背景:几个研究小组已经探索了放射性核素在热不可知应用中的潜力,因为它们的半衰期更长,并且在诊断和治疗对应物之间具有相等或相似的配位化学,以及分别是Luttium-177和tr-161。不同于镓-68/Luttium-177对,可能显示不同的体内摄取模式,钪放射性同位素的使用保证了诊断和治疗放射性肽之间的一致行为。与镓-68相比,钪的半衰期更长的优点是能够研究长时间的放射性肽摄取及其对集中生产和分配的适用性。然而,关注的是钪-44的衰变特性和钪-43的高生产成本。这项研究旨在评估使用scan放射性同位素与生长抑素类似物对抗镓68进行神经内分泌肿瘤PET成像的剂量学意义。
方法:使用放射性肽[43/44/44mSc]Sc-和[68Ga]Ga-DOTATATE,从产生的时间积分活性曲线(TIAC)估计每个注射活性(AD/IA)的吸收剂量。肾脏,肝脏,脾,脾选择红骨髓(RBM)进行剂量估计研究。EGSnrc和MCNP6.1蒙特卡罗(MC)代码用于女性(AF)和男性(AM)ICRP体模。结果与Olinda/EXM软件进行了比较,和评估的有效剂量浓度,钪放射性同位素之间的不同成分。
结果:我们的发现表明MC代码之间具有良好的一致性,平均差为-3±8%。肾脏,肝脏,和脾脏显示MC代码之间的差异(min和max)在-4%至8%的范围内。对于研究中使用的所有放射性肽的两个体模都观察到了这一点。与Olinda/EXM相比,观察到的最大差异是RBM,对于基于scadi和镓的放射性肽,AF的比例为21%,AM的比例为16%。尽管存在差异,我们的研究结果表明,与68Ga基对应物相比,[43/44Sc]Sc-DOTATATE的吸收剂量更高。
结论:这项研究发现,与[68Ga]Ga-DOTATATE相比,[43/44Sc]Sc-DOTATATE对危险器官的吸收剂量更高,假设平均分配。这是由于与镓-68相比,钪放射性同位素的半衰期更长。然而,计算剂量在可接受范围内,使钪放射性同位素成为PET成像中镓-68的可行替代品,有可能通过稍后的时间点成像提供增强的诊断潜力.
BACKGROUND: Several research groups have explored the potential of scandium radionuclides for theragnostic applications due to their longer half-lives and equal or similar coordination chemistry between their diagnostic and therapeutic counterparts, as well as lutetium-177 and terbium-161, respectively. Unlike the gallium-68/lutetium-177 pair, which may show different in-vivo uptake patterns, the use of scandium radioisotopes promises consistent behaviour between diagnostic and therapeutic radiopeptides. An advantage of scandium\'s longer half-life over gallium-68 is the ability to study radiopeptide uptake over extended periods and its suitability for centralized production and distribution. However, concerns arise from scandium-44\'s decay characteristics and scandium-43\'s high production costs. This study aimed to evaluate the dosimetric implications of using scandium radioisotopes with somatostatin analogues against gallium-68 for PET imaging of neuroendocrine tumours.
METHODS: Absorbed dose per injected activity (AD/IA) from the generated time-integrated activity curve (TIAC) were estimated using the radiopeptides [43/44/44mSc]Sc- and [68Ga]Ga-DOTATATE. The kidneys, liver, spleen, and red bone marrow (RBM) were selected for dose estimation studies. The EGSnrc and MCNP6.1 Monte Carlo (MC) codes were used with female (AF) and male (AM) ICRP phantoms. The results were compared to Olinda/EXM software, and the effective dose concentrations assessed, varying composition between the scandium radioisotopes.
RESULTS: Our findings showed good agreement between the MC codes, with - 3 ± 8% mean difference. Kidneys, liver, and spleen showed differences between the MC codes (min and max) in a range of - 4% to 8%. This was observed for both phantoms for all radiopeptides used in the study. Compared to Olinda/EXM the largest observed difference was for the RBM, of 21% for the AF and 16% for the AM for scandium- and gallium-based radiopeptides. Despite the differences, our findings showed a higher absorbed dose on [43/44Sc]Sc-DOTATATE compared to its 68Ga-based counterpart.
CONCLUSIONS: This study found that [43/44Sc]Sc-DOTATATE delivers a higher absorbed dose to organs at risk compared to [68Ga]Ga-DOTATATE, assuming equal distribution. This is due to the longer half-life of scandium radioisotopes compared to gallium-68. However, calculated doses are within acceptable ranges, making scandium radioisotopes a feasible replacement for gallium-68 in PET imaging, potentially offering enhanced diagnostic potential with later timepoint imaging.