An immunohistochemical study of lymphatic elements in the human brain.

Almost 150 papers about brain lymphatics have been published in the last 150 years. Recently, the information in these papers has been synthesized into a picture of central nervous system (CNS) "glymphatics," but the fine structure of lymphatic elements in the human brain based on imaging specific markers of lymphatic endothelium has not been described. We used LYVE1 and PDPN antibodies to visualize lymphatic marker-positive cells (LMPCs) in postmortem human brain samples, meninges, cavernous sinus (cavum trigeminale), and cranial nerves and bolstered our findings with a VEGFR3 antibody. LMPCs were present in the perivascular space, the walls of small and large arteries and veins, the media of large vessels along smooth muscle cell membranes, and the vascular adventitia. Lymphatic marker staining was detected in the pia mater, in the arachnoid, in venous sinuses, and among the layers of the dura mater. There were many LMPCs in the perineurium and endoneurium of cranial nerves. Soluble waste may move from the brain parenchyma via perivascular and paravascular routes to the closest subarachnoid space and then travel along the dura mater and/or cranial nerves. Particulate waste products travel along the laminae of the dura mater toward the jugular fossa, lamina cribrosa, and perineurium of the cranial nerves to enter the cervical lymphatics. CD3-positive T cells appear to be in close proximity to LMPCs in perivascular/perineural spaces throughout the brain. Both immunostaining and qPCR confirmed the presence of adhesion molecules in the CNS known to be involved in T cell migration.

Intranodal dynamic contrast-enhanced CT lymphangiography and dynamic contrast-enhanced MR lymphangiography in microminipig.

OBJECTIVES: To evaluate the feasibility and image quality of intranodal dynamic contrast-enhanced CT lymphangiography (DCCTL) and dynamic contrast-enhanced MR lymphangiography (DCMRL) in microminipigs. METHODS: Our institution's committee for animal research and welfare provided approval. Three microminipigs underwent DCCTL and DCMRL after inguinal lymph node injection of 0.1 mL/kg contrast media. Mean CT values on DCCTL and signal intensity (SI) on DCMRL were measured at the venous angle and thoracic duct (TD). The contrast enhancement index (CEI; increase in CT values pre- to post-contrast) and signal intensity ratio (SIR; SI of lymph divided by SI of muscle) were evaluated. The morphologic legibility, visibility, and continuity of lymphatics were qualitatively evaluated using a 4-point scale. Two microminipigs underwent DCCTL and DCMRL after lymphatic disruption and the detectability of lymphatic leakage was evaluated. RESULTS: The CEI peaked at 5-10 min in all microminipigs. The SIR peaked at 2-4 min in two microminipigs and at 4-10 min in one microminipig. The peak CEI and SIR values were 235.6 HU and 4.8 for venous angle, 239.4 HU and 2.1 for upper TD, and 387.3 HU and 2.1 for middle TD. The visibility and continuity of upper-middle TD scores were 4.0 and 3.3-3.7 for DCCTL, and 4.0 and 4.0 for DCMRL. In the injured lymphatic model, both DCCTL and DCMRL demonstrated lymphatic leakage. CONCLUSIONS: DCCTL and DCMRL in a microminipig model enabled excellent visualization of central lymphatic ducts and lymphatic leakage, indicating the research and clinical potential of both modalities. KEY POINTS: • Intranodal dynamic contrast-enhanced computed tomography lymphangiography showed a contrast enhancement peak at 5-10 min in all microminipigs. • Intranodal dynamic contrast-enhanced magnetic resonance lymphangiography showed a contrast enhancement peak at 2-4 min in two microminipigs and at 4-10 min in one microminipig. • Both intranodal dynamic contrast-enhanced computed tomography lymphangiography and dynamic contrast-enhanced magnetic resonance lymphangiography demonstrated the central lymphatic ducts and lymphatic leakage.

Advances in photoacoustic imaging aided by nano contrast agents: special focus on role of lymphatic system imaging for cancer theranostics.

