Minimizing exposure to patients Flashcards
What is the short form for equivalent dose?
EqD
What is the short fom for occupational and non occupational effective dose?
EfD
What is EqD?
The effect of the type of the radiation
What is EfD?
A measure that comes back on our TLD’s that incorporates both the effect of the type of radiation used and the variabiility in radiosensitiving of the organ or body part irradiated
When was the ALARA principle put forth and by whom?
1954 by the NCRP (national committee of radiation protection)
Define risk in the medical industry with reference to the radiation scienes:
The possibility of inducing a radiogenetic cancer or genetic defect after irradiation
Who has the responsibility for ordering a radiologic examination?
The reffering physician
Read through the benefits of effective communication
- Encourages reduction in anxiety and emotional stress
- Enhances the professional image of radiographer
- Increases likelyhood for cooperation and successful examination
- Reduces radiographic proceedures
Read through when communication between radiographer and patient is effective
- When verbal and nonverbbal messages are understood as intented
- Words and actions demonstrate understanding and respect for human dignitiy and individuality
- Patient protection during procedure are given with clear, consise instructions
What are the types of patient motion?
- Voluntary
- Involuntary
Read through the radiographic apparatus’ that can reduce dose
- SID
- PA positioning
- Collimation devices
- Protective filters
- Grids
- Protective sheilding
- Optimum processing
- IR sensitivity
True or false?
Larger SID is better for dose.
True
What is the degree of inaccuracy that distance (SID) indicators can be off?
2%
What is the degree of inaccuracy that centering indicators can be off?
1%
What is the minimal source to skin distance for mobile radiography?
Min SSD of 30 cm/12 inches
What is the general SSD used for mobile radiography?
100-120
Why do we position PA when we can?
- Reduction of photons hitting gonads, breast tissue and the thyroid
Why do we not always postion PA?
- Not always practical
- OID (magnification)
- Suspected fracture
Do flat panel detectors have PBL?
yes
Check to see if this is correct
What is the purpose of x ray beam limitation devices?
- Limits the quantity of body tissue irradiated
- Reduces the amount of scattered radiations (protects unecessary exposure to other tissues not under examination)
- Improves overall image quality
What are the types of x-ray beam limitation devices?
- Light-localizing variable aperture rectangular collimator
- Aperture diphragms
- Cones
- Cylinders
What is the purpose of PBL?
So that the primary x ray beam will be no larger than the size of the IR being used for the examination
What is light beam congruency?
The light beam is coming in perpendicular to the actual x ray beam
True or false?
Light localizing variable aperture rectangular collimators allow for automatic collimation using the PBL feature.
True
What is the purpose of radiographic beam filtration?
To reduce low E photons that have no diagnostic value so that the patients absorbed dose is reduced
What are the types of filtration?
- Inherent
- Added
=total
What is the most widely selected material for filters in general radiography?
Aluminum
Why is aluminum the most widely selcted filter in general radiography?
It effectively removes low energy x rays from a polyenergetic beam without severely decreasing the x ray beam intensity
How is HVL expressed?
By mm of aluminum
What is Half-value layer?
The thickness of a designated absorber required to decrease the intensity of the primary beam by 50% of its initial value
What is the purpose of a HVL test?
To measure the beam quality or effective E of the x-ray beam at a given kVp and determines whether the protective filtration in the tube is accurate
What filters are commonly used in mammography?
- Molybdenum
- Rhodium
Why do we select molybdenum or rhodium for mammography examinations?
Since they facilitate adequate contrast by allowing a particular range or window of energies from the x ray spectrum to emerge from the x ray tube to the target
What can compensating filters be made of?
- Aluminum
- Lead-acrylic, ect.
What is the purpose of compensating filters?
To partially attenuate x rays that are directed toward the thinner/less dense area while permitting more radiation to strike the thicker/denser area.
What are the types of compensating filters?
- Wedge filter
- Trough
- Bilateral wedge filter
- Boomerang
What is the purpose of radiographic grids?
To absorb scatter
If the kVp is below 90 kVp, what grid ratio should be used?
8:1
If the kVp is above 90, what grid ratio should be used?
Anything above 8:1
What is grid cut off?
A decrease in the number of transmitted photons that reach the image receptor because of some misalignment of the grid
During the yearly QC check for grid cut off, what are they checking?
If detent is centered to the center of the grid
Which areas of the body should be selectively shielded whenever possible?
- Gonads
- Thyroid
- Breast tissue
- Lens of the eye
What is the minimal thickness allowed for sheilding?
.25mm
What is the minimal defective area for general protective lead PPE?
Less than 670mm^2
What is the purpose of diagnostic type protective tube housing?
