Why do I have to have two MRI's?

July 14, 2010 12:20 PM

I need an MRI of both my lower back and my left knee. The lady in scheduling told me I will have to be in the MRI for 40 minutes for my back, and then I'll come out and then have to go right back in for another 40 minutes for my knee. This doesn't seem right. Why can't I stay in the MRI machine for 40 minutes and then have my back and knee imaged at the same time?

I'm trying to call my doctor's office to find out why this is, but I keep getting the voicemail. Can anyone explain to me why I have to undergo the MRI twice? And also, it appears the price will be for 2 MRI's, about $1000 each, does this seem right?

Thanks!

posted by lynnie-the-pooh to Health & Fitness (9 answers total)

They can't MRI your back and knee simultaneously. They have to center your back in the machine, put a coil on that is designed for imaging your back, and do that scan. They they will have to take you out, possibly turn you around depending on where on your back they're scanning, put a different coil over your knee, and center your knee in the machine to scan it. It's not possible to do them simultaneously.

And yeah, that price looks about right.
posted by brainmouse at 12:25 PM on July 14, 2010

Little bit more info: These pages show what the different coils might look like. They can only use one at a time. Very, very basically, the coils send out radio frequency pulses that interact with the magnetic field in a way that allowed the imager to... image.
posted by brainmouse at 12:32 PM on July 14, 2010

I agree with brainmouse on the reason why they require two MRIs. When I had a head MRI, they billed the insurance company $3,500. Head scans tend to be more expensive, but $2,000 for 2 MRIs sounds very reasonable to me.
posted by parakeetdog at 12:34 PM on July 14, 2010

They can't do both scans simultaneously. There are different coils they will use for each part, and your orientation will be different for each scan.

Depending on the facility and the hardware, you could ask for a DVD of your images. We do that all the time for people here.

The price seems in the ball park. We charge a bit more, I think, but I don't do billing, so....
posted by Pogo_Fuzzybutt at 12:51 PM on July 14, 2010

I'd be very, very surprised if you were really in there that long. We try to keep clinical scans at my department under 20 minutes (for patient comfort). Honestly, I can't imagine what sequences they'd run to keep you in there that long. Sure the tech will change the coils, but as a patient I wouldn't perceive that as a separate MRI. That doesn't mean however that they don't bill it that way. More than likely the lady at scheduling is told to block out 40 minutes per scan.
posted by sero_venientibus_ossa at 2:01 PM on July 14, 2010

Another reason the double images at the same time wouldn't work: superconducting magnets are adjusted through a process called "shimming" to have a "sweet spot," or a region where the magnetic field is especially homogeneous. In an MRI magnet, the spot is about as big as one body part, and certainly couldn't accommodate two body parts as far apart as your back and your knee. Also, even if they didn't have to use different coils, I'd be very surprised if the magnet or the computer they're using to create the images are set up to handle more than one data output at a time.
posted by hoperaiseshell at 2:14 PM on July 14, 2010

If you are worried about cost, can they do a CT Scan for one or both images? CT scans use x-rays rather than magnetic imaging and can be cheaper, but aren't always suitable.
posted by dantodd at 3:25 PM on July 14, 2010

My experience is ten years out of date, but I used to develop software for MRI machines (I wrote the software that actually did the scan and generated the raw image). Ten years ago, $1000/scan would have been below market rate and MRIs were routinely covered by insurance. @Hoperaiseshell is right -- the magnetic field has a gradient, so you need to get the body part you are imaging centered in the middle of the field to get a good image. And I agree with @sero_venientibus_ossa on the 40 minute scheduling fiction. MRI machines are expensive to buy and expensive to maintain. The imaging clinics I spent time around operated from 7am to 7pm and scheduled patients on 30 minute blocks, including time to get patient set up and in and out of the bore. I suspect that was more about profitability than patient comfort. Your actual time in the bore will probably be more like 10 to 15 minutes. Finally, to @dantodd's suggestion, CT scans give the radiologist a view of bone by essentially casting shadows with x-rays; MRIs give a view of liquids (soft tissue) by exciting the water molecules, so they are different tools. Presumably your doc ordered the MRI and is looking for something specific.
posted by kovacs at 5:51 PM on July 14, 2010

I just had an MRI on my neck, yesterday. They asked if I had any problems with tight spaces, and I admited that I do have a mild problem. Well, they have a nice something in a nose spray for that. Makes it easier to just close eyes and not be concerned by the surface, 10 cm (4") from my face.
posted by Goofyy at 12:11 PM on July 15, 2010