What is the interpretation of Computed Tomography (CT) perfusion of the brain?

From the Guidelines

CT perfusion of the brain is interpreted by analyzing blood flow parameters to identify areas of ischemia or infarction, with the goal of identifying potentially salvageable tissue and guiding acute stroke management decisions. When interpreting a CT perfusion scan, look for mismatches between cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT) 1. The ischemic core, representing irreversibly damaged tissue, shows decreased CBF and CBV with increased MTT. The penumbra, which is potentially salvageable tissue, typically shows decreased CBF, normal or slightly decreased CBV, and increased MTT. This mismatch pattern (decreased CBF with preserved CBV) helps identify patients who might benefit from reperfusion therapies like thrombectomy or thrombolysis.

Key Parameters for Interpretation

• Cerebral blood flow (CBF): decreased in ischemic core and penumbra
• Cerebral blood volume (CBV): decreased in ischemic core, normal or slightly decreased in penumbra
• Mean transit time (MTT): increased in ischemic core and penumbra
• Mismatch between CBF, CBV, and MTT: indicates potentially salvageable tissue

Clinical Application

CT perfusion helps guide acute stroke management decisions by determining if there is salvageable brain tissue that could benefit from intervention, even beyond traditional time windows for treatment 1. The results of CT perfusion can be used to:

• Identify patients with at-risk brain regions who may benefit from intra-arterial thrombolysis or mechanical clot retrieval
• Triage patients to other available therapies, such as induced hypertension
• Inform disposition decisions regarding intensive monitoring of patients with large abnormally perfused brain regions

Limitations and Considerations

• Artifacts from patient movement, beam hardening from bone, or vascular calcifications can affect image quality and should be considered during interpretation
• The time since symptom onset should be considered, as the penumbra gradually converts to infarct over time
• CT perfusion should be used in conjunction with other imaging modalities and clinical information to guide management decisions 1

From the Research

Interpretation of CT Perfusion of the Brain

The interpretation of Computed Tomography (CT) perfusion of the brain is a complex process that involves analyzing various parameters to assess cerebral blood flow and volume.

• CT perfusion imaging is used to evaluate acute ischemic stroke and guide treatment decisions 2, 3, 4.
• The interpretation of CT perfusion images involves differentiating between ischemic penumbra and core infarct using parameters such as cerebral blood volume (CBV), cerebral blood flow (CBF), mean transit time (MTT), and time to peak (TTP) 2.
• Different software, such as conventional vendor-provided CTP software and RAPID automated software, can be used to interpret CT perfusion images, each with its own tiebreaker for differentiating between ischemic penumbra and core infarct 2.
• CT perfusion imaging can also provide prognostic information, such as the hypoperfusion and CBV index, which can help guide treatment decisions 2.
• The technique of CT perfusion imaging involves acquiring images over time to assess changes in cerebral blood flow and volume, and can be used in combination with other imaging modalities, such as CT angiography, to provide a comprehensive assessment of cerebral perfusion 3, 5.

Clinical Applications

• CT perfusion imaging has a range of clinical applications, including:
  • Diagnosing acute ischemic stroke and guiding treatment decisions 2, 3, 4.
  • Assessing cerebral perfusion impairment in acute ischemic patients 5.
  • Evaluating functional reserve in cerebrovascular disease 5.
  • Diagnosing, grading, and monitoring intracranial neoplasms 5.
• CT perfusion imaging can also be used to identify patterns of brain perfusion that are favorable for recanalization therapy in patients with acute stroke 3.
• Recent studies have explored the use of machine learning algorithms to reduce scan duration and radiation dose in cerebral CT perfusion imaging, while preserving clinical content 6.