Brief reminder of different types of breast reconstruction, specifying the particular features of the so-called DIEP adipocutaneous flap.

Transcription

1 Analysis of deep inferior epigastric artery perforating vessels with CT angiography before autologous breast reconstruction. Optimal technique, anatomy and key preoperative imaging findings Poster No.: C-2287 Congress: ECR 2013 Type: Educational Exhibit Authors: J. A. Herrero Lara, C. Caparrós Escudero, D. de Araujo Martins Romeo, R. M. Lepe Vázquez; Sevilla/ES Keywords: CT-Angiography, Vascular, Anatomy, Abdomen DOI: /ecr2013/C-2287 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 21

2 Learning objectives Brief reminder of different types of breast reconstruction, specifying the particular features of the so-called DIEP adipocutaneous flap. CT angiography acquisition technique optimized for imaging the DIEA and the perforator branches. CT angiography postprocessing techniques optimized for display of the surgically relevant findings. To determine the properties of an ideal perforator. Page 2 of 21

3 Background 1) Introduction. Mastectomy is a surgical procedure with associated functional deficits, such as further inability to breastfeed and loss of sensivity on the skin of the area. It is also accompanied by psychosocial effects, which are probably the most important consequences for women undergoing this procedure. These include anxiety, depression and negative effects of their body perception and sexuality, derived from physical and aesthetic deformity. Several studies suggest that breast reconstruction restores body perception, improving vitality, femininity and sexuality of the patients and has satisfactory repercussions on their well-being and quality of life. Breast reconstruction is divided in two stages: breast volume restoration and reconstruction of the areola-nipple complex. Breast volume restoration is achieved by implants or autogenous tissue. Among the advantages of the second option we can find durability and long term cosmetic effects. Multiple factors are involved in the election of the technique, as well as the size and shape of the original breast, the location and type of tumor, the viability of surrounding tissue and other locations (probable donor areas), the age of the patient, possible medical risk factors and the type of adjuvant therapy. In any case, the patient's choice is assessed as a decisive factor. Breast volume restoration using tissue from the own patient includes several basic locations for the donor flap, such as the abdomen, back, buttocks and thighs. In all cases we use skin, fat and, in some occasions, muscle. They are transferred including a vascular pedicle or as free flap wich requires microvascular anastomosis of the blood vessels. The most common pedicled myocutaneous flap is the transverse rectus abdominis myocutaneous, TRAM flap, perfused by the superior epigastric vessels. Among free flaps, this is without pedicles, myocutaneous tissue is used including infraumbilical rectus abdominis, in the subsidiary area of the inferior epigastric vessels (free TRAM flap). A procedure which is at its peak also uses this location as the donor area, but only using skin and fat, flap based on one or two perforators that pass from the Page 3 of 21

4 inferior epigastric bessels through the rectus abdominis muscle into the fat and skin. This is known as the DIEP flap (deep inferior epigastric perforator). The DIEP flap doesn't employ muscle tissue (only adipocutaneous tissue) and is associated to a fewer abdominal wall complications (including hernias, protrusions or weakness), shorter hospital stays and it reduces the overall cost of treatment. A less harmful method would be employing tissue irrigated by the superficial inferior epigastric artery, it does not requires incision of the anterior rectus sheat, so the donor site morbidity is minimal. However, these vessels are less constant and, if present, their caliber is insufficient in many occasions. The branching pattern of the deep inferior epigastric artery (DIEA) and the location of its perforators have a high variability, mainly influenced by each patient s anatomy, that is going to dictate the DIEA and perforator/s on wich the flap will based. Doppler ultrasound is used as a preoperative technique to define the branching pattern of DIEA, although the identification of the ideal perforant is only possible after complete surgical dissection. There is evidence that a flap based on fewer perforator branches presents a lower risk of fat necrosis, thus the identification of an optimal perforator prior to tissue election is essential. CTA of the abdominal Wall is a technique able to characterize perforants, with a sensitivity and specificity around % and %, respectively, data based on clinical studies and autopsies. Additionally, this technique also defines the branching pattern of the DIEA. In conclusion, it provides with information that enables optimization of the surgical procedure as well as reducing its duration, improving the prognosis of breast reconstruction. 2) Anatomical reminder Branching pattern. The deep inferior epigastric artery originates in the medial margin of the distal external iliac artery following a cranial trajectory passing through the posterior layer of the sheath of the rectus right under the arcuate line. It further locates on the posterior layer of the Page 4 of 21

