Japanese
Title心電図同期心プールシンチグラムにおいて用いられる時間フィルタの周波数特性
Subtitle原著
Authors二村良博*, 古田敏也*, 下方辰幸*, 坂倉一義*, 桜井淳一*, 千田実**
Authors(kana)
Organization*名鉄病院循環器科, **放射線科
Journal核医学
Volume21
Number7
Page845-852
Year/Month1984/7
Article原著
Publisher日本核医学会
Abstract「要旨」心電図同期心プールシンチグラムで用いられる時間軸平滑化フィルタに関して特性の検討を行った. 検討に用いた正弦波は電子計算機で発生させ, 1周期を32フレーム, サンプリング周波数は3,200Hzとした. 対象としたフィルタは(1)X'n=1/4/Xn-1+1/2・Xn+1/4・Xn+1 (2)X'n=1/10・Xn-2+1/5・Xn-1+2/5・Xn+1/5・Xn+1+1/10・Xn+2 (3)f(x)=a0+jΣm=1 am sin(mx+αm)の3種とした. ここでXn, X'nはそれぞれnフレームでの1画素の計数値および重みづけ加算平均した値である. (3)式は周期関数f(x)に関してのj次項までのフーリエ級数である. 正弦波を離散的に収集すると入出力比は3Hzまでほぼ1で4Hz以上は1より小となり, かつ一定値をとらず振動した. (1)は入出力比は2Hzまで1, 遮断周波数はほぼ7Hzであった. (2)は1Hzより減衰が著しかった. (3)はj次項までを合成し, j+1次項以上の成分を除去してノイズを減らす. 入出力比は5Hzまでほぼ1であり遮断性能にすぐれ, 画像のノイズ除去に効果的であった.
Practice臨床医学：一般
KeywordsGated blood pool study, Temporal filters, Fourier transformation, Frequency characteristics.
English
TitleFrequency Characteristics of Temporal Filters Used in ECG Gated Blood Pool Scintigraphy
SubtitleOriginal Articles
AuthorsYoshihiro FUTAMURA*, Toshiya FURUTA*, Tatsuyuki SHIMOKATA*, Kazuyoshi SAKAKURA*, Junichi SAKURAI*, Minoru SENDA**
Authors(kana)
Organization*Department of Cardiology, **Department of Radiology, Meitetsu Hospital
JournalThe Japanese Journal of nuclear medicine
Volume21
Number7
Page845-852
Year/Month1984/7
ArticleOriginal article
PublisherTHE JAPANESE SOCIETY OF NUCLEAR MEDICINE
Abstract[Summary]The purpose of this study is to assess the frequency characteristics of several temporal filters used in ECG gated blood pool scintigraphy and to apply the temporal filters to the image processing. The three following filters were analyzed; (1)X'n=1/4・Xn-1+1/2・Xn+1/4・Xn+1 (2)X'n=1/10・Xn-2+1/5・Xn-1+2/5・Xn+1/5・Xn+1+1/10・Xn+2 (3)f(x)=a0+jΣm=1 am sin(mx+αm) where X'n is the averaged pixel count of the n-th frame and Xn is a pixel count of n-th frame. The last equation is Fourier transformation. Sinusoidal waves were generated in the digital computer in order to assess the frequency characteristics of the filters. The sinusoidal waves were sampled by 3,200 Hz and one frame was created by one hundred sampling points. One cycle was composed of thirty two frames as usually used in the gated blood pool study. At the discrete sampling of the sinusoidal waves, the amplitude ratio of input to output signal was almost flat up to 3 Hz. But the ratio oscillated above 3 Hz. This oscillation was created by the discrete sampling and was regarded as the newly produced noise. By using the first filter, the amplitude ratio of input to output was almost flat up to 2 Hz. But above 3 Hz, the amplitude ratio was less than 1 and the cut-off frequency was 7 Hz. By using the second filter the amplitude ratio was already less than 1 at 1 Hz and the cut-off frequency was 5 Hz. By the third filter, the amplitude ratio was almost flat up to 5 Hz and then gradually decreased above 5 Hz. All filters damped the noises created by the discrete sampling of the sinusoidal waves. The third filter had the excellent frequency characteristics. The reasons were (1) the distortion of the output wave was small because of the flat amplitude ratio, and (2) the noises were eliminated by filtering with an abrupt high frequency cut-off. Therefore, Fourier filtering is useful for the image processing in the gated blood pool study.
PracticeClinical medicine
KeywordsGated blood pool study, Temporal filters, Fourier transformation, Frequency characteristics.

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