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PURPOSE: The pvrpose of this study was to evaluate the accuracy of radioactivity quantitation in Tc-99m SPECT by using combined scatter and attenuation correction. MATERIALS AND METHODS: A cylindrical phantom which simulates tumors (T) and normal tissue (B) was filled with varying activity ratios of Tc-99m. We acquired emission scans of the phantom using a three-headed SPECT system (Trionix, Inc.) witb two energy windows (photopeak window: 126 154 keV and scatter window: 101 123 keV). We performed the scatter correction with dual-energy window subtraction method (k=0.4) and Chang attenuation correction. Three sets of SPECT images were reconstructed using combined scatter and attenuation correction (SC+AC', attenuation correction (AC) and without any correction (NONE). We compared T/B ratio, irnage contrast [(T-B)/(T+B)) and absolute radioactivity with true values. RESULTS: SC+AC images had the highest mean values of T/B ratios. Image contrast was 0.92 in SC+AC, which was close to the true value of 1, and higher than AC (0.77) or NONE (0.80). Errors of true activity by SPECT images ranged from 1 to 11% for SC+AC, 22-47% for AC, and 2 16% for NONE in a phantom which was located 2.4cm from the phantom surface. In a phantom located 10,0cm from the surface, SC+AC underestimated by ?4%, NON.E 40%. However, AC overestimated by 10%. CONCLUSION: We conclude that accurate SPECT activity quantitation of Tc-99m distribution can be achieved by dual window scatter correc.tion combined with attenuation correction.
Radioactivity ; Tomography, Emission-Computed, Single-Photon*

9.Diagnosis of hepatic hemangioma with 99mTc-labeled red cells and single photon emission computed tomography (SPECT).

Dae Hyuk MOON ; Shee Man CHO ; Myung Hae LEE ; Suck Kyun YANG ; Young Hwa CHUNG ; Yung Sang LEE ; Sung Hae SHIN ; Kee Suk HONG

Korean Journal of Nuclear Medicine 1991;25(1):68-75

10.Maligmant external otitis demonstrated by bone SPECT(99mTc-MDP) and67Ga SPECT.

Jin Sook RYU ; Dae Hyuk MOON ; Myung Hae LEE

Korean Journal of Nuclear Medicine 1992;26(1):168-169

1.Myocardial SPECT.

2.Reproducibility of non-invasive measurement for left ventricular contractility using gated myocardial SPECT.

3.Cerebral Postischemic Hyperperfusion in PET and SPECT.

4.Assessment of Gastric Accommodation by SPECT.

5.Malignant trasformation of hepatic dysplastic nodule revealed by Tc (99m)Liver Spect.

6.Combined 201T1 and 99mTc-PYP myocardial SPECT in acute myocardialinfarction.

7.Early stress echocardiogram and 99Tc-MIBI heart spect findings after coronary atrery revascularization.

8.Improved Activity Estimation using Combined Scatter and Attenuation Correction in SPECT.

9.Diagnosis of hepatic hemangioma with 99mTc-labeled red cells and single photon emission computed tomography (SPECT).

10.Maligmant external otitis demonstrated by bone SPECT(99mTc-MDP) and67Ga SPECT.

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