基于核磁共振CPMG方法比较3D打印体模材料的吸水性

Comparison of water absorbability of 3D printed phantom materials based on MR CPMG method

核磁共振体模是用于磁共振成像(MRI)测试的重要组件,由MRI中表现为无信号的聚甲基丙烯酸甲酯(PMMA)材料外壳内装PMMA材料制作的测试组件以及体模测试液(纯水、硫酸铜和氯化钠)组成。近年来,越来越多的磁共振体模通过3D打印的方式制作,来满足体模个性化设计和快速成型需求,然而对于3D打印制作的体模是否能像PMMA材料那样有效防水这一问题尚无相关研究,本研究基于核磁共振PQ001核磁共振分析仪,利用CPMG(Carr Purcell Meiboom Gill)硬脉冲序列测试6种材料(包括3D打印材料:ABS树脂、SLA光敏树脂和DLP光敏树脂;常用体模制备材料:硅胶、水凝胶和PMMA)饱水前后的T_2弛豫时间,以此比较6种不同性质材料的孔隙大小。同时结合6种材料饱水前后T_2信号量的变化率,综合比较材料的吸水情况。结果表明PMMA和光敏树脂、ABS等3D打印材料的孔隙大小明显低于常规体模材料硅胶和水凝胶,而在吸水性上3D打印材料ABS和SLA光敏树脂接近PMMA材料。综合孔隙大小和吸水性两方面比较,ABS和SLA光敏树脂材料在防水防渗透方面与常规磁共振体模外壳材料PMMA相近,可以有效替代PMMA材料用于磁共振体模外壳和插件。

Magnetic resonance（MR） phantom, an important component for MR imaging test, was composed of polymethylmethacrylate（PMMA） material shell, PMMA material test components and test solution（pure water, copper sulfate and sodium chloride）. In recent years, more and more MR phantoms were produced by three-dimensional（3 D） printing technique in order to meet the requirements for phantom personalized design and rapid prototyping. However, there was no relevant research on whether 3 D printed phantom could be effectively waterproof like PMMA materials. Six kinds of materials were investigated in this study, including 3 kinds of 3 D printed materials（ABS resin, SLA photosensitive resin and DLP photosensitive resin） and3 kinds of commonly used phantom materials（silica gel, hydrogels and PMMA）. Based on PQ001 MR analyzer, we used CPMG（Carr Purcell Meiboom Gill） hard pulse sequence to test the T_2 relaxation time of 6 kinds of materials before and after saturation for comparing their pore sizes. Meanwhile, the water absorbability of different materials was comprehensively compared with the consideration of T_2 relaxation time and the change rate of T_2 semaphore before and after saturation. The results revealed that the pore size of PMMA, photosensitive resin, ABS and other 3 D printed materials were significantly lower than that of silica and hydrogel, but the water absorbability of ABS and SLA photosensitive resin were similar to PMMA. Considering both pore size and water absorbability, ABS and SLA photosensitive resin materials which have a similar performance with PMMA of conventional MR phantom shell material in waterproof and anti-seepage could be an effective alternative to PMMA for phantoms and inserts.