7.1a. Contrast axial T1 Wtd MRI

1. 7.1a. Contrast axial T1 Wtd MRI 7.1b. Contrast coronal T1 Wtd MRI 7.1c. Contrast sagittal T1 Wtd MRI Figure 7.1: An enhancing ring lesion within the left posterior frontal lobe Diagnosis: Pyogenic Abscess Differential diagnosis: Metastasis While abscess can be differentiated from metastasis by MR imaging, appropriate patients clinical history and clinical findings are needed to aid in accurate diagnosis.

2. 7.2a,b,c. Pre-Contrast axial T1 Wtd MRI 7.2d,e,f. Post-Contrast axial T1 Wtd MRI Figure 7.2: Multiple enhancing ring lesions in a immunocompromised patient Diagnosis: Fungal Abscesses Differential diagnosis: Multiple Metastasis While abscess can be differentiated from metastasis by MR imaging, appropriate patients clinical history and clinical findings are needed to aid in accurate diagnosis.

3. Fig 7.3a. T2-weighted images of the brain at just above the level of roof of the lateral ventricles of a young homosexual man. Findings: Diagnosis: Areas of T2-weighted hyperintensity within the deep paraventricular white matter (arrows). Human Immunodeficiency Virus (HIV) Encephalopathy A myelin-stained section of the brain specimen reveals severe diffuse myelin pallor (*). Horizontal section of the brain revealing abnormal left frontal lobe white matter from demyelinization (arrow).

4. Fig. 7.3b. T2-weighted image of the brain at the level of frontal horns of a young homosexual man Findings: Diagnosis: Foci of T2-weighted hyperintensity involving the peripheral white matter at or close to cortico-medullary junction (arrows) and left basal ganglia (arrow head). Progressive Multifocal Leukoencephalopathy

5. Fig 7.3c. Post-contrast axial CT image of the brain at the level of frontal horns/basal ganglia of a young homosexual man. Findings: Diagnosis: Enhancing ring lesion (arrow) within the left caudate nucleus. Primary CNS Lymphoma Coronal brain section reveals a tumor involving the left caudate nucleus (arrows). Photomicrographic show perivascular collections of lymphoma cells

6. Fig 7.3d. Post-contrast axial CT image of the brain at the level of the basal ganglia of a drug addict Findings: Diagnosis: Enhancing ring lesion (arrow) within the right caudate nucleus. CNS Toxoplasmosis Horizontal section of the right hemisphere reveals an irregular necrotic lesion in the right caudate nucleus

7. Fig. 7.3e. T1-weighted image of the brain at the level of frontal horns of a young homosexual man 7.3e. Pre-Contrast Axial T1 Wtd MRI Diagnosis: Findings: Focal area of T1 Wtd low signal intensity, capping the right frontal horn. Cytomegalo Virus Infection.

8. Fig 7.3f. Axial T2 Wtd image of the Brain. Diagnosis: Findings: Cryptococcal Meningitis Multiple small areas of increased T2 Wtd signal within both basal ganglia (arrows). Coronal brain section reveals multiple soap-bubble like lesions in the basal ganglia (arrows). Photo micrograph reveals encapsulated Cryptococcus neoformans with budding forms (arrow).