Table 4.

MR elastography studies in animal brain tumor models.

Author, year	Study goal	Model	Major findings
Jamin et al. (2015)	Studied elasticity and viscosity in glioma and metastatic breast cancer models.	Glioma (U-87 MG human glioblastoma cells or RG2 rat glioma cells) and metastatic breast cancer (MDA-MB-231 LM2-4 human triple-negative breast carcinoma cells) female mice models.	All tumors were softer and less viscous than surrounding healthy brain parenchyma. Gliomas derived from U-87 MG were the stiffest and breast cancer metastases (MDA-MB-231 cells) were the softest. Tumor elasticity and viscosity correlated positively with cellular density and microvessel density, but not with extent of collagen deposition nor myelin fiber entrapment.
Schregel et al. (2017)	Explored longitudinal changes of elastic properties in glioblastoma	Glioblastoma stem cell line (G30) established from a patient implanted in five mice. MRE was performed at 2, 3 and 4 weeks post implantation.	Starting from week 2, viscoelastic modulus, shear wave speed and phase angle were significantly lower in tumors when compared with healthy brain tissue. Tumors became softer over time with tumor progression. Tumor heterogeneity increased starting at weeks 3 and 4. Softer tumor regions contained necrosis and patches of viable tumor cells. Dense tumor regions had areas of densely packed tumor cells and blood vessels.
Feng et al. (2016)	Impact of radiotherapy on elasticity of glioblastoma and unaffected brain.	Twelve 7–8 weeks age female Balb/c mice implanted with glioblastoma were randomized to either 20 Gy radiation treatment or no treatment groups.	Shear modulus was lower in tumor relative to mirror brain and decreased over time independently of radiation therapy. Radiation therapy was effective and prolonged mice survival time. Shear modulus of the mirror brain regions remained in treatment group and had increasing trend in not treated animals.