5 rectus and the rectus abdominis muscle. However, it is usual that one or both DIEP arteries penetrate and present an intramuscular course in some segment of its route. The pattern of ramification of the DIEA was first described by Moon and Taylor and is widely accepted. It includes three main types. Types I (one branch) and II (bifurcation in two branches) are more frequent than type III (division in more than two branches) (figure 1). In addition to the major branching patterns, there are also early branches: pubic, muscular and umbilical branches Segmental anatomy of DIEA perforators. The trajectory of the perforators from its origin at the DIEA between the posterior layer of the rectus sheat and the rectus muscle until they reach the subcutaneous cellular tissue and the skin is divided in several segments (figura 2). DIEA is located between the posterior layer of the sheath of the rectus and the posterior margin of the rectus abdominis muscle. Perforators originate from this point and pass through the posterior margin of the muscle adopting an initial intramuscular trajectory. This segment may be absent if the perforator coincides with a musculotendinous intersection in its way out. After going through the anterior margin of the rectus abdominis, the perforant branch is usually located between this space and the anterior layer of the rectal sheath, known as the subfascial segment. This segment is absent sometimes, when the trajectory of the perforant branch crosses simultaneously the anterior muscle edge and the anterior layer of the rectal sheath. The next segment after passing through the rectal sheath is the subcutaneous segment, with a variable extension and several anastomoses with branches of the superficial inferior epigastric artery. Perforators branches originating from the DIEA with type II or III ramification are known as medial and lateral branches. Perforators with a subfascial/subcutaneous trajectory originated in the closeness of the umbilicus are known by some authors as paraumbilical or paramedian perforators Additional useful characteristics for surgeons (Figura 3). Page 5 of 21

6 Anatomical data of the perforators obtained by CT angiography are used to determine the surgeon s choice of an ideal perforator (which will serve as the base for the flap) and it influences surgical planning and technique. There is evidence that a flap based on few perforator branches shows less risk of fat necrosis. A perforator branch with a long subcutaneous segment and a caliper #1 mm of diameter irrigates a considerable volume of skin and subcutaneous cellular tissue. In cases in which the perforator shows long subfascial or intramuscular trajectories, this must be indicated as both require a wide and careful dissection. This is not a desirable procedure as it increases the morbidity of the abdominal wall. Those perforators which origins coincide with a musculotendinous intersection are preferred by many surgeons as they usually present short or even absent intramuscular or subfascial segments. Types I and II ramifications are not only more frequent but they also present shorter intramuscular trajectories than those originated from a type III pattern. As mentioned, perforators derived from DIEA with a type II or III bifurcation can be classified as medial or lateral according to their location. Taken into account that the rectus abdominis muscles are innervated laterally it is easy to understand that a more medial perforator means that disecction through the rectus muscle is less likely to denervate the muscle that receives its nerve supply laterally. Denervation is an important complication as it aborts the main advantage of the DIEP flap technique, not preserving the muscles. Medial branches can also be used, but lateral ones must be conserved. 3) Patient selection. Most patients that have undergone a mastectomy due to breast cancer are candidates for DIEP flap reconstruction. This technique can be additionally used in patients with congenital or post-surgical breast defects as well as in breast augmentation surgery. Among absolute contraindications there are previous abdominoplasty, liposuction precedents or active smoking (counting the last month prior to surgery). Among relative contraindications, there is the presence of previous large cross-section or oblique incisions, especially in postapendectomy cases as the DIEP pedicle has been shown to be affected. Page 6 of 21

7 If the patient is under radiotherapy, it is preferable to be finished before surgery. Although the DIEP flap may tolerate the effects of radiotherapy, better long-term results have been shown in subsequent surgeries. If we consider CT angiography specific indications, a previous anaphylactic reaction to intravenous iodinated contrast material is an absolute contraindication. Nephropathies with a compromised renal function may also exclude the use of intravenous iodinated contrast material. Page 7 of 21

8 Images for this section: Fig. 1: MIP coronal reconstruction. DIEA, type I (single trunk, right), and type II (bifurcation into two trunks, left) branching pattern. Radiodiagnóstico, Hospital Universitario Virgen Macarena - Sevilla/ES Page 8 of 21

9 Fig. 2: MIP axial reconstruction. Segmental arterial anatomy of DIEA perforators. Intramuscular, subfascial and subcutaneous segments. Radiodiagnóstico, Hospital Universitario Virgen Macarena - Sevilla/ES Page 9 of 21

