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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Todd Gourdin M-IV
Radiology Final Presentation August 2, 2007
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
- Meningiomas and Neuromas enhance strongly with contrast while low-grade gliomas and epidermoid tumors do not enhance.
MRI is generally preferable to CT for evaluating intracranial neoplasms
CT is preferred for visualizing tumor calcification or intratumor hemorrhage.
Oligodendroglioma Glioblastoma multiforme
Choroid Plexus tumor Oligodendroglioma
Central neurocytoma Melanoma
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.
“This stuff is complicated!!!!”
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”
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
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
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
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
Radionuclide = 99m TC
Diagnosed by SPECT as a high-grade glioma and confirmed post-resection
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
F a-methyl tyrosine
- Can be used to quantify emission
Disadvantages of PET:
Need for a cyclotron(particle accelerator)
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”
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
- These are cranial nerve sheath tumors that show marked enhancement with IV contrast
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
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.