用正弦激活网络提升3D光声成像的频带与分辨率,实现快速高清成像。
Implicit Spatiotemporal Bandwidth Enhancement Filter by Sine-activated Deep Learning Model for Fast 3D Photoacoustic Tomography
- 引入正弦激活函数,从有限频带数据中恢复高频率信号
- 在-12 dB处实现全频带响应,信噪比显著提升
- 支持每秒2帧的快速成像,适合动态目标观测
采用高频半球形探头的3D光声断层成像(3D-PAT)具备近全向接收能力,能灵敏捕捉宽带光声信号中的细微结构。但受限于通道数和采样率,传感器常呈稀疏且带宽受限,影响图像质量。为此,本文重新审视直接对传感器级光声射频数据(PARF)应用二维深度学习的方法,提出在模型中引入正弦激活函数,以从观测到的带限高频PARF数据中重建宽带特性。由于真实3D训练数据稀缺,采用随机球形吸收体模拟训练数据,并结合正弦激活机制,强调频带学习而非数据记忆。在叶脉仿体、微CT验证的3D螺旋仿体及人体手掌血管的活体测试中,该方法展现出良好泛化能力,有效提升传感器密度并恢复时空频带。定性上,正弦激活模型显著增强高频成分,血管结构更清晰、伪影更少;定量上,在-12 dB处达到全频带响应,对比度噪声比更高,结构相似性损失极小。最后,优化后系统实现每秒2体积的快速增强成像,适用于自由运动目标的实时成像。
原文摘要 · Abstract (English)
3D photoacoustic tomography (3D-PAT) using high-frequency hemispherical transducers offers near-omnidirectional reception and enhanced sensitivity to the finer structural details encoded in the high-frequency components of the broadband photoacoustic (PA) signal. However, practical constraints such as limited number of channels with bandlimited sampling rate often result in sparse and bandlimited sensors that degrade image quality. To address this, we revisit the 2D deep learning (DL) approach applied directly to sensor-wise PA radio-frequency (PARF) data. Specifically, we introduce sine activation into the DL model to restore the broadband nature of PARF signals given the observed band-limited and high-frequency PARF data. Given the scarcity of 3D training data, we employ simplified training strategies by simulating random spherical absorbers. This combination of sine-activated model and randomized training is designed to emphasize bandwidth learning over dataset memorization. Our model was evaluated on a leaf skeleton phantom, a micro-CT-verified 3D spiral phantom and in-vivo human palm vasculature. The results showed that the proposed training mechanism on sine-activated model was well-generalized across the different tests by effectively increasing the sensor density and recovering the spatiotemporal bandwidth. Qualitatively, the sine-activated model uniquely enhanced high-frequency content that produces clearer vascular structure with fewer artefacts. Quantitatively, the sine-activated model exhibits full bandwidth at -12 dB spectrum and significantly higher contrast-to-noise ratio with minimal loss of structural similarity index. Lastly, we optimized our approach to enable fast enhanced 3D-PAT at 2 volumes-per-second for better practical imaging of a free-moving targets.
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