i was fixing a trouble with collimator, but i have the next question: when the collimator is putted at 10mm Slice, WHERE is checked this slice? at collimator window, at center of rotation, or at detector window??
As the x-ray beam is a diverging one. Like what you have asked the thckness at collimator will be different from that of at the Detector. The slice thickness what we are talking in CT is that of the patient body, which is at the centre of the entire scan rotation geometry. Hence the slice thickness is always calculated at the center of the rotation geometry.
The collimator width that is specified is the window that is actually where the beam hits the detector. This distance is measured in the collimator and is a factor of the projection. All of the manufactureres MUST track the width to establish dose guidlines and patient safety.
i asked about matter to some radiologysts, and two agree with Mr Vijai, that the slice is defined at center of rotation.
however, i decided to check this in a fixed type CT collimator (SCT4500), that uses a slot to make slice thickness, and i surprised that in the center of rotation, is about 14-15mm of main beam thickness; what is involved if this is misadjusted?? of course on GE CT collimators.
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Carlos Duran
CT collimator position doubt (basis)
April 28, 2006 10:14
Hello:
i was fixing a trouble with collimator, but i have the next question: when the collimator is putted at 10mm Slice, WHERE is checked this slice? at collimator window, at center of rotation, or at detector window??
thank you.
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Vijai shankar raja
Re: CT collimator position doubt (basis)
April 28, 2006 10:06
As the x-ray beam is a diverging one. Like what you have asked the thckness at collimator will be different from that of at the Detector. The slice thickness what we are talking in CT is that of the patient body, which is at the centre of the entire scan rotation geometry. Hence the slice thickness is always calculated at the center of the rotation geometry.
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Ralph Childs
Re: CT collimator position doubt (basis)
April 29, 2006 12:56
Carlos,
The collimator width that is specified is the window that is actually where the beam hits the detector. This distance is measured in the collimator and is a factor of the projection. All of the manufactureres MUST track the width to establish dose guidlines and patient safety.
Scooter
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Carlos Duran
CT collimator position doubt (basis)
April 30, 2006 08:30
first of all, thank you for your answers.
i asked about matter to some radiologysts, and two agree with Mr Vijai, that the slice is defined at center of rotation.
however, i decided to check this in a fixed type CT collimator (SCT4500), that uses a slot to make slice thickness, and i surprised that in the center of rotation, is about 14-15mm of main beam thickness; what is involved if this is misadjusted?? of course on GE CT collimators.
thank you,
to rate and post a comment