Unit 5 (Protection of the Patient during Diagnostic X-Ray Procedures)
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Name two aspects of effective communication:
- verbal messages
- body language
Name two types of patient motion (with example):
- voluntary (breathing)
- involuntary (heart beating)
Name three types of beam limitation devices:
- aperture diaphragm
Name four types of cones:
- Flared metal tubes and straight cylinders
- Extension cylinders
- Light-localizing variable-aperture rectangular collimators
- Beam-defining cones used in dental radiography
Name three types of Collimators:
What is the main purpose of filtration:
to lower patient dose by absorbing most of the lower-energy photons
As filtration increases, dose to the patient increases or decreases?
Name two types of filtration:
- Inherent filtration
- added filtration
Name the three three parts of inherent filtration:
- the glass envelope encasing the x-ray tube
- the insulating oil surrounding the tube
- the glass window in the tube housing
What is added filtration?
sheets of aluminun (or equivalent) of appropriate thickness located outside the tube housing above the collimator shutters.
How do you get the Total Filtration?
Inherent filtration + Added Filtration
For an x-ray procedure operating at 70 kVp or higher, what lead (Pb) equivalent is necessary?
What aluminum equivalency is provided by the silver on the mirror?
A structure or device made of certain materials such as concrete, lead, or lead-impregnated material that will adequately attenuate ionizing radiation
In the use of gonadal shielding, what are the dose reduction percentages for males and females?
How should the gonadal shielding device be placed on a male?
inferiorly to the symphysis pubis (to cover gonadal region) can be used as a guide when patient is supine
How should the gonadal shielding device be placed on a female?
1 inch medial to each palpable anterior iliac spine
Name four types of gonadal shielding devices:
- flat contact shields
- shadow shields
- shaped contact shields
- clear lead shields
Shielding used to be able to selectively shield radiosensitive organs and tissues other than the reproductive organs (and an example)
Specific Area Shielding (juvenile scoliosis examinations)
To penetrate the area of interest and obtain adequate density and contrast, what must be selected appropriately?
If AEC is not available, what can help to decrease repeats?
What balance of technical factors will reduce the dose to the patient?
high kVp and low mAs
What can help monitor/maintain all imaging equipment to assure proper images are being produced?
Good Quality Control Programs
Name some examples of reasons for repeat exposures (7):
- improper technical factors
- incorrect positioning
- incorrect centering of the beam
- patient motion
- improper collimation
- presence of external bodies
- processing artifacts (analog or digital)
What program increases radiographers' awareness and care to produce optimal quality images because they know they are being reviewed:
What increases contrast by not allowing scatter to reach the IR due to increased OIDS?
Does the Air-Gap Technique increase or decrease patient dose, and why?
- because you have to increase technical factors to compensate
Does increased Screen Speed (RS) increase or decrease patient dose?
Do rare earth intensifying screens emit more or less light?
Do rare earth intensifying screens have a higher or lower conversion factor?
What is the purpose of using a grid?
to improve image quality by reducing scatter reaching the IR
What is the grid conversion factor formula?
- mAs1 over mAs2 = GCF1 over GCF2
- mAs1 GCF1
- ____ = _____mAx2 GCF2
What is the difference in exposure in moving from a 5:1 grid to a 16:1 grid?
the exposure triples
Name some classic non-essential x-ray exam situations (6):
- standard CXR for hospital admission
- standard pre-op CXR
- CXR for pre-employment
- CXR as part of routine check-up
- CXR for TB check
- Whole Body multislice spiral CT screening
Four ways to measure patient exposure:
- Entrance Skin Exposure (ESE)
- Skin Dose
- Gonadal Dose
- Bone Marrow Dose
Which way of measuring patient exposure is often used due to the simplicity of calculating it and its lack of taking many factors into account?
Entrance Skin Exposure (ESE)
What is the formula for intensity as it pertains to Entrance Skin Exposure (ESE)?
- I1 (mAs1)(kVp1)2_= ___________
- I2 (mAs2)(kVp2)2
What represents the absorbed dose to the most superficial layer of the skin?
How can Skin Dose be obtained?
with the use of Thermoluminescent Dosimeters taped directly on skin where dose is needing to be read (delayed reading)
When do Gonadal Doses become more significant?
when a low gonadal dose is applied to an entire population
What puts out the most bone marrow?
What is the Bone Marrow Dose?
the average radiation dose to the entire active bone marrow
In fluoroscopic procedures, what does using an image intensifier do to patient dose?
halves it, by increasing image brightness
With the Image Intensifier, a fluoroscopic image increases brightness by how many times that of the original?
For Fluoroscopic Procedures, what technical factors should be used for adults? for children?
- 75-110 kVp
- approximately 25% less for children
For Fluoroscopic Procedures, what SID should be used for stationary procedures? For mobile procedures?
- stationary: 15in (38cm)
- mobile: 12in (30cm)
In fluoroscopy, with the Image Intensifier, how much aluminum equivalent is preferred and how much is required?
- preferred: 3 mm total aluminum equivalent
- required: 2 mm total aluminum equivalent
In fluoroscopy, for the Half Value Layer, what aluminum equivalency is standard and what peak kV ranges are there?
- 3-4mm aluminum
- kV ranges from 80-100
In fluoroscopy, when does the cumulative timing devise activate, sounding audible alerts?
after 5 minutes
What type of Fluoroscopic exposure control switch must be used?
What are the federal standards for Entrance Skin Exposure of intensified fluoroscopic units?
a maximum of 10 R per minute
When an image is stored from the last time that the fluoroscopic foot switch was depressed:
When the x-ray beam is turned off while the image is being scanned, thereby decreasing patient dose, and then back on for the next image:
Pulsed Progressive system
What is a name for some high-dose procedures like cath-lab, and neurology studies involving long exposure rates?
What procedure may have the most exposure from cine?
What is an operating mode for new technology that produces substantially higher exposure rates for better visualization of smaller and lower contrast objects that do not usually appear during standard fluoroscopy?
High-Level-Control Interventional Procedures (HLCF)
How often is it recommended that women receive breast exams?
- every other year from age 40-49
- yearly for age 50 and older
In a spiral CT, if pitch increases, does dose increase or decrease?
Three ways to decrease dose in a spiral CT:
- decrease noise by increasing mA
- smaller pixel size (increased resolution)
- thinner slices
In CT, dose is proportional to the square of the:
SNR (Signal to Noise Ratio)
What change of developing radiation induced leukemia or thyroid cancer does a child have as compared to an adult?
chance is doubled
In general, how do technical factors need to be adjusted from an adult to a child?
- decrease kVp setting by 25%
- (decrease in mA should also be considered)
What are two ways to reduce pediatric motion?
- increase mA with a decrease in time
In pediatrics, when does gonadal shielding cause a significant reduction in dose?
if the collimation is within 2 cm of the gonadal region
Name three ways to determine possibility of patient pregnancy:
- Ask if the patient is pregnant
- Determine last menstrual period (LMP)
- Result of pregnancy test
When should elective exams be performed when there is a possibility of pregnancy?
during the first few days after onset of menses
Who should perform calculations necessary to determine fetal exposure?
What dose to newborns is very unlikely to cause damage:
When is the risk of malformations significantly increased when x-raying a pregnant patient?
when exposure is increased above control levels above 15 rad
NCRP considers __________ to be negligible with other risks of pregnancy?
5 rads or less
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