As the name somewhat implies, diagnostic imaging provides images that are used to help us attain a diagnosis. It’s as simple as that. So what do they entail? The most common are X-rays, radiographs if you will, ultrasound, and then some of the more advanced modalities would be things like MRI or CT scans.

So how do you determine which one is the most applicable or the most useful in a situation? It varies tremendously on how the animal presents. If you’re looking at bones, then most of the time a simple X-ray is going to be fine. And I say a simple X-ray just because they’re very common. They’re readily available at almost any veterinary clinic.

If you need to look at the internal structure of the liver or the spleen or something like that, X-rays are probably not the best one for that. You’re going to want something like an ultrasound that can actually see what the integrity of the internal components of that organ looks like. So that would be a case where maybe ultrasound might be more applicable.

So rather than go through every device or every situation one by one, it really depends on what the presenting complaints or signs are that will dictate what type of imaging is best used.

There again, it depends on what you’re looking for. I hate to be vague, but it’s true. That’s a tough one to answer with just a black and white answer. They’re all pretty good in their own right. You have a broken bone, don’t ultrasound it. Start with an X-ray. And if you need more detail, then a CT scan would probably be next. Again, you also have to keep in mind in the real world, a CT scan is not available at your neighborhood veterinary clinic. So usually CT scans and MRIs are reserved for cases where you can’t get an answer with ultrasound, X-rays, blood work, and you’ve exhausted all other diagnostic abilities. In those cases, you may have to refer that cat to a teaching hospital or a referral center or something like that, where they have specialists. And they are the ones that would typically have some of those advanced modalities. So it’s hard to say which one is more accurate just as black and white as that question implies.

When it comes to the tools we use – X-ray and ultrasound – it’s a matter of hoping that the cat is cooperative enough with you to lay still. That’s it. With an X-ray, we typically want to get a lateral view with them on their side of whatever we’re shooting, whether it’s abdomen, chest, or even an extremity. If you want a lateral view coming from the side, then you typically want what we call it a VD ventral dorsal. So you want it from the bottom to the top. So we put them on their back and we kind of stretch them out that way. And that’s what we try to do. Some cats will do that quite readily. Some cats will not. Sometimes they require a bit of sedation to allow us to position them properly and get good images.

Obviously, we don’t want to sedate animals if we don’t have to, especially sick animals, but sometimes in order to obtain a clear diagnosis and do it justice, you have to use sedation. You just can’t do it on an awake cat who’s fighting and trying to bite you. So sometimes they have to be sedated. Ultrasound is almost identical to that. We have a little V-shaped cushion that we’ll put them in and we’ll normally have my technicians holding them, giving them affection, and they do whatever they have to do to keep them occupied or distracted. And an ultrasound’s very non-invasive—it’s a little probe that you use after wetting their skin down with alcohol or some sort of a contrast agent. You roll the little probe around to see what you need to see. Again, some of them require sedation. It just depends on the cat.

The last two modalities – CT scan, MRI – are seldom done in common general practice. But if they do have to be done, those animals often have to be under general anesthetic or very heavy sedation because they can’t move. Those scanners are such that you cannot have people in the scanner with them holding a cat in position. The cat has to lay there perfectly positioned and not move. Good luck doing that on an animal that’s awake.

X-rays… Broken bones, intestinal obstructions, bladder stones, things like that. Those are what I think… Dentistry. Those are where I think that X-rays, they serve their purpose. They’ve been around forever, not forever, but I mean, they’ve been around a very long time, but they serve their purpose. They work very well for that, and they’re much more cost-effective. So things like that. That’s what I’m reaching for first.

If I need to look at a soft tissue structure and I need to see the internal components of said soft tissue structure, then I’m grabbing my ultrasound. It allows you to look at the internal components of the bladder, the kidneys, the liver. I can see the vasculature and the blood flow and the drainage in everything from the liver to the heart, and I can see the heart valves. I can actively see the heart contracting and watch the heart valves fluttering and closing with an ultrasound. So it’s perfect for that kind of study.

MRIs and CT scans are more advanced. You need much more acute detail. We’ve all seen medical shows on TV. What does an MRI or CT scan look like? It’s a hundred little slices. You see their films on the wall and it’s got all these tiny images, not tiny images, or small squares on these great big films. That machine will hypothetically take hundreds of slices as it goes through the tissues and it lays them down and puts them on a film.

Say you’ve got a brain tumor. You’re looking at a soft tissue structure that’s encased in bone. I can’t see that on an X-ray. My X-ray is going to pick up that bone. It’s going to be bright white, but I can’t see the soft tissue of the brain underneath. Ultrasound cannot penetrate the bone. So that’s useless to try to see that. You need something that can actually take those slices, if you will, of tissue, and then be able to look at them this way. You’ll see the bone, but you’ll also see all the soft tissue encased underneath. And you can literally say, “Okay, this is at one millimeter, two millimeters.” It’s probably smaller than that, but you can literally break it down and have a sequential step. So you can see exactly where a growth or a mass or any kind of a lesion starts and stops based on that.

Lastly, too, I know MRI is pretty superior when you’re looking at ligament. Let’s say you have a torn cruciate or a torn meniscus and for whatever reason; my mind is stuck on knees right now. But if you have some sort of a soft tissue structure, an orthopedic soft tissue structure, MRI is really hard to beat if you need that kind of acuity to see if something is torn or partially torn. No other study can touch that kind of accuracy that you get with MRI on that.

That’s actually kind of an interesting question. And it’s something that I’ve toyed with and I don’t routinely do because it’s, if I’m being blunt, it’s a hard sell. Like it’s hard to convince somebody, “Let me do X-rays on your cat. They’re completely normal, but let me do X-rays on your cat as a baseline.” To answer your question, what’s the benefit? If we do X-rays on a one-year-old cat who has no clinical signs or problems of anything at all. That X-ray should and usually will be normal. That’s great. What does that provide me? That’s the baseline that we’re talking about.

Fast forward 10 years. And then now that same cat comes in and now he’s sick or now they’re behaving differently, and for whatever reason, we have to shoot X-rays again. Well, I can always go back and pull their films from when that cat was one year old, and compare to now at 11 years old and I will typically see differences. The baseline gives you the normal for that said animal that you can use for the rest of its life to compare back against. Is it always going to come into play? Maybe not, but that’s the point of a baseline is to know what normal is.

The same thing applies to blood work. Why don’t we do wellness blood work? To know “A”, that the animal is well and also if it is, to know what’s normal for that animal. We do this so, if at some point down the road, they become ill with any kind of condition, you have something to compare to. And it’s comparing apples to apples. It’s not just some cat, it’s that cat from X amount of time ago. And that’s the benefit of baseline radiographs and baseline blood work.

I said at the beginning, it was a hard sell because it’s hard to convince people to do that and to spend a hundred, $200, whatever it is, for X-rays when they don’t have a problem, but that would be the benefit of it.