(Methods and materials)
CT Scanning
CT scans were performed on a 64-detector row CT scanner (Lightspeed VCT; GE Healthcare, Wisconsin, USA). The scanning parameters were as follows: Scan mode, axial: Tube voltage, 120 kVp; tube current, 260-280 mA; beam width, 20 mm; scan mode, full; gantry rotation time, 2.0 seconds; bowtie filter, small; CTDIvol, 86.85 mGy; dose length product (DLP), 1182.46 mGy・cm. The scanning range was from parietal to foramen magnum.
Dose measurement
We used a whole-body human equivalent phantom (Whole Body Phantom PBU-10; KYOTOKAGAKU, Kyoto, Japan). The whole body phantom PBU-10 is a life-size (height; 150 cm, weight; 50 kg), full body anthropomorphic phantom, with a state-of-the-art synthetic skeleton, lungs, bronchus, etc, embedded in KYOTOKAGAKU original soft tissue substitute. And there are no metal parts or liquid structures. The outside radiation dose was measured using a real time skin dosimeter (RD - 1000; TORECK CO, Kanagawa, Japan).
A dosimeter sensor was installed near the head, where the thyroid gland and mammary gland were assumed to be highly sensitive to radiation6). We measured and compared for outside radiation dose between with- and without RPS wrapped around the neck to chest (RADPAD Bode Guard for CT {Lower abdomen shield}; Worldwide Innovations & Technologies .Inc, Kansas, USA). The measured value of radiation dose obtained was the mean value of five measurements (Fig.1).
Fig. 1: Measurement scene
References: Tuchiya General Hospital / Japan 2020
Statistical analysis
To compare the outside radiation dose of the with- and with RPS at head CT examination, we used the Mann-Whitney U test. Values of p < 0.05 were considered to be statistically significant.
(Results)
The mean outside radiation dose of the right thyroid gland were 3.49±0.21 mGy and 2.34±0.02 mGy for the without- and with RPS. The mean outside radiation dose of the left thyroid gland was 3.73±0.25 mGy under without RPS and 2.51±0.01 mGy under with RPS. The thyroid gland showed high dose at the left. The mean outside radiation dose of the both thyroid gland was 3.61±0.23 mGy under without RPS and 2.42±0.01 mGy under with RPS (Fig.2).
Fig. 2: Graph of scattered radiation dose in the thyroid gland
References: Tuchiya General Hospital / Japan 2020
There was significant higher difference of the average outside radiation dose (P < 0.01). The average outside radiation dose was 32.9 % lower with RPS (Table.1).
Table 1: It displays the measured dose values
References: Tuchiya General Hospital / Japan 2020
The mean outside radiation dose of the right mammary gland was 0.73±0.17 mGy under without RPS and 0.11±0.01 mGy under with RPS. The mean outside radiation dose of the left mammary gland was 0.69±0.17 mGy under without RPS and 0.08±0.01 mGy under with RPS. The mammary gland showed high dose at the right. The mean outside radiation dose of the both mammary gland was 0.71±0.17 mGy under without RPS and 0.10±0.01 mGy under with RPS (Fig.3).
Fig. 3: Graph of scattered radiation dose in the mammary gland
References: Tuchiya General Hospital / Japan 2020
There was significant higher difference of the average outside radiation dose (P < 0.01). The average outside radiation dose was 86.6 % lower with RPS (Table.1).