8. MRI safety
• Metal object
• Wire
• T top hoger op ECG
• No nerve stimulation (itch)
• Hearing protection
• Training
• SAR warmte (veel schakelen)
– 4W/kg (neo 2W/kg)
9. MRI safety
• New implants safe
• 5 gauss line / 0.0005 T
• Tissue heating
• RF burns
– loop by touching hands
• Switching rate
• pregnant: better than Xray
11. Buis / techniek
• 3 fase generator
• Continu hoge spanning
• Korter belichting
• Fototimer: ionisatiekamer voor
cassette
• Grid ratio hoger:
– meer contrast, meer straling, meer
loodstrips, minder scatter
12. Buis / techniek
• Bucky is moving grid
– Meer dosis
• Lateral decentering
• Exposure spread out
• Longer exposure
– Higher cost
• K (performance) hoger is meer
contrast
13. Buis / techniek
• Bucky factor (straling ontvangen /
straling verzonden)
– hogere BF bij hogere grid ratio
– hogere BF bij dikke pat.
– Hoge BF is hogere dosis
• Air gap ook minder scatter
14. Screen
• Xray naar licht (beter waargenomen
door film
• La / Ga
• Speed 100-400
• Thin more detail
• Thick more signal, more blur
15. Fluoro
• fosfor: X naar fotonen. CsI
• kathode: fotonen -> electronen CsAn
• anode: versnelt electronen
• fosfor 2: electronen ->fotonen. CsI
• Video camera of digitaal
16. Fluoro
• Brightness gain = minfication gain x
flux gain
• min.gain = oppervlak input /
oppervlak output
• 4 lines / mm (CsI)
• Distortion
– perifeer, lage brightness (vignet),
electron beam inhomogeen
17. Mammo
• Mo anode, energie 17.5 en 19 keV,
beter contrast
• focal spot .3 mm (.1 voor vergroting)
• 24 KVp (soft tissue contrast)
• 65 cm tube-object (high res)
• short time, high mA (motion, dose)
18. Mammo
• Compression and grid to reduce
scatter
• Compression:
– dose, short exposure, less overlap
• automatic exposure
• Screen / film
19. CT
• Decrease noise
– high mA
– thick slice
– decrease matrix
– decrease FOV
• Artifact
– move (streak), alias (streak), cupping
(black)
– Calibration (ring)
20. DR
• Plate
– fosfor/ Eu stores info Eu 2+->3+
– releases after laser pulse
– Blue light
• particle 5-10 um
– small grain sharp
– large grain sensitive