Correlations between Tracer Injection Sites and Lymphatic Pathways in the Leg: A Near-Infrared Fluorescence Lymphography Study

A preliminary investigation of precise visualization, localization, and resection of pelvic lymph nodes in bladder cancer by using indocyanine green fluorescence-guided approach through intracutaneous dye injection into the lower limbs and perineum

Objective

This study aimed to investigate the feasibility and effectiveness of using indocyanine green (ICG) injected intracutaneously through the lower limbs and perineum for visualized tracking, localization, and qualitative assessment of pelvic lymph nodes (LNs) in bladder cancer to achieve their accurate resection.

Methods

First, ICG was injected into the LN metastasis model mice lower limbs, and real-time and dynamic in vivo and ex vivo imaging was conducted by using a near-infrared fluorescence imaging system. Additionally, 26 patients with bladder cancer were enrolled and divided into intracutaneous group and transurethral group. A near-infrared fluorescence imaging device with internal and external imaging probes was used to perform real-time tracking, localization, and resection of the pelvic LNs.

Results

The mice normal LNs and the metastatic LNs exhibited fluorescence. The metastatic LNs showed a significantly higher signal-to-background ratio than the normal LNs (3.9 ± 0.2 vs. 2.0 ± 0.1, p < 0.05). In the intracutaneous group, the accuracy rate of fluorescent-labeled LNs was 97.6%, with an average of 11.3 ± 2.4 LNs resected per patient. Six positive LNs were detected in three patients (18.8%). In the transurethral group, the accuracy rate of fluorescent-labeled LNs was 84.4%, with an average of 8.6 ± 2.3 LNs resected per patient. Two positive LNs were detected in one patient (12.5%).

Conclusion

Following the intracutaneous injection of ICG into the lower limbs and perineum, the dye accumulates in pelvic LNs through lymphatic reflux. By using near-infrared fluorescence laparoscopic fusion imaging, physicians can perform real-time tracking, localization, and precise resection of pelvic LNs.

Effectiveness of lymphaticovenular anastomosis for adult-onset primary lower limb lymphedema: A retrospective study

BACKGROUND

Surgical treatments such as lymphaticovenular anastomosis (LVA) are widely used in addition to conservative treatment of secondary lymphedema. However, their indications and effectiveness for primary lymphedema are unclear. This study aims to objectively demonstrate the effectiveness of LVA for adult-onset primary lymphedema from various perspectives.

METHODS

We retrospectively examined patients with primary lower limb lymphedema who underwent LVA between January 2018 and December 2021 and were 21 or older. Treatment effects were evaluated using lymphoscintigraphy, questionnaires, body mass index, extracellular fluid ratio, and lymphedema index preoperatively and 6 months postoperatively. The LVA was performed under general anesthesia.

RESULTS

We evaluated 11 patients (11 lower limbs). Out of seven patients with complete obstruction preoperatively, all presented partial obstruction according to the Taiwan Lymphoscintigraphy Staging classification with a significant decrease in the score. Significant improvements were observed in clinical symptoms ("hardness") and in quality of life ("appearance" and "ease of wearing compression garments") assessments. A significant change was observed in the extracellular water ratio but not in lower extremity lymphedema index (LELindex).

CONCLUSION

LVA was suggested as one of the potential treatment options for patients with adult-onset primary lymphedema in whom lymphatic flow was confirmed by lymphoscintigraphy. In addition to clinical symptoms and physical examination, the evaluation of adult-onset primary lymphedema should include the patient's quality of life.

Preoperative photoacoustic versus indocyanine green lymphography in lymphaticovenular anastomosis outcomes for lower extremity lymphedema: A pilot study

BACKGROUND

Identification of the proper lymphatics is important for successful lymphaticovenular anastomosis (LVA) for lymphedema; however, visualization of lymphatic vessels is challenging. Photoacoustic lymphangiography (PAL) can help visualize lymphatics more clearly than other modalities. Therefore, we investigated the usefulness of PAL and determined whether the clear and three-dimensional image of PAL affects LVA outcomes.

METHODS

We recruited 22 female patients with lower extremity lymphedema. The operative time, number of incisions, number of anastomoses, lymphatic vessel detection rate (number of functional lymphatics identified during the operation/number of incisions), and limb volume changes preoperatively and 3 months postoperatively were compared retrospectively. The patients were divided according to whether PAL was performed or not, and results were compared between those undergoing PAL (PAL group; n = 10) and those who did not (near-infrared fluorescence [NIRF] group, n = 12).

