A PET-CT scan for lymphoma involves exposure to radiation from two sources: the PET component and the CT component. The PET scan uses a radioactive tracer, typically fluorodeoxyglucose (FDG), which emits positrons detected by the scanner, while the CT scan uses X-rays to provide detailed anatomical images. Together, these provide both metabolic and structural information crucial for lymphoma diagnosis, staging, and treatment monitoring.
The amount of radiation from a PET-CT scan for lymphoma varies depending on factors such as the tracer dose, the CT scan protocol, and the patient’s size. Generally, the **radiation dose from the PET part alone is about 5 to 7 millisieverts (mSv)**. This dose comes from the radioactive tracer injected into the patient, which emits radiation as it decays inside the body. The **CT scan adds an additional dose, typically ranging from 2 to 10 mSv**, depending on the body region scanned and the CT settings used. When combined, a PET-CT scan usually results in a total radiation dose of **around 10 to 25 mSv**.
For lymphoma patients, especially those undergoing multiple scans during diagnosis and treatment follow-up, this radiation exposure is a significant consideration. Lymphoma often requires repeated imaging to assess disease extent and response to therapy, which can increase cumulative radiation dose. However, advances in imaging technology and protocols have aimed to reduce this exposure. For example, new total-body PET scanners with higher sensitivity can reduce the tracer dose by up to 90% without compromising diagnostic accuracy, significantly lowering radiation risks for patients, including children and pregnant women.
In clinical practice, the tracer dose for FDG PET in lymphoma is often calculated based on body weight, commonly around 3 to 5 megabecquerels per kilogram (MBq/kg). Recent research has shown that doses as low as 0.25 to 1.0 MBq/kg can still provide reliable imaging results when using advanced scanners. This means that radiation exposure from the PET component can be minimized while maintaining the ability to detect lymphoma lesions and evaluate treatment response effectively.
The CT portion of the PET-CT scan can be performed with different protocols depending on the clinical need. A low-dose CT is often used for attenuation correction and anatomical localization, contributing less radiation (around 2-4 mSv). If a diagnostic-quality CT is needed, the dose may be higher (up to 10 mSv or more), but this is balanced against the clinical benefit of detailed anatomical information.
To put these doses in perspective, the average annual background radiation exposure from natural sources is about 3 mSv. A single PET-CT scan for lymphoma can thus represent several years’ worth of natural background radiation. Despite this, the benefits of accurate lymphoma staging and monitoring generally outweigh the risks associated with radiation exposure, especially when scans are optimized to use the lowest effective dose.
In summary, a PET-CT scan for lymphoma typically involves a total radiation dose in the range of 10 to 25 mSv, with the PET component contributing about 5 to 7 mSv and the CT component adding 2 to 10 mSv depending on the protocol. Advances in PET technology and low-dose CT protocols are helping to reduce these doses, making PET-CT a safer and more effective tool for lymphoma management.
