Fat grafting has been gaining popularity over the past decade. It is now commonly used for breast augmentation and reconstruction, however a major challenge remains the high rate and unpredictable rate of fat resorption post-operatively, leading to volume loss and patient dissatisfaction. Currently there is no consensus on the ideal technique to process donor fat to minimize the rate of resorption. Our study aims to compare two common processing methods to determine if one is superior for fat volume retention.

Fat grafting is a technique used commonly in plastic surgery that has gained popularity in breast augmentation and breast reconstruction. This technique involves harvesting fat using liposuction from donor sites, processing the extracted fat and re-injecting it back into the breast for the desired volume and shape. Fat grafting has gained popularity due to its resulting natural appearance and feel. This technique can also be used in conjunction with implant reconstruction to achieve a more natural contour and symmetry. However, the main issue is a low rate of fat retention, which, based on the literature, is inconsistent and only an average of 60% of the volume of fat injected. Furthermore, there are very few clinical studies studying the long-term clinical survivability of the grafted fat. Therefore, care must be taken in setting patient expectations, and sometimes multiple sessions are required to achieve the desired results.

There are currently multiple techniques used in harvesting and processing fat for grafting, and it is unclear in the current literature if the processing technique used affects the level of fat resorption. General principles of fat grafting include gentle extraction to avoid damage and processing to remove excess infiltration fluid and impurities before injection. The fat is collected from donor areas for extraction, using either manual or power-assisted liposuction. For processing, several products and processing solutions have been developed in recent years, including the Revolve system (AbbVie/Allergan), which is currently used at our institution. Prior to these systems, simple decantation of fat by gravity or centrifugation was used. However, due to damage to fat during processing and lower retention rates in the literature, centrifugation has largely been abandoned as a processing method. However, there is no standard method of donor fat harvest or processing, and there is a lack of well-defined prospective clinical studies comparing popular techniques in the current literature, particularly in the long term. Additionally, the amount of fat injected and patient factors such as previous radiation can affect the amount of fat retention. Further in-vitro studies are required to clarify factors that affect fat survivability.

In order to assess the rate of fat retention in the breast, quantitative imaging tools have been validated in the literature. One of the most popular techniques is 3D body surface scans. These can be taken easily, quickly, and cost-effectively for volume assessment at various time points pre and postoperatively. Comparatively, MRI imaging is costly, time-consuming and therefore not practical for frequent follow-up. Furthermore, as 3D imaging becomes more accessible, its use could become more common in clinical practice for preoperative planning and objective assessment of outcomes.

Methods Aims Currently, there is a lack of prospective clinical studies directly comparing the rate of fat graft retention between processing techniques. Our primary outcome aims to compare two common processing methods; decantation and the Revolve system. Investigators will measure the retention rate using 3D imaging techniques (Vectra H2, Canfield), in the place of traditional 2D photography, for quantitative measurement of breast volume. Our secondary outcomes include the assessment of operating time, cost, and collect secondary outcomes related to surgical complications and outcomes. Investigators will tangentially perform a qualitative review of the patient's pre and post-operatively using the validated Breast-Q questionnaire. This study will be conducted at LHSC sites in London, Ontario.

Inclusion Criteria:

• Any patient above the age of 18 undergoing fat grafting from any donor site to the breast for cosmetic or reconstructive purposes.
• We will accept patient who have an implant for either cosmetic or reconstructive purposes

Exclusion Criteria:

• Previous fat grafting
• Autologous breast reconstruction (regional or free flap)
• unable to consent to the study

This is an ongoing discussion. At present there is a slight lean towards not making individual participant data available. This is to protect patient information during inclusion in this trial.

When the patients check in at the reception desk, they will be assigned a ticket with a 0 or 1 sequentially. This will be placed in their file. Group 0 patients will receive Decantation, and group 1 will receive Revolve.

The nurse will collect this ticket, along with the patient's registration documents to prepare the equipment.

Photography will be done by a research assistant/coordinator. The person will be responsible for imaging patients, as well as conducting the volume analysis following training by the software manufacturer. This person will be blinded to which method is used.

During subsequent follow ups, the patient will have a 0 or 1 in their chart, to accurately collect data while in follow up.

The surgeon, assistants and nurses will not be able to be blinded as they are the person responsible for using the device in the operating room.