Current diagnostic and quantitative techniques in the field of lymphedema management: a critical review

Lymphedema evaluation entails multifaceted considerations for which options continue to evolve and emerge. This paper provides a critical review of the current status of diagnostic and quantitative measures for lymphedema, from traditional and novel bedside assessment tools for volumetric and fluid assessment, to advanced imaging modalities. Modalities are contrasted with regard to empirical support and feasibility of clinical implementation. The manuscript proposes a grid framework for comparing the ability of each modality to quantify specific lymphedema characteristics, including distribution, dysmorphism, tissue composition and fluid content, lymphatic anatomy and function, metaplasia, clinical symptoms, and quality of life and function. This review additionally applies a similar framework approach to consider how well assessment tools support important clinical needs, including: (1) screening, (2) diagnosis and differential diagnosis, (3) individualization of treatment, and (4) monitoring treatment response. The framework highlights which clinical needs are served by an abundance of assessment tools and identifies others that have problematically few. The framework clarifies which tools have greater or lesser empirical support. The framework is designed to assist stakeholders in selecting appropriate diagnostic and surveillance modalities, gauging levels of confidence when applying tools to specific clinical needs, elucidating overarching patterns of diagnostic and quantitative strengths and weaknesses, and informing future investigation.

Comparison of the Pharmacokinetics of Gadolinium-Based and Iron Oxide-Based Contrast Agents inside the Lymphatic Structure using Magnetic Resonance Lymphangiography

PURPOSE

Gadolinium (Gd)-based contrast agents are primarily used for contrast-enhanced magnetic resonance lymphangiography (MRL). However, overcoming venous contamination issues remains challenging. This study aims to assess the MRL efficacy of the newly developed iron-based contrast agent (INV-001) that is specially designed to mitigate venous contamination issues. The study further explores the optimal dosage, including both injection volume and concentration, required to achieve successful visualization of the popliteal lymph nodes and surrounding lymphatic vessels.

PROCEDURES

All animals utilized in this study were male Sprague-Dawley (SD) rats weighing between 250 and 300 g. The contrast agents prepared were injected intradermally in the fourth phalanx of both hind limbs using a 30-gauge syringe in SD rats. MRL was performed every 16 min on a coronal 3D time-of-flight sequence with saturation bands using a 9.4-T animal machine.

RESULTS

Contrary to Gd-DOTA, which exhibited venous contamination in most animals irrespective of injection dosages and conditions, INV-001 showed no venous contamination. For Gd-DOTA, the popliteal lymph nodes and lymphatic vessels reached peak enhancement 16 min after injection from the injection site and then rapidly washed out. However, with INV-001, they reached peak enhancement between 16 and 32 min after injection, with prolonged visualization of the popliteal lymph node and lymphatic vessels. INV-001 at 0.45 μmol (15 mM, 30 μL) and 0.75 μmol (15 mM, 50 μL) achieved high scores for qualitative image analysis, providing good visualization of the popliteal lymph nodes and lymphatic vessels without issues of venous contamination, interstitial space enhancement, or lymph node enlargement.

CONCLUSION

In MRL, INV-001, a novel T1 contrast agent based on iron, enables prolonged enhancement of popliteal lymph nodes and lymphatic vessels without venous contamination.

Magnetic resonance lymphangiography: Establishing normal

BACKGROUND

Despite an increased interest in visualizing the lymphatic vessels with magnetic resonance lymphangiography (MRL), little literature is available describing their appearance in nonlymphedematous individuals. To determine lymphatic abnormalities, an understanding of how healthy lymphatic vessels appear and behave needs to be established. Therefore, in this study, MRL of individuals without a history of lymphatic disease was performed.

METHODS

A total of 25 individuals (15 women) underwent MRL of their lower limbs using a 3.0 T Philips magnetic resonance imaging scanner (Philips Medical Systems). The first nine participants were recruited to establish the concentration of gadolinium-based contrast agent (GBCA) to administer, with the remainder imaged before and after interdigital forefoot GBCA injections at the optimized dose. Outcomes, including lymphatic vessel diameter, tortuosity, and frequency of drainage via particular drainage routes, were recorded.

RESULTS

Healthy lymphatic vessels following the anteromedial pathway were routinely observed in post-contrast T1-weighted images (average tortuosity, 1.09 ± 0.03), with an average of 2.16 ± 0.93 lymphatic vessels with a diameter of 2.47 ± 0.50 mm crossing the anterior ankle. In six limbs, vessels following the anterolateral pathways were observed. No vessels traversing the posterior of the legs were seen. In a subset of 10 vessels, the lymphatic signal, measured at the ankle, peaked 29 minutes, 50 seconds ± 9 minutes, 29 seconds after GBCA administration. No lymphatic vessels were observed in T2-weighted images.