Photoacoustic imaging (PAI) is a successful clinical imaging platform for management of cancer and other health conditions that has seen significant progress in the past decade. However, clinical translation of PAI based methods are still under scrutiny as the imaging quality and clinical information derived from PA images are not on par with other imaging methods. Hence, to improve PAI, exogenous contrast agents, in the form of nanomaterials, are being used to achieve better image with less side effects, lower accumulation, and improved target specificity. Nanomedicine has become inevitable in cancer management, as it contributes at every stage from diagnosis to therapy, surgery, and even in the postoperative care and surveillance for recurrence. Nanocontrast agents for PAI have been developed and are being explored for early and improved cancer diagnosis. The systemic stability and target specificity of the nanomaterials to render its theranostic property depends on various influencing factors such as the administration route and physico-chemical responsiveness. The recent focus in PAI is on targeting the lymphatic system and nodes for cancer diagnosis, as they play a vital role in cancer progression and metastasis. This review aims to discuss the clinical advancements of PAI using nanoparticles as exogenous contrast agents for cancer theranostics with emphasis on PAI of lymphatic system for diagnosis, cancer progression, metastasis, PAI guided tumor resection, and finally PAI guided drug delivery.

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.

Recent advancement of imaging strategies of the lymphatic system: Answer to the decades old questions.

The role of the lymphatic system in maintaining tissue homeostasis and a number of different pathophysiological conditions has been well established. The complex and delicate structure of the lymphatics along with the limitations of conventional imaging techniques make lymphatic imaging particularly difficult. Thus, in-depth high-resolution imaging of lymphatic system is key to understanding the progression of lymphatic diseases and cancer metastases and would greatly benefit clinical decisions. In recent years, the advancement of imaging technologies and development of new tracers suitable for clinical applications has enabled imaging of the lymphatic system in both clinical and pre-clinical settings. In this current review, we have highlighted the advantages and disadvantages of different modern techniques such as near infra-red spectroscopy (NIRS), positron emission tomography (PET), computed tomography (CT), magnetic resonance imaging (MRI) and fluorescence optical imaging, that has significantly impacted research in this field and has led to in-depth insights into progression of pathological states. This review also highlights the use of current imaging technologies, and tracers specific for immune cell markers to identify and track the immune cells in the lymphatic system that would help understand disease progression and remission in immune therapy regimen.

Intranodal CT Lymphangiography with Water-soluble Iodinated Contrast Medium for Imaging of the Central Lymphatic System.

Background Dynamic contrast-enhanced MR lymphangiography (DCMRL) is the reference standard used to diagnose various thoracic lymphatic disorders, such as traumatic chylothorax and plastic bronchitis. However, accessibility and logistical challenges have prevented the wide dissemination of this technology. Purpose To evaluate the feasibility of intranodal CT lymphangiography (ICTL) in the diagnosis and planning of subsequent intervention in patients with thoracic lymphatic disorders. Materials and Methods In this retrospective review, five women suspected of having lymphatic abnormalities (ranging from traumatic chylothorax to plastic bronchitis) and with contraindications to MRI underwent ICTL from September 2019 to May 2020. Needles (25 gauge) were placed in the bilateral inguinal lymph nodes with US guidance, and water-soluble iodinated contrast material was injected. CT fluoroscopy was used to monitor the opacification of the cisterna chyli to determine the timing of CT. After ICTL, the thoracic duct was catheterized, and lymphangiography was performed through the thoracic duct catheter. The ICTL and subsequent lymphangiographic findings were then visually compared by using three-dimensional reconstructions. Results Intranodal injection of water-soluble contrast medium was successful in all patients evaluated (five women; mean age, 68 years ± 11 [standard deviation]; range, 53-83 years). The central lymphatics were opacified in four of the five women, demonstrating abnormal pulmonary lymphatic flow from the thoracic duct into the lung parenchyma. In one of the five women, thoracic duct injection showed successful ligation of the thoracic duct. The time elapsed from injection of contrast medium to visualization of the thoracic duct ranged from 2 to 27 minutes. ICTL and lymphangiographic findings matched well. Conclusion Intranodal CT lymphangiography sufficiently depicted central lymphatic anatomy in patients with lymphatic abnormalities, thereby demonstrating its use as a feasible alternative to more technically challenging methods, such as dynamic contrast-enhanced MR lymphangiography. © RSNA, 2021.

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.

Lymphatic Interventions in the Cancer Patient.

