# Photoacoustic Imaging for Management of Breast Cancer: A Literature Review and Future Perspectives
## 3 Results
### Endogenous Contrast Agents  
[PERSON] et al. [67] used the Twente PA Imaging system at the 1064 nm wavelength on a rat model to visualize the vasculature development from the early stages of tumor growth. They showed that using PA imaging, the tumor neovascularization could be monitored without sacrificing the animal, which established PA imaging as a promising new tool in tumor angiogenesis research. [PERSON] et al. [75] performed in vivo spectroscopic PA imaging with a transgenic mouse model to evaluate the feasibility of differentiating among different breast pathologies (normal, hyperplasia, DCIS, IBC), in terms of oxygen saturation, total hemoglobin content and lipid content. Spectroscopic PA imaging of this study \begin{table}
\begin{tabular}{c c c} \hline \hline \multirow{2}{*}{**Phantom Study**} & **Materials Mimicking Breast Tissue** & **Materials Mimicking Tumor/Blood Vessel/Target** \\ \hline [PERSON] et al. [64] & 10\% gelatin (\(\mu_{\text{a}}=0.13\) cm\({}^{-1}\)) & Polyethelene tubes filled with the blood of sheep (\(\mu_{\text{a}}\) in the range of 0.45 to 1.0 cm\({}^{-1}\)). \\ \hline [PERSON] et al. [65] & Polyvinyl chloride-plastisol (PVCP) & Pencil leads \\ \hline [PERSON] et al. [66] & India ink dissolved in aqueous milk solution & A thin-wall rubber shell filled with India ink dissolved in aqueous milk solution \\ \hline [PERSON] et al. [59] & Poly vinyl alcohol (PVA) gel & Dyed, rigid PVA gel spheres \\ \hline [PERSON] et al. [67] & Intralipid, PVA & A silicon rubber tube filled with flowing human blood and dyed, rigid PVA gel spheres \\ \hline [PERSON] et al. [68] & Agar/intralipid gel & Plastic tube filled with agar gel and spherical objects made of agar gel \\ \hline [PERSON] et al. [60] & Chick breast muscle & Raw blood in 1.5 mm diameter tube \\ \hline [PERSON] et al. [69] & Porcine fat & water-based agar gel 2\% agar, 2\% salt and 96\% water): clear gel/gel mixed with black India ink \\ \hline [PERSON] et al. [70] & Chick breast & Low-density polyethylene (LDPE) tubes filled with either oxygenated bovine blood or methylene blue dye \\ \hline [PERSON] et al. [71] & 13\% gelatin, 12.5\% milk, and 74.5\% water & Carbon points \\ \hline [PERSON] et al. [72] & Intralipid + India ink & Thin metal wires and ex-vivo tumor tissue \\ \hline [PERSON] et al. [73] & Carbon/graphite fiber embedded in agar & Point absorber (a small spot of ink placed on the tip of a clear, thin polyethylene thread) \\ \hline [PERSON] et al. [74] & Gelatin & Astaxanthin-mediated gold nanoparticles (Atx-AuNPs)-treated breast cancer cells \\ \hline \hline \end{tabular}
\end{table} 
Table 3: _Cont._resulted in the increased oxygen saturation of hyperplasia (50.6%), DCIS (43.0%), and IBC (46.2%) as compared to normal glands (35.5%), whereas both the total hemoglobin and lipid content significantly decreased with advancing histology. Exogenous Contrast Agents  
[PERSON] et al. [76] performed PA imaging at 820 nm in a mouse model to evaluate the feasibility of using non-fluorescent nanodiamond as PA imaging contrast agents for effective HER2 positive breast cancer detection. [PERSON] et al. [77] performed an in vivo PA imaging study with folate-conjugated polymer (CP) dots as contrast agents in xenograft mice models and they demonstrated that after 1 h of the injection of the contrast agents, the Polate-CP dots accumulated into the tumor site produced fourfold contrast-enhanced PA signal as compared to PA signals produced by CP dots. In an in vivo study with female Balb/c mice, [PERSON] et al. [78] acquired PA as well as fluorescence images of subcutaneous 4T1 tumors using melanin carbonaceous dots (MCDs) as contrast agents. [PERSON] et al. [79] performed an in vivo PA imaging study with nude mice using biodegradable nanomaterial liposome-encapsulating ammonium bicarbonate (NH\({}_{4}\)HCO\({}_{3}\)) as a PA contrast agent. [PERSON] et al.