Chat 5 Flashcards
absorption
Energy of the beam is transferred to the material through which it passes
Genetic Effect of radiation
If defective DNA is contained in reproductive cell, then the defect may be passed along to further generations of organisms
**only occur in reproductive cells
Radiation effects on cytoplasm
- Increased permeability or rupture of membranes
- Nonfunctional organelles such as lysosomes, endoplasmic reticulum, or mitochondria
- Inactivation of enzymes
- Coagulation of the cytoplasmic fluid
Radiation effects on then nucleus
- Damage in the nucleus often affects the chromosomes, which contain DNA.
- Radiation my alter the base sequence of the DNA molecule and make it defective.
- Defective DNA may lead to the disruption of the mechanisms for cell division (mitosis).
- Cell division may be delayed or the reproductive capacity of the cells may be lost. Errors that are permanently incorporated into the DNA are passed on to future generations of the affected cells as mutations.
Factors that make cells more sensitive to radiation
- A high mitotic rate (it undergoes frequent cell division)
- A long mitotic history ( it undergoes many divisions over time)
- A primitive or immature nature (it must undergo further growth or development)
- An undifferentiated nature (It is not highly specialized in function)
What is the cell that is most sensitive to radiation? Why?
Small Lymphocyte
Highly specialized cell that is part of the immune system.. It will not divide once it is mature
Effects of radiation immediately?
Do not show up immediately due to latent period
latent period
Time from exposure to radiation and the signs and symptoms of biologic damage.
What affects how long the latent period will be
May be as short as a few hours or as long as 20 years or more
-depends on total dose of radiation received and the amount of time it took to receive the dose
List the Most Sensitive Cells to Least Sensitive Cells
1. Small Lymphocyte Bone Marrow Reproductive cells Intestinal Mucosa 2. Skin Lens of the eye Oral mucosa 3. Connective Tissue Small blood vessels Growing bone and cartilage 4. Mature bone and cartilage Salivary gland Thyroid gland Kidney Liver 5. Muscle Nerve
Cumulative effects of radiation
- From repeated radiation exposure
- Radiation itself does not accumulate in tissues, but some of the unrepaired damage might.
Cumulative effects of Radiation on the Lens of eye produces
Cataracts
Cumulative effects of radiation on the bone marrow
leukemia
Cumulative effects of radiation on the salivary gland
Cancer
Cumulative effects of radiation on the thyroid gland
Cancer
Cumulative effects of radiation on the Skin
Cancer
Cumulative effects of radiation on the Gonads
Genetic Abnormalities
Units for exposure to radiation
SI Units- Coulombs per kilogram
Old Term- Roentgen (common)
Unit for absorbed dose by the tissues
gray (Gy)
Critical Organs
Organs when exposed to radiation and damaged- the quality of an individuals life declines
Skin
- first tissue exposed to radiation
- response to radiation is reddening or erythema
- increases risk of skin cancer
- does to the skin is substantially reduced with F speed Film and rectangular collimation
Lens of the eye
- may produce cataracts
- more susceptible to radiation in children
- no longer considered a critical organ
Thyroid Gland
- resistant to radiation in adults
- more susceptible to radiation in children
- Thyroid collar reduce risk by half
Leukemia
- malignant changes in marrow may result in leukemia
- Marrow is found in the jaws, skull, and C-spine
- About 13% of the total bone marrow lies in the head and neck areas
Salivary Glands
- moderately sensitive to radiation
- association has been shown between tumors in the salivary glands and people who have received full-mouth radiographs before 20
ALARA Concept
As Low As Reasonably Achievable
Receptor Speed
1) Film- fastest possible speed should be used for periapicals and bitewings
2) E speed Film- no long produced; reduced exposure by at leasts 40% when compared to D speed
3) F speed film- reduces exposure by approximately 20% compared w/E speed film for a reduction of approx. 60% compared w/D speed film
4) Digital imaging receptors require less exposure than F speed
5) Charge-Coupled Device (CCD)- requires about 1/10 of radiation of D speed film
Radiation Protection for the Patient
Receptor Speed Selection Criteria Kilovoltage Filtration Beam Collimation Cylinders Technique Proper Chemical Processing Protection
Selection Criteria
-patients history and clinical examination rather than prescribing images routinely or according to arbitrary time tables
Kilovoltage
1) Low Kilovoltage result in higher patient doses, primarily to the skin
2) 60-90 kVp; common 70 kVp
Filtration
Filtration removes the low energy X-rays from the beam
1) Units operating at 70 kVp or more should have filtration equivalent to 2.5 mm of aluminum
2) Units operating at less than 70 kVp should have the equivalent of 1.5 mm aluminum
Beam Collimation
1) The X-ray beam should be collimated so that is no more than 7cm in diameter at the patients face.
2) Rectangular collimation can result in a dose reduction of 50% to 90%`
Cylinders
1) Open-ended circular or rectangular lead-lined cylinders are preferred for directing the x-ray beam.
2) A long cylinder will reduce the exposure to the patient more than short cylinder
3) Plastic cones are Not recommended and are illegal in some states due to scatter radiation
Technique
1) receptor-holding device is recommended
2) Retakes should be kept to a minimum
Protection
1) Thyroid collars should be used on all patients for intramural imaging except when it interferes w/the examination
2) Leaded apron may not be necessary if technique is good
Radiation protection for the operator
1) Operator stands behind appropriate barrier while exposing images.
2) Barrier should have window or other means of monitoring the patient
3) If no barrier, the operator should stand 6 feet away in an area that lies between 90 degrees and 135 degrees
4) Dental personnel should never hold image receptors for patients. If assistance is necessary, as a family member or guardian for help
5) Operator should never hold the tube head for stability, and if the equipment is unstable-it should not be used until it is professionally prepared.
6) Operatory that contains X-ray unit should be constructed so that it protects the people in the surrounding areas
Prescribing images
The decision to obtain dental images for patients and the number or types of images to be obtained are to be determined by licensed dentists
-need to obtain patient history; clinical exam
