Lymphedema evaluation using noninvasive 3T MR lymphangiography

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.

Lipedema Reduction Surgery Improves Pain, Mobility, Physical Function, and Quality of Life: Case Series Report

Background

Lipedema is a chronic inflammatory subcutaneous adipose-rich connective tissue disease affecting millions of women worldwide. Disproportionate fat accumulation on the extremities characterized by heaviness, tenderness, and swelling can affect function, mobility, and quality of life. Treatments include conservative measures and lipedema reduction surgery (LRS). Here, we report lipedema comorbidities and surgical techniques, outcomes measures, and complications after LRS.

Methods

This is a single outpatient clinic retrospective chart review case series of comorbidities and complications in 189 women with lipedema. Bioelectrical impedance analyses, knee kinematics, gait, physical examinations, Patient-Reported Outcomes Measurement Information System, and RAND Short Form-36 questionnaires collected before and after LRS were analyzed for 66 of the 189 women. Hemoglobin levels were measured by transdermal hemoglobin monitor (Masimo noninvasive hemoglobin monitoring; Irvine, Calif.).

Results

Common comorbidities in 189 women were hypermobile joints (50.5%), spider/varicose veins (48.6/24.5%), arthritis (29.1%), and hypothyroidism (25.9%). The most common complication in 5.5% of these women after LRS was lightheadedness with a 2-g reduction or more in hemoglobin. After conservative measures and LRS in 66 women, significant improvements (P ≤ 0.0009) were found for: (1) knee flexion (10 degrees); (2) gait; (3) Patient-Reported Outcomes Measurement Information System T-score (16%); (4) mobility questions: gait velocity, rising from a chair, stair ascent; (5) RAND Short Form-36 scores: physical functioning, energy/fatigue, emotional well-being, social function, general health; (6) and Bioelectrical impedance analyses total and segmental body fat mass.

Conclusion

LRS provided significant improvements to women with lipedema using direct physical measurements and validated outcome measures, comparable to those seen after total knee replacement.

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.

Choroid plexus perfusion and bulk cerebrospinal fluid flow across the adult lifespan

The choroid plexus (ChP) comprises a collection of modified ependymal cells that play an important role in the production of brain cerebrospinal fluid (CSF), and ChP perfusion aberrations have been implicated in a range of cerebrovascular and neurodegenerative disorders. To provide an exemplar for the growing interest in ChP activity, we evaluated ChP perfusion and bulk CSF flow cross-sectionally across the healthy adult lifespan. Participants (n = 77; age range = 21-86 years) were scanned at 3T using T1-weighted, T2-weighted-FLAIR, perfusion-weighted pCASL, and phase contrast MRI to calculate ChP anatomy, perfusion, and aqueductal CSF flow, respectively. Regression models were applied to evaluate aging effects on ChP volume and ChP perfusion in the lateral ventricles, as well as CSF flow. ChP volume (mean ± std = 2.81 ± 1.1 cm3) increased (p < 0.001), ChP perfusion (36.3 ± 8.6 mL/100 g/min) decreased (p = 0.0078), and ChP total blood flow (1.13 ± 0.34 mL/min) increased (p < 0.001) with age. Cranial-to-caudal net CSF flow (0.245 ± 0.20 mL/min) decreased, absolute CSF flow (4.86 ± 2.96 mL/min) increased, and CSF regurgitant fraction (0.87 ± 0.126) increased with age (all: p < 0.001). ChP perfusion was directly related to net cranial-to-caudal CSF flow through the aqueduct (p = 0.033). The implications of these findings are discussed in the context of the growing literature on CSF circulatory dysfunction in neurodegeneration and cerebrovascular disease.

Subcutaneous Adipose Tissue Edema in Lipedema Revealed by Noninvasive 3T MR Lymphangiography

BACKGROUND

Lipedema exhibits excessive lower-extremity subcutaneous adipose tissue (SAT) deposition, which is frequently misidentified as obesity until lymphedema presents. MR lymphangiography may have relevance to distinguish lipedema from obesity or lymphedema.

