Molecular Imaging (PET) of Brain Tumors
Molecular Imaging (PET) of Brain Tumors
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DOI：
10.1016/j.nic.2009.08.012
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发表时间：
2009-11-01
影响因子：
2.3
通讯作者：
Alavi, Abass
中科院分区：
文献类型：
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作者：
Basu, Sandip;Alavi, Abass
尽管由于正常灰质的高背景，氟脱氧葡萄糖正电子发射断层扫描（FDG-PET）在脑肿瘤成像中存在公认的局限性，但这种成像方式为脑肿瘤患者的管理提供了以下方面的关键信息：（1）提供肿瘤的全局图像，从而引导立体定向活检的适当部位，从而提高其准确性并减少活检样本的数量;和（2）预测肿瘤的生物学行为和侵袭性，从而帮助预后。另一个已经被广泛研究的领域，包括区分复发性肿瘤与治疗相关的变化（例如，放射性坏死和手术后变化）。此外，FDG-PET已证明其在区分获得性免疫缺陷综合征患者的淋巴瘤和弓形虫病方面具有很高的准确性，并被用作这种情况下的首选调查。与磁共振成像和延迟FDG-PET成像的图像配准是2种显著提高解释准确性的方法，因此应在临床环境中常规使用。近年来，越来越多的脑肿瘤PET研究使用了其他示踪剂（如标记的甲硫氨酸、酪氨酸、胸苷、胆碱、氟咪唑、EF 5等），其中正电子标记的氨基酸类似物、核苷酸类似物和缺氧成像示踪剂特别令人感兴趣。与FDG相比，这些放射性示踪剂的主要优点是在正常脑组织中的背景活性明显较低，从而可以检测到小病变和低级别肿瘤。氨基酸PET示踪剂的前景一直受到强调，因为与FDG相比，它们在成像复发肿瘤（特别是低级别肿瘤）方面具有更高的灵敏度，并且在区分复发肿瘤和治疗相关变化方面具有更高的准确性。较新的PET示踪剂也显示出对肿瘤生物学的重要方面进行成像的巨大潜力，从而显示出预测预后的能力。低氧成像示踪剂（如氟咪唑或最近的EF 5）的价值是实质性的放射治疗计划和预测治疗反应。此外，它们可能在未来指导和监测缺氧肿瘤的靶向缺氧治疗中发挥重要作用。在调强放射治疗时代，利用新型PET示踪剂和多模态成像开发最佳图像分割策略是一种值得一提的方法，并且可能在脑肿瘤患者的放射治疗计划中具有重要的临床和研究应用。
Despite the recognized limitations of (18)Fluorodeoxyglucose positron emission tomography (FDG-PET) in brain tumor imaging due to the high background of normal gray matter, this imaging modality provides critical information for the management of patients with cerebral neoplasms with regard to the following aspects: (1) providing a global picture of the tumor and thus guiding the appropriate site for stereotactic biopsy, and thereby enhancing its accuracy and reducing the number of biopsy samples; and (2) prediction of biologic behavior and aggressiveness of the tumor, thereby aiding in prognosis. Another area, which has been investigated extensively, includes differentiating recurrent tumor from treatment-related changes (eg, radiation necrosis and postsurgical changes). Furthermore, FDG-PET has demonstrated its usefulness in differentiating lymphoma from toxoplasmosis in patients with acquired immune deficiency syndrome with great accuracy, and is used as the investigation of choice in this setting. Image coregistration with magnetic resonance imaging and delayed FDG-PET imaging are 2 maneuvers that substantially improve the accuracy of interpretation, and hence should be routinely employed in clinical settings. In recent years an increasing number of brain tumor PET studies has used other tracers (like labeled methionine, tyrosine, thymidine, choline, fluoromisonidazole, EF5, and so forth), of which positron-labeled amino acid analogues, nucleotide analogues, and the hypoxia imaging tracers are of special interest. The major advantage of these radiotracers over FDG is the markedly lower background activity in normal brain tissue, which allows detection of small lesions and low-grade tumors. The promise of the amino acid PET tracers has been emphasized due to their higher sensitivity in imaging recurrent tumors (particularly the low-grade ones) and better accuracy for differentiating between recurrent tumors and treatment-related changes compared with FDG. The newer PET tracers have also shown great potential to image important aspects of tumor biology and thereby demonstrate ability to forecast prognosis. The value of hypoxia imaging tracers (such as fluoromisonidazole or more recently EF5) is substantial in radiotherapy planning and predicting treatment response. In addition, they may play an important role in the future in directing and monitoring targeted hypoxic therapy for tumors with hypoxia. Development of optimal image segmentation strategy with novel PET tracers and multimodality imaging is an approach that deserves mention in the era of intensity modulated radiotherapy, and which is likely to have important clinical and research applications in radiotherapy planning in patients with brain tumor.