Computed tomography: Standard QA procedures
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- čas přidán 12. 03. 2016
- This video describes the basic quality assurance (QA) procedures for medical physicists involved in diagnostic radiology, and more precisely for computed tomography (CT). It describes the how-to of simple manipulations intending at measuring the performances of CT units.
Following topics are described:
-CTDIvol measurement and calculation (small and broad beams)
-Primary beam collimation at isocenter
-Hounsfield units in water
-Manipulation of a Catphan® phantom
-Manipulation of a QRM® phantom
This video has been prepared in the frame of the EUTEMPE-RX course for medical physics experts (MPE).
thank you for this nice QC procedure
GREAT WORK
Great video!!!
Thank you! 😊
Very detailed. I will definitely add this to my playlist. I made a similar video for the CT daily QA procedure.
Thanks! Can you send me the link to said video? I would love to check it out.
Great work thanka
Thanks!
Thanks..I really appreciate it
My pleasure!
Great!
Hi thanks for the good video
I have one question when you want to irradiate the phantom for measuring CTDI, should we irradiate the entire length of the phantom (from the beginning to the end of it) or just length of the ionization chamber (10cm)? Or you just select a certain length to irradiate?
Elnaz Ahanj Hi! My pleasure! For this step, it is better to irradiate once over 360° in the middle of the phantom over one typical collimation width at the isocenter (typically 1, 2 or 4 cm). This allows to measure the dose in the phantom but also the scatter tail at both sides. The value for a given collimation width is extrapolated at 100 cm.
@@nickryckx7817 THANKS for your help. The dosimetr I'm using gives me DLP directly so when for example I irradiate a length of 4cm I should devide the DLP to this length (4cm) and then it gives me CTDI? am I right?
Almost forgot: the acquisition is done in axial (or sequential or step-and-shoot, depending on the manufacturer) mode, not helical.
Elnaz Ahanj Indeed, if your current is fixed. On helical mode, the DLP might include the overranging, but in axial mode, this shouldn’t be an issue.
@@nickryckx7817 again THANK YOU SO MUCH! really saved me from confusion
but sir for head phantom i didnt see what raplace skull bone so the absorbed dose couldnt be corrcte ? and what inside phantom is it empty ?
There is no need for something to replace skull bone, as CTDI is defined like this (measured in a PMMA phantom). As its name states (CT dose index), it is a measurement of CT output, not patient dose. If you need a more accurate estimation of local patient dose, you can correct CTDI with the proposed correction method called the size-specific dose estimate SSDE, described in the report of the AAPM task group 204, freely available on the AAPM website.
As for the phantoms themselves, they are homogenous and made entirely out of PMMA, which make them quite heavy, especially the 32 cm phantom.
I hope this answers your question.
@@nickryckx7817 thank you sir thank you it was very helpfull allah bless you sir thank you
is this ge lightspeed system or other model
and if you know how to create or read bug error report ?
It is a GE Discovery CT750. But I unfortunately don't know how to generate a bug report
@@nickryckx7817 do you know what commands can i write inside cmd or terminal to detect problems inside the system if you know or know any refrence to that can guide please tell me
@@deltacompany4766 Sorry, I honestly don't know how to do that.
Aprendi mais.
Should phantoms be in complectm with CT?
Arman Grad Sorry, I don’t understand your question.
@@nickryckx7817 I mean following. You used CTDI phantom, then HU unit phantom. Does this phantom sell with computed tomograph together from one manufacture. Or manufacture sell only CT and each company should buy phantoms by himself?
Arman Grad I am honestly not 100% sure. In Switzerland at least, and probably in all the countries in the world, the device comes with a vendor-dependent QA phantom, which I have not shown in the video. All other phantoms are to be bought separately. The CTDI phantom is rather well defined and easy to manufacture. However, image quality phantom such as the CatPhan or QRM series are unfortunately pretty expensive.
can anyone explain me the definition of the term Phantom, really i confused it.
A phantom is a test object that is used in place of an organism for a given purpose. For example, a CTDI phantom allows for measuring the dose delivered by the CT. The CatPhan or QRM phantoms imitate the X-ray absorption spectrum of a human to allow for image quality assessment.
@@nickryckx7817 thanks for your great explanation, now I’m feeling relaxed.
@@mamoha4635 You're welcome!
Do manufacturers truly supply those QA materials with the machine.? Hmmmm
What is the purpose of pressing “0” ?
It's more a comfort thing than anything else. It allows you to set the scanning boundaries of your acquisition. For example, for CTDI measurements, it is easier to put the "0" landmark at the centre of the phantom and scan the "0" position. Or knowing the length of your phantom, if you set the "0" at one extremity, it allows you to set the range between 0 and the phantom length. But if you are familiar with the coordinate system of the couch of your own CT device, you can skip this part, if it makes you more comfortable.
@Nick Ryckx i need you to help me with my internship. It can be via zoom so that i understand more concepts.
Sorry, but this will not be possible. I can provide some help via the comment section but I am not willing to do it elsewhere.
@@nickryckx7817 I am a new resident but there absolutely no Medical Physicist in my hospital, i just needed your guidance step by step. But thank you
Can you post mechanical test of ct
That is something we don't perform and leave to the manufacturer.
QA