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Effectiveness of flexible noise control image processing for digital portal images using computed radiography

¹ Department of Radiology, Kurashiki Central Hospital, 1-1-1 Miwa, Kurashiki, Okayama 710-8602 and ² Department of Medical Physics and Engineering, Division of Medical Technology and Science, Course of Health Science, Graduate School of Medicine, Osaka University, 1-7 Yamadaoka, Suita, Osaka 565-0871, Japan

View larger version (83K): [in a new window]   Figure 1. Computed radiography (CR) portal images of the head. (a) Examples of an un-sharp mask image. Black-framed artefacts were observed around the irradiation field (black arrows) and around the scale (black arrows on the broken line). The skin boundary around the head was unclear (white arrows). (b) Examples of an multiobjective frequency processing (MFP) image. Black-framed artefacts were reduced, and the skin boundary became clear.

View larger version (62K): [in a new window]   Figure 2. Outlines of multiobjective frequency processing (MFP). The original image and several unsharp mask images were prepared (step a). Several band-pass filter images were produced (step b) by subtraction processing of unsharp mask images with a similar frequency band. A combined image was produced (step c) by multiplying each band-pass filter image by each enhancement coefficient. An MFP image was obtained (step d) by adding the original image to the combined image.

View larger version (74K): [in a new window]   Figure 3. Outlines of flexible noise control processing (FNC). Several band-pass filter images were produced (step b) using several unsharp mask images, as in multiobjective frequency processing (MFP). Subsequently, images with extracted noise components alone were produced (step c), and an image with combined noise components was produced (step d). An FNC-processed image was obtained (step e) by subtracting the image with combined noise components from the original image. Routinely, the FNC-processed image was regarded as the original image, and was subjected to MFP.

View larger version (92K): [in a new window]   Figure 4. Sample images of multiobjective frequency processing (MFP) and flexible noise control (FNC). The upper panels (a, b) show the head, the middle panels (c, d) show the chest, and the lower panels. (e, f) show the lateral pelvis. The left panels (a, c, e) are MFP images, and the right panels (b, d, f) are FNC images.

View larger version (96K): [in a new window]   Figure 5. Parts of the multiobjective frequency processing (MFP) and flexible noise control (FNC) images after magnification. The upper panels (a, b) show the pituitary fossa, the middle panels (c, d) show the lung apex, and the lower panels (e, f) show the pubic symphysis. The left panels (a, c, e) are MFP images, and the right panels (b, d, f) are FNC images.