HYPOTHESIS

Hyperintensity profiles on 3T MR lymphangiography can identify distinct features consistent with SAT edema in participants with lipedema.

STUDY TYPE

Prospective cross-sectional study.

SUBJECTS

Participants (48 females, matched for age [mean = 44.8 years]) with lipedema (n = 14), lipedema with lymphedema (LWL, n = 12), cancer treatment-related lymphedema (lymphedema, n = 8), and controls without these conditions (n = 14).

FIELD STRENGTH/SEQUENCE

3T MR lymphangiography (nontracer 3D turbo-spin-echo).

ASSESSMENT

Review of lymphangiograms in lower extremities by three radiologists was performed independently. Spatial patterns of hyperintense signal within the SAT were scored for extravascular (focal, diffuse, or not apparent) and vascular (linear, dilated, or not apparent) image features.

STATISTICAL TESTS

Interreader reliability was computed using Fleiss Kappa. Fisher's exact test was used to evaluate the proportion of image features between study groups. Multinomial logistic regression was used to assess the relationship between image features and study groups. The odds ratio (OR) and 95% confidence interval (CI) of SAT extravascular and vascular features was reported in groups compared to lipedema. The threshold of statistical significance was P < 0.05.

RESULTS

Reliable agreement was demonstrated between three independent, blinded reviewers (P < 0.001). The frequency of SAT hyperintensities in participants with lipedema (36% focal, 36% diffuse), LWL (42% focal, 33% diffuse), lymphedema (62% focal, 38% diffuse), and controls (43% focal, 0% diffuse) was significantly distinct. Compared with lipedema, SAT hyperintensities were less frequent in controls (focal: OR = 0.63, CI = 0.11-3.41; diffuse: OR = 0.05, CI = 0.00-1.27), similar in LWL (focal: OR = 1.29, CI = 0.19-8.89; diffuse: OR = 1.05, CI = 0.15-7.61), and more frequent in lymphedema (focal: OR = 9.00, CI = 0.30-274.12; diffuse: OR = 5.73, CI = 0.18-186.84).

DATA CONCLUSION

Noninvasive MR lymphangiography identifies distinct signal patterns indicating SAT edema and lymphatic load in participants with lipedema.

EVIDENCE LEVEL

1 TECHNICAL EFFICACY: Stage 1.

Imaging of the Lymphatic Vessels for Surgical Planning: A Systematic Review

BACKGROUND

Secondary lymphedema is a common complication after surgical or radiotherapeutic cancer treatment. (Micro) surgical intervention such as lymphovenous bypass and vascularized lymph node transfer is a possible solution in patients who are refractory to conventional treatment. Adequate imaging is needed to identify functional lymphatic vessels and nearby veins for surgical planning.

METHODS

A systematic literature search of the Embase, MEDLINE ALL via Ovid, Web of Science Core Collection and Cochrane CENTRAL Register of Trials databases was conducted in February 2022. Studies reporting on lymphatic vessel detection in healthy subjects or secondary lymphedema of the limbs or head and neck were analyzed.

RESULTS

Overall, 129 lymphatic vessel imaging studies were included, and six imaging modalities were identified. The aim of the studies was diagnosis, severity staging, and/or surgical planning.

CONCLUSION

Due to its utility in surgical planning, near-infrared fluorescence lymphangiography (NIRF-L) has gained prominence in recent years relative to lymphoscintigraphy, the current gold standard for diagnosis and severity staging. Magnetic resonance lymphography (MRL) gives three-dimensional detailed information on the location of both lymphatic vessels and veins and the extent of fat hypertrophy; however, MRL is less practical for routine presurgical implementation due to its limited availability and high cost. High frequency ultrasound imaging can provide high resolution imaging of lymphatic vessels but is highly operator-dependent and accurate identification of lymphatic vessels is difficult. Finally, photoacoustic imaging (PAI) is a novel technique for visualization of functional lymphatic vessels and veins. More evidence is needed to evaluate the utility of PAI in surgical planning.

