Development of a small prototype for a proof-of-concept of OpenPET imaging

Abstract

The OpenPET geometry is our new idea to visualize a physically opened space between two detector rings. In this paper, we developed the first small prototype to show a proof-of-concept of OpenPET imaging. Two detector rings of 110 mm diameter and 42 mm axial length were placed with a gap of 42 mm. The basic imaging performance was confirmed through phantom studies; the open imaging was realized at the cost of slight loss of axial resolution and 24% loss of sensitivity. For a proof-of-concept of PET image-guided radiation therapy, we carried out the in-beam tests with (11)C radioactive beam irradiation in the heavy ion medical accelerator in Chiba to visualize in situ distribution of primary particles stopped in a phantom. We showed that PET images corresponding to dose distribution were obtained. For an initial proof-of-concept of real-time multimodal imaging, we measured a tumor-inoculated mouse with (18)F-FDG, and an optical image of the mouse body surface was taken during the PET measurement by inserting a digital camera in the ring gap. We confirmed that the tumor in the gap was clearly visualized. The result also showed the extension effect of an axial field-of-view (FOV); a large axial FOV of 126 mm was obtained with the detectors that originally covered only an 84 mm axial FOV. In conclusion, our initial imaging studies showed promising performance of the OpenPET.

System design of a small OpenPET prototype with 4-layer DOI detectors

“…The DOI detector was designed with the high priority for optimization of in-beam PET. As a result, the small OpenPET prototype has operated of a stable condition during the 11 C irradiation [13].…”

“…In a previous report [13], the coincidence window of the small OpenPET prototype was set at 60 ns, because the timing histogram had a broad distribution. However, random coincidences give a nearly undetectable count rate for in-beam PET experiments, because the activity due to irradiation is low.…”

“…We have developed and evaluated a small OpenPET prototype that uses 4-layer DOI detectors [10], which offers the promise of high sensitivity (6.5% system sensitivity) and high spatial resolution (about 2 mm full width at half maximum (FWHM)) [13]. The system design of the small OpenPET prototype has been optimized for in-beam PET experiments.…”

Imaging particle beams for cancer treatment

“…Furthermore, physiological processes such as blood flow cause some of the positron emitters to diffuse away from the treatment area over time and thus spoil the physical correlation between treatment delivery and measured activity. Researchers are working to develop both modern in-beam PET instrumentation tailored to in vivo beam-range verification 7,8 and computerassisted tools for adjusting the treatment plan when PET detects an offset between the delivered and intended beam ranges.…”

Signal pulse emulation for scintillation detectors using Geant4 Monte Carlo with light tracking simulation

“…Recently, PSD analysis has been applied for a depth-of-interaction (DOI) detector in a small positron emission tomography (PET) device aiming at the improvement of image quality. 9 The DOI detector consists of a multilayered scintillator with different scintillation properties. 10,11 Moreover, a phoswich (phosphor sandwich) detector which consists of a few scintillators identifies an incident particle type by PSD analysis in a common readout, 12 and applies a background rejection method using anti-Compton analysis.…”