The efficiency of lead and non-lead shielding on breast dose in head CT.

The aim of the study was to assess the effect of the shielding material and its thickness on the measured skin dose to the breasts during the CT examination of the head. The helical and axial head CT was performed on an anthropomorphic phantom (PBU 60). Two types of shielding were tested-lead and non-lead (antimony-bismuth) shielding. Measurements with different thicknesses were performed and the shielding efficiency of the materials was compared. Skin dose to the breasts was measured with an educational direct dosimeter (EDD-30). The shielding efficiency during both scanning protocols indicated an increased dose reduction with the thicker equivalent thickness in both shielding materials. Dose reduction was the highest at 0.5 mm equivalent thickness for both materials; lead shielding reduced the dose by 91% and 83%, the antimony-bismuth shielding by 90% and 86%, during the axial and helical head CT protocols, respectively. Statistically significant differences were found between the materials of the same equivalent thickness (0.175, 0.25 and 0.5 mm) during the helical protocol in favor of the antimony-bismuth shielding. During the axial protocol there were no statistically significant differences. Shielding of radiosensitive organs can prevent unnecessary exposure of radiosensitive organs outside the primary beam. Due to the significant decrease in radiation dose to the breasts, and many other positive attributes, use of the antimony-bismuth shielding instead of the lead shielding should be considered, especially during the helical CT scan of the head.

Establishment of national diagnostic reference levels for radiotherapy computed tomography simulation procedures in Slovenia.

PURPOSE: To propose national diagnostic reference levels (DRLs) for radiotherapy (RT) computed tomography (CT) localization purposes, compare both CT units used in the largest RT department in the country and to compare gathered results with other published DRLs in order to discover any need of optimization. METHODS: In total, 1631 patient data (time spend of 4 months) regarding sex, examination type, total dose-length product (DLP) and CTDIvol was collated on two CT units. Those simulation procedures account for more than 80 % of all simulation procedures performed nationwide. Then, total DLP and CTDIvol was calculated and mean, median and 3rd quartile for both units together were presented to determine national DRLs for simulation procedures. The same data was later compared between both units to discover any potential need for optimization. RESULTS: 3rd quartile values of DLP for abdomen, breast, chest, head, head and neck, pelvis and spine were 1116.2, 606.6, 832.4, 1942.4, 969.2, 677.1 and 1042.4 mGy∙cm, respectively. 3rd quartile CTDIvol values for the same sequence of procedures were 18.7, 13.3, 19.2, 76.9, 22.6, 17.9 and 22.2 mGy, respectively. Among the two units, the mentioned dose values were on average significantly higher on one CT unit than on the other unit. CONCLUSIONS: When comparing collected dose values with other studies, RT CT DRLs showed that radiation doses from our institution were similar or even lower. Some variations were found between both CT units in certain protocols, so exposure parameters should be reviewed and optimized.

RADIATION DOSE DURING PELVIC RADIOGRAPHY IN RELATION TO BODY MASS INDEX.

The purpose of this research was to investigate the impact of body mass index (BMI) on dose area product (DAP), effective dose (E), dose to the organs and image quality (IQ) on 200 patients referred to pelvic radiography. Patients were classified into three groups according to BMI: normal (<24.99), overweight (25.0-29.99) and obese (>30). The results showed 52% and 135% higher DAP for overweight and obese patients compared to normal-weight patients (p < 0.001). A 46 and 123% rise of E for overweight and obese patients compared to normal-weight patients (p < 0.001) was discovered. Overweight patients received 37% higher dose and obese patients 107% higher dose to the organs compared to normal-weight patients. There were no statistically significant differences between IQ, except between normal weight and overweight patients. A strong correlation (r = 0.733) was found between BMI and DAP and between BMI and E (r = 0.776).

A PHANTOM STUDY SHOWING THE IMPORTANCE OF BREAST SHIELDING DURING HEAD CT.

This study aimed to investigate the dose to the breasts during head computed tomography (CT) if lead shielding is used. The study was performed in two major hospitals using helical and axial protocols on an anthropomorphic phantom. Measurements were performed with and without the use of a lead shield of 0.5 mm equivalent density. The results showed a significant decrease in dose with the lead shielding in both hospitals. During the helical protocol, the use of shielding significantly reduced the dose by 96% in Hospital A and 82% in Hospital B. The dose reduction during axial protocol was also significant: 95% in Hospital A and 86% in Hospital B with lead shielding. Considering the significant dose reduction of 82% up to 96% during this study, we highly recommend the shielding of breasts regardless of the protocol used during head CT examinations.

Efficacy of breast shielding during head computed tomography examination.

BACKGROUND: Female breasts are exposed to scattered radiation regardless of not being included in the primary field during head CT. This study aimed to investigate whether the use of lead shielding is beneficial in dose reduction to the breasts during head CT. PATIENTS AND METHODS: The study was performed in two different hospitals on two different CT units and included 120 patients. Half of the measurements (n = 60) was conducted without the use of lead shielding and the other half (n = 60) with the use of lead shielding of 0.5 mm equivalent thickness. RESULTS: Significant skin dose reduction to the breasts during head CT in both hospitals with the use of lead shielding was discovered; 81% (338.2 ± 43.7 µGy to 64.3 ± 18.8 µGy) in Hospital A and 74% (from 253.1 ± 35.1 µGy to 65.3 ± 16.9 µGy) in Hospital B. CONCLUSIONS: Considering the assumed carcinogenic effect of low doses of radiation, high frequency of the head CT scans and the significant reduction of radiation doses to the highly radiosensitive breasts, the use of lead shielding is highly recommendable.