I can't speak about Walter Reed, and Dana Priest is certainly detestable. However, I have worked for a medical equipment company, and I recall that, at least in the 80's and 90's, when it came to x-ray machines, the VA would buy only the most basic, stripped-down models, in fact the same models that were bought by clinics at federal prisons. It was weird, because at the same time, DARPA was funding R&D on the most advanced models, to improve survival in field hospitals.
Walter Reed is not part of the VA system.