From the Guidelines
X-ray radiation is measured using the parameter air kerma, which is the standard unit of measure for x-ray beam exposure, and is typically expressed in units of Gray (Gy) or milliGray (mGy). The Gray measures the absorbed dose of radiation, representing the energy deposited in tissue (1 Gy = 1 joule/kg) 1. In medical settings, air kerma is used to assess the level of radiation present at a location, and is measured using devices such as dosimeters, ionization chambers, and digital detectors 1.
Key Metrics for Measuring X-ray Radiation
- Absorbed dose: measured in Gray (Gy) or milliGray (mGy), representing the energy deposited in tissue
- Equivalent dose: measured in Sievert (Sv) or milliSievert (mSv), accounting for biological effects by applying radiation weighting factors to the absorbed dose
- Air kerma: measured in Gray (Gy) or milliGray (mGy), assessing the level of radiation present at a location
- Effective dose: measured in milliSievert (mSv), calculating the whole-body quantity used to roughly compare potential stochastic risks from different partial-body exposures 1
Importance of Accurate Measurement
Accurate measurement of X-ray radiation is crucial for ensuring patient safety by monitoring exposure levels and maintaining them within established limits 1. Medical facilities follow the ALARA principle (As Low As Reasonably Achievable) to minimize unnecessary radiation exposure while still obtaining diagnostically useful images. Regular calibration of X-ray equipment ensures accurate dosage delivery and measurement 1.
Current Recommendations
The American College of Radiology recommends expressing quantitative radiation dose values as dose estimates, and replacing the term dose with dose estimate in publications 1. A national database for radiation dose indices is also being developed to address the actual range of exposures for X-ray examinations.
From the Research
Measurement of X-ray Radiation
X-ray radiation can be measured using various techniques and devices, including:
- Dosimeters, which are used to measure the dose of radiation absorbed by an object or person 2, 3, 4
- Ionization chamber dosimeters, which measure the air dose at a distance from the central point of X-ray exposure 5
- Personal dosimeter devices, which are worn by individuals to record their total radiation exposure over time 4
Types of Dosimeters
There are different types of dosimeters used to measure X-ray radiation, including:
- Shallow dose equivalent (SDE) dosimeters, which measure the dose of radiation at a shallow depth 2
- Deep dose equivalent (DDE) dosimeters, which measure the dose of radiation at a deeper depth 2
- Real-time dosimetry monitoring systems, which provide immediate feedback on radiation exposure 3
Factors Affecting Radiation Exposure
Several factors can affect the level of radiation exposure, including:
- Distance from the radiation source, with closer distances resulting in higher doses 2, 5
- Type of X-ray procedure, with some procedures resulting in higher doses than others 3
- Use of radiation shields or protective clothing, which can reduce radiation exposure 3, 5
Importance of Accurate Measurement
Accurate measurement of X-ray radiation is crucial to ensure the safety of patients and medical staff, and to minimize the risks associated with radiation exposure 2, 3, 4, 6