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KMID : 1143620130170020053
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Korean Journal of Nuclear Medicine Technology
2013 Volume.17 No. 2 p.53 ~ p.58
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The Evaluation of Image Correction Methods for SPECT/CT in Various Radioisotopes with Different Energy Levels
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Shin Byung-Ho
Kim Seung-Jeong
Yoon Seok-Hwan
Kim Tae-Yeob
Lim Jung-Jin
Woo Jae-Ryong
Oh So-Won
Kim Yu-Kyeong
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Abstract
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Purpose: To optimize correction method for SPECT/CT, image quality consisting of resolution and contrast was evaluated using three radioisotopes (99mTc, 201Tl and 131I) and three different correction methods; attenuation correction (AC), scatter correction (SC) and both attenuation and scatter correction (ACSC).
Materials and Methods: Images were acquired with a SPECT/CT scanner and a conventional CT protocol with an OESM
reconstruction algorithm (2 iterations and 10 subsets). For resolution measurement, fixed radioactivity (2.22 kBq) was infused into a spatial resolution phantom and full width at half maximum (FWHM) was measured using a vendor-provided software. For contrast evaluation, radioactive source with a ratio of 1:8 to background was filled in a Flanged Jaszczak phantom and percent contrast (%) were calculated. All the parameters for image quality were compared with non-correction (NC) method.
Results: As compared with NC, image resolution of all three isotopes were significantly improved by AC and ACSC, not by SC. In particular, ACSC showed better resolution than AC alone for 99mTc and 201Tl. Image contrast of all three radioisotopes in a sphere with the largest diameter were enhanced by all correction methods. ACSC showed the highest contrast in all three radioisotopes, which was the most accurate in 99mTc (85.9%).
Conclusion: Image quality of SPECT/CT was improved in all the radioisotopes by CT-based attenuation correction methods, except SC alone. SC failed to improve resolution in any radioisotopes, but it was effective in contrast enhancement. ACSC would be the best correction method as it improved resolution in radioisotopes with low energy levels and contrast in radioisotope with low energy levels. However, in radioisotope with high energy level, AC would be better than ACSC for resolution improvement.
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KEYWORD
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Attenuation correction, Scatter correction, Percent contrast, FWHM, OSEM
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