Note: This copy is for your personal non-commercial use only. To order presentation-ready copies for distribution to your colleagues or clients, contact us at www.rsna.org/rsnarights. Abdominal Wall CT Angiography: HOWIDOIT Ⅲ A Detailed Account of a Newly Established Preoperative Imaging Technique1 Timothy J. Phillips, MBBS, GradDipSurgAnat Institutional review board approval was obtained for this REVIEWS AND COMMENTARY Damien L. Stella, MBBS, FRANZCR study, and all patients gave written informed consent. Warren M. Rozen, MBBS, BMedSci, Autologous surgical breast reconstruction with use of ab- PGDipSurgAnat dominal wall donor flaps based on the deep inferior epigas- Mark Ashton, MBBS, MD, FRACS tric artery (DIEA) and one or more of its anterior muscu- G. Ian Taylor, MBBS, MD, FRCS, FRACS, AO locutaneous perforating branches (DIEA perforator flap) is being used with increasing frequency instead of breast reconstruction with use of traditional transverse rectus abdominus musculocutaneous and modified muscle-spar- ing flaps. Preoperative mapping of the DIEA perforators with abdominal wall computed tomographic (CT) angiog- raphy may improve patient care by providing the surgeon with additional information that will lead to optimization of the surgical technique, shorter procedure time, and reduction in the frequency of surgical complications. The branching pat- terns of the DIEA, the segmental anatomy of the anterior adipocutaneous perforating branches of the DIEA, and the importance of these features in pre- and intraoperative surgical planning necessitate a different approach to ab- dominal wall CT angiography than that used with other abdominal CT angiographic techniques. In abdominal wall CT angiography, the common femoral artery is used as the bolus trigger, CT scanning is performed in the caudocra- nial direction, the automatic exposure control feature is disabled, a scaled grid overlay tool is used to present information to the surgeons, and radiation dose is mini- mized (average dose, 6 mSv). The anatomic accuracy of abdominal wall CT angiography has been investigated in cadaveric and surgical studies, with sensitivity of 96%– 100% and specificity of 95%–100%. This detailed descrip- tion will allow other radiologists and surgeons interested in free DIEP flap surgery to incorporate this useful tool into their practice. ௠ RSNA, 2008 Supplemental material: http://radiology.rsnajnls.org/cgi /content/full/249/1/32/DC1 1 From the Department of Radiology, the Royal Melbourne Hospital, Grattan Street, Parkville, Melbourne, Victoria 3050, Australia. Received November 26, 2007; revision requested January 15, 2008; revision received March 21; final version accepted April 3. Address correspondence to T.J.P. (e-mail: timothy.john.phillips@gmail .com ). ஽ RSNA, 2008 32 Radiology: Volume 249: Number 1—October 2008 HOW I DO IT: Abdominal Wall CT Angiography Phillips et al utologous surgical breast recon- (hereafter, perforators) are termed ested in abdominal wall CT angiography struction with abdominal wall do- DIEA perforator flaps, and they are be- with a step-by-step manual that de- Anor flaps has evolved since its in- ing used with increasing frequency to scribes our approach to this modality. troduction in the late 1970s and early replace the traditional transverse rectus Included are considerations regarding 1980s (1,2). Free flaps based on the abdominus musculocutaneous flaps and appropriate patient selection, contrast deep inferior epigastric artery (DIEA) the modified muscle-sparing flaps (3–6). material enhancement, image acquisi- and one or more of its anterior muscu- The DIEA perforator flap is used to har- tion and reconstruction parameters, im- locutaneous perforating branches vest fat and skin (adipocutaneous tis- age display and analysis techniques, and sue) without muscle and has resulted in the radiology report, which includes the fewer abdominal wall complications— presentation of data to the referring Essentials including hernia, bulge, and weakness surgeon. An explanation of the surgical Ⅲ We have detailed the use of radio- (3,7–10)—and shorter hospital stays, and radiologic anatomy of the DIEA and logic classification of the segmen- with a cheaper overall cost of treatment the characteristics that define favorable tal anatomy of the anterior mus- (11,12) when compared with alterna- perforators is also included. These rec- culocutaneous perforating tive surgical techniques. The superficial ommendations are based on the au- branches (hereafter, perforators) inferior epigastric artery can also be thors’ experience in performing and in- of the deep inferior epigastric ar- used for an adipocutaneous muscle- terpreting the results of 65 abdominal tery (DIEA) and the surgical rele- sparing flap, and it is the preferred sur- wall