Wendy, I am a semi-professional photographer. I have done weddings and portrait work. I think with the right look it can make a good impression. I totally agree that the photos that are taken by some photographers tend to be just a photo without properly capturing you. The staged or posed shot does not work. The smile that comes when someone says "Cheese" does not work. The photo look needs to come from thought and attitude. When you get your photo taken, you need to be in the mindset of the caring, friendly doc. That mindset will show up on your photo.
You should not have to spend much on a head shot. Most photographers charge a sitting fee about $100 per hour and then they can give you the images. If you want something touched up, I will be glad to photoshop your images so that you get the look that you want and can save some editing costs.
Random shots with someone in your office popping off some shot with a phone can have amazing results too.