Radiochromic films for dental CT dosimetry: A feasibility study

Abstract

Dental CT dose evaluations are commonly performed using thermoluminescent dosimeters (TLD) inside anthropomorphic phantoms. Radiochromic films with good sensitivity in the X-ray diagnostic field have recently been developed and are commercially available as GAFCHROMIC XR-QA. There are potential advantages in the use of radiochromic films such as a more comprehensive dosimetry thanks to the adjustable size of the film samples. The purpose of this study was to investigate the feasibility of using radiochromic films for dental CT dose evaluations. Film samples were cut with a width of 5mm and a length of 25 mm (strips), the same size as the Alderson Rando anthropomorphic phantom holes used in this study. Dental CT dose measurements were performed using simultaneously both TLD and radiochromic strips in the same phantom sites. Two equipment types were considered for dental CT examinations: a 16 slice CT and a cone beam CT. Organ equivalent doses were then obtained averaging the measurements from the sites of the same organ and effective doses were calculated using ICRP 103 weighting factors. The entire procedure was repeated four times for each CT in order to compare also the repeatability of the two dosimeter types. A linear correlation was found between the absorbed dose evaluated with radiochromic films and with TLD, with slopes of 0.930 and 0.944 (correlation r>0.99). The maximum difference between the two dosimeter's measurements was 25%, whereas the average difference was 7%. The measurement repeatability was comparable for the two dosimeters at cumulative doses above 15 mGy (estimated uncertainty at 1 sigma level of about 5%), whereas below this threshold radiochromic films show a greater dispersion of data, of about 10% at 1 sigma level. We obtained, using respectively Gafchromic and TLD measurements, effective dose values of 107 μSv and 117 μSv (i.e. difference of 8.6%) for the cone beam CT and of 523 μSv and 562 μSv (i.e. difference of 7%) for the multislice CT. This study demonstrates the feasibility of radiochromic films for dental CT dosimetry, pointing out a good agreement with the results obtained using TLD, with potential advantages and the chance of a more extensive dose investigation.

Using GafChromic film to estimate the effective dose from dental cone beam CT and panoramic radiography

“…The GafChromic ® XR-QA film (ISP Corp., Wayne, NJ) is designed specifically as a quality assurance (QA) tool for radiology and dosimetry applications. In combination with flatbed document scanners, 7 it has been used for measuring medical 8 and dental 9 CBCT doses and CT doses. 10,11 Some of the characteristics of this film have been studied: energy dependence 8 and angular dependence.…”

“…Effective doses ranged between 8 mSv and 14 mSv. When PSP, CCD and FPD units were compared, the effective dose of the panoramic unit using the PSP receptor (14 mSv) was higher than those of the CCD and FPD units (8)(9)(10)(11).…”

Cone beam computed tomography for dental and maxillofacial imaging: technique improvement and low-dose protocols

“…Evaluations of effective dose were made with an Alderson Rando anthropomorphic phantom (The Phantom Laboratory, New York, USA) by placing in the internal seats of measures radiochromic film strips measuring 4 mm × 25 mm. Radiochromic films with good sensitivity in the X-ray diagnostic field have been recently developed and are commercially available as GAFCHROMIC XR-QA and XR-CT (International Specialty Products, Wayne, NJ) [11]. Fifty-eight locations have been used for the measurements in order to have a good sampling for all the involved organs at risk (bone marrow, bone surface, brain, salivary glands, thyroid, oral mucosa, extrathoracic airway, esophagus and lymph nodes).…”

“…Fifteen repeated acquisitions were made, so as to obtain values of absorbed dose compatible with the sensitivity of radiochromic film, even for peripheral sites affected only by scattered radiation. The evaluation methodology is described in detail in Rampado et al [11]. All parameters used for panoramic and cephalometric images in lateral and antero-posterior projections are reported in Table 2, both for adult and pediatric protocols.…”

Radiation dose measurements in a dental orthopantogram unit using indigenously developed optically stimulated luminescence dosimeters

“…Some factors that have made OSL a popular technique are its simplicity, all optical nature, wide dynamic range of measured dose, ease for automation, re‐read capability, ability to perform imaging, optical fibre‐based online dosimetry and the availability of diverse instruments . Several measurement tools, such as the TLDs with an anthropomorphic phantom, metal oxide semiconductor field effect transistor (MOSFET), Farmer type ionization chamber, dose area product (DAP), feasibility study for radiochromic films for dental computed tomography (CT) dosimetry and characterization of OSLDs for dentomaxillofacial dosimetry have already studied and evaluated the doses in dental units. In this study, we used an indigenously fabricated polymethyl methacrylate (PMMA) head phantom and 3 mm diameter discs of three optically stimulated luminescence phosphors.…”