a zone of supply just inferior to the primary angiosome of the SGA. The intramuscular dissection of these perforators is difficult, and preoperative awareness gained by CTA can be indispensable in selecting those with shorter intramuscular and partially septocutaneous courses.
The standard scan used to assess DIEA perforators can be used to visualize the SGAP and IGAP; however, our experience has identified that several key modifications can substantially improve the scan quality. First, triggering the scan at the source pedicle (the internal iliac artery) maximizes arterial filling of the gluteal artery perforators. In addition, these scans are performed in the prone position, to avoid pressure distortion of the gluteal soft-tissue and vascular anatomy.
TUG Flaps
The TUG flap has emerged as another useful donor site, and in some centers this flap has become the standard. The TUG flap is a free flap usually consisting of a segment of the proximal gracilis muscle and up to a 25-cm × 10-cm skin paddle oriented transversely (although a vertical paddle has been used too). The vascular pedicle of the TUG flap is the descending branch of the medial circumflex femoral artery, generally with 2 venae comitantes, yielding a pedicle about 6 cm long. This flap may also be raised as a perforator flap if the anatomy is favorable. This flap is favored by some because of its reported low donor site morbidity.
Imaging with CTA can clearly show the source vasculature and perforator anatomy ( Fig. 6 ). This characteristic can enable accurate flap planning and design of the skin paddle and aid in consideration of muscle-sparing procedures. The scanning technique for this flap (or any limb perforator flap) is simple: we place the patient in the position in which the flap will be raised, trigger the scan from the origin of the source vessel (common femoral artery), and scan in a proximal-distal direction. The gracilis muscle can clearly be shown on imaging, and perforators (either septocutaneous or musculocutaneous) through or around the muscle can be highlighted. The intraflap course of the perforators delineated on CTA has also confirmed the clinical and surgical findings that the major orientation/direction of the gracilis perforators (ie, their angiosome) is a transverse skin paddle as opposed to the vertical skin paddle described earlier.
Lumbar Artery Perforator Flaps
Although not a common candidate as a donor site for reconstruction, the lumbar region does offer a potential donor site for breast reconstruction, and lumbar artery perforators have been used in this role. Lumbar perforating arteries segmentally supply the lumbar skin, usually as fasciocutaneous perforators between the erector spinae and quadratus lumborum muscles. Each lumbar segment has its own artery, with the size of the vessels increasing inferiorly. To obtain a reasonable pedicle length for breast reconstruction deep dissection between erector spinae and quadratus lumborum is required.
The size and distribution of lumbar artery perforators have been studied with cadaveric angiographic techniques, and CTA has been used previously to determine the vascular anatomy of a particular patient to help improve the selection of pedicles and flap design.
Free flap donor sites
Preoperative imaging of a donor site with CTA can achieve 2 global aims: first, to confirm that a proposed donor site is suitable in that role, and second, to select the most appropriate vasculature from that donor site as the basis of flap design. All potential donor sites for free flap breast reconstruction can be investigated with CTA to determine the exact nature of their vasculature. A variety of potential donor sites have been used for autologous breast reconstruction, with many of these still in widespread use; however, the anterior abdominal wall has remained the first choice because of the superior cosmesis of its donor site. Abdominal wall flaps used in this role include the free transverse rectus abdominis myocutaneous (TRAM) flap, muscle-sparing variants of the TRAM flap, the DIEP flap, and the superficial inferior epigastric artery (SIEA) flap. Although the abdominal wall is versatile and suitable in most cases, several other free flap donor sites are suitable as first-line or particularly where the abdominal wall is unsuitable (eg, if there is scarring). These sites include the superior and inferior gluteal artery perforator flaps (SGAPs and IGAPs, respectively) and the transverse upper gracilis (TUG) flap.
Anterior Abdominal Wall Flaps (TRAM, DIEP, and SIEA Flaps)
Free flaps based on the lower anterior abdominal wall integument have progressed in techniques in a donor-site–sparing fashion, which has simultaneously increased surgical complexity and decision making. From inclusion of all deep inferior epigastric artery (DIEA) perforators in the TRAM flap, to the selection of the optimal perforators in the DIEP flap, preoperative imaging can substantially improve decision-making ability. For the SIEA flap, where anatomic variation is widespread and a suitable SIEA is present in only 10% of patients, preoperative planning is of utmost importance. The abdominal wall vasculature is highly variable, potentially more than most other body regions. The DIEAs originate from the external iliac artery, and ascend within the rectus sheath on the deep surface of rectus abdominis, distributing musculocutaneous perforators to supply the overlying integument. Perforator variability is not only in location but also in size and course. The ability of this anatomy to cause operative havoc led to the use of the external Doppler prove for perforator mapping from the early days of such surgery. However, with low sensitivity and specificity in this role, the development of advanced perforator imaging technique arose in response to this uncertainty.
For perforator mapping in the anterior abdominal wall, CTA has become established as the gold standard, shown to be highly accurate in both cadaveric and clinical studies, with a sensitivity and specificity in such mapping approaching 100%. It has been shown to accurately identify the DIEA ( Fig. 1 ), all of its major branches, and its musculocutaneous perforating branches. In addition to the location and size of these vessels, a 3D appreciation of the course of the perforators can be shown ( Fig. 2 ). The relative dominance of the superficial arterial system can also be determined ( Fig. 3 ). The use of CTA to show this anatomy can directly aid selection of the hemiabdominal wall of choice for dissection, the approximate volume of tissue supplied per perforator, and the perforators of choice for supply to the flap. CTA has been compared with other modalities such as color duplex (ecocolor Doppler) ultrasonography and magnetic resonance angiography (MRA), with superior results in such studies. Furthermore, improvements in outcomes have been shown with statistical significance, with faster dissection times and reduced operating times, improved flap vascularity and survival, and improved donor site morbidity all shown. These benefits have propelled CTA into increasingly widespread use. A wealth of information is gained from an abdominal wall CTA that contributes to the superior advantage of this modality. Not only does an abdominal wall CTA show the DIEA and its branches, but it also shows other vessels supplying the abdominal wall, including the SIEA, superficial superior epigastric artery, deep superior epigastric artery, deep circumflex iliac artery, superficial circumflex iliac artery, intercostal arteries (lateral and posterior), and lumbar arteries. The SGA and IGA are also shown within the same scan range, offering consideration of alternative donor site options. In addition to the vasculature (which can rarely show abdominal wall perforators coming from a direct intra-abdominal source vessel), the soft tissues and fascial layers of the abdominal wall and the abdominal contents are also included within the scan data. The use of all of this information can directly assist and change operative planning.
Related posts:
Assessing Perforator Architecture
Acoustic Doppler Sonography, Color Duplex Ultrasound, and Laser Doppler Flowmetry as Tools for Successful Autologous Breast Reconstruction
Maximizing the Use of the Handheld Doppler in Autologous Breast Reconstruction
Noncontrast Magnetic Resonance Imaging for Preoperative Perforator Mapping
Fluorescent Angiography
Near-Infrared Spectroscopy in Autologous Breast Reconstruction
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