CT angiographic examinations and vance of this classification for free gical option for an abdominal wall free on close collaboration between the de- adipocutaneous flap harvest. flap, as it does not require incision of partments of radiology and plastic sur- Ⅲ We have developed a CT angiog- the anterior rectus sheath and thus has gery at our institution. raphy acquisition technique opti- minimal donor site morbidity (13,14). mized for imaging the DIEA and However, this vessel is not uniformly the anterior musculocutaneous present or of sufficient caliber to per- Anatomy branches (perforators) supplying form the operation. the abdominal wall. The branching pattern of the DIEA DIEA Classification Ⅲ We have described CT angiogra- and the location of its perforators vary, Cadaveric and surgical studies have phy postprocessing techniques and each patient’s anatomy dictates the been performed to classify the branch- optimized for display of the surgi- DIEA and perforator(s) on which the ing pattern of the DIEA. The branching cally relevant findings. flap will be based (15,16). Preoperative classification first described by Moon Ⅲ We have demonstrated a volume- Doppler ultrasonography (US) is useful and Taylor has been widely adopted and rendering color look-up table opti- when defining the DIEA branching pat- is shown in Figure 1 (15). In addition to mized for imaging of anterior tern; however, locating and choosing the major branching patterns (types I, musculocutaneous branches of the perforators was previously com- II, and III) of the DIEA above the arcu- the DIEA in the subcutaneous fat plete only after intraoperative abdomi- ate line, early branches also include a of the abdominal wall. nal wall dissection. Identification of op- pubic branch, muscular branches, and Ⅲ We have demonstrated a real- timal perforators on which to base the an umbilical branch (15). time volume-rendered image ma- flap is highly desirable. There is evi- Type I (single trunk) and type II (bi- nipulation reading technique that dence that flaps based on fewer perfora- furcation into two trunks) branching enables preoperative mapping of tors have a lower incidence of fat necro- patterns occur more commonly than DIEA perforators. sis (7). Harvesting a flap supplied by one does the type III pattern (division into Ⅲ Autologous breast reconstruction perforator requires the identification of more than two trunks). The other rele- with use of adipocutaneous free a perforator with optimal characteris- vant characteristics are the caliber of flaps (DIEA perforator flap) is the tics (discussed in detail later in this arti- the trunk(s) and any intramuscular optimal standard of care after cle). mastectomy. Abdominal wall computed tomo- Ⅲ Preoperatively mapping DIEA graphic (CT) angiography is a new tech- Published online perforators with this abdominal nique tailored to assist in locating and 10.1148/radiol.2483072054 wall CT angiography technique characterizing the perforators, with re- may improve patient care by pro- ported sensitivity and specificity of Radiology 2008; 249:32–44 viding the surgeon with additional 96%–100% and 95%–100%, respec- Abbreviations: information that leads to optimi- tively, in cadaveric and clinical studies CLUT ϭ color look-up table zation of the surgical technique, (17–23). In addition, this technique can DIEA ϭ deep inferior epigastric artery ϭ shorter operative time, and a re- be used to define the branching pattern MIP maximum intensity projection VRT ϭ volume-rendered technique duction in the frequency of opera- of the DIEA (18,23). The intent of this tive complications. article is to provide those who are inter- Authors stated no financial relationship to disclose. Radiology: Volume 249: Number 1—October 2008 33 HOW I DO IT: Abdominal Wall CT Angiography Phillips et al Figure 1 course. Usually, the DIEA enters the rectus sheath superficial to the arcuate line and courses superiorly between the posterior layer of the rectus sheath and the rectus muscle. It is not uncommon for one or both of the DIEAs to pene- trate and course within the rectus mus- cle for some part of their length (15,24,25). Segmental Arterial Anatomy of DIEA Perforators The descriptions and nomenclature ap- plied to the variations in perforator anatomy in cadaveric studies and surgi- cal observations are diverse, but the key findings are similar (24–26). The course a perforator takes from its origin at the DIEA through four anatomic spaces to Figure 1: Three-dimensional graphic illustrations show the classification of DIEA branching described by its end supply of the subcutaneous fat Moon and Taylor (15). Type I (single trunk) and type II (bifurcation into two trunks) branching are more com- and skin of the anterior abdominal mon than type III branching (division