Abstract
Single-photon-emission computed tomography (SPECT) and positron-emission tomography (PET) are highly sensitive molecular detection and imaging techniques that generally measure accumulation of radio-labeled molecules by detecting gamma rays. Quantum sensing of local molecular environment via spin, such as nitrogen vacancy (NV) centers, has also been reported. Here, we describe quantum sensing and imaging using nuclear-spin time-space correlated cascade gamma-rays via a radioactive tracer. Indium-111 (111In) is widely used in SPECT to detect accumulation using a single gamma-ray photon. The time-space distribution of two successive cascade gamma-rays emitted from an 111In atom carries significant information on the chemical and physical state surrounding molecules with double photon coincidence detection. We propose and demonstrate quantum sensing capability of local micro-environment (pH and chelating molecule) in solution along with radioactive tracer accumulation imaging, by using multiple gamma-rays time-and-energy detection. Local molecular environment is extracted through electric quadrupole hyperfine interaction in the intermediate nuclear spin state by the explicit distribution of sub-MeV gamma rays. This work demonstrates a proof of concept, and further work is necessary to increase the sensitivity of the technique for in vivo imaging and to study the effect of scattered radiation for possible application in nuclear medicine.
Highlights
Single-photon-emission computed tomography (SPECT) and positron-emission tomography (PET) are highly sensitive molecular detection and imaging techniques that generally measure accumulation of radio-labeled molecules by detecting gamma rays
In the 1970s, some studies revealed the correlation of the external field environment and its emission through electric quadrupole interaction via nuclear spin with one simple coincidence detector[22,23] and suggested possible biological applications; there have been no studies on simultaneous imaging and quantum sensing of pH and other molecular environments
DPECT imaging localizes the radioactive tracer position with a single coincidence event compared with conventional SPECT, which typically requires the rotation of detectors
Summary
Single-photon-emission computed tomography (SPECT) and positron-emission tomography (PET) are highly sensitive molecular detection and imaging techniques that generally measure accumulation of radio-labeled molecules by detecting gamma rays. DPECT imaging localizes the radioactive tracer position with a single coincidence event compared with conventional SPECT, which typically requires the rotation of detectors These methods have only been used to detect the accumulation of radio-labeled molecules, and local molecular environment sensing was not investigated. With multiple-dimension gamma-rays decay detection techniques combined with nuclear spin, we propose local environment quantum sensing, such as pH or chemical state, and its simultaneous imaging using cascade decay radioactive nuclide. We characterized the distribution of gamma-ray time-space distribution in several different local environments surrounding molecules by developed ring-shaped detectors and demonstrated the imaging capability of clinically available 111In SPECT nuclearmedicine tracer together with pH and chelating molecule sensing This simultaneous imaging and quantum sensing will provide nuclear-medicine diagnosis with local molecular environment sensing and a platform of quantum sensing in medical diagnosis with naturally polarized photons via nuclear spin. This work demonstrates a proof of concept, and further work is necessary to increase the sensitivity of the technique for in vivo imaging and to study the effect of scattered radiation for possible application in nuclear-medicine
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