Part III Flashcards
the degree of blackening in the finished radiograph
optical density
OD is primarily controlled by [..]
mAs
Optical and mAs relationship
directly proportional
Tips for High Contrast-Short Scale of Contrast
- Low Scatter Radiation
- High Differential Absorption
- OD Falls on the straight-line portion of the CC
- Steep CC
Tips for Low Contrast-Long Scale of Contrast
- High Scatter Radiation
- Low Differential Absorption
- OD falls on the toe and shoulder
- Shallow CC
Kvp Vs. Density
Directly related to OD and IR expo but not proportional
↑ kVp, ↑xray quantity (kVp²)
↓kVp, ↓ xray quantity (kVp^5)
high KVp chain [H.Ix.DdD.Is.L
high kVp→ increase xray beam pene → decreases DA → increase scatter → low contrast
mAs vS Density
control quantity
directly prop to OD
↑ mAs, ↑ IR expo and film density
SID vS Density
indirect
↑ SID, ↓ film density and IR expo
mAs must be increased
OID vS Density
indirect
↑ OID, ↓ radiation, exposure, scatter, OD/IR
Anatomical Part vs Density [TAXO]
↑ thickness, ↑ attenuation, ↓ xray quantity, ↓ OD/IR exposure (indi)
lung [mass density]
320
fat [mass density]
910
soft tissue, muscle [mass density]
1000
bone [mass density]
1850
air cm [mass density]
1.3
barium [mass density]
3500
iodine [mass density]
4930
calcium [mass density]
1550
concrete [mass density]
2350
molybdenum [mass density]
10, 200
lead [mass density]
11, 350
rhenium [mass density]
12,500
tungstate [mass density]
19, 300
increased pt thickness chain
↑ patient thickness → increases volume of tissue irradiated → increases scatter rad → low contrast
constructive pathology vs density [IDD)
increase attenuation
decreases xray quantity
decreases OD/IR exposure
mAs must be increased
constructive pathology [3ACHMePPS]
Aortic Aneurysm
Ascites
Atelectasis
Cirrhosis
Hypertrophy
Metastases
Pleural Effusion
Pneumonia
Sclerosis
destructive pathology [2ABoCaDEOP]
active tuberculosis
atrophy
bowel obstruction
cancer
degenerative arthritis
emphysema
osteoporosis
pneumothorax
positive cm vs density
radiopaque
high atomic o.
increase attenuation
decreases x-ray quantity
decreases OD/IR expo
fat [effective atomic no.]
6.3
soft tissue and lungs[effective atomic no.]
7.4
bone [effective atomic no.]
13.8
air [effective atomic no.]
7.6
iodine [effective atomic no.]
53
barium [effective atomic no.]
56
concrete [effective atomic no.]
17
molybdenum [effective atomic no.]
42
tungsten [effective atomic no.]
74
lead [effective atomic no.]
82
high atomic no. chain
high atomic number → positive cm →radiopaque → high contrast
dev’t time vs density
increased development time, more silver ions are reduced to black metallic silver, increase OD
decreased development time, fewer silver is reduced to black metallic silver, increases OD
increased developer, temp, replenishment rate chain
increased developer, temp, replenishment rate → increases chemical fog → shallow curve → low contrast
→very high OD → OD on the shoulder portion → low contrast
decreased developer, temp, replenishment rate chain
decreased developer, temp, replenishment rate → very low OD → OD falls on toe portion →low contrast
screen speed vs density
large phosphor, greater no. of light produced per incident x-rays, increases OD/IR expo, mAs must be decreased
ultra high or hi plus [relative speed value]
300
high or fast screen [relative speed value]
200
medium, par or standard screen [relative speed value]
100
detail, slow or high resolution [relative speed value]
50
ultra-detail
25
Fast Screen chain
Fast screen
Fast Screen chain [SIDH]
Fast screen → steep curve → increases OD differences → high contrast
Slow Screen chain [S. S. D. L]
slow screen → shallow curve → decreases OD differences → low contrast
collimation vs density
increased collimation, decreases primary beam FS, decreases no. of photons available, decreases, scatter, decreases OD/IR expo, mAs must be increased
increased collimation chain
increased collimation chain → decrease FS → decrease tissue volume irrad → decrease scatter rad → high contrast
grid ratio vs density
high grid ratio, increases scatter rad clean up, decreases, scatter radiation, high contrast
filtration vs kVp
increased filtration → decreases low energy x-rays → increases beam hardening → decreases differential absorption → low contrast
screen film vs kVp
vice versa for direct-expo film
screen film → steep curve → increases OD differences → high contrast
affects the number number of x-ray pulses and the total average photon energy
voltage ripple
High voltage ripple/ Hi Generator chain
high generator → low V ripple (<1%) →increases average energy → decreases differential absorption → increases scatter → low contrast