RESULTS

The mean age of the patients was 55.9 ± 15.1 years in the PAL group and 50.7 ± 14.9 years in the NIRF group. One patient in the PAL group and three in the NIRF group had primary lymphedema. Eighteen patients (PAL group, nine; and NIRF group, nine) had secondary lymphedema. Based on preoperative evaluation using the International Society of Lymphology (ISL) classification, eight patients were determined to be in stage 2 and two patients in late stage 2 in the PAL group. In contrast, in the NIRF group, one patient was determined to be in stage 0, three patients each in stage 1 and stage 2, and five patients in late stage 2. Lymphatic vessel detection rates were 93% (42 LVAs and 45 incisions) and 83% (50 LVAs and 60 incisions) in the groups with and without PAL, respectively (p = 0.42). Limb volume change was evaluated in five limbs of four patients and in seven limbs of five patients in the PAL and NIRF groups as 336.6 ± 203.6 mL (5.90% ± 3.27%) and 52.9 ± 260.7 mL (0.71% ± 4.27%), respectively. The PAL group showed a significant volume reduction. (p = .038).

CONCLUSIONS

Detection of functional lymphatic vessels on PAL is useful for treating LVA.

A new lymphography protocol and interpretation principles based on functional lymphatic anatomy in lower limb lymphedema

Indirect lymphatic system imaging is essential for diagnosing lymphatic diseases. The basic methodology involves intradermal or subcutaneous injection of a contrast agent into the surrounding lymphatic capillary, and the flow of the contrast agent is identified using a detector. Many contrast agents that use near-infrared dye, including indocyanine green (ICG) fluorescent lymphography, are available. ICG is rapidly spreading as a convenient and safe lymphedema diagnostic method, because it does not involve radiation exposure, and the imaging equipment is more compact than other devices. The lymphatic system is a semi-open circulatory system with numerous lymphatic capillaries acting as blind ends. Anatomical information on the injection site and observation of specific lymphatic vessels and nodes is important. However, this anatomical information is lacking. Recent reports suggest that ICG fluorescent lymphography can be applied to cadavers in the same manner as living bodies. Furthermore, these reports have demonstrated the functional aspects of the capillary lymph vessel networks as well as their relationship with lymphatic vessels and lymph nodes. This review article describes the historical progression from the old to the new functional lymphatic anatomy and introduces a new functional lymphography technique for the lower limbs.

MR Lymphangiography in Lymphatic Disorders: Clinical Applications, Institutional Experience, and Practice Development

Lymphatic flow and anatomy can be challenging to study, owing to variable lymphatic anatomy in patients with diverse primary or secondary lymphatic pathologic conditions and the fact that lymphatic imaging is rarely performed in healthy individuals. The primary components of the lymphatic system outside the head and neck are the peripheral, retroperitoneal, mesenteric, hepatic, and pulmonary lymphatic systems and the thoracic duct. Multiple techniques have been developed for imaging components of the lymphatic system over the past century, with trade-offs in spatial, temporal, and contrast resolution; invasiveness; exposure to ionizing radiation; and the ability to obtain information on dynamic lymphatic flow. More recently, dynamic contrast-enhanced (DCE) MR lymphangiography (MRL) has emerged as a valuable tool for imaging both lymphatic flow and anatomy in a variety of congenital and acquired primary or secondary lymphatic disorders. The authors provide a brief overview of lymphatic physiology, anatomy, and imaging techniques. Next, an overview of DCE MRL and the development of an MRL practice and workflow in a hybrid interventional MRI suite incorporating cart-based in-room US is provided, with an emphasis on multidisciplinary collaboration. The spectrum of congenital and acquired lymphatic disorders encountered early in an MRL practice is provided, with emphasis on the diversity of imaging findings and how DCE MRL can aid in diagnosis and treatment of these patients. Methods such as DCE MRL for assessing the hepatic and mesenteric lymphatic systems and emerging technologies that may further expand DCE MRL use such as three-dimensional printing are introduced. ©RSNA, 2024 Test Your Knowledge questions for this article are available in the supplemental material.

