Why Synchrony? “Every breath you take, and every move you make, every bond you break, every step you take I'll be watching you.” The Police.

Have you ever really thought about breathing? Unless you are in a Yoga class, Freediving or just completed a Marathon, the thought of your breathing never crosses your mind, yet breathing is an intricate collaboration of muscles, organs and tissues and the motion of breathing is much more complicated than you may imagine.

If you have ever taken anatomy 101, you have seen a cartoon image of the lungs, maybe even in a video where the lungs expand and contract. This would make you think that this is all there is too it, but what about the motion of the curved diaphragm pushing the air in and out as we inhale and exhale, or the ribcage expanding and contracting, not to mention the heart, esophagus trachea, major veins and arteries that all cause changes to what we perceive as a simple in and out motion. All this impacts motion with the lobes of the lung and this motion can be completely different dependent on the lobe and location.

This does not even begin to consider our current disposition. All these motions can be impacted by whether we happen to be nervous or relaxed.

With all things considered, you can imagine that the motion of a lesion can be dramatically different based off its size and location within the lung, and this motion can change in a matter of moments based off anything from the rapidity of breathing, the speed of the heart beating, swallowing just to name a few.

The average number of breaths in a minute is sixteen, and the heart beats at about eighty beats per minute, so during a course of a fifteen-minute treatment there is at minimum over fourteen hundred opportunities from these two actions alone to impact the motion happening within your lungs.

In general, a lesion in a lower lobe can and will move in an almost elliptical bi-curvilinear pattern that can change on its axis, while a lesion near the axilla may only move several millimeters in an inferior/superior motion, but this is in general. You really will not know the overall motion of a lesion until you are tracking it.

In Radiation Oncology today there are currently three clinical practices to combat this motion. The first one is to simply determine where a lesion is at exhale and inhale, then add a margin and treat the entire range. As you can imagine, this will hit the target but is more like shooting a squirrel with a sawed-off shotgun. Sure, you will kill the squirrel, but what about the damage to the tree?

The other method, fortunately more popular, is gating. Gating allows the beam to turn on and off based off the perceived location of the lesion located on a breath hold CT scan, but unless you are using an MR based system, you are making an assumption that the location you planned is where the lesion happens to be. In either instance you are still creating a larger treatment volume to make up for the unknown variability, and even in the case of the MR based system, if you see the motion has changed or the lesion has deformed you need to wait until this change has subsided.

That is where Synchrony? comes in. With Synchrony, only available on the CyberKnife? and Radixact? systems you build a model based off of the motion of the chest and the real-time position of the lesion, and the model allows for the dose to move with the lesion in real-time, eliminating the need to irradiate considerable healthy tissue, completing the treatment in an efficient manner that eliminates the need for waiting for the motion to subside. It is true artificially intelligent, real time adaptive technology that allows the clinician to treat with reduced margins by teaching a system how a patient breathes, but it even goes beyond that.

New images of the lesions position are taken throughout the course of the treatment, and with a first in/ first out methodology is correlated to the current breathing motion, allowing the system to adjust and correct throughout the course of the treatment ensuring the dose is going to exactly where it needs to be.

You would think that would be enough, but the system goes one step further. It is using this continuously updated model to adjust and compensate for the motion, but since it is a model if there is a change in the external respiratory motion the systems takes this into account and will move the entire model to compensate for it, making the model truly dynamic in nature confirming the dose you prescribed is delivered exactly where you wanted to submillimeter accuracy every time the beam turns on.

Let us face it, unfortunately if your patient has been diagnosed with lung cancer there is most likely another underlying condition, be it emphysema, COPD or any other of a number of lung complications that initially led them to see a pulmonologist in the first place. Their breathing is more than likely already compromised and as a result need every bit of healthy lung tissue they can spare. What these patients need is Synchrony.

Please feel free to reach out me to find out more about how Synchrony can effectively handle motion throughout the treatment process.

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*The statements on this site are my own and do not represent Accuray opinions or positions.

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