10 Fig. 3 Phillips TJ, Stella DL. Department of Radiology, Royal Melbourne Hospital, Melbourne, Australia. Page 10 of 21

11 Imaging findings OR Procedure details 1) Abdominal Wall CT angiography. Image acquisition. As in any CT angiography exam including intravenous iodinated contrast material, a previous creatinine measurement must be realized, the patient must be fasting at least 4 hours before and the written informed consent is obtained from all patients. The patient, with all undergarments removed, is posicioned supine on the CT table. The upper limit of the acquisition volume was established 3-4 cms. above the umbilicus. The inferior limit must allow the exit of the superficial inferior epigastric artery from the common femoral artery using the lessers trochanters as an anatomical reference. Oral contrast preparations mustn't be done. 100 ml. of an intravenous, low-osmolar, noionic iodinated hignh concentration ( mg/ml) contrast agent is administered, followed by 50 ml of saline bolus flash, both at a rate of 4 ml/sc. Using high concentrations (>350 ml/sc) allows the identification of tiny perforators, particulary intramuscular segments. As an alternative, we can use an iodinated contrast material with a 300 mg/ml concentration at an administration rate of 5 ml/sc. Unique injection is posibble, 150 ml of iodinated contrast, with a concentration of 270 mg/ ml at a 4 cm/sc rate, without saline solution, which is a useful alternative, especially if there isn't a double-head injection system available. To optimize artery enhancement with time of acquisition, we employed the bolus tracking technique, with the ROI (region of interest) in the common femoral artery, due to the caudocranial trajectory of the assessed vessels, thus equally conditioning that the acquisition is also done in a caudocranial direction. The exact time at which acquisition starts may be automatically programmed (over 100 U.H.) or manually. Contiguos isometric acquisition data obtained with thin-colimation helical CT are ideal for quality CT angiography. Page 11 of 21

12 All parameters must be well adjusted in order to obtain high-quality images that enable a precise diagnosis with the lowest radiation, following the ALARA (as low as reasonably achievable) principle. Use of 120 KV tube voltage and mas tube current results in high-quality images and accetable effective dose estimates for the limited scanning range of abdominal wall CT angiography. In the summary table we include the image acquisitionparameters proposed for equipments with 16 and 64 detectors (figure 4). 2) Abdominal Wall CTA. Image processing techniques. MIP reconstruction (maximum intensity projection) can be used in an axial plane to confirm intramuscular and subcutaneous segments of the perforators. Thus, the perforator with the best characteristics (following those previously mentioned) are chosen: larger caliper, less intramuscular trajectory and preferentially locate in a medial/ periumbilical location (figure 2). Among the subfascial segment assessment, we studied the anastomosis with branches from the superficial inferior epigastric artery. The presence of muscle fat infiltration, diastases or hernias must also be studied. The branching pattern of both DIEA was subsequently determined by using a MIP reconstruction in a coronal section. The width of the reconstruction must be adjusted at the work station in order to eliminate anterior (skin) or posterior structures (mesenteric and omental arteries and other highlighted structures such as bowel walls) as they could cover the area of interest (figure 5). Moreover, in order to confirm the branching pattern and to distinguish the ramifications of the prominent perforators, we will make use of the axial and sagittal sections (figure 6). Considering the umbilicus as a central reference position, the exact location and the course of the perforator arterial branches and the point where the subcutaneous segment originates are marked on the cutaneous surface of a 3D VR (volume rendering) reconstruction (figure 7). A scaled grid can be applied to the image with the center point at the umbilicus (figure 8). These reconstructions must be stored in the PACS. The detailed description will allow surgeons to improve their practice. Page 12 of 21

13 In addition to these techniques, during the postprocessing using VR reconstruction, we can use the color look-up table (CLUT) software, with is used to assign voxel color and opacity on the basis of CT numbers. The aim is to easily differentiate between areas, based on the fact that abrupt color changes are more noticeable than changes in intensity. For this purpose, a color is arbitrarily fixed for a specific intensity in an initially monochromatic image. Another possibility of postprocessing that may be useful is to provide with the simultaneous location of each perforator on axial, coronal and sagittal sections by a multiplane reconstruction (MPR) using an axis-based system, and in a coronal VR reconstruction in which the umbilicus has been previously marked. Therefore, we obtain an exact location in all sections with descriptive information for the surgeon and additionally providing the specific characteristics of each perforator. Page 13 of 21