PURPOSE OF REVIEW: The incidence of lymphatic leakage (iatrogenic and non-iatrogenic) is growing in cancer population due to the increased complexity of the surgical procedures and improved overall survival in cancer patients. The purpose of this article is to review the contemporary approach in the field of percutaneous lymphatic embolization in cancer patients with lymphatic leaks. RECENT FINDINGS: Since the advent of intranodal lymphangiography in 2011 alongside with the MR and CT lymphangiography, the accuracy of diagnosis of the lymphatic diseases has significantly improved significantly. These advancements have triggered a revival of minimally invasive lymphatic interventions. Lymphatic embolization is expanding from the classic indication, thoracic duct embolization, to other lymphatic disorders (chylous ascites, lymphoceles, liver lymphorrhea, protein-losing enteropathy). The growth of lymphatic research and the standardization of the lymphatic interventions require a multidisciplinary and collaborative approach between physicians and researchers.

The bright future of nanotechnology in lymphatic system imaging and imaging-guided surgery.

Lymphatic system is identified the second vascular system after the blood circulation in mammalian species, however the research on lymphatic system has long been hampered by the lack of comprehensive imaging modality. Nanomaterials have shown the potential to enhance the quality of lymphatic imaging due to the unparalleled advantages such as the specific passive targeting and efficient co-delivery of cocktail to peripheral lymphatic system, ease molecular engineering for precise active targeting and prolonged retention in the lymphatic system of interest. Multimodal lymphatic imaging based on nanotechnology provides a complementary means to understand the kinetics of lymphoid tissues and quantify its function. In this review, we introduce the established approaches of lymphatic imaging used in clinic and summarize their strengths and weaknesses, and list the critical influence factors on lymphatic imaging. Meanwhile, the recent developments in the field of pre-clinical lymphatic imaging are discussed to shed new lights on the design of new imaging agents, the improvement of delivery methods and imaging-guided surgery strategies.

The Lymphatic System in the Fontan Patient-Pathophysiology, Imaging, and Interventions: What the Anesthesiologist Should Know.

The Fontan surgery was developed as a palliative intervention for congenital heart disease (CHD) patients with single-ventricle physiology who are not candidates for a biventricular repair. Improvements in the surgery and medical management of these patients have increased survival, yet this population remains at risk for complications and end-organ dysfunction due to Fontan failure. Lymphatic vessels maintain a fluid balance within the extracellular space, participate in fat reabsorption from the small intestine, and play an important role in the body's immune response. Altered Starling forces at the capillary level, capillary leak, and lymphatic obstruction contribute to lymphatic dysfunction in patients with Fontan physiology. These lymphatic complications include edema, pleural effusions, plastic bronchitis (PB), and protein-losing enteropathy (PLE). Over the past decade, there have been innovations in lymphatic imaging. These new imaging techniques include noncontrast magnetic resonance (MR) lymphangiography, intranodal lymphangiography (IL), dynamic contrast-enhanced magnetic resonance lymphangiography (DCMRL), and liver lymphangiography. These imaging techniques help in delineating anatomy and guiding the appropriate therapeutic approach. Lymphatic interventions then may be performed to decompress the lymphatic system or to identify and occlude abnormal lymphatic vessels and drainage pathways. The anesthesiologist should have an understanding of the effects of lymphatic disorders on the Fontan circulation and apply appropriate management techniques for the associated interventions. The Fontan surgery was developed as a palliative intervention for CHD patients with single-ventricle physiology who are not candidates for a biventricular repair. The surgery creates a series systemic and pulmonary circulation with the energy necessary to provide gradient-driven pulmonary blood flow generated by the ventricle.1 In the past decades, improvements in the surgery and medical management of these patients have increased survival, with 30-year survival rates close to 85%.2 Despite these improvements, this population remains at risk for complications and end-organ dysfunction due to Fontan failure, which is characterized by elevated systemic venous pressures and low cardiac output. These complications include arrhythmias, cardiac dysfunction, ascites, liver fibrosis/cirrhosis, renal dysfunction, pulmonary failure, and lymphatic complications such as edema, pleural effusions, PB, and PLE. Complications ultimately contribute to increased risk for hospitalization, death, and need for heart transplantation.3,4 For this reason, there has been increasing interest in the role of abnormal lymphatic circulation in the genesis of Fontan failure. The authors characterize the lymphatic pathophysiology associated with Fontan physiology and review the imaging and interventional strategies used to treat these patients.

Dynamic contrast-enhanced magnetic resonance lymphangiography.