Lymphatic-based Lymphosome: A Novel Hypothesis with Clinical Implication for Supermicrosurgical Lymphaticovenous Anastomosis

Understanding the anatomical territories drained by lymphatic vessels (LVs) is essential for a better comprehension of lymphatic anatomy and functionality, and for performing lymphatic procedures such as lymphaticovenous anastomosis (LVA). However, current concepts regarding the lymphatic territory are insufficient to explain some of the clinical observations. As shown in the figures, within one incision for the LVA, one to two lymphatic vessels (LV) remained unenhanced on indocyanine green (ICG) lymphography, whereas the rest of the LVs were enhanced. To answer this question, one must examine the concept of the lymphosome, first described by Suami, defined as a particular region drained by LVs into the same subgroup of regional lymph nodes (LNs) (eg, superficial groin LNs). Suami's lymphosome concept represents "LN-based lymphosomes." In addition, Shinaoka identified four distinct lymphatic groups (anteromedial, anterolateral, posteromedial, and posterolateral) in the lower limbs after ICG injection. This represents the concept "group-based lymphosomes." Nevertheless, neither the LN- nor group-based lymphosome concepts offer an appropriate explanation for the clinical findings described above. In addition to the aforementioned lymphosome concepts, the author proposes a novel hypothesis called "lymphatic-based lymphosome," which considers each LV as a single lymphosome. Therefore, the normal-type LV remained unenhanced when ICG was not injected into the draining territory. To enhance post-LVA outcomes, an even distribution of anastomoses to different group-based lymphosomes is important, as is avoiding performing all anastomoses onto a single LV or within the same group-based lymphosome.

Measurement of lymphatic vessel depth using photoacoustic imaging

OBJECTIVES

Information regarding the depth of lymphatic vessel is important for lymphatic surgeons because rapid identification of functional lymphatic vessels and veins is necessary to perform good lymphaticovenular anastomosis, which is a surgical procedure for lymphedema cases. Photoacoustic lymphangiography (PAL) may be useful for such identification because it allows the assessment of the depth of lymphatic vessels. Thus, we aimed to measure the lymphatic vessel depth using images obtained by PAL.

METHODS

This study included healthy individuals and patients with lymphedema. In all participants, indocyanine green dissolved in dextrose was injected subcutaneously into the first and fourth webs of the foot and the lateral malleolus, and PAL was performed on the medial side of the lower leg. The lymphatic vessel depth was measured from the ankle joint, 10 cm above the medial malleolus, and 20 cm above the medial malleolus on PAL in the cross-sectional view and was compared between the participant groups.

RESULTS

The healthy group (mean age, 43.3 ± 12.9 years) included 21 limbs of 4 male and 16 female healthy individuals (bilateral limbs of 1 patient were considered). The lymphedema group (mean age, 62.0 ± 11.7 years) included 17 limbs of 3 male and 14 female patients with lymphedema. The average lymphatic vessel depths from the ankle joint, 10 cm above the medial malleolus, and 20 cm above the medial malleolus were 2.6, 4.7, and 5.6 mm in the healthy group and 3.6, 7.3, and 7.4 mm in the lymphedema group, respectively. Lymphatic vessels were significantly deeper in the lymphedema group than in the healthy group at all measurement locations.

CONCLUSIONS

Using PAL, we determined the lymphatic vessel depth in living bodies. By searching for the lymphatic vessels based on our findings, even surgeons who are relatively inexperienced with lymphatic surgery may be able to identify functional lymphatic vessels more efficiently.

A new indocyanine green fluorescence lymphography protocol for diagnostic assessment of lower limb lymphoedema

INTRODUCTION

The lower limbs are a common body site affected by chronic edema. Imaging examination of the lymphatic system is useful to diagnose lymphoedema, identify structural changes in individuals, and guide interventional strategies. In this study, we used a protocol combining indocyanine green (ICG) lymphography and ICG-guided manual lymphatic drainage (MLD) for the diagnostic assessment of lower limb lymphoedema.

MATERIALS AND METHODS

Patients with lower limb lymphoedema were divided into three groups by their medical history: primary, secondary cancer-related, or secondary non-cancer-related. ICG lymphography was conducted in three phases: initial observation, MLD to accelerate ICG dye transit and reduce imaging time, and imaging data collection. Lymphatic drainage regions were recorded, and the MD Anderson Cancer Center ICG staging was applied. We collected routine lymphoedema assessment data, including limb volume and bioimpedance spectroscopy measurements.

RESULTS

Three hundred and twenty-six lower limbs that underwent ICG lymphography were analyzed. Eight drainage regions were identified. The ipsilateral inguinal and popliteal were recognized as the original regions, and the remaining six regions were considered compensatory regions that occur only in lymphoedema. More than half of the secondary cancer-related lower limb lymphoedema (57.6%) continued to drain to the ipsilateral inguinal region. The incidence of drainage to the ipsilateral inguinal region was even higher for the primary (82.8%) and secondary non-cancer-related (87.1%) groups. Significant associations were observed between cancer-related lymphoedema and the presence of compensatory drainage regions.

CONCLUSIONS

We proposed a prospective ICG lymphography protocol for the diagnostic assessment of lower limb lymphoedema in combination with MLD. Eight drainage regions were identified, including two original and six compensatory regions.

