Management of Pt Radiation Dose During Diagnostic X-ray Procedures Flashcards
A holistic approach to patient care is essential in diagnostic imaging and this begins with:
effective communication
Radiographers must limit the pt’s exposure by:
Employing appropriate radiation reduction techniques and using protective devices that minimize radiation exposure.
Three effects of good communication are:
- Reduction in anxiety and emotional stress.
- Enhances the professional image of the radiographer.
- Increases the chance for successful completion of the X-ray examination.
Pt’s must be informed of any pain, discomfort or strange sensations associated with the procedure when?
Before the procedure begins - but done overemphasize it.
An effect of poor communication can be:
If something unexpected happens, pt may move during an exposure resulting in a repeat exposure.
Pt motion can be eliminated or minimized by:
Proper body or body part immobilization.
Motion reduction techniques.
Pt's age Breathing patterns or problems general anxiety Physical or mental discomfort Excitability Fear of the exam Fear of unfavorable prognosis Mental instability
Things that voluntary motion may be attributed to.
How to eliminate voluntary motion:
Gaining cooperation of pt.
Adequate immobilization by the use of radiographic aids.
Chills Tremors Muscle spasms Pain Active withdrawl
Things that involuntary motion may be attributed to
How is involuntary motion reduced?
By the use of high mA with short exposure times.
How does lead shielding protect from radiation?
It attenuates the X-ray beam and reduces or eliminates a radiation dose.
Areas of the body that should be shielded from the X-ray beam whenever possible:
Lens of the eye
Breasts
Reproductive organs
When should gonadal shielding be used?
when these organs are in or within approximately 5 cm of a properly collimated beam.
Gonadal shielding is a secondary protective measure and never a substitute for:
an adequately collimated beam that includes only the anatomy of interest.
Female reproductive organs receive about ____ times more exposure than males for radiographic exams of the pelvic region.
three
For female patients, the use of a flat contact shield placed over reproductive organs reduces exposure by about:
50%
For male patients, primary beam exposure can be reduced as much as ____ when gonads are shielded.
90% to 95%.
When a male is in the supine position, the ___________ can be used to guide shield placement.
pubic symphysis
For females, the shield should be placed _______________ for protection of the ovaries.
about 2.5 cm (1 inch) medial to each palpable ASIS
Four basic types of gonadal shielding devices:
Flat contact shields
Shadow shields
Shaped contact shields
Clear lead shields
Flat contact shields are made of:
lead strips or lead impregnated materials 1 mm thick.
If flat contact shields are used during typical fluoro exams, where is the shield placed?
Under the patient. If the tube is above the patient, the shield is placed over the patient.
Shadow shields are made of:
radiopaque material that is suspended over the region of interest. It casts a shadow over the area to be shielded.
Shaped contact shields are made of and are shaped how?
They contain 1 mm of lead and are contoured to enclose the male reproductive organs. Not recommended for PA projections as it covers only anterior surface.
Clear lead shields
Made of transparent lead-acrylic material impregnated with about 30% lead by weight.
Lens shields for the eyes are what type of shield? (contact, shadow, shape, gonadal)
contact
Gonadal shielding minimizes the number of:
potentially harmful xray induced mutations expressed in future generations.
Specific area shielding significantly reduces exposure to those areas and should be used when ever possible to minimize:
the possibility of stochastic effects.
Standardized technique charts have become even more important because:
digital image receptors are capable of responding to a large variance in X-ray intensities exiting the patient (wide dynamic range)
With screen-film imaging, as kVp increases and mAs decreases, radiographic contrast is ____ and the amount of diagnostically useful information in the recorded image is ____.
reduced, less.
In digital imaging, changing kVp has ____ of an effect on the contrast of the digital image. So the use of higher kVp than is used with scree-film is an advocated practice.
less
Increasing kVp by ____ with the appropriate decrease in mAs reduces patient dose.
15%
Correct film processing enhances ______ and ensures _____
image quality, the film will not deteriorate over time when it is stored.
Poorly processed radiographs leads to:
repeat exams
unnecessary patient exposure
A quality control program ensures:
standardization in the processing of analog and digital images. It includes regular monitoring and maintenance of all processing and image display equipment.
Air gap technique is:
an alternative procedure to the use of a grid for reducing scatter.
Selection of exposure factors for air gap technique are comparable to those used with:
an 8:1 grid (higher than a non-grid technique)
With kVp settings of _____ or above, air gap techniques are not as effective.
- X-rays scatter at greater angles and are less likely to hit the IR at lower kVp ranges (less than 90) and air gap techniques are more useful.
Repeat analysis program is:
an attempt to record the various causes of inadequate quality on occasions when an image has to be retaken.
- Images too dark or too light because of inappropriate selection of technical exposure factors
- Incorrect pt positioning
- Incorrect centering of the radiographic beam
- Pt motion during the radiographic exposure.
