Assessment of global cardiac I-123 MIBG uptake and washout using volumetric quantification of SPECT acquisitions.
BACKGROUND
Assessment of cardiac innervation using single-photon emission computer tomography (SPECT) is less established than planar imaging, but may be more suitable for quantification. Therefore, a volumetric quantification of I-123 MIBG SPECT acquisitions was performed. Reproducibility, the effects of extra cardiac I-123 MIBG uptake and the relation with conventional planar indices were evaluated.


METHODS
54 patients referred for planar and SPECT I-123 MIBG acquisitions were included. Ellipsoidal or box-shaped volumes of interest were placed on the left ventricle, cardiac lumen, mediastinum, lung and liver. SPECT segmentation was performed twice in all patients. Indices were determined based on the heart-to-mediastinum (HM), myocardial wall-to-mediastinum and myocardial wall-to-lumen regions. HM ratios and washout rates were also determined based on anterior planar images.


RESULTS
Cardiac count densities were highly reproducible (CV 1.5-5.4, ICC 0.96-0.99) and inter-rater variability was low (CV 1.8-6.8, ICC 0.94-0.99). Mediastinal uptake was an important explanatory variable of uptake in the entire heart (early R(2) = 0.36; delayed R(2) =0.43) and myocardial wall (early R(2) = 0.28; delayed R(2) = 0.37). Lung washout was an explanatory variable of organ washout of the heart (heart R(2) = 0.38; myocardial wall R(2) = 0.33). In general, SPECT indices showed moderate-to-good correlations with the planar uptake (PCC 0.497-0.851).


CONCLUSIONS
By applying a volumetric segmentation method we were able to segment the heart in all patients. SPECT I-123 MIBG quantification was found to be highly reproducible and had a moderate to good correlation with the planar indices.
Department of Nuclear Medicine, Leiden University Medical Center, PO Box 9600, 2300 RC Leiden, The Netherlands. l.vd.veen@nki.nl
Berlinda J
BJ
van der Veen
Imad
I
Al Younis
Albert
A
de Roos
Marcel P M
MP
Stokkel
D019797:3-Iodobenzylguanidine / Q000493:pharmacokinetics*; D000367:Age Factors; D000368:Aged; D005260:Female; D006321:Heart / Q000000981:diagnostic imaging*; D006352:Heart Ventricles / Q000473:pathology; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D007457:Iodine Radioisotopes / Q000494:pharmacology; D008297:Male; D008482:Mediastinum / Q000473:pathology; D008875:Middle Aged; D009206:Myocardium / Q000473:pathology; D015588:Observer Variation; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D015203:Reproducibility of Results; D014018:Tissue Distribution; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods*
D007457:Iodine Radioisotopes; D019275:Radiopharmaceuticals; D019797:3-Iodobenzylguanidine