胰腺实性假乳头状瘤^18F—FDGPET／CT影像表现和代谢特征分析

Analysis of ^18F-FDG PET/CT imaging characteristics and metabolism features of pancreatic solid pseudopapillary tumor

目的 总结胰腺实性假乳头状瘤（SPTP）^18F－FDG PET/CT的影像表现和代谢特点，提高对该病的认识和诊断准确性。方法 回顾性分析2010年8月至2014年6月在上海长海医院经病理证实为SPTP的16例患者（男3例，女13例，平均年龄38.6岁）PET/CT及临床资料。观察病灶的形态、密度及代谢特征，测量病灶大小、SUVmax；对10例行双时相显像患者的早期SUVmax与延迟SUVmax进行配对t检验，并计算滞留指数（RI）。结果16例患者病灶均为单发、外生性生长，边界较清楚。肿瘤长径1.2～10.4（4.0±2.7） cm，短径1.0～8.6（3.3±2.2） cm。4例实性病灶中，2例为均匀高代谢灶，1例不均匀高代谢灶，1例FDG摄取与正常胰腺实质相仿；12例囊实性病灶表现为不均匀高代谢区（内见代谢明显增高壁结节）与不规则轻度代谢和（或）摄取缺损区混杂，缺损区可位于肿瘤中心或边缘。16例患者SUVmax为7.3±6.8（2.4～29.1）；10例双时相显像患者早期SUVmax为6.0±3.4（2.4～14.1），延迟SUVmax为6.4±3.2（2.3～13.4），差异无统计学意义（t＝－1.658, P〉0.05）；RI为6.9%（－4.2%，13.6%）。16例中5例病灶侵犯胰管或胰周器官，对应病灶SUVmax为6.7±4.1（3.4～13.1），无侵犯病灶的SUVmax为4.4（2.6，7.6）。结论 SPTP多表现为体积较大、边界清楚、向胰腺外突出且伴有钙化的囊实性或实性肿块。病灶代谢特征多样，实性部分FDG多为高摄取，延迟显像后FDG摄取无明显变化。

Objective To summarize the imaging features and metabolic characteristics of solid pseudopapillary tumors of the pancreas （SPTP） using ^18F-FDG PET/CT in order to improve the diagnostic accuracy.Methods ^18F-FDG PET/CT findings and clinical data of 16 patients （3 males, 13 females, average age 38.6 years） pathologically proved SPTP from August 2010 to June 2014 in Shanghai Changhai Hospital were analyzed retrospectively. The morphology, density and metabolic characteristics of the lesions were observed, and SUVmax and tumor size were measured and recorded. The difference between early SUVmax and delayed SUVmax was evaluated with paired t test in 10 patients underwent dual-time scans, and the retention index （RI） was also calculated.Results The lesions were all single with well delineated and exogenous growth. The long diameter of the tumors was about 1.2-10.4（4.0±2.7） cm, and the short diameter was 1.0-8.6（3.3±2.2） cm. Four tumors were nearly completely solid, in which 2 lesions showed high and uniform FDG accumulation, 1 inhomogeneous high metabolic lesion, and 1 with FDG uptake similar to normal pancreas. The other 12 cases demonstrated solid and cystic mixed structures which showed uneven high metabolic components in mural nodules mixed with mild metabolic and/or uptake defect. The early SUVmax of all patients was 7.3±6.8（2.4-29.1）. For the 10 patients with dual-phase scans, no statistical difference was seen between the early SUVmax （6.0±3.4） and the delayed SUVmax（6.4±3.2）（t=-1.658, P〉0.05）; RI was 6.9%（-4.2%, 13.6%）. Among the 16 patients, 5 were found to have invasion of pancreatic duct or surrounding organs of pancreas, with early SUVmax （6.7±4.1）（3.4-13.1）, SUVmax of remaining 11 patients was 4.4（2.6, 7.6）.Conclusions SPTP is mostly cystic-solid or solid lesions with big volumes, calcification, well-defined borders and outward swelling. On FDG PET images, there are diverse metabolic characteristics of lesions, with high uptake on the solid part, and few changes of FDG uptake on the delayed scan.