What Is 15O-Water, and Why Is MedTrace So Eager to Make It Available in Clinical Practice?

1 Xie et al Med Phys. 2015 Jun; 42(6): 2955–2966; 2 Carpeggiani et al BMC Cardiovascular Disorders (2017) 17:63

MedTrace’s Senior Scientist, Hans Harms, Ph.D., explains.

15O-water is a radiotracer, a radioactive compound, that doctors may inject into patients to diagnose various diseases by, for example, following the flow of blood or the use of sugar in organs. In other words, 15O-water makes it possible to look and measure inside the body.

At MedTrace we find 15O-water particularly interesting because the short half-life means that if you need to do more than a single scan, as is the case in cardiology, you can quickly start the second scan because the signal of the first scan disappears so fast. In addition, the patient radioactivity dose for 15O-water is the lowest achievable and down to 0.4 mSv pr. scan, according to The U.S. Nuclear Regulatory Commission (mSv stands for millisievert and it is the unit that we measure radioactivity in).

In cardiology, healthcare professionals make use of many different procedures such as CT angiography, PET, SPECT, and invasive tests (ICA), and the approach in any medical field is always, the lower the amount of radiation the better.

In the below, I have compared the radiation dose of an injection of 15O-water with other procedures used in cardiology and with radiation in daily life, to illustrate how low the dose of 15O-water is.  

To create the figure above, I used the doses documented by Xie et al in the scientific article “Assessment of Radiation Dose in Nuclear Cardiovascular Imaging Using Realistic Computational Models” published in Medical Physics in 2015 and doses documented by Carpeggiani et al in the scientific article “Variability of radiation doses of cardiac diagnostic imaging tests: the RADIO-EVINCI study (RADIationdOse subproject of the EVINCI study)” published in BMC Cardiovascular Disorders in 2017.

In the figure you can see how the dose of a single injection of 15O-water compares to that of other commonly used PET tracers or cardiac procedures.

Using the references mentioned above to create this figure, it becomes very visible that the radioactive exposure from 15O-water is 17 times lower than SPECT, which is a technology widely used today.

To put the radioactivity from tracers and technologies used in cardiology into perspective, it is worth noticing that the average total radiation dose in a year for a U.S. citizen, including from human sources, is 6.2 mSv, according to The U.S. Nuclear Regulatory Commission. This is the same as fourteen 15O-water injections.

In addition, people are exposed to additional radiation during air travel, with one 15O-water injection being equal to about six return flights from London to New York (Health Physics Society).

All tracers (and many other items around us) come with a radiation dose, but the dose of 15O-water is much lower than all other tracers used in cardiology.

And that is one of the reasons that MedTrace is so eager to make it available in clinical practice.

MedTrace is developing a solution for manufacturing 15O-water right next to the patient which makes it possible to inject a specific volume of the tracer at a controlled level to the patient. This method also ensures that any potential exposure to the personnel performing the procedure is completely avoided.

MedTrace has an ongoing phase III clinical trial that seeks to evaluate the diagnostic accuracy and safety of  using 15O-water as a myocardial perfusion PET imaging agent.