Branderhorst W, de Groot J E, Neeter L M F H, van Lier M G J T B, Neeleman C, den Heeten G J, Grimbergen C A
Department of Biomedical Engineering and Physics, Academic Medical Center, P.O. Box 22660, Amsterdam 1100 DD, The Netherlands and Sigmascreening B.V., Meibergdreef 45, Amsterdam 1105 BA, The Netherlands.
Department of Biomedical Engineering and Physics, Academic Medical Center, P.O. Box 22660, Amsterdam 1100 DD, The Netherlands.
Med Phys. 2016 Jan;43(1):518. doi: 10.1118/1.4939129.
In mammography, the height of the image receptor is adjusted to the patient before compressing the breast. An inadequate height setting can result in an imbalance between the forces applied by the image receptor and the paddle, causing the clamped breast to be pushed up or down relative to the body during compression. This leads to unnecessary stretching of the skin and other tissues around the breast, which can make the imaging procedure more painful for the patient. The goal of this study was to implement a method to measure and minimize the force imbalance, and to assess its feasibility as an objective and reproducible method of setting the image receptor height.
A trial was conducted consisting of 13 craniocaudal mammographic compressions on a silicone breast phantom, each with the image receptor positioned at a different height. The image receptor height was varied over a range of 12 cm. In each compression, the force exerted by the compression paddle was increased up to 140 N in steps of 10 N. In addition to the paddle force, the authors measured the force exerted by the image receptor and the reaction force exerted on the patient body by the ground. The trial was repeated 8 times, with the phantom remounted at a slightly different orientation and position between the trials.
For a given paddle force, the obtained results showed that there is always exactly one image receptor height that leads to a balance of the forces on the breast. For the breast phantom, deviating from this specific height increased the force imbalance by 9.4 ± 1.9 N/cm (6.7%) for 140 N paddle force, and by 7.1 ± 1.6 N/cm (17.8%) for 40 N paddle force. The results also show that in situations where the force exerted by the image receptor is not measured, the craniocaudal force imbalance can still be determined by positioning the patient on a weighing scale and observing the changes in displayed weight during the procedure.
In mammographic breast compression, even small changes in the image receptor height can lead to a severe imbalance of the applied forces. This may make the procedure more painful than necessary and, in case the image receptor is set too low, may lead to image quality issues and increased radiation dose due to undercompression. In practice, these effects can be reduced by monitoring the force imbalance and actively adjusting the position of the image receptor throughout the compression.
在乳腺钼靶摄影中，在对乳房进行压迫之前，需将图像接收器的高度调整至与患者适配。高度设置不当会导致图像接收器和压迫板施加的力失衡，致使被夹住的乳房在压迫过程中相对于身体向上或向下移动。这会导致乳房周围皮肤和其他组织不必要的拉伸，从而使成像过程对患者而言更加痛苦。本研究的目的是实施一种测量并最小化力失衡的方法，并评估其作为一种客观且可重复的设置图像接收器高度的方法的可行性。
对一个硅胶乳房模型进行了13次头尾位乳腺钼靶压迫试验，每次试验中图像接收器处于不同高度。图像接收器高度在12厘米范围内变化。在每次压迫中，压迫板施加的力以10牛的步长增加至140牛。除了压迫板的力，作者还测量了图像接收器施加的力以及地面施加在患者身体上的反作用力。该试验重复了8次，每次试验之间模型重新安装在略有不同的方向和位置。
对于给定的压迫板力，所得结果表明总是恰好存在一个图像接收器高度能使乳房上的力达到平衡。对于乳房模型，偏离这个特定高度会使140牛压迫板力时的力失衡增加9.4±1.9牛/厘米（6.7%），40牛压迫板力时增加7.1±1.6牛/厘米（17.8%）。结果还表明，在未测量图像接收器施加的力的情况下，通过让患者站在体重秤上并观察过程中显示体重的变化，仍可确定头尾位力失衡情况。
在乳腺钼靶乳房压迫中，即使图像接收器高度的微小变化也会导致施加力的严重失衡。这可能使该过程比必要情况更痛苦，并且如果图像接收器设置过低，可能会导致图像质量问题以及因压迫不足而增加辐射剂量。在实际操作中，通过监测力失衡并在整个压迫过程中主动调整图像接收器的位置，可以减少这些影响。
