SPECT/CT stabilizes the interpretation of somatostatin receptor scintigraphy findings: a retrospective analysis of inter-rater agreement.
OBJECTIVE
Correlating the anatomical information from CT with the functional information from SPECT improves diagnostic accuracy of somatostatin-receptor-scintigraphy (SRS) in patients with neuroendocrine tumors (NET). The aim of the present study was to investigate the impact of dual modality SPECT/CT on the inter-rater agreement in SRS.


METHODS
Twenty-five unselected patients with suspected or histologically proven NET in whom whole body planar imaging and low-dose SPECT/CT had been performed after injection of 200 MBq In-111-octreotide were included retrospectively. Images were interpreted independently by 2 nuclear medicine physicians, an experienced one and an inexperienced one. Both readers first re-evaluated the planar whole-body images alone, then added the SPECT images, and finally the CT-images. Lesions with pathologically increased tracer uptake were categorized according to the following 3-point score: equivocal, probably pathologic, and definitely pathologic. Cohen's linear-weighted kappa coefficient kappa was used to quantify inter-rater agreement.


RESULTS
A total number of 50 lesions were described in 23 of the 25 patients. The two readers showed only moderate agreement in the interpretation of the planar findings (kappa = 0.593). Agreement improved to substantial by adding SPECT (kappa = 0.736) and to very good by adding SPECT/CT (kappa = 0.860). SPECT/CT resulted in up-staging of 18% of the lesions and down-staging of 12% compared to planar + SPECT (experienced reader). In addition, SPECT/CT tended to reduce the frequency of indefinite scores (equivocal, probably pathologic), from 18% in planar + SPECT to 6% (p = 0.065). Change of lesion localization by SPECT/CT tended to contribute to the change of lesion score (p = 0.055).


CONCLUSIONS
The present results suggest that low-dose SPECT/CT stabilizes report quality in SRS by improving inter-rater agreement.
Apostolova
Ivayla
I
Department of Nuclear Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany. swissiva@yahoo.com
Riethdorf
Swantje
S
Buchert
Ralph
R
Derlin
Thorsten
T
Brenner
Winfried
W
Mester
Janos
J
Klutmann
Susanne
S
D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D017481:Receptors, Somatostatin / Q000378:metabolism*; D012189:Retrospective Studies; D015899:Tomography, Emission-Computed, Single-Photon; D014057:Tomography, X-Ray Computed; D051598:Whole Body Imaging
D017481:Receptors, Somatostatin