CONCLUSIONS

Contrast-enhanced MRL reliably depicts the lymphatic vessels in the legs of healthy controls. Following interdigital contrast injection, anteromedial drainage appears dominant. Quantitative measures related to lymphatic vessel size, tortuosity, and drainage rate are readily obtainable and could be beneficial for detecting even subtle lymphatic impairment.

State-of-the-art imaging for children with central lymphatic disorders

Lymphatic imaging plays a crucial role in novel lymphatic interventions, offering valuable insights into central lymphatic drainage. Lymphatic system abnormalities may appear in various pediatric disorders, and accurate imaging is crucial for effective diagnosis and tailored therapeutic interventions. Traditional imaging modalities have offered valuable insights, but the demand for non-invasive, high-resolution techniques has fueled the development of innovative lymphatic imaging methods. In this review, we explore the state of the art in lymphatic imaging specifically within the context of pediatric surgery.

Analysis on efficacy of magnetic resonance lymphangiography using INV-001 in healthy beagle dogs

We aimed to conduct a proof-of-concept study of INV-001 in visualizing lymphatic vessels and nodes without venous contamination and to determine the optimal dose condition of INV-001 for magnetic resonance lymphangiography (MRL) in healthy beagles. MRL was performed using a 3.0-Tesla (T) whole body clinical magnetic resonance imaging (MRI) scanner. A dose-finding study of INV-001 for MRL in beagles (N = 6) was carried out according to an adaptive optimal dose finding design. For the reproducibility study (N = 6), MRL was conducted at selected INV-001 doses (0.056 and 0.112 mg Fe/kg) with a 15 mM concentration. Additionally, an excretion study (N = 3) of INV-001 was conducted by analyzing T1, T2, and T2* maps of the liver and kidney 48 h post-administration. INV-001 administration at doses of 0.056 and 0.112 mg Fe/kg (concentration: 15 mM) consistently demonstrated the visualization of contrast-enhanced lymphatic vessels and nodes without venous contamination in the beagles. The contrast enhancement effect was highest at 30 min after INV-001 administration, then gradually decreasing. No toxicity-related issues were identified during the study. After 48 h, the T1, T2, and T2* values in the liver and both kidneys were found to be comparable to the pre-administration values, indicating thorough INV-001 excretion. The optimal dosing conditions of INV-001 for MRL for contrast-enhanced visualization of lymphatic vessels and nodes exclusively with no venous contamination in beagles was determined to be 0.056 mg Fe/kg with a 15 mM concentration.

Novel Techniques in Imaging Congenital Heart Disease: JACC Scientific Statement

Recent years have witnessed exponential growth in cardiac imaging technologies, allowing better visualization of complex cardiac anatomy and improved assessment of physiology. These advances have become increasingly important as more complex surgical and catheter-based procedures are evolving to address the needs of a growing congenital heart disease population. This state-of-the-art review presents advances in echocardiography, cardiac magnetic resonance, cardiac computed tomography, invasive angiography, 3-dimensional modeling, and digital twin technology. The paper also highlights the integration of artificial intelligence with imaging technology. While some techniques are in their infancy and need further refinement, others have found their way into clinical workflow at well-resourced centers. Studies to evaluate the clinical value and cost-effectiveness of these techniques are needed. For techniques that enhance the value of care for congenital heart disease patients, resources will need to be allocated for education and training to promote widespread implementation.

Back to the Future II-A Comprehensive Update on the Rapidly Evolving Field of Lymphatic Imaging and Interventions

