Weight Limits and CT Scans: Extra Considerations for Obese Patients

CT scanners are large machines that require patients to slide at least halfway into it to properly scan and record diagnostic images. A patient undergoing a CT scan has to be slid into the machine’s gantry while on their backs. Considering the size of the typical CT scanner, this doesn’t usually present much of a challenge. However, you may have obese patients who may not fit through a standard CT scanner’s gantry. A lot of standard CT scanners are not designed to support patients past a certain weight limit as well. You’ll need to consider this possibility if you are thinking about investing in a new CT scanner.

First and Foremost – What is The Weight Limit for a Typical CT Scanner?

Most CT scanners can support no more than 450 pounds. This should be adequate to support the weight of 99 percent of your patients. However, there are patients who exceed this weight limit who are in need of CT scans. It’s not just the ability to support the weight that you need to worry about. The size of the gantry can pose difficulties as well. Most gantry aperture diameters are between 70cm and 85cm, which means that obese patients may not be able to fit into the gantry even if the table supports their weight.

Image quality is another consideration. A larger patient requires a larger field of view. Additionally, the X-Ray tube power will need to be increased as well. Standard patients can be scanned at 120kV, but a larger patient may need to be scanned at 140kV to 150kV to ensure the quality of the images being captured. This will also require the CT scanner to generate the power needed to increase the voltage and current of the X-Ray tubes.

Problems Associated With Obese Patients and CT Scans

Because of CT scanner tables may not be able to support patients past a certain weight limit and because they may not have a big enough gantry (not to mention that obese patients have different imaging requirements), a standard CT scanner may pose problems for you. The following are a few common issues you’re likely to face when trying to accommodate an obese patient.

Finding a CT Scanner That Will Accommodate The Extra Weight Can Be an Expensive Exercise

CT scanners are expensive as is. They take up a significant amount of space, and installation costs tend to be high as well. Investing in a CT scanner that accommodates obese patients means the system has to be larger to support more weight and fit the patients through its gantry. The bigger the CT scanner is, the more expensive it will be.

It May Be Necessary To Use an X-Ray or Ultrasound Instead

You may not have the budget to upgrade to a CT scanner that can accommodate your obese patients — and even if you did, it may not make financial sense to do so just so you can accommodate the one percent of your patients that are obese. As a result, you may be forced to use your X-Ray machine or Ultrasound instead.

Issues with Effectiveness

CT scans provide more detail than X-rays and Ultrasounds. Not only do they allow for higher resolution scans, but CT scans allow for 360-degree image captures that are not possible with X-rays or Ultrasounds, which only capture 2-D images and can’t see past bone. This means if your patient is too obese to undergo a CT scan, the images you capture using X-rays or Ultrasounds will limit your diagnostic abilities.

Can Lead to a Missed Diagnosis

By having to settle for using X-Rays or Ultrasounds on patients who are too obese to go through your CT scanner, you could potentially risk misdiagnosing them. This happens when you can’t view 3-D images of a patient’s internal systems and you’re forced to attempt a diagnosis using the limited view of a 2-D image. This can be extremely problematic when it comes to diagnosing potentially life-threatening conditions, such as tumors (for which CT scans are often used).

An Overweight Patient Can Cause Damage to The Equipment

Attempting to fit an overweight patient onto your CT scanner can result in damage to your CT scanning equipment if your patient exceeds its weight limit. Such damage requires expensive repairs and will put your CT scanner out of commission until you are able to make those repairs, inconveniencing countless patients who may have had CT scans scheduled.

Other Options Available For Obese Patients

If your current CT scanner wasn’t built to accommodate overweight patients, it doesn’t mean you won’t be able to diagnose whatever issues they have. The following are a few alternatives to consider if you’re forced to rule out the use of your CT scanner due to the patient’s weight.

Older, More Traditional Options Are Still Available

Although CT scanners allow doctors to make more accurate diagnoses, doctors did have the ability to accurately diagnose patients prior to the invention of the CT scanner. CT scanners haven’t been around for that long, after all. More traditional methods can be employed to diagnose any obese patients you have, whether it’s through physical exams or the use of exploratory surgery.