- Improper collimation of the radiographic beam
- Presence of external foreign bodies
- Processing artifacts
Categories for discarded images (repeats)
- The program increases awareness among staff and student radiographers of the need to produce optimal quality recorded images.
- Radiographers generally become more careful in producing their radiographic images because they are aware that the images are being reviewed.
- When the repeat analysis program identifies problems or concerns, in-service education programs covering these specific topics may be designed for imaging personnel.
Benefits of a repeat analysis program
Analysis of repeat rates provide:
valuable information for process improvement, helps minimize pt exposures, and improves overall performance of the department.
Who assumes the responsibility for ordering a radiologic exam?
The referring physician.
Increased numbers of people in the US are undergoing diagnostic imaging procedures each year. This results in increased concern about _______________. Imaging personnel must reduce the risk to pts whenever possible by ____________.
the risks from the radiation exposure received, using methods that produce high-quality images with the least amount of radiation.
The quantity of radiation received by a pt during an imaging procedure can be specified in three ways:
Entrance skin exposure, gonadal dose, bone marrow dose. ESE is the easiest to obtain and most widely used.
Entrance skin exposure may be converted to patient skin dose by:
using well established well-documented multiplicative factors.
When measuring ESE and actual pt measurements are not available:
accurate estimates can be made and is the reason why ESE is widely used in assessing the amount of radiation received by the pt.
Most often used to measure skin dose:
TLD’s
TLD’s are attached to ___________ and exposed during the radiograph.
the skin in the middle of the clinical area of interest
Is the sensing material and respondsin a manner similar to human tissue when exposed to radiation and an accurate determination of surface dose can be made.
LiF
In fluoro, the amount of radiation a pt receives is usually estimated by:
measuring the exposure rate at tabletop and multiplying it by the fluoro time.
Skin dose:
represents the absorbed dose to the most superficial layers of the skin. The region is the epidermis and functions to protect underlying tissues and structures.
Five layers of the epidermis:
Horny, or outer layer. Translucent, or clear layer. Granular layer Prickle cell layer Germinal, or basal cell layer
Measurements and estimates of gonadal dose are important because of:
the suspected genetic effects of radiation.
For exams in the pelvis region, differences in doses exist between:
male and female pts
In diagnostic radiology, the gonadal dose is low for each individual but may have some significance in terms of:
population effects.
Genetically Significant Dose:
is the equivalent dose (EqD) to the reproductive organs, that if received by every member of the population, would produce the total genetic effect on the population as the sum of the individual doses actually received.
Genetically significant dose takes into consideration that:
some people receive radiation to their reproductive organs during a given year and others do not.
For computational purposes, the genetically significant dose considers ________ for each person examined with X-rays. It also acknowledges:
the age, sex, and expected number of children…the various types of exam and the gonadal dose per examination type.
According to the US Public Health Service, the estimated GSD for the population of the US is:
approximately .20 mSv (20mRem)
The genetic effect of the genetically significant dose are:
not detectable
Bone marrow dose may also be referred to as:
the mean marrow dose
Bone marry contains large numbers of:
stem (precursor) blood cells that could be depleted or destroyed by substantial exposure to ionizing radiation.
Hematologic effects of radiation are rarely experienced in diagnostic radiology. Radiation dose to bone marrow may be responsible for:
radiation-induced leukemia
Which diagnostic exams involve exposure to large amounts of bone marrow?
Head, upper limb girdle, ribs, thoracic vertebrae, lumbar vertebrae, sacrum, lower limb girdle
In the US, the mean marrow dose from diagnostic X-ray exams averaged over the entire population is:
1 mGt/year (100 mrad/yr)
Bone marrow dose is a concept that is used to estimate, on a population basis:
the risk of one late effect of radiation - leukemia
Fluoroscopically guided positioning:
Called FGP and is the practice of using fluoro to determine the exact location of the CR before taking a radiographic exposure.
The ASRT recognizes that the routine use of fluoro to ensure proper positioning for radiography prior to making an exposure is :
an unethical practice that increases pt dose unnecessarily and should never be used in place of appropriate skills required of the competent RT.
Studies have shown that pt ESE ______ with the use of FGP when repeat exposure is needed.
increases
Increases attention of exposure of pts to medical X-rays have brought about increased attention in our society for two reasons:
- The frequency of X-ray exams, among all age groups, is growing annually.
- Concern among public health officials is increasing regarding the risk associated with medical X-ray exposure, especially the possibility of late effects.
If the pt is to receive substantial pelvic irradiation and there is some doubt about her pregnancy status and there are no overriding medical concerns, it is recommended that:
the result of the pregnancy test be obtained prior to the xray
xray exams in which the fetus is not in or near the primary beam may be allowed, but:
they should be accompanied by pelvic shielding.
If a pregnant pt escapes detection and is irradiated:
the fetal dose is estimated.
When the form for a request for estimated fetal dose is completed:
it is conveyed to the RSO or medical physicist whose responsibility it is to determine the absorbed EqD to the embryo-fetus.