ABSTRACT

Lymphatic imaging and interventional therapies of disorders affecting the lymphatic vascular system have evolved rapidly in recent years. Although x-ray lymphangiography had been all but replaced by the advent of cross-sectional imaging and the scientific focus shifted to lymph node imaging (eg, for detection of metastatic disease), interest in lymph vessel imaging was rekindled by the introduction of lymphatic interventional treatments in the late 1990s. Although x-ray lymphangiography is still the mainstay imaging technique to guide interventional procedures, several other, often less invasive, techniques have been developed more recently to evaluate the lymphatic vascular system and associated pathologies. Especially the introduction of magnetic resonance, and even more recently computed tomography, lymphangiography with water-soluble iodinated contrast agent has furthered our understanding of complex pathophysiological backgrounds of lymphatic diseases. This has led to an improvement of treatment approaches, especially of nontraumatic disorders caused by lymphatic flow abnormalities including plastic bronchitis, protein-losing enteropathy, and nontraumatic chylolymphatic leakages. The therapeutic armamentarium has also constantly grown and diversified in recent years with the introduction of more complex catheter-based and interstitial embolization techniques, lymph vessel stenting, lymphovenous anastomoses, as well as (targeted) medical treatment options. The aim of this article is to review the relevant spectrum of lymphatic disorders with currently available radiological imaging and interventional techniques, as well as the application of these methods in specific, individual clinical situations.

Near-Infrared Imaging of Indocyanine Green Identifies Novel Routes of Lymphatic Drainage from Metacarpophalangeal Joints in Healthy Human Hands

Background: Collecting lymphatic vessel (CLV) dysfunction has been implicated in various diseases, including rheumatoid arthritis (RA). RA patients with active hand arthritis exhibit significantly reduced lymphatic clearance of the web spaces adjacent to the metacarpophalangeal (MCP) joints and a reduction in total and basilic-associated CLVs on the dorsal surface of the hand by near-infrared (NIR) imaging of indocyanine green (ICG). In this pilot study, we assessed direct lymphatic drainage from MCP joints and aimed to visualize the total lymphatic anatomy using novel dual-agent relaxation contrast magnetic resonance lymphography (DARC-MRL) in the upper extremity of healthy human subjects. Methods and Results: Two healthy male subjects >18 years old participated in the study. We performed NIR imaging along with conventional- or DARC-MRL following intradermal web space and intra-articular MCP joint injections. ICG (NIR) or gadolinium (Gd) (MRL) was administered to visualize the CLV anatomy of the upper extremity. Web space draining CLVs were associated with the cephalic side of the antecubital fossa, while MCP draining CLVs were localized to the basilic side of the forearm by near-infrared indocyanine green imaging. The DARC-MRL methods used in this study did not adequately nullify the contrast in the blood vessels, and limited Gd-filled CLVs were identified. Conclusion: MCP joints predominantly drain into basilic CLVs in the forearm, which may explain the reduction in basilic-associated CLVs in the hands of RA patients. Current DARC-MRL techniques show limited identification of healthy lymphatic structures, and further refinement in this technique is necessary. Clinical trial registration number: NCT04046146.

MR Angiography of Pulmonary Vasculature

Pulmonary MR angiography (MRA) is a useful alternative to computed tomographic angiography (CTA) for the study of the pulmonary vasculature. For pulmonary hypertension and partial anomalous pulmonary venous return, a cardiac MR imaging and the pulmonary MRA are useful for flow quantification and planning treatment. For the diagnosis of pulmonary embolism (PE), MRA-PE has been shown to have non-inferior outcomes at 6 months when compared with CTA-PE. Over the last 15 years, pulmonary MRA has become a routine and reliable examination for the workup of pulmonary hypertension and the primary diagnosis of PE at the University of Wisconsin.

MRI of Lymphedema

Lymphedema is a devastating disease that has no cure. Management of lymphedema has evolved rapidly over the past two decades with the advent of surgeries that can ameliorate symptoms. MRI has played an increasingly important role in the diagnosis and evaluation of lymphedema, as it provides high spatial resolution of the distribution and severity of soft tissue edema, characterizes diseased lymphatic channels, and assesses secondary effects such as fat hypertrophy. Many different MR techniques have been developed for the evaluation of lymphedema, and the modality can be tailored to suit the needs of a lymphatic clinic. In this review article we provide an overview of lymphedema, current management options, and the current role of MRI in lymphedema diagnosis and management. EVIDENCE LEVEL: 5 TECHNICAL EFFICACY: Stage 5.

State-of-the-art imaging for lymphatic evaluation in children

The lymphatic system has been poorly understood and its importance neglected for decades. Growing understanding of lymphatic flow pathophysiology through peripheral and central lymphatic flow imaging has improved diagnosis and treatment options in children with lymphatic diseases. Flow dynamics can now be visualized by different means including dynamic contrast-enhanced magnetic resonance lymphangiography (DCMRL), the current standard technique to depict central lymphatics. Novel imaging modalities including intranodal, intrahepatic and intramesenteric DCMRL are quickly evolving and have shown important advances in the understanding and guidance of interventional procedures in children with intestinal lymphatic leaks. Lymphatic imaging is gaining importance in the radiologic and clinical fields and new techniques are emerging to overcome its limitations.

