exposures review Flashcards
what is now recommended with digital detectors - reduces ESE (entrance skin exposure)
higher kVp
higher SID means
lower dose - loses energy when all other factors remain unchanged
higher OID reduces
overall exposure & increases magnification
reducing scatter overall
reduces dose
good right collimation lowers
dose& scatter therefore exposure
patients thickness
reduces exposure , when all other factors remain unchanged
increase factors for
grids
added filtration
lowers exposure
greater signal =
better images with less noise or graininess
what is detector saturation
excessive signal (exposure) gives no added visible improvement and adds to dose
to lower entrance skin exposure
up kVp, lower mAs
exposure technique charts
help produce consistent images, 2 types
fixed kVp
establish optimal kVp range, appropriate contrast w in acceptable limits. !!mAs is adjusted in increments of min. 30% (double or halve mAs for every 5 cm of subject thickness!! helps to decrease patient dose
fixed kVp is better suited for
DR systems - the rules are not as strict
variable kVp
2 kvp per cm of subject thickness + base kvp
2kvp times part cm +30kvp = new kvp
* consistent with the 15% rule while ensuring sufficient penetration
dose creep happens when
using a wide latitude
dose creep
wide exposure latitude with digital imaging, errors in technique selection are being made on the additive side for correction
EI number
evaluates how much exposure hit the IR
EI target number provide
reliable techniques based on exam type, projection, patient thickness
Automatic Exposure Control (AEC)
work well with CR & DR, used to help with ALARA, requires precise positioning of part for accurate exposure
DI (deviation index) number
determines the amount of over or under exposure
DI number increments
are set at 20% for underexposure , and 25% for overexposure
-2 would be an underexposure of
40% below
+2 would be an overexposure of
50% above recommended target
photon starvation
-under exposure or inadequate exposure to detector elements
responsible for lower visual or perceived resolution and obscuring anatomical features
80+ kVp should be used for
grids
non grid exams
80 or less kVp
data drop - excessive signal to IR
- occurs because of extreme overexposure
DELs are overwhelmed with photons (saturated) and become incapable of recognizing high energy values
Electronic masking (shuttering)
also known as cropping, a post processing function that reduces veil glare & improves viewing conditions
what must you have on an image
patient demographics & labeling laterality
medical radiographs are considered
a legal document
artifacts are
extraneous pieces of information on an image that do not truly represent the patient & their condition
artifact type - ghosting or phantom image
incomplete image erasure
artifact type - drop out
reductions in resolution, dust in CR or on laser imaging unit
artifact type - backscatter fogging
radiation
artifact type - reticulation
aka quantum mottle from underexposure
artifact type - histogram analysis error
improper collimation , technique, beam alignment
Biomedical informatics (BMI)
platforms used for medical purpose applications used for patient care and clinical research
LAN
Local Area Network - allows computers to share info and devises on the same network
WAN
Wide Area Network - network that spans a large area : city , state , nation etc.
DICOM (Digital Imaging and Communications in Medicine)
universal, standardized public format and protocol for communicating biomedical imaging files
HL7 (Health Level 7)
Organization that provides standards for interoperability that improve care delivery optimize workflow reduce ambiguity and enhance knowledge transfer among all stakeholders
* make sure to log out never share password *!!!
PACS
Picture Archiving and Communication System
PACS 3 system part
image acquisition - images are acquired in a digital format , can be transferred
display work station - any computer that a worker uses to view a digital image
Archive server - the “file room” of the PACS
ROI - region of interest measurement
can tell type of tissue or fluid from intensity reading
HIS
Hospital Information System
RIS
Radiology Information System
EMR/EHR
electronic medical record & electronic health records
HIPAA
Health Insurance Portability and Accountability Act- ensures confidentially of patient information
HIPAA year introduced
1996
