Glioma MRI

Pilocytic astrocytoma

1. T1: Iso- to hypointense solid component

2. T2: Hyperintense solid component

Low-grade astrocytoma

1. T1:

• Isointense to hypointense
• Confined to the white matter and causes expansion of the adjacent cortex

2. T2/FLAIR:

• Mass-like hyperintense signals
• Confined to the white matter and causes expansion of the adjacent cortex
• Cortex can also be involved in late cases in comparison to the oligodendroglioma, which is a cortical based tumor from the start
• Microcystic changes along the line of spread
• High T2 signal (not related to cellularity or cellular atypia, but rather edema, demyelination, and other degenerative changes)

3. DWI:

• No restricted diffusion
• Increased diffusibility

4. T1 C+ (Gd): No enhancement

5. MR spectroscopy:

• Tumor will show elevated choline peak, low NAA peak, and elevated choline/creatine ratio
• Lack of the lactate peak

6. MR perfusion: No elevation of rCBV

Anaplastic astrocytoma

1. T1: Hypointense

2. T2: Hyperintense but can be heterogeneous, if calcification of blood present

3. T1 C+ (Gd):

• Variable enhancement
• Presence of ring enhancement suggests central necrosis

4. MR spectroscopy:

• Increased choline/creatine ratio
• NAA preserved or mildly depressed
• No significant lactate
• Intermediate levels of myo-inositol (lower than low grade, higher than glioblastoma)

5. MR perfusion: Elevated cerebral blood volume

Glioblastoma multiforme

1. T1:

• Hypo- to isointense mass within white matter
• Central heterogenous signal (necrosis, intratumoral hemorrhage)

2. T1 C+ (Gd):

• Variable enhancement
• Typically peripheral and irregular with nodular components
• Completely surrounds necrosis

3. T2/FLAIR:

• Hyperintense
• Surrounded by vasogenic edema
• Flow voids

4. GE/SWI:

• Susceptibility artifact on T2 from blood products or calcification
• Low intensity rim from blood product
• Located inside the peripheral enhancing component
• Absent dual rim sign

5. DWI/ADC:

• Solid component
• Elevated signal on DWI is common in solid / enhancing component
• Diffusion restriction is typically intermediate similar to normal white matter, but significantly elevated compared to surrounding vasogenic edema
• ADC values correlate with grade:

• WHO IV (GBM) = 745 ± 135 x 10-6 mm2/s
• WHO III (anaplastic) = 1067 ± 276 x 10-6 mm2/s
• WHO II (low grade) = 1273 ± 293 x 10-6 mm2/s
• ADC threshold value of 1185 x 10-6 mm2/s sensitivity (97.6%) and specificity (53.1%) in the discrimination of high-grade (WHO grade III & IV) and low-grade (WHO grade II) gliomas

6. Non-enhancing necrotic / cystic component: Vast majority (>90%) have facilitated diffusion (ADC values > 1000 x 10-6 mm2/s)

7. MR perfusion: rCBV elevated compared to lower grade tumors and normal brain

8. MR spectroscopy:

• Choline: increased
• Lactate: increased
• Lipids: increased
• NAA: decreased
• Myo-inositol: decreased

Oligodendroglioma

1. T1: Hypointense

2. T2: Hyperintense

3. SWI: Calcium seen as areas of “blooming”

4. T1 C+ (Gd): Contrast enhancement is common

5. DWI: No diffusion restriction

6. MR perfusion: increased vascularity “chicken wire” network of vascularity results in elevated relative cerebral blood volume (rCBV)

Ependymoma

1. T1: Iso- to hypointense solid component

2. T2: Hyperintense to white matter

3. SWI: Foci of blooming from hemorrhage or calcification

4. T1 C+ (Gd): Heterogenous enhancement

5. DWI/ADC: Restricted diffusion in solid components

6. MR spectroscopy:

• Increased choline
• Decreased NAA
• Elevated choline/creatine ratio
• Increased lipid and lactate