Brain metastases

Preliminary Diagnosis: Brain Metastases

I. What imaging technique is first-line for this diagnosis?

• MRI imaging of the brain with intravenous contrast

II. Describe the advantages and disadvantages of this technique for diagnosis of brain metastases.

Advantages

• Highly suggestive of etiology in appropriate clinical situation

• Able to localize exact anatomic area of disease and as a result predict any current or potential neurologic compromise

• Can assess for secondary complications such as mass effect, midline shift, hemorrhage, etc

• Does not utilize ionizing radiation

Disadvantages

• Expensive

• Time consuming and requires significant patient cooperation

• Very susceptible to motion artifact

• MRI with IV contrast requires a renal function of at least GFR >30

III. What are the contraindications for the first-line imaging technique?

MRI is contraindicated in patients with non-MR-compatible metallic hardware or foreign body.

IV. What alternative imaging techniques are available?

• Enhanced and nonenhanced CT

• PET/CT

V. Describe the advantages and disadvantages of the alternative techniques for diagnosis of brain abscesses.

Enhanced (intravenous contrast) and nonenhanced CT

Advantages

• May be performed much quicker than MRI

• Can be performed on unstable patients

• Associated with less motion artifact

Disadvantages

• Often misses lesions unless hemorrhagic, calcified, or associated with significant vasogenic edema

• Demonstrates less anatomic detail and contrast resolution compared with MRI

• Exposes the patient to ionizing radiation

PET/CT

Advantages

• High sensitivity and specificity for detecting tumors

• Often used to distinguish between neoplasm and radiation necorsis, a common mimicker

• Can often differentiate benign versus malignant lesions based on hypermetabolism

• Ability to detect distant disease affecting staging and therapy

Disadvantages

• High degree of radiation exposure to patient

• Cannot detect small lesions (i.e. less than 1.5 cm)

• Limited anatomic detail

VI. What are the contraindications for the alternative imaging techniques?

Enhanced and nonenhanced CT imaging

• Contraindicated in pregnant patients. especially within the first two trimesters

• IV contrast is relatively contraindicated in patients with contrast or iodine allergy. If IV contrast is necessary, the patient must be prepped with antihistamines and corticosteroids.

• Relative contraindication in patients with renal dysfunction

PET/CT

• Contraindicated in pregnant patients especially within the first two trimesters