Scandium (Sc) is a promising candidate for theranostic applications due to the existence of radioisotopes suitable for both imaging and therapy. A “proof-of-concept” study regarding first-in-human use of ⁴⁴Sc for imaging metastatic neuroendocrine tumors was reported recently, however, quantitative assessment of ⁴⁴Sc-based PET images was not performed. The aim of this study was to evaluate quantitative capabilities of ⁴⁴Sc-PET using a commercial PET scanner. The NEMA/IEC body phantom with ⁴⁴Sc was acquired according to the local protocol used for whole-body oncological [¹⁸F]FDG PET examinations. Additionally, we characterized the signal recovery (recovery coefficient—RC) according to the iteration number. For all reconstructions, pertinent image corrections (normalization, dead time, activity decay, random coincidence, and attenuation) were applied. Presently, ⁴⁴Sc scatter corrections are not optimized and could, thus, result in quantitative bias. To investigate the best option, the data were reconstructed using different available scatter corrections (relative -RelSC- and absolute -AbsSC-) and an additional prompt-gamma correction (PGC). System cross-calibration with the local dose calibrator (BG_cal) and image noise, expressed by the coefficient of variation (COV), were evaluated in the homogeneous background region (5 kBq/mL) of the phantom. Maximum (RC_max) and 50% threshold recovery coefficients, corrected for background (RC_A50), were measured for all spherical inserts (25 kBq/mL) of the phantom. Acceptable COV (<15%) was achievable with low iteration numbers (<3). BG_cal differences were low: mean BG_cal were 77.8, 81.3, and 86.7%, for RelSC, AbsSC, and PGC, respectively. RC values exceeded the present RC range recommended for [¹⁸F]FDG procedures. Using the iterations to be evaluated, RC_A50 ranged from 29.9 to 59.9% for the smallest lesion (spherical insert of 10 mm diameter) and from 45.5 to 80.3% (13 mm), 66.4 to 75.6% (17 mm), 71.7 to 75.7% (22 mm), 75.1 to 78.6% (28 mm), and 76.7 to 80.9% (37 mm) for the, respectively spherical inserts. The results of this study show that clinical ⁴⁴Sc-PET imaging has the potential to provide signal recovery in lesions of different sizes comparable to current ¹⁸F-PET standards. In order to improve the quantitative accuracy of ⁴⁴Sc PET, optimized corrections are still necessary and will be investigated further in future.

由于存在适合成像和治疗的放射性同位素，（Sc）是治疗学应用的有前途的候选者。最近报道了一项关于“首次在人体中使用⁴⁴ Sc对转移性神经内分泌肿瘤成像的概念验证”研究，但是，尚未对基于⁴⁴ Sc的PET图像进行定量评估。这项研究的目的是使用商用PET扫描仪评估⁴⁴ Sc-PET的定量能力。根据用于全身肿瘤学的本地协议，获得了具有⁴⁴ Sc的NEMA / IEC人体模型[ ¹⁸F] FDG PET检查。此外，我们根据迭代次数来表征信号恢复（恢复系数-RC）。对于所有重建，均应用了相关的图像校正（标准化，停滞时间，活动衰减，随机重合和衰减）。目前，没有对^44个Sc散射校正进行优化，因此可能导致定量偏差。为了研究最佳选择，使用不同的可用散点校正（相对-RelSC-和绝对-AbsSC-）和附加的即时伽玛校正（PGC）重建数据。使用本地剂量校准器（BG）进行系统交叉校准_卡）和以变异系数（COV）表示的图像噪声，在模型的均匀背景区域（5 kBq / mL）中进行了评估。最大（RC_最高）和50％阈值恢复系数，并针对背景（RC_一种50），分别用于所述体模的所有球形插入件（25 KBQ / mL）的测量。低迭代次数（<3）可以达到可接受的COV（<15％）。BG_卡 差异低：平均BG_卡RelSC，AbsSC和PGC分别为77.8、81.3和86.7％。RC值超出了[ ¹⁸ F] FDG程序推荐的当前RC范围。使用要评估的迭代，RC_一种对于最小的病变（直径为10毫米的球形插入物），₅₀为29.9至59.9％，13毫米为45.5至80.3％（17毫米），17.6％为66.4至75.6％（22毫米），75.1至75.1对于球形刀片，分别为78.6％（28 mm）和76.7至80.9％（37 mm）。这项研究的结果表明，与目前的¹⁸ F-PET标准相比，临床⁴⁴ Sc-PET成像有潜力在不同大小的病变中提供信号恢复。为了提高⁴⁴ Sc PET的定量准确度，仍需要优化校正，并将在以后进行进一步研究。