Physical/Clinical Exam

Although a physical exam is much more limited than a CT scan since doctors won’t be able to see inside the patient’s body, they can still be effective. The use of observation, auscultation, percussion, and palpation can often evaluate the objective anatomic findings needed for a partial diagnosis. Physical exams usually provide around 20 percent of the data needed to make an accurate diagnosis, which is often enough to be able to figure out some of the potential causes of the problem the patient is experiencing.

Exploratory Surgery

Using the information you’ve gathered from a physical exam, exploratory surgery can be performed on the patient to find a diagnosis for an ailment. Exploratory surgery is still done to identify conditions that may be more difficult to pinpoint using standard tests, such as cancer in certain areas of the body.

Barometric Scanners

Bariatric CT scanners are available that were built specifically to accommodate larger patients. These scanners are able to support more weight (often upwards of 700 pounds) and have wider bores as well (up to 78cm in diameter), making it easier to fit patients inside.

These Types of Scanners Can Be Expensive

There are a few drawbacks to investing in a bariatric CT scanner. It is a bigger machine, which means it will take up more space. This may require renovation work in your facility, which can be expensive. Initial costs and installation of larger CT scanners will be more expensive as well.

May Be A Necessary Expense 

If you have a lot of obese patients, you may not have much of an option. The obesity rate is climbing in the U.S. as well. As of 2017, the adult obesity rate was at or above 30 percent in 29 states. More American adults are obese than just overweight. Unfortunately, if you think you might have a need for a bariatric CT scanner, odds are that need will only increase year by year.

Popular Models

There are a number of different models available from some of the most highly regarded CT scanner manufacturers that are built to accommodate obese patients. Some of these models include the Siemens SOMATOM Definition AS Open HD FoV Pro that provides a large FoV and excellent image quality for larger patients. It also has a wide 80cm diameter bore and is available with a 676-pound table load design.

Phillips also manufactures CT scanners that are suitable for larger patients, such as its Big Bore RT, which boasts an 85cm bore aperture. In fact, CT scanner options have expanded so much over the years that all major CT scanner manufacturers have bariatric options available.

Adjustments to the Protocol

Your protocol will need to be customized for scanning obese patients. Determine what their weight is and whether they will fit into the gantry before placing them onto the CT scanner. Perform a physical examination first and determine what your best options are before attempting to put them through a CT scanner. Even if they can fit and the table supports them, scans can be quite uncomfortable for them. You will also need to adjust the procedure itself. More contrast is likely to be needed as well as higher kV, and you’ll need to adjust the scans to ensure clarity in the images. Otherwise, you will end up having to scan them all over again.

It’s Crucial to Consider the Feelings of Your Patient

The last thing you want to do is to offend your patients. Be sensitive when it comes to discussing their weight. If your patient is obese, of course they know this, and going out of your way to avoid talking about it will simply make them more uncomfortable. However, be sensitive with the language you use. Don’t refer to them as “obese.”

For example, if you need to weigh them to figure out if the table will support them, don’t tell them that you need to weight them to make sure that they aren’t too heavy for the CT scanner. Instead, tell them that you want to make sure that the table will support them so that they won’t hurt themselves. If you’re measuring them to make sure they fit in the gantry, say something along the lines of “we want to make sure you’ll fit comfortably into the gantry,” instead of “you may be too large to fit inside.”

Make it about their comfort and not about your convenience. You don’t want to make them feel bad about the fact that they may not be able to fit into your CT scanner.

Additional Points to Keep in Mind

Besides risking damage to the CT scanner by using it on an obese patient who does not fit, don’t waste time or risk embarrassing the patient. It’s why you should make sure the CT scanner can accommodate the patient’s weight before you attempt to place them into the scanner.

Ensure You’ve Checked The Weight Limit of Your CT Scanner Before Using It With a Patient

Make sure your staff is trained to handle an obese patient and to know what to do. The last thing you want is for them to attempt to fit the patient onto the table if it’s not built to support their weight since this can damage your CT scanner. Make sure everyone knows the weight limit of your CT scanner and that they weigh obese patients before trying to place them on the CT scanner table.

You should also make sure that the patient will fit into the gantry even if the table supports their weight. Some hospitals have created hula hoops reflecting the size of the diameter of the gantry that they use to determine if the patient fits. This way, they don’t waste time trying to fit them into the scanner and embarrassing the patient.