Impact of a predefined mediastinal ROI on inter-observer variability of planar ¹²³I-MIBG heart-to-mediastinum ratio.
OBJECTIVE
Purpose of this study was to assess the impact of mediastinal region of interest (ROI) definition on intra- and inter-observer variability in relation to collimator type.


METHODS
Thirty-five subjects with CHF (80% men, mean age 66 ± 9 years, NYHA 2.4 ± 0.5, LVEF 29 ± 8.4%) were enrolled. 15 minutes and 4 hours post-injection (p.i.) of (123)I-MIBG, planar images were sequentially acquired with low energy high energy (LEHR) and medium energy (ME) collimators. In the first analysis, observer-defined mediastinal ROI was used. In the second analysis, a predefined mediastinal ROI was used. Intra- and inter-observer variability of late H/M was assessed using Lin's concordance coefficient (LCC).


RESULTS
There was substantial agreement between all three observers using predefined mediastinum ROI. LCCs for LEHR were 0.98, 0.96, and 0.95, for ME 0.98, 0.97, and 0.97. However, observer-defined mediastinal ROI resulted in poor-moderate agreement. LCCs for LEHR were 0.82, 0.94, and 0.70, for ME 0.77, 0.91, and 0.80. Intra-observer analysis using predefined mediastinal ROI showed substantial agreement. LCC was 0.97 for LEHR and 0.96 for ME.


CONCLUSIONS
Predefined mediastinal ROI results in low intra- and inter-observer variability of late H/M and is, therefore, to be preferred over observer-defined mediastinal ROI. Intra- and inter-observer variability of late H/M is not influenced by collimator choice.
Department of Nuclear Medicine, Academic Medical Center, University of Amsterdam, P.O. Box 22700, 1100 DE, Amsterdam, The Netherlands, d.o.verschure@amc.uva.nl.
Derk O
DO
Verschure
Vivian
V
Bongers
Petronella J
PJ
Hagen
G Aernout
GA
Somsen
Berthe L F
BL
van Eck-Smit
Hein J
HJ
Verberne
D019797:3-Iodobenzylguanidine / Q000493:pharmacokinetics*; D000368:Aged; D005260:Female; D006321:Heart / Q000000981:diagnostic imaging; D006333:Heart Failure / Q000000981:diagnostic imaging* / Q000378:metabolism*; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008297:Male; D008482:Mediastinum / Q000000981:diagnostic imaging*; D009206:Myocardium / Q000378:metabolism*; D015588:Observer Variation; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
D019275:Radiopharmaceuticals; D019797:3-Iodobenzylguanidine