8th Baltic Congress of Radiology

Radioprotection and management

oral abstract

It is well known that diagnostic and interventional X-rays represent the largest portion of radiation exposure from artificial sources to the general population. Since these exposures are associated with small but significant stochastic risk in the long term, the International Commission on Radiological Protection (ICRP) recommends the application of the following radiation protection principles: justification of exposure and optimization of radiation procedures in order to keep dose “as low as reasonably achievable”. The diagnostic reference level (DRL) provide an efficient tool for optimization of diagnostic procedures and protection of patients against high level of radiation. DRLs does not represent limit values but rather an upper reference values guiding optimization of patient doses without jeopardizing image diagnostic quality. In Vilnius University hospital Santaros klinikos (VUHSK), second biggest hospital in Lithuania, a large number of diagnostics, together with interventional and nuclear medicine procedures are performed annually. The purpose of this study was to evaluate the most common radiological examinations and to check compliance with national diagnostic reference levels (DRLs) when available.

More than 5000 diagnostic procedures performed in 2021-2022 (2200 interventional, 90 fluoroscopic, 1600 pediatric and adult radiology, and 1500 pediatric and adult Computed tomography) were included in this study. Data collection was carried for seven angiography/angioplasity procedures (from six systems), twelve conventional radiology protocols (from five systems) and five CT protocols (from 3 systems). For adult procedures, patients of all weight were included in setting local DRL. The pediatric population was grouped into four age intervals: 0 - < 1, 1 - < 5, 5 - < 10 and 10 - < 15 years. Radiographic systems from all four major vendors: Siemens, Philips, General Electric, Shimadzu were included in data analysis. Local DRL were set as the 75th percentile of the distribution of the following dose-related parameters (depending on the type diagnostic procedure): dose area product (DAP), volume computed tomography dose index (CTDIvol), dose length product (DLP), entrance surface dose (ESD) and fluoroscopy time (FT) as recommended by the European commission and Radiation Protection Centre in Lithuania. Statistical analysis was performed in order to compare exposure dose and time between radiographic equipment for each protocol. For interventional procedures, dependence of patient exposure dose and time on performing radiologist was evaluated. Differences between medians were estimated using Kruskall-Wallis non-parametric test with follow-up pair wise comparison with MannWhitney test. Differences were considered statistically significant for p-value < 0.05.

According to European Directive 97/43/Euratom, adult DRL should be established for standard weight patient (70±5kg). However, in this study, patient weight and height were not registered in 70% of the procedures which prompted setting DRLs without any size consideration. Nevertheless, in order to reduce interindividual influence on collected doses, a large sample size of ≥30 patient was included. It is recommended to compare established local DRLs against national DRLs in order to evaluate the level of patient radiation protection in the involved hospital. Although Lithuanian DRL are not currently established for all radiography procedures included in this study, most procedures had a dose lower than Lithuanian DRLs. Higher incompliance was found within pediatric conventional chest and head protocols where automatic exposure control was not used routinely and a strong correlation was found between patient doses and the radiographer who performs the examination. Direct comparison of same protocol indicated a significant difference in patient doses for different equipment. Similarly, in case of interventional radiology, patient doses and procedure time were highly dependent on performing radiologist. In Computer tomography limitation is related to the difference in methodology used in estimating local DRL as opposed to Lithuanian DRLs. In Lithuanian, DRLs in CT are only set for single-phase examination with non-contrast. However, in this study dose of multiphase examination related to a single clinical indication was evaluated.

Setting DRL can be a cumbersome and time-consuming task since it should cover a large number of diagnostic procedures in different hospital departments. However, it helps identify inconsistency in radiation exposure between different equipment and keep patient doses as low as possible. Local DRLs were set for most common diagnostic procedures performed at VUHSK. Protocol with higher than recommended doses will be re-evaluated in the near future after providing additional training of personnel and adjusting exposure parameters whenever needed.

The purpose of this study was to evaluate the most common radiological examinations and to check compliance with national diagnostic reference levels (DRLs). Local DRLs were set for most common diagnostic procedures performed at Vilnius University hospital Santaros klinikos. Protocol with higher than recommended doses will be re-evaluated in the near future after providing additional training of personnel and adjusting exposure parameters whenever needed.

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