Lu Yihuan, Peng Boyu, Lau Beverly A, Hu Yue-Houng, Scaduto David A, Zhao Wei, Gindi Gene
Department of Electrical & Computer Engineering, Stony Brook University, NY 11794 USA.
Phys Med Biol. 2015 Aug 21;60(16):6323-54. doi: 10.1088/0031-9155/60/16/6323. Epub 2015 Aug 3.
Contrast-enhanced dual energy digital breast tomosynthesis (CE-DE-DBT) is designed to image iodinated masses while suppressing breast anatomical background. Scatter is a problem, especially for high energy acquisition, in that it causes severe cupping artifact and iodine quantitation errors. We propose a patient specific scatter correction (SC) algorithm for CE-DE-DBT. The empirical algorithm works by interpolating scatter data outside the breast shadow into an estimate within the breast shadow. The interpolated estimate is further improved by operations that use an easily obtainable (from phantoms) table of scatter-to-primary-ratios (SPR)--a single SPR value for each breast thickness and acquisition angle. We validated our SC algorithm for two breast emulating phantoms by comparing SPR from our SC algorithm to that measured using a beam-passing pinhole array plate. The error in our SC computed SPR, averaged over acquisition angle and image location, was about 5%, with slightly worse errors for thicker phantoms. The SC projection data, reconstructed using OS-SART, showed a large degree of decupping. We also observed that SC removed the dependence of iodine quantitation on phantom thickness. We applied the SC algorithm to a CE-DE-mammographic patient image with a biopsy confirmed tumor at the breast periphery. In the image without SC, the contrast enhanced tumor was masked by the cupping artifact. With our SC, the tumor was easily visible. An interpolation-based SC was proposed by (Siewerdsen et al 2006 Med. Phys. 33 187-97) for cone-beam CT (CBCT), but our algorithm and application differ in several respects. Other relevant SC techniques include Monte-Carlo and convolution-based methods for CBCT, storage of a precomputed library of scatter maps for DBT, and patient acquisition with a beam-passing pinhole array for breast CT. Our SC algorithm can be accomplished in clinically acceptable times, requires no additional imaging hardware or extra patient dose and is easily transportable between sites.
对比增强双能数字乳腺断层合成（CE-DE-DBT）旨在对碘化肿块进行成像，同时抑制乳腺解剖背景。散射是一个问题，特别是对于高能量采集，因为它会导致严重的杯状伪影和碘定量误差。我们提出了一种针对CE-DE-DBT的患者特异性散射校正（SC）算法。该经验算法通过将乳腺阴影外的散射数据内插到乳腺阴影内的估计值来工作。通过使用一个易于获得的（来自体模）散射与原发射线比（SPR）表（每个乳腺厚度和采集角度有一个SPR值）的操作，进一步改进内插估计值。我们通过将我们的SC算法得到的SPR与使用光束穿透针孔阵列板测量的SPR进行比较，对两个乳腺模拟体模验证了我们的SC算法。我们计算的SC的SPR在采集角度和图像位置上的平均误差约为5%，较厚的体模误差稍大。使用OS-SART重建的SC投影数据显示出很大程度的去杯状伪影。我们还观察到SC消除了碘定量对体模厚度的依赖性。我们将SC算法应用于一名CE-DE乳腺钼靶患者图像，该患者乳腺周边有活检证实的肿瘤。在没有SC的图像中，对比增强的肿瘤被杯状伪影掩盖。使用我们的SC算法后，肿瘤很容易看到。（Siewerdsen等人，2006年，《医学物理》33卷，187 - 97页）针对锥束CT（CBCT）提出了一种基于插值的SC算法，但我们的算法和应用在几个方面有所不同。其他相关的SC技术包括用于CBCT的蒙特卡洛和基于卷积的方法、用于DBT的预计算散射图库的存储以及用于乳腺CT的使用光束穿透针孔阵列的患者采集。我们的SC算法可以在临床可接受的时间内完成，不需要额外的成像硬件或额外的患者剂量，并且很容易在不同地点之间传输。
