Effect of collimator choice on quantitative assessment of cardiac iodine 123 MIBG uptake.
BACKGROUND
Quantitative accuracy in iodine 123 studies may be impaired by septal penetration. We evaluated the effect of collimator choice on estimation of the heart-to-mediastinum (H/M) ratio in cardiac I-123 metaiodobenzylguanidine (MIBG) imaging.


RESULTS
A low-energy high-resolution (LEHR) collimator, special LEHR (SLEHR) collimator, and medium-energy (ME) collimator were used. In experiments in which a phantom of simple geometry was used, the use of the LEHR collimator provided the lowest contrast accuracy, suggesting the effect of septal penetration. Thoracic phantom studies demonstrated contamination of heart and mediastinum counts by lung and liver activities, which was greatest with the LEHR collimator and least with the ME collimator. In 8 patients anterior chest views were acquired successively with the three collimators after I-123 MIBG injection. H/M ratios were significantly higher with the SLEHR collimator than with the LEHR collimator and were still higher with the ME collimator. The difference in H/M ratios between the LEHR and ME collimators showed a high positive correlation with the lung-to-mediastinum ratio.


CONCLUSIONS
Collimator choice substantially influences estimation of the H/M ratios in cardiac I-123 MIBG imaging. The use of an ME collimator provides high quantitative accuracy and may enhance reliability in the evaluation of cardiac sympathetic nerve function.
Inoue
Yusuke
Y
Department of Radiology, Institute of Medical Sciences, University of Tokyo, Japan. inoueys-tky@umin.ac.jp
Suzuki
Akira
A
Shirouzu
Ichiro
I
Machida
Toru
T
Yoshizawa
Yasunori
Y
Akita
Fumihide
F
Ohnishi
Satoshi
S
Yoshikawa
Kohki
K
Ohtomo
Kuni
K
D019797:3-Iodobenzylguanidine / Q000032:analysis / Q000493:pharmacokinetics*; D019544:Equipment Failure Analysis / Q000379:methods*; D005119:Extravasation of Diagnostic and Therapeutic Materials / Q000000981:diagnostic imaging / Q000378:metabolism*; D006352:Heart Ventricles / Q000000981:diagnostic imaging / Q000294:innervation* / Q000378:metabolism*; D007089:Image Enhancement / Q000295:instrumentation / Q000379:methods; D008482:Mediastinum / Q000000981:diagnostic imaging; D019047:Phantoms, Imaging; D011874:Radiometry / Q000295:instrumentation / Q000379:methods; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D015203:Reproducibility of Results; D012542:Scattering, Radiation; D012680:Sensitivity and Specificity; D013564:Sympathetic Nervous System / Q000000981:diagnostic imaging / Q000378:metabolism*; D014055:Tomography, Emission-Computed / Q000295:instrumentation* / Q000379:methods*
D019275:Radiopharmaceuticals; D019797:3-Iodobenzylguanidine