Radiologic Evaluation of Radiologic Evaluation of Intracranial TumorsIntracranial Tumors

Todd Gourdin M-IV Radiology Final Presentation August 2, 2007

Available ModalitiesAvailable Modalities

1)X-ray1)X-ray

2)CT2)CT

3)MRI3)MRI

4)Nuclear Medicine4)Nuclear Medicine

X-rayX-ray

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

- Was useful for detecting increased Was useful for detecting increased intracranial pressure and intracranial intracranial pressure and intracranial calcifications.calcifications.

CraniopharnygiomaCraniopharnygioma

CTCT

- Most intracranial neoplasms are visible on Most intracranial neoplasms are visible on CTCT

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

Pilocytic Cerebellar Pilocytic Cerebellar AstrocytomaAstrocytoma

Metastatic LesionMetastatic Lesion

- Small tumors or isodense tumors may be Small tumors or isodense tumors may be missed on noncontrast CT but highlight missed on noncontrast CT but highlight after contrast administrationafter contrast administration

- Meningiomas and Neuromas enhance - Meningiomas and Neuromas enhance strongly with contrast while low-grade strongly with contrast while low-grade gliomas and epidermoid tumors do not gliomas and epidermoid tumors do not enhance.enhance.

Why not MRI them all???Why not MRI them all???

- MRI is generally preferable to CT for MRI is generally preferable to CT for evaluating intracranial neoplasmsevaluating intracranial neoplasms

- CT is preferred for visualizing tumor CT is preferred for visualizing tumor calcification or intratumor hemorrhage.calcification or intratumor hemorrhage.

Commonly Calcified and Commonly Calcified and Hemorrhagic LesionsHemorrhagic Lesions

Calcified Calcified HemorrhagicHemorrhagicOligodendroglioma Glioblastoma multiforme Oligodendroglioma Glioblastoma multiforme

Choroid Plexus tumor OligodendrogliomaChoroid Plexus tumor Oligodendroglioma

Ependymoma Metastatic:Ependymoma Metastatic:

Central neurocytoma MelanomaCentral neurocytoma Melanoma

Craniopharyngioma BreastCraniopharyngioma Breast

Teratoma LungTeratoma Lung

ChordomaChordoma

EpendymomaEpendymoma

Glioblastoma MultiformeGlioblastoma Multiforme

MRIMRI

- Usually the preferred method of imaging Usually the preferred method of imaging intracranial tumors due to better soft-tissue intracranial tumors due to better soft-tissue contrastcontrast

- MRI exploits increased water content of MRI exploits increased water content of many neoplasms. This water content many neoplasms. This water content shows up as increased signal on T2 shows up as increased signal on T2 weighted images and decreased signal on weighted images and decreased signal on T1 Images.T1 Images.

Noncontrast MRI of MeningiomaNoncontrast MRI of Meningioma

T2T1

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

Advanced MRI TechniquesAdvanced MRI Techniques

“This stuff is complicated!!!!”

Proton Magnetic Resonance Proton Magnetic Resonance SpectroscopySpectroscopy

- Analyzes the biochemical makeup of a Analyzes the biochemical makeup of a tumor to create a characteristic tumor to create a characteristic spectroscopic pattern.spectroscopic pattern.

- Computer analysis of the pattern allows - Computer analysis of the pattern allows histologic type to be determined non-histologic type to be determined non-invasively. invasively.

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”

Perfusion weighted MRIPerfusion weighted MRI

- Technique used to determine the relative Technique used to determine the relative cerebral blood volume (rCBV) of cerebral blood volume (rCBV) of intracranial structures.intracranial structures.

- Many tumors are highly vascularized - Many tumors are highly vascularized allowing them to be distinguished from the allowing them to be distinguished from the background on a perfusion weighted MRI.background on a perfusion weighted MRI.

Meningioma Meningioma

T2 Contrasted T1 Perfusion-Weighted

MRI-guided SurgeryMRI-guided Surgery

- A variety of techniques have been A variety of techniques have been developed to incorporate MRI into the developed to incorporate MRI into the surgical process for intracranial tumor surgical process for intracranial tumor resection:resection:

MRI guided stereotactic biopsyMRI guided stereotactic biopsy

Brain surface imagingBrain surface imaging

Interventional MRIInterventional MRI

Brain Surface ImagingBrain Surface Imaging

Interventional MRIInterventional MRI

Nuclear MedicineNuclear Medicine

SPECT(Single Photon Emission Computed SPECT(Single Photon Emission Computed Tomography)Tomography)

- Gamma rays emitted during radionuclide Gamma rays emitted during radionuclide decay are detected by a gamma camera decay are detected by a gamma camera that rotates about the patient’s headthat rotates about the patient’s head

- The radionuclides must cross the blood-- The radionuclides must cross the blood-brain barrierbrain barrier

Radionuclides preferentially taken up by Radionuclides preferentially taken up by intracranial neoplasms include:intracranial neoplasms include:

201201 TI Chloride TI Chloride99m 99m Tc MIBITc MIBI123123 I I -methyl tyrosine-methyl tyrosine111111 In octreotide In octreotide

