I am getting darker images with window shift towards lower valuesiewater phantom images showing CT values at -55 at 120 KV ,2s and 4 sec scan.the images get pretty ok at 1sec.ct value -25.software,ct number calib has no effect.KV and ma waveform are o.k.Any suggestions
Are the low CT numbers throughout the phantom or mainly in the top region??? If they are in the top, you need to check phantom vertical position when doing the calibration.
If they are consistent throughout the phantom then you have a number or things to check:
1) How old is the tube? Is the dose output dropping off due to tungsten splatter on the port?
2) What is the condition of the collimator filter? Does it have cracks in the surface?
3) Was this phantom okay before? Make certain that the "filler" is actually dsitilled water and not alcohol.
4) You need to verify your actual rotation speeds. It alomost sounds like your slower speeds are incorrect.
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sunil Kumar
Image quality-SR7000
October 07, 2005 09:22
I am getting darker images with window shift towards lower valuesiewater phantom images showing CT values at -55 at 120 KV ,2s and 4 sec scan.the images get pretty ok at 1sec.ct value -25.software,ct number calib has no effect.KV and ma waveform are o.k.Any suggestions
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Ralph Childs
Re: Image quality-SR7000
October 08, 2005 12:59
Sunil,
Are the low CT numbers throughout the phantom or mainly in the top region??? If they are in the top, you need to check phantom vertical position when doing the calibration.
If they are consistent throughout the phantom then you have a number or things to check:
1) How old is the tube? Is the dose output dropping off due to tungsten splatter on the port?
2) What is the condition of the collimator filter? Does it have cracks in the surface?
3) Was this phantom okay before? Make certain that the "filler" is actually dsitilled water and not alcohol.
4) You need to verify your actual rotation speeds. It alomost sounds like your slower speeds are incorrect.
Let me know if I can help you.
Scooter
scanner1@eim.ae
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SHIJU KARAKKOOTTIL
Re: Image quality-SR7000
October 08, 2005 04:13
Hi
Conform your tube centering.
Regards,
Shiju.
shiju@cura.co.in
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