Currently, no consistent guidelines for CT scans used within PET/CT examinations are available. This systematic review provides an up-to-date overview of studies to answer the following questions: What are the specific CT protocols used in PET/CT? What are the possible purposes of requiring a CT study within a PET/CT scan? Is the CT protocol obtained from a dosimetric optimisation study? PubMed/MEDLINE, Cochrane Library, Embase and Scopus were systematically searched for relevant studies in accordance with the PRISMA statement. The literature search was conducted from January 2007 until June 2019. Data derived from studies were standardized in order to reduce possible biases, and they were divided into clinically homogeneous subgroups (adult, child or phantom). Subsequently, we divided the CT protocol intents into 3 types (anatomic localization only, attenuation correction only and diagnostic purpose). A narrative approach was used to summarise datasets and to investigate their heterogeneity (due to medical prescription methodology) and their combination in multiseries CT protocols. When weighted computed tomography dose index (CTDIw) was available, we calculated the volumetric computed tomography dose index (CTDIvol) using the pitch value to make the results uniform. Eventually, the correlation between protocol intents and CTDIvol values was obtained using a Kruskal–Wallis one-way ANOVA statistical test. Starting from a total of 1440 retrieved records, twenty-four studies were eligible for inclusion in addition to two large multicentric works that we used to compare the results. We analyzed 87 CT protocols. There was a considerable range of variation in the acquisition parameters: tube current–time product revealed to have the most variable range, which was 10–300 mAs for adults and 10–80 mAs for paediatric patients. Seventy percent of datasets presented scans acquired with tube current modulation, 9% used fixed tube current and in 21% of them, this information was not available. Dependence between mean CTDIvol values and protocol intent was statistically significant (p = 0.002). As expected, in diagnostic protocols, there was a statistically significant difference between CTDIvol values of with and without contrast acquisitions (11.68 mGy vs 7.99 mGy, p = 0.009). In 13 out of 87 studies, the optimisation aim was not reported; in 2 papers, a clinical protocol was used; and in 11 works, a dose optimisation protocol was applied. According to this review, the dose optimisation in PET/CT exams depends heavily on the correct implementation of the CT protocol. In addition to this, considering the latest technology advances (i.e. iterative algorithms development), we suggest a periodic quality control audit to stay updated on new clinical utility modalities and to achieve a shared standardisation of clinical protocols. In conclusion, this study pointed out the necessity to better identify the specific CT protocol use within PET/CT scans, taking into account the continuous development of new technologies.

中文翻译：

---

PET / CT中的CT方案优化：系统综述

当前，在PET / CT检查中没有统一的CT扫描指南。该系统综述提供了最新的研究概述，以回答以下问题：PET / CT中使用的特定CT方案是什么？在PET / CT扫描中要求进行CT研究的可能目的是什么？CT方案是从剂量学优化研究中获得的吗？根据PRISMA声明，系统地搜索了PubMed / MEDLINE，Cochrane库，Embase和Scopus以进行相关研究。文献检索从2007年1月至2019年6月进行。为了减少可能的偏倚，对研究数据进行了标准化，并将其分为临床上均一的亚组（成人，儿童或幻像）。后来，我们将CT协议的意图分为3种类型（仅解剖定位，仅衰减校正和诊断目的）。一种叙述方法用于汇总数据集，并研究其异质性（由于医疗处方方法的原因）及其在多系列CT方案中的组合。当可获得加权计算机断层摄影剂量指数（CTDIw）时，我们使用音高值计算体积计算机断层摄影剂量指数（CTDIvol），以使结果均匀。最终，使用Kruskal-Wallis单向方差分析统计测试获得方案意图与CTDIvol值之间的相关性。从总共1440条检索到的记录开始，除我们用来比较结果的两份大型多中心著作外，还有24项研究符合纳入条件。我们分析了87个CT方案。采集参数的变化范围很大：电子管电流-时间乘积显示出最大的变化范围，成人为10-300 mAs，儿科患者为10​​-80 mAs。70％的数据集显示了通过电子管电流调制获取的扫描结果，其中9％使用了固定电子管电流，其中21％的信息不可用。平均CTDIvol值与协议意图之间的相关性具有统计学意义（p = 0.002）。不出所料，在诊断方案中，有和没有造影剂采集的CTDIvol值之间在统计学上都有显着差异（11.68 mGy与7.99 mGy，p = 0.009）。在87项研究中，有13项没有报告优化目标；在2篇论文中，使用了临床方案；在11项工作中，应用了剂量优化方案。根据这篇评论，PET / CT检查中的剂量优化在很大程度上取决于CT方案的正确实施。除此之外，考虑到最新的技术进步（即迭代算法的发展），我们建议定期进行质量控制审核，以随时了解新的临床实用程序形式并实现临床协议的共享标准化。总而言之，本研究指出了考虑到新技术的不断发展，有必要更好地识别PET / CT扫描中特定CT协议的使用。我们建议进行定期的质量控制审核，以随时了解新的临床实用程序形式并实现临床协议的共享标准化。总而言之，本研究指出了考虑到新技术的不断发展，有必要更好地识别PET / CT扫描中特定CT协议的使用。我们建议进行定期的质量控制审核，以随时了解新的临床实用程序形式并实现临床协议的共享标准化。总而言之，本研究指出了考虑到新技术的不断发展，有必要更好地识别PET / CT扫描中特定CT协议的使用。