Abstract
The x-ray computed tomography (CT) images with low dose are noisy and may contain photon starvation artifacts. The artifacts are location and direction dependent. Therefore, the common shift-invariant denoising filters do not work well. The state-of-the-art methods to process the low-dose CT images are image reconstruction based; they require the raw projection data. In many situations, the raw CT projections are not accessible. This paper suggests a method to denoise the low-dose CT image using the pseudo projections generated by the application of a forward projector on the low-dose CT image. The feasibility of the proposed method is demonstrated by real clinical data.
Highlights
The main drive force of using low-dose x-ray computed tomography (CT) is to reduce the patient radiation exposure [1,2,3]
The numerical results of the Sum Square Difference (SSD) values are listed in Tables 1, 2, and 3, respectively, for slices #5, #30, and #50
This phenomenon could be caused by the lowpass filtering effect of the forward projecting procedure, which reduces some noise
Summary
The main drive force of using low-dose x-ray computed tomography (CT) is to reduce the patient radiation exposure [1,2,3]. When the x-ray dose is extremely low, the photon starvation effect can cause severe streaking artifacts in the CT reconstruction [5, 6]. The reference [7] states that “Photon starvation is one source of streak artifact which may occur in CT. It is seen in high attenuation areas, behind metal implants.”. It is seen in high attenuation areas, behind metal implants.” In [8] we read: “When too few photons reach detector elements, strong streaks appear through paths of high X-ray attenuation and an image becomes completely useless.”
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