Quantitative regional blood flow measurements in exercising leg skeletal muscle based on 99mTc-pertechnetate...

Skeletal muscle blood flow (SMBF) is a crucial indicator of impaired peripheral circulation. Although 133Xe has long been used for estimation of regional SMBF, its lipophilic and volatile nature hampers precise measurement. Therefore, we established an improved method based on 99mTc-pertechnetate ion (99mTcO-4) clearance.

Ten healthy male volunteers including five rugby players and five non-athletes (each group aged 25-35 years) received injection of 99mTcO-4 into the bilateral tibialis anterior muscles and gastrocnemius muscles (GCMs). The radioactivity of 99mTcO-4 before, during, and after toe-up or treadmill exercise was traced using a gamma-camera. Regional SMBF in absolute values (in ml/min/100 g muscle) was then calculated based on the half-time obtained from the time-activity curve.

In both the groups, SMBF in tibialis anterior muscle changed similarly with values at the same levels. In contrast, SMBF in GCM showed marked difference between the two groups: in rugby players, SMBF in GCM returned to the baseline level (6.5+/-1.7, n=10) immediately after treadmill exercise, whereas that in non-athletes remained high (16.2+/-3.2, n=10).

Regional SMBF measured by 99mTcO-4 clearance can indicate effectiveness of exercise training, and would be a diagnostic tool and prognostic indicator for use in patients with impaired peripheral circulation.