Study of the protocol used to evaluate skin-flap perfusion in mastectomy based on the characteristics of indocyanine green

Background: Indocyanine green angiography enables real-time visualization of blood vessels at depths of up to 10 mm beneath the body surface, thereby aiding the evaluation of the viability of skin flaps and predicting necrosis in surgical fields requiring good tissue perfusion. Although skin-flap necrosis also occurs in mastectomy without reconstruction, most studies have focused on reconstructive plastic surgery. Several patients undergoing mastectomy are eligible for postoperative adjuvant therapy, but complications can lead to delays in treatment and thus require prevention. However, a lack of a standard protocol for evaluating skin-flap perfusion using indocyanine green necessitates the study of its characteristics to facilitate comparison of the perfusion rate among individuals. Methods: This retrospective study focused on the characteristics of indocyanine green and established a protocol for indocyanine green angiography using laser-assisted imaging (SPY system) to predict postoperative skin-flap necrosis from intraoperative images of 30 patients who underwent mastectomy without reconstruction. Results: Our protocol predicted postoperative skin-flap necrosis as follows. First, the intravenous dose and concentration were set at 2.5 mg/mL and 0.05 mg/kg, respectively. Second, the timing of measurement was set to 100 s after the entry of indocyanine green into the skin (plateau phase); the analysis pattern was set to single frame. Third, comparisons among individuals were made using relative values. Conclusions: We analyzed the area of postoperative flap necrosis using this protocol. We found that the intraoperative images showed decreased perfusion in that area, which was useful in predicting skin-flap necrosis, as reported by previous breast reconstruction studies.