School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA.
Department of Cardiovascular Surgery, Children's Hospital Boston, Boston, MA, USA.
Int J Comput Assist Radiol Surg. 2018 May;13(5):721-729. doi: 10.1007/s11548-018-1729-3. Epub 2018 Mar 16.
High dynamic range (HDR) imaging is a popular computational photography technique that has found its way into every modern smartphone and camera. In HDR imaging, images acquired at different exposures are combined to increase the luminance range of the final image, thereby extending the limited dynamic range of the camera. Ultrasound imaging suffers from limited dynamic range as well; at higher power levels, the hyperechogenic tissue is overexposed, whereas at lower power levels, hypoechogenic tissue details are not visible. In this work, we apply HDR techniques to ultrasound imaging, where we combine ultrasound images acquired at different power levels to improve the level of detail visible in the final image.
Ultrasound images of ex vivo and in vivo tissue are acquired at different acoustic power levels and then combined to generate HDR ultrasound (HDR-US) images. The performance of five tone mapping operators is quantitatively evaluated using a similarity metric to determine the most suitable mapping for HDR-US imaging.
The ex vivo and in vivo results demonstrated that HDR-US imaging enables visualizing both hyper- and hypoechogenic tissue at once in a single image. The Durand tone mapping operator preserved the most amount of detail across the dynamic range.
Our results strongly suggest that HDR-US imaging can improve the utility of ultrasound in image-based diagnosis and procedure guidance.
高动态范围（HDR）成像是一种流行的计算摄影技术，已应用于现代智能手机和相机中。在 HDR 成像中，通过组合不同曝光获取的图像来增加最终图像的亮度范围，从而扩展相机有限的动态范围。超声成像是一种常见的医疗成像技术，也存在动态范围有限的问题；在较高的功率水平下，强回声组织会过亮，而在较低的功率水平下，弱回声组织的细节则不可见。在这项工作中，我们将 HDR 技术应用于超声成像中，通过组合不同功率水平获取的超声图像来提高最终图像中可见的细节水平。
在不同的声功率水平下获取离体和体内组织的超声图像，然后将其组合以生成 HDR 超声（HDR-US）图像。使用相似性度量来定量评估五种色调映射算子的性能，以确定最适合 HDR-US 成像的映射。
离体和体内结果表明，HDR-US 成像能够在单个图像中同时可视化高回声和低回声组织。Durand 色调映射算子在整个动态范围内保留了最多的细节。
我们的结果强烈表明，HDR-US 成像可以提高超声在基于图像的诊断和手术引导中的应用价值。