- Can be used for example in distinguishing - Can be used for example in distinguishing between benign lesions, low-grade gliomas, and between benign lesions, low-grade gliomas, and high-grade gliomashigh-grade gliomas

SPECT of Normal BrainSPECT of Normal Brain

Radionuclide = 99m TC

201201 T1 SPECT T1 SPECT

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

PET(Positron Emission PET(Positron Emission Tomography)Tomography)

- Similar to SPECT but the radioisotopes used decay to Similar to SPECT but the radioisotopes used decay to produce positronsproduce positrons

- These positrons quickly combine with an adjacent These positrons quickly combine with an adjacent electron to produce two gamma rays that travel in electron to produce two gamma rays that travel in opposite directions. Detection of these gamma rays opposite directions. Detection of these gamma rays allows calculation of their exact point of origin.allows calculation of their exact point of origin.

- Can evaluate different brain processes depending on Can evaluate different brain processes depending on the radioisotope selectedthe radioisotope selected

Radionuclides useful for PET analysis of Radionuclides useful for PET analysis of intracranial tumors include:intracranial tumors include:

FluorodeoxyglucoseFluorodeoxyglucose

C methionineC methionine

F F -methyl tyrosine-methyl tyrosine

Advantages of PET over SPECT:Advantages of PET over SPECT:- Can be used to quantify emission- Can be used to quantify emission- Better resolutionBetter resolution

Disadvantages of PET:Disadvantages of PET:- CostCost- Limited availabilityLimited availability- Need for a cyclotron(particle accelerator)Need for a cyclotron(particle accelerator)

PET scan of Language CenterPET 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”

Classification of Intracranial Classification of Intracranial NeoplasmsNeoplasms

1)Neuroepithelial Origin – 1)Neuroepithelial Origin – astrocytoma, astrocytoma, oligodendroglioma, ependymoma, mixed glioma, choroid oligodendroglioma, ependymoma, mixed glioma, choroid plexus tumor, neuronal tumor, pineal tumor.plexus tumor, neuronal tumor, pineal tumor.

-Gliomas(astrocytomas, oligodendroglioma, ependymoma) -Gliomas(astrocytomas, oligodendroglioma, ependymoma) = approximately 50% of primary brain tumors = approximately 50% of primary brain tumors

-Graded from 1 -4 based on severity-Graded from 1 -4 based on severity

-Grade 4 = Glioblastoma Multiforme – most common -Grade 4 = Glioblastoma Multiforme – most common primary intracranial neoplasmprimary intracranial neoplasm

GBMGBM

-Hallmark finding is tumor necrosis

-Often cross the midline

- Extremely poor prognosis

2)Tumors of Nerve Sheath – 2)Tumors of Nerve Sheath – Schwannoma, Schwannoma, NeurofibromaNeurofibroma

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

Bilateral schwannomas in NF type Bilateral schwannomas in NF type 22

3)Meningeal tumors – 3)Meningeal tumors – meningiomameningioma

- Originate from “arachnoid cell rests” in the dura matterOriginate from “arachnoid cell rests” in the dura matter

- Commonly arise from parasagittal region, cerebral convexities, Commonly arise from parasagittal region, cerebral convexities, sphenoid ridge, and olfactory groovesphenoid ridge, and olfactory groove

- Often contain calcifications and enhance well with IV contrastOften contain calcifications and enhance well with IV contrast

- Represents approximately 15% of primary intracranial tumorsRepresents approximately 15% of primary intracranial tumors

MeningiomaMeningioma

4)Lymphoma 4)Lymphoma - 2-3% of intracranial neoplasms2-3% of intracranial neoplasms

- Well defined, rounded lesions that appear hyperdense Well defined, rounded lesions that appear hyperdense on noncontrast CT and enhace well with contraston noncontrast CT and enhace well with contrast

- Lymphomas may appear “atypical” in the Lymphomas may appear “atypical” in the immunocompromisedimmunocompromised

Lymphoma on noncontrast/contrast Lymphoma on noncontrast/contrast CTCT

5)Metastasis5)Metastasis

- Usually multiple lesions which help distinguish them from Usually multiple lesions which help distinguish them from supratentorial gliomassupratentorial gliomas

- Often found at grey/white matter junctionOften found at grey/white matter junction

MetastasesMetastases

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

Some famous people who have Some famous people who have suffered from a brain tumorsuffered from a brain tumor

ReferencesReferences

Harvard University Dept. of RadiologyHarvard University Dept. of Radiology

www.brighamrad.harvard.edu

LSU Dept. of RadiologyLSU Dept. of Radiology

www.medschool.lsuhsc.edu

University of South Carolina Dept. of RadiologyUniversity of South Carolina Dept. of Radiology

www.radiology.med.sc.edu

Grainger and Allison’s Diagnostic Radiology: A Textbook of Medical Grainger and Allison’s Diagnostic Radiology: A Textbook of Medical Imaging, 4Imaging, 4thth ed. 2001 Churchill Livinstone Inc., 2001. ed. 2001 Churchill Livinstone Inc., 2001.