Molecular Imaging and Therapy Service, Department of Radiology, Memorial Sloan Kettering Cancer Center, New York, NY.
Body Imaging Service, Department of Radiology, Memorial Sloan Kettering Cancer Center, New York, NY.
Semin Nucl Med. 2021 Sep;51(5):485-501. doi: 10.1053/j.semnuclmed.2021.04.001. Epub 2021 May 6.
In the past two decades, PET/CT has become an essential modality in oncology increasingly used in the management of gastrointestinal (GI) cancers. Most PET/CT tracers used in clinical practice show some degree of GI uptake. This uptake is quite variable and knowledge of common patterns of biodistribution of various radiotracers is helpful in clinical practice. F-Fluoro-Deoxy-Glucose (FDG) is the most commonly used radiotracer and has quite a variable uptake within the bowel. Ga-Prostate specific membrane antigen (PSMA) shows intense uptake within the proximal small bowel loops. C-methyl-L-methionine (MET) shows high accumulation within the bowels, which makes it difficult to assess bowel or pelvic diseases. One must also be aware of technical artifacts causing difficulties in interpretations, such as high attenuation oral contrast material within the bowel lumen or misregistration artifact due to patient movements. It is imperative to know the common variants and benign diseases that can mimic malignant pathologies. Intense FDG uptake within the esophagus and stomach may be a normal variant or may be associated with benign conditions such as esophagitis, reflux disease, or gastritis. Metformin can cause diffuse intense uptake throughout the bowel loops. Intense physiologic uptake can also be seen within the anal canal. Segmental bowel uptake can be seen in inflammatory bowel disease, radiation, or medication induced enteritis/colitis or infection. Diagnosis of appendicitis or diverticular disease requires CT correlation, as normal appendix or diverticulum can show intense uptake. Certain malignant pathologies are known to have only low FDG uptake, such as early-stage esophageal adenocarcinoma, mucinous tumors, indolent lymphomas, and multicystic mesotheliomas. Response assessment, particularly in the neoadjuvant setting, can be limited by post-treatment inflammatory changes. Post-operative complications such as abscess or fistula formation can also show intense uptake and may obscure underlying malignant pathology. In the absence of clinical suspicion or rising tumor marker, the role of FDG PET/CT in routine surveillance of patients with GI malignancy is not clear.
在过去的二十年中，PET/CT 已成为肿瘤学中不可或缺的一种方式，越来越多地用于胃肠道（GI）癌症的治疗管理。在临床实践中使用的大多数 PET/CT 示踪剂都显示出一定程度的 GI 摄取。这种摄取变化很大，了解各种放射性示踪剂的常见分布模式在临床实践中很有帮助。氟代脱氧葡萄糖（FDG）是最常用的放射性示踪剂，在肠道中有相当大的摄取。镓前列腺特异性膜抗原（PSMA）在近端小肠环中表现出强烈的摄取。C-甲基-L-蛋氨酸（MET）在肠道中高度积聚，这使得评估肠道或盆腔疾病变得困难。还必须注意导致解释困难的技术伪影，例如肠腔中高衰减的口服对比材料或由于患者运动引起的配准伪影。了解可模拟恶性病理的常见变异和良性疾病至关重要。食管和胃内 FDG 摄取强烈可能是正常变异，也可能与食管炎、反流病或胃炎等良性疾病有关。二甲双胍可导致整个肠环弥漫性摄取强烈。在肛门管内也可以看到强烈的生理性摄取。在炎症性肠病、辐射或药物诱导的肠炎/结肠炎或感染中，可以看到节段性肠摄取。阑尾炎或憩室病的诊断需要 CT 相关性，因为正常阑尾或憩室也可以表现出强烈摄取。某些恶性病理仅显示低 FDG 摄取，例如早期食管腺癌、黏液性肿瘤、惰性淋巴瘤和多囊性间皮瘤。在新辅助治疗中，由于治疗后炎症变化，反应评估可能受到限制。术后并发症，如脓肿或瘘管形成，也可能表现出强烈摄取，可能掩盖潜在的恶性病理。在没有临床怀疑或肿瘤标志物升高的情况下，FDG PET/CT 在胃肠道恶性肿瘤常规监测中的作用尚不清楚。