Anatomical Location of Lymphatic Pathways in the Posterior Thigh

BACKGROUND

It is necessary for treating lower extremity lymphedema to understand the lymphatic pathways in the extremities. This study aimed to clarify the anatomical locations of lymph vessels in the posterior thigh using indocyanine green (ICG) lymphography.

METHODS

Medical records of cancer survivors who underwent ICG lymphography for secondary lymphedema screening from February 2019 to November 2020 were reviewed. Nonlymphedematous limbs without dermal backflow pattern on ICG lymphography (ICG stage 0) were included. Indocyanine green (0.1 mL) was injected intradermally at 2 points in the midlateral thigh, at the levels of one third and two thirds from the popliteal fossa to the gluteal fold in a prone position. Locations of the posterior thigh collecting lymph vessels visualized by ICG lymphography were marked on the skin surface with a pen, and distances from the popliteal fossa to the collecting lymph vessels were measured at the posterior midline in percentage, with the popliteal fossa set as 0% and the gluteal fold as 100%. Based on ICG lymphography findings, the number of the collecting lymph vessels shown as linear pattern and anatomical locations at the posterior thigh midline were investigated.

RESULTS

Twenty limbs of 20 cancer survivors were included. Linear pattern was identified in all lower extremities; average number was 2.3 ± 0.7 (range, 1-3). Most collecting lymph vessels shown on ICG lymphography, 26.7% (12 of 45) lymph vessels, were located within 40% to 50% of the region, and 24.4% (11 of 45) lymph vessels within 30% to 40% of the region.

CONCLUSIONS

There are 1 or more collecting lymph vessels in the posterior thigh by midlateral thigh ICG injection, which can be addressed for posterior thigh lymphedema.

A new severity classification of lower limb secondary lymphedema based on lymphatic pathway defects in an indocyanine green fluorescent lymphography study

Most protocols for lymphatic imaging of the lower limb conventionally inject tracer materials only into the interdigital space; however, recent studies indicate that there are four independent lymphatic vessel groups (anteromedial, anterolateral, posteromedial, and posterolateral) in the lower limb. Thus, three additional injection sites are needed for lymphatic imaging of the entire lower limb. We aimed to validate a multiple injection designed protocol and demonstrate its clinical benefits. Overall, 206 lower limbs undergoing indocyanine green fluorescent lymphography with the new injection protocol were registered retrospectively. To assess the influence of predictor variables on the degree of severity, multivariable logistic regression models were used with individual known risk factors. Using a generalized linear model, the area under the curve (AUC) of the conventional clinical model, comprising known severity risk factors, was compared with that of the modified model that included defects in the posterolateral and posteromedial groups. Multivariable logistic regression models showed a significant difference for the posteromedial and posterolateral groups. The AUC of the modified model was significantly improved compared to that of the conventional clinical model. Finding defects in the posteromedial and posterolateral groups is a significant criterion for judging lymphedema severity and introducing a new lymphedema severity classification.

Selection of Optimal Functional Lymphatic Vessel Cutoff Size in Supermicrosurgical Lymphaticovenous Anastomosis in Lower Extremity Lymphedema

BACKGROUND

Functional lymphatic vessels are essential for supermicrosurgical lymphaticovenous anastomosis. Theoretically, the larger the lymphatic vessel, the better the flow. However, large lymphatic vessels are not readily available. Since the introduction of lymphaticovenous anastomosis, no guidelines have been set as to how small a lymphatic vessel is still worthwhile for anastomosis.

METHODS

In this longitudinal cohort study, unilateral lower limb lymphedema patients who underwent lymphaticovenous anastomosis between March of 2016 and January of 2019 were included. Demographic data and intraoperative findings including the number and size of lymphatic vessels were recorded. The cutoff size was determined by receiver operating characteristic curve analysis, based on the functional properties of lymphatic vessels. Clinical correlation was made with post-lymphaticovenous anastomosis volume measured by magnetic resonance volumetry.

RESULTS

A total of 141 consecutive patients (124 women and 17 men) with a median age of 60.0 years (range, 56.7 to 61.2 years) were included. The cutoff size for a functional lymphatic vessel was determined to be 0.50 mm (i.e., lymphatic vessel0.5) from a total of 1048 lymphatic vessels. Significant differences were found between the number of lymphatic vessels0.5 anastomosed (zero to one, two to three, and greater than over equal to four lymphatic vessels0.5), the median post-lymphaticovenous anastomosis volume reduction (in milliliters) (p < 0.001), and the median percentage volume reduction (p = 0.012).

