With the start of basketball season, my laboratory begins scanning the college and professional basketball teams. As we start to scan these athletes I am reminded of just how tall these athletes are. Although dual X-ray absorptiometry (DXA) is considered the ‘gold standard for the assessment of body composition there is one weakness of DXA and that is for most DXA scanners, the height limit is 78 inches (6 feet 6 inches or 1.98 meters). Unlike football players where the challenge of scanning them is due to the width of their shoulder and upper body basketball players present a different challenge.
To be clear, the table length of DXA scanners does not mean you cannot measure an athlete who is taller than 78 inches. It just requires a couple of considerations you need to make prior to scanning these tall athletes. You have to decide how you want to place the athlete on the DXA scanner. No matter how you place them on the scanner you are going to lose some data at either the head or feet since one of those areas will have to be outside of the measuring area of the table. Most DXA manufacturers will tell you that when measuring someone taller than 78 inches to position the head at the top of the table and place the feet outside the scanning area. Although this is a reasonable solution, in basketball players the lower limb is vital to the sport so losing part of the legs is not something you want to do. Another solution is to align the individual’s feet at the end of the table and allow part of the head to be outside of the scanning area. Although some DXA manufacturers may frown on this solution, remember that the DXA will provide body composition measures not using the head. This is for a number of reasons. In children and adolescents, the density of the head due to it growing is somewhat variable. For adults the density of the head is much more consistent however, the amount of fat and muscle mass involved in the head is relatively small so losing a portion of it will have little effect on overall amounts of muscle mass or fat mass.
Some of you may worry that the head being unsupported will be uncomfortable for the athlete. Although the scanning area of most DXA scanners is 78 inches, the tables themselves are actually longer than 78 inches so the table will often provide support for the head even if the individual is taller than 78 inches. We have found that individuals up to 82 inches (6 feet 10 inches or 2.08 meters) experience no discomfort with their heads lying outside of the scanning area. This covers a majority of basketball players, however, for those individuals taller than 82 inches we often support the head using a small support device made from RohaCell® (Evonik Resource Efficiency GmbH, Essen, Germany)(see image1). This material has traditionally been used in the construction of X-ray tables and is invisible to most X-ray admitting devices such as the DXA. Therefore, you can have a portion of this material under the individual’s head and neck and it will not affect the results of the DXA scan (see image 2). One issue with RohaCell® is that it can flake a little when handled so we shrink-wrap our RohaCell® support to prevent flaking. The RohaCell® head support that we have created is 20.5 inches x 12.5 inches x 0.5 inches. The support is placed under the DXA table pad and only 5.5 inches is actually extending beyond the DXA table pad. The rest of the support is actually under the individual being scanned.
If you are scanning basketball players or anyone that is taller than 78 inches then I suggest viewing our blog “Too Tall For The DXA Table?” That blog not only discusses how to scan athletes that are too tall for the DXA table but also provides a video that demonstrates how to scan these types of athletes.
About the Author
Donald Dengel, Ph.D., is a Professor in the School of Kinesiology at the University of Minnesota and is a co-founder of Dexalytics. He serves as the Director of the Laboratory of Integrative Human Physiology, which provides clinical vascular, metabolic, exercise and body composition testing for researchers across the University of Minnesota.