CT Safety Flashcards
“Radiation safety” refers to:
The methods and tools used to protect patients and personnel from ionizing radiation exposure
Organizations who set and enforce radiation standards include:
ICRP NRC EPA FDA OSHA
How can x-rays cause damage to the body as it passes through?
Directly interacting with DNA bonds within cells
Producing ion pairs
Radiation can cause the most harm during what peak of pregnancy?
First trimester
Rad is equal to:
The absorption of 0.01 joules of energy per kilogram of matter
Radiation can be measured as:
Rad
Gray (1 Gy = 100 rads)
Rem
Sievert (1 Sv = 100 rem)
Radiation dose at the _____ is greater than the dose at the ______ of the body
Skin / Center
What is unique about the radiation profile of a single slice?
It is rounded and the radiation actually extends outside of the intended slice
“Radiation penumbra” refers to:
The radiation that “leaks” outside of the intended slice thickness
Why does a radiation penumbra occurs?
Imperfect collimation of the x-ray beam (not due to service problems, but due to natural CT physics)
What are some indicators of radiation dose?
CT Dose Index
MSAD
Dose-length Product
Effective Dose
CTDI did not account for what type of scans?
Helical scanning
Cone beam irradiation
Simultaneous acquisition of multiple slices in a single rotation
When would a CTDI value be inaccurate?
If adjacent slices overlapped or had gaps
Which indicator of radiation penumbra would correct the CTDI on conventional scans?
MSAD
Where do we see the radiation penumbra on MDCT slices?
Only the end slices of the volume
The DLP accounts for:
Performance of helical scans
Total number of slices
Slice thickness
What is unit used to express DLP?
mGy-cm
How can you calculate the effective dose?
Multiplying the absorbed dose by a weighting factor assigned to each organ / body region
Effective dose is an indication of the :
Overall risk to the patient from radiation
What unit is used to express the effective dose?
Sv
What scan parameters can inadvertently affect patient dose?
mAs Anatomical coverage Slice thickness (single-row detectors) Table increment Pitch
On a single-row detector, how can you achieve fewer radiation penumbras?
Thicker slices
How can you decrease dose to a patient?
Decrease mAs / anatomical coverage
Increase slice thickness / table increment / pitch
What about the image quality would be most apparent when decreasing dose to a patient?
Increased noise
What scanning techniques can be used to minimize dose to the patients without repeating scans?
Noise reduction algorithms
Iterative reconstruction
What kind of material are some of the radiation shielding devices made of?
Lead
Tungsten
Bismuth
What is the federal government limit for occupational exposure?
5 rem in a given year
Pregnant workers: < 0.05 rem/month
The cumulative dose equivalent (in rem) must not exceed:
The age of the worker (in years)
Contrast agents are helpful in clarifying anatomical findings through what kind of mechanism?
Attenuation
What components used in CT are referred to as “negative contrast” in rectal administrations?
Air and water
“Negative contrast” can improve visualization of:
Internal surface (stomach and bowel)
What are the categories of CT contrast administration?
Intravenous Oral Rectal Intrathecal Intra-articular
What can we visualize with an intravenous CT contrast administration?
Blood vessels
Vascular lesions
Abdominal organs
What can we visualize with an oral CT contrast administration?
Gastrointestinal tract
What can we visualize with a rectal CT contrast administration?
Distal gastrointestinal tract
What can we visualize with an intrathecal CT contrast administration?
Spine
What can we visualize with an intra-articular CT contrast administration?
Joints (arthrography)
What type of exams requires IV contrast agents?
CTA Brain Neck Chest Abdomen Pelvis
What are the different types of IV contrast agents?
Non-ionic (does not break down / form ions)
Ionic (breaks down into two ions)
What are typically used for injecting CT contrast media?
Single-use, disposable catheters or butterfly needles
Which vein is the vessel of choice in the cubital fossa as far as injection site goes?
Basilic vein
What are the different phases of contrast equilibrium?
Bolus
Non-equilibrium
Equilibrium
When scanning is performed later than the portal venous phase, during the equilibrium phase, many hepatic tumors become:
Isodense with the liver
What are the benefits of using a dual-head power injector?
Potential to decrease both contrast usage and radiation dose to patient
What kind of complications can occur with an extravasation?
Tissue necrosis
Swelling
Pain
How can you treat extravasations?
Elevation
Ice packs
Surgery
What are some complications to an air embolism?
(Larger) Shortness of breath Chest pain Hypotension Paralysis Seizures
How can you treat air embolism?
Position in left lateral decubitus with head angled 30-40 degrees downward
100% oxygen administration
Which type of IV contrast agents may you see more complications with?
Ionic
What are the benefits to using oral contrast agents?
Reduce the risk of misdiagnosing fluid-filled bowel
Lesion location
Lesion infiltration
What are the two basic varieties of oral contrast agents?
Iodine
Barium Sulfate
What is the difference between oral agents used in CT compared to conventional radiography?
More diluted
How can we speed up the barium sulfate contrast progress through the GI tract?
Mix it with iodinated oral agent
What are some complications to using oral agents?
Diarrhea
Abdominal cramping
What are some contraindications to barium sulfate agents?
Colon perforation Tracheosophageal fistula Obstructing lesions of the small intestine Pyloric stenosis Known sensitivity to barium sulfate
How should you scan a patient who has received intrathecal contrast?
Elevate the patient’s head
Confirm the proper density of the contrast agent
Roll patient to ensure contrast media does not separate from the CSF
What might be done prior to injection an intra-articular contrast agent?
Some joint fluid may be removed
If a patient is sedated, what kind of special monitoring device is recommended?
Pulse oximeter
A stroke results from:
Lack of blood flow to the brain
What is the normal range for oral temperature?
97-99
What is the normal range for axillary temperature?
96.5-98.5
What is the normal range for rectal temperature?
97.5-99.5
What is the normal range for pulse rates in an adult?
70-100 BPM
What is the normal range for pulse rates in an athletic adult?
45-60 BPM
What is the normal range for pulse rates in a child?
95-110 BPM
What is the normal range for pulse rates in an infant?
100-180 BPM
Blood pressure is expressed as:
Systolic over Diastolic
What does the systolic pressure indicate?
The force of ventricular contraction
What does the diastolic pressure indicate?
The lowest pressure of the ventricle between heartbeats
What are some pediatric concerns?
Portray non-threatening environment Obtain cooperation (possible sedation) Minimize dose
Pediatric protocols use lower values for:
mAs and kVps
What’s the typical dose for IV contrast?
1-2 ml per kg
Children will usually receive about ____ of the total volume of oral contrast as adults.
Half
