Dead time may affect the accuracy of quantitative SPECT (QPSECT), and thus of dosimetry. The aim of this study was to quantify the effect of dead time on 177Lu-QSPECT and renal dosimetry following peptide receptor radionuclide therapy (PRRT) of neuroendocrine tumours. QSPECT/CT was performed on days 1 and 3 during 564 personalized 177Lu-octreotate cycles in 166 patients. The dead-time data for each scanning time point was compiled. The impact of not correcting QSPECT for the dead time was assessed for the kidney dosimetry. This was also estimated for empiric PRRT by simulating in our cohort a regime of 7.4 GBq/cycle. The probability to observe a larger dead time increased with the injected activity. A dead-time loss greater than 5% affected 14.4% and 5.7% of QSPECT scans performed at days 1 and 3, respectively. This resulted in renal absorbed dose estimates that would have been underestimated by more than 5% in 5.7% of cycles if no dead-time correction was applied, with a maximum underestimation of 22.1%. In the simulated empiric regime, this potential dose underestimation would have been limited to 6.2%. Dead-time correction improves the accuracy of dosimetry in 177Lu radionuclide therapy and is warranted in personalized PRRT.

中文翻译：

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死区时间对PRRT期间定量177Lu-SPECT（QSPECT）和肾脏剂量的影响。

死区时间可能会影响定量SPECT（QPSECT）的准确性，从而影响剂量测定的准确性。这项研究的目的是量化神经内分泌肽受体放射性核素治疗（PRRT）后死时间对177Lu-QSPECT和肾脏剂量的影响。在166例患者的564个个性化177Lu奥曲肽周期的第1和第3天进行了QSPECT / CT。编译每个扫描时间点的停滞时间数据。对于肾脏剂量测定法，评估了不校正死区时间的QSPECT的影响。通过在我们的队列中模拟7.4 GBq /周期的方案，还可以对经验PRRT进行估算。观察到更大的死区时间的可能性随注入的活动而增加。死时间损失大于5％分别影响在第1天和第3天执行的QSPECT扫描的14.4％和5.7％。如果没有应用死区时间校正，那么在5.7％的周期中，肾脏吸收的剂量估计将被低估超过5％，最大低估为22.1％。在模拟的经验方案中，这种潜在的剂量低估将被限制为6.2％。停滞时间校正可提高177Lu放射性核素治疗中剂量测定的准确性，并在个性化PRRT中得到保证。