Intro to imaging Flashcards
radiographic timeline
-1885- x ray discovery by Wihelm Conrad Roentgen
-1940- 1/10 pts managed by radiographic study
-1950-1970- development of conventional angiography, nuclear medicine, U/S, and CT
-1980- almost all pts underwent some dx imaging
-1980s- MRI emerges
-1990s- molecular images
-new millennium- interventional radiography -> development of subspecialties based on organ system, specific fields -> genetic and molecular marker imaging
X-Ray
-high energy photons, emitted by electrons generated by x-ray tube
-wire element one end (cathode) and metal target (copper, now tungsten) opposite end (anode)
-high energy electrons collide with metal target (anode) creating x-rays
-x-rays pass through pt to hit a specialized detector
-now its more digitalized
pros of digital imaging
-Can be stored on CD/USB
-Permits remote access/telemedicine
-Can manipulate images
-Easy retrieval of previous studies/no lost films
ionizing vs non ionizing studies
radiation safety
-X-rays may cause damage to DNA molecules directly or produce free radicals that can chemically damage genetic material
-sievert = mSv or mrem -> measures radiation dosage
radiation risk factors
-age (younger)- cells dividing and cumulative dose
-organ -> ovaries/eyes are sensitive
-heart/brain -> radiation resistant (more barriers)
-body region
-cumulative dose
biological effects of radiation exposure
-Erythemia
-Skin peeling
-Ulcerations / skin lesions
-Cancers
-Cataracts
short term effects of radiation exposure
-skin erythema -> starts to appear a few hours after exposure
-hematopoietic syndrome- damages bone marrow, leads to anemia, infections, bleeding, occurs after a whole body dose over
-1 gray (Gy) = 100 roentgen (Rads)
-one roentgen of x-rays may deposit anywhere from 0.01 to 0.04 Gy (1.0 to 4.0 rad) in bone depending on the beam energy
-doses of 200 to 1,000 rad delivered in a few hour will cause serious illness
-whole body doses of more than 1,000 rad are almost invariably fatal
short term effects: GI syndrome
-destroys the cell that line the GI tract
-results in death due to inability to absorb nutrients and water
-occurs after a single whole body dose over 1000 rads (10Gy) for comparison 1 Gray (Gy) = 100 Roentgen (rads)
short term effects: cerebrovascular syndrome
-destroys nervous system tissues and blood brain barrier
-occurs after a single whole body dose of 5000 rads (50 Gy)
long term effects and primary concern of radiation workers in hospital settings
-cataract formation is deterministic and occurs at threshold of 100 rads
-vision impairment occurring at 500 rads
-skin effects can occur on hands of fluoroscopists who perform interventional procedures (SHIELDING IS ESSENTIAL)
effects on fetus
-depends on stage of pregnancy
-pre-implantation period
-8-15 weeks increased risk of neurodevelopment (10-20 rad threshold)
-organ malformations can occur with exposures during major organogenesis
-increased incidence of early childhood cancer has been observed in children exposed in-utero
issues concerning pregnant workers
-option of declaring yourself a pregnant worker NOT mandatory
-there is a declaration form
-fetal dosimeter in addition to standard dosimeter
-monthly exposure rate would be restricted to 50 mrem (.5 mSv) per month and 500mrem for pregnanct
dosimetry
-radiation workers are given badges that will monitor an individuals exposure
-use of landauer OSL (optically stimulated luminescence) badges
-badges are made of aluminum oxide
-nuclear medicine workers are also given ring badges which contain LiF TLD’s (thermo luminescence dosimeters)
ALARA princinples
-always wear personnel monitor
-radiology personnel should not restrain pts
-sound radiographic exposure factors
-cardinal rules of radiation protection: time, distance, shielding
distance
6 feet of clearance
shielding
-lead aprons can reduce exposure by as much as 95%
-thyroid shields and lead gloves are available for use in fluoroscopy
-when working with radioactive material, use lead blocks, syringe shields and lead pigs to reduce exposure
scatter radiation
-protect- time, distance, shielding
-MC type of exposure you will receive in dx radiology
safety guidlines
-justification- appropriate indication for imaging procedure
-optimization- ALARA (as low as reasonably achievable)
-limitation
-american college of radiology guidelines- systems to decrease the utilization of low yield CT scans
target film distance (TFD)
-distance between tube and cassette
-Increased TFD produces clearer image
-3 feet ideal distance for chest X-rays
object film distance (OFD)
-distance between the person and cassette
-Short as possible for most accurate image
-If increased will cause magnification
-decrease distance causes decrease magnification! (this is good)
-greater distance causes scatter
golden rules
-Review previous tests to answer current questions.
-Select the appropriate study.
-Communicate/Consult with the radiologist & technicians!!!
-Only request studies that will influence management.
-Prepare patient to minimize delays in getting study done.
-Continually filter results in the context of the patient.
-Ensure appropriate follow-up
-Balance risks and benefits
-Provide patient-centered care: inform, consent, educate
reasons for errors in radiology
-errors in interpretation
-failure to suggest next appropriate procedure
-failure to communicate results in timely and clinically appropriate manner
radiology vs other medical specialities
-yields presumptive….….. but NEITHER a histological nor a biological diagnosis
-depends entirely on visual perception!