Visual analysis of global research output of lymphedema based on bibliometrics

Background

Globally, several generations of doctors in the field of lymphedema have created numerous publications. To date, no bibliometric analysis has been performed specifically on these publications. For the further promotion of research on lymphedema and to align with the international research frontiers, it is essential to understand the current state of Lymphedema research output.

Objective

This study aims to statistically and visually analyze the characteristics of publications output, distribution of contributions and development process of lymphedema, enriching the knowledge base of Lymphedema, and then seek potential research topics and collaborators.

Methods

Based on the Web of Science core collection database, we firstly analyzed the quantity and quality of publications in the field of lymphedema, secondly profiled the publishing groups in terms of country, institution, author's publication and cooperation network, and finally sorted out and summarized the hot topics of research.

Results

A total of 8569 papers were retrieved from 1900-2021. The top4 journals with the most publications were LYMPHOLOGY, LYMPHATIC RESEARCH AND BIOLOGY, PLASTIC AND RECONSTRUCTIVE SURGERY and ANNALS OF SURGICAL ONCOLOGY. The top 4 countries with the most publications were USA, Japan, UK, and China. The United States dominates the total number of publications and the international cooperation network. The most productive research institution is Harvard University, and the research institution with the most collaborating institutions is Memorial Sloan Kettering Cancer Center. Mortimer, Peter S contributes the most research in this field. The research achievements of Japanese scholars in this field are of great significance. The top 5 ranked keywords are "Breast Cancer", "Health-Related Quality Of Life", "Lymphscintigraphy", "Lymphovenous Anastomosis", and "Lymphangiogenesis".

Conclusion

More and more scholars are devoted to the research of cancer-related Lymphedema. It is foreseeable that breast cancer-related lymphedema and lymphangiogenesis will remain a focus of future research. Advances in Lymphatic vessel imaging and the development of lymphatic microsurgery will further play a role in the clinical workup of lymphedema. Meanwhile, This study can help researchers identify potential collaborators and partner institutions and contribute to further research.

Understanding Lymphatic Anatomy and Abnormalities at Imaging

Lymphatic abnormalities encompass a wide range of disorders spanning solitary common cystic lymphatic malformations (LMs) to entities involving multiple organ systems such as lymphangioleiomyomatosis. Many of these disorders are rare, yet some, such as secondary lymphedema from the treatment of malignancy (radiation therapy and/or lymph node dissection), affect millions of patients worldwide. Owing to complex and variable anatomy, the lymphatics are not as well understood as other organ systems. Further complicating this is the variability in the description of lymphatic disease processes and their nomenclature in the medical literature. In recent years, medical imaging has begun to facilitate a deeper understanding of the physiology and pathologic processes that involve the lymphatic system. Radiology is playing an important and growing role in the diagnosis and treatment of many lymphatic conditions. The authors describe both normal and common variant lymphatic anatomy. Various imaging modalities including nuclear medicine lymphoscintigraphy, conventional lymphangiography, and MR lymphangiography used in the diagnosis and treatment of lymphatic disorders are highlighted. The authors discuss imaging many of the common and uncommon lymphatic disorders, including primary LMs described by the International Society for the Study of Vascular Anomalies 2018 classification system (microcystic, mixed, and macrocystic LMs; primary lymphedema). Secondary central lymphatic disorders are also detailed, including secondary lymphedema and chylous leaks, as well as lymphatic disorders not otherwise easily classified. The authors aim to provide the reader with an overview of the anatomy, pathology, imaging findings, and treatment of a wide variety of lymphatic conditions. ^©RSNA, 2022.

Dynamic contrast-enhanced MR lymphangiography: feasibility of using ferumoxytol in patients with chronic kidney disease

PURPOSE

To assess the feasibility of direct intra-lymphatic administration of diluted ferumoxytol as a T1-positive contrast agent for dynamic contrast-enhanced MR lymphangiography (DCMRL) imaging of the central lymphatics in children with renal disease.

METHODS

In vitro scan of dilute ferumoxytol was initially performed using time-resolved and high-resolution 3D gradient echo (GRE) sequences with short TE values (1 to 1.5 ms). A ferumoxytol concentration of 0.25 to 0.40 mg/mL was found to retain high signal in the T1-weighted sequences. DCMRL was then performed in 4 children with renal disease with the same 3D GRE sequences administrating diluted ferumoxytol via intra-mesenteric (IM), intra-hepatic (IH), and intra-nodal (IN) routes (6 to 9 mL to each site; average total dose of 0.75 mg/kg) by slow hand injection (0.5 to 1.0 mL/min). The signal-to-noise ratio (SNR) of the lymphatics was measured for quantitative evaluation.

