Authors’ reply to George and Gupta et al.

We appreciate and thank the readers for their interest in our article, “Role of computed tomography angiography in deep inferior epigastric perforator flap breast reconstruction surgery: A retrospective observational study.”[1] In this letter, we provide our responses to the queries raised by Gupta et al. and George.[2,3] The acquisition of computed tomography angiography (CTA) to map the deep inferior epigastric perforator can be made at the time of staging or re-staging post-neoadjuvant chemotherapy, reducing the need for an additional scan and saving the cost, radiation exposure, and contrast requirement. The amount of radiation exposure can be reduced as low as 6 mSv using an appropriate dose-adapted protocol which is comparable to a standard CT examination of the pelvis.[4] A study by Niumsawatt et al.[5] showed that a radiation reduction of 60% is attainable in CTA techniques with the use of adaptive statistical iterative reconstruction (ASIR) technology without sacrificing image quality. The acquisition time for CTA is under 30 seconds, and the whole CTA process takes about 5-7 minutes which is faster than magnetic resonance angiography (MRA), which takes about 30-40 minutes.[6] The cost for an additional angiographic phase is not usually added, especially in government setups; however, private centers can have an additional cost for the post-processing data. Allergic reactions occur in about 0.1-0.6% of patients exposed to modern non-ionic low-osmolar contrast agents, out of which only 1-5% are severe.[7] Patients with mild allergies to contrast agents or other common drugs can be managed using premedications before they are taken for the scan, reducing the risk of fatal reactions.[8] However, moderate-to-severe reactions to these contrast agents are an absolute contraindication to the procedure, and in these patients, MRA is an indication for mapping. The first prospective cohort study comparing CTA with color Doppler ultrasound (CDU) was published by Rozen et al.[9] in 2008, and it was subsequently discontinued after enrolling eight patients due to significant interobserver variability and inconsistencies between imaging and operative findings. Strikingly, in this study, not a single perforator was found using CDU. A prospective research study by Scott et al.[10] that enrolled 22 patients and was published in 2010 revealed a 34% false negative rate for dominant perforator detection using CDU, in which they also found the CTA to be superior in evaluating the intramuscular segment of the deep inferior epigastric artery (DIEA) over CDU. In a study by Giunta et al.,[11] preoperative Doppler ultrasound produced approximately 47.6% false positive results, which were attributed to the relatively high sensitivity of CDU in locating very small perforating vessels that were not suitable for perforator flaps (due to their narrow diameters). Another prospective study conducted by Mijuskovic et al.[12] found a significantly stronger correlation between CDU and intraoperative findings of perforator detection, size, and selection compared with CTA data. The results of Mijuskovic et al. study were superior because highly specialized angiologists performed the CDUs; these may not be available at many high-volume centers performing modern microsurgical breast reconstruction.[12] Interobserver variability is a major drawback of CDU, especially in places where specialized angiologists are not available. The main disadvantage of acquiring MRA for mapping is performing an additional investigation as it augments the cost and time taken for the workup. The time of acquisition of MRA can range from 30 to 40 minutes, with longer sequence duration requiring patient cooperation, increasing the susceptibility to motion artifacts that hamper the diagnostic quality. Severe claustrophobia is another disadvantage where patients cannot undergo MRA and CTA is indicated in them. The incidence of an acute allergic reaction to gadolinium is about 0.07% which is lower compared to iodinated contrast; however, there is a rare risk of systemic reactions (such as nephrogenic systemic fibrosis) when used in patients with poor renal function.[13] The reported accuracy of MRA in identifying the three best perforators was about 88.4%, while CTA had an accuracy of about 95.6%. However, the suboptimal evaluation of the DIEA branching pattern and its intramuscular segment was a disadvantage for MRA.[6] These observations were mostly caused by the decreased contrast between the magnetic resonance (MR) signals from vessels and muscle during the equilibrium phase of enhancement used to choose the perforators, obstructing the clear vision of the perforator’s course through the muscle. The outcomes of MRA could also be compromised by magnetic field inhomogeneity, which would influence fat saturation across the anterior abdominal wall. According to the study done by Cina et al.,[6] the error in the measurement of calibers was slightly higher for MRA (1.63 ± 0.39 mm) than for CTA (1.18 ± 0.35 mm), with both techniques overestimating the size of the arteries. In another study by Phillips et al.,[4] a preliminary evaluation of six patients showed that abdominal wall MRA demonstrated poor reproducibility and a disappointing depiction of smaller perforator vessels. This was also observed in the pilot study of six patients done by Rozen et al.,[9] who concluded that MRA could help to visualize only larger perforators because of its relatively poor spatial resolution. The MRA technique is ever-changing and evolving, with recent studies showing more promising results. Apart from these, the lack of availability of MRI, especially at peripheral centers, is a major drawback. At the commencement of our study,[1] MRI was considered but failed miserably due to the above-mentioned reasons. Given the advantages of cost-effectiveness and quick acquisition, CTA remains the main diagnostic tool for mapping a perforator before undergoing DIEP flap reconstruction. Furthermore, it can be performed at the time of staging to reduce the potential disadvantages of additional investigations. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.