Fast CT imaging using limited projections: Performance analysis of FBP and SIRT-FBP reconstruction on a...

Computed Tomography (CT) imaging requires significant time and a large data volume, particularly for 3D reconstruction using a 2D planar detector. To address this, we propose a fast-scanning technique with limited projections and compare two reconstruction methods: Filtered Back Projection (FBP) and a combination of FBP with Simultaneous Iterative Reconstruction Technique (SIRT). The study was conducted on an industrial X-ray CT system at the Department of Physics, Universitas Gadjah Mada. A cylindrical water phantom (4" diameter) containing four solid inserts, aluminium, PTFE, graphite, and acrylic, was scanned using six different projection counts: 360, 180, 144, 108, 72, and 36. Each reconstruction result was evaluated against the reference image (360 projections) using mean square error (MSE), structural similarity index (SSIM), and signal-to-noise ratio (SNR). SIRT-FBP produced smoother images with less noise (SNR ≥20.33 dB, SSIM ≈ 0.9), while FBP generated sharper but noisier results (SNR ≤17.20 dB, SSIM ≈ 0.6). MSE values also indicated higher accuracy for SIRT-FBP. However, SIRT-FBP required longer computation time (100 s) compared to FBP (45 s). Both methods showed significant quality degradation at 72 and 36 projections, with blurry and low-contrast images. Acceptable image quality was achieved with a minimum of 108 projections.