| Posted: Fri Jun 29th, 2012 10:57 am |
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1st Post |
CTnovice
Member
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Hi, this question is more for Jack but feel free to contribute everyone. I was taught on a VCT 64 GE that you should always use the same kV in your scout as your helical scan. Otherwise your final dose calculation will be incorrect and it effect the tube current modulation. However, recently i have heard that this theory doesnt apply to GE ct anymore and that you can use 100kV in your scout to save dose and still use 120 kV for your helical scan. Just wondering how correct is this statement? Many thanks
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| Posted: Sun Jul 8th, 2012 11:22 pm |
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2nd Post |
ctisus
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Jack it is!!
Initial helical scanners, such as CTi, did need the same KvP for both
acquisitions for the Auto-mA feature to work at its best capability.
The first generation of multi-slice CT followed that rule. However,
since the 8 slice and higher scanners have been available, it is okay to
have different KvP values selected between the scout parameters and the
actual scan sequence parameters. The system has enough computational
power and programming to "see" the different settings and adjust for
that. The operator's manual states clearly that a "well penetrated" is
needed for the software to work at peak value. In the case of most
pediatric exams a KvP value of 80 is likely to give you enough
penetration for the majority of exams. If you are doing IAC's, hips,
knees, or any other dense piece of anatomy you would probably be better
served with 100 or even 120 KvP settings. Additionally, if you are doing
someone who is chronologically a pediatric patient but their body
habitus is that of an adult consider changing the KvP setting to a
higher value for better penetration. PLEASE check with a supervising
radiation officer or physicist for direction on where these higher
settings should be used. The primary factor in utilizing Auto-mA to its
fullest is to have the patient correctly centered with the thickest part
of the mass centered to iso-center.
Can you use different KvP values between scout and scan: YES. Be sure
the mass is centered to iso-center AND the scout to be used for setting
scan parameters is well penetrated. To save dose you might even consider
doing a lateral scout first at 80 KvP and the scout for planning being
done at 100 KvP. This gives you an image you can put a grid on first to
check centering to iso-center and then a well penetrated scout (done at
the correct iso-center setting) for scan set up.
Good question. I believe it is always smart to check and be sure before
ever exposing someone and then saying, " well I can do better next
time". Make every exam feel as important to you as if you were scanning
a loved one. Be kind and be smart when planning on any radiation
exposure by using the ALARA principle to be a factor in all your
planning. Good luck and thanks for being a dose champion in your
department. Everyone needs one to act as Jiminy Cricket and remind us
all to, " let your conscience be your guide"!
Jack Risner
Clinical Product Specialist
GE Healthcare
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| Posted: Mon Jul 9th, 2012 08:40 am |
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3rd Post |
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