Value of combined application of interstitial MR lymphangiography and heavily T₂WI in the lower extremity with lymphedema

Objective: To access the value of combined application of high-resolution interstitial MR lymphangiography (MRL) and heavily T₂WI for the visualization of lymphatic vessels in patients with primary lymphedema. Methods: Forty lower extremities in 31 patients with primary lymphedema were examined by heavily T₂WI and interstitial MRL with a 3.0 T MR unit (Philips Medical Systems, Best, the Netherlands). Two experienced radiologists analyzed the images and tried to determine the differences in number of lymphatic vessels, and their maximum diameters, SNR and CNR, and accumulated lymph fluid in the tissue.Statistical analyses were conducted by using Wilcoxon test and t test. Results: Dilated lymphatic vessels in 73 leg segments of 40 lower extremities were visualized on heavily T₂WI (median 5, 1 to 24), which were more than those on MRL (median 3, 1 to 16) (Z=-2.92, P<0.01). The maximum diameter of lymphatic vessels was (4.3 ± 1.5) mm on heavily T₂WI, whereas it was (3.4 ± 1.0) mm on MRL (t=6.90, P<0.0 1). The average SNR and CNR in the dilated lymphatic vessels were 257 ± 130, 207 ± 113 on MRL and 169 ± 91, 135 ± 82 on heavily T₂WI, which was statistically significant (SNR t=- 5.95, CNR t=-5.10; P<0.01). The visualization of regions of accumulated lymph fluid on heavily T₂WI (median 1) had a higher score than that on MRL (median 0) (Z=-5.64, P<0.01). Conclusions: The heavily T₂WI has greater sensitivity and the MRL image has better SNR and CNR. Combining these two MR techniques can provide adequate information for clinicians in the therapeutic planning of patients with advanced stages of lymphedema. (authors)