Browne Jacinta E, Watson Amanda J, Hoskins Peter R, Elliott Alex T
Department of Clinical Physics, Western Infirmary, Glasgow, UK.
Ultrasound Med Biol. 2005 Jul;31(7):957-64. doi: 10.1016/j.ultrasmedbio.2005.03.012.
Tissue harmonic imaging (THI) has been reported to improve contrast resolution, tissue differentiation and overall image quality in clinical examinations. However, a study carried out previously by the authors (Brown et al. 2004) found improvements only in spatial resolution and not in contrast resolution or anechoic target detection. This result may have been due to the homogeneity of the phantom. Biologic tissues are generally inhomogeneous and THI has been reported to improve image quality in the presence of large amounts of subcutaneous fat. The aims of the study were to simulate the distortion caused by subcutaneous fat to image quality and thus investigate further the improvements reported in anechoic target detection and contrast resolution performance with THI compared with 2D conventional imaging. In addition, the effect of three different types of fat-mimicking layer on image quality was examined. The abdominal transducer of two ultrasound scanners with 2D conventional imaging and THI were tested, the 4C1 (Aspen-Acuson, Siemens Co., CA, USA) and the C5-2 (ATL HDI 5000, ATL/Philips, Amsterdam, The Netherlands). An ex vivo subcutaneous pig fat layer was used to replicate beam distortion and phase aberration seen clinically in the presence of subcutaneous fat. Three different types of fat-mimicking layers (olive oil, lard and lard with fish oil capsules) were evaluated. The subcutaneous pig fat layer demonstrated an improvement in anechoic target detection with THI compared with 2D conventional imaging, but no improvement was demonstrated in contrast resolution performance; a similar result was found in a previous study conducted by this research group (Brown et al. 2004) while using this tissue-mimicking phantom without a fat layer. Similarly, while using the layers of olive oil, lard and lard with fish oil capsules, improvements due to THI were found in anechoic target detection but, again, no improvements were found for contrast resolution for any of the layer combinations. Therefore, it was felt that the lack of improvement in contrast resolution performance may be due to the test phantom design and not to whether a layer was present that caused beam distortion and phase aberrations.
据报道，组织谐波成像（THI）可提高临床检查中的对比分辨率、组织分辨力和整体图像质量。然而，作者先前进行的一项研究（Brown等人，2004年）发现，仅在空间分辨率方面有所提高，而在对比分辨率或无回声目标检测方面没有改善。这一结果可能是由于体模的均匀性。生物组织通常是不均匀的，据报道，在存在大量皮下脂肪的情况下，THI可提高图像质量。本研究的目的是模拟皮下脂肪对图像质量造成的失真，从而进一步研究与二维传统成像相比，THI在无回声目标检测和对比分辨率性能方面所报道的改善情况。此外，还研究了三种不同类型的脂肪模拟层对图像质量的影响。对两台具有二维传统成像和THI功能的超声扫描仪的腹部探头进行了测试，分别是4C1（Aspen-Acuson，西门子公司，美国加利福尼亚州）和C5-2（ATL HDI 5000，ATL/飞利浦公司，荷兰阿姆斯特丹）。使用离体猪皮下脂肪层来复制临床上在存在皮下脂肪时所见到的波束失真和相位畸变。评估了三种不同类型的脂肪模拟层（橄榄油、猪油和含有鱼油胶囊的猪油）。与二维传统成像相比，猪皮下脂肪层显示出THI在无回声目标检测方面有所改善，但在对比分辨率性能方面没有改善；该研究小组先前在使用这种没有脂肪层的组织模拟体模时进行的一项研究（Brown等人，2004年）也发现了类似结果。同样，在使用橄榄油层、猪油层和含有鱼油胶囊的猪油层时，发现THI在无回声目标检测方面有所改善，但对于任何层组合，在对比分辨率方面均未发现改善。因此，认为对比分辨率性能缺乏改善可能是由于测试体模的设计，而不是由于是否存在导致波束失真和相位畸变的层。