RESULTS

Ferumoxytol-enhanced DCMRL was technically successful in all patients. Contrast conspicuity within the lymphatics was sufficient without subtraction. The mean SNR was significantly higher than the muscle (50.1 ± 12.2 vs 13.2 ± 2.8; t = 15.9; p < .001). There were no short-term complications attributed to the administration of ferumoxytol in any of the four patients.

CONCLUSION

Magnetic resonance lymphangiography using ferumoxytol via IN, IH, and IM access is a new method to directly visualize the central lymphatic system and can be applied safely in patients with renal failure based on our preliminary report of four cases. Ferumoxytol-enhanced DCMRL shows diagnostic image quality by using 3D GRE sequences with short TE values and appropriate dilution of ferumoxytol.

KEY POINTS

• MR lymphangiography using ferumoxytol via intra-nodal, intra-hepatic, and intra-mesenteric access is a new method to directly visualize the central lymphatic system from the groin to the venous angle. • FDCMRL can be applied safely in patients with renal failure based on our preliminary report of four cases. • FDCMRL shows diagnostic image quality by using 3D GRE sequences with short TE values and appropriate dilution of the ferumoxytol.

Ferumoxytol-enhanced vascular suppression in magnetic resonance neurography

OBJECTIVE

To evaluate ferumoxytol-enhanced vascular suppression for visualizing branch nerves of the brachial plexus in magnetic resonance (MR) neurography.

MATERIALS AND METHODS

Signal simulations were performed to determine ferumoxytol's effect on nerve-, fat-, and blood-to-muscle contrast and to optimize pulse sequence parameters. Prospective, in vivo assessment included 10 subjects with chronic anemia who underwent a total of 19 (9 bilateral) pre- and post-infusion brachial plexus exams using three-dimensional (3D), T₂-weighted short-tau inversion recovery (T₂-STIR) sequences at 3.0 T. Two musculoskeletal radiologists qualitatively rated sequences for the degree of vascular suppression and brachial plexus branch nerve conspicuity. Nerve-to-muscle, -fat, and -vessel contrast ratios were measured.

RESULTS

Quantitative nerve/muscle and nerve/small vessel contrast ratios (CRs) increased with ferumoxytol (p < 0.05). Qualitative vascular suppression and suprascapular nerve visualization improved following ferumoxytol administration for both raters (p < .05). Pre- and post-ferumoxytol exams demonstrated moderate to near-perfect inter-rater agreement for nerve visualization and diagnostic confidence for the suprascapular and axillary nerves but poor to no agreement for the long thoracic nerve.

CONCLUSION

Ferumoxytol in T₂-weighted brachial plexus MR neurography provides robust vascular suppression and aids visualization of the suprascapular nerve in volunteers without neuropathy.

Lymphatic regeneration after implantation of aligned nanofibrillar collagen scaffolds: Preliminary preclinical and clinical results

BACKGROUND

We tested our hypothesis that implantation of aligned nanofibrillar collagen scaffolds (BioBridge™) can both prevent and reduce established lymphedema in the rat lymphedema model. Our authors report clinical cases that demonstrate new lymphatic formation guided by BioBridge™ as seen by near-infrared (NIR) fluoroscopy and magnetic resonance (MR) lymphography.

METHODS

A rat lymphedema model was utilized. A prevention group received implantation of BioBridge™ immediately after lymphadenectomy. A lymphedema group received implantation of BioBridge™ with autologous adipose-derived stem cells (ADSC; treatment group) or remained untreated (control group). All subjects were observed for 4 months after lymphadenectomy. The hindlimb change was evaluated using computed tomography-based volumetric analysis. Lymphagiogenesis was assessed by indocyanine green (ICG) lymphography.

RESULTS

Animals in the treatment group showed a reduction in affected limb volume. Animals in the prevention group showed no increase in the affected limb volume. ICG fluoroscopy demonstrated lymph flow and formation of lymphatics toward healthy lymphatics.

CONCLUSIONS

In the rat lymphedema model, implantation of BioBridge™ at the time of lymph node removal prevents the development of lymphedema. Treatment of established lymphedema with the BioBridge™ and ADSC reduces lymphedema. New lymphatic vessels are demonstrated by NIR fluoroscopy and MR lymphography. These findings have implications for the treatment of lymphedema in human subjects.

