# Multispectral optoacoustic tomography of benign parotid tumors in vivo: a prospective observational pilot study

## TL;DR

This study explores using multispectral optoacoustic tomography to distinguish benign parotid tumors from healthy tissue in a small group of patients.

## Contribution

The first prospective pilot trial using MSOT to differentiate between pleomorphic adenoma and Warthin tumor in vivo.

## Key findings

- MSOT parameters for pleomorphic adenoma and Warthin tumor differed significantly from healthy parotid tissue.
- Maximal MSOT parameters showed differences between the two tumor types, particularly at 900 nm and hemoglobin-related metrics.
- No significant differences were found in mean MSOT parameters between pleomorphic adenoma and Warthin tumor.

## Abstract

Parotid lumps are a heterogeneous group of mainly benign but also malignant tumors. Preoperative imaging does not allow a differentiation between tumor types. Multispectral optoacoustic tomography (MSOT) may improve the preoperative diagnostics. In this first prospective pilot trial the ability of MSOT to discriminate between the two most frequent benign parotid tumors, pleomorphic adenoma (PA) and Warthin tumor (WT) as well as to normal parotid tissue was explored. Six wavelengths (700, 730, 760, 800, 850, 900 nm) and the parameters deoxygenated (HbR), oxygenated (HbO2), total hemoglobin (HbT), and saturation of hemoglobin (sO2) were analyzed. Ten patients with PA and fourteen with WT were included (12/12 female/male; median age: 51 years). For PA, the mean values for all measured wave lengths as well as for the hemoglobin parameters were different for the tumors compared to the healthy parotid (all p < 0.05). The mean MSOT parameters were all significantly higher (all p < 0.05) in the WT compared to healthy parotid gland except for HbT and sO2. Comparing both tumors directly, the mean values of MSOT parameters were not different between PA and WT (all p > 0.05). Differences were seen for the maximal MSOT parameters. The maximal tumor values for 900 nm, HbR, HbT, and sO2 were lower in PA than in WT (all p < 0.05). This preliminary MSOT parotid tumor imaging study showed clear differences for PA or WT compared to healthy parotid tissue. Some MSOT characteristics of PA and WT were different but needed to be explored in larger studies.