ct v. mri part 1. back 2 basics ▪two types of interactions ▸ ionization ▸ excitation
TRANSCRIPT
CT v. MRI
Part 1
Back 2 Basics
▪Two types of Interactions▸Ionization▸Excitation
Ionization
▪Caused by adding or subtracting electrons from an atom▪In radiology, normally subtracted electrons
▪Most radiology modalities require ionization▸Compton effect - CT▸Photoelectric effect – Radiology
▪Permanent changes to the atom▪May manifest as abnormalities
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
Advantages of CT
▪Low cost
▪No contraindicated patients ▸(except for contrast)
▪Fast
▪In some body systems fewer motion artifacts
Advantages of MRI
▪Multi-planar capability▸Coronal, sagittal, and oblique
▪Vascular info without contrast
▪No bone artifacts
▪Some functional information is available
Disadvantages
▪CT▸Requires radiation
▪MRI▸Some patients are completely contraindicated
Neurologic Anatomy
▪Brain▸Cerebrum, cerebellum, and brain stem
▪Spine▸Bony anatomy and cord anatomy
CT uses in Neuro Imaging
▪Acute bleeds▸Traumatic v. hemmorhagic
▪Fractures
▪Bony erosion
MRI uses in Neuro Imaging
▸Tumors▸Infections▸Non-specific events▸Diseases and syndromes
Stroke
▪Initial exam▸CT eliminates hemmorhagic CVA
▪MRI is good for accurate assessment▸Diffusion MR - extent of damage
Bleeds
▪SAH
▪SDH
▪Epidural
▪Intracerebral
Metastatic disease
▪CT▸Can be difficult to see
▪MRI▸Proper sequencing may affect diagnostic ability
Spine Mets
▪Often called the only emergent MRI
▪Tumors that metastasize to the bone▸Prostate▸Breast
Acoustic Neuroma
▪CT▸Relies on bony erosion▸Can be difficult due to artifacts
▪MRI▸Multi-planar▸No artifacts▸Can utilize contrast
Pediatric Glioma
▪CT▸Difficult visualization
▪MRI▸Differentiate between tumor and edema
Multiple Sclerosis (MS)
▪CT▸Limited
▪MRI▸Good visualization
Syrinx
▪CT▸Limited by the axial plane
▪MRI▸Direct sagittals▸Find underlying cause
Arnold Chiari Syndrome
Neurofibroma
▪CT▸Limited by plane and artifacts
▪MRI▸Direct imaging▸Improves with contrast
Cervical Spine Fractures
▪CT▸Good bony information
▪MRI▸Soft tissue info and cord damage
Fractures
▪Facial▸Tripod▸Blow-out
▪Cranial▸Depressed
Aneurysm
▪CT▸Requires contrast▸Decreased resolution with reconstructions
▪MRI▸No contrast required▸Multi-planar acquistion
Herniated Nucleus Pulposa (HNP)
▪CT▸Depends on patient and location
▪MRI▸Direct sagittal▸Good post evaluation
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.