a while back i volunteered in the radiology dept. got to follow the rad techs around as they took various x-rays around the hospital. got a lot of patient interaction here, for example if there was a particularly heavy patient who was non responsive, the rad tech would not be able to lift him on his own to get the x-ray slide behind his back to take the chest x-ray. then i helped the tech develop the slide.
also i got to observe some interventional radiology procedures. i always thought radiologists just sat in dark rooms all day but apparently one of the specialties, interventional radiology is like surgery-lite. they put a camera into the body and do various procedures, like finding a tumor or angiogram, and even some treatments like embollizations, draining fluids, and inserting catheters.
look, you have to MAKE oppurtunities if you want to get anything meaningful out of your volunteer experience. ask a lot of questions, if you can do things, be a little annoying, dont be afraid of rejection.
edit - if you are just pulling charts and things like that, try asking the nurse about the charts. learn how charts work, what goes in the chart, and maybe some of the issues the patient is dealing with. when you hear about some medication, or see something in a chart, ask about it. i'm pretty nosy and skimmed through a lot of charts in my free time in some departments