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Any procedure like this, especially in sensitive areas like the brain and spine, are done with 3D MRI topography guidance ("Look ma, no glasses!"). Look up STEALTH MRI if you're interested. You basically take high res MRIs with multiple markers placed on the surface of the subjects' skin for reference, then the computer does some fancy math and says "Put needle here, go this deep, then stop".
Quit the radiation fear mongering. And yes, IAAMD.