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Hey Vircet, the Linac doesn’t need fiducials because it tracks the prostate in 3D with realtime MRI. Cyberknife uses tomography to track the fiducials which are placed at 3 points on the gland - but it follows the fiducials regardless of gas bubbles or peristalsis moving delicate structures into the path of the beam.
The Linac shuts off if the gland/margin moves out of the target area but the CAT doesn’t - very clear advantage to avoiding tissue damage.
Also, MRI is not - as far as I know - compatible with metal so if you had fiducials placed I cannot imagine that they used an MRI based machine.
Only proton radiation has beams which STOP at the target - all photonic technologies use electrons that pass thru the target. When I first consulted with an RO who used MRIdian he said I would need a spacer.
As far as my radiation I would have to check but I saw a post treatment report which said 6000 to prostate bed and 4500 to pelvic nodes. Don’t think it was expressed in Gy, however.
Phil
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Hi Phil,
I believe the values in your post-treatment report are in "centigray (1/100th of a gray)."
If I am correct, this means you had 45 Gy to the pelvic nodes and 60 Gy to the prostate bed.
I read in another literature that 60 Gy is maximum (I am not sure if this information is current).
It appears that Elekta MR-Linac is similar to the MRidian machine.
After my 5th treatment, I told my oncologist that, "You told me the MR-Linac is used only for patients without the fiducial markers. But the radiation team told me they used Elekta linear accelator to treat me."
The oncologist replied, "Our Elektas are linear accelerators. MRI-guided for radio planning. The MR-Linac is real-time MRI, for patients without fiducials. don't worry, all our Elektas are good."
Perhaps, it can't get better than that. Before my cancer center got the MR-Linac, all their prostate RT patients were treated with the older machines, MRI-Guided for radio planning but not real-time MRI during treatment. Based on machine loading and machine capacity, I understand that the lone MRI-guided-real-time machine cannot replace all the other machines in the cancer center -- if I heard correctly, a thousand patients a year. (If I was paying with my own money or my private insurer's money, perhaps I could have insisted on the Elekta MR-Linac. As it is, our taxpayer-funded medical care cannot accommodate all who prefer MRI-Guided treatment, with "MRI-guided for planning" as the second best choice for many.
Thanks for your comments. I am learning. and I hope our discussion can help others still researching on what linear accelerator machine they will be treated.