VIDEO: 6 key advances in molecular imaging technology for PET and SPECT

"It is always tricky to predict the future of these technologies, but two that have seemed to catch a lot of momentum are FAPI agents and immune PET," Ghesani said

1. FAPI PET/CT shows promise as a better radiotracer for cancer than 18F-FDG

Fibroblast activation protein (FAP) is overexpressed in cancer-associated fibroblasts of several types of tumors. FAP is highly expressed in cancer-associated fibroblasts (CAFs) in more than 90% of epithelial tumors and contributes to progression and worse prognosis of different cancers.[1] Therefore, FAP is considered a promising target for radionuclide-based approaches for the diagnosis and treatment of tumors and for the diagnosis of non-malignant diseases associated with a remodeling of the extracellular matrix. 

A variety of quinolone-based FAP inhibitors (FAPI) coupled to chelators are being developed with specific binding to human and murine FAP with a rapid and almost complete internalization. Due to this high tumor uptake and a very low accumulation in normal tissues, combined with rapid clearance from the circulation, a high-contrast is obtained for FAPI-PET/CT imaging even at 10 minutes after tracer administration.[1] Moreover, FAPI-PET/CT provides advantages over FDG-PET/CT in several tumor types for initial staging and detection of tumor recurrence and metastases.

"These agents have applicability in multiple disease states, and not only with various cancers, but also outside of cancer to image infection and inflammation," Ghesani said. "So that might be an exciting new frontier."

Also, in contrast to today's standard of 18F-FDG imaging, no diet or fasting in preparation for the examination is necessary, and image acquisition can potentially be started a few minutes after tracer application. Tumor-to-background contrast ratios were equal to or even better than those of 18F-FDG.[1]

2. Immuno-PET imaging better at tracking cancer treatment effectiveness

Selection of the right drug for the right patient is a promising approach to increase clinical benefit of targeted therapy with monoclonal antibodies. Immune PET imaging allows assessment of the in vivo biodistribution and tumor targeting of these agents to predict toxicity and efficacy to guide personalized treatment and drug development. Molecular imaging with radio-labeled monoclonal antibodies allows visualization and quantification of the tracer uptake, providing an imaging biomarker to assess target expression and tumor targeting.

"This will help us not only on the diagnostic side, but also on the theragnostics side. This is very promising," he explained. 

3. Movement to digital detectors and replacing photomultiplier tubes

Over the past several years, photomultiplier tube (PMT) technology has been replaced with digital detectors. The digital detectors convert photons directly into electrical signals and eliminate the intermediate steps of imaging a flash of light to convert into an electrical signal. This improves image quality, sensitivity of the detector while also reducing the size and weight of scanner systems. 

4. Expansion of the Z-axis so a patient can be imaged head-to-toe in a single scan

Several vendors have expanded the ability of their scanners to scan a much longer field of view, now allowing head-to-toe imaging in a single scan. This allows for a reduction in radiotracer dose and exam time.

5. New radiopharmaceuticals being developed

Ghesani said at the SNMMI annual meeting, there were several sessions on new biomarkers vendors are developing for nuclear imaging. He said the U.S. Food and Drug Administration (FDA) sees the promise to improve care with the prognostic value in these biomarkers and is integrating them into its approval process to help speed access on the market. "These technologies will be playing an increasing role," he explained.

6. Movement to iterative reconstruction

Vendors have moved from filtered back projection (FBP) image reconstruction to iterative reconstruction algorithms in recent years. This enables clearer images and better noise reduction. 

The combination of these technologies has renewed interest in purchasing new nuclear imaging systems, both PET and SPECT. 

"SPECT CT is re-emerging because the technology has changed quite significantly," Ghesani explained.