Unit 1 + Unit 2

quality of x ray

penetrability energy level of the beam (kVp)

quantity of x ray

intensity, number of x rays being produced in the tube (mAs)

primary exposure factors

mA, kVp, exposure time, distance

secondary exposure factors

contrast, receptor exposure, spatial resolution, distortion

mA (milliaperage)

measure of x ray tube current

kVp (kilovoltage peak)

controls both quantity and quality, determines speed at which electrons in tube move

exposure time

affects quantity, determines the length of time for tube current allowed to flow from cathode to anode

distance

controls the quantity or intensity of the beam, SID

contrast

degree of difference between the light and dark areas of a radiograph

attenuation

reduction in radiation intensity from absorption and scattering as it passes through matter

receptor exposure

amount and quality of radiation reaching the image receptor, affected by mAs and kVp

spatial resolution

sharpness and quality from the visibility and accuracy of recorded anatomical structural lines

distortion

misrepresentation of the true size of an object on the radiograph

differential absorption

different degrees of absorption in the different tissues that result in image contrasts and formation of the image

transmission

incoming photon passes through the anatomic part without any interaction with the atomic structure

subject contrast

absorption differentiates in differences in tissue thickness density Z# affecting quality of x ray beam

scatter

adds unwanted exposure to the radiographic image due to compton interaction

quantum noise (static of images)

depends on the quantity of x ray photons, if mA increases, not enough KV no good picture

radiopaque

absorbs x ray, not transmission, appear white

radiolucent

allows x. ray to pass through, appears dark

contrast resolution

ability of IR to distinguish between objects that have similar contrast

optimal kVp

kVp value high enough to ensure penetration

dynamic range

range of exposure intensities an IR can detect

contrast agent

substance that can be injected or ingested to increase or decrease attenuation

compensating filter

effective kVp

low attenuation to high attenuation

air, fat, muscle, bone

positive contrast agent

absorbs more x ray, high Z#, lighter shades

positive contrasts examples

barium (56) and iodine (53)

negative contrast agent

decreases attenuation, darker shades, air

iodinated contrast require ___ kvp

70-80

barium sulfate contrast require ___ kVp

single (100-120), double (90-100)

factors that affect attenuation

tissue thickness, Z#, tissue density, tissue type, x-ray beam energy

15% rule

increase kVp, double mAs or decrease kVp, half mAs

for a hyposthenic or asthenic patient you would …

half your technique

for a sthenic patient you would…

use normal technique

for hypersthenic patient you would…

double your technique

how would 15% rule affect xray

changing KV will change the quantity and quality

contradiction for barium

scheduled surgery, perforation, allergy to barium

contradiction for iodinated contrast

allergy to iodine

pediatric requirements

require a decrease in exposure factors, use shortest exposure time, close collimation

geriatric requirements

decreased technique because of tissue, enhanced patient care

bariatric requirements

significant increase in exposure, grid and collimation, image patient in sections

pathologic conditions

alter technique of anatomic part, additive and destructive diseases

additive diseases can…

increase the absorption, difficult to penetrate due to extra tissue, increase KV

destructive tissue can…

decrease absorption, easier to penetrate due to loss of tissue, decrease the KV

abdomen additive pathology

ascites, aortic aneurysm, cirrhosis

chest additive pathologies

CHF, pleural effusion, pneumonia

skeletal additive pathology

osteoma, pagets disease, osteopetrosis

nonspecific additive pathology

abscess, edema, morbid obesity

abdomen destructive pathology

bowel obstruction, free air

chest destructive pathology

pneumothorax, emphysema

skeletal destructive pathology

osteomyelitis, degenerative arthritis, osteopenia

nonspecific destructive pathology

emaciation

motion definition

deteriorates or diminishes spatial resolution

voluntary motion

patient moving, fidgeting, breathing

involuntary motion

peristalsis, heart motion

causes of motion examples

unclear instructions, improper immobilization, pain, involuntary movments

exams with motion problems

angiography, pediatric, geriatric, abdomen and bowel studies