Intraoperative Optical and Fluorescence Imaging of Blood Flow Distributions in Mastectomy Skin Flaps for Identifying Ischemic Tissues

Mastectomy Skin Flap Perfusion Assessment Prior to Breast Reconstruction: A Narrative Review

BACKGROUND

Predicting the viability of the skin flaps after mastectomy is of high importance and significance in immediate breast reconstruction. Numerous methods have been used and are readily available. This review aims to describe and compare the current preferred perfusion assessment tools.

METHODS

Four major scientific databases-Web of Science, PubMed, Embase, and Scopus-were consulted to retrieve reviews, meta-analyses, clinical trials, experimental studies, and case reports focused on skin flap perfusion assessment following mastectomy. English-language articles published within the last 10 years were included. The most recent search was conducted on 31 July 2024.

RESULTS

A summary focused on the relevant information of all included studies was drafted, and the results of the studies have been synthetized and compared. A total of 58 studies have been included in this review.

CONCLUSION

Indocyanine green angiography (ICG-A) is the preferred and most-used method of evaluating perfusion, especially in high-risk patients, while new technologies show promising results and might be of great interest in the future. Perfusion assessment tools complement and should not replace clinical evaluation.

Prediction of Mastectomy Skin Flap Necrosis With Indocyanine Green Angiography and Thermography: A Retrospective Comparative Study

OBJECTIVE

This study investigates the predictive role of indocyanine green angiography and thermography in assessing mastectomy skin flap necrosis in the intraoperative and postoperative setting.

METHODS

A retrospective review of 45 patients who underwent nipple-sparing mastectomy and immediate prepectoral reconstruction was performed. Mastectomy flap viability was evaluated intraoperatively with indocyanine green angiography and thermography after placement of an implant sizer and again postoperatively at 24 hours. Fluorescence pattern was analyzed with a near-infrared camera (IC-FlowTM Imaging System, Diagnostic Green GmbH, Germania) and thermographic images with FLIR ONE device. FLIR ONE and ICG images were then transposed on macroscopic breast images with a scale 1:1. The mastectomy skin flap was evaluated using the SKIN score (Mayo Clinic Classification).

RESULTS

Overlap between angiography and thermography images was 87.95% intraoperatively and 95.95% 24 hours postoperatively. Overlay with mastectomy flap necrosis was higher in the intraoperative angiography group with statistical significance. Contrarily, such a difference was not apparent in the postoperative period.

CONCLUSIONS

ICG appears to be a superior tool when used intraoperatively with fundamental implications on reconstructive decision-making, while thermography could be a valuable assessment method in the postoperative setting. Further studies are necessary to confirm such results and determine their clinical applicability.

Use of Ambient Light Compatible Fluorescence-Guided Surgical Technology for Objective Assessment of Flap Perfusion in Autologous Breast Reconstruction

BACKGROUND

 Decreased autologous flap vascular perfusion can lead to secondary procedures. Fluorescence angiography during surgery reduces the probability of repeat surgery but suffers from interpretation variability. Recently, the OnLume Avata System was developed, which evaluates real-time vascular perfusion in ambient light. This study aims to predict complications in autologous breast reconstruction using measures of relative intensity (RI) and relative area (RA).

METHODS

 Patients undergoing autologous breast reconstruction underwent intraoperative tissue perfusion assessment using the OnLume Avata System. Post-hoc image annotation was completed by labeling areas of the flap interpreted to be "Well Perfused," "Questionably Perfused," and "Under Perfused." RIs and RAs were calculated for the marked areas. Primary complications of interest were overall complication rate, fat and mastectomy skin flap necrosis, and surgical revision. Logistic regression was applied to determine the odds of developing a complication based on RI and RA for each image.

RESULTS

 A total of 25 patients (45 flaps) were included. In total, 17 patients (68%) developed at least one complication. Patients who developed any complication (p = 0.02) or underwent a surgical revision for complications (p = 0.02) had statistically lower RI of under-perfused portions of the flap. Patients with greater areas of under-perfused flap had a significantly higher risk of developing fat necrosis (odds ratio [OR]: 5.71, p = 0.03) and required a revision operation (OR: 1.10, p = 0.01).

CONCLUSION

 Image-based interpretation using the OnLume Avata System correlated with the risk of developing postoperative complications that standard fluorescence imaging systems may not appreciate. This information can benefit surgeons to improve perfusion assessment and intraoperative decision-making.

