A Scintigraphic Method for Quantitation of Lymphatic Function in Arm Lymphedema

Lymphoscintigraphy is commonly used to assess breast cancer-related lymphedema. However, a reliable quantitative method that clearly distinguishes normal lymphatic function from lymphedema is desired. We propose a quantitative method based upon the physiological mean transit time (MTT) measure of lymph fluid passing through the arm.

Eleven patients, aged 34-68 years, with unilateral arm lymphedema following breast cancer treatment underwent simultaneous bilateral lymphoscintigraphy using intradermal injection of ^99mTc-labeled human serum albumin (HSA). Imaging was performed at 30-45 minute intervals for 5 hours. Time activity curves from each injection site and each arm region were recorded. The input into the arm region was obtained as the (minus) time derivative of the injection site activity curve. In the proposed model the arm activity curve was considered to arise from the convolution of the retention function and the input function. The retention function was obtained by fitting the calculated arm activity curve to the measured arm activity curve. The MTT of activity passing through the arm was calculated as the time integral of the resulting retention function. All measured time activity curves were well described by the model. The MTT of the lymphedema arm (mean 60.1 minutes, range 22-105 minutes) was markedly different from that of the contralateral normal arm (mean 5.4 minutes, range 1.2-8.7 minutes), p < 0.0001.

The proposed model showed great similarity with measured time activity curves and was capable of quantitatively distinguishing lymphatic function of the lymphedema arm from that of the normal arm in terms of calculated MTT.