Magnetic resonance lymphangiography: with or without contrast?

Lymphedema is an important medical issue around the world, caused by an anomalous collection of fluid in soft tissue due to congenital malformations or stenosis or obstruction of lymphatic vessels. Magnetic resonance lymphangiography (MRL) is an emerging technique focused on noninvasive or minimally invasive imaging of lymphatics with the goal to diagnose and treat lymphedema. This review will briefly discuss lymphatic imaging starting with lymphography and radionuclide lymphoscintigraphy up to the newest methods, focusing on MRL, a rising technique, and highlighting the technical aspects fundamental for achieving high-resolution MRL.

[Multidisciplinary approach in the lymphedema patient: From rehabilitation to microsurgery]

Lymphedema is a chronic disease with a high incidence in our society. In this paper, we present a review with the latest advances in imaging techniques and surgical reconstructive treatment of lymphedema (lymphovenous anastomosis, vascularized lymph node transfer, and prophylactic lymphedema surgery). In addition, a protocol is established based on a multidisciplinary team (composed of physiatrists, plastic surgeons, radiologists and nuclear medicine radiologists) to optimize the treatment of these patients.

Systematic Review of Magnetic Resonance Lymphangiography From a Technical Perspective

BACKGROUND

Clinical examination and lymphoscintigraphy are the current standard for investigating lymphatic function. Magnetic resonance imaging (MRI) facilitates three-dimensional (3D), nonionizing imaging of the lymphatic vasculature, including functional assessments of lymphatic flow, and may improve diagnosis and treatment planning in disease states such as lymphedema.

PURPOSE

To summarize the role of MRI as a noninvasive technique to assess lymphatic drainage and highlight areas in need of further study.

STUDY TYPE

Systematic review.

POPULATION

In October 2019, a systematic literature search (PubMed) was performed to identify articles on magnetic resonance lymphangiography (MRL).

FIELD STRENGTH/SEQUENCE

No field strength or sequence restrictions.

ASSESSMENT

Article quality assessment was conducted using a bespoke protocol, designed with heavy reliance on the National Institutes of Health quality assessment tool for case series studies and Downs and Blacks quality checklist for health care intervention studies.

STATISTICAL TESTS

The results of the original research articles are summarized.

RESULTS

From 612 identified articles, 43 articles were included and their protocols and results summarized. Field strength was 1.5 or 3.0 T in all studies, with 25/43 (58%) employing 3.0 T imaging. Most commonly, imaging of the peripheries, upper and lower limbs including the pelvis (32/43, 74%), and the trunk (10/43, 23%) is performed, including two studies covering both regions. Imaging protocols were heterogenous; however, T2 -weighted and contrast-enhanced T1 -weighted images are routinely acquired and demonstrate the lymphatic vasculature. Edema, vessel, quantity and morphology, and contrast uptake characteristics are commonly reported indicators of lymphatic dysfunction.

DATA CONCLUSION

MRL is uniquely placed to yield large field of view, qualitative and quantitative, 3D imaging of the lymphatic vasculature. Despite study heterogeneity, consensus is emerging regarding MRL protocol design. MRL has the potential to dramatically improve understanding of the lymphatics and detect disease, but further optimization, and research into the influence of study protocol differences, is required before this is fully realized.

LEVEL OF EVIDENCE

2 TECHNICAL EFFICACY: Stage 2.

Magnetic resonance lymphography as three-dimensional navigation for lymphaticovenular anastomosis in patients with leg lymphedema

BACKGROUND

Precise mapping of functional lymphatic vessels is essential for successful lymphaticovenular anastomosis (LVA). This study aimed to clarify the precision of magnetic resonance lymphography (MRL) in detecting lymphatic vessels prior to LVA.

METHODS

Eighteen patients with leg lymphedema were recruited for this prospective study. All patients underwent MRL before LVA to obtain three-dimensional coordinates of lymphatic vessels from MRL images. The precision of MRL for detecting lymphatic vessels was evaluated and compared with those of other contrast techniques.

RESULTS

Twenty legs from 18 patients were analyzed. A total of 40 skin incisions were made, 32 of which were determined by MRL. The precision of MRL to detect lymphatic vessels was 94%. With the addition of MRL, the number of lymphatic vessels identified preoperatively was increased as compared with indocyanine green lymphography (ICG-L) alone. Assuming a detection sensitivity of MRL for lymphatic vessels of 1, those of other contrast techniques were 0.90 for ICG-L under microscopy, 0.73 for patent blue staining, and 0.43 for ICG-L before incision. Whereas ICG-L before incision could not detect lymphatic vessels at depths greater than 17.0 mm, all deeper anastomosed lymphatic vessels were identified by MRL.

