What type of computed tomography (CT) scan should be ordered to assess for a brain bleed?

CT Imaging for Brain Hemorrhage Assessment

A non-contrast CT scan of the head is the imaging modality of choice for the initial assessment of suspected brain hemorrhage. 1

Rationale for Non-Contrast CT as First-Line Imaging

Non-contrast CT (NCCT) is superior to other imaging modalities for detecting acute intracranial hemorrhage for several key reasons:

• High sensitivity for acute blood: CT is excellent at detecting fresh blood due to its hyperdensity (appears bright white) compared to brain tissue 1, 2
• Rapid acquisition time: Critical in emergency situations where time-to-diagnosis impacts outcomes
• Widespread availability: Available in most emergency departments 24/7
• Few contraindications: Unlike MRI, no need to screen for metal implants or devices 1

The American College of Radiology (ACR) Appropriateness Criteria specifically rates non-contrast head CT with a score of 9 (highest rating) for suspected acute subarachnoid hemorrhage, confirming it as the gold standard initial test 1.

When to Consider Additional Imaging

After initial non-contrast CT confirms hemorrhage, further vascular imaging may be indicated:

1. CT Angiography (CTA):

   • Should be performed if aneurysm or vascular malformation is suspected 1
   • Particularly useful after detection of subarachnoid or parenchymal hemorrhage 1
   • Can be added immediately following the initial non-contrast CT 1

2. MRI/MRA:

   • More sensitive for subacute and chronic hemorrhage 2, 3
   • Better for detecting small or early ischemic changes
   • Consider when CT is negative but clinical suspicion remains high 4
   • Gradient echo sequences particularly sensitive for detecting prior hemorrhages 1

3. CT Venography (CTV):

   • Consider when venous sinus thrombosis is suspected 1
   • Alternative when MR venography is not possible 1

Important Clinical Considerations

• Timing matters: CT sensitivity is highest for acute hemorrhage (first few hours) 2
• False negatives: Small hemorrhages or isodense subacute hemorrhages may be missed on CT 4, 3
• Radiation exposure: CT involves ionizing radiation, which should be considered especially in young patients or those requiring serial imaging 1
• Contrast considerations: If CTA is needed following NCCT, ensure patient has no contraindications to iodinated contrast (renal impairment, severe allergy) 5

Algorithm for Brain Hemorrhage Imaging

1. Initial presentation with suspected brain hemorrhage:

   • Perform non-contrast CT head immediately 1

2. If hemorrhage detected on non-contrast CT:

   • Proceed to CTA if vascular etiology suspected (aneurysm, AVM) 1, 6
   • Consider CT venography if venous sinus thrombosis suspected 1

3. If non-contrast CT negative but clinical suspicion remains high:

   • Consider MRI with gradient echo/susceptibility-weighted sequences 4, 3
   • These sequences are more sensitive for detecting small hemorrhages missed on CT 3

4. For follow-up imaging of known hemorrhage:

   • Non-contrast CT for acute monitoring (first days)
   • MRI better for subacute/chronic phase evaluation 2

By following this evidence-based approach, clinicians can optimize detection of brain hemorrhage while minimizing unnecessary radiation exposure and contrast administration.