Introduction

¹¹C-acetate (ACE)-PET/CT is used for staging of high-risk prostate cancer. PET data is reconstructed with iterative algorithms, such as VUEPointHD ViP (VPHD) and VUEPoint HD Sharp IR (SharpIR), the latter with additional resolution recovery. It is expected that the resolution recovery algorithm should render more accurate maximum and mean standardized uptake values (SUV_max and SUV_mean) and functional tumor volumes (FTV) than the ordinary OSEM. Performing quantitative analysis, choice of volume-of-interest delineation algorithm (SUV threshold) may influence FTV. Optimizing PET acquisition time is justified if image quality and quantitation do not deteriorate.

The aim of this study is to identify the optimal reconstruction algorithm, SUV threshold and acquisition time for ACE-PET/CT.

Methods

ACE-PET/CT data acquired with a General Electric Discovery 690 PET/CT from 16 consecutive high-risk prostate cancer patients was reconstructed with VPHD and SharpIR. Forty pelvic lymph nodes (LNs) and 14 prostate glands were delineated with 42% and estimated threshold. SUV_max, SUV_mean, FTV and total lesion uptake were measured.

Default acquisition time was four minutes per bed position. In a subset of lesions, acquisition times of one, two and four minutes were evaluated.

Structural tumor volumes (STV) of the LNs were measured with CT for correlation with functional volumetric parameters.

To validate SUV quantification under different conditions with SharpIR 42%, recovery coefficients (RCs) of SUV_mean and FTV were calculated from a phantom with ¹⁸F-fluoro-deoxy-glucose (FDG)-filled volumes 0.1–9.2cm³ and signal-to-background (S/B) ratios 4.3–15.9.

Results

With SharpIR, SUV_max and SUV_mean were higher and FTV lower compared with VPHD, regardless of threshold method, in both prostates and LNs.

Total lesion uptake determined with both threshold methods was lower with SharpIR compared with VPHD with both threshold methods, except in subgroup analysis of prostate targets where estimated threshold returned higher values.

Longer acquisition times returned higher FTV for both threshold methods, regardless of reconstruction algorithm. The FTV difference was most pronounced with one minute’s acquisition per bed position, which also produced visually the highest noise. SUV parameters were unaffected by varying acquisition times.

FTV with SharpIR 42% showed the best correspondence with STV.

SharpIR 42% gave higher RCs of SUV_mean and FTV with increasing phantom size and S/B-ratio, as expected.

Conclusions

Delineation with SharpIR 42% seems to provide the most accurate combined information from SUV_max, SUV_mean, FTV and total lesion uptake. Acquisition time may be shortened to two minutes per bed position with preserved image quality.

中文翻译：

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临床¹¹ C-醋酸PET / CT中PET重建算法，SUV阈值算法和PET采集时间的优化

介绍

¹¹ C-醋酸盐（ACE）-PET / CT用于高危前列腺癌的分期。PET数据使用VUEPointHD ViP（VPHD）和VUEPoint HD Sharp IR（SharpIR）等迭代算法进行重建，后者具有额外的分辨率恢复能力。预计分辨率恢复算法应比普通的OSEM更加准确，准确地确定标准化的最大摄取值（SUV _max和SUV _mean）和功能性肿瘤体积（FTV）。执行定量分析时，感兴趣区划定算法（SUV阈值）的选择可能会影响FTV。如果图像质量和定量不降低，则优化PET采集时间是合理的。

这项研究的目的是确定ACE-PET / CT的最佳重建算法，SUV阈值和采集时间。

方法

使用VPHD和SharpIR重建了用General Electric Discovery 690 PET / CT从16位连续的高危前列腺癌患者那里获得的ACE-PET / CT数据。用42％和估计的阈值描绘了40个盆腔淋巴结（LNs）和14个前列腺。测量SUV _max，SUV_平均数，FTV和总病灶摄取量。

默认采集时间为每个床位四分钟。在病变的子集中，评估采集时间分别为1分钟，2分钟和4分钟。

用CT测量LN的结构肿瘤体积（STV），以与功能性体积参数相关。

为了验证在不同条件下使用SharpIR 42％进行的SUV量化，我们从模型中填充了¹⁸ F-氟-脱氧葡萄糖（FDG）的体积为0.1-9.2cm ^3的信号模型，计算了SUV_平均值和FTV的恢复系数（RCs​​）。与背景（S / B）的比率为4.3–15.9。

结果

与VPHD相比，无论采用阈值方法如何，在SharpIR和LN中，使用SharpIR时，SUV _max和SUV_均值均高于VPHD，而FTV较低。

与两种阈值方法的VPHD相比，两种阈值方法确定的总病灶摄取率均低于SharpIR，而对前列腺靶标的亚组分析估计阈值返回较高值。

无论采用哪种重构算法，两种阈值方法的采集时间越长，FTV越高。FTV的差异最为明显，每个床位的采集时间为一分钟，这在视觉上也产生了最高的噪音。SUV参数不受采集时间变化的影响。

具有SharpIR 42％的FTV显示与STV的最佳对应。

如预期的那样，SharpIR 42％给出了更高的SUV_平均数和FTV RC，同时幻像尺寸和S / B比也增加了。

结论

SharpIR 42％的轮廓似乎提供了来自SUV _max，SUV_均值，FTV和总病灶摄取的最准确的组合信息。可以将每个床位的采集时间缩短到两分钟，同时保持图像质量。