CONCLUSIONS

Lymphatic vessel0.5 can be a valuable reference for lymphaticovenous anastomosis. Post-lymphaticovenous anastomosis outcome can be enhanced with the use of lymphatic vessel0.5 for anastomoses.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Risk, II.

A phase III, multicenter, single-arm study to assess the utility of indocyanine green fluorescent lymphography in the treatment of secondary lymphedema

OBJECTIVE

Indocyanine green (ICG) fluorescent lymphography might be useful for assessing patients undergoing lymphatic surgery for secondary lymphedema. The present clinical trial aimed to confirm whether ICG fluorescent lymphography would be useful in evaluating lymphedema, identifying lymphatic vessels suitable for anastomosis, and confirming patency of lymphaticovenular anastomosis in patients with secondary lymphedema.

METHODS

The present phase III, multicenter, single-arm, open-label, clinical trial (HAMAMATSU-ICG study) investigated the accuracy of lymphedema diagnosis via ICG fluorescent lymphography compared with lymphoscintigraphy, rate of identification of lymphatic vessels at the incision site, and efficacy for confirming patency of lymphaticovenular anastomosis. The external diameter of the identified lymphatic vessels and the distance from the skin surface to the lymphatic vessels using preoperative ICG fluorescent lymphography were measured intraoperatively under surgical microscopy.

RESULTS

When the clinical decision for surgery at each research site was made, the standard diagnosis of lymphedema was considered correct. For the 26 upper extremities, a central judgment committee who was unaware of the clinical presentation confirmed the imaging diagnosis was accurate for 100.0% of cases, whether the assessments had been performed via lymphoscintigraphy or ICG lymphography. In contrast, for the 88 lower extremities, the accuracy of the diagnosis compared with the diagnosis by the central judgment committee was 70.5% and 88.2% for lymphoscintigraphy and ICG lymphography, respectively. The external diameter of the identified lymphatic vessels was significantly greater in the lower extremities than in the upper extremities (0.54 ± 0.21 mm vs 0.42 ± 0.14 mm; P < .0001). Also, the distance from the skin surface to the lymphatic vessels was significantly longer in the lower extremities than in the upper extremities (5.8 ± 3.5 mm vs 4.4 ± 2.6 mm; P = .01). For 263 skin incisions, with the site placement determined using ICG fluorescent lymphography, the rate of identification of lymphatics vessels suitable for anastomosis was 97.7% (95% confidence interval, 95.1%-99.2%). A total of 267 lymphaticovenular anastomoses were performed. ICG fluorescent lymphography was judged as "useful" for confirming patency after the anastomosis in 95.1% of the cases.

CONCLUSIONS

ICG fluorescent lymphography could be useful for improving the treatment of patients with secondary lymphedema from the outpatient setting to surgery.

Preliminary outcomes of combined surgical approach for lower extremity lymphedema: supraclavicular lymph node transfer and lymphaticovenular anastomosis

BACKGROUND

Vascularized lymph node transfer (VLNT) is a well-established surgical approach for treating lower extremity lymphedema (LEL). Since VLNT takes time to show effect, a combined approach with lymphaticovenular anastomosis (LVA) may be more advantageous to patients by inducing an immediate improvement. This study aims to describe our experience and evaluate the results of a combined approach.

METHODS

In this retrospective review, we analyzed a total of 12 patients that underwent simultaneous supraclavicular VLNT and LVA for the treatment of secondary LEL with the ISL stage II or III. Patients who had a follow-up period of less than 12 months were excluded. The supraclavicular flap, including superficial lymphoid tissue as well as deep cervical nodes, was harvested and anastomosed to the posterior tibial vessels. The pre- and postoperative change of circumference difference ratios and LEL index were compared.

RESULTS

All twelve flaps survived without re-exploration. An average of 2.3 LVAs were simultaneously performed. At 12.9 months of follow-up (range, 12-16 months), the postoperative mean circumference ratio was significantly improved than pre-operative in 10 cm above the knee (7.9 ± 7.2% vs 15.0 ± 7.6%, p = 0.01), 10 cm below the knee (8.5 ± 7.5% vs 17.4 ± 12.7%, p = 0.03) and lateral malleolus (16.5 ± 15.5% vs 28.6 ± 17.9%, p = 0.03). Also, the mean LEL index was decreased (preoperative 324.3 ± 53.0 vs postoperative 298.0 ± 44.6, p = 0.242) and eight patients showed improvement in LEL stage.

CONCLUSIONS

The combined approach showed a significant decrease in the circumference of LEL. Additional LVAs could reinforce the effect of a VLNT. Larger series with longer follow-up is needed to confirm our findings.