After irradiation of pregnant pt, once fetal dose is known, the stage of gestation is determined and the information is used how?
To allow the pregnancy to continue or terminate the pregnancy. Recommendations for abortions after diagnostic X-rays are rarely indicated.
Because natural incidence of congenital anomalies is about 5%,
no such effects can reasonably be considered a consequence of diagnostic X-ray doses.
Manifest damage to the newborn is unlikely at fetal doses below:
250 mGyt (25rad) although some suggest lower doses may cause mental developmental abnormalities.
Concerning a pregnant pt that was irradiated before the pregnancy was known, if the fetal dose is under 100 mGyt,
a therapeutic abortion is not indicated.
Concerning a pregnant pt that was irradiated before the pregnancy was known, if the fetal dose is above 250 mGyt,
the risk of latent injury may justify a therapeutic abortion.
Concerning a pregnant pt that was irradiated before the pregnancy was known, if the fetal dose is between 100 and 250 mGyt,
the precise time of irradiation, the emotional state of the pt, the effect an additional child would have on the family, and other social and economic factors must be considered.
The fetal dose rarely exceeds
50 mGyt (5 rad) after a series of X-ray exams.
Federal regulations for FDA certification of screening mammography facilities state that the mean dose to the glandular tissue of a 4.5 cm compressed breast used in screen-film mammography should not exceed:
3 mGyt (300 rad) per view. (Does are usually not more than 2 mGyt.
ACR recommends annual screening mammography at least:
every other year for women age 40-49 and annually for women 50 and older.
The helical pitch ratio (or just pitch) is the relationship between:
the couch movement and the X-ray beam width.
Pitch is expressed as:
a ratio.
A pitch of .5:1 results in:
overlapping of the images and a higher pt dose
A pitch of 2:1 results in:
extended images and reduced pt dose.
US Public Health Service data suggests that 10% of all X-ray exams are now CT - but CT accounts for:
70% of the pt effective dose
Two concerns relating to pt dose in CT are:
skin dose and dose distribution.
The CT xray beam is more _________ than the conventional beam.
tightly collimated.
The entrance exposure from a CT exam my be compared with the entrance exposure received during:
a routine fluoro exam.
The dose distribution resulting from a CT exam is _______ as the dose distribution resulting from routine radiography.
not the same
In radiography or fluoro, the entrance dose to the skin is greater than the exit dose. In CT:
the dose is more uniform throughout the pt because the tube rotates around the pt.
Approximate dose for head during CT imaging:
30-50 mGy (3000-5000 mrad). Varies depending on CT imaging system and exam technique used.
Approximate dose to body for CT imaging:
20-40 mGy (2000-4000 mrad) Varies depending on CT imaging system and exam technique used.
Because of the rotational nature of the exposure, a shield is not more effective than:
the collimators that exist on the scanner.
When the pitch ratio is 1:1 the spiral CT scan dose is:
comparable to conventional CT
When the pitch ratio is higher than 1:1 (e.g. 2:1), pt dose is:
reduced compared to conventional CT because less of the pt is exposed during the scan.
When the pitch ratio is less than 1:1, (.5:1) Pt dose:
increases as compared to conventional CT
Other factors in CT that affect pt dose:
pixel size, slice thickness and tube mA. The use of smaller pixel sizes for better resolution, the selection of thinner slices and the increase in mA all increase pt’s absorbed dose.
Dose parameters for CT:
CTDI, CTDI(w), CTDI(vol), Dose length product (DLP)
There is a ____________ relationship among all four CT parameters.
direct, progressive
CTDI(vol) and DLP are displayed by:
the scanner’s software
CTDI is determined by ___. An ionization chamber is:
QC. inserted into an acrylic phantom…all other holes are filled with acrylic plugs
When determining CTDI by QC, a single slice is scanned (10 cm) with technique factors equivalent to:
those used for pt studies
How is mGy measured during CTDI QC?
The ionization chamber is attached to an electrometer whose reading when multiplied by correction factors will be given in mGy.
CTDI(w)
is a weighted average of two measured CTDI values, one that is obtained in the center of the phantom and the other from the average of the 4 peripheral cavity measurements. (1cm deep at 3, 6, 9 and 12 o’clock positions.)
CTDI(vol)
is the average absorbed dose within a scanned volume.
If pitch equals 1, then CTDI(w) will equal:
CTDI(vol)
If there pitch is greater than 1, then the CTDI(vol) will be:
less than the CTDI(w)
Dose length product (DLP)
is the product of CTDI(vol) and the irradiated scan length. It is expressed in mGy-cm.
Effective Computed Tomography Dose
Using a table of scan region-specific conversion factors, generated by the European Union, and combining that with the dose information supplied by the CT software for each delivered scan sequence, the EfD value for that CT scan will be yielded.
EfD is calculated by the following equation:
EfD=DLP x EfDLP. EfD is expressed in mSv and represents a conversion factor from pt’s CT scan to the EfD