Interstitial Fluid Flows along Perivascular and Adventitial Clearances around Neurovascular Bundles

This study reports new phenomena of the interstitial fluid (ISF) microflow along perivascular and adventitial clearances (PAC) around neurovascular bundles. The fluorescent tracing was used to observe the ISF flow along the PAC of neurovascular bundles in 8-10 week old BALB/c mice. The new results include: (1) the topologic structure of the PAC around the neurovascular bundles is revealed; (2) the heart-orientated ISF flow along the PAC is observed; (3) the double-belt ISF flow along the venous adventitial clearance of the PAC is recorded; (4) the waterfall-like ISF flow induced by the small branching vessel or torn fascia along the PAC is discovered. Based on the above new phenomena, this paper approached the following objectives: (1) the kinematic laws of the ISF flow along the PAC around neurovascular bundles are set up; (2) the applicability of the hypothesis on the PAC and its subspaces by numerical simulations are examined. The findings of this paper not only enriched the image of the ISF flow through the body but also explained the kernel structure of the ISF flow (i.e., the PAC). It helps to lay the foundation for the kinematics and dynamics of the ISF flow along the PAC around neurovascular bundles.

Imaging biomarkers for diagnosis and treatment response in patients with lymphedema

Lymphedema is defined as a dysfunction of the lymphatic system producing an accumulation of lymphatic fluid in the surrounding tissue, as well as edema and fibrosis. A total of 250 million people worldwide are affected by this condition. Greater than 99% of these cases are related to a secondary cause. As there is a lack of curative therapy, the goal involves early diagnosis, in order to prevent the progression of the disease. Additionally, early diagnosis can aid in decreasing the demand for more complex surgical procedures. Currently, there is an impressive breadth of diagnostic tests available for these patients. We aimed to review the available literature in relation to the utilization of imaging biomarkers for the early diagnosis and treatment response in lymphedema.

Elevated magnetic resonance imaging measures of adipose tissue deposition in women with breast cancer treatment-related lymphedema

PURPOSE

Breast cancer treatment-related lymphedema (BCRL) is a common co-morbidity of breast cancer therapies, yet factors that contribute to BCRL progression remain incompletely characterized. We investigated whether magnetic resonance imaging (MRI) measures of subcutaneous adipose tissue were uniquely elevated in women with BCRL.

METHODS

MRI at 3.0 T of upper extremity and torso anatomy, fat and muscle tissue composition, and T₂ relaxometry were applied in left and right axillae of healthy control (n = 24) and symptomatic BCRL (n = 22) participants to test the primary hypothesis that fat-to-muscle volume fraction is elevated in symptomatic BCRL relative to healthy participants, and the secondary hypothesis that fat-to-muscle volume fraction is correlated with MR relaxometry of affected tissues and BCRL stage (significance criterion: two-sided p < 0.05).

RESULTS

Fat-to-muscle volume fraction in healthy participants was symmetric in the right and left sides (p = 0.51); in BCRL participants matched for age, sex, and BMI, fat-to-muscle volume fraction was elevated on the affected side (fraction = 0.732 ± 0.184) versus right and left side in controls (fraction = 0.545 ± 0.221, p < 0.001). Fat-to-muscle volume fraction directly correlated with muscle T₂ (p = 0.046) and increased with increasing level of BCRL stage (p = 0.041).

CONCLUSION

Adiposity quantified by MRI is elevated in the affected upper extremity of women with BCRL and may provide a surrogate marker of condition onset or severity.

CLINICAL TRIAL

NCT02611557.

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.

