Department of Medical Physics, Fakultät für Physik, Ludwig-Maximilians-Universität München (LMU Munich), Am Coulombwall 1, Garching bei München, Germany.
Department of Physics, Northern Illinois University, 1425 W. Lincoln Highway, DeKalb, IL, United States.
Phys Med. 2021 Jan;81:237-244. doi: 10.1016/j.ejmp.2020.12.012. Epub 2021 Jan 20.
To reduce imaging artifacts and improve image quality of a specific proton computed tomography (pCT) prototype scanner by combining pCT data acquired at two different incident proton energies to avoid protons stopping in sub-optimal detector sections.
Image artifacts of a prototype pCT scanner are linked to protons stopping close to internal structures of the scanner's multi-stage energy detector. We aimed at avoiding such protons by acquiring pCT data at two different incident energies and combining the data in post-processing from which artifact-reduced images of the relative stopping power (RSP) were calculated. Energy-modulated pCT (EMpCT) images were assessed visually and quantitatively and compared to the original mono-energetic images in terms of RSP accuracy and noise. Data were acquired for a homogeneous water phantom.
RSP images reconstructed from the mono-energetic datasets displayed local image artifacts which were ring-shaped due to the homogeneity of the phantom. The merged EMpCT dataset achieved a superior visual image quality with reduced artifacts and only minor remaining rings. The inter-quartile range (25/75) of RSP values was reduced from 0.7% with the current standard acquisition to 0.2% with EMpCT due to the reduction of ring artifacts. In this study, dose was doubled compared to a standard scan, but we discuss strategies to reduce excess dose.
EMpCT allows to effectively avoid regions of the energy detector that cause image artifacts. Thereby, image quality is improved.
通过将在两种不同入射质子能量下采集的 pCT 数据进行组合，避免质子在探测器的非最佳部分停止，从而减少特定质子计算机断层扫描（pCT）原型扫描仪的成像伪影并提高图像质量。
原型 pCT 扫描仪的图像伪影与靠近扫描仪多级能量探测器内部结构停止的质子有关。我们的目标是通过在两种不同的入射能量下采集 pCT 数据，并在后期处理中对数据进行组合，从而计算出相对阻止本领（RSP）的图像伪影减少，以避免这种质子。对能量调制 pCT（EMpCT）图像进行了视觉和定量评估，并在 RSP 准确性和噪声方面与原始单能图像进行了比较。数据是在均匀水模体上采集的。
从单能数据集重建的 RSP 图像显示出局部图像伪影，由于水模体的均匀性，这些伪影呈环形。合并后的 EMpCT 数据集具有更好的视觉图像质量，减少了伪影，仅留下少量残余的环。RSP 值的四分位数范围（25/75）从当前标准采集的 0.7%降低到 EMpCT 的 0.2%，这是由于环形伪影的减少。在本研究中，与标准扫描相比，剂量增加了一倍，但我们讨论了降低过量剂量的策略。
EMpCT 可有效避免导致图像伪影的能量探测器区域。从而提高了图像质量。
