Double bowtie design for high sensitivity pediatric spectral CT

Despite the evident benefits of spectral computed tomography (CT) in delivering qualitative imaging superior to that of conventional CT in adults, its application in pediatric diagnostic imaging is still relatively limited due to various reasons, including design limitations and radiation dose considerations. The use of specialized K-edge filters, in conjunction with other spectral technologies, has been demonstrated to improve spectral quantification accuracy. X-ray flux limitations generally pose challenges in these concepts when applied to adults. However, such limitations are not present in pediatric imaging, allowing the full exploitation of K-edge filters to improve performance. To facilitate the adoption of spectral CT's benefits, as seen in the adult population, into pediatric settings, we introduce an innovative double bowtie filter design. This design incorporates a K-edge material coupled with Teflon and is integrated with rapid kVp-switching technology. A Python simulation was built to model a rapid kVp-switching x-ray tube and to estimate Cramer-Rao lower bound (CRLB) noise in photoelectric and Compton scatter basis domains. We estimate a conventional bowtie filter and corresponding reference patient dose before optimizing double bowtie configurations to contain the highest obtainable spectral signal-to-noise content for the specified phantom. Our findings indicate that an optimal combination of holmium and Teflon in the filter geometry can increase spectral SNR up to twofold the conventional estimates, while still maintaining low radiation dose exposure. This study broadens the scope for pediatric patients to fully benefit from the capabilities of spectral CT.