Other imaging modalities 2 Flashcards
What is the first line imaging for soft tissue
o Ultrasound is the first line imaging + possible biopsy if required
o MRI should be considered for further investigation
What are examples of disease that can be seen on ultrasound
o Facial lymph node disease
o Ranula
o Lipoma
o Sebaceous cyst
How do cysts typically appear on ultrasound
Cysts typically will have posterior enhancement which is a bright area behind a hypoechoic area
Also seen in pleomorphic adenomas as may have cystic content
What does CBCT consist of
- Consists of low dose multiplanar imaging
- Images are made up form isotropic voxels
How does CBCT differ from CT
o CBCT is cone shaped beam, CT is fan shaped beam
o CBCT is lower dose
o CBCT has poorer soft tissue contrast
o CBCT does not require radiographic contrast
o Patient is sat upright/standing whereas CT is lying horizontal
What are the most common reasons for CBCT
is implant planning, other reasons include for cysts, MRONJ, osteomyelitis
What imaging is done for myofascial pain
none
What imaging is done for internal derangement
o MRI is gold standard
o Disc is visualised on MRI and can determine if it is with our without reduction and which direction the disc moves in relation to the condyle
o Need to view it in the parasagittal (along the short axis of the condyle) and para-coronal (along the long axis of the condyle)
o Taken in open and closed position
What imaging is done for degenerative changes
o CBCT
How does MRI work
- Works by exciting hydrogen ions within different tissues of the body and then the magnets are turned off and the time it takes for ions to relax is what is responsible for the different densities in the images
- Two key weighted scans are T1 and T2
What is T1 MRI
fat is always white, bone and fluid is black and they are useful for looking at anatomy
What is T2 MRI
fat and fluid is white whereas bones are black
What is SPECT
- Injection with 99mTc is used
- Used to check for activity of the joint compared to the normal side
- It is very good for looking for increased activity whether that be due to a tumour, condylar hyperplasia, infection, inflammation
- It has high sensitivity & low specificity
- Only used as a screening method
What is sensitivity
o Sensitivity is the proportion of diseased people who are correctly identified as positive and it means how good the test is at correctly identifying those who had the disease
What is specificity
o Specificity of the test is the proportion of non-diseased people who are correctly identified as negative by the test. It means how good it was at correctly identifying the people who did not have disease
What is the difference between MRI and CT
