Kunio Hamada

Relationship between image quality and changes in spatial resolution for the gamma camera.

空間分解能の劣化と視覚的な画質との関係を定量的に検討した。コリメータと検体を密着した時のFWHMを基準にして, 離した時のFWHMとの差を△FWHMとすると, 画質上の変化を認識できる割合 (ρ) は, △FWHMが大きくなるに従いsigmoid curveを描いて大となった。Dendyらの方法およびファジィ理論を適用して, 画質の違いを充分認識できる最小△FWHMを検討すると, △FWHM=0.5mmとなった。この値はコリメータから約2cm離れた時の値に相当した。

(p, 5n) 反応によって製造した123Iを用いたSPECTに関する基礎的検討

The effects of higher-energy photon from 123I (p, 5n) on the SPECT image quality were evaluated. The quality was evaluated by image contrast and %rms. Image contrast had similar tendency to planar and SPECT FWHM value. %rms was affected by septal penetration. Using 140 keV high resolution collimator (140 keV HR), image contrast was superior to that for 300 keV medium energy collimator (300 keV ME), but septal penetration rate (SPR) was 18% and %rms was 10.5. When quantitation is required, the collimator with less SPR than 18% is recommended for SPECT imaging. Using 300 keV ME, SPR was 0.05%, but spatial resolution and image contrast were inferior to that for 140 keV HR.