Non-contrast magnetic resonance lymphography (NCMRL) in cancer-related secondary lymphedema: acquisition technique and imaging findings

Cancer-related secondary lymphedema (LE) is a widespread issue, which markedly affects patients' quality of life. Its diagnosis is mainly clinical since there is no consensus on the best imaging technique that should be used to assess this pathology. Even if lymphedema treatment has been traditionally conservative and mainly based on compressive bandages and decongestive therapy, new surgical techniques are proving their effectiveness in the management of the disease and made proper assessment and characterization of lymphedema necessary. In this scenario, non-contrast magnetic resonance lymphography (NCMRL) is acquiring an increasing role, as a non-invasive imaging technique, useful for the analysis of LE. NCMRL is an effective tool in diagnosis confirmation, in providing information about the structural changes of the affected limbs, in grading this disorder, and provides a guide for LE management and treatment planning. This article aims to provide an overview of the literature regarding this examination, analyzing the acquisition technique, the interpretation of the imaging findings and their usefulness, the advantages and limits of this technique, to help the radiologist approach this relatively new investigation in cases of cancer-related LE.

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 imaging and bioimpedance evaluation of lymphatic abnormalities in patients with breast cancer treatment-related lymphedema

PURPOSE

Breast cancer treatment-related lymphedema (BCRL) evaluation is frequently performed using portable measures of limb volume and bioimpedance asymmetry. Here quantitative magnetic resonance imaging (MRI) is applied to evaluate deep and superficial tissue impairment, in both surgical and contralateral quadrants, to test the hypothesis that BCRL impairment is frequently bilateral and extends beyond regions commonly evaluated with portable external devices.

METHODS

3-T MRI was applied to investigate BCRL topographical impairment. Female BCRL (n = 33; age = 54.1 ± 11.2 years; stage = 1.5 ± 0.8) and healthy (n = 33; age = 49.4 ± 11.0 years) participants underwent quantitative upper limb MRI relaxometry (T2), bioimpedance asymmetry, arm volume asymmetry, and physical evaluation. Parametric tests were applied to evaluate study measurements (i) between BCRL and healthy participants, (ii) between surgical and contralateral limbs, and (iii) in relation to clinical indicators of disease severity. Two-sided p-value < 0.05 was required for significance.

RESULTS

Bioimpedance asymmetry was significantly correlated with MRI-measured water relaxation (T2) in superficial tissue. Deep muscle (T2 = 37.6 ± 3.5 ms) and superficial tissue (T2 = 49.8 ± 13.2 ms) relaxation times were symmetric in healthy participants. In the surgical limbs of BCRL participants, deep muscle (T2 = 40.5 ± 4.9 ms) and superficial tissue (T2 = 56.0 ± 14.8 ms) relaxation times were elevated compared to healthy participants, consistent with an edematous micro-environment. This elevation was also observed in contralateral limbs of BCRL participants (deep muscle T2 = 40.3 ± 5.7 ms; superficial T2 = 56.6 ± 13.8 ms).

CONCLUSIONS

Regional MRI measures substantiate a growing literature speculating that superficial and deep tissue, in surgical and contralateral quadrants, is affected in BCRL. The implications of these findings in the context of titrating treatment regimens and understanding malignancy recurrence are discussed.

Use of magnetic resonance imaging for evaluation of therapeutic response in breast cancer-related lymphedema: A systematic review

Breast cancer treatment-related lymphedema (BCRL) is a common comorbidity in breast cancer survivors. Although magnetic resonance imaging (MRI) is widely used to evaluate therapeutic response of patients with various medical conditions, it is not routinely used to evaluate lymphedema patients. We conducted a systematic review of the literature to identify studies on the use of MRI to evaluate therapy for BCRL. We hypothesized that MRI could provide information otherwise not possible through other examinations. On October 21, 2019, we conducted a systematic review on the PubMed/MEDLINE and Scopus databases, without time frame or language limitations, to identify studies on the use of MRI to evaluate therapy for BCRL. We excluded studies that investigated other applications of MRI, such as lymphedema diagnosis and surgical planning. Of 63 potential articles identified with the search, three case series fulfilled the eligibility criteria. In total, 53 patients with BCRL were included and quantitatively evaluated with MRI before and after manual lymphatic drainage. Authors used MRI or MR lymphagiography to investigate factors such as lymphatic vessel cross-sectional area, tissue water relaxation time (T₂), and chemical exchange saturation transfer. The only study that compared MRI measurement with standard examinations reported that MRI added information to the therapy evaluation. MRI seems to be a promising tool for quantitative measurement of therapeutic response in patients with BCRL. However, the identified studies focused on only manual lymphatic drainage and were limited by the small numbers of patients. More studies are necessary to shed light on the topic.

