乳腺筛查X射线成像参数与辐射剂量和影像质量的相关性研究

Correlation between image quality and radiation dose on screening mammography

目的探讨乳腺筛查X射线摄影参数对辐射剂量与影像质量的影响，以获取辐射剂量与影像质量的最佳匹配。方法回顾性分析接受数字乳腺X射线筛查摄影的507例受检者的曝光参数与平均腺体剂量的相关性。对不同厚度的亚克力板进行曝光，获取乳腺压迫厚度对辐射剂量的影响。通过对比度细节测试模体（CDMAM3．4）与不同厚度亚克力板的组合测试，分析其与影像质量的相关性。结果在507例受检者中，30～49岁为乳腺筛查影像受检者的主体人群，占67．06％。3种曝光模式下，平均腺体剂量（AGD）的均值以对比度优先模式最高，为标准模式的137．5％。标准模式靶物质／滤过板组合是Mo／Mo、Mo／Rh、Rh／Rh共3种，各占1／3；剂量优先模式选择的是Mo／Rh、Rh／Rh2种组合，各占50％；对比度优先模式则以选择Mo／Mo组合为主，占52％。乳腺压迫厚度与平均腺体剂量之间均呈正相关。3种曝光模式的逆影像质量指数（IQFinv）分别为98．32、95．41和107．02，其中对比度优先模式的IQFinv值最高；但当亚克力板增加到≥5cm时，3种曝光模式下的IQFinv值很接近。结论当受检者乳腺属于致密型乳腺且压迫厚度〈4cm时，应选择剂量优先曝光模式；〉4cm而〈6cm时，选择标准曝光模式；〉6cm选择手动。

Objective To obtain the matched parameters between image quality and radiation dose by exploring the influence of the exposure parameters of screening mammography on both the image quality and radiation dose. Methods The correlation between the exposure parameters and average glandular doses to 507 patients undergoing screening mammography were retrospectively analyzed. The influence of breast compression thickness on radiation dose by exposing different thickness of PMMA was obtained. The correlation with image quality was analyzed by combined testing of contrast detail test mode （CDMAM3.4） and different thickness of PMMAs. Results The groups aged 30 to 49 years were the main groups in 507 examined patients, up to 67.06% of the total. The mean value of average gland doses （AGD） in contrastprior mode was the highest in three kinds of exposure modes, accounting for 137.5% of standard mode. In standard mode, target material/filtration board combination was Mo/Mo, Mo/Rh and Rh/Rh, accounting for 1/3 respectively. Mo/Rh and Rh/Rh were selected in dose-prior mode, accounting for 50% respectively. Mo/Mo was mainly selected in contrast-prior, accounting for 52%. Breast compression thickness was positively correlated with average gland doses. Image quality figure inverse （IQFinv） under three kinds of modes （STD,DOSE,CNT） was 98. 32, 95.41 and 107.02, respectively, and IQFinv of contrast-prior mode was the highest among them. [QFinv was in general agreement in the three kinds of exposure modes when the thickness of PMMA plates plates was greater than or equal to 5 cm. Conclusions In clinical practice, when the breast is of density type and pressed thickness is less than 4 cm, the dose-prior mode should be selected. When the pressed thickness is between 4 and 6 cm, the standard exposure mode should be selected. When the pressed thickness is larger than 6 cm, the manual mode should be selected.