Impact of Magnetic Resonance Lymphography on Lymphaticolvenular Anastomosis for Lower-Limb Lymphedema

BACKGROUND

 Although several investigations have described the safety, utility, and precision of magnetic resonance lymphography (MRL) as a preoperative examination for lymphaticovenular anastomosis (LVA), it is unclear how much MRL assistance impacts LVA results. The present study aimed to clarify the outcome of MRL-assisted LVA for leg lymphedema using body water measurements obtained by bioelectrical impedance analysis.

METHODS

 The water reductive effect of MRL-assisted LVA in female secondary leg lymphedema patients was compared with that of non-MRL-assisted controls in this retrospective study. In the MRL-assisted group, all LVA candidates underwent MRL prior to surgery, and the lymphatic vessels to be anastomosed were primarily determined by MRL findings. The body water composition of the treated legs was assessed before LVA and at 6 months postoperatively using a multi-frequency bioelectrical impedance analyzer.

RESULTS

 Twenty-three patients in the MRL-assisted study group and an equal number in the non-MRL-assisted control group were analyzed. Although mean leg water volume before LVA, mean excess water volume of the affected leg before LVA, and number of anastomoses created were comparable between the groups, the water volume reduction (1.02 L versus 0.49 L; 95% confidence interval [CI]: 0.03-1.03, p < 0.05) and edema reduction rate (46.7% versus 27.2%; 95% CI: 3.7-35.5%, p < 0.05) in the MRL-assisted group were significantly greater than in controls.

CONCLUSION

 Preoperative MRL-assisted lymph vessel visualization and selection appeared to significantly enhance the water reductive effect of LVA for International Society of Lymphology classification stage 2 leg lymphedema. MRL also helped to reliably identify lymphatic vessels for anastomosis. Without increasing the number of anastomoses, LVA could be performed more effectively by better detecting stagnant lymphatic vessels using MRL.

Eyelid Lymphatics: An Anatomical Study by Microdissection

OBJECTIVE

To obtain further understanding of the eyelid lymphatic anatomy.

METHOD

Thirty-two halves of eyelids from 16 fresh fetus cadavers were studied by microdissection using a mixture of 3% Prussian blue and chloroform to visualize the lymphatic vessels.

RESULTS

Three layers of lymphatic plexuses were demonstrated in the eyelids: a superficial or preorbicularis muscle plexus; a pretarsal or postorbicular muscle plexus; and a deep or posttarsal plexus. Furthermore, communicating branches among these plexuses were also spotted.

CONCLUSIONS

The study results demonstrated the topographic distribution of the eyelid lymphatic vessels and confirmed the existence of communicating branches. This discovery will be conducive to understanding the route and mechanism by which inflammation of the eyelid spreads and cancer disseminates. It also provides anatomical insights to apply during eyelid surgery with regard to the prevention of possible eyelid lymphatic injury.

Use of photoacoustic imaging to determine the effects of aging on lower extremity lymphatic vessel function

OBJECTIVE

Aging is one of the causes of primary lymphedema. However, the effects of aging on the lymphatic system are still not completely understood. We investigated the effects of aging on the lymphatic vessels in the lower extremities of healthy volunteers using photoacoustic imaging.

METHODS

Healthy volunteers who underwent photoacoustic lymphangiography between March 2018 and January 2019 were enrolled. To visualize lymphatics, indocyanine green (ICG, 5.0 mg/mL) was injected subcutaneously into the first and fourth web spaces of the foot and under the lateral malleolus. Subsequently, near-infrared fluorescence lymphography was performed to confirm good ICG flow, and photoacoustic lymphangiography was performed on the medial side of the lower leg. Neodymium-doped yttrium aluminum garnet laser irradiation at 797 and 835 nm, the optimal wavelengths for visualizing ICG and blood, was applied. The number of lymphatic vessels shown at areas 10 cm (L10) and 20 cm (L20) cranially from the internal malleolus was counted.

RESULTS

Nineteen healthy volunteers (4 males and 15 females) were enrolled in the study. Their mean age was 42.9 ± 12.8 years. One volunteer was bilaterally imaged; 15 left lower limbs and 5 right lower limbs were imaged. The number of lymphatic vessels visualized increased with age. There were strong positive correlations between age and L10 (R = 0.729, P < .001) and between age and L20 (R = 0.570, P = .009).

CONCLUSIONS

Photoacoustic imaging indicates that the number of lymphatic vessels increases with age. Lymphatic stasis resulted in visualization of not only normal drainage pathways but also nonfunctional lymphatic pathways.

