[Intl_DxMedPhys] Hybrid Canon IR/CT displayed CTDIvol accuracy

[Michael Masiar]

I have a client with this system. If they buy the upgraded 320 slice
detector its truly 320 x 0.5 with a 16 cm detector.  Whereas the other
option is a "160" slice system with a 4cm detector... so its really 80 x
0.5 and the 160 is some flying focal spot nonsense.  If your system doesn't
have 320 as an option and the helical protocols say 160 x 0.5 ... they are
really 80 x 0.5.  With that adjustment everything comes out ok, measuring
CTDIvol between 5 and 20% below reported depending on the protocol.


Michael Masiar MS DABR
Certified Medical Physicist
Therapy Physics, Inc.
2501 Cherry Ave., Suite 270
Signal Hill, CA 90755
email: mmasiar at gmail.com
cell: 310-625-9906
office: 562-317-0650



On Fri, Feb 21, 2025 at 2:02 PM Daniel Vergara via
Intl_dxmedphys_wd_osu_list <intl_dxmedphys_wd_osu_list at lists.osu.edu> wrote:

> For those of you who have worked with Canon CT scanners, in particular the
> hybrid IR/CT Alphenix CT scanner, what has been your experience with the
> displayed CTDIvol accuracy? Do you often get CTDI accuracy results with
> large % differences?
> For those of you who have worked with Canon CT scanners, in particular the
> hybrid IR/CT Alphenix CT scanner, what has been your experience with the
> displayed CTDIvol accuracy? Do you often get CTDI accuracy results with
> large % differences?
>
> We have measured repeated CTDIvol differences exceeding 20% for several
> protocols of different collimation (nT), tube voltage, phantom size, pitch,
> axial vs helical, scanned FOV and rotation time. And these high %
> differences have repeated over the course of a year. We have reached out to
> Canon reps for assistance, but have not gotten satisfactory help. We also
> tried measuring the CTDI using the Canon CTDI instructions, in which 10
> peripheral measurements are made with defined time delays for certain
> rotation times and then averaged.
>
> I'm fine admitting if we've performed the measurements incorrectly,
> somehow, but I need to know how testing CTDI on a Canon Alphenix differs
> from other scanners.
>
>
> TIA
> Daniel
>
> --
> Daniel Vergara
> xvergarax at gmail.com
>
>
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