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Bosniak II-III Cystic Renal Masses: Subtraction MR Images for Improvement of Interobserver Agreement with Bosniak Classification, Version 20191Radiology, the First Medical Center of Chinese PLA General Hospital, Beijing, China, 2Radiology, the Fifth Medical Center of Chinese PLA General Hospital, Beijing, China
Synopsis
The purpose of this study was to investigate whether subtraction MR images can improve the interobserver agreement for Bosniak II, IIF and III cystic renal masses (CRMs) with Bosniak classification, version 2019. The results showed that the interobserver agreement was higher with subtraction MR images than without subtraction MR images (weighted k = 0.73 vs 0.60, respectively; P=.011), which may contribute to the popularization and application of Bosniak classification, version 2019.
Purpose
To investigate whether subtraction MR images can improve the interobserver agreement for Bosniak II-III cystic renal masses (CRMs) with Bosniak classification, version 2019.Methods
The CRMs of Bosniak II, IIF and III were selected from all pathologically confirmed CRMs which had been classified in consensus by two experienced genitourinary radiologists with Bosniak classification version 2019. Blinded to clinical and pathologic information, the other two radiologists independently classified Bosniak II, IIF and III CRMs with and without subtraction MR images, respectively, with an interval of 1 month. Ultimately, by using multirater k statistics with Stata/MP 14.0 software, interobserver agreement was evaluated with comparisons between classifications. P＜.05 was considered to indicate a statistically significant difference.Results
A total of 187 patients (mean age ± standard deviation, 50.4 years ± 12.1; 128 male and 59 female patients) with CRMs were included. The weighted k for interobserver agreement among two radiologists with subtraction MR images and without subtraction MR images was 0.73 (95% CI: 0.66, 0.80) and 0.60 (95% CI: 0.53, 0.68), respectively. The interobserver agreement was higher with subtraction MR images than without subtraction MR images (weighted k = 0.73 vs 0.60, respectively; P=.011).Discussion
By eliminating the inherent high signal on the precontrast images, the MR subtraction images may contribute to evaluate whether the lesion has enhancement on the enhanced images, which can improve the interobserver agreement for Bosniak classification.Conclusion
The interobserver agreement for Bosniak II, IIF and III CRMs can be improved using subtraction MR images, which may contribute to the popularization and application of Bosniak classification, version 2019.Acknowledgements
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Figures
Figure 1. The diagram of subtraction MR images. The mass showed heterogeneous hyperintensity on the precontrast images (a) and two thin (≤2mm) enhancing septa on enhanced MR images (b) (corticomedullary phase, nephrographic phase and excretory phase). However, the subtraction MR images (c) (obtained by subtracting a from b) only showed two thin enhancing septa within the lesion.
Figure 2. 57/F, a cyst with hemorrhage located in the right kidney. On Axial view of T2 weighted imaging (a), the mass showed heterogeneous hyperintensity. On the precontrast images (b), the mass exhibited focal slight hyperintensity (pathologically confirmed hemorrhage). On the excretory phase (c), the lesion showed enhancing wall and one septum. On subtraction images from the excretory phase (d), we can clearly see that the mass showed thin (≤2mm) enhancing wall and one thin septum.