Situational Questions (gawa gawa ko lang) Flashcards
Why should you set the exposure to the HIGHEST mA setting?
- This allows shortest exposure time and minimizes the change of patient movement.
- If we use the highest mA possible, we can reduce the time of exposure, thus reducing patient exposure dose, and avoid blurring in the x-ray film.
What produces radiographic contrast in an x-ray?
- Radiographic contrast is due to the differences of the density and thickness of the soft and hard tissues and other structures in our body.
- Those with high density will appear more white or radiopaque as they are more radioresistant.
- Those with low density will appear more black or grey or radiolucent as they are more radiosensitive.
- With the differential absorption of different tissues, we observe different degrees of radiopacity in an x-ray and this allows us to study a radiographic image for clinical purposes.
Do x-rays travel in all directions? And how?
- Yes.
- Because not all radiations produced are effective photons.
- Most of the radiations produced are actually scattered photons and low-energy (soft) radiations that do not serve a good purpose in producing the radiograph. They travel in all directions and may actually hit the patient and cause a blurring effect in the image by degrading the image contrast.
If your clinic doesn’t have lead barriers, what can you do as an operator to protect yourself from harmful radiations?
- Stay away for at least 6 feet or 2 meters from the x-ray machine.
- Place myself out of the path of the x-ray beam, at an angle of 90-135 degrees to the central x-ray beam.
Structures like the lamina dura is not seen on radiographs. Why is that?
- Due to the eggshell effect.
- Structure like the lamina dura, which are corticated, produces an eggshell effect in 2D radiographs due to the tangential path of photons.
- Basically, the way that x-ray photons travel to the margins of corticated structures and to the insides of the structure is different.
- The x-ray beam passing through corticated structures, tangentially touching only the curved peripheries, has more attenuation while the rest of the structure has less attenuation (meaning it’s radiolucent), which is why the lamina dura is just seen as a thin radiopaque layer, representing only its margins (peripheries).
What is the importance of the SLOB technique in clinical dentistry?
1) When surgically estimating and treating impacted teeth.
2) When doing endodontic treatments (RCTs) to estimate and localize specific pulp canals of multirooted teeth.
Why should we place the image receptor parallel to the long axis of the object?
- To avoid or minimize shape distortion.
- To prevent foreshortening and elongation in the radiographic image.
- To make sure that we get the image we need and for such reasons, we can avoid retakes, thus lowering patient exposure.
Explain how x-rays are produced.
The cathode in the x-ray tube is the source of electrons. Once there is a power supply already and the exposure button is activated, the filament in the cathode is heated up, and the electrons are accelerated from the cathode to the anode. Once these electrons hits the focal spot, the kinetic energy is converted into x-rays and heat. The useful x-ray beam exits the PID, strikes the patients, and essentially hitting the image receptor, producing the radiographic image.
In your own words, explain latent image formation.
The silver halide grains in the film emulsion are sensitive to light and x-ray photons. During x-ray exposure, these silver halide grains absorbs the energy emitted by the x-radiation and this energy is stored and remains invisible until it undergoes chemical processing (developer/fixer). Depending on the density of the subject to where the halide crystals are placed during exposure (e.g., behind soft tissue, behind an amalgam restoration), there is a varying amount of energy stored. This stored energy in the exposed film that cannot be seen is what we refer as the latent image.
Why should we use rectangular collimators instead of circular ones?
Because rectangular collimators are designed to have similar dimensions as the image receptor we use for intra-oral x-rays. With rectangular collimators, the x-ray beam directed to the patient will also be shaped rectangular, thus there are no excess radiation hitting the patient that results to unnecessary patient exposure.
With rectangular collimators, they limit the size of the x-ray beam, therefore also decreasing patient surface area that is exposed to the x-ray, and preventing scattered radiation that could cause film fogging.
Where do we base exposure time in dental radiography?
We base it from the patient’s size (larger densities = larger thickness = more exposure required) and from the anatomic area that we are interested in (incisors vs. molars; incisors are more narrower or less dense than molars, so less exposure is required).
Can we take dental radiographs in pregnant patients? Will this not affect the growing fetus / baby in the womb?
- Yes, we can take dental x-rays in pregnant patients. As long as we use the right exposure time, correct exposure dose, the reasons are justified, applied the ALARA principle and adhere to the radiation protection measures, then dental x-rays are safe for pregnant women.
- No, radiation exposure that are needed in dental radiographic examinations are thousand times smaller than the fetal dose for embryos/fetuses. Meaning, when we take dental radiographs, we will not reach the threshold required for deterministic effects on fetuses such as death and microcephaly.
How are the teeth affected with radiotherapy? Why do malformations happen after radiotherapy?
- Radiation affects the development of teeth, especially in children, where the teeth is still developing.
- When the developing tooth buds are irradiated, it brings change to the developing teeth. The radiation could cut off the nutrient (blood) supply of the teeth, it can cause change to the oral environment, and it can also retard or abort root formation.
- Due to the fact that growing teeth are still not fully specialized, they are more radiosensitive at this point. And that is when malformations happen.
How could you convince a patient to undergo a dental xray examination?
Pili ka, x-ray o bunot? 🤪
Srslyyy:
- Tell the patient how minimal the exposure dose required for dental x-rays, and that, compared to medical x-rays, it’s much more smaller.
- Give a relative comparison, na 1 airline flight causes much more radiation than a single x-ray examination.
- Explain to the px how important and crucial the x-ray exam is for the diagnosis and treatment plan, that the benefit of the resultant radiographs will be much more beneficial and that it outweighs the risk.
- Tell the px that we are going to apply the ALARA principle and that we are going to make sure that we apply the proper radiation protection measures and efforts for them to make sure that we expose them to the most minimal radiation dose possible but is still effective for dental radiographic imaging.
What kind of dental x-ray films do we use? And why do we use them?
- Fast image receptors (E/F speed).
- We use them because they require less exposure time, which means we lessen the radiation exposure that we expose the patient to. This means that with fast speed films, we reduced exposure, and without sacrificing the image quality needed for diagnostic information.
