We report a novel photoacoustic (PA) scoring method for the risk stratification of thyroid nodules, which is combination of the American Thyroid Association (ATA) and PA malignancy probability. We performed multi-spectral PA imaging and multi-parametric PA analysis for thyroid cancer patients (23 malignancy and 29 benign cases). Initial multi-parametric PA analysis showed that malignancy of the thyroid nodules can be diagnosed with a 78% sensitivity and 93% specificity. Moreover, our novel score called ATAP improved the sensitivity to 83% while maintaining the specificity. The results suggest that the ATAP may help physicians examine thyroid nodules, thus reducing unnecessary biopsies.
Thyroid cancer is one of the most commonly diagnosed cancers in the world. Ultrasonography and fine-needle aspiration biopsy are the typical standard-of-care method for diagnosing thyroid nodules. However, about 20% of fine-needle aspiration biopsies generate undeterminable results, which can lead to overdiagnosis and overtreatment. In this study, we propose photoacoustic imaging as an additional triaging tool for identifying cancerous nodules in vivo. We enrolled and photoacoustically imaged 28 patients (19 malignant and 9 benign) who have thyroid nodules. To perform multispectral analysis, we used a series of 5 different wavelengths (i.e., 700, 756, 796, 866, and 900 nm), which were selected based on the optical absorption property of oxy- and deoxy-hemoglobin. All the raw data were automatically stored for further off-line processing, while the corresponding images were visualized on the clinical ultrasound machine in real-time. By using the multispectral photoacoustic data, we calculated the oxygen saturation values of the nodule areas. The result showed that the oxygen saturation level of malignant nodules was lower than that of benign nodules (p < 0.005), which matched with the well-known property of cancerous nodules. Based on the oxygen saturation value, malignant and benign nodules were differentiable with a sensitivity of 80% and specificity of 89%. The result showed the great potential of multispectral photoacoustic analysis as a novel method to identify malignancy of thyroid nodules in vivo. We also verified the robustness of the result by testing reproducibility and comparing inter-physician interpretation.
Thyroid cancer is one of the most prevalent cancers. About 3-8% of the people in the United States have thyroid nodules, and 5-15% of these nodules are malignant. Fine-needle aspiration biopsy (FNAB) is a standard procedure to diagnose malignity of nodules. However, about 10-20% of FNABs produce indeterminable results, which leads to repeat biopsies and unnecessary surgical operations. We have explored photoacoustic (PA) imaging as a new method to identify cancerous nodules. In a pilot study to test its feasibility, we recruited patients with thyroid nodules (currently 36 cases with 21 malignant and 15 benign nodules), acquired in vivo PA and ultrasound (US) images of the nodules in real time using a recently-developed clinical PA/US imaging system, and analyzed the acquired data offline. The preliminary results show that malignant and benign nodules could be differentiated by utilizing their PA amplitudes at different excitation wavelengths. This is the first in vivo PA analysis of thyroid nodules. Although a larger-scale study is needed for statistical significance, the preliminary results show the good potential of PA imaging as a non-invasive tool for triaging thyroid cancer.
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