Scatter correction by two-window method standardizes cardiac I-123 MIBG uptake in various gamma camera systems.
Heart to mediastinum count ratio (H/M) has been commonly utilized as an indicator of myocardial I-123 MIBG uptake. However, normal ranges of H/M were markedly different among various gamma camera systems. The purpose of this study was to clarify whether scatter correction by two-window method standardizes H/M among various gamma camera systems.


METHODS
Scatter uncorrected and corrected MIBG imaging was acquired in phantom and human studies in combination with low energy high-resolution collimator (LEHR) and medium energy collimator (MEC). For scatter correction, energy window width of 159 keV +/- 10% was applied to main window imaging and 193 keV +/- 9.5% was applied to upper window imaging for scatter correction.


RESULTS
In phantom study, a significant difference was observed in uncorrected H/M among three gamma camera systems using LEHR or MEC (2.09 +/- 0.06 vs. 2.58 +/- 0.03 in GCA7200 camera, 2.00 +/- 0.07 vs. 2.42 +/- 0.06 in DS7 camera and 2.16 +/- 0.04 vs. 2.67 +/- 0.07 in Vertex plus camera). However, there was no significant difference in corrected H/M among the three gamma camera systems, either with LEHR or MEC (2.70 +/- 0.07 vs. 2.69 +/- 0.07 in GCA7200 camera, 2.66 +/- 0.08 vs. 2.61 +/- 0.05 in DS7 camera and 2.66 +/- 0.05 vs. 2.61 +/- 0.05 in Vertex plus camera). In human study, uncorrected H/M in DS7 camera with LEHC was significantly lower than that in GCA7200 camera with MEC (1.60 +/- 0.37 vs. 1.85 +/- 0.54, N = 14). In contrast, the difference was insignificant in corrected H/M (2.12 +/- 0.59 vs. 2.16 +/- 0.68). There was a very excellent correlation in corrected H/M between DS7 and GCA7200 cameras (r = 0.991, p < 0.001).


CONCLUSIONS
This study demonstrated that scatter correction by the two-window method standardizes the H/M in MIBG scintigraphy either with LEHR or MEC. Scatter corrected H/M can be applied to measure a standardized parameter of MIBG uptake in human clinical studies using various gamma camera systems.
Kobayashi
Hideki
H
Department of Radiology, Tokyo Women's Medical University, Japan. mkobayas@hij.twmu.ac.jp
Momose
Mitsuru
M
Kanaya
Shinichi
S
Kondo
Chisato
C
Kusakabe
Kiyoko
K
Mitsuhashi
Norio
N
D019797:3-Iodobenzylguanidine / Q000378:metabolism* / Q000493:pharmacokinetics* / Q000592:standards; D016477:Artifacts; D002138:Calibration; D004868:Equipment Failure; D005260:Female; D015902:Gamma Cameras / Q000592:standards*; D006321:Heart / Q000000981:diagnostic imaging; D006331:Heart Diseases / Q000000981:diagnostic imaging* / Q000378:metabolism*; D006801:Humans; D007089:Image Enhancement / Q000295:instrumentation / Q000379:methods* / Q000592:standards*; D008297:Male; D008875:Middle Aged; D009206:Myocardium / Q000378:metabolism; D019047:Phantoms, Imaging; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D015203:Reproducibility of Results; D012542:Scattering, Radiation; D012680:Sensitivity and Specificity
D019275:Radiopharmaceuticals; D019797:3-Iodobenzylguanidine