1.5 + 1.5 = 3, right? So a 3T MRI is twice as good as a 1.5T MRI, right? As far as the field strength is concerned – sure. In the world of sales and marketing – absolutely. But from an imaging standpoint, from a throughput standpoint, and from a cashflow standpoint – maybe not. Before you spend (in some cases) twice the money for a 3T, it might benefit you to take a look at what it can do for you, what it can’t, and what you are planning on doing with it!
Bread and butter systems are still what butters the bread
Without tagging it with a percentage, let’s just say that a 1.5T MRI is completely adequate for the majority of scans that are routinely done on MRIs in the U.S.A. today. The 1.5T Short bore MRI still remains the standard and still accounts for the vast majority of MRIs currently in use. It’s not that 3Ts haven’t “caught on,” but when looking over the landscape of consolidation, reimbursement changes, patient needs, and competitive concerns there’s a real need to be deliberate about equipment choices, especially when weighed against facility improvements, staffing, and the need for other modalities. After all, though the price tag is substantially higher for a 3T than a 1.5T the federal reimbursement does not change.
Drown out the noise or turn down the volume?
Image noise is always present in an MRI scan – think of it in terms of “white noise” if that helps. Most of this noise actually comes from the patient’s body as well as the electronics inherent in the MRI system. The goal is to have more “signal” creating an image than “noise” which can affect the image quality. This can be achieved by both 3T and 1.5T MRI, but in different ways…..
10 year old girls tend to be especially loud. If they congregate together at a birthday party the excitement makes them even more so. Games keep them busy until the party can mercifully end. If you wish to have a proper game of musical chairs for instance, you have two choices if you want everyone to hear the music:
- Turn up the volume
- Quiet the children
A 3T system works much like your stereo as it plays kiddie music at top-volume. It essentially gives you more signal – more molecules are resonating in the increased field strength and drowning out the noise. A 1.5T system using multi-channel phased array coils works more like quieting the children. It enables you to get more coil elements closer to the part of the anatomy being studied to create a “less noisy” image.
Clarity, Speed, and your Imaging Needs
Two things come to mind when considering 3T systems: Better image clarity and speed. Simply put, the 3T system with its stronger magnet field will increase the signal available (which creates the image) and the potential for better image clarity at comparable scan speed. However, you can’t always have the best of both worlds and MRI studies are a compromise between scan time and image quality. So depending on the tech, your throughput needs, and other factors this is typically skewed in one direction or another. Point being – you can still get beautiful images with a 1.5T system using multi-channel coil technology – but the scan times would be longer than a 3T. Conversely, you can shorten scan times as well with a 1.5T system but the image quality will be sacrificed somewhat. It all depends upon the type of study that’s needed. Like choosing between a Chevrolet and a Formula One racecar; both will get you where you need to go, but before you buy one or the other, it’s important to assess how quickly you actually need to get there.
Supply and Demand
If you’re doing the types of studies that involve very minute detail, (sophisticated brain work is one of the categories in which 3T really shines) or if your market area, throughput needs, or referring doctors are leaning you toward 3T, then be sure to plan ahead. 3T systems are costly – even on the secondary market the pricetag could easily be double what you’d pay for a 1.5T, and they are still rather difficult to find. Give yourself time to locate one and make sure your room can accommodate it. Typically the active shielding on these magnets is good enough to contain the 5 Gauss line in a moderately sized room, but make sure. And keep in mind: The strength of electromagnets used to pick up cars in junkyards is about the same as 1.5T MRI. 3Ts have twice as much magnetic field. Be sure to have safety measures in place!
If your studies will be less detailed or your pace will be less hectic, you’ll be able to get everything you need from a 1.5T system. These systems are far more readily available as are replacement parts and service engineers to keep them running. As with 3T systems, you’ll want to be sure your site can accommodate your new magnet. Even at half the magnetic field, a room without proper safety precautions can lead to costly damages and serious injuries.
Meet the author: Steve Rentz
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