b'evaluation is immersed in a bath and the displaceddoes not provide anatomic detail. Planar lympho-water volume is measured. This method is time- scintigraphy can be enhanced with single-photon consuming and requires access to water and a wateremission computed tomography (SPECT) imaging, tank with an outflow 22 . Another method involveswhich fuses the flow images with CT images. This adds bioimpedance spectroscopy (BIS), which has becomethree-dimensional anatomic detail, however has an increasingly popular method of detecting fluidlimited spatial resolution 30 . changes. BIS measures the rate of electrical currentNear-infrared Fluorescence Lymphography uses transmission through the limb as an indication ofindocyanine green (ICG), a non-radioactive dye used subdermal limb fluid levels. Validated mathematicalsafely for over 60 years, to provide real-time imaging models are used to calculate tissue and fluid measures.of lymphatic vessels and lymph nodes. Advantages of A faster transmission rate is measured through thethis method include high-resolution images, a safety lymphedematous limb, and it has been validated toprofile with a 1/10,000 allergy risk, low invasiveness, detect subclinical lymphedema 2426 . and suitability for intraoperative imaging. The above methods are not able to differentiateDisadvantages include limitation to superficial tissue between lymphedema versus lipedema. and difficulty in imaging individuals with high body However, ultrasound imaging can provide additionalmass index (BMI) 31 . Additionally, venography and details about the characteristics of the soft tissues,ultrasonography can be used to identify concomitant giving the provider information about not only whethervenous pathology in individuals with clinical evidence abnormal edema is present but also whether theof lymphedema 32 . abnormalities are more indicative of lymphedema orMagnetic Resonance Imaging (MRI): MRI has become lipedema. Ultrahigh frequency ultrasound has beenan important tool in the imaging armamentarium for able to demonstrate superficial lymphatic channels both lymphedema, lipedema, and as well, complex and the locations of adjacent venules, which has vascular and lymphatic anomalies. Non-contrast MR been proven particularly useful for some surgicaldemonstrates the anatomical findings of lymphedema, interventions for the treatment of lymphedema such with characteristic high signal in the subcutaneous as lymphovenous bypass or anastomosis.tissues/epifascial space on heavily T2 weighted sequences, corresponding to low signal intensity onUltrasound imaging demonstrating thicker T1 weighted sequences 33,34 . The central lymphatic skin and dermal hypo-echogenicity denotesvessels, including the thoracic duct, can also be lymphedema, whereas lipedema has beendemonstrated on heavily-T2 weighted sequences 34 .associated with increased thickness ofLymphangiography: Lymphangiography (or subcutaneous fat and hypo-echogenicitylymphography) uses known imaging techniques such subcutaneous fat 27 . as X-ray (fluoroscopy), CT or MRI, and specializeddyes that are able to visualize the lymphatic system IMAGING and detect abnormal anatomy and/or pathologyAuthor: Deborah Rabinowitz, MD such as lymphatic leaks. Various imaging methods may be used to betterInterstitial MR Lymphangiography (MRL) is characterize aberrant lymphatic vessels and provide aperformed with the injection of gadolinium (an MRI more personalized therapeutic approach. The imagingcontrast) into the interstitial tissue of the affected modalities discussed here are all available at LE&RNextremity. T1-weighted Images are then obtained at Comprehensive Centers of Excellence, Networks oftime intervals to demonstrate both the dynamic Excellence, and Referral Networks of Excellence, andlymphatic flow and high-resolution anatomic imaging.near-infrared fluorescence lymphography is available This demonstrates the function of the lymphatic at LD Surgery Centers of Excellence.system as well as dilated lymphatic vessels and dermal Radionuclide Lymphoscintigraphy was traditionally backflow35. Interstitial MRL is also used in pre-surgical the gold standard for diagnosis and confirmation ofplanning for both lymphovenous anastomosis and lymphedema28. A technetium-labeled radionuclide vascularized lymph node transfer surgeries 36,37 . is injected into the interdigital tissues of the affectedDynamic Contrast-enhanced MR Lymphangiography extremity, and images are obtained as the radiotracer(DCMRL) is increasingly utilized to visualize the central emits gamma rays. The tracer is visualized as it is lymphatic system 34 . Intranodal injection of gadolinium taken up by the lymphatic system, demonstrating theis performed with direct cannulation of groin lymph dynamic flow within the lymphatic system. Delayednodes and injection of gadolinium during time-tracer movement or dermal backflow confirms theresolved T1 weighted imaging 38 . Lymphatic flowdiagnosis of lymphedema with reports of 96%and anatomy are both visualized with high resolution, sensitivity and as high as 100% specificity 29however,allowing for a detailed examination of the central | Standardized Approach for the Diagnosis and Management of Lymphedema (LE) and Lymphatic Diseases (LD)|13'