CONCLUSION

Lymphatic vessels enhanced on MRL can be reliably identified intraoperatively. MRL is a promising preoperative examination in LVA that can selectively depict suitable lymphatic vessels even in deep tissue layers.

Current advances in lymphoedema management

Lymphoedema is the accumulation of protein-rich interstitial fluid within subcutaneous tissue and skin as a result of dysfunction of the lymphatic system. It is an underestimated, widely neglected and debilitating chronic condition. This article presents an overview of lymphoedema and recent advances in its management.

Patterns of lymphatic drainage after axillary node dissection impact arm lymphoedema severity: A review of animal and clinical imaging studies

Upper extremity lymphoedema after axillary node dissection is an iatrogenic disease particularly associated with treatment for breast or skin cancer. Anatomical studies and lymphangiography in healthy subjects identified that axillary node dissection removes a segment of the lymphatic drainage pathway running from the upper limb to the sub-clavicular vein, creating a surgical break. It is reasonable to infer that different patterns of lymphatic drainage may occur in the upper limb following surgery and contribute to the various presentations of lymphoedema from none to severe. Firstly, we reviewed animal imaging studies that investigated the repair of lymphatic drainage pathways from the limb after lymph node dissection. Secondly, we examined clinical imaging studies of lymphatic drainage pathways after axillary node dissection, including lymphangiography, lymphoscintigraphy and indocyanine green fluorescence lymphography. Finally, based on the gathered data, we devised a set of general principles for the restoration of lymphatic pathways after surgery. Lymphoscintigraphy shows that restoration of the original lymphatic pathway to the axilla after its initial disruption by nodal dissection was not uncommon and may prevent lymphoedema. We found that regenerated lymphatic vessels and dermal backflow (the reflux of lymph to the skin) contributed to either restoration of the original pathway or rerouting of the lymphatic pathway to other regional nodes. Variation in the lymphatic drainage pathway and the mechanisms of fluid drainage itself are the foundation of new lymphatic drainage patterns considered to be significant in determining the severity with which lymphoedema develops.

Initial Clinical Experience with Dual-Agent Relaxation Contrast for Isolated Lymphatic Channel Mapping

Purpose To evaluate the clinical performance of dual-agent relaxation contrast (DARC) magnetic resonance (MR) lymphangiography compared with that of conventional MR lymphangiography in the creation of isolated lymphatic maps in patients with secondary lymphedema. Materials and Methods This retrospective study was approved by the institutional review board. The diagnostic quality of 42 DARC MR lymphangiographic studies was compared with that of 42 conventional MR lymphangiographic studies. Two independent readers rated venous contamination as absent, mild, or moderate to severe. Interreader agreement on venous contamination grades was assessed by using the linearly weighted Cohen κ statistic. The Mann-Whitney U test was used to compare the distribution of grades at each station between conventional MR lymphangiography and DARC MR lymphangiography for each reader separately. Results DARC MR lymphangiography had significantly less venous contamination than did conventional MR lymphangiography (P < .001). The two radiologists rated venous contamination as moderate to severe in 64% (27 of 42) and 69% (29 of 42) of distal limbs, 23% (10 of 42) of midlimbs, and 2% (one of 42) and 9% (four of 42) of proximal limbs at conventional MR lymphangiography compared with 0% (0 of 42) of distal limbs, 2% (one of 42) of midlimbs, and 0% (0 of 42) of proximal limbs at DARC MR lymphangiography. Lymphatic signal was partially attenuated (median 45% decrease) when longer echo times were used for venous suppression, but it did not subjectively degrade diagnostic quality. Conclusion DARC MR lymphangiography yields isolated lymphatic maps through nulling of venous contamination, thereby simplifying diagnostic interpretation and communication with surgical colleagues. ^© RSNA, 2017.

