X-ray induced acoustic computed tomography (XACT) utilized the ultrasound generated by the thermoelastic effect to reconstruct the x-ray absorption distribution of tissues. In this Letter, we propose a method for mechanical characterization of osteoporosis based on an XACT technique. The theoretical and simulation studies were performed on the influence of elasticity effect on x-ray induced acoustic (XA) generation. The images of normal and osteoporotic bones reconstructed by the simulated XACT were found to be in good agreement with micro-CT. Furthermore, through XA signal analysis, the rise time of tissue displacement can be obtained to characterize the elasticity of bone tissues. Experimental results demonstrated that this method can provide structural and mechanical information of bone tissues, which has future potentials for assessment of bone in osteoporosis.

Photoacoustic (PA) imaging is a non-invasive imaging technique with high optical resolution and acoustic penetration depth, which has been widely used in medical and clinical researches. As an important part in functional PA imaging, photoacoustic mechanical imaging (PAMI) has great potential in visualizing and understanding the local development of pathological process. This review provides lots of PA breakthroughs which have been made in elasticity detection, viscosity detection, and viscoelasticity detection through PAMI techniques. The current research problems, challenges and future development directions were discussed.

The Manipulation of g^(2)(0) peak value of Hanbury Brown-Twiss (HBT) effect is discussed with a holographic projection scheme. By the aid of target pattern artificially designed in the projection imaging system, the statistical distribution of projection pattern will be highly controllable. In this work, we theoretically point out key factors influencing the g^(2)(0) peak value of HBT effect in a single-lens incoherent imaging system. We find the peak value is not only decided by statistical property and coherence length of target pattern but also depends on the intrinsic characteristics of projection system, such as numerical aperture and projection quality. Then, we experimentally measured the g^(2)(0) peak value of HBT effect with a phase-only holographic projection scheme and demonstrate the applicability of our theoretical analysis on the holographic scheme. Here, the super-bunching effect in the projection plane has been observed, when target patterns originated from chaotic speckle or it's function transformation patterns. Moreover, we design some sparse target patterns, whose holographic reconstruction patterns show the super-bunching effect achieving g^(2)(0)=39.77. Finally, we discussed the positive influence of holographic noise on increasing the g^(2)(0) peak value. The presented work predicting the peak value of HBT effect not only is applicable for the lens imaging system but also in other projection systems, such as the holographic projection.

Computer-generated holography (CGH) enables on-demand scaling and projection of artificially designed target patterns, offering distinct advantages such as a lensless configuration and high-frame-rate operation. In this work, we actively manipulate projection patterns via CGH to integrate two representative single-pixel imaging (SPI) schemes, thereby establishing a ghost imaging (GI) framework with flexibly tunable properties. Specifically, reference signals derived from computational holography and their corresponding bucket signals are processed using an intensity correlation algorithm, enabling the simultaneous reconstruction of image results across multiple GI schemes. Experimentally, we demonstrate the method using two types of target patterns: intensity-squared chaotic speckle patterns and artificially designed sparse patterns. The results exhibit varying degrees of improvement in image visibility and contrast-to-noise ratio. Moreover, by designing mirror-symmetric target patterns, we successfully achieve positive and negative ghost image copies through holographic projection. Consequently, this integrated, lensless GI approach based on holographic projection not only fulfills the requirement for customizable projection patterns in practical applications but also provides the high-frame-rate sampling capability essential for multi-frame intensity correlation measurements.

In a lens-assisted imaging scheme with speckle illumination, the spatial resolution can surpass the Rayleigh resolution limit by a factor of $\sqrt{2}$ with second-order auto-correlation of light intensity. In this work, integrated with the nonlinear structured illumination after the speckle sinusoidally modulated, the second-order auto-correlation imaging can surpass the Rayleigh resolution limit by a factor of $2+\sqrt{2}$. In theory, a higher spatial resolution with the surpassing factor $N+\sqrt{N}$ is available by the $N$-order auto-correlation measurement. Our imaging scheme combined two super-resolution technologies not only enhances the spatial resolution of the lens-assisted imaging, but also promotes the practicality of the intensity correlation imaging.