Thyroid nodules are prevalent in up to more than 50% of the population above the age of 50. However, most of the nodules are benign and asymptomatic. The diagnostic methods of choice are ultrasonography and scintigraphy – the former lacking in specificity (resulting in a high number of unnecessary biopsies) and the latter necessitating exposure to ionizing radiation. Initial studies suggest that optoacoustic imaging has the potential to differentiate thyroid nodules on the basis of their perfusion and oxygenation.

A schematic shows the illumination and subsequent ultrasound detection of MSOT signal.

Principles of clinical MSOT of the thyroid

Transversal ultrasound image of the thyroid gland and surrounding tissue allows the exact localization of anatomic structures. The regions of interest identified in ultrasound images are then transferred to the co-registered pseudocolor-coded MSOT images for visual and quantitative analysis.

Roll et al. J Nucl Med. 2019

Functional markers of inflammatory activity in Graves’ disease

Graves‘ disease, also known as toxic diffuse goiter, is an autoimmune disease that affects the thyroid. Quantification of MSOT images shows significantly elevated HbR and HbT values and significantly reduced fat values in thyroid lobes affected by Graves’ disease compared to healthy thyroid tissue.

Roll et al. J Nucl Med. 2019

MSOT-derived quantification of deoxy- (HbR) and oxyhemoglobin (HbO2), total hemoglobin (HbT), tissue oxygen saturation (sO2), fat, and water.

Co-registered pseudocolered MSOT image of sO2 weighted with the signal of total hemoglobin in red/yellow/green overlaid with transparency onto a greyscale ultrasound image.

Functional markers in benign and malignant thyroid nodules

Malignant nodules show significantly reduced MSOT-derived tissue oxygen saturation values compared to benign nodules. Preliminary clinical studies demonstrate the potential of MSOT coupled with ultrasound to semi-quantitatively provide tissue characterization and functional parameters in thyroid disorders for improved non-invasive diagnostics of thyroid diseases.

Roll et al. J Nucl Med. 2019