Beled probe can be particularly accumulated in tumor tissues. In vivo scintigraphic imaging with 99mTc-RRL revealed a higher tumor uptake in the mice bearing HepG2 xenografts. Tumor was imaged clearly, and radiotracer accumulation was also displayed in the kidneys and stomach, and that might indicate the limited application of 99mTc-RRL planar imaging in tumors in these organs. Higher uptake in stomach was observed in both biodistribution analysis and in vivo imaging study. Besides the uptake of free pertechnetate in gastric mucosa, the release of free pertechnetate during catabolism of 25033180 the conjugate in vivo led to a certain degree of catabolic instability of the radiolabeled probe. Taking perchlorate before imaging and drinking more water may help discharge the radioactive uptake in these organs to a certain extent. Blocking imaging studies with excessive unlabeled peptide demonstrated specific affinity of the radiolabeled peptide with liver carcinoma. It is obvious that the unlabeled RRL successfully blocked the radioactive uptake in tumor. The color gradation of tumor was similar with control group. A micro-PET imaging was also included in this study to help identify the diagnostic efficiency of 99mTc-RRL. The average T/M ratio was 6.85, calculated by computer ROI technique. And that was 
similar to the data of experimental group. In this study, we also found the BI-78D3 web linear relationship between the tumor size and tumor uptake by correlation analysis. When tumor is small (,0.05 g), there is little angiogenesis with low blood flow. When tumors are in their rapid growing stage (0.1?.5 g), theFigure 8. Comparison images of nude mice bearing HepG2 cells. In blocking imaging, the tumor on the front right upper JW-74 site extremities was not shown clearly at any time (B), the concentration of 99mTc-RRL only reached a background level. To the contrary, experimental group showed clearly uptake in tumor at 2 h (A). Control group with only injection of free pertechnetate also showed an ambiguous imaging of the tumor (C). Arrows points to tumors on the front right upper extremities. Figure 8E showed imaging position. Figure 8D showed the dissected tumor specimens on the left, and immunohistochemical staining of HE and CD34 in tumors (6200). doi:10.1371/journal.pone.0061043.gA Novel99mTc-Labeled Molecular ProbeFigure 9. 18F-FDG small-animal PET imaging of HepG2 tumor bearing model. Representative images 1326631 confirmed the significant tumor uptake on the front right upper extremities in transverse (A), sagittal (B) and coronal (C) section. doi:10.1371/journal.pone.0061043.gmicrovessel density is high and its ID tumor uptake is high. As a result, the size of tumor was bigger; the tumor uptake of molecular probe was more. Even if the size of tumor was small as 0.12 g, the ID could reach 0.62. Tumor must have sufficient radioactivity counts to be detectable. In this study, we found that tumor of .5 mm in diameter could be visualized with excellent contrast.liver carcinomas. And the application of 99mTc-RRL in diagnosis of different kinds of malignant tumors is expected to explore.AcknowledgmentsWe acknowledge the contributions of our research group of Department of Nuclear Medicine of Peking University First Hospital. We thank Dr. Meng Liu and Dr. Xia Lu for their suggestions in revising of this article.ConclusionThe in vitro stability, biodistribution, and imaging properties of Tc-RRL were evaluated. High tumor uptake and retention suggested that this radiolabeled pep.Beled probe can be particularly accumulated in tumor tissues. In vivo scintigraphic imaging with 99mTc-RRL revealed a higher tumor uptake in the mice bearing HepG2 xenografts. Tumor was imaged clearly, and radiotracer accumulation was also displayed in the kidneys and stomach, and that might indicate the limited application of 99mTc-RRL planar imaging in tumors in these organs. Higher uptake in stomach was observed in both biodistribution analysis and in vivo imaging study. Besides the uptake of free pertechnetate in gastric mucosa, the release of free pertechnetate during catabolism of 25033180 the conjugate in vivo led to a certain degree of catabolic instability of the radiolabeled probe. Taking perchlorate before imaging and drinking more water may help discharge the radioactive uptake in these organs to a certain extent. Blocking imaging studies with excessive unlabeled peptide demonstrated specific affinity of the radiolabeled peptide with liver carcinoma. It is obvious that the unlabeled RRL successfully blocked the radioactive uptake in tumor. The color gradation of tumor was similar with control group. A micro-PET imaging was also included in this study to help identify the diagnostic efficiency of 99mTc-RRL. The average T/M ratio was 6.85, calculated by computer ROI technique. And that was similar to the data of experimental group. In this study, we also found the linear relationship between the tumor size and tumor uptake by correlation analysis. When tumor is small (,0.05 g), there is little angiogenesis with low blood flow. When tumors are in their rapid growing stage (0.1?.5 g), theFigure 8. Comparison images of nude mice bearing HepG2 cells. In blocking imaging, the tumor on the front right upper extremities was not shown clearly at any time (B), the concentration of 99mTc-RRL only reached a background level. To the contrary, experimental group showed clearly uptake in tumor at 2 h (A). Control group with only injection of free pertechnetate also showed an ambiguous imaging of the tumor (C). Arrows points to tumors on the front right upper extremities. Figure 8E showed imaging position. Figure 8D showed the dissected tumor specimens on the left, and immunohistochemical staining of HE and CD34 in tumors (6200). doi:10.1371/journal.pone.0061043.gA Novel99mTc-Labeled Molecular ProbeFigure 9. 18F-FDG small-animal PET imaging of HepG2 tumor bearing model. Representative images 1326631 confirmed the significant tumor uptake on the front right upper extremities in transverse (A), sagittal (B) and coronal (C) section. doi:10.1371/journal.pone.0061043.gmicrovessel density is high and its ID tumor uptake is high. As a result, the size of tumor was bigger; the tumor uptake of molecular probe was more. Even if the size of tumor was small as 0.12 g, the ID could reach 0.62. Tumor must have sufficient radioactivity counts to be detectable. In this study, we found that tumor of .5 mm in diameter could be visualized with excellent contrast.liver carcinomas. And the application of 99mTc-RRL in diagnosis of different kinds of malignant tumors is expected 
to explore.AcknowledgmentsWe acknowledge the contributions of our research group of Department of Nuclear Medicine of Peking University First Hospital. We thank Dr. Meng Liu and Dr. Xia Lu for their suggestions in revising of this article.ConclusionThe in vitro stability, biodistribution, and imaging properties of Tc-RRL were evaluated. High tumor uptake and retention suggested that this radiolabeled pep.
