The University of Texas Medical School, Department of Diagnostic and Interventional Imaging, Ultrasonics Laboratory, Houston, TX, USA.
Ultrason Imaging. 2010 Jul;32(3):190-8. doi: 10.1177/016173461003200306.
We have recently shown that the appearance of Axial-Shear Strain Elastograms (ASSEs) for the case of loosely-bonded, elliptical inclusions (like fibroadenomas in the breast) is unique and therefore has the potential to distinguish benign fibroadenomas from malignant tumors in the breast. The ASSEs were obtained using quasi-static axial compressions, in a like manner as in normal axial-strain elastography. However, strict axial compression is achieved most often only by computer-controlled acquisitions and not by more practical freehand acquisitions. In a freehand acquisition, the frame sequence may contain several frames that do not experience strict axial compression but may also experience rotation or shear deformations. In this paper, we demonstrate the importance of accounting for the type of deformation applied to a target tissue for the correct interpretation of the resulting ASSEs. Using freehand acquired in vivo examples, we show that such a frame experiencing rotation or shear deformations results in ASSEs that may potentially be misinterpreted. This may be far more detrimental compared to the corresponding axial elastogram frames that may only suffer from inferior image quality in terms of contrast-to-noise ratio (CNR). Further, we show that we may be able to eliminate these frames from a sequence of freehand acquired in vivo breast lesion data by implementing a special filtering scheme, thus significantly improving the reliability of the remaining ASSE frames. This work further suggests that under freehand conditions, frames have to be checked for the presence of undesirable deformations.
我们最近表明，对于松散结合的椭圆形内含物（如乳房中的纤维腺瘤），轴向剪切应变弹性图（ASSE）的出现是独特的，因此有可能将良性纤维腺瘤与乳房中的恶性肿瘤区分开来。ASSE 是通过准静态轴向压缩获得的，与正常轴向应变弹性成像的方式类似。然而，严格的轴向压缩通常仅通过计算机控制的采集来实现，而不是通过更实际的徒手采集来实现。在徒手采集过程中，帧序列可能包含多个帧，这些帧没有经历严格的轴向压缩，但也可能经历旋转或剪切变形。在本文中，我们证明了考虑施加到目标组织的变形类型对于正确解释所得 ASSE 的重要性。使用徒手获取的体内实例，我们表明，这种经历旋转或剪切变形的帧可能会导致 ASSE 被错误解释。与可能仅因对比度噪声比（CNR）而导致图像质量较差的相应轴向弹性图帧相比，这可能更为不利。此外，我们表明，我们可以通过实施特殊的滤波方案，从徒手获取的体内乳房病变数据序列中消除这些帧，从而显著提高剩余 ASSE 帧的可靠性。这项工作进一步表明，在徒手条件下，必须检查帧是否存在不理想的变形。
