ディジタルマンモグラフィの輝尽性蛍光体プレート劣化による臨床画像への影響

摘要

近年日本人女性の罹患者数が増加するとともに死亡者数も同時に増加しているため社会的な問題になっている.さまざまな部位のがんにいえることであるが，乳がんにおいても早期発見，早期治療によって生存率が格段に高くなることが知られている.乳がんの早期発見には，マンモグラフィにおける検診が非常に有用であるが，乳がん診断の指標となる微小な石灰化ゃ低コントラストの腫瘤を描出するためには，精度の高い管理をされた乳房撮影装置や検診マンモグラフィ撮影認定診療放射線技師(以下，認定技師)による撮影が必要となる.%We noted that breast-like artifacts occur in photo-stimulable phosphor plates (PSPs) used for long periods in digital mammography systems. This prompted us to investigate the effects on mammography diagnoses of these artifacts. Our study took the form of a comparison between the images generated by along-term use PSP (four years use) and a short-term use PSP. First, an acrylic phantom and an in-house-made phantom for visual evaluation were imaged using X-ray PSPs under the same exposure conditions. They were then scanned under the same conditions to generate images. The mean values of the digital signals were measured in the 35 locations of region of interest present in the images of the acrylic phantom. The images of the in-house-made phantom were then visually evaluated by five certified experts, who examined 22 clinical images taken with both PSPs while referring to a visual evaluation scale. Differences were detected in all the evaluated items: the short-term use PSP gave a higher rate than the long-term use PSP (p<0.01), suggesting that long-term use PSPs might adversely affect the results of diagnostic mammography.