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  • Granted Patent for CT Dose Profiler

    Tuesday, 07 November 2017

    Lars Herrnsdorf, CSO RTI Group, one of the innovators and developers behind the CTDI dose detector ”CT Dose Profiler (CTDP)”.

    Congratulations on being granted a patent for the CT Dose Profiler in Sweden, United Kingdom, Germany and France; this is in addition to the existing patent in US and China. The CTDP has been a real team effort and also a very important task in securing a new way to introduce a QA control tool for CT and CBCT.


    Q: How did you come up with the idea for this solution?

    LH: I was Inspired by another RTI product, an X-ray meter that has a very small dose detector; The Barracuda Multipurpose detector, MPD. It demonstrated the possibilities to measure the dose profile from a CT scanner in the “scout” mode. I then realized that it was possible to design a “point dose” detector that was suitable to mount in a small rod and then be used as a rotational, symmetrical dose detector for CT.
    I went back to my home workshop and made the first prototype based on existing RTI parts.

    I also had to make software that could calculate Dose, DLP and CTDI based on the dose profile.

    At RSNA (USA) 2003 I had the prototype with me and got the opportunity to meet an important GE CT QA individual. He was so excited to the new concept, that he booked a visit the next day to their CT headquarters where I could demonstrate the CTDP at their CT test “cells”.
    It went extremely well and was very exciting in how easy they now could document the new CT scanner’s dose profile. The order for the first system arrived the same day! The rest is as they say history.


    Q: What have been the challenges with development of the product?

    LH: To find a design approach to meet the need for a sensitive, rugged, energy and angle independent detector that can measure in the clinical field in such 3D space. To fulfill that we have had to make our own solid-state x-ray detector. Although the work to introduce a new way of measurement takes considerable effort, such challenges are not new for the RTI Group.


    Q: Why is the CT Dose Profiler important for CT Quality Assurance?

    LH: Of all artificial X-ray sources, medical radiation sources supply the largest dose to the human population, and of these, Computer Tomography (CT) contributes 70% of the total dose.
    A CT examination gives 10-50 times more dose to a patient than corresponding conventional examinations, and therefore quality control is important and so should be made regularly.

    Dose measurement is traditionally done with a 100mm long pencil-shaped ionization chamber. However, at present CTs with beam collimation of up to 160 mm are available, which results in an incomplete measurement of the primary radiation using an ion chamber.  CTDP measures dose profiles of any length, and therefore is not restricted to a 160mm field. 


    Q: So, what’s the next step?

    LH: To design a CTDP that fulfills the new IEC CT regulations for safety, constancy and acceptance of CT and CBCT. Moreover this same design approach could be used as a general 3D point dose detector for clinical use for all diagnostic modalities. 



    The CT Dose Profiler was developed in conjunction with Björn Cederquist and released in 2009. Lars Herrnsdorf is one of the founders of RTI and has worked in the Xiray QA field for over 30 years.

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