Lymphatic flow disorders include a broad spectrum of abnormalities that can originate in the lymphatic or the venous system. The development of these disorders is multifactorial and is most commonly associated with congenital heart diseases and palliative surgeries that these patients undergo. Central lymphatic disorders might be secondary to traumatic leaks, lymphatic overproduction, conduction abnormalities or lymphedema, and they can progress to perfusion anomalies. Several imaging modalities have been used to visualize the lymphatic system. However, the imaging of central lymphatic flow has always been challenging. Dynamic contrast-enhanced magnetic resonance lymphangiography (DCMRL) allows for visualization of central lymphatic flow disorders and has been recently applied for the assessment of plastic bronchitis, protein-losing enteropathy, chylothorax and chylopericardium, among other lymphatic disorders. The hepatic and mesenteric accesses are innovative and promising techniques for better identification and understanding of these abnormalities. The main objectives of this review are to discuss the physiology and anatomy of the lymphatic system and review the current uses of DCMRL in the diagnosis and management of lymphatic flow disorders.

Lymphatic anomalies in congenital heart disease.

Congenital heart disease can lead to various lymphatic complications including traumatic leaks, lymphatic overproduction, conduction abnormalities or lymphedema. Advancements in the imaging of central lymphatics and guided interventions have improved outcomes in these children. Dynamic contrast-enhanced magnetic resonance (MR) lymphangiography allows for the assessment of abnormal lymphatic drainage. This technique is preferred for evaluating lymphatic conditions such as plastic bronchitis, chylothorax, chyloptysis, chylopericardium, protein-losing enteropathy and chylous ascites, among other lymphatic disorders. In this review, we discuss lymphatic abnormalities encountered on MRI in children with congenital heart disease. We also briefly review treatment options.

The lymphatic system throughout history: From hieroglyphic translations to state of the art radiological techniques.

A comprehensive lymphatic system is indispensable for a well-functioning body; it is integral to the immune system and is also interrelated with the digestive system and fluid homeostasis. The main difficulty in examining the lymphatic system is its fine-meshed structure. This remains a challenge, leaving patients with uninterpreted symptoms and a dearth of potential therapies. We review the history of the lymphatic system up to the present with the aim of improving current knowledge. Several findings described throughout history have made fundamental contributions to elucidating the lymphatic system. The first contributions were made by the ancient Egyptians and the ancient Greeks. Vesalius obtained new insights by dissecting corpses. Thereafter, Ruysch (1638-1731) gained an understanding of lymphatic flow. In 1784, Mascagni published his illustration of the whole lymphatic network. The introduction of radiological lymphography revolutionized knowledge of the lymphatic system. Pedal lymphangiography was first described by Monteiro (1931) and Kinmonth (1952). Lymphoscintigraphy (nuclear medicine), magnetic resonance imaging, and near-infrared fluorescence lymphography further improved visualization of the lymphatic system. The innovative dynamic contrast-enhanced magnetic resonance lymphangiography (DCMRL) transformed understanding of the central lymphatic system, enabling central lymphatic flow disorders in patients to be diagnosed and even allowing for therapeutic planning. From the perspective of the history of lymph visualization, DCMRL has ample potential for identifying specific causes of debilitating symptoms in patients with central lymphatic system abnormalities and even allows for therapeutic planning.

Photoacoustic-fluorescence microendoscopy in vivo.

A miniature endoscope capable of imaging multiple tissue contrasts in high resolution is highly attractive, because it can provide complementary and detailed tissue information of internal organs. Here we present a photoacoustic (PA)-fluorescence (FL) endoscope for optical-resolution PA microscopy (PAM) and FL microscopy (FLM). The endoscope with a diameter of 2.8 mm achieves high lateral resolutions of 5.5 and 6.3 µm for PAM and FLM modes, respectively. In vivo imaging of zebrafish larvae and a mouse ear is conducted, and high-quality images are obtained. Additionally, in vivo endoscopic imaging of a rat rectum is demonstrated, showing the endoscopic imaging capability of our endoscope. By providing dual contrasts with high resolution, the endoscope may open up new opportunities for clinical endoscopic imaging applications.

Magnetic Resonance Lymphangiography of the Central Lymphatic System: Technique and Clinical Applications.

Magnetic resonance lymphangiography (MRL) is a noninvasive imaging technique that can be used in the management of lymphatic disorders to delineate the central lymphatic system for treatment planning. This article reviews the MRL technique, its advantages, limitations, indications, and impact on patient management. Level of Evidence 5 Technical Efficacy Stage 3 J. MAGN. RESON. IMAGING 2021;53:374-380.

