Speaker
Description
The combination of scintigraphy and fluoroscopic X-ray imaging enables shorter and easier interventional procedures involving radionuclides, such as radio embolization. As a result of the simultaneous acquisition of anatomical and nuclear information, this could reduce the burden for the patient and simplify hospital logistics. While various multimodal imaging techniques are already available and in use \cite{cherry2009multimodality}, this new approach mounts a gamma camera directly behind a flat-panel X-ray detector on a clinical C-arm \cite{van2019dual}. Advantages of this hybrid C-arm for interventional x-ray and scintigraphy imaging (IXSI) include a compact design and a naturally good image alignment. However, several shortcomings still need to be addressed, especially the X-ray induced blinding effects in the gamma camera \cite{koppert2018impact}. To this day, most clinical gamma cameras use NaI(Tl) as the scintillator. This material has a relatively high afterglow, which gives rise to a background signal following each X-ray pulse. This high background obscures the signal generated by the gamma photons, which are emitted by the radionuclide \cite{koppert2019comparative}. Thus, this research focuses on finding a scintillator with similar attributes as NaI(Tl) but with lower afterglow.
To find such, a series of GATE simulations of the IXSI hybrid C-arm detector were performed, in which the energy deposition in the gamma camera due to a typical X-ray-scan was calculated for twelve different scintillation materials. From the X-ray energy deposition within each type of crystal, the scintillation light emission and afterglow could be estimated. The afterglow intensity was subsequently compared to the light signal generated by a single $140\,\mathrm{keV}$ photon in the same scintillation material, by calculating the ratio of the light yields due to the $140\,\mathrm{keV}$ photon and the afterglow at $100\,\mathrm{ms}$ after the X-ray pulse. The five scintillators with the highest signal-to-background ratios were chosen for further in-house testing. These were CeBr3, CdWO4, NaI(Tl, Y, Sr), NaI(Tl, Sr) and CsI(Tl, Sb, Bi). From these, NaI(Tl, Y, Sr), NaI(Tl, Sr) and CsI(Tl, Sb, Bi) are newly developed materials. The in-house measurements will at least consist of afterglow-, decay-time- and energy-resolution-measurements.
Extensive results from the simulation and results from the in-house measurements will be presented at the conference.
\begin{figure}[ht]
\begin{minipage}[c]{0.4\linewidth}
\includegraphics[width=\linewidth]{Screenshot from 2024-03-18 16-10-21.png}
\caption{Simulated 'IXSI' hybrid C-arm detector prototype in Gate9.2.}
\end{minipage}
\hfill
\begin{minipage}[c]{0.4\linewidth}
\includegraphics[width=\linewidth]{Edep-Analyse.png}
\caption{Afterglow from an X-ray pulse for various scintillators (solid lines) and the corresponding light yields for one incident $140\,\mathrm{keV}$ photon (dashed horizontal lines).}
\end{minipage}%
\end{figure}
