My experience with ultrasound: it didn't make things worse and maybe made them a little better. They wipe hydrocortizone cream (%10) on your foot and then use ultrasound waves to drive it into the fascia.
I say go for it. It seems to me that especially if you have a relatively recent injury (seven months doesn't seem recent to me), it might be effective. My PT was surprised that I didn't get healed in three weeks. That may be evidence that it heals people often. I believe that it took a little chink out of my pain-- maybe %5. I had insurance so why not. Otherwise, It's too expensive.
the ultrasound waves can cause damage to the bones in the feet if used too often, so they usually limit the treatment to a certain number of sessions. I'd say definitely try it, especially if you have insurance, but I have a lot more confidence in the long run, as many here will attest, in dogging it out with several self-applied therapies like stretching, diet, exersize, and a regimen of morning heating and possibly icing. You need to get devoted to this. Perhaps you already are, in which case you might try ultrasound.
But if ultrasound only makes you feel like you are doing something and don't need to do anything else, then it is harmful in that time is going by when you might have been getting aggressive about a more comprehensive discipline in easing this thing.