An estimated ~250,000 new cases of both invasive and non-invasive breast cancer were diagnosed in US women almost every year. To reduce the local recurrence rate, the breast conserving surgery (BCS) is widely used as the initial therapy, which is to excise the tumor with a rim of normal surrounding tissue such that no cancer cells remain at the cut margin, Patients with positive margin commonly require a second surgical procedure to obtain clear margins. To this end, optical-resolution photoacoustic microscopy (OR-PAM) with ultraviolet (UV) laser illumination (OR-UV-PAM) has been developed for providing label-free, high-resolution, and histology like imaging of fixed, unprocessed breast tissue. To further improve the performance of OR-UV-PAM, here, we introduce dual-view UV-PAM (DV-UV-PAM) to significantly improve the axial resolution, achieving three-dimensional (3D) resolution isotropy. We first use 0.5 μm polystyrene beads and carbon fibers to validate the resolution isotropy improvement. Imaging of mouse brain slices further demonstrates the improved resolution isotropy, revealing the 3D structure of cell nuclei in detail, which facilitates quantitative cell nuclear analysis.
KEYWORDS: 3D image processing, Deconvolution, Image resolution, Photoacoustic microscopy, In vivo imaging, Photoacoustic imaging, Microscopy, Resolution enhancement technologies, Point spread functions, 3D photoacoustic microscopy, Signal to noise ratio, Tissues, Ultrasonography
Acoustic-resolution photoacoustic microscopy (ARPAM) is a promising tool for deep imaging of biological tissues. Synthetic aperture focusing technique (SAFT) can improve the degraded lateral resolution in the out-of-focus region of ARPAM when using a high numerical aperture acoustic transducer. We previously reported a three-dimensional (3D) deconvolution technique to improve both lateral and axial resolutions in the focus region of ARPAM. In this work, we extended resolution enhancement of ARPAM to the out-of-focus region based on two dimensional SAFT combined with the 3D deconvolution (SAFT+Deconv). In both the focus and out-of-focus regions, depth-independent lateral and axial resolution after SAFT ensures a depth-independent point spread function for 3D deconvolution algorithm. In an extended depth of focus (DOF) of ∼2 mm, SAFT+Deconv ARPAM improves the −6 dB lateral resolutions from 65–700 μm to 20–29 μm, and the −6 dB axial resolutions from 35–42 μm to 12–19 μm. The signal-to-noise ratio is also increased by 6–30 dB. The enhanced resolution in extended DOF by SAFT+Deconv ARPAM may enable important applications in biomedical photoacoustic imaging.
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