Application of three-dimensional SPACE magnetic resonance imaging in accurate measurement of implant volume in breast surgery

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Objective The study is to assess the accuracy and reliability of three-dimensional simulated magnetic resonance imaging with silicone-excitation SPACE (sampling perfection with application optimized contrast using different flip angle evolutions) sequence for estimating implant volume. Methods (1) MRI examinations of 10 silicone implants (Wuhan Tongji Hospital from October 2018 to December 2018) were performed with T2, H2O-excitation SPACE sequence (T2-spc-H2O) and silicone-excitation SPACE sequence (T2-spc-Silicone) to find the most accurate method to estimate implant volume by ITK-SNAP. The effect of implant deformation and slice thickness of T2-spc-Silicone on volume measurement were investigated. (2) 13 normal patients and 6 patients with implant complications (Wuhan Tongji Hospital from March 2017 to May 2019) were enrolled for testing the accuracy and reliability of T2-spc-Silicone for volume measurement in vivo. The data were analyzed using Prism 8.0 software. The paired student t-test was used to compare the difference of two groups. One-way ANOVA was used to compare the difference of multiple groups. P<0.05 was considered statistically significant. Results The absolute volume differences of T2, T2-spc-H2O, T2-spc-Silicone were (42.19±2.31) ml, (23.27±1.55) ml and (6.28±1.22) ml. The absolute volume differences of T2-spc-Silicone group was significantly less than T2-spc-H2O and T2 group in vitro(F=195.3, P<0.001). No significant difference(F=1.36, P=0.22)was shown between the normality group and the deformation group for estimating the volume of implants with the slice thickness of SPACE increased from 0.5 mm×0.5 mm×0.5 mm to 5.0 mm×5.0 mm×5.0 mm. Besides, the slices thickness of SPACE from 0.5 mm×0.5 mm×0.5 mm to 5.0 mm×5.0 mm×5.0 mm did not significantly affect the accuracy of volume measurement of the implants in deformation state(F=1.22, P=0.29). The measurement error of SPACE was (8.82±0.99) ml in normal patients. Moreover, there was no significant difference between measured volume[(226.4±12.76)ml] and actual volume of implants[(225.9±11.94) ml](t=0.31, P=0.76)in patients with implant complications. The result showed excellent intraobserver reliability (ICC=0.997) and internal consistency ranged from 0.986 to 0.997 (P<0.001). Conclusions The method to measure implant volume by silicone-excitation SPACE sequence had desirable accuracy and reliability. The deformation of the implant and the slice thickness of the SPACE sequence did not exhibit a significant effect on the accuracy of volume measurement. Key words: Silicone gel; Breast implant; Magnetic resonance imaging; Sampling perfection with application optimized contrast using different flip angle evolutions; Slice thickness; Deformation; Volume measurement