基于 3D 打印双室肾脏模型的 Lu SPECT/CT 图像定量优化。

Optimizing Image Quantification for Lu SPECT/CT Based on a 3D Printed 2-Compartment Kidney Phantom.

机构信息

Department of Nuclear Medicine, University of Würzburg, Würzburg, Germany

Department of Nuclear Medicine, University of Würzburg, Würzburg, Germany.

出版信息

J Nucl Med. 2018 Apr;59(4):616-624. doi: 10.2967/jnumed.117.200170. Epub 2017 Nov 2.

DOI:10.2967/jnumed.117.200170

PMID:29097409

Abstract

The aim of this work was to find an optimal setup for activity determination of Lu-based SPECT/CT imaging reconstructed with 2 commercially available methods (xSPECT Quant and Flash3D). For this purpose, 3-dimensional (3D)-printed phantoms of different geometries were manufactured, different partial-volume correction (PVC) methods were applied, and the accuracy of the activity determination was evaluated. A 2-compartment kidney phantom (70% cortical and 30% medullary compartment), a sphere, and an ellipsoid of equal volumes were 3D printed, filled with Lu, and scanned with a SPECT/CT system. Reconstructions were performed with xSPECT and Flash3D. Different PVC methods were applied to find an optimal quantification setup: method 1 was a geometry-specific recovery coefficient based on the 3D printing model, method 2 was a geometry-specific recovery coefficient based on the low-dose CT scan, method 3 was an enlarged volume of interest including spilled-out counts, method 4 was activity concentration in the peak milliliter applied to the entire CT-based volume, and method 5 was a fixed threshold of 42% of the maximum in a large volume containing the object of interest. Additionally, the influence of postreconstruction gaussian filtering was investigated. Although the recovery coefficients of sphere and ellipsoid differed by only 0.7%, a difference of 31.7% was observed between the sphere and the renal cortex phantoms. Without postfiltering, the model-based recovery coefficients (methods 1 and 2) resulted in the best accuracies (xSPECT, 1.5%; Flash3D, 10.3%), followed by the enlarged volume (method 3) (xSPECT, 8.5%; Flash3D, 13.0%). The peak-milliliter method (method 4) showed large errors only for sphere and ellipsoid (xSPECT, 23.4%; Flash3D, 21.6%). Applying a 42% threshold (method 5) led to the largest quantification errors (xSPECT, 32.3%; Flash3D, 46.7%). After postfiltering, a general increase in the errors was observed. In this work, 3D printing was used as a prototyping technique for a geometry-specific investigation of SPECT/CT reconstruction parameters and PVC methods. The optimal setup for activity determination was found to be an unsmoothed SPECT/CT reconstruction in combination with a recovery coefficient based on the low-dose CT. The difference between spheric and renal recovery coefficients suggests that the typically applied volume-dependent but only sphere-based recovery coefficient lookup tables should be replaced by a more geometry-specific alternative.

摘要

这项工作的目的是为基于 Lu 的 SPECT/CT 成像的活性测定找到最佳设置，该成像使用 2 种市售方法（xSPECT Quant 和 Flash3D）进行重建。为此，制造了不同几何形状的 3 维（3D）打印体模，应用了不同的部分体积校正（PVC）方法，并评估了活性测定的准确性。制造了一个 2 室肾脏体模（70%皮质和 30%髓质室）、一个球体和一个等体积的椭圆体，并用 SPECT/CT 系统对其进行填充和扫描。使用 xSPECT 和 Flash3D 进行重建。应用不同的 PVC 方法来找到最佳的量化设置：方法 1 是基于 3D 打印模型的特定几何形状的恢复系数，方法 2 是基于低剂量 CT 扫描的特定几何形状的恢复系数，方法 3 是包含溢出计数的感兴趣体积的扩大，方法 4 是应用于整个基于 CT 的体积的峰毫升的活性浓度，方法 5 是包含感兴趣物体的大体积中的 42%最大的固定阈值。此外，还研究了重建后高斯滤波的影响。尽管球体和椭圆体的恢复系数仅相差 0.7%，但球体和肾脏皮质体模之间的差异为 31.7%。不进行后滤波时，基于模型的恢复系数（方法 1 和 2）会导致最佳准确性（xSPECT，1.5%；Flash3D，10.3%），其次是扩大体积（方法 3）（xSPECT，8.5%；Flash3D，13.0%）。峰毫升法（方法 4）仅在球体和椭圆体上显示出较大误差（xSPECT，23.4%；Flash3D，21.6%）。应用 42%的阈值（方法 5）会导致最大的量化误差（xSPECT，32.3%；Flash3D，46.7%）。后滤波后，观察到误差普遍增加。在这项工作中，3D 打印被用作特定于 SPECT/CT 重建参数和 PVC 方法的几何形状的原型技术。发现活动测定的最佳设置是结合基于低剂量 CT 的恢复系数的未平滑的 SPECT/CT 重建。球型和肾脏恢复系数之间的差异表明，典型应用的基于体积但仅基于球体的恢复系数查找表应替换为更具几何形状的替代表。