一位無症狀之51歲男性接受氟－18-去氧葡萄糖正子攝影作為健康檢查與癌症篩檢的一部份。正子攝影顯示左側睪丸比右側睪丸放射活性增加，因此懷疑左側睪丸之疾患而安排進一步檢查。後續檢查排除左側睪丸之疾患且顯示右側為一萎縮睪丸，導致氟－18-去氧葡萄糖攝取減少，造成睪丸攝取不對稱的情形。就吾人所知，睪丸萎縮導致氟化去氧葡萄糖攝取減少尚未被報導。在判讀睪丸不對稱之氟－18-去氧葡萄糖攝取活性時，須注意單側萎縮睪丸導致攝取減少的可能性。

We present an asymptomatic 51-year-old man who underwent a FDG-PET scan as a part of health checkup for cancer screening. The FDG-PET scan showed higher radioactivity in the left testis than in the right one and left testicular disorder was thus suspected. Following examinations of testes ruled out diseased left testis and revealed an atrophic right testis, which resulted in a decrease in FDG uptake and asymmetric picture. To our knowledge, testicular atrophy causing decrease in FDG uptake has not yet been reported. In reading a picture of asymmetric testicular FDG activity, the possibility of unilateral atrophic testis that absorbs less radioactivity should be kept in mind.