Breast reconstruction is a common procedure that can dramatically improve the quality of life and satisfaction for women who undergo mastectomy, with over 100,000 procedures performed in the U.S. in 2018. The success of this procedure, however, is limited by its complications, including mastectomy skin flap necrosis, which occurs at a rate a 10-15%. Mastectomy skin flap necrosis causes significant morbidity in patients undergoing breast reconstruction, potentially compromising results and delaying oncologic management. In addition, necrosis can lead to infection, implant loss, and need for reoperation.

Current approaches to identify mastectomy skin flap necrosis rely largely on the surgeon's assessment of skin flap color, capillary refill, temperature turgor and dermal bleeding. However, clinical assessment of necrosis is subjective and is not a reliable predictor of postoperative complications. ICG microangiography is an accepted adjunct method to aid in clinical judgment by identifying poor perfusion as a surrogate marker for tissue at risk for necrosis during reconstructive surgical procedures. However, transient alterations in blood flow seen by this method may not represent actual necrosis. Furthermore, the common practice of using vasoconstriction methods to prevent massive blood loss in plastic surgery also alters microperfusion and renders the microangiography inaccurate. There is an unmet need for reliable methods to identify mastectomy skin flap necrosis during or post breast reconstruction procedure in order to improve patient outcomes.

Recently in animal models of burn or ischemic injuries, ICG dye was shown to preferentially bind to exposed phospholipids in the membranes of necrotic cells, thus acting as a biomarker for necrotic tissue, when imaged a day after injection rather than minutes after injection, as is standard for microangiographic use of ICG. This necrosis-avid property of ICG has broad translational potential for clinical use in a variety of disease processes that result in necrosis. However, no clinical application of the necrosis-avid property of ICG has been reported yet. In this study, the investigator will test the feasibility of combining the necrosis-avid property of ICG and the SPY imaging system at University of Wisconsin hospital to obtain delayed imaging of ICG fluorescence for direct necrosis detection in breast reconstruction in mastectomy patients.

This project is an early feasibility study to establish whether ICG imaging, in a delayed fashion, can be used in mastectomy patients to aid in the detection of necrotic tissue in breast reconstruction wounds. Investigators will use the preliminary data generated from this pilot study to generate hypotheses and to power future studies.

Inclusion Criteria:

• Female, age 18 years or older
• Subject undergoes mastectomy
• Subject receives intraoperative ICG during their breast reconstruction procedure
• Subject is expected to need at least 4 days of hospitalization as determined by the attending plastic surgeon on admission
• Subject understands the study procedures and can provide informed consent to participate in the study and authorization for release of relevant protected health information to the study investigator.

Exclusion Criteria:

• Subject has known contraindication to ICG injection, i.e. previous reaction to ICG (adverse event rate 1 in 42,00010)
• Subject has Iodine allergy
• Subject is pregnant