Sanjay Mehta, M.D.

So that's another thing that has changed. Now, essentially, when I say now, the last basically 30 years, most machines in the US are linear accelerators. So these are artificially generated x-rays. It's essentially accelerating electrons through a long vacuum tube, essentially an electron gun. And at the very end of the tube, you've got a tungsten target.

So that's another thing that has changed. Now, essentially, when I say now, the last basically 30 years, most machines in the US are linear accelerators. So these are artificially generated x-rays. It's essentially accelerating electrons through a long vacuum tube, essentially an electron gun. And at the very end of the tube, you've got a tungsten target.

And so the electrons hammer that target, and then they shower photons out. So you're generating the X-rays that way. And this has been done, actually, I think your alma mater, Stanford, had the very first one in the U.S., the medical linear accelerator. But prior to that, they were using these for atom smashers, and they have the gigantic machines that were used for physics.

And so the electrons hammer that target, and then they shower photons out. So you're generating the X-rays that way. And this has been done, actually, I think your alma mater, Stanford, had the very first one in the U.S., the medical linear accelerator. But prior to that, they were using these for atom smashers, and they have the gigantic machines that were used for physics.

But they started in London, I think, in 53. And then I think in the late 50s, Henry Kaplan at Stanford had the first one. So we're essentially still doing that even today, what, 70 years later. But the key difference is how we're able to shape those photons once they come out of the machine now. And so when the actual photons are coming out, they're completely unfiltered.

But they started in London, I think, in 53. And then I think in the late 50s, Henry Kaplan at Stanford had the first one. So we're essentially still doing that even today, what, 70 years later. But the key difference is how we're able to shape those photons once they come out of the machine now. And so when the actual photons are coming out, they're completely unfiltered.

It comes out in a cone shape and it diverges just as any light source would. You know how when you hold a flashlight to a wall, you get a nice precise circle. As you pull the flashlight away, it diverges. So we have filters and we have what's called the multi-leaf collimator that can actually shape the beam, as I mentioned earlier, that can actually match the anatomy of the patient.

It comes out in a cone shape and it diverges just as any light source would. You know how when you hold a flashlight to a wall, you get a nice precise circle. As you pull the flashlight away, it diverges. So we have filters and we have what's called the multi-leaf collimator that can actually shape the beam, as I mentioned earlier, that can actually match the anatomy of the patient.

But now that's all done. Automatically, we programmed it ahead of time as opposed to the old days when we had to use lead blocks that were actually physically blocking the beam. But basically, the LINAC has been the standard. Prior to that, we were using a Cobalt-60 machine, which is essentially, it's not even a machine.

But now that's all done. Automatically, we programmed it ahead of time as opposed to the old days when we had to use lead blocks that were actually physically blocking the beam. But basically, the LINAC has been the standard. Prior to that, we were using a Cobalt-60 machine, which is essentially, it's not even a machine.

It's basically just exposing a patient to a radioactive isotope and then shutting the jaws again. And actually, those are still in use in most of the world. There's a few left in the U.S., but they've mostly been decommissioned now because the LINACs have taken over.

It's basically just exposing a patient to a radioactive isotope and then shutting the jaws again. And actually, those are still in use in most of the world. There's a few left in the U.S., but they've mostly been decommissioned now because the LINACs have taken over.

So roughly 2.5, 2.6 gray per day. And you're right, times 15 treatments. So you're getting roughly 40 gray to the breast. And then we usually actually do a boost. So we'll give what we call a tumor bed boost. We give a little extra dose to just the lump itself, the lumpectomy cavity itself.

So roughly 2.5, 2.6 gray per day. And you're right, times 15 treatments. So you're getting roughly 40 gray to the breast. And then we usually actually do a boost. So we'll give what we call a tumor bed boost. We give a little extra dose to just the lump itself, the lumpectomy cavity itself.

And there was a couple of French trials that showed that adding an extra 10 gray over an extra five days, so two gray times five, just to the lumpectomy cavity itself improves local control over just the whole breast.

And there was a couple of French trials that showed that adding an extra 10 gray over an extra five days, so two gray times five, just to the lumpectomy cavity itself improves local control over just the whole breast.

An extra boost. It's a customization based on the patient's pathology. I'll occasionally have a patient that the breast surgeon will call me and say, hey, Sanjay, we did our best, but we had a persistent positive margin. I went back and did a re-resection and there's still a positive margin, or maybe the positive margin is at the chest wall. They can only go so far.

An extra boost. It's a customization based on the patient's pathology. I'll occasionally have a patient that the breast surgeon will call me and say, hey, Sanjay, we did our best, but we had a persistent positive margin. I went back and did a re-resection and there's still a positive margin, or maybe the positive margin is at the chest wall. They can only go so far.

In that case, instead of giving a 10 gray boost, I might give a 16 gray boost or something to account for instead of just treating microscopic disease, potentially macroscopic residual in that sort of situation. So every patient's a little different. And then the axillary nodes themselves are normally not treated in an early stage patient.

In that case, instead of giving a 10 gray boost, I might give a 16 gray boost or something to account for instead of just treating microscopic disease, potentially macroscopic residual in that sort of situation. So every patient's a little different. And then the axillary nodes themselves are normally not treated in an early stage patient.