Table 1.

MR characteristics of post-treatment radiation necrosis and tumor.

	Sequence
Entity	T1C	T2	DSC MR Perfusion	MR Spectroscopy	DWI	Notable comments
Radiation Necrosis	↑	↑	↓ rCBV	Variable Cho/Cr ↓ Cho/NAA ↑ Lipids	Variable/↓	"Swiss cheese-like" enhancement
Recurrent Tumor	↑	↑	↑ rCBV	↑ Cho/Cr ↑ Cho/NAA	Variable/↑	Multiple lesions, cross midline
Pseudoprogression	↑→↓	↑→↓	↓ rCBV/ Variable	Variable	Variable	Follow-up imaging important
Pseudoresponse	↓→↑	↓→↑	↓ rCBV/ Variable	Variable	Variable	Follow-up imaging important; occurs with anti-angiogenic drugs