The latest advances in MRI(Contd.)

3. Perfusion Imaging
Contrast augmented Dynamic Susceptibility Contrast EPI (DSC-EPI), a method for assessing the passage of a bolus of MR contrast agent through the brain (perfusion), is a combination of imaging sequences and post processing software that enhances the ability of magnetic resonance to detect and characterise diseases of the brain.
Single shot spin echo EPI techniques can be used to track the passage of a contrast agent through the substance of the brain. When processed with a Negative Enhancement Integral algorithm, the imaging data can be transformed into a map that precisely portrays the areas of the brain that the bolus passed through [Cerebral Blood Volume (CBV) maps].

Clinical/Patient Advantages: Acute Stroke
In the critical first few hours after the onset of stroke symptoms, contrast augmented DSC-EPI may be invaluable in planning therapeutic intervention.
While diffusion weighted EPI may indicate areas of the brain that have already been compromised, contrast augmented DSC-EPI will indicate the extent of brain tissue that has also been relatively devascularised, and therefore is at a risk of irreversible injury. When significant discrepancies exist between the region at risk, as identified on contrast augmented DSC-EPI, and the area already compromised, as identified on diffusion weighted EPI, the patient may benefit from medical brain protective therapy. Intervention with thrombolytic agents in this acute setting may produce a more favourable patient outcome with lower morbidity and mortality. Conversely, if these two areas coincide, the risk of thrombolytic intervention might be avoided.

NEI image reveals corresponding defect in PCA territory.

4. Spectroscopy A 33-year-old female presented for evaluation two weeks post partum, complaining of left sided headaches and new onset tonic-clonic seizures. An MRI exam demonstrated a large, heterogeneous appearing, non-enhancing left temporo-parietal lesion with associated mass effect. Differential diagnostic considerations after correlation with the clinical picture included haemorrhage/haemorrhagic infarction and neoplasm. PROBE-SV assessment of the lesion was remarkable for the lack of choline (CHO) elevation, low N-acetyl-aspartate (NAA) and the presence of significant lactate (LAC/LAP) accumulation, favouring the diagnosis of infarction and mitigating against the presence of neoplasm. In this case, because of the patient's clinical status, excisional biopsy and brain decompression were performed confirming the absence of neoplasm. The wealth of chemical information available from MRS (Magnetic Resonance Spectroscopy) makes it a potentially useful and effective diagnostic tool.