研究目的
To decrease both the total acquisition time and the light dose to the sample in optical projection tomography (OPT) for longitudinal living model studies by improving the ordered subsets expectation maximization reconstruction algorithm.
研究成果
The improved OSEM reconstruction algorithm significantly reduces the number of projections and acquisition time in OPT while maintaining image quality comparable to FBP with many more projections. The precalibration method using DBP effectively avoids the need for postcalibration, speeding up the reconstruction process. This approach is beneficial for longitudinal in vivo studies by minimizing phototoxicity and other negative effects.
研究不足
The method may be limited by the specific biological model (zebrafish) and the pretreatment requirements to reduce optical scattering. The calibration process, although precalibration is introduced, might still require manual adjustments. The algorithm's performance could be affected by noise and artifacts in very low projection scenarios.
1：Experimental Design and Method Selection:
The study designed an improved ordered subsets expectation maximization (OSEM) reconstruction algorithm for OPT to reduce the number of projections and acquisition time. A precalibration method using direct back projection (DBP) algorithm was proposed to calibrate the imaging system before data acquisition.
2：Sample Selection and Data Sources:
Zebrafish specimens were used as the biological model. The specimens were pretreated by immersion in methanol and a benzyl alcohol and benzyl benzoate (BABB) mixture to reduce optical scattering.
3：List of Experimental Equipment and Materials:
The experimental setup included a dual-modality OPT system with bright-field and fluorescence illumination modules, a white-light LED, a diffuser, a specific wavelength laser with expansion lens and collimator, a rotation stage, an objective, an iris aperture, an emission filter, a tube lens, and a highly sensitive CCD camera. The specimen was fixed in a transparent tube filled with BABB.
4：Experimental Procedures and Operational Workflow:
The specimen was rotated stepwise, and projection images were acquired in transmission and fluorescence modes. For transmission OPT (tOPT), white light illuminated the specimen; for emission OPT (eOPT), a 550-nm laser excited fluorophores stained with Rhodamine B. Images were captured at different angular steps over 360 degrees. Preprocessing included illumination heterogeneity correction and image resizing. The OSEM algorithm was applied for reconstruction with iterative updates.
5：Data Analysis Methods:
Image quality was assessed using the structural similarity index (SSIM) to compare reconstructed images from OSEM and FBP algorithms. Statistical analysis included calculating SSIM values and variances for different projection subsets and iterations.
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