Haemorrhage MRI Imaging Characteristics
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Questions and Answers

What is a characteristic feature of hyperacute and late subacute phases in isotropic/trace DWI images?

  • Low ADC values
  • Hypointense on T2 imaging
  • Isointense on T1 imaging
  • High-signal-only appearance (correct)

How do the ADC values compare in different stages of haematoma evolution?

  • Fluctuate widely throughout all stages
  • Substantially lower than normal white matter in most stages (correct)
  • Similar to normal grey matter at all times
  • Higher in all stages except chronic

What happens to the T1 and T2 signal characteristics during the acute stage of haematoma as it evolves?

  • T1 become hypointense while T2 remains isointense
  • T1 becomes hyperintense and T2 becomes hypointense
  • T1 becomes isointense and T2 becomes hyperintense (correct)
  • Both T1 and T2 remain hypointense

What can confound attempts at reliably dating the age of an extracranial haemorrhage?

<p>The heterogeneous appearance of extracranial haematomas (B)</p> Signup and view all the answers

What effect does the presence of blood products in a cavity have on the utility of diffusion restriction for diagnosing pus in an abscess?

<p>Results in low ADC values, reducing diagnostic utility (B)</p> Signup and view all the answers

What imaging characteristic depends on the oxygenation state of hemoglobin?

<p>The age of the blood (C)</p> Signup and view all the answers

Which type of hemoglobin has a strong paramagnetic effect due to the presence of unpaired electrons?

<p>Methemoglobin (B), Deoxyhemoglobin (D)</p> Signup and view all the answers

How does methaemoglobin affect T2* weighted sequences on MRI?

<p>It creates a blooming artifact (A), It causes signal loss (C)</p> Signup and view all the answers

Which MRI sequence is primarily affected by the presence of red blood cell lysis?

<p>T2* weighted sequences (C)</p> Signup and view all the answers

What is the primary characteristic of oxyhemoglobin in terms of its magnetic properties?

<p>It is weakly diamagnetic (D)</p> Signup and view all the answers

What factor primarily influences the appearance of hemorrhage on MRI over time?

<p>The age of the blood (B)</p> Signup and view all the answers

In which state is hemoglobin mostly found in arterial blood?

<p>Oxyhemoglobin (C)</p> Signup and view all the answers

What effect does the presence of blood proteins have on T1 signals during hyperacute and acute hemorrhages?

<p>It results in intermediate T1 signals (A)</p> Signup and view all the answers

Flashcards

Haemoglobin states

Different forms of haemoglobin (oxygenated, deoxygenated, oxidized) that impact MRI signal.

Oxyhaemoglobin

Oxygenated haemoglobin, weakly diamagnetic, little effect on T2*.

Deoxyhaemoglobin

Deoxygenated haemoglobin, strongly paramagnetic, significant signal loss on T2*.

Methaemoglobin

Oxidized haemoglobin, strongly paramagnetic, also causes signal loss on T2*.

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T2* weighted sequence

MRI sequence sensitive to changes in magnetic susceptibility; affected by haemoglobin state and cell lysis.

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Intracellular vs. extracellular hemoglobin

Difference in signal loss patterns dependent on whether haemoglobin is inside red blood cells or outside.

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Age of Hemorrhage

The time elapsed since the hemorrhage occurred, affects imaging characteristics.

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MRI sensitivity to acute hemorrhage

While MRI might appear insensitive to acute hemorrhage, modern sequences can detect it.

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Haematoma Evolution Stages

Five stages describing the changes in a blood clot over time: hyperacute, early subacute, late subacute, chronic, and very chronic.

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Hyperacute Haematoma

The initial stage (14-28 days) of a blood clot, characterized by high signal on T2-weighted images due to extracellular hemichromes.

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T2* Signal Loss

Decrease in signal intensity on T2*-weighted images caused by paramagnetic substances like deoxyhemoglobin and methemoglobin.

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Haemoglobin & Paramagnetism

Different forms of hemoglobin have varying paramagnetic properties, affecting T2* signal. Deoxyhemoglobin and methemoglobin are strongly paramagnetic.

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ADC in Haematoma

Apparent Diffusion Coefficient (ADC) maps show lower values in hematomas than normal white matter, except in chronic stages.

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Study Notes

Haemorrhage on MRI Imaging Characteristics

  • Haemorrhage appearance on MRI varies significantly, dependent on several factors:

    • Blood age
    • Haemoglobin type (oxy-, deoxy-, or met-)
    • Red blood cell wall integrity (intra- vs. extracellular)
    • MRI sequence used
  • MRI is often considered insensitive to acute haemorrhage, but newer sequences can detect it.

  • Haemorrhage presentation changes over time; therefore, precise age estimation is challenging.

Physiology of Blood on MRI

  • Haemoglobin oxygenation state significantly impacts MRI signal:
    • Oxyhaemoglobin (95% arterial, 70% venous): weakly diamagnetic, minimal effect on T2* and T1.
    • Deoxyhaemoglobin: strongly paramagnetic, substantial signal loss on T2* sequences (e.g., SWI), creating blooming artifacts.
    • Methemoglobin: strongly paramagnetic, similar to deoxyhaemoglobin in its effect on T2* sequences.

MRI Sequences and Haemorrhage

  • T1-weighted sequences: little effect from oxy- and deoxyhaemoglobin; blood proteins result in intermediate signals in hyperacute/acute haemorrhages.

  • T2-weighted sequences (e.g., SWI, gradient-echo):* primarily affected by haemoglobin oxygenation and cell lysis.

    • Within RBCs, deoxy/met-hemoglobin leads to signal loss.
    • After cell lysis, even distribution of paramagnetic effects reduces signal loss.
    • Haemosiderin/ferritin ingestion by monocytes/macrophages result in uneven, paramagnetic effects causing signal loss.
  • Diffusion-weighted imaging (DWI):

    • Apparent diffusion coefficient (ADC) maps: substantially lower values than normal white matter in all stages except chronic.
    • Isotropic/trace DWI images: High signal hyperacute and late subacute phases due to combined T2 and diffusion effects

Stages of Haematoma Evolution

  • Hyperacute (1-14 days):
    • Periphery: Hypointense on T1, T2, and SWI (rim).
    • Centre: Isointense on T1, hyperintense on T2; low DWI, high ADC, variable SWI.
  • Ageing blood appearance factors: influenced by the extracranial/intracranial location, and heterogeneous appearance affecting the reliability of dating extracranial haemorrhage.

Practical Considerations

  • Extracranial vs. Intracranial Haemorrhages: Extracranial blood products age differently than intracranial ones, and have a more heterogeneous appearance.
  • Subacute/Chronic Blood: appear hypointense and show blooming on T2* weighted sequences (e.g., SWI).
  • Blood in cavities: result in low ADC values; making diffusion restriction not useful for differentiating blood from an abscess.

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Description

Explore the imaging characteristics of haemorrhage on MRI. This quiz covers factors such as blood age, haemoglobin type, and the effect of various MRI sequences. Delve into the physiology of blood and the impact of oxygenation on MRI signals.

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