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![Imaging methods to evaluate tumor microenvironment factors affecting nanoparticle drug delivery and antitumor response](https://image.oaes.cc/3f718cf9-29f2-4ae9-b045-a3665856410d/3923.fig.4.jpg)
Figure 4. Tumor vasculature development and vessel tortuosity using photoacoustic imaging. (A) Volume-rendered 3-D photoacoustic image of a LS174T subcutaneous tumor (day 8 post inoculation) with arrows indicating artery-vein pairs. (B) Top: Maximum intensity projection (MIP) of the image presented in (A). The insets show magnified y-zy-z and x-yx-y MIPs of a region containing a small blood vessel. Bottom: Profiles across this vessel between points A-B and C-D were plotted and fitted with a Gaussian function to obtain spatial resolution. (C) Photoacoustic images of a larger SW1222 subcutaneous tumor (day 12 post-inoculation) illustrating an imaging depth of at least 9 mm. Figure reproduced with permission from[250].