Abstract
The location and field size of the incident X‐ray beam in panoramic dental radiography cannot be ascertained visually most of the time. However, these parameters are needed for quality control and dosimetry determination. To alleviate this problem, we tested GafChromic XR‐QA film on two panoramic systems. For each system, we used the length of a cross‐sectional image of the incident beam and the exposure measurement with a pencil ion chamber to compute the dose–area product. The result was confirmed by direct analysis of a dose distribution on a film. Placement of the ion chamber was determined by the latter images. The GafChromic XR‐QA version of radiochromic film has thus been demonstrated to usefully complement a pencil ion chamber in the testing of a panoramic radiography system.PACS numbers: 87.52.Df, 87.59Bh, 87.66.Cd, 87.66Jj
Highlights
Panoramic radiography in dentistry poses several challenges for medical physics testing
We evaluated the use of this new film to record the location and dimensions of the X-ray beam in a medical physics evaluation
Dose–width product (DWP) was computed using the pencil ion chamber reading and the length of the chamber’s sensitive volume.(3) Multiplying DWP by the length of the image of the prepatient collimator, we obtained the dose–area product (DAP) at the pre-patient collimator. This value, which is supposed to be invariant with respect to distance from the radiation source, was compared to the DAP computed from film at the post-patient collimator
Summary
Panoramic radiography in dentistry poses several challenges for medical physics testing. Goldstein(1) developed a jig to help with some of the quality control measurements. He demonstrated the inaccuracies of thimble ion chambers in measuring radiation exposure.(2). That deficiency has perhaps been overcome by the more recent proposal of Perisinakis and colleagues(3) to use a pencil ionization chamber, which has a more uniform response along the length of the sensitive volume. Those authors demonstrated the use of such a detector to determine dose–area product (DAP) and the subsequent computation of effective dose from the DAP. With the move to digital technology, film processors, and dental films or general diagnostic radiography films, will no longer be available to help with these tests
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