Principles of Imaging 2 Flashcards
What is the radiation absorbed dose and what is its unit?
Radiation absorbed dose Relates to the amount of energy per unit mass of tissue
Gy = J/Kg
1 Gy = 100 RAD
What is equivalent dose? What is its unit?
Relates to the type of radiation
1 Sv = 100 REM
Wr X-rays = 1
Wr α-rays= 20
H = WR x D
What is effective dose and what is its unit?
Relates to parts of thebody
Converting all doses to equivalent whole body dose
Sv
E = H x Wt
Why is effective dose necessary to understand?
Some parts of the body are more sensitive to radiation than others
Why is it harmful for medical professional to stay in the same room as medical imaging?
The frequency of taking X-rays make it harmful to stay in the same room as the patient during the X-rays
Why are younger people more likely to develop cancer from ionizing radiation?
Average solid tumour takes 15 to 20 years to develop
Ionizing radiation has more of an impact on dividing cells
Which cells are most sensitive to radiation?
Cells that are undifferentiated
Cells with a high mitotic rate
Cells with a long mitotic future
What are the principles for justifying use of X-rays?
Radiographic images can only be taken after a thorough clinical examination and collecting a medical/dental history
There should be a net benefit for using X-rays
If there are previous radiographs they should be used before taking more
Any radiographic image taken should add to information that is already available
Patient should be able to cope with the procedure
What is the limitation principle?
Radiation dose should be kept As Low As Diagnostically Acceptable and As Low As Reasonably Achievable
Field of view should be limited to the region of interest
Use of fast image detectors and collimation
Avoid retakes
Use the right technique / imaging modality
What is the optimization principle?
Optimal images should be taken
Best imaging modality should be used
What dose of radiation can result in tissue damage?
Above 100 mGy and anything above 250 mGy increases risk of malignancy by 1%
What are the possible early reactions to radiation single doses above 100 mGy?
Skin erythema or mucositis
What are the possible delayed onset reactions to single doses above 100 mGy?
Osteoradionecrosis is a possible result
Hyposalivation
Cataract
Erythema
Fibrosis
Haematopoetic reactions/changes
Why is it impossible to get deterministic effects of radiation exposure during dental x-rays?
Doses are far far lower than 100mGy
What are stochastic effects of radiation exposure?
Probabilistic effects such as radiation induced cancer and genetic defects
