Most common tumor of brain - brain metastaes or secondaries.
Approximately 40% of intracranial neoplasms are metastatic. (1)
Primaries which most commonly metastasize includes 1.Lungs 2.Breast 3.Melanoma 4.Kidney 5.Colon cancers in descending order of frequencies.(2)
Modality :(1)
MRI with Contrast enhancement is the method of choice.
CT used because of availability and low cost.
CT SCAN:
A. CECT
1.Enhancing solid lesion with prominent edema
2.Enhancing rim lesion with prominent edema in lesion which have outgrown the blood supply.
"On findings of multiple, enhancing solid lesions at the gray matter–white matter junction and prominent surrounding edema in a patient with known primary cancer, a diagnosis of metastases may be confidently made. Approximately 90% of patients with a history of cancer who present with a single supratentorial lesion have brain metastases."(1)
B.NON CECT
"On noncontrast CT, the density of metastatic lesions may be less than, equal to, or greater than that of adjacent brain parenchyma. Most of the patterns are variable and are nondiagnostic"(1)
Non CECT useful in detecting Hemorrhagic and calicified mets. A highdensity metastasis is more often hemorrhagic than calcific.(1)
MRI :
1.CONTRAST ENHANCED
Uniform or Ringlike enhancement with edema for detecting any mets and especially for small mets and those surrounded extensively and obscured by edema.
2. NON CONTRAST
Hemorrhagic mets and melanoma :
high signal in T1 and high or low signal on T2
T2W Image - neoplastic nodule may blend with surrounding edema and obscure the diagnosis.
"Contrast-enhanced MRI is the best method for detection of meningeal tumor seeding, which appears as abnormal dural enhancement. This is a nonspecific finding; however, in the correct clinical setting, it correlates with the presence of sheets of tumor cells affecting the meninges"(1)
"Following administration of a contrast agent, solid, nodular (see first image below), or irregular ring patterns of enhancement are seen. Nonenhancing lesions (see second image below) are less likely to be metastases."(1).Exception is cystic metastases, which does not enhance or shows only rim enhancement like abscesses.
Bibliography:
1.Emedicine Radiology
2.Grainger Allison Textbook of Diagnostic radiology
Approximately 40% of intracranial neoplasms are metastatic. (1)
Primaries which most commonly metastasize includes 1.Lungs 2.Breast 3.Melanoma 4.Kidney 5.Colon cancers in descending order of frequencies.(2)
Modality :(1)
MRI with Contrast enhancement is the method of choice.
CT used because of availability and low cost.
CT SCAN:
A. CECT
1.Enhancing solid lesion with prominent edema
2.Enhancing rim lesion with prominent edema in lesion which have outgrown the blood supply.
"On findings of multiple, enhancing solid lesions at the gray matter–white matter junction and prominent surrounding edema in a patient with known primary cancer, a diagnosis of metastases may be confidently made. Approximately 90% of patients with a history of cancer who present with a single supratentorial lesion have brain metastases."(1)
B.NON CECT
"On noncontrast CT, the density of metastatic lesions may be less than, equal to, or greater than that of adjacent brain parenchyma. Most of the patterns are variable and are nondiagnostic"(1)
Non CECT useful in detecting Hemorrhagic and calicified mets. A highdensity metastasis is more often hemorrhagic than calcific.(1)
"IV administration of contrast material (30-40 g iodine) increases the diagnostic accuracy of CT. Most metastases enhance after a standard dose of IV contrast. Use of a higher dose of contrast (80-85 g of iodine) and delaying scanning by 1-3 hours after injection of the contrast agent lead to a further increase in the detection of multiple metastases; such an approach is appropriate if MRI is not available"
MRI :
1.CONTRAST ENHANCED
Uniform or Ringlike enhancement with edema for detecting any mets and especially for small mets and those surrounded extensively and obscured by edema.
2. NON CONTRAST
Hemorrhagic mets and melanoma :
high signal in T1 and high or low signal on T2
T2W Image - neoplastic nodule may blend with surrounding edema and obscure the diagnosis.
"Lesions are isointense to mildly hypointense on T1-weighted images; they are hyperintense on T2-weighted images or with fluid attenuation inversion recovery.
Surrounding edema is relatively hypointense on fluid attenuation inversion recovery and on T1-weighted images; they are hyperintense on T2-weighted images." (1)
"Contrast-enhanced MRI is the best method for detection of meningeal tumor seeding, which appears as abnormal dural enhancement. This is a nonspecific finding; however, in the correct clinical setting, it correlates with the presence of sheets of tumor cells affecting the meninges"(1)
"Following administration of a contrast agent, solid, nodular (see first image below), or irregular ring patterns of enhancement are seen. Nonenhancing lesions (see second image below) are less likely to be metastases."(1).Exception is cystic metastases, which does not enhance or shows only rim enhancement like abscesses.
Bibliography:
1.Emedicine Radiology
2.Grainger Allison Textbook of Diagnostic radiology
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