Magnetic Resonance Lymphangiography

Dynamic contrast-enhanced magnetic resonance lymphangiography is a novel technique to image central conducting lymphatics. It is performed by injecting contrast into groin lymph nodes and following passage of contrast through lymphatic system using T1-weighted MR images. Currently, it has been successfully applied to image and plan treatment of thoracic duct pathologies, lymphatic leaks, and other lymphatic abnormalities such as plastic bronchitis. It is useful in the assessment of chylothorax and chyloperitoneum. Its role in other areas such as intestinal lymphangiectasia and a variety of lymphatic anomalies is likely to increase.

A systematic review of magnetic resonance lymphography for the evaluation of peripheral lymphedema

OBJECTIVE

Visualization of the lymphatic system is necessary for both early diagnosis and associated treatments. A promising imaging modality is magnetic resonance lymphography (MRL). The aim of this review was to summarize different MRL protocols, to assess the clinical value in patients with peripheral lymphedema, and to define minimal requirements necessary for visualization of lymphatics.

METHODS

A systematic literature search was conducted in PubMed, Embase, and the Cochrane Library in December 2018. Studies performing MRL in patients with peripheral lymphedema or healthy participants were included. Study design, population, etiology, duration of lymphedema, clinical staging, contrast agent, dose, injection site, and technical magnetic resonance imaging details were analyzed. No meta-analyses were performed because of different study aims and heterogeneity of the study populations.

RESULTS

Twenty-five studies involving 1609 patients with both primary lymphedema (n = 669) and secondary lymphedema (n = 657) were included. Upper and lower limbs were examined in 296 and 602 patients, respectively. Twenty-two studies used a gadolinium-based contrast agent that was injected intracutaneously or subcutaneously in the interdigital web spaces. Contrast-enhanced T1-weighted combined with T2-weighted protocols were most frequently used. T1-weighted images showed lymphatics in 63.3% to 100%, even in vessels with a diameter of ≥0.5 mm. Dermal backflow and a honeycomb pattern were clearly recognized.

CONCLUSIONS

MRL identifies superficial lymphatic vessels with a diameter of ≥0.5 mm with high sensitivity and specificity and accurately shows abnormal lymphatics and lymphatic drainage patterns. Therefore, MRL could be of clinical value in both early and advanced stages of peripheral lymphedema. Minimum requirements of an MRL protocol should consist of a gadolinium-based contrast-enhanced T1-weighted gradient-recalled echo sequence combined with T2-weighted magnetic resonance imaging, with acquisition at least 30 minutes after injection of contrast material.

CEST MRI quantification procedures for breast cancer treatment-related lymphedema therapy evaluation

PURPOSE

To quantify chemical exchange saturation transfer contrast in upper extremities of participants with lymphedema before and after standardized lymphatic mobilization therapy using correction procedures for B₀ and B₁ heterogeneity, and T₁ relaxation.

METHODS

Females with (n = 12) and without (n = 17) breast cancer treatment-related lymphedema (BCRL) matched for age and body mass index were scanned at 3.0T MRI. B₁ efficiency and T₁ were calculated in series with chemical exchange saturation transfer in bilateral axilla (B₁ amplitude = 2µT, Δω = ±5.5 ppm, slices = 9, spatial resolution = 1.8 × 1.47 × 5.5 mm³ ). B₁ dispersion measurements (B₁ = 1-3 µT; increment = 0.5 µT) were performed in controls (n = 6 arms in 3 subjects). BCRL participants were scanned pre- and post-manual lymphatic drainage (MLD) therapy. Chemical exchange saturation transfer amide proton transfer (APT) and nuclear Overhauser effect (NOE) metrics corrected for B₁ efficiency were calculated, including proton transfer ratio (PTR'), magnetization transfer ratio asymmetry ( M T R asymmetry ' ) , and apparent exchange-dependent relaxation (AREX'). Nonparametric tests were used to evaluate relationships between metrics in BCRL participants pre- versus post-MLD (two-sided P < 0.05 required for significance).

