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Radiologic Evaluation of Intracranial Tumors. Todd Gourdin M-IV Radiology Final Presentation August 2, 2007. Available Modalities. 1)X-ray 2)CT 3)MRI 4)Nuclear Medicine. X-ray. Primarily of historical interest since the onset of CT in 1974.

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Radiologic Evaluation of Intracranial Tumors

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radiologic evaluation of intracranial tumors

Radiologic Evaluation of Intracranial Tumors

Todd Gourdin M-IV

Radiology Final Presentation August 2, 2007

available modalities
Available Modalities




4)Nuclear Medicine

x ray

Primarily of historical interest since the onset of CT in 1974.

Was useful for detecting increased intracranial pressure and intracranial calcifications.


Most intracranial neoplasms are visible on CT

Tumors may be hypodense, isodense, or hyperdense on a noncontrast CT depending on tumor histology and location

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.

why not mri them all
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.

commonly calcified and hemorrhagic lesions
Commonly Calcified and Hemorrhagic Lesions

Calcified Hemorrhagic

Oligodendroglioma Glioblastoma multiforme

Choroid Plexus tumor Oligodendroglioma

Ependymoma Metastatic:

Central neurocytoma Melanoma

Craniopharyngioma Breast

Teratoma Lung



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.

advanced mri techniques
Advanced MRI Techniques

“This stuff is complicated!!!!”

proton magnetic resonance spectroscopy
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.


Figure 98-3Proton 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”

perfusion weighted mri
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.


T2 Contrasted T1 Perfusion-Weighted

mri guided surgery
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

nuclear medicine
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

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

spect of normal brain
SPECT of Normal Brain

Radionuclide = 99m TC

201 t1 spect
201 T1 SPECT

Diagnosed by SPECT as a high-grade glioma and confirmed post-resection

pet positron emission tomography
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

Radionuclides useful for PET analysis of intracranial tumors include:


C methionine

F a-methyl tyrosine

Advantages of PET over SPECT:

- Can be used to quantify emission

Better resolution

Disadvantages of PET:


Limited availability

Need for a cyclotron(particle accelerator)

pet scan of language center
PET scan of Language Center

Figure 98-4H215O 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”

classification of intracranial neoplasms
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

  • Hallmark finding is tumor necrosis
  • Often cross the midline
  • Extremely poor prognosis
2)Tumors of Nerve Sheath – Schwannoma, Neurofibroma

- These are cranial nerve sheath tumors that show marked enhancement with IV contrast

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


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


Usually multiple lesions which help distinguish them from supratentorial gliomas

Often found at grey/white matter junction

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

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. 2001 Churchill Livinstone Inc., 2001.