Doctors measure how much radiation a patient can safely handle by carefully calculating and monitoring the radiation dose that the patient will receive, ensuring it stays within established safety limits designed to minimize harmful effects. This process involves understanding the type of radiation, the area of the body exposed, the patient’s health status, and the purpose of the radiation exposure, whether for diagnostic imaging or treatment like radiotherapy.
Radiation dose is measured in units called sieverts (Sv) or millisieverts (mSv), which quantify the biological effect of radiation on human tissue. To determine a safe dose, doctors rely on guidelines and limits set by radiation protection authorities, which are based on extensive research about how different doses affect the body over time. These limits vary depending on the context—medical imaging typically involves much lower doses than cancer treatments, which may require higher doses targeted precisely to tumors.
In medical imaging, such as X-rays or CT scans, doctors use devices that measure the amount of radiation emitted and absorbed. They use dosimeters—small devices that can be worn or placed near the patient—to directly measure exposure. These devices help ensure the dose is as low as reasonably achievable while still obtaining the necessary diagnostic information. The dose is carefully calculated based on the machine settings, the duration of exposure, and the specific body part being imaged.
For radiation therapy, where higher doses are used to kill cancer cells, the process is more complex. Doctors use sophisticated treatment planning systems that calculate the exact dose distribution needed to maximize damage to the tumor while sparing healthy tissue. These systems use detailed imaging data and computer models to simulate how radiation will travel through the body. Quality assurance procedures, including measurement-based and calculation-based checks, verify that the planned dose matches what the machine delivers. This ensures patient safety and treatment effectiveness.
Additionally, doctors consider patient-specific factors such as age, overall health, and previous radiation exposure history. They also use administrative controls like limiting the time a patient is exposed and increasing the distance from the radiation source when possible. In cases where radiation might be incorporated into the body (for example, radioactive tracers in nuclear medicine), specialized instruments measure radiation inside the body or in bodily fluids to estimate the internal dose.
Overall, the measurement and control of radiation doses in patients involve a combination of direct measurement tools, computational modeling, adherence to safety standards, and individualized clinical judgment to balance the benefits of radiation use against its potential risks.
