Hi there, I am going to illustrate in a series of posts some medical applications of technologies developed for particle physics. How do I know about this? Well, my most exciting job during my time at CERN was being the Head of Knowledge and Technology Transfer. My mission was to demonstrate that technologies developed for exotic experiments at CERN could yield real, tangible benefits to mankind.
Not an easy job, since CERN is funded out of taxpayer's money from its Member States…
In times of economic recession, people and politicians would (legitimately ) ask why funding the quest for the Higgs boson should have higher priority than welfare, or other real-world issues. Luckily, I had plenty of arguments to defend CERN funding, because it turns out that there are plenty of technologies developed in the context of particle physics which are saving lives as we speak!
To illustrate this, let's first understand what happens in physics experiments such as the Large Hadron Collider at CERN. Broadly speaking, the logic is quite simple, kind of brute force-driven: we make protons collide with each other as hard as possible. We smash them, and take "pictures" of the fragments and debris.
The smashing part is accomplished at CERN by accelerating two beams of protons and make them run in opposite directions inside a 27-kilometre long circular ring lying some 100 meters underground. It's like two trains running like crazy in opposite directions on parallel rails.
At some point, (I am sure you guessed it) we let the trains collide :)
Collisions are engineered to take place in specific points, where huge structures, called detectors, are ready to take "pictures" of the collision events.
Now, I hear you...“So, what? How on earth is all this saving lives...?”
Well, it’s the know-how developed in this context which does. Accelerator know-how delivers innovative cancer treatments, while detector know-how delivers advanced medical imaging devices.
Here we'll dig a little bit into the first item….
Hadron Therapy
Radiation therapy is the medical use of ionizing radiation to treat cancer, by destroying tumor cells. Traditionally, this is accomplished by using beams of X rays, i.e. high-energy photons.
One problem with the traditional approach is that the X-ray beam travels across our body and deposits most of its energy below the skin surface and in healthy tissues in front and behind the target tumor. So, the tumor gets bombed, but we also generate a lot of “collateral damage”, if you see what I mean.
Conversely, if you hit the body with a beam of hadrons (protons, or carbon ions), it is possible to fine-tune the depth range where most of the energy is deposited, so that damage to healthy tissues is greatly reduced. This is shown in the picture below, referring to the treatment of a tumor located near the centre of the skull and comparing photon and proton irradiation patterns.
Image credit: Leroy R, Benahmed N, Hulstaert F, Mambourg F, Fairon N, Van Eycken L, De Ruysscher D. Hadron therapy in children – an update of the scientific evidence for 15 paediatric cancers – Synthesis. Health Technology Assessment (HTA) Brussels: Belgian Health Care Knowledge Centre (KCE). 2015. KCE Reports 235Cs.D/2015/10.273/03
In physics terms, the difference between the behavior of photon and hadron beams in the human body is described through the Bragg peak.
The picture below shows energy deposition vs. depth in the body for a photon beam (red line) and different hadron beams (blue lines). Each hadron beam graph has a sharp peak (the Bragg) peak at a specific depth, so by using multiple hadron beams of different energies one can effectively irradiate the region where the tumor is located and spare most of surrounding (healthy) tissues. In the picture you can see the aggregate, spread out Bragg peak (SOBP, dashed blue line) obtaining by using 12 hadron beams to span the region where the tumor is located.
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Clearly, this approach is particularly promising for tumors which are located deep inside the body and, generally speaking, for the treatment of children, since for them it is essential to minimize the probability of side effects over time related to “collateral damage”…
The idea of using protons for cancer treatment was first proposed in 1946 by the physicist Robert Wilson, who later became the founder and first director of the Fermi National Accelerator Laboratory (Fermilab) near Chicago. Today, there are over 50 hadron therapy facilities worldwide.
To the best of my knowledge (I am by no means a technical expert), today there is still no conclusive clinical evidence regarding the advantages of hadron vs. photon irradiation. One factor to keep into account is that hadron treatments are, generally speaking, more expensive, and this element clearly affects the cost vs benefits debate.
There are a number of other exciting health applications of particle physics technologies which I plan to discuss (very informally and superficially...) here. One topic which Steemers might like in particular is the need for Big Data solutions in the analysis of clinical data, e.g. when analyzing patient and tumor data and dose arrays in order to correlate them with clinical outcomes…
To be continued :-)