Research Priorities in Lymphatic Interventions: Recommendations from a Multidisciplinary Research Consensus Panel.

Recognizing the increasing importance of lymphatic interventions, the Society of Interventional Radiology Foundation brought together a multidisciplinary group of key opinion leaders in lymphatic medicine to define the priorities in lymphatic research. On February 21, 2020, SIRF convened a multidisciplinary Research Consensus Panel (RCP) of experts in the lymphatic field. During the meeting, the panel and audience discussed potential future research priorities. The panelists ranked the discussed research priorities based on clinical relevance, overall impact, and technical feasibility. The following research topics were prioritized by RCP: lymphatic decompression in patients with congestive heart failure, detoxification of thoracic duct lymph in acute illness, development of newer agents for lymphatic imaging, characterization of organ-based lymph composition, and development of lymphatic interventions to treat ascites in liver cirrhosis. The RCP priorities underscored that the lymphatic system plays an important role not only in the intrinsic lymphatic diseases but in conditions that traditionally are not considered to be lymphatic such as congestive heart failure, liver cirrhosis, and critical illness. The advancement of the research in these areas will lead the field of lymphatic interventions to the next level.

Association of Lymphatic Abnormalities with Early Complications after Fontan Operation.

BACKGROUND: Increased central venous pressure is inherent in Fontan circulation but not strongly related to Fontan complication. Abnormalities of the lymphatic circulation may play a crucial role in early Fontan complications. METHODS: This was a retrospective, single-center study of patients undergoing Fontan operation from 2008 to 2015. The primary outcome was significant early Fontan complication defined as secondary in-hospital treatment due to peripheral edema, ascites, pleural effusions, protein-losing enteropathy, or plastic bronchitis. All patients received T2-weighted magnetic resonance images to assess abdominal and thoracic lymphatic perfusion pattern 6 months after Fontan completion with respect to localization, distribution, and extension of lymphatic perfusion pattern (type 1-4) and with application of an area score (0-12 points). RESULTS: Nine out of 42 patients developed early Fontan complication. Patients with complication had longer chest tube drainage (mean 28 [interquartile range [IQR]: 13-60] vs. 13 [IQR: 2-22] days, p = 0.01) and more often obstructions in the Fontan circuit 6 months after surgery (56 vs. 15%, p = 0.02). Twelve patients showed little or no abnormalities of lymphatic perfusion (lymphatic perfusion pattern type 1). Most frequently magnetic resonance imaging showed lymphatic congestion in the supraclavicular region (24/42 patients). Paramesenteric lymphatic congestion was observed in eight patients. Patients with early Fontan complications presented with higher lymphatic area score (6 [min-max: 2-10] vs. 2 [min-max: 0-8]), p = 0.001) and greater distribution and extension of thoracic lymphatic congestion (type 3-4: n = 5/9 vs. n = 1/33, p = 0.001). CONCLUSION: Early Fontan complication is related to hemodynamic factors such as circuit obstruction and to the occurrence and extent of lymphatic congestion.

Solo Smart Fluorogenic Probe for Potential Cancer Diagnosis and Tracking in Vivo Tumorous Lymphatic Systems via Distinct Emission Signals.

A versatile twisted-intramolecular-charge-transfer (TICT)-based near-infrared (NIR) fluorescent probe (L) has been judiciously designed and synthesized that could be utilized for potential cancer diagnosis and to track lymph node(s) in mice through distinct emission signals. Essentially, the probe rendered the capability to preferentially recognize the cancer cells over the noncancer cells by polarity-guided lipid droplet specific differential bioimaging (in green emission channel) studies. The probe also exhibited selective turn-on fluorescence response toward HSA/BSA in physiological media (aqueous PBS buffer; pH 7.4) at far-red/NIR regions, because of the 1:1 chelation between the probe and HSA/BSA. Therefore, the fluorescent probe was then maneuvered to track the draining lymphatic system and sentinel lymph node in tumor mice model by fluorescence imaging (NIR/deep-red channel), wherein the accumulated albumin protein in the draining tumor lymphatic system facilitated the in situ formation of the fluorescent albumin-L complex.

Quantification of Thoracic Lymphatic Flow Patterns Using Dynamic Contrast-enhanced MR Lymphangiography.

