A study to improve the image quality in low-dose computed tomography (SPECT) using filtration

Area of Science:

• Medical Imaging
• Radiological Physics

Background:

• Computed tomography (CT) X-ray beams contain a spectrum of photon energies.
• Low-energy photons are absorbed preferentially, shifting the beam spectrum and causing artifacts (beam-hardening).
• Accurate Hounsfield units are crucial for attenuation coefficient calculations.

Purpose of the Study:

• To investigate the impact of additional copper filters on CT image quality.
• To minimize beam-hardening artifacts in CT imaging.
• To evaluate the quantitative effect of varying filter thicknesses on CT images.

Main Methods:

• Dual-head SPECT with low-dose CT (120/140 kV, 2.5 mA) was used.
• CT QA Phantom with six density pins evaluated image quality.
• Copper filters (1-5 mm) were sequentially added to the X-ray beam.
• Images were analyzed for visibility, spatial resolution, and signal-to-noise ratio (SNR).

Main Results:

• Image quality improved with filter thicknesses up to 3 mm, showing sharper images with fewer artifacts.
• Spatial resolution improved from 1.29 mm (no filter) to 0.54 mm (3 mm filter).
• Signal-to-noise ratio (SNR) increased by 15.7% with a 3-mm filter (1.72 to 1.99).

Conclusions:

• A 3-mm copper filter is optimal for artifact reduction in CT imaging.
• This filtration enhances image quality without significant photon flux reduction.
• Improved image accuracy is expected to enhance SPECT image contrast and visualization.