Low attenuation lesion：低密度病变；低密度灶

密度。胸部增强CT显示，肺动脉干水平的不均质胸腺瘤。箭头所示为肿瘤中多个低密度区中的两个。
Attenuation. Contrast-enhanced chest computed tomography (CT) (soft tissue window) of a heterogeneous thymoma at the level of the pulmonary trunk. Arrows point to two of the many small low attenuation regions within the mass.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6131232/

低密度肿块
低密度肿块的英文译词
Low attenuation masses
http://www.scidict.org/items/低密度肿块.html

（1）大块状融合病灶2例：病理结果分别为肝细胞的大块状坏死和聚合的结节样再生。CT平扫相应表现为地图样分布的低密度和高密度区；
1 ） Massive confluent aggregate loci in 2 patients demonstrated low attenuation and high attenuation as geographical patterns on CT scans betore contrast enhancement, respectively.
https://qikan.cqvip.com/Qikan/Article/Detail?id=38024151
(打开链接后请按 “展开更多” 和 MORE 来看全文)

肝内低密度灶是否要紧，主要取决于病变的性质。肝内低密度灶是肝脏CT的一种异常表现，临床上很多疾病在肝脏CT上，都可以表现为肝脏低密度灶。这些病变有些是良性病变，有些是恶性病变；...
https://baike.baidu.com/item/肝低密度灶/49984710#:~:text=肝内低密度灶是肝...

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Note added at 21 hrs (2023-03-31 05:50:42 GMT)
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回答 Asker:
attenuation 的解释是 “衰减”，意思是X光经过一物体后其强度会衰减。经过低密度物体后，其衰减就低。经过高密度物体后，其衰减就高。
low attenuation 的意思是 “使X光衰减低”。Low attenuation lesion 是 “使X光衰减低的病变”，即 “低密度病变”。

X射线穿过物质之后，强度会衰减。前面已经指出，这是因为X射线同物质相互作用时经历各种复杂的物理、化学过程，从而引起各种效应转化了入射线的部分能量。
https://atc.scnu.edu.cn/xrd/BOOK01/Book1-105.htm

Attenuation is the reduction of the intensity of an x-ray beam as it traverses matter. The reduction may be caused by absorption or by deflection (scatter) of photons from the beam and can be affected by different factors such as beam energy and atomic number of the absorber.
https://pubs.rsna.org/doi/10.1148/radiographics.18.1.9460114...

The density of the tissue is in proportion to the attenuation of the x-rays which pass through. Tissues like air and water have little attenuation and are displayed as low densities (dark), whereas bone has high attenuation and is displayed as high density (bright) on CT.
https://case.edu/med/neurology/NR/CT Basics.htm