Sarcopenia was quantified using two approaches—the Total Psoas Index (TPI) and the Hounsfield Unit Average Calculation (HUAC). Gender specific quartiles were then generated and the lowest 25% within each approach met criteria for sarcopenia. For TPI, the psoas muscle at L3 was measured as described by others [24 (link)]. The TPI (right psoas area +left psoas area)/(height2) normalized the measured psoas area for the height of the patient.
The Hounsfield Unit is a measure of radiation attenuation that can be obtained from a CT Scan. The HUAC of the psoas muscles is a measure of muscle density and fatty infiltration. Both the right and left psoas were evaluated and the average was used for the final HUAC calculation. Right Hounsfield Unit Calculation (RHUC) =(Right Hounsfield Unit*Right Psoas Area)/(Total Psoas Area), left Hounsfield Unit Calculation (LHUC) =(Left Hounsfield Unit*Left Psoas Area)/(Total Psoas Area), and HUAC =(Right Hounsfield Unit Calculation +Left Hounsfield Unit Calculation)/2.
The Hounsfield Unit is a measure of radiation attenuation that can be obtained from a CT Scan. The HUAC of the psoas muscles is a measure of muscle density and fatty infiltration. Both the right and left psoas were evaluated and the average was used for the final HUAC calculation. Right Hounsfield Unit Calculation (RHUC) =(Right Hounsfield Unit*Right Psoas Area)/(Total Psoas Area), left Hounsfield Unit Calculation (LHUC) =(Left Hounsfield Unit*Left Psoas Area)/(Total Psoas Area), and HUAC =(Right Hounsfield Unit Calculation +Left Hounsfield Unit Calculation)/2.
