5 Comments

  1. mmouawad on April 11, 2022 at 11:05 am

    I think something is wrong with the phrasing of one of the follow up questions:

    What are plane-parallel chambers calibrated in high energy electron fields?

    To minimize the gradient across the reference cylindrical ion chamber.

    Is it supposed to be why instead of what?

    • Max (editor) on April 11, 2022 at 11:27 am

      Yup, definitely intended to be “why.” I have corrected this error. Thanks!

  2. takpoly on July 26, 2023 at 4:15 pm

    On the last followup question, which “reference” depth you are referring to? The one we use for TG-51 electron beam (dref, calculated from R50), or typical electron reference depth of Machine calibration (typically at dmax)?

    • jocwhite on February 19, 2025 at 2:30 pm

      Yeah, I was thinking the same thing.

      • alex634 on February 22, 2025 at 12:59 am

        Dref and Dmax for 6MeV and 9MeV are pretty close together because the max plateau region isn’t as broad. But starting with 12 and moving onwards to 20Mev you start seeing like 99%, 98% and 96%. Calibration is done using dref, past the plateau of dmax to standardize clinics and not involve any gradient fluctuations. Your machine should be calibrated at a single point depth which wont stay at the same PDD for +-5mm

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