Diagnostic Imaging Flashcards
What are the modalities that use ionizing radiation?
- Radiograph
- CT
- Fluoroscopy
- Angiography
What are the modalities that do NOT use ionizing radiation?
- Ultrasound
- MRI
Bergoine and Tribondeau’s law
-What are the characteristics of tissues that have increased radio-sensitivity?
- Cells are undifferentiated
- Greater proliferative capacity
- Divide more rapidly
What are the adverse effects of ionizing radiation?
- Carcinogenesis-leukemia, thyroid, breast, lung, skin
- Genetic consequences-gonadal irradiation
What are some clinical considerations/contraindications of ionizing radiation?
- Previous allergy to contrast
- Renal patients
- Pregnant patients (days 16-45 are critical)
- Children
What medication is contraindicated with ionizing radiation and why?
Metformin-beware of the lactic acidosis
What is the point of contrast?
Increases difference in density between anatomic structures
-3 ways to administer-PO, IV, PR
What is used for GI contrast?
GI contrast-Barium and gastrograffin
What is used for IV contrast?
IV contrast-Iodine based
What is used for MRI contrast?
MRI contrast-Gadolinium
Contrast reactions
- Hypersensitivity rxns
- Chemotoxic rxns
- Vasovagal rxns
What are the symptoms of hypersensitivity rxns?
- Hives, anaphylaxis, urticaria, pruritis, angioedema
- Immediate = less than 1 hour
- Delayed = greater than 1 hour to days
What is the Pre-Tx for hypersensitivity rxns to contrast?
prednisone w/ diphenhydramine
What is the rapid Tx for hypersensitivity to contrast?
epi, saline, and albuterol
Chemotoxic reactions to contrast
Self limited symptoms-nausea, vomiting, and flushing
-Very common
Vasovagal reactions to contrast
Vasovagal rxns to contrast
- Increased vasovagal tone
- Decreased SA and AV node conduction
How do ultrasounds work?
Ultrasounds use high frequency sound waves to generate an image
Coupling gel-aids in wave transmission
hat are the pros and cons of ultrasounds
-Pros-no radiation, cheaper than other modalities
-Cons-Bowel gas and lung tissue hinder the image, technician skills variable
Can body habitus affect results?
Common clinical uses of ultrasounds
- Trauma
- RUQ pain
- RLQ pain
- Acute pelvic pain
- Cardiac concerns
- Pregnancy
- Evaluate blood flow (duplex/doppler)
- Procedures
AST exam-primary views or windows
FAST exam
- Subxiphoid
- RUQ
- LUQ
- Suprapubic
How do X-rays work?
X-ray
- Patient placed between film cassette and X-ray machine
- Pass through body and become attenuated
- X-rays + fluorescent coated film -> photochemical reaction -> light particles -> IMAGE
Pros and cons of X-rays?
X-rays
- Pros-Cheap, easily accessible, fast, excellent screening tool
- Cons-2D pic, radiation exposure, poor detail of soft tissue
Radiographic densities
-Air?
Air = Black
Radiographic densities
-Fat?
Fat = Dark gray
Radiographic densities
-Soft tissue/fluid?
Soft tissue/fluid = Light gray
Radiographic densities
-Mineral?
Mineral = Off white
Radiographic densities
-Metal?
Metal = Bright white
adiograph clinical uses
-Chest?
Chest-Assess lung pathology
Radiograph clinical uses
-Skeletal?
Skeletal-Examine bone structure
Radiograph clinical uses
-Abdomen?
Abdomen-Assess for obstruction, free fluid, free air
Radiograph clinical uses
-Dental?
Dental-Assess and detect pathology
CT scans
3D image of the body-X-rays on steroids
What are the pros and cons of CT scans?
- Pros-Widely available, quick, painless, somewhat reasonable price
- Cons-potential contrast reaction, exposure to radiation (up to 100x radiation from normal X-ray), diagnosis limitations
What are some common clinical uses of CT scans?
Neuro
- Pulmonary
- GI
- When an MRI is contraindicated or cannot be performed
How do MRIs work?
- Use of magnetic field to generate image-hydrogen atoms align
- Tissues generate different signals based on H composition
What are some MRI precautions?
- Cardiovascular devices-pacemakers, stents, mechanical valves, IVC filters
- Unstable patients
- Claustrophobic and agitated
- Large body habitus
What are the pros and cons of MRIs?
- Pros-Safe, no radiation, extremely precise with incredible detail of soft tissue
- Cons-not widely available, costly, body habitus, patient must have patience
MRI clinical uses
- Neuro
- Musculoskeletal
- Repro
Gadolinium considerations
Gadolinium considerations
- Contrast induced nephropathy
- Nephrogenic systemic fibrosis
Gadolinium considerations
-Contrast induced nephropathy
- Within 24-48 hrs of contrast administration
- Increased sCr
- Decreased GFR with oliguria (< 500 mL UOP/day)
Gadolinium considerations
-Nephrogenic systemic fibrosis
- Advanced renal failure or dialysis patients (GFR < 30 mL)
- 2 days-18 months post-exposure
- Symptoms-thickening and hardening of skin, head spared
What is angiography?
Angiography-Injection of contrast media directly into artery or vein via needle or catheter
- Invasive-percutaneous (think cardiac catch lab-fluoroscopy)
- Non-invasive-CT or MRI
What are the clinical uses of angiography?
- Neurological
- Pulmonary
- Cardiovascular
What is fluoroscopy?
Modality that uses continually emitted x-rays and allows for real time visualization
-Images are intensified - decreased radiation exposure
What are the clinical uses of fluoroscopy
- Esophagram
- Upper GI study
- Small bowel follow through
- Barium enema
- Cardiac
- Vascular
