MRI imaging of brain tumors. A practical approach.

A logarithmic approach to diagnosis of intra-axial tumors.

1. MRI imaging of brain tumors. A practical approach. Dr. Hazem Abu Zeid Yousef Assistant professor of radiodiagnosis . Assiut University Hospital.

2. Brain tumor imaging objectives

3. What is my job?

4. What protocol to use? Scout. Axial T1W, T2W & FLAIR. DWI, ADC & DTI. Perfusion. SWI. Axial, Sagittal & Coronal post Gd T1W. Proton MRS SV & Multivoxel . 3D T1W volume.

5. What is each sequences tells about the tumor? Conventional sequences (T1WI, T2WI & FLAIR). Post contrast T1WI. Perfusion MRI. SWI. MRS. DWI & DTI.

6. Conventional sequences (T1WI, T2WI & FLAIR). Post contrast T1WI. Perfusion MRI. SWI. MRS. DWI & DTI Conventional sequences (T1WI, T2WI & FLAIR).

7. Peritumoral edema Vasogenic cerebral oedema  refers to a type of  cerebral edema  in which the blood brain barrier (BBB) is disrupted (c.f.  cytotoxic edema  where BBB is intact). It is an extracellular oedema which mainly affects the white matter, through leakage of fluid out of capillaries. It may be minor or major, rounded or irregular. It is most frequently seen around  brain tumors  (both primary and secondary) but is may be seen around non tumorous conditions.

8. Necrosis Caused by sudden vascular occlusion. Endothelial proliferation and thrombosis are predisposing factors. Poor prognosis in adult glioma .

9. Calcification It is usually a sign of slowly growing lesion. It is best assessed in CT.

10. Pilocytic astrocytoma WHO grade I Ependymoma WHO grade II Medulloblastoma WHO grade IV

11. Cysts Neoplastic cysts (arises within the tumor and has enhancing walls). Non neoplastic cysts (reactive, arising in the neighbouring parenchyma and mural enhancement is absent).

12. Medulloblastoma WHO grade IV

13. Ependymoma WHO grade II

14. Glioblastoma Multiforme WHO grade IV

15. Hemorrhage Due to pathological changes in the tumor vessels. It is rare (0.8-10.2%) and is usually typical of malignant tumors .

16. Hemorrhagic metastatic melanoma.

17. Size. Edema . Location. Necrosis. Calcification. Hemorrhage . Cysts. Unpredective of grading

18. Conventional sequences (T1WI, T2WI & FLAIR). Post contrast T1WI. Perfusion MRI. SWI. MRS. DWI & DTI. Post contrast T1WI.

19. Post contrast scan Contrast material enhancement in the central nervous system is a combination of two primary processes: intravascular (vascular) enhancement and interstitial (extravascular) enhancement.   Intravascular enhancement may reflect neovascularity , vasodilatation or hyperemia , and shortened transit time or shunting . Interstitial enhancement indicates abnormal BBB.

20. Diffuse astrocytoma WHO grade II

21. Dysembryoplastic Neuroepithelial Tumor (DNET)   WHO grade I

22. GBM WHO grade IV Primary CNS lymphoma WHO grade IV

23. Meningioma WHO gradeI Choroid plexus papilloma WHO grade I

24. Conventional sequences (T1WI, T2WI & FLAIR). Post contrast T1WI. Perfusion MRI. SWI. MRS. DWI & DTI. Perfusion MRI.

25. Perfusion MRI Perfusion imaging allows some insight into angiogenesis “development of new arteries from pre-existing arteries” , a process essential for neoplastic growth. Neoplastic induced angiogenesis results in structurally abnormal vessels that tend to be leaky, and thus neoplasms have increased permeability parameters on perfusion MR images.

26. The more aggressive a neoplasm The more abnormal its vascularity. Greater vascular tortuosity. Greater vascular density. Greater permeability. Higher tumor blood volume.

27. Representative CBV maps from (A) a grade II fibrillary astrocytoma, (B) a grade III anaplastic astrocytoma, and (C) a grade IV glioblastoma multiforme . ©2005 by American Society of Neuroradiology Tufail F. Patankar et al. AJNR Am J Neuroradiol 2005;26:2455-2465

28. WHO Grade II astrocytoma

29. WHO Grade III anaplastic astrocytoma

30. WHO Grade IV GBM

31. WHO Grade I meningioma

32. Primary CNS lymphoma WHO grade IV

33. Perfusion MRI Predective of grading Neoangiogenesis is one of the key features of high grade tumours .

34. Conventional sequences (T1WI, T2WI & FLAIR). Post contrast T1WI. Perfusion MRI. SWI. MRS. DWI & DTI. SWI.

35. Susceptibility weighted imaging (SWI) SWI is a technique that exploits the susceptibility difference between tissues to provide contrast for different regions of the brain. In essence, it uses the deoxygenated hemoglobin of veins, hemosiderin of hemorrhage, etc. as intrinsic contrast agents, allowing for much better visualization of blood and microvessels even without administration of an external contrast agent.

36. SWI is an innovative new technique to demonstrate microvessels and tumor neoangiogenesis in exquisite detail based on the presence of ITSS ( intratumoral susceptibility signals) thereby aiding in tumor grading. Higher the ITSS score higher the tumor grade.

37. Grade I astrocytoma

38. Oligodendroglioma grade II

39. Glioblastoma multiforme WHO grade IV

40. Glioblastoma multiforme WHO grade IV

41. Conventional sequences (T1WI, T2WI & FLAIR). Post contrast T1WI. Perfusion MRI. SWI. MRS. DWI & TWI. MRS.

42. MR Spectroscopy Proton magnetic resonance spectroscopy (MRS) provides a noninvasive method for characterizing the cellular biochemistry which underlies brain pathologies, as well as for monitoring the biochemical changes after treatment in vivo.

43. The brain metabolites that are commonly seen on the MR spectrum are

44. Glioblastoma multiforme WHO Grade IV showing “sky high” choline.

45. Cerebellar grade I astrocytoma

46. Conventional sequences (T1WI, T2WI & FLAIR). Post contrast T1WI. Perfusion MRI. SWI. MRS. DWI & TWI DWI & DTI.

47. Diffusion weighted imaging (DTI) The degree of restriction to water diffusion is correlated with tissue cellularity and integrity of cell membranes. Generally, malignant tumors have enlarged nuclei and show hypercellularity . These characteristics reduce the extracellular matrix and the diffusion space of water protons in the extracellular areas, with a resultant decrease in the ADC value.

48. Grade ADC value

49. Anaplastic astrocytoma III

50. Medulloblastoma WHO IV

51. DWI of ring enhancing lesions The necrotic component of brain tumor (GBM and metastases) show marked hypo intensity on DW images and increased ADC values due to increased free water. This finding can be used to differentiate necrotic tumors from cerebral abscess, which demonstrates marked diffusion restriction.  

52. Hypercellularity is one of the key features of high grade tumours . Predective of grading

53. Diffusion tensor ( tractography )

54. Radiology Vol. 243, No. 2: 539-550 ©RSNA, 2007

55. Thank you