The Doctor Weighs In

My son Jason, the radiologist, sent me an article from the American Journal of Roentgenology.  It is called, "Impact of Obesity on Medical Imaging and Image-Guided Intervention."  It is a treatise on what radiologists need to know about providing imaging services to obese people.   Here are some of the key questions addressed in the article:

• Is it possible to transport the patient from the hospital room to the radiology department?
• Can the patient fit into the machine?
• Can you get good images that help with the diagnosis?
• Can you get good images without exceeding recommended allowances for exposure to radioactive substances?
• Can interventional radiology procedures (e.g., imaging-guided biopsies) be done safely and effectively?

Too big to fit?

It turns out there are weight limits for both transportation equipment and imaging machines that can preclude a very obese individual from being able to get in a wheelchair for transport and from fitting into, say, an MRI machine.  Most hospitals currently have equipment that accommodates individuals up to about 450 pounds, although one type of MRI, called a vertical field MRI, can accommodate individuals up to 550 pounds.  If you try to put someone heavier into the machine and it is damaged as a result, the cost of the damage won't be covered by the manufacturer's insurance.

But it isn't just about weight, obese individuals may also be too big to fit into the opening of the imaging machine.  To save obese patients the embarrassment failing to squeeze into an MRI or CT scanner and to save precious time on the part of the radiology department, the article counsels that staff should ask about the patients weight and girth before scheduling the appointment.

Manufacturers are responding to the obesity epidemic by producing hospital equipment and imaging machines that can accommodate larger people.  But this equipment is expensive, particularly the imaging machines which can costs more than a million dollars.  We can expect that smaller hospitals and hospitals that serve populations that are un- or under-insured are not going to be able to afford to replace existing equipment quickly enough to keep up with demand.

Quality of the image

The increased body thickness of obese individuals requires the X-ray beam to travel farther than it does in a normal weight person.  This means increased exposure time and introduces the possibility of motion artifact (this is similar to what happens when you use long exposure times on your camera).  The result can be images that do not provide enough clarity to help with a diagnosis. 

Sometimes, obese people are so big that you need to use more than one radiograph cassette or, in the case of nuclear imaging, you need to give high doses of the radionuclide used to obtain the images.  Sometimes, even administering the maximum allowable dose of radionuclide is inadequate to obtain optimal images.

Can you do the biopsy safely?

There are lots of problems performing imaging-guided interventions on very obese people.  They may have compromised airways making conscious sedation (the person is awake, but doesn't feel or remember the procedure) unsafe.   Further, proper positioning of the patient for the biopsy may be difficult requiring extra staff people to accomplish.  Pillows and sometimes sandbags may be required to hold the person in position.  Longer than normal instruments may be necessary to reach the site to be biopsied.   These problems posed by obese patients may dictate that the obese person has to go to the operating room and have a surgical procedure instead of the less invasive imaging-guided procedure.

The AJR article provides information not only on the challenges of imaging obese individuals, but it also provides detailed suggestions for how to successfully address these challenges.  But, in the end, there is no question that if you are obese, you may likely have an imaging problem. 

This will be added to TDWIs growing list --  "Yet another reason to lose weight:"

Spending more on gasoline?  Yet another reason to lose weight

Obese people earn less, yet another reason to lose weight

Escape from prison:  yet another reason to lose weight

Pat Salber, MD, MBA