title: Method for reducing noise in X-ray images by averaging pixels based on the normalized difference with the relevant pixel.
abstract: A real-time digital filter for noise reduction in X-ray images is proposed. The filter is based on averaging of only similar pixels (pixels that differ only little) rather than neighboring pixels, which are averaged in conventional linear low-pass filters. The effectiveness of the filter was evaluated by computer simulation, where original images that were acquired by X-ray exposure were processed in accordance with the filter algorithm. The resulting images were evaluated in terms of the pre-sampled modulation transfer function (MTF), the noise power spectrum (NPS), and the lag. Comparison of the filtered and original images revealed that the NPS was reduced for the full range of spatial frequencies in the filtered image, resulting in a reduction of total noise power to about 1/9 the level in the original image with no degradation in the MTF or lag. The usefulness of the filter was demonstrated in fluoroscopic, digital subtraction angiography (DSA) and mammographic phantom studies. The filter was found to have the potential to reduce the patient dose by reducing the noise in dynamic as well as static X-ray images.
authors.affiliation: Toshiba Medical Systems Corporation, Otawara, Tochigi, Japan. masayuki.nishiki@toshiba.co.jp
authors.forename: Masayuki
authors.initials: M
authors.lastname: Nishiki
authors.forename: Kunio
authors.initials: K
authors.lastname: Shiraishi
authors.forename: Takuya
authors.initials: T
authors.lastname: Sakaguchi
authors.forename: Kyojiro
authors.initials: K
authors.lastname: Nambu
mesh_terms: D000465:Algorithms; D015901:Angiography, Digital Subtraction / Q000295:instrumentation / Q000379:methods; D003198:Computer Simulation; D005374:Filtration / Q000295:instrumentation* / Q000379:methods; D005471:Fluoroscopy / Q000295:instrumentation / Q000379:methods; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000295:instrumentation* / Q000379:methods; D008327:Mammography / Q000295:instrumentation / Q000379:methods; D019047:Phantoms, Imaging; D011835:Radiation Protection / Q000295:instrumentation* / Q000379:methods; D014057:Tomography, X-Ray Computed / Q000295:instrumentation* / Q000379:methods
references.citation: Br J Radiol. 2005 Jun;78(930):519-27
references.pmid: 15900057
references.citation: Med Phys. 2000 Aug;27(8):1841-54
references.pmid: 10984231
references.citation: Radiol Phys Technol. 2008 Jan;1(1):62-74
references.pmid: 20821165
references.citation: Med Phys. 1995 Oct;22(10):1595-604
references.pmid: 8551983
references.citation: Invest Radiol. 2006 Jan;41(1):1-7
references.pmid: 16355033
references.citation: Radiology. 1982 Sep;144(4):789-92
references.pmid: 7111727
references.citation: Med Phys. 2000 Sep;27(9):2048-59
references.pmid: 11011732
references.citation: Med Phys. 1998 Jan;25(1):102-13
references.pmid: 9472832
references.citation: Nihon Hoshasen Gijutsu Gakkai Zasshi. 2003 May;59(5):621-4
references.pmid: 12881691
references.citation: Med Phys. 2000 Aug;27(8):1855-64
references.pmid: 10984232
references.citation: Nihon Hoshasen Gijutsu Gakkai Zasshi. 2004 Dec;60(12):1688-93
references.pmid: 15614220