TY - JOUR
T1 - Dark Matter Search Application to Medical Physics
T2 - 2021 European Physical Society Conference on High Energy Physics, EPS-HEP 2021
AU - Lai, M.
AU - Ramirez, A.
AU - Li, X.
AU - Renshaw, A.
AU - Wada, M.
AU - Zabihi, A.
AU - Franco, D.
AU - Gabriele, F.
AU - Galbiati, C.
AU - Wang, H.
N1 - Funding Information:
The expected signal from a patient is back-to-back 511 keV gamma particles. A gamma scattering in liquid Argon has a probability of 70% to excite the triplet state, which is forbidden at dipole momentum and hence yields a significantly long average time-decay of 1.6 us; this can be compared with the remaining 30% of Argon excimers, which are excited into the allowed singlet state that has an average time decay of only 6 ns. While for dark matter searches this is the key to distinguish most of the local backgrounds from a potential dark matter signal [5, 10], in the case of a PET scanner this widens the trigger circuit coincidence window, decreasing the signal-to-noise ratio. Furthermore, the increase of the coincidence circuit time window also increases the dead-time of the acquisition; thus affecting the sensitivity of the scanner. As a solution, the presented design also assumes the replacement of the TPB with the addition of 0.5 % of Xenon into the liquid Argon, since it then shifts the average triplet state time decay down to about 100 ns, resulting in an overall scintillation time comparable with the ones observed in traditional scintillating crystals. 3. First Results From Quality Checks The performance of the 3DΠ scanner has been tested according to NEMA-NU-2018 [11] document, which provides experimental tests to benchmark the performance of a PET scanner as well as standards to adhere. The preliminary results come from tests based on the GEANT4 simulation of the 3DΠ scanner. The sensitivity of a PET scanner is defined as the number of detected counts per unit time and per unit of activity of the source. A line source was simulated, completely wrapped in an attenuating sleeve of aluminum with varying thickness. This allows for fitting the count rate as a function of sleeve thickness; the limit for null thickness is the sensitivity, which was evaluated to be 505 cps/kBq for the design of the 3DΠ scanner using liquid Argon and TPB. A slight increase to 513 cps/kBq is observed for the second possible design, with Xenon doped liquid Argon and the absence of TPB. In both cases, the detector shows an outstanding sensitivity, approximately one order of magnitude higher than that achieved by average commercial technologies. The spatial resolution is evaluated by setting a point-like source in six different positions within a water phantom, in order to report the spatial resolution along both the axial direction and the radial one. While the Argon-only design shows on average a spatial resolution of about 10 mm, the Argon plus Xenon design shows an improvement, reducing down to about 5 mm in each direction, which is comparable with the spatial resolution from commercial scanners. The resolution has been evaluated after reconstructing the image with the filtered back-projection, although an improvement of the spatial resolution is expected by using an interactive algorithm for the image reconstruction. On the other hand, the contribution to the spatial resolution due to the time resolution shows to be very promising, estimated at about 100 ps from a preliminary evaluation. Both of these results suggest an extraordinary performance on the image quality test as specified in NEMA-NU-2018. The recommended phantom in this test is a water sphere with six radiation sources located at the same radius from the center, as shown in Figure 1 (right side) for the configuration in Argon doped with Xenon. According to the preliminary results, the quality of an image acquired in 30 minutes from commercial scanners is comparable with an image acquired by 3DΠ in only ∼15 s. Thanks to the increase in sensitivity, the 3DΠ scanner provides an advantage compared to commercial scanners, since it can provide similar detailed images in much shorter times, or much more detailed images across a similar time. As an alternative, the increase in the sensitivity can instead be used to decrease the dose of the radiotracer in the patient. Patients who have previously been barred from PET scanners due to radiation safety limits, such as children and pregnant women, could then have access to PET imaging. 4. Acknowledgments This work has been supported by the National Science Foundation (NSF) Graduate Research Fellowship under Grant No. 1746046, the University of Houston’s High Performance Cluster under NSF Grant No. 1531814. Also, it was performed with the support by IRAP AstroCeNT funded by FNP from ERDF and with the support by "Fondazione CON IL SUD" Grant No. 2018-PDR-01005.
Publisher Copyright:
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PY - 2021
Y1 - 2021
N2 - 3D? will be the first total-body scanner for Positron Emission Tomography (PET) using liquid Argon as a scintillator medium. The project is an application in medical physics of the ongoing R&D of the DarkSide collaboration, whose main aim is the direct detection of dark matter particles via liquid Argon targets. Utilizing liquid Argon as a scintillator will allow for a competitive and cost-effective total-body PET scanner to be built, thanks to the high availability of atmospheric Argon that can be isotopically distilled as needed, along with potential for the availability of underground Argon. The preliminary results here demonstrate that, while the spatial resolution is comparable to that of commercial scanners, the 3D? scanner is expected to show outstanding detection sensitivity, allowing for a reduction of the PET scanning time or a reduction of the patient dose.
AB - 3D? will be the first total-body scanner for Positron Emission Tomography (PET) using liquid Argon as a scintillator medium. The project is an application in medical physics of the ongoing R&D of the DarkSide collaboration, whose main aim is the direct detection of dark matter particles via liquid Argon targets. Utilizing liquid Argon as a scintillator will allow for a competitive and cost-effective total-body PET scanner to be built, thanks to the high availability of atmospheric Argon that can be isotopically distilled as needed, along with potential for the availability of underground Argon. The preliminary results here demonstrate that, while the spatial resolution is comparable to that of commercial scanners, the 3D? scanner is expected to show outstanding detection sensitivity, allowing for a reduction of the PET scanning time or a reduction of the patient dose.
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M3 - Conference article
AN - SCOPUS:85129402458
SN - 1824-8039
VL - 398
JO - Proceedings of Science
JF - Proceedings of Science
M1 - 778
Y2 - 26 July 2021 through 30 July 2021
ER -