SIGMA* by Imagivo

*Surgical Imaging Guide for Margin Analysis

Overview

The Problem

Head and neck cancers have a 50% survival rate due to multiple factors [1]. First, it is difficult to achieve complete removal of malignant tissue during surgical resection via manual assessment methods. Second, any remaining cancerous tissue can aggressively progress and metastasize throughout the body. Out of extraneous caution, large masses of unaffected functional tissue around the targeted area may be extracted to ensure complete tumor removal and reduce the chance of recurrence [2]. This results in significant loss of function and extensive cosmetic damage. Subsequent surgeries to remove previously undetected cancerous tissue can be challenging to perform, especially in advanced stages of cancer or on older patients, as their bodies may be too weak to survive additional invasive procedures. It is essential for physicians to accurately analyze the resected tissue while the patient is on the operating table as this helps ensure the complete removal of the tumor and minimizes future procedures for the patient. Because of this, there is a clear clinical need to improve margin assessment methods.

Margin Analysis

Margins are defined as the distance from the surface of the specimen to cancerous tissue. Typically, surgeons take a sample of a tumor and send it to pathology for frozen sectioning. If there is >=5mm of normal tissue depth, then it is defined as clear margin. if cancer is found on the edges then it is said to be positive margin. Anything in the middle is considered a close margin.* Patients are 6 times more likely to survive if margins are clear.

Margin assessment is crucial as it tells the surgeon where and how much to cut and excise the tissue. But, in sectioning, depending on the slices examined, there is a high chance for missed cancer as only a few slices are examined and the procedure is also time-consuming. Because of the complex anatomy in the head and neck region and the limitations of this analysis, 30-50% of surgical procedures fail to obtain tumor-free surgical margins.

*Acceptable margin allowances vary for different types of cancer based on amount of functional tissue in the area and aggressiveness of cancer.

The presented issues in head and neck cancer surgeries were addressed by a previous year’s senior design team who developed the RApid Surgical Margin Assessment Device (RASMAD).** RASMAD is a tissue biopsy imager that uses fluorescence-guided imaging to assess cancer margins. It is currently under clinical trials with six patients at the University Medical Center of Groningen (UMCG) in the Netherlands. While RASMAD showed promising results, the system had limitations. First, the system was not able to accurately identify the depth of the tumor and distinguish tumor tissue locations because of the low signal-to-noise ratio (SNR) of the images. Second, the system lacked full automation and required imprecise manual readjustments of components, which led to difficulties fitting into the clinical workflow of the surgeon. Team Imagivo discussed these concerns with not only the UMCG group, but also surgeons from Stanford, Dartmouth, UC San Diego, and UChicago.

Imagivo confirmed that the user needs most critical to patient outcomes included improved quality of the images through high SNR for improved tumor depth detection and ease of use of the device (optimization & automation) for better incorporation into clinical environments without the need for extensive technical understanding of the system.

Our Solution

To improve margin assessment, Team Imagivo has developed a device known as SIGMA (Surgical Imaging Guide for Margin Assessment) that uses fluorescence imaging to guide tumor resection. SIGMA aims to address all three concerns that were voiced by the clinicians (tumor depth, signal-to-noise ratio, and automation) by incorporating raster scanning, a new image reconstruction algorithm, an automated height control, and data collection system.

[1] Baddour, H. M., Magliocca, K. R., & Chen, A. Y. (2016). The importance of margins in head and neck cancer: Margins in Head and Neck Cancer. Journal of Surgical Oncology, 113(3), 248–255. https://doi.org/10.1002/jso.24134 [2] Ang, K. K., Berkey, B. A., & Tu, X. (n.d.). Impact of Epidermal Growth Factor Receptor Expression on Survival and Pattern of Relapse in Patients with Advanced Head and Neck Carcinoma. 9. ** Allyson Trang, Brooke Villinski, Jennifer Vorhan, Sophia Nelson, Senior Design Team, 2021

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