Interobserver reproducibility of signal intensity ratio on magnetic resonance angiography for hemodynamic impact of intracranial atherosclerosis.
BACKGROUND
Changes of signal intensities (SIs) across intracranial atherosclerosis (ICAS) on magnetic resonance angiography (MRA) may reflect hemodynamic impact of the lesion. We evaluated the interobserver reproducibility of an index termed signal intensity ratio (SIR), developed in a previous study to represent the changes of SIs across ICAS on MRA.


METHODS
Symptomatic ICAS on MRA were retrospectively recruited. Two observers respectively evaluated the images and calculated the SIR as follows, blinded to each other's readings: SIR=(mean poststenotic SI-mean background SI)/(mean prestenotic SI-mean background SI). Statistical analyses were performed to evaluate the interobserver reproducibility of this index.


RESULTS
A total of 102 symptomatic ICASs were enrolled, with 36 (35.3%) lesions of 50%-69% MRA stenoses and others being 70%-99% stenoses or flow void on MRA. Overall, mean SIRs were not significantly different between the 2 observers (.92±.17 versus .93±.17; mean difference -.006±.09; P=.496 for paired t test). Pearson correlation coefficients were >.80 for all analyses, indicating strong linear correlations between SIRs by the 2 observers. Bland-Altman analysis for SIRs of all cases showed no systematic bias between the 2 observers. For different cut-points ranging from .75 to 1.00, the kappa statistics were mostly greater than .6 and interobserver agreements were all greater than 80%, implying substantial agreement between observers.


CONCLUSIONS
SIR was demonstrated to be highly reproducible between observers in the present study. Future studies are warranted to further explore the role of this index in comprehensive evaluation and risk stratification of symptomatic ICAS.
Department of Medicine and Therapeutics, The Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, Hong Kong SAR, China.
Xinyi
X
Leng
Hing Lung
HL
Ip
Yannie
Y
Soo
Thomas
T
Leung
Liping
L
Liu
Edward
E
Feldmann
Ka Sing
KS
Wong
David S
DS
Liebeskind
D001488:Basilar Artery / Q000503:physiopathology*; D002343:Carotid Artery, Internal / Q000503:physiopathology*; D002560:Cerebrovascular Circulation; D002681:China; D003251:Constriction, Pathologic; D006439:Hemodynamics; D006801:Humans; D002537:Intracranial Arteriosclerosis / Q000175:diagnosis* / Q000503:physiopathology; D018810:Magnetic Resonance Angiography; D020768:Middle Cerebral Artery / Q000503:physiopathology*; D015588:Observer Variation; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D012189:Retrospective Studies
Interobserver reproducibility; hemodynamics; intracranial atherosclerosis; magnetic resonance angiography; signal intensity