Evaluating Arterialized Vein in Thumb Replantation using Indocyanine Green Angiography: A Case Report

BACKGROUND The absence of valid vessels for the anastomosis constitutes a contraindication to replantation, but the need for arterial vessels in good condition has recently been questioned and some authors have proposed the arterialization of the veins with promising results. However, this method is not routine in replantation and it is unclear what conditions can establish venous congestion and loss of the replanted segment. CASE REPORT We detail a case where indocyanine green aids in evaluating arterialization of a vein during thumb replantation in a 40-year-old smoker following a crush injury. Multiple attempts to anastomose the princeps pollicis and its collateral vessel failed due to a thrombus formation, leaving the finger non-perfused despite urokinase treatment. To confirm the absence of reperfusion, we administered 0.3 mg/kg of indocyanine green through an upper limb peripheral vein. Observing no reperfusion, we located a suitable radial dorsal vein and performed an arteriovenous anastomosis at the proximal phalanx level. Indocyanine Green Angiography (IGA) revealed a slightly delayed reperfusion but a effective venous outflow. We did not consider it necessary to perform additional venous anastomoses other than the single dorsal radial venous anastomosis. CONCLUSIONS This single case report shows the potential of indocyanine green as a valid aid to evaluate the perfusion of the replantation and also any early venous congestion, being able to modify the operative plan accordingly.

Depth-sensitive diffuse speckle contrast topography for high-density mapping of cerebral blood flow in rodents

Significance

Frequent assessment of cerebral blood flow (CBF) is crucial for the diagnosis and management of cerebral vascular diseases. In contrast to large and expensive imaging modalities, such as nuclear medicine and magnetic resonance imaging, optical imaging techniques are portable and inexpensive tools for continuous measurements of cerebral hemodynamics. The recent development of an innovative noncontact speckle contrast diffuse correlation tomography (scDCT) enables three-dimensional (3D) imaging of CBF distributions. However, scDCT requires complex and time-consuming 3D reconstruction, which limits its ability to achieve high spatial resolution without sacrificing temporal resolution and computational efficiency.

Aim

We investigate a new diffuse speckle contrast topography (DSCT) method with parallel computation for analyzing scDCT data to achieve fast and high-density two-dimensional (2D) mapping of CBF distributions at different depths without the need for 3D reconstruction.

Approach

A new moving window method was adapted to improve the sampling rate of DSCT. A fast computation method utilizing MATLAB functions in the Image Processing Toolbox™ and Parallel Computing Toolbox™ was developed to rapidly generate high-density CBF maps. The new DSCT method was tested for spatial resolution and depth sensitivity in head-simulating layered phantoms and in-vivo rodent models.

Results

DSCT enables 2D mapping of the particle flow in the phantom at different depths through the top layer with varied thicknesses. Both DSCT and scDCT enable the detection of global and regional CBF changes in deep brains of adult rats. However, DSCT achieves fast and high-density 2D mapping of CBF distributions at different depths without the need for complex and time-consuming 3D reconstruction.

Conclusions

The depth-sensitive DSCT method has the potential to be used as a noninvasive, noncontact, fast, high resolution, portable, and inexpensive brain imager for basic neuroscience research in small animal models and for translational studies in human neonates.

Quantification of Indocyanine Green Fluorescence Imaging in General, Visceral and Transplant Surgery

Near-infrared (NIR) imaging with indocyanine green (ICG) has proven to be useful in general, visceral, and transplant surgery. However, most studies have performed only qualitative assessments. Therefore, a systematic overview of all studies performing quantitative indocyanine green evaluation in general, visceral, and transplant surgeries should be conducted. Free term and medical subject heading (MeSH) term searches were performed in the Medline and Cochrane databases until October 2022. The main categories of ICG quantification were esophageal surgery (24.6%), reconstructive surgery (24.6%), and colorectal surgery (21.3%). Concordantly, anastomotic leak (41%) was the main endpoint, followed by the assessment of flap perfusion (23%) and the identification of structures and organs (14.8%). Most studies examined open surgery (67.6%) or laparoscopic surgery (23.1%). The analysis was mainly carried out using manufacturer software (44.3%) and open-source software (15.6%). The most frequently analyzed parameter was intensity over time for blood flow assessment, followed by intensity alone or intensity-to-background ratios for structure and organ identification. Intraoperative ICG quantification could become more important with the increasing impact of robotic surgery and machine learning algorithms for image and video analysis.

Prepectoral Breast Reconstruction

Prepectoral breast reconstruction has gained popularity due to numerous benefits in properly selected patients. Compared with subpectoral implant reconstruction, prepectoral reconstruction offers preservation of the pectoralis major muscle in its native position, resulting in decreased pain, no animation deformity, and improved arm range of motion/strength. Although prepectoral reconstruction is safe and effective, the implant sits closer to the mastectomy skin flap. Acellular dermal matrices play a critical role, allowing for precise control of the breast envelope and providing long-term implant support. Careful patient selection and intraoperative mastectomy flap evaluation are critical to obtaining optimal results with prepectoral breast reconstruction.