Can MRI show if changes are normal or if brain lesion's growing?

The 6th of September it will be year since I underwent External Beam Radiation Therapy for 3 original brain lesions that had spread from my left kidney mass (I had my left kidney with the mass removed in Nov. 2024), but it spread to my lungs within three months as a lung biopsy showed in March 2025; and then August 8th, 2025 3 lesions were found in my brain. I was referred to a radiation oncologist immediately by my regular Oncologist/Hematologist for radiation treatment. Since it will be a year very shortly, and I have had MRI's with and without contrast of the brain ordered by the Radiation oncologist along with CT and alslo PET/CT's of Chest, Abdomen and Pelvis every three months this past year, with the 4th lesion being treated the last of November 2025 as it was not discovered until October 2025, the MRI's of the with and without contrast show two of the original 3 along with the 4th being stable, but the lesion in my right frontal lobe shows swelling and fluid surrounding it and my radiation oncologist plus the radiologist cannot tell if it is changes due to the radiation or if the changes are due to increase in size of this lesion. The ones that are stable along with the one he can't tell if it is getting bigger are all under 2 cm in size right now and very small and Praise God have stayed at 4 with no more developing for almost a year now. His answers are the same everytime telling me that with the next scheduled MRI he should be able to tell. Because of the "only time will tell" answer I asked him last winter if it will be years, or months or what? He said months. He refuses right now to re-radiate the four lesions, but I told him, I don't want to just wait around and let them all get too big to treat? That's when he replied about he can't tell and will not re-radiate them now. This has led me to seek a second opinion at Vanderbilt Ingram-Cancer center which will either confirm his waiting or point out more options I hope. Can anyone provide some input? It seems like near a year he would be able to tell if its just normal changes from almost a year ago or if the lesion is growing?