Published in the December 2023 issue of Ultrasound in Obstetrics and Gynaecology, Quing Zhu (Washington University, St Louis, USA) et al state that they have developed a novel imaging method which combines photoacoustic imaging (PAI) with ultrasound to better diagnose lesions in the ovaries and adjacent adnexa.
Without a standard screening test that can assist with early detection of ovarian cancer, ultrasound imaging is most commonly used. Ultrasound in this setting is not always accurate, the researchers exposit, which has historically led some patients to have their ovaries unnecessarily removed.
In developing this technique, Zhu and colleagues incorporated functional biomarkers with PAI which illuminates tissue with a near-infrared light at specific wavelengths that are then absorbed differently by oxygenated and deoxygenated haemoglobin.
Enrolling 68 women with ovarian/adnexal lesion(s) suggestive of malignancy referred for oophorectomy—the surgical removal of the ovaries/adnexal lesions, participants underwent a clinical ultrasound examination followed by a co-registered ultrasound and PAI prior to oophorectomy. The researchers note that each ovarian/adnexal lesion was graded by two radiologists using the ovarian-adnexal reporting & data system (O-RADS) scale.
Among the included patients, 93 lesions were identified overall; 14 patients were found to have malignant lesions in their ovaries or adnexal regions, two patients had malignant fallopian tubes, and 52 patients had benign lesions. When comparing the malignant and benign lesions, Zhu et al found that the relative total haemoglobin in patients with malignant lesions in the ovaries and in the adnexal region was 1.8 times higher than in those with benign lesions. Blood oxygen saturation was 5% lower in those with malignant lesions, though this was not a statistically significant difference.
The team found that the most important predictors of malignancy were relative total haemoglobin, the O-RADS score, presence of the cancer antigen CA 125, and percentage of blood oxygen saturation (sO2). Their model, which incorporates all four features, achieved “superior performance” for sensitivity of 100% and specificity of 82%.
“Photoacoustic imaging combined with ultrasound provides complementary diagnostic imaging data involving structure and function,” Zhu said. “The ultrasound localises the lesion, and the photoacoustic images inform tumour haemoglobin content and percent of blood oxygen saturation.”
Co-principal investigator Matthew Powell (Washington University, St Louis, USA) expanded on the value of their findings: “Women frequently develop ovarian cysts, which cause a great deal of worry. This technology should quickly and easily be able to help assure both the doctor and the patient that most of these can be watched, and unnecessary surgery can be avoided. These surgeries can lead to loss of fertility and early menopause. This technology and other imaging advancements could be immensely helpful to improve the lives of our patients.”
Cary Siegel (Washington University, St Louis, USA)—a fellow co-principal investigator who worked alongside Powell and Zhu—adds that carrying out an assessment of an adnexal mass can be “challenging” for experienced radiologists, as “many different benign and malignant causes are often among possibilities for diagnosis”. However, by deploying their novel photoacoustic ultrasound technique “accuracy and confidence” can be given to radiologists to improve early diagnosis and treatment of ovarian cancer. “With early diagnosis, our ultimate goal is to improve ovarian cancer survival. Working with Powell, Zhu and her engineering team has been a highlight of my medical career,” Siegel concludes.
