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Diffusion-weighted and diffusion tensor imaging of the brain, made easy.

Huisman TA - Cancer Imaging (2010)

Bottom Line: In addition, DWI/DTI allows exploring the microarchitecture of the brain.A detailed knowledge of the basics of DWI/DTI is mandatory to better understand pathology encountered and to avoid misinterpretation of typical DWI/DTI artifacts.This article reviews the basic physics of DWI/DTI exemplified by several classical clinical cases.

View Article: PubMed Central - PubMed

Affiliation: Division Pediatric Radiology, Johns Hopkins Hospital, Baltimore, MD 21287-0842, USA. thuisma1@jhmi.edu

ABSTRACT
Diffusion-weighted and diffusion tensor imaging (DWI/DTI) has revolutionized clinical neuroimaging. Pathology may be detected earlier and with greater specificity than with conventional magnetic resonance imaging sequences. In addition, DWI/DTI allows exploring the microarchitecture of the brain. A detailed knowledge of the basics of DWI/DTI is mandatory to better understand pathology encountered and to avoid misinterpretation of typical DWI/DTI artifacts. This article reviews the basic physics of DWI/DTI exemplified by several classical clinical cases.

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Example of a 10-year-old female with a left cerebellar pilocytic astrocytoma. The T2- and contrast-enhanced T1-weighted images reveal a large peripherally solid, partially contrast enhancing, centrally necrotic/cystic tumor in the left cerebellar hemisphere. DWI and ADC maps show an increased diffusion within the cystic component excluding abscess formation. The FA maps show a lack of internal diffusion directionality as characterized by the FA hypointensity. The green-encoded white matter tracts in the middle cerebellar peduncle are compressed; the internal fiber architecture of the brainstem is preserved but mildly displaced.
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Figure 10: Example of a 10-year-old female with a left cerebellar pilocytic astrocytoma. The T2- and contrast-enhanced T1-weighted images reveal a large peripherally solid, partially contrast enhancing, centrally necrotic/cystic tumor in the left cerebellar hemisphere. DWI and ADC maps show an increased diffusion within the cystic component excluding abscess formation. The FA maps show a lack of internal diffusion directionality as characterized by the FA hypointensity. The green-encoded white matter tracts in the middle cerebellar peduncle are compressed; the internal fiber architecture of the brainstem is preserved but mildly displaced.

Mentions: In clinical routine, DWI/DTI has proved to be especially helpful in the early recognition of cerebral ischemia (Fig. 8). DWI/DTI may show tissue injury within 30 min of vessel occlusion, before conventional T1- or T2-weighted sequences show pathology. By combining the DWI/DTI data with perfusion-weighted imaging (PWI), tissue at risk for imminent infarction can be identified. Typically the core of infarction is characterized by a matching area of DWI/PWI abnormality surrounded by an area of oligemic tissue without matching diffusion abnormality (penumbra). If the oligemia persists, this area of DWI/PWI mismatch may evolve into infarction. Recognition of these differential areas of oligemia has initiated various neuroprotective treatment options as well as interventions. In addition, lesions with restricted diffusion (e.g. cytotoxic brain edema) and increased diffusion (vasogenic edema) can be differentiated using DWI/DTI (Fig. 9). This may have prognostic significance because cytotoxic edema (e.g. in ischemia) is frequently irreversible; vasogenic edema (e.g. infectious) may be reversible. Moreover, analysis of the DTI scalars may also help to differentiate between an abscess and a necrotic tumor (Fig. 10) or between an arachnoid cyst and an epidermoid cyst (Fig. 11) within the basal cisterns. The time evolution of the ADC and FA scalars in cerebral stroke also helps to date lesions. In ischemia, a pseudo-normalization of the ADC values may be seen at 10 days of ischemic injury.Figure 8


Diffusion-weighted and diffusion tensor imaging of the brain, made easy.

Huisman TA - Cancer Imaging (2010)

Example of a 10-year-old female with a left cerebellar pilocytic astrocytoma. The T2- and contrast-enhanced T1-weighted images reveal a large peripherally solid, partially contrast enhancing, centrally necrotic/cystic tumor in the left cerebellar hemisphere. DWI and ADC maps show an increased diffusion within the cystic component excluding abscess formation. The FA maps show a lack of internal diffusion directionality as characterized by the FA hypointensity. The green-encoded white matter tracts in the middle cerebellar peduncle are compressed; the internal fiber architecture of the brainstem is preserved but mildly displaced.
© Copyright Policy
Related In: Results  -  Collection

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Figure 10: Example of a 10-year-old female with a left cerebellar pilocytic astrocytoma. The T2- and contrast-enhanced T1-weighted images reveal a large peripherally solid, partially contrast enhancing, centrally necrotic/cystic tumor in the left cerebellar hemisphere. DWI and ADC maps show an increased diffusion within the cystic component excluding abscess formation. The FA maps show a lack of internal diffusion directionality as characterized by the FA hypointensity. The green-encoded white matter tracts in the middle cerebellar peduncle are compressed; the internal fiber architecture of the brainstem is preserved but mildly displaced.
Mentions: In clinical routine, DWI/DTI has proved to be especially helpful in the early recognition of cerebral ischemia (Fig. 8). DWI/DTI may show tissue injury within 30 min of vessel occlusion, before conventional T1- or T2-weighted sequences show pathology. By combining the DWI/DTI data with perfusion-weighted imaging (PWI), tissue at risk for imminent infarction can be identified. Typically the core of infarction is characterized by a matching area of DWI/PWI abnormality surrounded by an area of oligemic tissue without matching diffusion abnormality (penumbra). If the oligemia persists, this area of DWI/PWI mismatch may evolve into infarction. Recognition of these differential areas of oligemia has initiated various neuroprotective treatment options as well as interventions. In addition, lesions with restricted diffusion (e.g. cytotoxic brain edema) and increased diffusion (vasogenic edema) can be differentiated using DWI/DTI (Fig. 9). This may have prognostic significance because cytotoxic edema (e.g. in ischemia) is frequently irreversible; vasogenic edema (e.g. infectious) may be reversible. Moreover, analysis of the DTI scalars may also help to differentiate between an abscess and a necrotic tumor (Fig. 10) or between an arachnoid cyst and an epidermoid cyst (Fig. 11) within the basal cisterns. The time evolution of the ADC and FA scalars in cerebral stroke also helps to date lesions. In ischemia, a pseudo-normalization of the ADC values may be seen at 10 days of ischemic injury.Figure 8

Bottom Line: In addition, DWI/DTI allows exploring the microarchitecture of the brain.A detailed knowledge of the basics of DWI/DTI is mandatory to better understand pathology encountered and to avoid misinterpretation of typical DWI/DTI artifacts.This article reviews the basic physics of DWI/DTI exemplified by several classical clinical cases.

View Article: PubMed Central - PubMed

Affiliation: Division Pediatric Radiology, Johns Hopkins Hospital, Baltimore, MD 21287-0842, USA. thuisma1@jhmi.edu

ABSTRACT
Diffusion-weighted and diffusion tensor imaging (DWI/DTI) has revolutionized clinical neuroimaging. Pathology may be detected earlier and with greater specificity than with conventional magnetic resonance imaging sequences. In addition, DWI/DTI allows exploring the microarchitecture of the brain. A detailed knowledge of the basics of DWI/DTI is mandatory to better understand pathology encountered and to avoid misinterpretation of typical DWI/DTI artifacts. This article reviews the basic physics of DWI/DTI exemplified by several classical clinical cases.

Show MeSH
Related in: MedlinePlus