The Established Nuclear Medicine Modalities for Imaging of Bone Metastases

Targeting bone microenvironments for treatment and early detection of cancer bone metastatic niches

Bone tissues are the main metastatic sites of many cancers, and bone metastasis is an important cause of death. When bone metastasis occurs, dynamic interactions between tumor cells and bone tissues promote changes in the tumor-bone microenvironments that are conducive to tumor growth and progression, which also promote several related diseases, including pathological fracture, bone pain, and hypercalcemia. Accordingly, it has obvious clinical benefits for improving the cure rate and reducing the occurrence of related diseases through targeting bone microenvironments for the treatment and early detection of cancer bone metastasis niches. In this review, we briefly analyzed the relationship between bone microstructures and tumor metastasis, as well as microenvironmental changes in osteoblasts, osteoclasts, immune cells, and extracellular and bone matrixes caused when metastatic tumor cells colonize bones. We also discuss novel designs in nanodrugs for inhibiting tumor proliferation and migration through targeting to tumor bone metastases and abnormal bone-microenvironment components. In addition, related researches on the early detection of bone and multi-organ metastases by nanoprobes are also introduced. And we look forward to provide some useful proposals and enlightenments on nanotechnology-based drug delivery and probes for the treatment and early detection of bone metastasis.

Evaluation of the Small-animal Nano Scan PET/CT System using 89Zr

INTRODUCTION

The purpose of the present work was to evaluate the imaging characteristics of ⁸⁹Zr-PET in comparison with those obtained using fluorine-18 Fluorodeoxyglucose (18FFDG) PET (a gold standard tracer in PET imaging) using a small-animal NanoScan PET/CT scanner.

METHODS

The system's spatial resolution, sensitivity, uniformity, and image quality were measured on a Nano Scan small-animal PET/CT scanner according to the NEMA NU4-2008 protocols. For reconstruction images, we used 2D and 3D reconstruction algorithms. The reconstruction methods included filter back projection (FBP), the ordered subsets expectation maximization (OSEM) algorithm, and the 3D Tera-Tomo algorithm, which are developed for the NanoScan small-animal PET/CT scanner.

RESULTS

The results obtained showed a significant difference in the spatial resolution for ⁸⁹Zr as compared to 22Na and 18F when using a 2D reconstruction algorithm. The spatial resolution values were much enhanced by using the 3D Tera-Tomo reconstruction for each isotope, the Full width at half maximum (FWHM) values was less than 1 for all isotopes at the center of the field of view (FOV). This difference in spatial resolution is dependent on the positron range, energy, and the reconstruction method.

CONCLUSION

The long half-life of ⁸⁹Zr makes it an ideal positron emitter for performing immuno- PET, which is matched with the biological half-life of intact mAbs.⁸⁹Zr can also give several advantages over other long half-life positron emitters in relation to the overall imaging performance because of its relatively short positron range and simpler decay scheme. The values of ⁸⁹Zr sensitivity that were obtained in the present study were less than those of previous studies.