Investigation of the potential application of rhenium in medical imaging

Many thermodynamically stable coordination compounds have been synthesized using rhenium, a chemically versatile transition metal. Some of these rhenium complexes have been studied for utilization in nuclear medicine. However, many of their applications in medical imaging remain relatively unexplored and require further investigation. A comprehensive study was conducted in preclinical and clinical X-ray equipment to examine the use of rhenium as a contrast agent for X-ray imaging. Usually, there is a trade-off between image quality and radiation dose. This experimental work, along with theoretical Monte Carlo calculations, showed that it is feasible to preserve image quality and minimize radiation dose simultaneously when a rhenium-based formulation is utilized. This research provided thorough evidence of rhenium’s usefulness in X-ray imaging. Another application of rhenium was evaluated by producing a radiopaque, biodegradable electrospun scaffold containing a rhenium complex. Typically, catheterizations are performed under X-ray imaging guidance, but most catheters are radiolucent. After coating catheters with this scaffold, they became strongly radiopaque. Even a thin rhenium-doped coating has the potential of enhancing the contrast during catheterizations, which might be helpful in placing catheters more rapidly and precisely. Not only large medical devices, but also microsized carriers can be made radiopaque. An issue with embolic microspheres is their lack of contrast. To improve their visibility, potentially toxic contrast agents are co-administered in X-ray imaging-guided embolotherapy. Using a microfluidic technology, radiopaque, biodegradable microspheres made of a custom-synthesized polymer containing a rhenium complex were produced. Upon increasing the polymer’s rhenium concentration, these microspheres could be utilized in embolotherapy. Rhenium’s radioisotope Re¹⁸⁸ is a mixed beta and gamma emitter and can thus be exploited in another imaging modality: single photon emission computed tomography (SPECT). The biodistribution of microspheres labeled with Re¹⁸⁸ was evaluated in a hepatocellular carcinoma-bearing rat model. Although challenging in clinical practice, the radiation doses to the tumor and the healthy liver tissue were calculated. The radiation dose from the beta emissions yields these “imageable” microspheres theranostic, with quantifiable cancer radiotherapeutic potential. This work established the foundations to guide further research on the development of biodegradable devices doped with rhenium for medical imaging.Pharmaceutical Sciences, Faculty ofGraduat