Establishing a Lymphatic Venous Anastomotic Training Model in Pig Trotters

BACKGROUND

 Lymphatic venous anastomosis (LVA) is a widely accepted surgical procedure for lymphedema. To obtain the best outcomes, surgeons should be well trained. A recent study introduced an LVA training model using pig trotters for their utility and structural similarity to human tissues. However, details regarding the utilization of anastomosis models, such as feasible points for training based on vessel anatomy, have not been clarified. Therefore, we assessed the anatomical details of lymphatic vessels and veins of trotters to establish a practical training model of LVA.

METHODS

 Ten frozen trotters were used. After thawing at room temperature, indocyanine green fluorescent lymphography was used to visualize the lymphatic course. To dissect the lymphatic vessels and veins from the distal to the proximal end, whole skins were detached thoroughly from the plantar side. Data from the lymphatic vessels and veins were collected based on their courses, diameters, and layouts to clarify adjacent points feasible for LVA training.

RESULTS

 Both lymphatic vessels and veins were classified into four major courses: dorsal, medial, lateral, and plantar. The majority were dorsal vessels, both lymphatic vessels and veins. The adjacent points were always found in the distal dorsum center and were especially concentrated between the metacarpophalangeal (MP) joint and central interphalangeal crease, followed by the medial and lateral sides.

CONCLUSION

 The most relevant point for LVA surgical training in the trotter was the dorsal center distal to the MP joint, where parallel vessels of similar sizes were found in all cases. This practical LVA surgical model would improve surgeon skills in not only anastomosis but also preoperative fluorescent lymphography.

Visualization of Lymphatic Vessels Using Photoacoustic Imaging

Lymphedema occurs when interstitial fluid and fibroadipose tissues accumulate abnormally because of decreased drainage of lymphatic fluid as a result of injury, infection, or congenital abnormalities of the lymphatic system drainage pathway. An accurate anatomical map of the lymphatic vasculature is needed not only for understanding the pathophysiology of lymphedema but also for surgical planning. However, because of their limited spatial resolution, no imaging modalities are currently able to noninvasively provide a clear visualization of the lymphatic vessels. Photoacoustic imaging is an emerging medical imaging technique that provides unique scalability of optical resolution and acoustic depth of penetration. Moreover, light-absorbing biomolecules, including oxy- and deoxyhemoglobin, lipids, water, and melanin, can be imaged. Using exogenous contrast agents that are taken up by lymphatic vessels, e.g., indocyanine green, photoacoustic lymphangiography, which has a higher spatial resolution than previous imaging modalities, is possible. Using a new prototype of a photoacoustic imaging system with a wide field of view developed by a Japanese research group, high-resolution three-dimensional structural information of the vasculatures was successfully obtained over a large area in both healthy and lymphedematous extremities. Anatomical information on the lymphatic vessels and adjacent veins provided by photoacoustic lymphangiography is helpful for the management of lymphedema. In particular, such knowledge will facilitate the planning of microsurgical lymphaticovenular anastomoses to bypass the excess fluid component by joining with the circulatory system peripherally. Although challenges remain to establish its implementation in clinical practice, photoacoustic lymphangiography may contribute to improved treatments for lymphedema patients in the near future.

Extensive Perineural Spread of Subungual Melanoma

BACKGROUND

Subungual melanoma (SUM) is a rare form of melanoma confined to the nailbed and is rarely of the desmoplastic subtype. The often subtle nature of SUM, initially starting as a small dark spot or line in the nailbed, means deeper invasion can occur before a patient seeks clinical evaluation for a large, ulcerated lesion. We report the only known case of perineural spread of SUM of the lower extremity and describe its extensive path of perineural spread from the toe.

CASE DESCRIPTION

A 72-year-old man with a distant history of SUM status post second ray amputation, presented for evaluation of ipsilateral foot drop. Imaging revealed nodular involvement of tibial, peroneal, and sciatic nerves. Biopsies revealed desmoplastic melanoma and he was treated with nivolumab.

CONCLUSIONS

We report the only known case of perineural spread of SUM of the lower extremity and describe the pathoanatomy of perineural spread. A high index of suspicion for recurrent disease should be maintained even many years after completion of treatment.

HAMAMATSU-ICG study: Protocol for a phase III, multicentre, single-arm study to assess the usefulness of indocyanine green fluorescent lymphography in assessing secondary lymphoedema

Introduction

Secondary lymphoedema of the extremities is an important quality-of-life issue for patients who were treated for their malignancies. Indocyanine green (ICG) fluorescent lymphography may be helpful for assessing lymphoedema and for planning lymphaticovenular anastomosis (LVA). The objective of the present clinical trial is to confirm whether or not ICG fluorescent lymphography using the near-infrared monitoring camera is useful for assessing the indication for LVA, for the identification of the lymphatic vessels before the conduct of LVA, and for the confirmation of the patency of the anastomosis site during surgery.

