# Photoacoustic Imaging for Management of Breast Cancer: A Literature Review and Future Perspectives
## 3 Results
### Endogenous Contrast Agents
#### 3.1.4 In Vivo Studies  
In 2007, the research group of [PERSON] [103] performed in vivo PA imaging studies on human breast cancer patients. Later on, in 2009, the research group headed by [PERSON] [66], performed in vivo studies on human patients using PA imaging for breast cancer detection. During 2012-2015, the largest clinical study on 2105 patients was performed by the research group of [PERSON] [37; 38] using the dual mode PA-US imaging system (IMAGIO) for breast cancer detection, and in 2016, they performed another in vivo study using the same system for breast cancer detection. In 2018, the research group of [PERSON] [104; 105] reported their study results on 209 patients using the dual mode PA-US imaging system (IMAGIO) for breast cancer detection. In 2013, [PERSON]'s research group [73] performed an in vivo study on human patients using PA imaging. During 2015-2018, the research group headed by [PERSON] [106; 107] performed two in vivo studies on human patients using PA imaging. Research group of [PERSON] [39; 47; 108; 109] reported four in vivo studies during 2014-2017 on human patients using PA imaging during 2014-2017 and in 2015, the research group of [PERSON] [110] performed an in vivo study using functional PA imaging system for breast cancer detection. Details of these studies performed by each research group are summarized below. In a pilot clinical study conducted with the PA imaging system involving 27 patients, [PERSON] et al. [66] successfully visualized 18 out of 20 malignant lesions suspected from the X-ray and the US images. Their findings were confirmed by the biopsy procedure, performed after the PA image acquisition. [PERSON] et al. [111] developed \(\rm{Imagio}^{TM}\) breast imaging system with a specialized duplex handheld probe by fusing a functional PA imaging with a gray-scale ultrasound. This system was tested on 74 breast masses and found that this system could provide better specificity and equal sensitivity as compared to conventional US imaging. Another pilot study was conducted by the same group involving the first 100 subjects from a multi-center pivotal study of \(\rm{Imagio}^{TM}\) system. The results of this study indicated that the number of all negative biopsies could be potentially reduced by 21.4%. [PERSON] et al. [37; 38] performed a multi-center pivotal study during 2012-2015 involving 2105 women with 2191 breast masses using their dual mode PA-US imaging system (IMAGIO). From the 2191 masses, 210 masses were excluded due to technical failures/incomplete imaging, 78 masses were excluded due to protocol deviations, 43 masses were excluded due to high-risk histologic results along with 103 masses were excluded as they were utilized as training population. Finally, they have included only 1690 women with 1757 breast masses (benign cases: 1079 and malignant cases: 678) in their study analysis. From the results of their study, they claimed that the diagnostic specificity of the dual mode PA-US imaging system was improved 14.9% over the internal US imaging system alone. The study results support the utility of dual mode PA-US imaging system as a potential device for improving diagnostic performance of breast mass assessment. The dual mode PA US imaging technology can potentially improve specificity in differentiating between malignant and benign breast masses, which can reduce the number of benign breast mass biopsies as well as false-positive examinations. [PERSON] et al. [112] performed a multicenter in vivo study with their dual mode PA-US imaging system on 94 breast masses. They found that the dual mode system showed 7.9% improvement in specificity compared to their US imaging system, whereas the sensitivities of both PA-US, as well as only the US system, were 97.1%. [PERSON] et al. [104; 105] performed a multicenter study during 2015-2016 using a dual mode PA-US imaging system on 215 breast masses which, prior to dual mode imaging, were assigned to specific BI-RADS categories based on the US imaging alone.