Advanced Imaging Flashcards
What shaped beam in used in CT imaging?
Fan-shaped beams that are detected by gas or crystals
What type of images does CT produce?
A series of ‘slices’ of the patient
What is windowing?
Digital manipulation of tissue contrast
How does voltage and current different from CT to CBCT?
Conventional - tube current is 200Ma and voltage 120Kv
CBCB - Voltage 120kV but current 5Ma
What is the significance of CBCT Ma being lower?
Reduces radiation dose and alters image contrast
Reduced tube current doesn’t permit contrast difference of soft tissues - only hard tissues can be seen
What are the indications for CT?
Reached the end of what plain film can tell you
Need 3D imaging
Bony pathology - more imaging for diagnostic or tx planning purpose
Examples of indications for CT?
Impacted teeth Root resorption Planning implant Evaluation of large lesions Complex facial trauma
What are contrast techniques?
Compounds introduced into the body that artificially alter the contrast of the issue
Most common type of x-ray contrast?
Iodine - radiopaque
Some pt have allergic reactions - always check
Examples of contrast technique imaging?
Sialography, TMJ arthrography, angiography
What is sialography?
Introduction of contrast into the ductal system of parotid or submandibular salivary gland
Indications for sialography?
Hx suggestive of obstruction
Contraindications for sialography?
Acute salivary gland infection
Allergy to iodine
Discrete salivary gland swelling - other techniques more informative
What is TMJ arthography?
Introduction of contrast into inferior joint space of TMJ - determine disc position and to detect perforation/ adhesion
What is angiography?
Involves injection of contrast directly into blood vessel via catheter
Indications for angiography?
Show vascular anatomy
Investigation arteriovenous malformations
Embolise vascular lesions
What is MRI?
Placing pt inside magnetic field and pulsing radio waves into pt - emitted radio waves converted into image of a space through the body
Is ionising radiation involved in MRI?
No
Why is MRI better than CT?
Better soft tissue detail
Due to proton density difference between soft tissues
Advantages of MRI?
Provide superior soft tissue detail
Excellent inter cranial disease
Used to directly image the disc position within TMJ
What are the disadvantages of MRI?
Contraindicated in pt w/ pacemaker
Scanner noise and claustrophobic
Imagining take 20-30 mins
What is ultrasound?
Uses high frequency sound waves from transducer held against skin - sound reflect by tissue interfaces back - converted electrical signal
Benefits of ultrasound?
Non-invasive, safe
Cheaper MRI/CT
Uses of ultrasound?
Assessment of superficial soft tissues
Advantages of ultrasound?
No ionising radiation
Real-time imaging
Assess vascularity
Disadvantages of ultrasound?
Can’t image through bone or air
Intensity of the reflection decreases w/ depth
What is nuclear imaging?
Injection of radioactive isotope which emits gamma rays
Usually bound to another pharmaceutical - high affinity for tissue of interest
Indications for nuclear imaging?
Detection of bony metastases Investigation of salivary gland function Condyle hyperplasia Evaluation of bone grafts Thyroid investigations
What is positron emission tomography - PET scan?
Functional and anatomical imaging
Pt receive intravenous glucose which is labelled
Indications for PET scan?
Cancer staging
Re-staging after chemo
If MRI is contraindication what is fall-back technique?
Contrast-enhanced CT
What should be used for dents-alveolar pathology and implant planning?
CBCT