Methods and analysis

This trial is a phase III, multicentre, single-arm, open-label clinical trial to assess the efficacy and safety of ICG fluorescent lymphography when assessing and treating lymphoedema of patients with secondary lymphoedema who are under consideration for LVA. The primary endpoint is the identification rate of the lymphatic vessels at the incision site based on ICG fluorescent lymphograms obtained before surgery. The secondary endpoints are 1) the sensitivity and specificity of dermal back flow determined by ICG fluorescent lymphography as compared with ^99mTc lymphoscintigraphy—one of the standard diagnostic methods and 2) the usefulness of ICG fluorescent lymphography when confirming the patency of the anastomosis site after LVA.

Ethics and dissemination

The protocol for the study was approved by the Institutional Review Board of each institution. The trial was filed for and registered at the Pharmaceuticals and Medical Devices Agency in Japan. The trial is currently on-going and is scheduled to end in June 2020.

Trial registration number

jRCT2031190064; Pre-results.

•

This study will examine the efficacy of a highly safe drug, indocyanine green for evaluating lymphatic anatomy.

•

This is the first, multicentre, prospective, systematised clinical trial of Indocyanine green lymphography.

•

The present clinical trial will not allow the assessment of the therapeutic efficacy of lymphaticovenular anastomosis.

Anatomical Theories of the Pathophysiology of Cancer-Related Lymphoedema

Lymphoedema is a well-known concern for cancer survivors. A crucial issue in lymphoedema is that we cannot predict who will be affected, and onset can occur many years after initial cancer treatment. The variability of time between cancer treatment and lymphoedema onset is an unexplained mystery. Retrospective cohort studies have investigated the risk factors for lymphoedema development, with extensive surgery and the combination of radiation and surgery identified as common high-risk factors. However, these studies could not predict lymphoedema risk in each individual patient in the early stages, nor could they explain the timing of onset. The study of anatomy is one promising tool to help shed light on the pathophysiology of lymphoedema. While the lymphatic system is the area least investigated in the field of anatomical science, some studies have described anatomical changes in the lymphatic system after lymph node dissection. Clinical imaging studies in lymphangiography, lymphoscintigraphy and indocyanine green (ICG) fluorescent lymphography have reported post-operative anatomical changes in the lymphatic system, including dermal backflow, lymphangiogenesis and creation of alternative pathways via the deep and torso lymphatics, demonstrating that such dynamic anatomical changes contribute to the maintenance of lymphatic drainage pathways. This article presents a descriptive review of the anatomical and imaging studies of the lymphatic system in the normal and post-operative conditions and attempts to answer the questions of why some people develop lymphoedema after cancer and some do not, and what causes the variability in lymphoedema onset timing.

Lower-Limb Lymphatic Drainage Pathways and Lymph Nodes: A CT Lymphangiography Cadaver Study

Background Most lymphatic imaging examinations of the lower limb require intradermal or subcutaneous injection of tracer material into the foot to demonstrate the lymphatic vessels; however, no standard protocol exists, and single or multiple injections are applied at different sites. Purpose To determine the three-dimensional relationships between each lymphatic group of the lower limb and corresponding regional lymph nodes. Materials and Methods A total of 130 lower limbs (55 from men and 75 from women) from 83 fresh human cadavers were studied. Lymphatic vessels were first visualized by using indocyanine green fluorescent lymphography with 19 injection sites in the foot, classified into four distinct lymphatic groups (anteromedial, anterolateral, posteromedial, and posterolateral); dilute oil-based contrast material was then injected. Next, specimens were scanned with CT and three-dimensional images were analyzed. Results The anteromedial and anterolateral lymphatic groups of the lower-leg lymphatic vessels were independent of each other and connected to different regional lymph nodes in the inguinal region. The posteromedial group and the anteromedial group in the lower leg drained to the same inguinal lymph nodes. Only the posterolateral group of lymphatic vessels in the lower leg drained to the popliteal lymph nodes. Leg lymphatic drainage pathways were independent of genital pathways. Conclusion Standard injection sites at the web spaces between the toes did not help visualize some lymph nodes of the lower leg. Additional injection sites in the medial, lateral, and posterior aspect of the foot would be better for evaluating the whole lymphatic pathways and regional lymph nodes and for improving understanding of leg lymphedema. © RSNA, 2019 Online supplemental material is available for this article. See also the editorial by Weiss and Liddel in this issue.