1. Radiologic Evaluation of Intracranial Tumors
Todd Gourdin M-IV
Radiology Final Presentation August 2, 2007

2. Available Modalities
1)X-ray
2)CT
3)MRI
4)Nuclear Medicine

3. X-ray Primarily of historical interest since the onset of CT in 1974.
Was useful for detecting increased intracranial pressure and intracranial calcifications.

5. Craniopharnygioma

6. CT Most intracranial neoplasms are visible on CT
Tumors may be hypodense, isodense, or hyperdense on a noncontrast CT depending on tumor histology and location

7. Pilocytic Cerebellar Astrocytoma

8. Metastatic Lesion

9. Small tumors or isodense tumors may be missed on noncontrast CT but highlight after contrast administration
- Meningiomas and Neuromas enhance strongly with contrast while low-grade gliomas and epidermoid tumors do not enhance.

10. Why not MRI them all???
MRI is generally preferable to CT for evaluating intracranial neoplasms
CT is preferred for visualizing tumor calcification or intratumor hemorrhage.

11. Commonly Calcified and Hemorrhagic Lesions
Calcified Hemorrhagic
Oligodendroglioma Glioblastoma multiforme
Choroid Plexus tumor Oligodendroglioma
Ependymoma Metastatic:
Central neurocytoma Melanoma
Craniopharyngioma Breast
Teratoma Lung
Chordoma

12. Ependymoma

13. Glioblastoma Multiforme

14. MRI
Usually the preferred method of imaging intracranial tumors due to better soft-tissue contrast
MRI exploits increased water content of many neoplasms. This water content shows up as increased signal on T2 weighted images and decreased signal on T1 Images.

15. Noncontrast MRI of Meningioma

16. Contrast(often IV Gadolinium) helps visualize small tumors that don’t cause much edema.

17. Advanced MRI Techniques
“This stuff is complicated!!!!”

18. Proton Magnetic Resonance Spectroscopy
Analyzes the biochemical makeup of a tumor to create a characteristic spectroscopic pattern.
- Computer analysis of the pattern allows histologic type to be determined non-invasively.

19. Figure 98-3 Proton magnetic resonance spectroscopy; the choline peak (3.22 p.p.m.) is elevated, the creatine peak (3.03 p.p.m.) is low and the N-acetyl aspartate peak (2.01 p.p.m.) is nearly undetectable; characteristic spectroscopic appearance of gliomas (choline—CHO; creatine—PCr/Cr; N-acetyl aspartate—NAA). “Grainger and Allison’s Diagnostic Radiology, 2001”

20. Perfusion weighted MRI
Technique used to determine the relative cerebral blood volume (rCBV) of intracranial structures.
- Many tumors are highly vascularized allowing them to be distinguished from the background on a perfusion weighted MRI.

21. Meningioma
T Contrasted T Perfusion-Weighted

22. MRI-guided Surgery
A variety of techniques have been developed to incorporate MRI into the surgical process for intracranial tumor resection:
MRI guided stereotactic biopsy
Brain surface imaging
Interventional MRI

23. Brain Surface Imaging

24. Interventional MRI

25. Nuclear Medicine SPECT(Single Photon Emission Computed Tomography)
Gamma rays emitted during radionuclide decay are detected by a gamma camera that rotates about the patient’s head
- The radionuclides must cross the blood-brain barrier

26. Radionuclides preferentially taken up by intracranial neoplasms include:
201 TI Chloride
99m Tc MIBI
123 I a-methyl tyrosine
111 In octreotide
- Can be used for example in distinguishing between benign lesions, low-grade gliomas, and high-grade gliomas

27. SPECT of Normal Brain
Radionuclide = 99m TC

28. 201 T1 SPECT
Diagnosed by SPECT as a high-grade glioma and confirmed post-resection

29. PET(Positron Emission Tomography)
Similar to SPECT but the radioisotopes used decay to produce positrons
These positrons quickly combine with an adjacent electron to produce two gamma rays that travel in opposite directions. Detection of these gamma rays allows calculation of their exact point of origin.
Can evaluate different brain processes depending on the radioisotope selected

30. Radionuclides useful for PET analysis of intracranial tumors include:
Fluorodeoxyglucose
C methionine
F a-methyl tyrosine

31. Advantages of PET over SPECT:
- Can be used to quantify emission
Better resolution
Disadvantages of PET:
Cost
Limited availability
Need for a cyclotron(particle accelerator)

32. PET scan of Language Center
Figure 98-4 H215O PET activation study during a language task in a young man with a right frontal glioma, before neurosurgical resection. Language activation is seen bilaterally and is distant from the tumour “Grainger and Allison’s Diagnostic Radiology, 2001”

33. Classification of Intracranial Neoplasms
1)Neuroepithelial Origin – astrocytoma, oligodendroglioma, ependymoma, mixed glioma, choroid plexus tumor, neuronal tumor, pineal tumor.
-Gliomas(astrocytomas, oligodendroglioma, ependymoma) = approximately 50% of primary brain tumors
-Graded from 1 -4 based on severity
-Grade 4 = Glioblastoma Multiforme – most common primary intracranial neoplasm

34. GBM Hallmark finding is tumor necrosis Often cross the midline
Extremely poor prognosis

35. 2)Tumors of Nerve Sheath – Schwannoma, Neurofibroma
- These are cranial nerve sheath tumors that show marked enhancement with IV contrast

36. Bilateral schwannomas in NF type 2

37. 3)Meningeal tumors – meningioma
Originate from “arachnoid cell rests” in the dura matter
Commonly arise from parasagittal region, cerebral convexities, sphenoid ridge, and olfactory groove
Often contain calcifications and enhance well with IV contrast
Represents approximately 15% of primary intracranial tumors

38. Meningioma

39. 4)Lymphoma 2-3% of intracranial neoplasms
Well defined, rounded lesions that appear hyperdense on noncontrast CT and enhace well with contrast
Lymphomas may appear “atypical” in the immunocompromised

40. Lymphoma on noncontrast/contrast CT

41. 5)Metastasis
Usually multiple lesions which help distinguish them from supratentorial gliomas
Often found at grey/white matter junction

42. Metastases

43. 6)Additional classes include: germ cell tumors, dermoid/epidermoid cysts, sellar/pituitary tumors,

44. Some famous people who have suffered from a brain tumor

45. References Harvard University Dept. of Radiology
LSU Dept. of Radiology
University of South Carolina Dept. of Radiology
Grainger and Allison’s Diagnostic Radiology: A Textbook of Medical Imaging, 4th ed Churchill Livinstone Inc., 2001.