I routinely get questions asking “which [machine MR, CT, etc.] should I buy?" Unfortunately, this is a question with no easy answer. Veterinarians purchasing imaging equipment must realize that everything in imaging is a trade off. When purchasing equipment and using the equipment to generate diagnostic images, decisions must be made in logical, economical, and emotionless manner. Failure to do so will result in wasted money and/or jeopardizing the safety of the patient.
The first step in purchasing any imaging device is to understand the diagnostic threshold level for the modality. This is the level of image quality at which all of the information necessary to make the diagnosis is present in the image. Below this level you will miss the diagnosis because pertinent information is absent from the images. Above the threshold level the images contain more information and are often times sharper, prettier or are otherwise more impressive but the added information does not change the diagnosis. Never buy equipment that generates images below the necessary diagnostic threshold. Determining the diagnostic threshold for a modality takes time and experience. If you are unfamiliar with an imaging modality seek out an expert such as your local veterinary radiologist for assistance.
Determining the diagnostic threshold can be difficult because this threshold will vary depending on the intended use of the machine. All purchases must be made with a full understanding of the future use of the machine. For example, if you purchase a single slice helical CT with the intent of doing skull imaging and basic body imaging but later find that you want to perform full body metastatic screenings with 3D reconstructions you will find that a multidetector CT would have been more appropriate and you will find your images for these advanced applications under the diagnostic threshold.
The next step in purchasing an imaging device is to analyze the trade offs. Everything in imaging is a trade off. The three main trade offs are:
- Cost vs. speed
- Cost vs. image quality
- Image quality vs. safety
It is pretty easy to purchase a machine that will allow you to obtain a beautiful image, very quickly, if you don’t care at all about the safety of the patient or your staff, and you don’t care how much it costs to you to obtain that image. Conversely, regardless of how fast that image is obtained or how much you operate your practice to the detriment of your technical staff if your new machine cannot create the images necessary to make a diagnosis, it is not worth having it in your practice.
We see three main equipment purchasing problems:
- Trying to save money and purchasing equipment that falls below the diagnostic imaging threshold level for the intended use: In this situation, the veterinarian does not understand the diagnostic imaging threshold and fails to realize that the image on the screen does not represent the what is inside the pet but rather what the imaging device can image. If the device cannot image the pathology, there will be missed diagnosis and false negative results. If the deal seems too good to be true, it probably is. Know the intended use for your equipment.
- Failing to understand that image quality and patient safety are a trade off: In imaging, everything is a trade off. Patient and technical staff safety included.With digital radiography, image quality improves with increased technique. Increased technique results in increased exposure to the technical staff. Is the trade off worth it? With MRI, scanning time and image quality are correlated. Is it worth it to keep the pet anesthetized just to make pretty pictures or are the slightly grainy images sufficient?
- Buying equipment to start an imaging “arms race”: This is a situation that is happening more and more often in some markets. Practices are buying imaging equipment and using imaging as a marketing advantage. It seems that that the theory is that the practice with the prettiest pictures - wins. Unfortunately, in these situations, there are no winners. These markets have lost sight of the diagnostic threshold are now concentrating on making pretty pictures for the sake of pretty pictures. In these situations, the costs are passed on to the pet owners who become losers; and the safety issues are passed on to the pets who also become losers.
The bottom line is that everything in veterinary imaging is a trade off. A failure to understand these trade offs will result in unnecessarily spending money or unnecessarily risking the patient’s safety in an effort to obtain the prettiest pictures. The added cost is passed on to the owners and the safety issues are passed on to the patients. Always perform a trade off analysis and understand the diagnostic threshold before purchasing any imaging equipment for your hospital.