Table 2.

The radiogenomic biomarkers linking imaging features/phenotypes to gene expression patterns in the studies

Genes/Molecular biomarkers	Characteristics	Imaging biomarkers	Number of studies	Ref
EGFR	Diffusion	relative CBV, PSR	10	13
	Morphology	Anatomic location (radiogenomic maps)		35, 36
		Percentage of CE, NE, necrosis & oedema and largest diameter on lesion		7
	Morphology, diffusion & interaction with ECM	Border sharpness, restricted water diffusion, ADC		37
	Gene expressions	CE, necrosis, mass effect, oedema, cortical involvement, CE:N volume ratio, T2heterogeneity		38
		Infiltration, proliferation, neurogenesis and synaptic transmission		39
	Perfusion	VP & Ktrans		40
		Normalized CBV & CBF		41
		Mean & relative TBF		42
MGMT methylation status	Perfusion	Ktrans	5	43
	Normalized CBV		44
Morphology	Anatomic location		35, 36 ]
	Textures	Correlation, energy, entropy & local intensity		45
IDH1	Morphology	Location	4	35
	Metabolite changes	Percentage of CE, NE, necrosis & oedema and largest diameter on lesion 2-hydroxyglutarate (2HG)		7 [46, 47
	Perfusion	TBF		48
TP53	Morphology	Percentage of CE, NE, necrosis & oedema and largest diameter on lesion	2	7
	Gene expressions	CE, necrosis, mass effect, oedema, cortical involvement, CE:N volume ratio, T2 heterogeneity		38
PTEN loss	Morphology	Anatomic location	2	36
		Percentage of CE, NE, necrosis & oedema and largest diameter on lesion		7
Ki-67 index	Diffusion, perfusion, metabolite change & genomics	relative CBF, FA, ADC, Cho/Cr, NAA/Cho, NAA/Cr, Lac/Cr & MI	3	49, 50
	Gene expressions	CE, necrosis, mass effect, oedema, cortical involvement, CE:N volume ratio, T2 heterogeneity		38
VEGFR	Morphology and textural	Shape, texture, edge sharpness of necrotic core and surrounding CE rim	2	51
	Vascularization	CBV		52
1p/19q codeletions	Vascularization	relative CBV	1	53
GAP4 and WWTR1 genes	Intensities (ROI), sharpness of lesion boundaries, boundary shapes	Edge sharpness of necrotic portion	1	18
HRAS copy number variation	Contrast enhancement and genetic expressions	Proportion of enhancing tumour & T1/FLAIR ratio	1	8
Periostin and miR-219	Cellular invasion	Edema/invasion FLAIR volumes	1	54
Molecular subclasses of GBM	Hemodynamics	relative CBV	1	52

ADC, apparent diffusion coefficient; CBF, cerebral blood flow;CBV, cerebral blood volume; CE, contrast enhancement; CE:N, contrast-enhancing volume to the necrotic tumour volume ratio; ECM, extra cellular matrix; EGFR,epidermal growth factor receptor; Cho, choline; Cr, creatine; FA, fractional anisotropy; IDH1,isocitrate dehydrogenase1; Ki-67antigen; K_trans, volume transfer constant; Lac, lactate; MGMT, O₆-methylguanine-DNA-methyltransferase; MI, myo-inositol; NAA, N-acetyl aspartate; NE, non-enhanced; PDGFA, platelet-derived growth factor; ROI, region of interest; PSR, percent signal recovery; PTEN, phosphatase and tensin homolog; TBF, tumour blood flow; TP53, tumour protein p53; VEGFR, vascular endothelial growth factor receptor; VP, plasma volume.