177Lu CZT SPECT/CT图像重建参数优化：基于体模的恢复系数研究

Optimization of reconstruction parameters in 177Lu CZT SPECT/CT: a phantom study of recovery coefficients

    摘要
  • 摘要:
    目的  基于177Lu 碲锌镉(CZT) SPECT/CT体模采集，筛选最佳重建参数以提高图像质量及最佳恢复系数（RC），为临床诊断及剂量学评估提供依据。
    方法  使用Discovery NM/CT 670型 CZT双探头SPECT/CT扫描仪采集177Lu的113 keV能峰图像。图像重建采用有序子集最大期望值法（OSEM），探究迭代次数（1~90次）及子集数（2~20）对图像RC及图像质量的影响，并联合衰减校正（AC）、分辨率恢复（RR）及散射校正（SC）确定最佳校正方案；在上述参数固定的前提下，改变每帧采集时间（10、15、20 s/帧），探究采集时间对图像RC的影响。通过RC及图像质量评分来评估重建参数性能。不同校正方法间RC的比较采用单因素方差分析，组间两两比较采用Tukey多重比较检验；采用Pearson相关性分析评估RC与迭代次数、子集数及采集时间的相关性。
    结果  RC随迭代次数增加而升高，在迭代1~10次时RC与其呈中度至高度相关（r=0.773~0.939，均P<0.05），迭代10次后RC趋于稳定。当子集数达到10后，RC基本趋于稳定。单因素方差分析结果显示，AC+RR+SC联合校正的RC显著优于AC及AC+RR（q=7.236~9.822，均P<0.05）。RC与采集时间无相关性（r>0.929，P>0.05）。3种采集时间下的图像视觉评分分别为（3.50±0.50）、（4.17±0.37）、（4.50±0.50）分。
    结论 优化重建参数可有效提高177Lu CZT SPECT/CT图像的RC及图像质量。推荐临床采用4次迭代、10个子集联合AC+RR+SC校正方案，采集时间可根据患者情况个性化选择。

     

    Abstract:
    Objective To identify the optimal image reconstruction parameters based on phantom acquisitions using 177Lu cadmium zinc telluride (CZT) SPECT/CT, aiming to improve image quality and achieve the optimal recovery coefficient (RC), thereby providing a basis for clinical diagnosis and dosimetric evaluation.
    Methods Images of the 177Lu 113 keV photopeak were acquired using a Discovery NM/CT 670 dual-head CZT SPECT/CT scanner. Image reconstruction was performed using ordered-subsets expectation maximization. The effects of the number of iterations (1–90) and subsets (2–20) on image RC and image quality were investigated, and the optimal correction scheme was determined by combining attenuation correction (AC), resolution recovery (RR), and scatter correction (SC). Under the above fixed parameters, the acquisition time per frame was changed (10, 15, and 20 s/frame) to investigate the effect of acquisition time on image RC. The performance of reconstruction parameters was evaluated by RC and image quality scores. Comparisons of RC among different correction methods were performed using one-way ANOVA, and pairwise comparisons between groups were performed using Tukey′s multiple comparison test. Pearson correlation analysis was used to evaluate the correlations of RC with the number of iterations, the number of subsets, and the acquisition time.
    Results RC increased as the number of iterations increased. At 1–10 iterations, RC showed a moderate to high correlation with the number of iterations (r=0.773–0.939, all P<0.05); after 10 iterations, RC tended to stabilize. When the number of subsets reached 10, RC reached equilibrium. One-way ANOVA showed that the RC obtained with combined AC+RR+SC correction was significantly better than that obtained with AC alone and AC+RR (q=7.236–9.822, all P<0.05). No correlation was found between RC and acquisition time (r>0.929, P>0.05). The visual image scores under the three acquisition times were (3.50±0.50), (4.17±0.37), and (4.50±0.50) scores.
    Conclusions Optimizing reconstruction parameters can effectively improve the RC and image quality of 177Lu CZT SPECT/CT images. Clinical practice should adopt 4 iterations, 10 subsets, and combined AC+RR+SC correction, with acquisition time individually selected according to each patient′s condition.

     

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