Radiology 5th year, 1st & 2nd lectures (Dr. Ameer)

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The lecture has been given on Feb. 10th & 17th, 2011 by Dr. Ameer.

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Radiology 5th year, 1st & 2nd lectures (Dr. Ameer)

  1. 1. Skull & Brain Imaging Techniques Plain……..trauma CT & MRI …standard investig. US Angiography….Limited to stenosis. aneurysm & AVM
  2. 2. Imaging Techniques <ul><li>Plain …. </li></ul><ul><li>Normal….inner & outer tables (compact) </li></ul><ul><li>Diploic space ( spongy bone ) </li></ul><ul><li>Sutures remain visible even </li></ul><ul><li>after fusion. </li></ul><ul><li>Metopic suture. Inconstant </li></ul><ul><li>vascular impressions </li></ul><ul><li>arachnoid granulations </li></ul><ul><li>position of calc. pineal body. </li></ul>
  3. 3. Plain film…..cont. <ul><li>Abnormal plain films; look for </li></ul><ul><li>-intra-cranial calcifications </li></ul><ul><li>-pit. fossa…..pit. tumors </li></ul><ul><li>-bones for lytic, sclerotic, # </li></ul><ul><li>-calcifications & signs of raised ICP are </li></ul><ul><li>import. signs in the plain films. </li></ul>
  4. 4. Intracranial calcifications <ul><li>Most intra-cranial calcif. is normal & of no significance. </li></ul><ul><li>Normal intra-cranial calcifications: </li></ul><ul><li>pineal, choroid, interclinoid, petroclinoid, falx, atheromatous calcification in carotid. </li></ul><ul><li>pathological calcifications: </li></ul><ul><li>primary tumors, meningioma, glioma, craniopharyngioma, AVM , aneurysm & old abscess. </li></ul>
  5. 5. Raised ICP <ul><li>Plain film abnormality in prolonged cases. </li></ul><ul><li>Sutural diastasis. </li></ul><ul><li>Destruction of dorsum sellae. </li></ul>
  6. 6. Lytic & sclerotic lesions in the skull <ul><li>Lytic lesions </li></ul><ul><li>Metast. & M.M. </li></ul><ul><li>Geographic skull in histiocytosis X. </li></ul><ul><li>Osteoporosis circumscripta …paget’s </li></ul><ul><li>Sclrotic lesions </li></ul><ul><li>Hyperostosis frontalis interna….commonest cause </li></ul><ul><li>Localized sclerosis…St. mixed with lytic in </li></ul><ul><li>meningioma, metastases, fibrous dysplasia </li></ul><ul><li>Paget’s ……cotton-wool app. (thickening of calvarum) </li></ul>
  7. 7. CT Brain <ul><li>Normal CT </li></ul><ul><li>Abnormal CT cardinal signs </li></ul><ul><li>-abnormal tissue density </li></ul><ul><li>high density…recent hge, calcified and contrast enhancement </li></ul><ul><li>low density….neoplasm, infarct, oedema (surrounding neoplasm, infarcts, hge, inflammation) </li></ul>
  8. 8. Abnormal CT…cont. <ul><li>Mass effect ..compressed or displaced </li></ul><ul><li>lateral ventricles </li></ul><ul><li>Midline shift </li></ul><ul><li>Dilatation of ventricular system </li></ul><ul><li>Obst. to CSF flow within the system ( non-communicating) </li></ul><ul><li>Obst. over the surface of brain (communicating) </li></ul><ul><li>Secondary to brain atrophy </li></ul><ul><li>-CT with contrast </li></ul>
  9. 9. MRI of brain <ul><li>Multiplanar capability….extent of tumor. </li></ul><ul><li>esp. for post. Fossa & craniovertebral junction. </li></ul><ul><li>Disadvantage; inability to show calcification and bone details </li></ul><ul><li>long scan time </li></ul><ul><li>difficulty in monitoring critical patients </li></ul>
  10. 10. MRI Brain <ul><li>Contrast </li></ul><ul><li>Gadolinium </li></ul><ul><li>MRA severe stenosis & aneurysm </li></ul><ul><li>MRV </li></ul>
  11. 11. MRI Brain <ul><li>It is more often possible to make a specific diagnosis with MRI than CT. </li></ul><ul><li>Demyelinating plaques of MS </li></ul><ul><li>AVM </li></ul>
  12. 12. Neurosonography <ul><li>Hydrocephalus </li></ul><ul><li>Hemorrhage </li></ul><ul><li>Congenital abnormalities. </li></ul>
