Resources for virtual dose mapping

Frequently asked questions

What is dose mapping?

Dose mapping refers to the experimental measurement of the dose distribution delivered during radiation sterilization, as required by ISO 11137. Practically, this measurement is performed by affixing multiple dosimeters to your packaged device, exposing the device to radiation, and then reading the dose measured by the dosimeters. Because dose mapping requires physical devices, it can only occur after the device has been fully designed, packaged, and manufactured.

What is virtual dose mapping?

Virtual dose mapping uses computer modeling to predict the dose distribution that would be delivered during radiation sterilization. Unlike experimental dose mapping, which can only occur after a device has been fully designed and manufactured, virtual dose mapping can be performed as soon as a preliminary CAD model exists. Because of this, it can be performed early in the product development cycle, which allowed medical device manufacturers to unlock the time and cost savings offered by Design for Sterilization.

How long does virtual dose mapping take?

Another thing that sets virtual dose mapping apart from experimental dose mapping is the quick turn around time. Our simulations take a few hours to run, so you can expect a completed dose report in a day or two. This allows you to iterate on design choices quickly, which accelerates your design process and reduces your time-to-market.

What is Design For Sterilization?

Design for Sterilization (DFS) is the process of designing medical devices and packaging with sterilization in mind in order to make sterilization validation easier. Virtual dose mapping is a tool that can be used for DFS by studying the effect of design choices on the dose distribution that will be delivered during radiation sterilization. Design for Sterilization is part of the concept of Design for X, which includes Design for Manufacturing (DFM), Design for Assembly (DFA), and Design for Inspection (DFI).

How does Dose Insight do virtual dose mapping?

Dose Insight calculates virtual dose maps using the Monte Carlo method, which has long been established as the “gold standard” in the scientific community for producing accurate and precise predictions of radiation dose. Specifically, our simulations use the Monte Carlo toolkit Geant4, which has been developed by an international collaboration of physicists to ensure that it contains the most up-to-date understanding of radiation-matter interactions.

Can I trust virtual dose mapping?

Yes you can! In the words of the Nobel Prize-winning physicist Richard Feynman,

If it disagrees with experiment, it's wrong. In that simple statement is the key to science.

True to that sentiment, we have extensively validated our simulation technology so that you know you can trust the virtual dose maps produced by Dose Insight. Check out our validation data to see for yourself!

Do I need to be an expert in radiation simulations to work with Dose Insight?

Absolutely not! Our team of physicists will leverage their expertise in radiation physics and high-performance computing to run the virtual dose mapping for you. Just as you would go to a contract sterilizer for dose mapping measurements, come to Dose Insight for virtual dose mapping! We are the experts in virtual dose mapping so you don't have to be!

What information do I need to get started with virtual dose mapping with Dose Insight?

To run the virtual dose mapping simulations, we need you to provide us with the following:

A CAD model of your device/packaging. We accept CAD files from all major vendors.
The names of all the materials you are using. This could be included in the CAD model, or as a separate BOM. If this is a preliminary design, don't worry if your material choices aren't finalized yet; we can work with you to make some educated guesses.
Information about your e-beam sterilization facility, such as the beam energy. Again, if you haven't chosen a beamline yet, no problem! We have validated models of beamlines from many popular contract sterilizers, and can use a universal beamline model if you are still early in your vendor selection process.

Validation data

Virtual dose mapping is a predictive technology, and we want to make sure all our customers feel as confident in virtual dose mapping as we do. As such, we have performed a series of validation experiments, some of which are described below.

Aluminum wedge

ISO/ASTM 51649 describes the standard way that qualification and routine processing is performed at e-beam sterilization facilities. In it is a description of how to measure the energy of the e-beam source by sandwiching a film dosimeter between a pair of aluminum wedges.

We replicated this experimental geometry in Dose Insight's virtual dose mapping tool in order to compare the simulated dose-depth curve with that measured at a 7.5 MeV e-beam facility.

We found excellent agreement between the simulated and measured dose-depth curves, with the simulated curve entirely contained within the experimental uncertainty (shown as the colored band in the figure below). The most probable energy calculated from the measured and simulated dose depth curves agreed with a <1% relative difference. This speaks to the predictive power of virtual dose mapping.

Acrylic cylinder

A cylinder is a simple shape that results in a surprisingly complex dose distribution! We affixed two rows of film dosimeters around the outer surface of an acrylic cylinder, and then irradiated it with a one-sided, 10 MeV e-beam.

We found considerable variation in the dosimeter measurements, especially near the sides of the cylinder where the dose gradients are large.

Dose profiles around the outer surface of an acrylic cylinder irradiated by a 10 MeV e-beam as measured and simulated by Dose Insight's virtual dose mapping tool

Acrylic steps

We designed an acrylic step phantom and irradiated it from the top with a one-sided, 10 MeV e-beam. Two dosimeters were affixed to each step at the locations of the yellow squares shown below.

We observed that the dose increased with higher steps, but then suddenly decreased for the top step. This is due to the fact that the lower steps receive scatter from adjacent steps, whereas the top step does not have a nearby wall to receive scattering from. Again, the simple geometry lead to a surprisingly complex dose distribution, which speaks to challenges of using rules-of-thumb when deciding the best sterilization configuration for medical devices, which have considerably more complex geometries.

Dose delivered to an acrylic step phantom as measured at a 10 MeV e-beam sterilizer and simulated by Dose Insight's virtual dose mapping tool

Use cases

Curious to know more? Take a look at some of our white papers, or get in touch if you have any questions.

Optimizing the sterilization process with virtual dose mapping	Read
Saving time and money with Design for Sterilization	Read