背景:精确的光剂量测定是恶性神经胶质瘤的间质光动力疗法(iPDT)中一个复杂的挑战。理想地,光剂量测定应当基于组织形态和目标区域中的每种组织类型的个体光学组织性质。首次研究报告了使用NMR信息来估计单个光学组织特性的变化。
方法:研究猪脑组织和光学组织体模。对猪的大脑来说,添加补充剂以模拟水肿或高血液含量。组织体模基于琼脂,Lipeveneous,墨水,血液和gadobutrol(基于Gd的MRI造影剂)。改变体模成分和组织添加剂的浓度,以比较浓度依赖性对光学和NMR性能的影响。使用3特斯拉全身MRI系统来确定T1和T2弛豫时间。光学组织特性,即,光谱分辨吸收和降低散射系数,是使用单个积分球设置获得的。将观察到的NMR和光学性质的变化相互比较。
结果:通过将组织体模的NMR弛豫时间和光学组织特性调整为文献值,人类脑肿瘤的食谱,获得了同时模拟这些脑组织的白质和灰质组织体模。对于猪的脑组织,观察到随着组织中水浓度的增加,核磁共振弛豫时间都增加了,而在635nm处,µa降低,µs\'增加。将血液添加到猪脑样品中显示出恒定的T1,而T2缩短,并且在635nm处的吸收系数增加。
结论:在这项调查中,通过改变样本内容,已观察到NMR弛豫时间和光学组织性质的显着变化,并检查了它们的关系。开发的双NMR/光学组织体模可用于iPDT研究,临床培训和演示。
BACKGROUND: Accurate light dosimetry is a complex remaining challenge in interstitial photodynamic therapy (iPDT) for malignant gliomas. The light dosimetry should ideally be based on the tissue morphology and the individual optical tissue properties of each tissue type in the target region. First investigations are reported on using NMR information to estimate changes of individual optical tissue properties.
METHODS: Porcine brain tissue and optical tissue phantoms were investigated. To the porcine brain, supplements were added to simulate an edema or high blood content. The tissue phantoms were based on agar, Lipoveneous, ink, blood and gadobutrol (Gd-based MRI contrast agent). The concentrations of phantom ingredients and tissue additives are varied to compare concentration-dependent effects on optical and NMR properties. A 3-tesla whole-body MRI system was used to determine T1 and T2 relaxation times. Optical tissue properties, i.e., the spectrally resolved absorption and reduced scattering coefficient, were obtained using a single integrating sphere setup. The observed changes of NMR and optical properties were compared to each other.
RESULTS: By adjusting the NMR relaxation times and optical tissue properties of the tissue phantoms to literature values, recipes for human brain tumor, white matter and grey matter tissue phantoms were obtained that mimic these brain tissues simultaneously in both properties. For porcine brain tissue, it was observed that with increasing water concentration in the tissue, both NMR-relaxation times increased, while µa decreased and µs\' increased at 635 nm. The addition of blood to porcine brain samples showed a constant T1, while T2 shortened and the absorption coefficient at 635 nm increased.
CONCLUSIONS: In this investigation, by changing sample contents, notable changes of both NMR relaxation times and optical tissue properties have been observed and their relations examined. The developed dual NMR/optical tissue phantoms can be used in iPDT research, clinical training and demonstrations.