  13. 13. Brain Tumors <ul><li>Glioma </li></ul><ul><li>Solitary irregular mass </li></ul><ul><li>surrounded by edema </li></ul><ul><li>may compress or displace ventricle. </li></ul><ul><li>usually hypodense </li></ul><ul><li>may be hyper or mixed. </li></ul><ul><li>may calcify </li></ul><ul><li>most show partial enhancement. </li></ul><ul><li>may be ring enhancement. </li></ul><ul><li>Low in T1 , high in T2 </li></ul>
  14. 14. <ul><li>Metastases </li></ul><ul><li>may be of high or low density. </li></ul><ul><li>surrounded by edema </li></ul><ul><li>typically multiple </li></ul><ul><li>a solitary metast. could not be diff. from </li></ul><ul><li>a primary neither by CT nor by MRI </li></ul>
  15. 15. <ul><li>Meningioma </li></ul><ul><li>arise from meninges of the vault, falx & tentorium. </li></ul><ul><li>commonest sites are parasagittal region over the cerebral convexities & sphenoid ridge. </li></ul><ul><li>Slightly hyperdense on native CT </li></ul><ul><li>marked enhancement </li></ul><ul><li>Sclerosis & thickening of adjacent bone. </li></ul><ul><li>Acoustic neuroma; in the CPA near IAM. </li></ul>
  16. 16. <ul><li>Pit. Tumors: </li></ul><ul><li>microadenoma < 10mm </li></ul><ul><li>macroadenoma.> 10mm </li></ul><ul><li>endocrine active 80% </li></ul><ul><li>endocrine inactive. 20% </li></ul><ul><li>Gd is better for demost. microadenomas </li></ul>
  17. 17. <ul><li>Cerebral infarction & hemorrhage </li></ul><ul><li>Clinically similar </li></ul><ul><li>CT is the initial exam. </li></ul><ul><li>Hge….high density surrounded by edema. </li></ul><ul><li>May be SAH or intraventricular. </li></ul><ul><li>In Infarction ….CT normal initially. </li></ul><ul><li>MRI diffusion Weighted Images. </li></ul>
  18. 18. <ul><li>SAH usually due to rupture aneurysm. </li></ul><ul><li>CT is the best initial exam. </li></ul><ul><li>The large aneurysms are seen by CT. </li></ul><ul><li>MRA can show smaller aneurysms. </li></ul><ul><li>Arteriography is the best. </li></ul><ul><li>AVM may present with Hge….CT can show the AVM esp. with contrast. </li></ul><ul><li>But MRI is better even without contrast. </li></ul>
  19. 19. <ul><li>Abscess </li></ul><ul><li>Low density with ring enhancement </li></ul><ul><li>Herpes encephalitis </li></ul><ul><li>enhancing low density areas in the </li></ul><ul><li>temporal lobes. </li></ul>
  20. 20. <ul><li>Head Injury: </li></ul><ul><li>Fractures </li></ul><ul><li># more translucent </li></ul><ul><li># may branch abruptly </li></ul><ul><li># have straight or jagged edge that fit together. While venous channels have undulating irregular edges which cannot be fitted together. </li></ul><ul><li>Arterial grooves have parallel sides (more easily confused with #)..but present in known anatomical positions. </li></ul><ul><li>Suture in known anatomical positions & show regular interdigitations. Widening of a suture has the same significance as a # </li></ul><ul><li>Depressed #....dense </li></ul><ul><li>EDH can result from # through MMA groove. </li></ul>
  21. 21. CT in head injury <ul><li>CT should be done when there is: </li></ul><ul><li>-deterioration in the conscious level. </li></ul><ul><li>-worsening of neurological deficits. </li></ul><ul><li>Extracerebral lesions </li></ul><ul><li>-EDH.. biconvex. Associated with # </li></ul><ul><li>High density for 2Wks. </li></ul><ul><li>After 3-4Wks…..hypodense </li></ul><ul><li>Isodense in between. </li></ul><ul><li>-SDH …….concavoconvex </li></ul>
  22. 22. <ul><li>Fractures of the base & vault are easily </li></ul><ul><li>seen in bone window </li></ul><ul><li>Intracerbral lesions: </li></ul><ul><li>-Edema- homogenous low density. </li></ul><ul><li>-Contusions- patchy low density areas </li></ul><ul><li>-Intracerebral hematoma </li></ul><ul><li>Severe head injury can exist with no abnormal CT </li></ul>

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