Saturday, September 22, 2012

Encephalitis

1-It appears as a hypo intense lesion in T1 and hyper intense lesion in T2 in deep and sub cortical white matter with edges resemble that of vasogenic edema ( finger like ), with no definite mass effect or shift of the mid line structures.

2-Examples as HIV and Herpes simplex encephalitis.

3- Other D.D.:

-Adrenoleucodystrophy (A).

-Tuberculoma (T).

-Radiation injury (R).               E  D  A           T

-Deep white matter ischemia (D).

-Encephalomalacia (E).

4-Adrenoleucodystrophy:

Bilateral, symmetrical coming out from ventricles.


5-Encephalitis and tuberculoma:




6-Radiation injury:





7-Encephalomalacia:

As the mass effect resolves and the infarcted tissue is resorbed, the adjacent sulci and ventricle will enlarge. The end result is a chronic infarct with focal areas of cystic encephalomalacia and some surrounding parenchymal change due to gliosis.



Saturday, September 8, 2012

Brain tumors and MRS



1-In brain tumors, the following changes will occur putting in your consideration that as the malignancy increased these changes will be more apparant:

-NAA: Decreases as the tumor will destroy the neurones.

-Creatine: Decreases as tumors with high metabolism will reduce the energy store.

-Choline: Increases as hyper cellular tumors with rapid growth will increase it.

-Lactate: Increases when tumor exceeds the capability of its blood supply and try to increase anerobic glycolysis.

-Lipids: Increased  in necrotic portion of the tumor.

2-In case of tumor recurrance, choline will be increased.

3-You should evaluate the presence of high choline outside the enhanced margins of the mass to see the true extension of the tumor.

4-Following radiation, there are decreased NAA, creatine and choline.

5- In case of radiation necrosis, Increased lipid and lactate.

6-In case of meningioma, there is increased alanine at 1.48 ppm with no NAA, very low creatine and increased glutamates.


The normal MR spectra obtained from gray matter and white matter are shown below. Predominant metabolites, displayed from right to left, are NAA, creatine, choline, and myo-inositol. The primary difference between the two spectra is that gray matter has more creatine.� Hunter's angle is the line formed by the metabolites on the white matter spectrum. The common way to analyze clinical spectra is to look at metabolite ratios, namely NAA/Cr, NAA/Cho, and Cho/Cr. Normal and abnormal values are shown in the chart above. By including a known reference solution when acquiring the MR spectral data, absolute concentrations of metabolites can be calculated.


  

Normal MRS


In vivo MR spectroscopy of normal brain. Axial T2-weighted MR image shows a single voxel of interest for MR spectroscopy (white box) placed within the brain parenchyma in a healthy volunteer (A). The corresponding in vivo MR spectrum shows the normal dominant peaks of NAA at 2.0 ppm (arrow), Cr at 3.0 ppm, and Cho at 3.2 ppm (B).
Normal MR spectra obtained from gray matter and white matter are shown on the right. The predominant metabolites, displayed from right to left, are NAA, creatine, choline, and myo-inositol. The primary difference between the two spectra is that gray matter has more creatine.Hunter's angle is the line formed by the metabolites on the white matter spectrum. The common way to analyze clinical spectra is to look at metabolite ratios, namely NAA/Cr, NAA/Cho, and Cho/Cr. Normal and abnormal values are shown in the chart to the right. By including a known reference solution when acquiring the MR spectral data, absolute concentrations of metabolites can be calculated.