© Borgis - Postępy Nauk Medycznych 4/2017, s. 233-236
*Tomasz Roman1, Maciej Szajner1, Klaudia Karska1, Justyna Markowicz-Roman2, Katarzyna Hać1, Ewa Kramarz1, Łukasz Światłowski1, Małgorzata Szczerbo-Trojanowska1
Radiation exposure in interventional neuroradiology
Narażenie na promieniowanie rentgenowskie w neuroradiologii interwencyjnej
1Department of Interventional Radiology and Neuroradiology, Medical University in Lublin
Head of Department: Professor Małgorzata Szczerbo-Trojanowska, MD, PhD
2Department of Clinical Immunology, Medical University in Lublin
Head of Department: Professor Jacek Roliński, MD, PhD
Streszczenie
Ciągły rozwój neuroradiologii interwencyjnej wpływa na wzrost liczby procedur, a także w niektórych przypadkach na wydłużenie czasu zabiegów. Istnieje szereg czynników mogących wpływać na całkowite narażenie na promieniowanie rentgenowskie podczas neuroembolizacji. Obserwuje się różne skutki uboczne, pojawiające się w zależności od dawki oraz czasu narażenia. W tym opracowaniu przeglądowym pod uwagę będą brane sposoby pomiaru dawki właściwe dla ramienia C. Zrozumienie ich rodzajów, definicji oraz zastosowań praktycznych jest bardzo istotne dla operatora przy ocenie i kontroli narażenia pacjenta na promieniowanie rentgenowskie. Ważne jest także dokumentowanie dawek, nie tylko w celu świadomego zwiększania bezpieczeństwa pacjenta, ale także jako informacji zwrotnej dla lekarza. Ocena trudności zabiegu powinna zawierać także szacunkową ocenę pod kątem możliwego ryzyka związanego z promieniowaniem. Operator powinien mieć także podstawową wiedzę w zakresie epidemiologii chorób związanych z narażeniem na promieniowanie rentgenowskie.
Summary
Constant development of interventional neuroradiology procedures increases number and sometimes length of vascular interventions. There are several factors that have impact on total radiation dose during neuroembolization. Reaction of human body to radiation exposure may be different. In general, it depends on severity of exposure and time in which it occurs. In this review, only dose measurements applicable for C-arm devices will be taken for consideration. There are several methods for x-ray use assessment during interventional neuroradiology procedures. This is important for operating physician to understand their definitions and practical implications for most appropriate dose control during procedures. Most important reasons for recording of patient dose are patients safety and dose optimization as a feedback to the operator. The procedures with potentially high dose risk may be enlisted and performed with greater awareness. Increasing awareness of epidemiological data on radiation-induced diseases should improve dose management.
Introduction
Interventional neuroradiology is fast developing branch of medicine providing various endovascular techniques for treatment of brain vascular diseases. Both materials and radiological equipment are constantly improving. However, the risks connected with exposure to radiation are still important limitation of such approach.
There are several factors that have impact on total radiation dose during neuroembolization. Those may be related directly to patient or to operating techniques and equipment. They are summarized in table 1. Increasing awareness of side effects of radiation and undertaking efforts to optimize x-ray use is important part of radiologists practice.
Tab. 1. Risk factors concerning radiation of interventional neuroradiology patient
| Radiation risks related to patient | Radiation risks related to operating techniques and equipment |
| Age | Position of a table |
| Sex | Collimation |
| Weight | Frames per second |
| Prior history of radiation | Image quality presets |
| Specific area – brain, covered with skull | Area of imaging |
| | Biplane vs monoplane, including overlying of fields |
| | Learning curve |
Effects of radiation
Reaction of human body to radiation exposure may be different. In general, it depends on severity of exposure and time in which it occurs. For academic purposes, these health consequences may be divided into stochastic and deterministic effects. The severity of stochastic effects does not depend on total dose absorbed, but the chance of incidence increases along with amount of radiation. The key examples of stochastic effects of radiation are cancers, in that case as radiation-induced. Deterministic effects, in the other hand, are correlated positively with received dose. The threshold dose can be defined for them, keeping in mind that it can be variant depending on particular cases. After exceeding a individual threshold level, damage appears accordingly to increasing dose. Most common deterministic effects to observe in neuroradiology suite are skin injury, hair loss and erythema.
Dose measurement
In this review, only dose measurements applicable for C-arm devices will be taken for consideration. There are several methods for x-ray use assessment during interventional neuroradiology procedures. This is important for operating physician to understand their definitions and practical implications for most appropriate dose control during procedures.
The fluoroscopy time, as well as total images count may be related to patient dose, but they can vary between different procedures with the same effective dose. Information about fluoroscopic dose rate and the dose per image must be also provided. The fluoroscopy time and fluoroscopic images count are considered to be least relevant for dose monitoring.
Kerma-area product (PKA) is another commonly available indicator for most of the angiographic suites. It is defined as “integral of air kerma across the entire x-ray beam emitted from the x-ray tube” (1). PKA is measured in Gy·cm2. The scatter is usually not included in the given value, which is usually measured by fluoroscope. This value represents total radiation energy entering the patient. It is approved by International Commission on Radiation Units and Measurements (ICRU) commission as indicator of future probability of stochastic effects to the patient. There are observations proving that PKA correlates also with staff dose. However, this parameter is not considered to be good indicator of deterministic effects.
Reference air kerma (Ka,r), also know an reference point air kerma (called cumulative dose or cumulative air kerma) represents air kerma that is being concentrated at the interventional reference point. This radiation measurement does not include backscatter from the patient. The value is given in Grays (Gy) and it can be measured by most fluoroscopic units. The interventional reference point (also known as patient entrance reference point) for C-arm is located 15 cm from its isocenter towards the x-ray tube. The Ka,r is considered to be an estimation value for skin dose, however some observations suggests that it may overestimate the risks (2). Important limitation there is that the interventional reference point may be located at different distance from the patient’s skin, depending on the table height, beam angle, as well as dimensions of current individual. This is main source of estimation while using Ka,r as skin dose measurement.
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Piśmiennictwo
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3. National Council on Radiation Protection and Measurements. Radiation dose management for fluoroscopically guided interventional medical procedures. Report No. 168. Bethesda, MD: NCRP, 2011.
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8. European Commission. COUNCIL DIRECTIVE 2013/59/EURATOM of 5 December 2013 laying down basic safety standards for protection against the dangers arising from exposure to ionising radiation, and repealing Directives 89/618/Euratom, 90/641/Euratom, 96/29/Euratom, 97/43/Euratom and 2003/122/Euratom. Available at http://eur-lex.europa.eu/legal-content/EN/ALL/?uri=OJ:L:2014:013:TOC Accessed February 27.09.2014.
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12. National Council on Radiation Protection and Measurements. Radiation Dose Management for Fluoroscopically-Guided Interventional Medical Procedures. Bethesda, Maryland: National Council on Radiation Protection and Measurements; 2010. NCRP Report No. 168.
