Experimental comparison of photon versus particle computed tomography to predict tissue relative stopping powers
Experimental comparison of photon versus particle computed tomography to predict tissue relative stopping powers
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DOI：
10.1002/mp.15283
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发表时间：
2021-11-16
期刊：
影响因子：
3.8
通讯作者：
Seco, Joao
中科院分区：
文献类型：
--
作者：
Bar, Esther;Volz, Lennart;Seco, Joao
目的：测量结果比较了最先进系统的相对阻止本领（RSP）准确度，这些系统代表单能量和双能量计算机断层扫描（SECT/DECT）与质子CT（pCT）和氦CT（HeCT）在生物组织样本中的表现。方法：我们使用了16份不同组织类型的猪和牛样本和水，RSP范围为0.90 +/- 0.06至1.78 +/- 0.05。将样品包装并密封在3D打印的圆柱体（d=2 cm，h=5 cm）中，并插入内部设计的圆柱形聚甲基丙烯酸甲酯（PMMA）体模（d=10 cm，h=10 cm）中。我们在商业SECT和DECT（120 kV; 100和140 kV/Sn（锡过滤））中扫描体模;并使用粒子成像原型采集pCT和HeCT（E类似于200 MeV/u，2个圆步长，类似于6.2x106（p）/类似于2.3x106（He）粒子/投影）。使用化学计量方法从SECT/DECT和使用DROP-TVS算法从pCT/HeCT计算RSP图。我们估计了感兴趣的圆柱体中每个模态的每个组织的平均RSP，并将其与从峰值检测测量中获取的地面真实RSP进行比较。结果如下：在所有样本中，我们观察到以下均方根RSP预测误差+/-参考测量和成像的组合不确定度：SECT 3.10 +/-2.88%，DECT 0.75 +/-2.80%，pCT 1.19 +/-2.81%和HeCT 0.78 +/-2.81%。每种模态的最大平均误差+/-组合不确定度为：皮质骨中SECT 8.22 +/- 2.79%，背部脂肪中DECT 1.74 +/- 2.00%，骨髓中pCT 1.80 +/- 4.27%，骨髓中HeCT 1.37 +/- 4.25%。在pCT和HeCT重建中均观察到环形伪影，对预测的RSP施加了系统性偏移。结论：比较最先进的SECT/DECT技术和pCT/HeCT原型，DECT提供了最准确的RSP预测，紧随其后的是粒子成像。新的模式pCT和HeCT有可能进一步提高RSP的准确性，工作重点是环形伪影的起源和校正。未来的工作将使用来自研究成像模式的RSP图研究质子治疗计划的准确性。
Purpose: Measurements comparing relative stopping power (RSP) accuracy of state-of-the-art systems representing single-energy and dual-energy computed tomography (SECT/DECT) with proton CT (pCT) and helium CT (HeCT) in biological tissue samples. Methods: We used 16 porcine and bovine samples of various tissue types and water, covering an RSP range from 0.90 +/- 0.06 to 1.78 +/- 0.05. Samples were packed and sealed into 3D-printed cylinders (d=2 cm, h=5 cm) and inserted into an in-house designed cylindrical polymethyl methacrylate (PMMA) phantom (d=10 cm, h=10 cm). We scanned the phantom in a commercial SECT and DECT (120 kV; 100 and 140 kV/Sn (tin-filtered)); and acquired pCT and HeCT (E similar to 200 MeV/u, 2 circle steps, similar to 6.2x106 (p)/similar to 2.3x106 (He) particles/projection) with a particle imaging prototype. RSP maps were calculated from SECT/DECT using stoichiometric methods and from pCT/HeCT using the DROP-TVS algorithm. We estimated the average RSP of each tissue per modality in cylindrical volumes of interest and compared it to ground truth RSP taken from peak-detection measurements. Results: Throughout all samples, we observe the following root-mean-squared RSP prediction errors +/- combined uncertainty from reference measurement and imaging: SECT 3.10 +/- 2.88%, DECT 0.75 +/- 2.80%, pCT 1.19 +/- 2.81%, and HeCT 0.78 +/- 2.81%. The largest mean errors +/- combined uncertainty per modality are SECT 8.22 +/- 2.79% in cortical bone, DECT 1.74 +/- 2.00% in back fat, pCT 1.80 +/- 4.27% in bone marrow, and HeCT 1.37 +/- 4.25% in bone marrow. Ring artifacts were observed in both pCT and HeCT reconstructions, imposing a systematic shift to predicted RSPs. Conclusion: Comparing state-of-the-art SECT/DECT technology and a pCT/HeCT prototype, DECT provided the most accurate RSP prediction, closely followed by particle imaging. The novel modalities pCT and HeCT have the potential to further improve on RSP accuracies with work focusing on the origin and correction of ring artifacts. Future work will study accuracy of proton treatment plans using RSP maps from investigated imaging modalities.