The Critical Difference: Why In-Water Dose is the Gold Standard

In the world of clinical research, precision is paramount. Every variable, from the test article's concentration to the environmental temperature, is meticulously controlled. Yet, when it comes to small animal irradiation in a preclinical setting, a critical variable is often overlooked: the dose.

Many irradiators are calibrated to measure dose "in-air," also known as air kerma. This is a great starting point, but it's not the full story. The true dose that impacts your research is the absorbed dose delivered to the animal's tissues, which is a fundamentally different measurement.

In-Air Dose (Air Kerma): The Starting Point

Imagine a radiation beam hitting an empty space. In-air dose, or air kerma, measures the kinetic energy released in air by the beam. This measurement is easy to perform and is useful for initial machine commissioning and quality assurance.

However, air kerma has significant limitations for biological studies. It doesn't account for how the radiation interacts with a living organism. When a beam enters an object like a mouse, it's affected by:

• Scatter: Photons bounce off tissue and into other areas, increasing the dose to surrounding organs.

• Attenuation: As photons pass through tissue, they lose energy, reducing the dose at deeper points. This also includes inherent filtration of the x-ray tube itself or the containment used to hold the mice in the irradiator.

• Absorption: The energy transferred to the tissue is what causes the biological effect. Air kerma doesn't measure this directly.

Because of these interactions, the dose delivered "in-water" (or in-tissue) is always different from the dose measured "in-air."

In-Water Dose: The Biologically Relevant Measurement

In contrast, in-water dose measures the energy that is actually absorbed by a material that closely mimics the properties of living tissue. Water is the international standard for this type of measurement because its density and atomic composition are very similar to soft tissue.

When you measure in-water dose, you are accounting for the real-world effects of scatter and attenuation. This gives you a true picture of the absorbed dose, which is what actually causes the biological response in your preclinical study. The goal of a radiobiology experiment is not to deliver a certain dose to air, but to a specific organ or tumor within the animal.

The Dosequate™ Advantage: Bridging the Gap

This is precisely where the Dosequate™ system excels. It moves beyond theoretical calculations and in-air measurements to provide a biologically relevant dose. By using 3D-printed murine phantoms made of tissue-equivalent materials and embedding alanine dosimeters at specific organ locations, our system directly measures the absorbed dose where it matters most.

This approach gives you:

• Confidence in your data: You know the exact dose delivered to the target.

• Reproducibility: You can replicate the exact dose and geometry for future studies.

• Intercomparability: You can confidently compare your results with other labs using the same Dosequate™ system.

While in-air dose has its place for machine checks, relying on it alone is like planning a journey by just looking at a map and ignoring the road conditions. For accurate, repeatable, and publishable research, the true gold standard is an in-water or in-tissue absorbed dose. Dosequate™ provides this critical measurement, ensuring your research is as reliable as it can be.