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객체지향과 멀티미디어 기술을 이용한 전산화 신경 심리 검사 시스템
안창범,김휴정,신진교,박준모,이성훈 대한의용생체공학회 1999 의공학회지 Vol.20 No.5
임상적인 응용을 목적으로 하는 전산화 신경 심리 검사 시스템을 개발하였다. 개발된 시스템은 국소적 뇌기능 장애 진단에 뛰어난 14개의 검사록 구성되어 있으며 집중력·언어능력, 공간 및 도형 인지 능력, 기억력, 운동 집중 능력 등을 진단하게 된다. 개발된 시스템은 멀티미디어 객체지향개념에 의거하여 설계 구현되었고, 마이크로소프트 Windows 에 기반을 둔 그래픽 인터페이스를 채용하여 운용이 용이하도록 하였다. 또한 마우스와 터치스크린을 이용하여 피검사자로부터 입력을 손쉽게 받아들 일수 있도록 하였으며, 색체 단어검사, 범주화검사, 언어기억검사들을 한글화하여 검사의 효용성을 향상시켰다. 개발된 시스템을 정상인 그룹과 환자에 적용한 결과 뇌기능 장애 진단에 유용하게 사용될 수 있음을 확인할수 있었다.
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정수기반 웨이블릿 변환을 이용한 통합된 유 / 무손실 의학영상압축
안창범(Ahn C . B .),송영철(Song Y . C .),고형화(Koh H . H .),안용현(Ahn Y . H .) 한국화상학회 1998 한국화상학회지 Vol.4 No.1
A unified lossy to lossless compression algorithm is developed using integer-based reversible wavelet transforms. The proposed algorithm is based on a pre-quantization, integer-based wavelet transform, and a bit plane coding of the wavelet bands with QM coder. An improved pre-quantization scheme is proposed with which number of gray levels after pre-quantization is the same as that in the original image. An optimal encoding order for the wavelet bands in both spatial frequency domain and bit planes are devised. Prom simulation, reconstructed image by the proposed algorithm shows higher peak signal-to-noise ratio (PSNR) compared to those obtained by a float-point-based wavelet transform (Daubechies) and the JPEG. Peak errors in the reconstructed images by the integer-based wavelet transform are also much lower than those obtained by the JPBG and the float-point-based wavelet coding. In near lossless compression, lossless encoding of the wavelet coefficients of the pre-quantized image shows higher PSNR than those with bit rate control by the bit plane-band ordering of the wavelet coefficients without pre-quantization. Using pre-quantization, peak error can be easily controlled, which may be an important feature in medical image compression.
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자기공명영상의 신호대잡음비 향상을 위한 다중 템플릿 적응 필터링
안창범(Ahn C . B .),송영철(Song Y . C .),박대준(Park D . J .) 한국화상학회 1997 한국화상학회지 Vol.3 No.1
In this paper, a local shape adaptive template filtering is proposed for an enhancement of signal-to-noise ratio in magnetic resonance imaging with little degradation of resolution. Uulike conventional filtering where template size and shape are fixed, multiple templates are defined and optimal template among the multiple templates is selected and applied in pixel-by-pixel basis. By the proposed scheme, edge blurring is minimized by selecting mostly matched template, yet SNR enhancement by the filtering is fully utilized. Compared to existing two-dimensional linear least square error Inter or direction-adaptive recursive filter, the proposed shape-adaptive filter with multiple templates provides higher SNR and sharper edges for both natural images and artificial resolution phantom images.
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향상된 정수 기반 웨이블릿 변환을 이용한 무손실에 가까운 영상 압축
안창범(Ahn C . B .),송영철(Song Y . C .) 한국화상학회 1997 한국화상학회지 Vol.3 No.1
An enhanced version of integer-based wavelet transform(TS Transform) coding is proposed for near lossless image compression. Due to flexibility in representing nonstationary image signals in time and frequency domains and ability in adapting to human visual characteristics, wavelet transform has unique advantages over other transforms currently used in image compression. In the Integer-based wavelet transform compression, original image is decomposed into multi-scalar bands. For the lowest band, a predictor is designed and error signal is entropy coded. For higher scalar bands, runlength coding for zero runs is employed with Huffman coding. In order to perform near lossless compression, pre-quantization of the original image is applied and the quantized image is losslessly encoded. To overcome visual degradation resulting from pre-quantization, a new pre-quantization scheme using multiple quantization tables is proposed. From simulation (512×512 size, 256 graylevel image) reconstructed images by the proposed algorithm show higher peak signal-to-noise ratio (PSNR) compared to those obtained by a float-point-based wavelet transform and the JPEG. Peak error in the reconstructed images by the integer-based wavelet transform is also much lower than those obtained by the JPEG and the float-point-based wavelet transform.
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JPEG 점진적 확장 코딩을 이용한 핵자기 공명 영상 압축
안창범(Ahn C . B .),윤기병(K . B . Yoon) 한국화상학회 1995 한국화상학회지 Vol.1 No.1
The JPEG (Joint Photographic Experts Group) standard which was accepted as a compression method in the Digital Imaging and Communications in Medicine (DICOM) standard recently is tested with a set of magnetic resonance (MR) images with 8 bits/pixel and 12 bits/pixel precisions. Due to the lossy character of the DCT-based JPEG compression, its application to medical image compression has been limited. for head sections of MR images, compression ratios of more than 10 are obtained without noticeable image degradation. The performance of the JPEG coding is compared to existing full-frame bit-allocation technique proposed for the radiological image compression. From comparison, the JPEG standard achieves higher compression with high signal-to-noise ratio. Reconstructed images by the JPEC standard also show better subjective image quality with less Gibb`s artifact. The progressive JPEG coding may be useful in tele-radiology when data is transmitted through slow public communication channel.
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