Imaging Modalities for Evaluating Lymphedema

Abstract

Lymphedema is a progressive condition. Its therapy aims to reduce edema, prevent its progression, and provide psychosocial aid. Nonsurgical treatment in advanced stages is mostly insufficient. Therefore-in many cases-surgical procedures, such as to restore lymph flow or excise lymphedema tissues, are the only ways to improve patients' quality of life. Imaging modalities: Lymphoscintigraphy (LS), near-infrared fluorescent (NIRF) imaging-also termed indocyanine green (ICG) lymphography (ICG-L)-ultrasonography (US), magnetic resonance lymphangiography (MRL), computed tomography (CT), photoacoustic imaging (PAI), and optical coherence tomography (OCT) are standardized techniques, which can be utilized in lymphedema diagnosis, staging, treatment, and follow-up. Conclusions: The combined use of these imaging modalities and self-assessment questionnaires deliver objective parameters for choosing the most suitable surgical therapy and achieving the best possible postoperative outcome.

Keywords: computed tomography (CT); indocyanine green (ICG); lymphedema; lympho-venous anastomosis (LVA); lymphoscintigraphy (LS); magnetic resonance lymphangiography (MRL); near-infrared fluorescent (NIRF) imaging; optical coherence tomography (OCT); photoacoustic imaging (PAI); ultrasonography (US).

Figure 1

Ultra-high-frequency ultrasound (48 MHz probe) accurately reveals lymphatic vessels and neighboring veins. The green arrow indicates the lymphatic collector; the blue arrow shows the vein.

Figure 2

Lymphoscintigraphy (LS) reveals the lymphatic flow insufficiency. (A) Anteroposterior (AP) transmission LS scan shows the early distribution of the tracer; proximal lymph nodes can be observed. (B) Posteroanterior (PA) scan, early distribution. (C) AP LS scan demonstrates the late distribution of the isotope, showing lymphatic retention on the medial calf on the right side. (D) PA scan, late distribution.

Figure 3

Taiwan Lymphoscintigraphy Staging differentiates lymphedema into 3 patterns and 7 stages: L0, normal drainage; P1–3, partial obstruction; T4–6, total obstruction. Cited with permission [41].

Figure 4

(A) Lymphovenous anastomosis (LVA). An ecstatic lymphatic vessel (left side) is anastomosed to a reflux-free vein (right side). Wash-out of blood can be observed from the distal part of the vein to the patent venous valve. (B) Microscope-integrated intraoperative ICG-L ensures the patency of lympho-venosus anastomosis.

Figure 5

Presentation of indocyanine green (ICG) lymphography on a specific lymphatic vessel, which is for lymphovenous anastomosis operation. (A) ICG lymphography markings on the skin (the green arrow indicates the lymphatic vessel, the blue arrow shows at the vein). Linear and dermal backflow (DB) patterns are indicated differently. (B) ICG lymphography patterns on the same region. (C) The previously detected lymphatic collector is dissected and verified under microscope. (D) Microscope-integrated ICG lymphography shows the functional lymphatic vessel. (E) The anastomosis is made with 11-0 non-absorbable monofil sutures. (F) Microscope-integrated ICG lymphography ensures the patency of the anastomosis and excludes any leakage. Lymphatic flow washes out blood from the vein.

Figure 6

MRL of a patient with lower limb primary lymphedema. Hyperplasic lymphatic vessels and inguinal lymph nodes (arrow) of the right lower extremity are visible [55].

Figure 7

The medial view of the right lower extremity of a woman in her thirties without any past medical history registered with photoacoustic/optoacoustic lymphangiography. (A) Both venules and lymphatic vessels are shown. (B) Only lymphatic vessels are shown. Cited with permission. [65].

Figure 8

Lymphatic vessel photographed (A), the green square in A shows the area imaged with a microscope-integrated NIRF camera (B) and the green line in B indicates the position of the crossectional image captured with a microscope-integrated OCT (C). The diameter and wall-thickness of vessels can be measured precisely on the OCT images [70].