58 E. Saeedian et al.: Radioprotection 2025, 60( 1), 57 – 64
In veterinary practice, the animal adopters are asked to hold the animals. The International Commission of Radiological Protection, ICRP, recommended that radiation workers in the veterinary facility do not hold animals to avoid repeated exposure. In such cases, the immobilization should be done by people accompanying the patients i. e. their adopters( Mehdizadeh et al., 2019; IAEA, SRS 71, 2013). Therefore they are inevitably exposed to ionizing radiation. According to the international recommendations, and the recommendations of the ICRP, the dose to individual members of the public should be limited( Vano et al., 2015; Dietze and Menzel, 1994; ICRP publication 153; Sousa et al., 2021; Mayer et al., 2018). Therefore the dose received by the animal adopters should be investigated.
This study aims to measure the entrance skin dose, ESD values to the animals, and the dose equivalent values to the body, Hp( 10), and hands Hp( 0.07) values to the pet adopters during veterinary radiology.
2 Materials and methods
2.1 Digital radiography unit
In the Radiology Department of the School of Veterinary Medicine, Shiraz University, Shiraz, Iran, two X-ray units are employed for performing radiographic examinations on animals, including large and smaller animals. The Philips Practix 100 / 20 portable X-ray unit( Philips Medical System, Holland) is used for smaller animals such as birds and kittens; while the Philips Super M100 fixed X-ray unit( Philips Medical System, West Germany) is employed for larger animals, such as dogs and cats.
2.2 Preparation of TLD-100 chips
TLD-100 dosimeters, composed of LiF, Mg, and Ti, are widely used in dosimetry, including diagnostic radiology. They are cube-shaped chips measuring 3.1 mm 3.1 mm 0.9 mm, commonly used for medical dosimetry( Sadeghi, 2015; Dehghan, 2018; Zehtabian, 2017).
In the first step, the TLD-100 chips were annealed at 400 ° C for an hour followed by 80 ° C for 20 hours to remove residual signals. Then the element correction coefficient( ECC) for each TLD chip was obtained based on the following equation:
ECC i ¼ TLE
TLE i
; ð1Þ
where TLE is the average of the readings of all dosimeters in a TLD batch, and the TLE i is the reading of the i th TLD and ECC i is the element correction coefficient for the i th TLD chip. Using the ECC values, the reading of the TLDs can be corrected, when used for either personal dosimetry or animal skin dose( ZarifSanayei and Sina, 2024).
2.3 Calibration of TLD chips
The calibration process was performed by using a standard X-ray spectrum. Three calibration curves were drawn, one for entrance skin dose, i. e. ESD, to the animals, and two for personal dose equivalents, i. e. Hp( 10), and Hp( 0.07), to pet adopters.
2.3.1 Calibration process for ESD measurements for patients( animals)
For calibration, the TLDs were divided into several groups and exposed to various amounts of doses. After exposure, the TLDs were read out using a Harshaw 4500 TLD reader, and the resulting calibration curves were obtained. These curves showed how the TLD response varied with the radiation dose and were used to estimate the entrance surface dose during radiological procedures with similar tube voltages( Sina et al., 2016).
2.3.2 The calibration process for personal dose equivalent for animal adopters
The calibration of the TLDs for personal dose equivalent measurement was performed based on the recommendations of ISO 4037, by using ISO standard phantoms, and by applying the kerma to dose equivalent conversion factors given in the standard above. Two separate calibration curves were drawn for Hp( 0.07), and Hp( 10). The TLDs were installed on the surface of the ISO slab phantom, and ISO rod phantom, and exposed to known amounts of equivalent dose values, and the calibration curves were prepared.
2.4 Assessment of the ESD for the patient( animal)
To calculate the entrance surface dose( ESD) for pets( dogs, cats, and birds) undergoing X-ray imaging, the annealed TLD chips in thin tissue-equivalent pockets were placed on the surface of their body. The ESD values were measured for 20 animals in the radiology department veterinary medicine school in Shiraz, Iran.
Three TLD chips were placed in a dark plastic pocket and used for measurement of the entrance skin dose( ESD) to each animal( see Fig. 1). Additionally, three TLD chips were used to measure the background level of radiation exposure.
The TLD pockets were installed at the center of the radiation field for each animal. After the imaging procedure was completed, the TLD chips were read out using a TLD reader( Harshaw 4500, USA).
Each TLD chips were read out twice to consider the residual signal. The TLD readings were corrected for the ECC, and the sum of the readings was regarded as the net reading of each chip. The net reading of each chip was corrected for background values. nc net ¼ X3 i¼1 nc i
ECC i
: ð2Þ
The corrected reading( nc corrected) of the TLDs for each animal is obtained as follows:
nc corrected ¼ nc net Þ eachanimal � nc net Þ background
: ð3Þ