Contrast-enhanced pulmonary MRA for the primary diagnosis of pulmonary embolism: current state of the art and future directions

CT pulmonary angiography (CTPA) is currently considered the imaging standard of care for the diagnosis of pulmonary embolism (PE). Recent advances in contrast-enhanced pulmonary MR angiography (MRA) techniques have led to increased use of this modality for the detection of PE in the proper clinical setting. This review is intended to provide an introduction to the state-of-the-art techniques used in pulmonary MRA for the detection of PE and to discuss possible future directions for this modality. This review discusses the following issues pertinent to MRA for the diagnosis of PE: (1) the diagnostic efficacy and clinical effectiveness for pulmonary MRA relative to CTPA, (2) the different pulmonary MRA techniques used for the detection of PE, (3) guidance for building a clinical service at their institution using MRA and (4) future directions of PE MRA. Our principal aim was to show how pulmonary MRA can be used as a safe, effective modality for the diagnosis of clinically significant PE, particularly for those patients where there are concerns about ionizing radiation or contraindications/allergies to the iodinated contrast material.

A comprehensive literatures update of clinical researches of superparamagnetic resonance iron oxide nanoparticles for magnetic resonance imaging

This paper aims to update the clinical researches using superparamagnetic iron oxide (SPIO) nanoparticles as magnetic resonance imaging (MRI) contrast agent published during the past five years. PubMed database was used for literature search, and the search terms were (SPIO OR superparamagnetic iron oxide OR Resovist OR Ferumoxytol OR Ferumoxtran-10) AND (MRI OR magnetic resonance imaging). The literature search results show clinical research on SPIO remains robust, particularly fuelled by the approval of ferumoxytol for intravenously administration. SPIOs have been tested on MR angiography, sentinel lymph node detection, lymph node metastasis evaluation; inflammation evaluation; blood volume measurement; as well as liver imaging. Two experimental SPIOs with unique potentials are also discussed in this review. A curcumin-conjugated SPIO can penetrate brain blood barrier (BBB) and bind to amyloid plaques in Alzheime's disease transgenic mice brain, and thereafter detectable by MRI. Another SPIO was fabricated with a core of Fe3O4 nanoparticle and a shell coating of concentrated hydrophilic polymer brushes and are almost not taken by peripheral macrophages as well as by mononuclear phagocytes and reticuloendothelial system (RES) due to the suppression of non-specific protein binding caused by their stealthy ''brush-afforded'' structure. This SPIO may offer potentials for the applications such as drug targeting and tissue or organ imaging other than liver and lymph nodes.

Crossover comparison of ferumoxytol and gadobenate dimeglumine for abdominal MR-angiography at 3.0 tesla: Effects of contrast bolus length and flip angle

PURPOSE

Ferumoxytol (FE) has gained interest as an alternative to gadolinium-based contrast agents (GBCAs). The purpose of this study was to evaluate and optimize ferumoxytol dose and T1 weighting, in comparison to a conventional GBCA.

MATERIALS AND METHODS

Twelve healthy volunteers (six women / six men, mean age 44.3 years) were recruited for this study. Scanning was performed on a clinical 3 Tesla (T) MRI system. Gadobenate dimeglumine (GD)-enhanced MRA was performed followed by FE-enhanced MRA 1 month later. Volunteers were randomly assigned to a diluted (n = 6) or undiluted (n = 6) dose of GD (0.1 mmol/kg), and to FE doses of 4 mg/kg (n = 6) or 2 mg/kg (n = 6). First pass and steady-state MRA were performed for GD- and FE-enhanced MRA. Flip-angle optimization was performed after FE administration. Quantitative analysis included relative contrast-to-noise ratio (relCNR) measurements for all acquisitions. First pass GD- and FE-enhanced MRA images were evaluated qualitatively.

RESULTS

RelCNR was significantly higher with undiluted GD (31.8, 95% confidence interval [CI], 27.7-35.9) compared with diluted GD (16.2; 95% CI, 12.2-20.3; P = 0.001) and both 4 mg/kg FE (12.5; 95% CI, 8.5-16.4; P < 0.001) and 2 mg/kg FE (9.1; 95% CI, 5.1-13.2; P < 0.001) during first pass. Relative CNR did not decrease with FE 5 min postinjection compared with GD. Flip-angle analysis revealed relative CNR-peaks at 30° for FE 4 mg/kg and at 20° for FE 2 mg/kg. Diluted GD (P = 0.013) and FE 4 mg/kg (P = 0.01) revealed significantly higher image quality scores compared with undiluted GD during first pass.

CONCLUSION

This study shows an equivalent image quality of FE and GD for first pass MRA even though GD showed significantly higher relative CNR.

LEVEL OF EVIDENCE

1 Technical Efficacy: Stage 2 J. MAGN. RESON. IMAGING 2017;45:1617-1626.

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