The aim of this study was to compare attenuation-correction (AC) approaches for PET/MRI in clinical neurooncology. Methods: Forty-nine PET/MRI brain scans were included: brain tumor studies using ¹⁸F-fluoro-ethyl-tyrosine (¹⁸F-FET) (n = 31) and ⁶⁸Ga-DOTANOC (n = 7) and studies of healthy subjects using ¹⁸F-FDG (n = 11). For each subject, MR-based AC maps (MR-AC) were acquired using the standard DIXON- and ultrashort echo time (UTE)–based approaches. A third MR-AC was calculated using a model-based, postprocessing approach to account for bone attenuation values (BD, noncommercial prototype software by Siemens Healthcare). As a reference, AC maps were derived from patient-specific CT images (CTref). PET data were reconstructed using standard settings after AC with all 4 AC methods. We report changes in diagnosis for all brain tumor patients and the following relative differences values (RDs [%]), with regards to AC-CTref: for ¹⁸F-FET (A)—SUVs as well as volumes of interest (VOIs) defined by a 70% threshold of all segmented lesions and lesion-to-background ratios; for ⁶⁸Ga-DOTANOC (B)—SUVs as well as VOIs defined by a 50% threshold for all lesions and the pituitary gland; and for ¹⁸F-FDG (C)—RD of SUVs of the whole brain and 10 anatomic regions segmented on MR images. Results: For brain tumor imaging (A and B), the standard PET-based diagnosis was not affected by any of the 3 MR-AC methods. For A, the average RDs of SUV_mean were −10%, −4%, and −3% and of the VOIs 1%, 2%, and 7% for DIXON, UTE, and BD, respectively. Lesion-to-background ratios for all MR-AC methods were similar to that of CTref. For B, average RDs of SUV_mean were −11%, −11%, and −3% and of the VOIs 1%, −4%, and −3%, respectively. In the case of ¹⁸F-FDG PET/MRI (C), RDs for the whole brain were −11%, −8%, and −5% for DIXON, UTE, and BD, respectively. Conclusion: The diagnostic reading of PET/MR patients with brain tumors did not change with the chosen AC method. Quantitative accuracy of SUVs was clinically acceptable for UTE- and BD-AC for group A, whereas for group B BD was in accordance with CTref. Nevertheless, for the quantification of individual lesions large deviations to CTref can be observed independent of the MR-AC method used.

这项研究的目的是比较临床神经肿瘤学中用于PET / MRI的衰减校正（AC）方法。方法：包括四十九次PET / MRI脑扫描：使用¹⁸ F-氟代乙基酪氨酸（¹⁸ F-FET）（n = 31）和⁶⁸ Ga-DOTANOC（n = 7）进行脑肿瘤研究以及健康研究使用¹⁸ F-FDG的受试者（n= 11）。对于每个受试者，使用基于标准DIXON和超短回波时间（UTE）的方法获取基于MR的AC图（MR-AC）。使用基于模型的后处理方法来计算第三个MR-AC，以说明骨骼衰减值（BD，西门子医疗集团的非商业原型软件）。作为参考，AC图来自患者特定的CT图像（CTref）。使用所有4种AC方法，在AC后使用标准设置重建PET数据。对于AC-CTref，我们报告了所有脑肿瘤患者的诊断变化以及以下相对差异值（RD [％]）：对于¹⁸ F-FET（A）-SUV和所定义的关注体积（VOI）所有分割的病灶和病灶与背景比率的阈值提高70％；为⁶⁸Ga-DOTANOC（B）-SUV和VOI由所有病变和垂体的50％阈值定义；对于全脑SUV的¹⁸ F-FDG（C）-RD和在MR图像上分割的10个解剖区域。结果：对于脑肿瘤成像（A和B），基于PET的标准诊断不受3种MR-AC方法的影响。对于A，SUV的平均RD_平均值分别为-10％，-4％和-3％，而VOI的平均RD分别为DIXON，UTE和BD的1％，2％和7％。所有MR-AC方法的病变背景比率与CTref相似。对于B，SUV的平均的RD_平均值分别为-11％，11％和-3％和VOI的1％，4％和-3％之间。在¹⁸的情况下F-FDG PET / MRI（C）对DIXON，UTE和BD的全脑RD分别为-11％，-8％和-5％。结论：选择的AC方法对PET / MR脑肿瘤患者的诊断读数没有改变。A组的UTE-和BD-AC的SUV的定量精度在临床上是可以接受的，而B组的BD符合CTref。然而，为了量化单个病变，可以独立于所使用的MR-AC方法观察到CTref的较大偏差。