Effects on image quality of a 2D antiscatter grid in x-ray digital breast tomosynthesis: Initial experience using the dual modality (x-ray and molecular) breast tomosynthesis scanner.
Effects on image quality of a 2D antiscatter grid in x-ray digital breast tomosynthesis: Initial experience using the dual modality (x-ray and molecular) breast tomosynthesis scanner.
复制标题
X 射线数字乳腺断层合成中 2D 防散射网格对图像质量的影响：使用双模态（X 射线和分子）乳腺断层合成扫描仪的初步经验。
DOI：
10.1118/1.4943632
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发表时间：
2016
期刊：
影响因子：
3.8
通讯作者：
Williams,MarkB
中科院分区：
文献类型：
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作者：
Patel,Tushita;Peppard,Heather;Williams,MarkB
数字乳腺断层合成摄影（DBT）中乳腺散射的辐射会导致图像退化，包括癌组织和背景组织之间的对比度损失。与二维（2D）乳腺X线摄影不同，DBT中不能轻易使用防散射滤线栅，因为在扫描过程中改变射线管和探测器之间的对准会导致不可接受的初级辐射损失。但是，在结合了DBT和分子乳腺断层合成的双模态乳腺断层合成（DMT）扫描仪中，射线管和探测器围绕公共轴旋转，从而保持固定的射线管-探测器对准。这种C形臂几何结构提高了使用2D（细胞）聚焦抗散射滤线栅的可能性。本研究的目的是评估图像质量的变化时，使用的DBT部分的DMT扫描条件下的固定辐射dose.MethodsTwo 2D聚焦原型网格与80厘米的焦距进行了测试，一个堆栈层压铜（Cu）和一个铸造钨聚合物（W-聚）。使用旨在最大化初级X射线光子传输的运动方案进行往复运动。测量模拟30%、50%和70%腺体组织组成的矩形材料块的网格输入和网格输出散射-原发比（SPR）。为了通过增加网格来评估图像质量的变化，计算机化成像参考系统公司，使用011 A型体模，其中包含一组1cm厚的块，模拟腺体/脂肪比范围为0/100至100/0。为了模拟6.5和8.5 cm厚的压缩乳房，将1 cm厚的PMMA切片添加到011 A型体模中。在有和没有网格的情况下获得DBT图像，对于给定的压缩厚度，曝光参数是固定的。从重建的体模images.ResultsFor 4，6，和8 cm组织等效块体模厚度，包含W-poly网格减少SPR的因素5，6，和5.8，分别为所有块的信噪比（SDNR），对比度，和体素值为基础的衰减系数（μ）进行测量。对于相同的厚度，铜网格将SPR降低了3.9、4.5和4.9倍。对于011 A体模，W-聚乙烯网格将70/30块的SDNR分别从0.8、−0.32和−0.72提高到4.5、6.5和8.5 cm体模的0.9、0.76和0.062。对于4.5、6.5和8.5 cm体模，它将100/0块的SDNR分别从3.78、1.95和1.0提高到3.79、3.67和3.25。包含W-poly网格提高了所有组织块组成的基于图像的μ值的准确性。然而，由于有限的角度采样，跨切片的衰减涂抹降低了体素值的灵敏度，以改变成分相比，理论μvalues.ConclusionsUnder条件下，固定的辐射剂量的乳房，使用2D聚焦网格增加对比度，SDNR，估计衰减的准确性质量模拟块组成的所有体模厚度测试，与程度的改善取决于材料的组成。2D防散射滤线栅可以有效地结合在采用完全等中心管探测器旋转的DBT系统中。
PurposeRadiation scattered from the breast in digital breast tomosynthesis (DBT) causes image degradation, including loss of contrast between cancerous and background tissue. Unlike in 2‐dimensional (2D) mammography, an antiscatter grid cannot readily be used in DBT because changing alignment between the tube and detector during the scan would result in unacceptable loss of primary radiation. However, in the dual modality breast tomosynthesis (DMT) scanner, which combines DBT and molecular breast tomosynthesis, the tube and detector rotate around a common axis, thereby maintaining a fixed tube‐detector alignment. This C‐arm geometry raises the possibility of using a 2D (cellular) focused antiscatter grid. The purpose of this study is to assess change in image quality when using an antiscatter grid in the DBT portion of a DMT scan under conditions of fixed radiation dose.MethodsTwo 2D focused prototype grids with 80 cm focal length were tested, one stack‐laminated from copper (Cu) and one cast from a tungsten‐polymer (W‐poly). They were reciprocated using a motion scheme designed to maximize transmission of primary x‐ray photons. Grid‐in and grid‐out scatter‐to‐primary ratios (SPRs) were measured for rectangular blocks of material simulating 30%, 50%, and 70% glandular tissue compositions. For assessment of changes in image quality through the addition of a grid, the Computerized Imaging Reference Systems, Inc., phantom Model 011A containing a set of 1 cm thick blocks simulating a range of glandular/adipose ratios from 0/100 to 100/0 was used. To simulate 6.5 and 8.5 cm thick compressed breasts, 1 cm thick slices of PMMA were added to the Model 011A phantom. DBT images were obtained with and without the grid, with exposure parameters fixed for a given compressed thickness. Signal‐difference‐to‐noise ratios (SDNRs), contrast, and voxel value‐based attenuation coefficients (μ) were measured for all blocks from reconstructed phantom images.ResultsFor 4, 6, and 8 cm tissue‐equivalent block phantom thicknesses, the inclusion of the W‐poly grid reduced the SPR by factors of 5, 6, and 5.8, respectively. For the same thicknesses, the copper grid reduced the SPR by factors of 3.9, 4.5, and 4.9. For the 011A phantom, the W‐poly grid raised the SDNR of the 70/30 block from 0.8, −0.32, and −0.72 to 0.9, 0.76, and 0.062 for the 4.5, 6.5, and 8.5 cm phantoms, respectively. It raised the SDNR of the 100/0 block from 3.78, 1.95, and 1.0 to 3.79, 3.67, and 3.25 for the 4.5, 6.5, and 8.5 cm phantoms, respectively. Inclusion of the W‐poly grid improved the accuracy of image‐basedμvalues for all block compositions. However, smearing of attenuation across slices due to limited angular sampling decreases the sensitivity of voxel values to changing composition compared to theoreticalμvalues.ConclusionsUnder conditions of fixed radiation dose to the breast, use of a 2D focused grid increased contrast, SDNR, and accuracy of estimated attenuation for mass‐simulating block compositions in all phantom thicknesses tested, with the degree of improvement depending upon material composition. A 2D antiscatter grid can be usefully incorporated in DBT systems that employ fully isocentric tube‐detector rotation.