Frequency-dependent optimal weighting approach for megavoltage multilayer imagers.
Frequency-dependent optimal weighting approach for megavoltage multilayer imagers.
复制标题
DOI：
10.1088/1361-6560/abe051
复制
发表时间：
2021-04-16
影响因子：
3.5
通讯作者：
中科院分区：
文献类型：
--
作者：
多层成像（MLI）装置提高了探测量子效率（DQE），同时保持了用于放射治疗的传统超高压（MV） x射线探测器的空间分辨率。迄今为止，只有具有相同探测器层的mli被探索过。然而，可以在每一层中使用不同的闪烁材料来改善最终的图像质量。为此，我们开发并验证了一种方法，该方法可以最佳地组合由异构层构建的MLI设备的每层的单个图像。通过将掺铽氧化硫化钆Gd2O2S:Tb （GOS）荧光粉和LKH-5玻璃闪烁体堆叠不同层，在GATE蒙特卡罗封装内模拟了两种结构。用调制传递函数（MTF）、归一化噪声功率谱（NNPS）和DQE表征检测器响应。然后对每一层的空间频率相关加权因子进行解析推导，从而使总和组合图像的总DQE在所有空间模式下都最大化。最后得到的图像是每一层子图像的加权和。发现使DQE最大化的最优加权因子是异构MLI检测器各层MTF和NNPS的商。结果验证了DQE在整个频域上的改进。对于LKH-5平板配置，DQE(0)增加了2-3%（绝对），而LKH-5像素化配置的相应改进为7%。在2.5 MV和6 MV下，通过空间分辨率、对比噪声比（CNR）和信噪比（SNR）对加权法的性能进行了定量评价。当空间频率大于0.2 lp mm−1时，线对幻像捕获的CNR和SNR增加了两倍，但MTF下降。对于拉斯维加斯幻影，根据对比度区域的不同，加权将CNR提高了约30%，而信噪比值则提高了2.5倍。这些结果表明，采用频率相关加权方案可以提高MLI系统的成像性能。在所有空间尺度上，加权组合图像的信噪比和信噪比都得到了提高，与探测器组合或光子束能量无关。
Multi-layer imaging (MLI) devices improve the detective quantum efficiency (DQE) while maintaining the spatial resolution of conventional mega-voltage (MV) x-ray detectors for applications in radiotherapy. To date, only MLIs with identical detector layers have been explored. However, it may be possible to instead use different scintillation materials in each layer to improve the final image quality. To this end, we developed and validated a method for optimally combining the individual images from each layer of MLI devices that are built with heterogeneous layers. Two configurations were modeled within the GATE Monte Carlo package by stacking different layers of a terbium doped gadolinium oxysulfide Gd2O2S:Tb (GOS) phosphor and a LKH-5 glass scintillator. Detector response was characterized in terms of the modulation transfer function (MTF), normalized noise power spectrum (NNPS) and DQE. Spatial frequency-dependent weighting factors were then analytically derived for each layer such that the total DQE of the summed combination image would be maximized across all spatial modes. The final image is obtained as the weighted sum of the sub-images from each layer. Optimal weighting factors that maximize the DQE were found to be the quotient of MTF and NNPS of each layer in the heterogeneous MLI detector. Results validated the improvement of the DQE across the entire frequency domain. For the LKH-5 slab configuration, DQE(0) increases between 2–3% (absolute), while the corresponding improvement for the LKH-5 pixelated configuration was 7%. The performance of the weighting method was quantitatively evaluated with respect to spatial resolution, contrast-to-noise ratio (CNR) and signal-to-noise ratio (SNR) of simulated planar images of phantoms at 2.5 and 6 MV. The line pair phantom acquisition exhibited a twofold increase in CNR and SNR, however MTF was degraded at spatial frequencies greater than 0.2 lp mm−1. For the Las Vegas phantom, the weighting improved the CNR by around 30% depending on the contrast region while the SNR values are higher by a factor of 2.5. These results indicate that the imaging performance of MLI systems can be enhanced using the proposed frequency-dependent weighting scheme. The CNR and SNR of the weighted combined image is improved across all spatial scales independent of the detector combination or photon beam energy.
登录
查看更多内容
影响因子：
3.8
作者：
Hu YH;Myronakis M;Rottmann J;Wang A;Morf D;Shedlock D;Baturin P;Star-Lack J;Berbeco R
通讯作者：
Berbeco R
影响因子：
3.5
作者：
Rottmann J;Morf D;Fueglistaller R;Zentai G;Star-Lack J;Berbeco R
通讯作者：
Berbeco R
影响因子：
3.5
作者：
Jan, S.;Benoit, D.;Buvat, I.
通讯作者：
Buvat, I.
影响因子：
10.6
作者：
FUJITA, H;TSAI, DY;OHTSUKA, A
通讯作者：
OHTSUKA, A
DOI：
10.1016/j.ejmp.2013.07.127
发表时间：
2014-03-01
影响因子：
3.4
作者：
Rucci, Alexis;Carletti, Claudia;Strbac, Bojan
通讯作者：
Strbac, Bojan