Background Dynamic contrast material-enhanced MR lymphangiography has recently emerged as a technique to image the lymphatic anatomy and identify lymphatic flow abnormalities; however, a method to quantify lymphatic flow in health and disease is needed. Purpose To develop a method to quantify thoracic lymphatic flow patterns using dynamic contrast-enhanced MR lymphangiography. Materials and Methods The following patients with dynamic contrast-enhanced MR lymphangiography images collected in 2015 and 2016 were retrospectively identified: group A, neonates with chylothorax; group B, children with heart failure complicated by plastic bronchitis; and group C, adults with lymphatic plastic bronchitis and without heart failure. An automated image segmentation method was developed for segmenting the contrast-enhanced lymphatic flow in spatiotemporal domains from the dynamic contrast-enhanced MR lymphangiography images. The lymphatic flow rates were quantified for individual patients on the basis of their spatiotemporal dynamic contrast-enhanced MR lymphangiography segmentation results, and the flow rates were compared among the three patient groups by using Wilcoxon rank sum tests. Results Twenty-two patients were evaluated: seven neonates (mean age, 49 days ± 71 [standard deviation]; three boys, four girls), 10 children (mean age, 8 years ± 3; seven boys, three girls), and five adults (mean age, 46 years ± 10; three men, two women). The proposed method was used to obtain lymphatic flow segmentation results with Dice scores of 0.80, 0.82, and 0.83 for patients from groups A, B, and C, respectively. The mean flow rates for groups A, B, and C were 1.8 mL/min ± 1.4, 4.0 mL/min ± 1.8, and 12.5 mL/min ± 3.8, respectively. The flow rate differed significantly between groups A and B (P = .002), groups A and C (P = .01), and groups B and C (P = .01). Conclusion An automatic spatiotemporal segmentation method was used to determine thoracic lymphatic flow rates in individual patients based on their dynamic contrast-enhanced MR lymphangiographic images. © RSNA, 2020 Online supplemental material is available for this article.

Contrast-enhanced Interstitial Transpedal MR Lymphangiography for Thoracic Chylous Effusions.

Background Abnormalities of the central lymphatic system (CLS) are increasingly treated by interventional radiology approaches. Planning of these procedures, however, is challenging because of the lack of clinical imaging tools. Purpose To evaluate the clinical usefulness of contrast agent-enhanced interstitial transpedal MR lymphangiography in the preinterventional workup of lymphatic interventions in patients with thoracic chylous effusions. Materials and Methods Patients with chylous effusions evaluated from January 2014 and December 2017 were included in this retrospective analysis of transpedal MR lymphangiography. Indications were chylothorax (n = 19; 76%), cervical lymphatic fistula (n = 2; 8%), and combined chylothorax and chylous ascites (n = 4; 16%). Patients underwent transpedal MR lymphangiography at 1.5 T with T1-weighted imaging after interstitial pedal of gadolinium-based contrast medium under local anesthesia. Contrast-enhanced MRI was evaluated for technical success, depiction of pathologic abnormalities of the CLS, and access site for lymphatic interventions (ie, clinically useful examination). Reader agreement for image quality and overall degree of visualization was assessed with weighted κ. Interrelations between overall image quality and degree of visualization of CLS structures were assessed by Spearman ρ. Efficacy of transpedal MR lymphangiography was calculated by using radiographic lymphangiography as the reference standard. Results Twenty-five patients (mean age, 54 years ± 18 [standard deviation]; 13 men) were evaluated. Eight percent (two of 25) of examinations failed (lymphoma in one patient and technical failure in one patient). Contrast agent injection was well tolerated without complications. Interrater agreement of image quality was excellent (κ = 0.96). The degree of CLS visualization correlated with overall image quality (ρ = 0.71; P < .001). Retroperitoneal lymphatics, cisterna chyli, and thoracic duct were viewed with an accuracy of 23 of 25 (92%), 24 of 25 (96%), and 23 of 25 (92%), respectively. Anatomic variations, a lymphatic pathologic abnormality, and interventional access routes were identified with an accuracy of 22 of 25 (88%), 23 of 25 (92%), and 24 of 25 (96%), respectively. Overall, 23 of 25 (92%) transpedal MR lymphangiograms provided clinically useful information. Conclusion Transpedal interstitial MR lymphangiography was well tolerated by the patient and identified specific pathologic abnormalities causing thoracic chylous leakages before lymphatic intervention. © RSNA, 2020 Online supplemental material is available for this article. See also the editorial by Maki and Itkin in this issue.