14 Images for this section: Fig. 4: MIP coronal reconstruction. Enhancement of the intestinal walls and their support vessels (black arrow) causing a worse definition of the right DIEA branching pattern (type II) than the left side (type I). Radiodiagnóstico, Hospital Universitario Virgen Macarena - Sevilla/ES Page 14 of 21

15 Fig. 5: MIP coronal (right) and sagital (left) reconstructions. Left DIEA with type II branching pattern. Although right branch may have similarities in their morphology, it corresponds to a type I pattern with a lateral perforator branch of considerable caliber (black arrow), which was confirmed in the sagittal plane valuation. Origin of both epigastric arteries from distal external iliac (thick black arrows). It marks the umbilicus as anatomical reference. Radiodiagnóstico, Hospital Universitario Virgen Macarena - Sevilla/ES Page 15 of 21

16 Fig. 6: VR reconstruction. Arrows indicate the point where the subcutaneal segment originates in each perforator. Radiodiagnóstico, Hospital Universitario Virgen Macarena - Sevilla/ES Page 16 of 21

17 Fig. 7: VR reconstruction similar than fg.6. A scaled grid has been applied, to calculate the distance between the origins of sucutaneal segment of each perforator and the umbilicus. Radiodiagnóstico, Hospital Universitario Virgen Macarena - Sevilla/ES Page 17 of 21

18 Fig. 8: VR and coronal, sagital and axial reconstructions. A scaled coordinate system has been applied with the center point in the origin of the subcutaneal segment of each perforator. Radiodiagnóstico, Hospital Universitario Virgen Macarena - Sevilla/ES Page 18 of 21

19 Conclusion Abdominal Wall CT angiography is a valuable tool in presurgical assessment of breast reconstruction with a DIEP flap due to its capacity of defining the anatomy of the deep inferior epigastric artery and its perforator branches, providing information that optimizes the preoperative planning and improve the prognosis. A correct performance requires specific acquisition and postprocessing techniques. There are some relevant characteristics of the perforator branches with a special relevance for the surgeon, and they must be known and highlighted on the radiological report. Page 19 of 21

20 References 1. Karunanithy N, Rose V, Lim A, et al. CT angiography of inferior epigastric and gluteal perforating arteries before free flap breast reconstruction. Radiographycs 2011; 31: Cordeiro PG. Breast Reconstruction after Surgery for Breast Cancer. N Engl J Med 2008;359: Phillips TJ, Stella DL, Rozen WM, et al. Abdominal wall CT angiography: a detailed account of a newly established preoperative imaging technique. Radiology 2008;249: Nahabedian MY. Secondary Operations of the Anterior Abdominal Wall following Microvascular Breast Reconstruction with the TRAM and DIEP Flaps. Plast Reconst Sur : Trehaskiss AP, Goodwin AN, Acland RD. The Cutaneous Arteries of the Anterior Abdominal Wall: A Three-Dimensional Study. Plast Reconst Sur 2007; 120: Alonso A, Garcia E, Bastarrika G, et al. Preoperative planning of deep inferior epigastric artery perforator flap reconstruction with multislice-ct angiography: Imaging findings and inicial experience. J Plast Reconstr Aesthet Surg 2006; 59: Smit J, Dimopoulo A, Liis A, et al. Preoperative CT angiography reduces surgery time in perforator flap reconstruction. J Plast Reconstr Aesthet Surg 2009; 62: Granzow JW, Levine JL, Chiu ES, et al. Breast reconstruction with the deep inferior epigastric perforator flap: History and an update on current technique. J Plast Reconstr Aesthet Surg 2006; 59: Castro J, García E, Alonso, A. Análisis de perforantes de la epigástrica inferior profunda con Angio TC 3D, Eco Doppler color y Doppler simple de ultrasonidos en colgajo DIEP: resultados preliminares. Cir Plast Iberolatinoam 2008; 34: Gagnon AR, Blondeel PN. Colgajos de perforantes de las arterias epigástricas inferiores profunda y superficial. Cir Plas Iberolatinoam 2006; 32: Page 20 of 21

21 Personal Information Juan Antonio Herrero Lara. U.G.C. de Radiodiagnóstico. Hospital Universitario Virgen Macarena. Sevilla, España. Page 21 of 21