ACRF Image X Institute, The University of Sydney, New South Wales, Australia.
Liverpool & Macarthur Cancer Therapy Centres, Liverpool Hospital, Liverpool, New South Wales, Australia.
Phys Med Biol. 2021 Mar 23;66(7). doi: 10.1088/1361-6560/abebfb.
Conventional 4DCBCT captures 1320 projections across 4 min. Adaptive 4DCBCT has been developed to reduce imaging dose and scan time. This study investigated reconstruction algorithms that best complement adaptive 4DCBCT acquisition for reducing imaging dose and scan time whilst maintaining or improving image quality compared to conventional 4DCBCT acquisition using real patient data from the first 10 adaptive 4DCBCT patients. Adaptive 4DCBCT was implemented in the ADaptive CT Acquisition for Personalized Thoracic imaging clinical trial. Adaptive 4DCBCT modulates gantry rotation speed and kV acquisition rate in response to the patient's real-time respiratory signal, ensuring even angular spacing between projections at each respiratory phase. We examined the first 10 lung cancer radiotherapy patients that received adaptive 4DCBCT. Fast, 200-projection scans over 60-80 s, and slower, 600-projection scans over ∼240 s, were obtained after routine patient treatment and compared against conventional 4DCBCT acquisition. Adaptive 4DCBCT acquisitions were reconstructed using Feldkamp-Davis-Kress (FDK), McKinnon-Bates (MKB), Motion Compensated FDK (MCFDK) and Motion Compensated MKB (MCMKB) algorithms. Reconstructions were assessed via, Structural SIMilarity (SSIM), Signal-to-Noise-Ratio (SNR), Contrast-to-Noise-Ratio (CNR), Tissue Interface Sharpness of Diaphragm (TIS-D) and Tumor (TIS-T). The 200- and 600-projection adaptive 4DCBCT acquisition corresponded to 85% and 55% reduction in imaging dose, shorter and similar scan times of approximately 90 s and 236 s respectively, compared to conventional 4DCBCT acquisition. 200- and 600-projection adaptive 4DCBCT reconstructions achieved more than 0.900 SSIM relative to conventional 4DCBCT acquisition. Compared to conventional 4DCBCT acquisition, 200-projection adaptive 4DCBCT reconstructions achieved higher SNR, CNR, TIS-T, TIS-D with motion compensated algorithms, MCFDK (208%, 159%, 174%, 247%) and MCMKB (214%, 173%, 266%, 245%) respectively. The 200-projection adaptive 4DCBCT MCFDK- and MCMKB-reconstruction results show image quality improvements are possible even with 85% fewer projections acquired. We established acquisition-reconstruction protocols that provide substantial reductions in imaging time and dose whilst improving image quality.
传统的 4D CBCT 在 4 分钟内采集 1320 个投影。自适应 4D CBCT 的开发旨在降低成像剂量和扫描时间。本研究使用来自前 10 名接受自适应 4D CBCT 的肺癌放疗患者的真实患者数据，调查了最佳补充自适应 4D CBCT 采集以降低成像剂量和扫描时间的重建算法，同时与使用常规 4D CBCT 采集相比，保持或提高图像质量。自适应 4D CBCT 在 ADaptive CT Acquisition for Personalized Thoracic imaging 临床试验中实施。自适应 4D CBCT 根据患者的实时呼吸信号调节机架旋转速度和 kV 采集率，确保在每个呼吸阶段的投影之间具有均匀的角间距。我们检查了前 10 名接受自适应 4D CBCT 的肺癌放疗患者。在常规患者治疗后获得了 60-80 秒的快速 200 个投影扫描和 240 秒左右的较慢 600 个投影扫描，并与常规 4D CBCT 采集进行了比较。自适应 4D CBCT 采集使用 Feldkamp-Davis-Kress (FDK)、McKinnon-Bates (MKB)、Motion Compensated FDK (MCFDK) 和 Motion Compensated MKB (MCMKB) 算法进行重建。通过结构相似性 (SSIM)、信噪比 (SNR)、对比度噪声比 (CNR)、膈肌组织界面锐度 (TIS-D) 和肿瘤 (TIS-T) 评估重建。与常规 4D CBCT 采集相比，200 个和 600 个投影自适应 4D CBCT 采集的成像剂量分别降低了 85%和 55%，扫描时间分别缩短了约 90 秒和 236 秒。与常规 4D CBCT 采集相比，200 个和 600 个投影自适应 4D CBCT 重建的 SSIM 均大于 0.900。与常规 4D CBCT 采集相比，200 个投影自适应 4D CBCT 重建的运动补偿算法 MCFDK（208%、159%、174%、247%）和 MCMKB（214%、173%、266%、245%）实现了更高的 SNR、CNR、TIS-T 和 TIS-D。即使采集的投影减少了 85%，200 个投影自适应 4D CBCT 的 MCFDK 和 MCMKB 重建结果也显示出图像质量的改善是可能的。我们建立了采集-重建协议，可在大幅减少成像时间和剂量的同时提高图像质量。
