Prostate-specific membrane antigen (PSMA) radiotracers such as [18F]PSMA-1007 used with positron emission tomography-computed tomography (PET-CT) is promising for initial staging and detection of recurrent disease in prostate cancer patients. The block-sequential regularization expectation maximization algorithm (BSREM) is a new PET reconstruction algorithm, which provides higher image contrast while also reducing noise. The aim of the present study was to evaluate the influence of different acquisition times and different noise-suppressing factors in BSREM (β values) in [18F]PSMA-1007 PET-CT regarding quantitative data as well as a visual image quality assessment. We included 35 patients referred for clinical [18F]PSMA-1007 PET-CT. Four megabecquerels per kilogramme were administered and imaging was performed after 120 min. Eighty-four image series per patient were created with combinations of acquisition times of 1–4 min/bed position and β values of 300–1400. The noise level in normal tissue and the contrast-to-noise ratio (CNR) of pathological uptakes versus the local background were calculated. Image quality was assessed by experienced nuclear medicine physicians. The noise level in the liver, spleen, and muscle was higher for low β values and low acquisition times (written as activity time products (ATs = administered activity × acquisition time)) and was minimized at maximum AT (16 MBq/kg min) and maximum β (1400). There was only a small decrease above AT 10. The median CNR increased slowly with AT from approximately 6 to 12 and was substantially lower at AT 4 and higher at AT 14–16. At AT 4–6, many images were regarded as being of unacceptable quality. For AT 8, β values of 700–900 were considered of acceptable quality. An AT of 8 (for example as in our study, 4 MB/kg with an acquisition time of 2 min) with a β value of 700 performs well regarding noise level, CNR, and visual image quality assessment.

中文翻译：

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[18F] PSMA-1007 PET-CT在前列腺癌患者中使用常规重建的优化。

前列腺特异性膜抗原（PSMA）放射性示踪剂，例如与正电子发射断层扫描计算机断层扫描（PET-CT）一起使用的[18F] PSMA-1007，有望用于前列腺癌患者的初步分期和复发性疾病的检测。块序列正则化期望最大化算法（BSREM）是一种新的PET重建算法，它可以提供更高的图像对比度，同时还可以降低噪声。本研究的目的是评估定量数据以及视觉图像质量评估中[18F] PSMA-1007 PET-CT中BSREM（β值）中不同采集时间和不同噪声抑制因子的影响。我们纳入了35例因临床[18F] PSMA-1007 PET-CT而转诊的患者。每公斤服用四兆贝，并在120分钟后进行成像。每位患者创建了84个图像系列，采集时间为1-4分钟/床位，β值为300-1400。计算正常组织中的噪声水平以及病理摄取与局部背景的对比噪声比（CNR）。图像质量由经验丰富的核医学医师评估。低β值和低采集时间（写为活动时间乘积（ATs =所管理的活动×采集时间））在肝脏，脾脏和肌肉中的噪声水平较高，在最大AT（16 MBq / kg min）时最小化和最大β（1400）。在AT 10上方只有很小的下降。随着AT的增加，中值CNR从大约6缓慢增加到12，在AT 4显着降低，在AT 14-16显着升高。在AT 4–6，许多图像被认为是不可接受的质量。对于AT 8，β值700-900被认为是可以接受的质量。在噪声水平，CNR和视觉图像质量评估方面，AT值为8（例如，在我们的研究中为4 MB / kg，采集时间为2分钟），β值为700。