A Pioneer at Measuring CT Dose

The RTI CT Dose Profiler for Barracuda, Piranha and Cobia Flex has taken the CT quality assurance to the next level. Because of its revolutionary design it has transformed the CTDI measurement from being inaccurate due to underestimation of the dose for wide beams to be more exact. It also has the ability to further analyze the result – all in one shot.

The rapid advancements in CT technology are placing new demands on methods and equipment used for quality assurance. The wide beam widths found in CT scanners with multiple beam apertures make it difficult to use existing CT dose ionization chambers to measure the total dose given to the patient. Using a standard 10 cm CT ionization chamber may result in inaccurate measurements due to underestimation of the dose profile for wide beams. The CT Dose Profiler was developed to solve this problem.

The dose is measured in every point of the X-ray beam and the total dose profile is acquired regardless of how wide the beam is. There is no limitation of the beam width. This makes it possible to measure without the drawbacks of traditional CT probes.

With the CT Dose Profiler you can avoid more expensive methods that require both preparation before and read-out after each scan (like TLD and X-ray film). The CT Dose Profiler is also ideal for measuring point dose and dose rate in the CT beam.

The CT Dose Profiler is based on solid-state technology. It is robust and it fits into existing standard phantoms used for CTDI measurements.

Following parameters are achieved from a single exposure:

  • CTDI100
  • Point Dose
  • CT dose profile
  • CTDIw
  • CTDIvol
  • DLP
  • Performance of the AEC
  • FWHM (Full width at half maximum of the dose profile)
  • Geometric efficiency%

Specifications with Black Piranha

Dose Rate 40 nGy/s - 760 mGy/s 
  0.26 mR/min - 5200 R/min
Accuracy ±5 % or ±10 nGy/s
Spatial Resolution 0.25 mm

Specifications with Cobia Flex / Sense

Dose rate: 3.5 µGy/s to 3.3 Gy/s
Inaccuracy ±5 % or ±0.4 µGy/s

The software runs on either a PC or Tablet connected either to a Barracuda or a Piranha. After each exposure, the data is presented instantly. The detector can be used for both point dose and CTDI measurements.

Only one exposure is needed to measure and calculate CTDI100, CTDIw, CTDIvol, DLP, FWHM and Scatter index. To be able to simplify the procedure from normally 5 exposures to only one measurement in the central phantom position (CTDI100,c), a factor k is multiplied with CTDI100, to get the CTDIw. The k factors are stored in the existing CT Database and have been acquired from a number of different CT systems.

In the software, you are also able to measure the CTDIw with the five exposures at different phantom positions but is seldom needed with the new “Central Point Method”.

Measured data is saved and can be re-opened for later reviewing. Data can also be printed or exported to Microsoft Excel for further analysis.

Example CTDI measured in a head phantom for a nominal beam width of 20mm and pitch 0.969. Dose profile acquired in central position of phantom.

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