68Ga-NOTA-Evans Blue TOF PET/MR Lymphoscintigraphy Evaluation of the Severity of Lower Limb Lymphedema

Abstract

Purpose: This study was designed to investigate the role of Ga-NOTA-Evans Blue (NEB) time-of-flight (TOF) PET/MR in evaluating lower limb lymphedema by visual analysis and novel parameters.

Methods: Thirteen patients with unilateral lower limb lymphedema were divided into 3 groups according to the clinical severity: minimal (4 patients), moderate (5 patients), and severe (4 patients). All patients underwent Ga-NEB TOF PET/MR lymphoscintigraphy. The ratio of the standardized uptake value (SUV) of superficial lymphatic vessel (SLV) versus SUV of deep lymphatic vessel (DVL) (SUVslv/dlv) was designed to assess the level of lymphedema severity. The correlation between lymphedema severity and lymphoscintigraphy findings was determined using 1-way analysis of variance, the t test, and Pearson correlation analysis.

Results: There was a significant difference in the SUVslv between the affected limbs and normal limbs in all subjects (affected limbs: 0.57 ± 0.32, normal limbs: 1.86 ± 1.43; P < 0.05), which was not found in the SUVdlv (affected limbs: 0.64 ± 0.39, normal limbs: 0.63 ± 0.31; P > 0.1). The SUVslv/dlv of the affected limbs showed statistical differences within the 3 groups (P < 0.05) (minimal group: 1.91 ± 0.45; moderate group: 0.84 ± 0.16; severe group: 0.42 ± 0.11). The statistical analysis revealed a negative correlation between SUVslv/dlv and the severity of lymphedema (r = -0.899; P < 0.01).

Conclusions: Ga-NEB TOF PET/MR lymphoscintigraphy can provide anatomical and functional information of lymphatic vessels to guide surgery plans. SUVslv/dlv was well correlated with clinical lymphedema severity and might be potential in evaluating bilateral lower limb lymphedema.

Fig. 1.

(a) A 50-year-old female patient had lymphedema in the left lower limb for 2 years (minimal group). (b) A 54-year-old female patient had lymphedema in the right lower extremity for 4 years (moderate group). (c) A 57-year-old female patient had lymphedema in the left lower limb for 2 years (severe group). (a-c) Observed by vision, the swelling level gradually increased from the minimal group to the severe group. (d) ^99mTc-SC lymphoscintigraphy was performed 6 hours after subcutaneous injection of the radiotracer, showing dermal backflow in the left extremity and reduced visualization of the left inguinal lymph nodes. (e) ^99mTc-SC lymphoscintigraphy was performed 6 hours after subcutaneous injection of ^99mTc-SC, revealing dermal backflow in the right limb and decreased tracer uptake in the right inguinal lymph nodes. (f) ^99mTc-SC lymphoscintigraphy indicated dermal backflow in the left limb and decreased tracer uptake in the left inguinal lymph nodes.

Fig. 2.

(a-f) ⁶⁸Ga-NEB TOF PET/MR lymphoscintigraphy presented the visualization of DLVs (red arrow) and SLVs (yellow arrow). The lymphatic circulation of the lower extremity could be observed on MIP (a and d, minimal group; b and e, moderate group; c and f, severe group). (a) The PET image showed dermal flowback and reduced inguinal lymph node visualization 20 mins after injection. (b) The PET image 20 mins after subcutaneous injection revealed dermal flowback and decreased inguinal lymph node visualization. (c) The PET image 20 mins after subcutaneous injection showed dermal flowback and decreased inguinal lymph node visualization. (d-f) The axial fusion images indicated that the ⁶⁸Ga-NEB accumulation in the SLVs of the affected limb was less than that of the normal limb (yellow arrows), and the ⁶⁸Ga-NEB accumulation in the DLVs of the affected limb was equal to that of the normal limb (red arrows). There was also much more adipose fat deposition around the SLV than around the DLV.

Fig. 3.

There was a significant difference between the SUV_slv of the affected limb and normal limb (P<0.05).

Fig. 4.

No significant difference was found between the SUV_dlv of the affected limb and normal limb (P>0.1).

Fig. 5.

The SUV_slv/dlv of the affected limb showed statistical differences among all three groups (P<0.05). The statistical analysis revealed a negative correlation between the SUV_slv/dlv and severity of lymphedema (r = −0.899, P<0.01).