Nuclear medicine relies on two imaging modalities to assess internal function and diagnose disease. Positron emission tomography (PET) typically uses fluorine-18, a radiotracer that releases positrons, and a special scanner to detect the resulting gamma rays. Single-photon emission computed tomography (SPECT) is similar, but usually depends on injecting the technetium-99m radioisotope and a gamma camera to detect where it goes in the body. Each modality has its benefits and drawbacks, and comparisons between the two may provide interesting insights and clinical consequences for nuclear medicine. However, it is currently impossible to perform a simultaneous PET/SPECT scan.
Now, researchers at the Kavli Institute for the Physics and Mathematics of the Universe in Japan have developed a semiconductor-based silicon/cadmium telluride (Si/CdTe) Compton camera that can detect fluorine-18 and technetium-99m at the same time, something they’ve already tested on an adult volunteer.
Compton cameras were originally designed for astronomy as a way to detect gamma rays and the technology inside this latest device was developed for Japan Aerospace Exploration Agency (JAXA).
Using the new device, the Kavli team can specify the energy windows for their device to look at and create 3D models of the distribution of the two radiotracers inside the body of a volunteer. These maps are then overlaid onto a CT scan of the same volunteer to give context to where the radioactive particles traveled.
Indeed, the kidneys and liver lit up on the scans, but the distribution was different, an expected finding that confirmed that the system was functioning properly.
The researchers hope that their technology will open up a new sub-field within nuclear medicine and perhaps even allow for the introduction of alternative radiotracers, as their camera can be tuned to detect different gamma ray energies.
Top image: (Left) an image of gamma rays with energy of 141 keV from 99mTc-DMSA, and (right) an image of gamma rays with energy of 511 keV from 18F-FDG detected at the same time using the Compton camera. (Credit: Nakano et al.)
Study in Physics in Medicine & Biology: Imaging of 99mTc-DMSA and 18F-FDG in humans using a Si/CdTe Compton camera
Via: Kavli Institute