Jerushalmi Jacqueline, Frenkel Alex, Bar-Shalom Rachel, Khoury Jabour, Israel Ora
Department of Nuclear Medicine, Western Galilee Hospital, Nahariya, Israel.
J Nucl Med. 2009 Jun;50(6):849-53. doi: 10.2967/jnumed.108.058586. Epub 2009 May 14.
(18)F-FDG uptake in the thymus, mainly related to hyperplasia after chemotherapy, has been described. Thymic uptake can challenge the accurate assessment of cancer patients by (18)F-FDG imaging. The present study defines the incidence, patterns, and intensity of thymic (18)F-FDG uptake in relationship to age and time after treatment in a large cohort of patients.
A total of 559 consecutive (18)F-FDG PET/CT studies in 160 patients (86 men, 74 women; age, 3-40 y) performed at baseline, during treatment, at the end of treatment, and during follow-up were retrospectively reviewed. PET/CT studies were assessed for the presence or absence (T+ or T-, respectively), pattern, and intensity (SUVmax) of increased (18)F-FDG uptake in the anterior mediastinum, localized by the CT component to the thymus. The overall incidence of (18)F-FDG avidity in the thymus in relationship to the patient's age and time after treatment administration were statistically evaluated.
There were 137 of 559 T+ studies (25%), with equal sex distribution. T+ studies were found in significantly younger patients (20.6 +/- 9.3 y vs. 27.4 +/- 8.4 y, P < 0.001). Most T+ patients (60%) showed an inverted V pattern of thymic uptake, with additional unilateral mediastinal extension in 24% and focal midline uptake in 16% of studies. T+ studies were encountered in 80% of patients younger than 10 y, compared with 8% of patients in the 31- to 40-y age group. There were 17% T+ studies at baseline, 6% during treatment, 8% at the end of treatment, and 27%-40% during follow-up. The average SUVmax of thymic (18)F-FDG uptake was 3.73 +/- 1.22.
Thymic (18)F-FDG uptake was found in 28% of the present study population, more frequently after treatment. T+ patients were significantly younger. Thymic uptake was found in 73% of untreated patients up to the age of 13 y and in 8% of patients in the fourth decade of life. Knowledge of this age- and treatment-related incidence of physiologic thymic (18)F-FDG avidity can reduce the number of potential pitfalls in reporting PET/CT studies in cancer patients.
已描述过胸腺中（18）F-FDG摄取，主要与化疗后的增生有关。胸腺摄取可通过（18）F-FDG成像对癌症患者的准确评估构成挑战。本研究在一大群患者中确定了胸腺（18）F-FDG摄取的发生率、模式和强度与年龄及治疗后时间的关系。
回顾性分析了160例患者（86例男性，74例女性；年龄3至40岁）连续进行的559次（18）F-FDG PET/CT研究，这些研究在基线、治疗期间、治疗结束时及随访期间进行。通过CT部分定位到胸腺，评估PET/CT研究中前纵隔（18）F-FDG摄取增加的存在与否（分别为T+或T-）、模式和强度（SUVmax）。对胸腺中（18）F-FDG摄取与患者年龄及治疗给药后时间的总体发生率进行统计学评估。
559项T+研究中有137项（25%），性别分布均等。T+研究在明显更年轻的患者中出现（20.6±9.3岁对27.4±8.4岁，P<0.001）。大多数T+患者（60%）表现出胸腺摄取的倒V形模式，24%的研究中有额外的单侧纵隔延伸，16%的研究中有局灶性中线摄取。10岁以下患者中80%出现T+研究，而31至40岁年龄组患者中这一比例为8%。基线时T+研究占17%，治疗期间占6%，治疗结束时占8%，随访期间占27%-40%。胸腺（（18）F-FDG摄取的平均SUVmax为3.73±1.22。
本研究人群中28%发现有胸腺（18）F-FDG摄取，治疗后更常见。T+患者明显更年轻。13岁以下未治疗患者中73%发现有胸腺摄取，40岁患者中这一比例为8%。了解这种与年龄和治疗相关的生理性胸腺（18）F-FDG摄取发生率，可减少癌症患者PET/CT研究报告中潜在陷阱的数量。
