1. CT v. MRI Part 1

2. Back 2 Basics ▪Two types of Interactions ▸ Ionization ▸ Excitation

3. Ionization ▪Caused by adding or subtracting electrons from an atom ▪In radiology, normally subtracted electrons ▪Most radiology modalities require ionizat ion ▸ Compton effect - CT ▸ Photoelectric effect – Radiology ▪Permanent changes to the atom ▪May manifest as abnormalities

4. Excitation ▪Caused by adding energy to the atom ▪Most common side-effect is heat ▪If stimulation stops before causing damage; there is no long term effect or damage ▪MRI is uses excitation to generate images

5. Advantages of CT ▪Low cost ▪No contraindicated patients ▸ (except for contrast) ▪Fast ▪In some body systems fewer motion artifacts

6. Advantages of MRI ▪Multi-planar capability ▸ Coronal, sagittal, and oblique ▪Vascular info without contrast ▪No bone artifacts ▪Some functional information is available

7. Disadvantages ▪CT ▸ Requires radiation ▪MRI ▸ Some patients are completely contraindicated

8. Neurologic Anatomy ▪Brain ▸ Cerebrum, cerebellum, and brain stem ▪Spine ▸ Bony anatomy and cord anatomy

9. CT uses in Neuro Imaging ▪Acute bleeds ▸ Traumatic v. hemmorhagic ▪Fractures ▪Bony erosion

10. MRI uses in Neuro Imaging ▸ Tumors ▸ Infections ▸ Non-specific events ▸ Diseases and syndromes

11. Stroke ▪Initial exam ▸ CT eliminates hemmorhagic CVA ▪MRI is good for accurate assessment ▸ Diffusion MR - extent of damage

13. Bleeds ▪SAH ▪SDH ▪Epidural ▪Intracerebral

20. Metastatic disease ▪CT ▸ Can be difficult to see ▪MRI ▸ Proper sequencing may affect diagnostic ability

26. Spine Mets ▪Often called the only emergent MRI ▪Tumors that metastasize to the bone ▸ Prostate ▸ Breast

29. Acoustic Neuroma ▪CT ▸ Relies on bony erosion ▸ Can be difficult due to artifacts ▪MRI ▸ Multi-planar ▸ No artifacts ▸ Can utilize contrast

32. Pediatric Glioma ▪CT ▸ Difficult visualization ▪MRI ▸ Differentiate between tumor and edema

38. Multiple Sclerosis (MS) ▪CT ▸ Limited ▪MRI ▸ Good visualization

41. Syrinx ▪CT ▸ Limited by the axial plane ▪MRI ▸ Direct sagittals ▸ Find underlying cause Arnold Chiari Syndrome

44. Neurofibroma ▪CT ▸ Limited by plane and artifacts ▪MRI ▸ Direct imaging ▸ Improves with contrast

47. Cervical Spine Fractures ▪CT ▸ Good bony information ▪MRI ▸ Soft tissue info and cord damage

50. Fractures ▪Facial ▸ Tripod ▸ Blow-out ▪Cranial ▸ Depressed

54. Aneurysm ▪CT ▸ Requires contrast ▸ Decreased resolution with reconstructions ▪MRI ▸ No contrast required ▸ Multi-planar acquistion

58. Herniated Nucleus Pulposa (HNP) ▪CT ▸ Depends on patient and location ▪MRI ▸ Direct sagittal ▸ Good post evaluation

61. Conclusion ▪Both MR and CT have a place in the modern radiology department. The key is the proper and accurate use of the correct modality.