To protect the patient and imaging personnel from off focus, or leakage radiation by restricting the emission of x rays to the area of the useful or primary beam
When the x ray machine is operated at its highest techniques what is the minimal amount of leakage radiation allowed one meter away from the tube housing?
1mGy/hr (100mR/hr)
True or false?
Patient repeats have decreased with the use of DR.
True
What are the qualities of a high quality image?
- Sufficient brightness to display anatomical structures
- An appropriate level of SC to differentiate amoung the anatomical structures
- Maximum amount of SR
- Minimal amount of distortion
True or false?
We should use AEC whenever possible.
True
What is the purpose of having technique charts?
For usage when AEC is not being used
What are Diagnostic Reference Levels?
The amount of radiation used to get a good image (a reference level)
How are DRL’s tested?
By measurements of dose on phantoms
True or false?
Increasing the sensitivity of the IR increases the dose.
False; decreasing sensitivity increases dose
True or false?
A harder x ray beam+Higher average energy beam=Less soft/low energy photons.
True
The higher the HVL, the higher the quality of the beam.
True
True or false?
The image intensifier in floroscopy should be maintainted as close as practical to reduce the patients entrance exposure rate.
True
Yes
For stationary fluoroscopes, what is the minimal distance that the source should be from the patient?
No less than 38 cm/15 inches
For mobile fluoroscopes, what is the minimal distance that the image intensifier should be from the patient? Why?
-No less than 30cm/12 inches
-Should be as short as possible to reduce enterance dose and OID
What is the kVp range for adults?
75-110 kVp depending on body area
What is the kVp range for pediatrics?
Up to 25% of adult kVp
What is the minimal HVL acceptable for kVp ranges from 80-100 kVp in fluoroscopy?
3-4.5mm of Al
True or false?
The larger the imaging mode, the more magnification and patient dose.
False; The SMALLER the imaging mode, the more magnification and patient dose.
Does itermittent/pulsed flouroscopy decrease patient dose?
Yes
Epecially in long proceedures
True or false?
Every 7 minutes of fluoscopy time, an alarm will sound.
False, every 5 minutes of fluoro time
What type of fluoroscopic exposure control switch is used?
Dead man type
Can we use collimation in fluroscopy?
Yes
What is on either end of a mobile C arm fluoroscopy unit?
- Image intensifier
- X ray tube
What are the most common usages for the mobile C arm fluoroscopy machine?
In the operating room for;
1. Orthopedic procedures
2. Cardiac imaging
3. Interventional procedures
What is the minimal source to end distance required for mobile fluoroscopy machines?
Minimum of 30 cm
Where is the prefered position of the c-arm in relation to the patient? Why?
-Under the patient
-Because scatter radiation is less intense and personnel dose is reduced (back scatter is more intense)
What is ESE
The enterance skin exposure
-It is the measurement of radiation output at the point of skin entry for; common x ray exams, including conventional radiography and fluoroscopy and should not be exceeded
What are the units for ESE
C/Kg or mR or mGy
How often should ESE measuremetns be preformed?
- Semi annually OR
- Each time th radiographic system is repaired or serviced
How is ESE measured?
- Using a phantom and a 102cm SID, place a dosimeter on top of a specific body part and expose using a technique that is routinely used.
- Record exposure on dosimeter
- The recorded exposure must be less than or equal to the DRL for that specific procedure…..or use ESE equation
Tells us how much was absorbed at skin level
What does ABC stand for?
Automatic brightness control
What is better; having the tube under the table or over the table? Why?
Having the tube under the table;
1. Scatter travels towards the ground
2. Less dose to operator
3. Generally hitting the back first
What is the patients position and projection?
AP projection; supine on the table
What is the patients position and projection?
PA projection; supine on the table
True or false
The smaller the imaging mode:
1. More Magnification
2. More Patient Dose
True
What is pulse mode?
Rapid on and off of the x-ray exposure
Why is there a cylinder at the end of the x ray tube in floro machines?
To stop the tube from reaching less than a 30 cm distance
If the Diagnostic Reference Levels (DRLs) are higher than the ESD for specific positions, what does that mean
- Not enough fitration
- Techniques too high
How do you calculate ESE?
ESE = mR x (SCD/SOD)^2
What does SCD stand for?
SCD = source to chamber distance (dosimeter)
What is the pupose of the ESE equation?
-To calculate what the value would be at different heights
-Calculated value < or = Diagnostic Reference Values (DRL’s)
Why do we position the dosimiter 15cm off the table during ESE measurements?
-To reduce back scatter to get an accurate reading
What is mR meausring in the ESE equation?
What the dosimeter sees
How do you find source to chamber distance?
SID-distance from IR to object-distance of dosimeter above table
Do ESE calculation
DO IT BC HES GONNA ASK