RESULTS

B₁ dispersion experiments showed nonlinear dependence of Z-values on B₁ efficiency in the upper extremities; PTR' showed < 1% mean fractional difference between subject-specific and group-level correction procedures. PTR'_APT significantly correlated with T₁ (Spearman's rho = 0.57, P < 0.001) and body mass index (Spearman's rho = -0.37, P = 0.029) in controls and with lymphedema stage (Spearman's rho = 0.48, P = 0.017) in BCRL participants. Following MLD therapy, PTR'_APT significantly increased in the affected arm of BCRL participants (pre- vs. post-MLD: 0.41 ± 0.05 vs. 0.43 ± 0.03, P = 0.02), consistent with treatment effects from mobilized lymphatic fluid.

CONCLUSION

Chemical exchange saturation transfer metrics, following appropriate correction procedures, respond to lymphatic mobilization therapies and may have potential for evaluating treatments in participants with secondary lymphedema.

Update in diagnostic imaging of the thymus and anterior mediastinal masses

Anterior mediastinal masses include a wide spectrum of malignant and benign pathologies with a large percentage represented by thymic lesions. Distinguishing these masses on diagnostic imaging is fundamental to guide the proper management for each patient. This review illustrates possibilities and limits of different imaging modalities to diagnose a lesion of the anterior mediastinum with particular attention to thymic disease.

68Ga-NOTA-Evans Blue TOF PET/MR Lymphoscintigraphy Evaluation of the Severity of Lower Limb Lymphedema

PURPOSE

This study was designed to investigate the role of Ga-NOTA-Evans Blue (NEB) time-of-flight (TOF) PET/MR in evaluating lower limb lymphedema by visual analysis and novel parameters.

METHODS

Thirteen patients with unilateral lower limb lymphedema were divided into 3 groups according to the clinical severity: minimal (4 patients), moderate (5 patients), and severe (4 patients). All patients underwent Ga-NEB TOF PET/MR lymphoscintigraphy. The ratio of the standardized uptake value (SUV) of superficial lymphatic vessel (SLV) versus SUV of deep lymphatic vessel (DVL) (SUVslv/dlv) was designed to assess the level of lymphedema severity. The correlation between lymphedema severity and lymphoscintigraphy findings was determined using 1-way analysis of variance, the t test, and Pearson correlation analysis.

RESULTS

There was a significant difference in the SUVslv between the affected limbs and normal limbs in all subjects (affected limbs: 0.57 ± 0.32, normal limbs: 1.86 ± 1.43; P < 0.05), which was not found in the SUVdlv (affected limbs: 0.64 ± 0.39, normal limbs: 0.63 ± 0.31; P > 0.1). The SUVslv/dlv of the affected limbs showed statistical differences within the 3 groups (P < 0.05) (minimal group: 1.91 ± 0.45; moderate group: 0.84 ± 0.16; severe group: 0.42 ± 0.11). The statistical analysis revealed a negative correlation between SUVslv/dlv and the severity of lymphedema (r = -0.899; P < 0.01).

CONCLUSIONS

Ga-NEB TOF PET/MR lymphoscintigraphy can provide anatomical and functional information of lymphatic vessels to guide surgery plans. SUVslv/dlv was well correlated with clinical lymphedema severity and might be potential in evaluating bilateral lower limb lymphedema.

3.0 T relaxation time measurements of human lymph nodes in adults with and without lymphatic insufficiency: Implications for magnetic resonance lymphatic imaging

The purpose of this work was to quantify 3.0 T (i) T1 and T2 relaxation times of in vivo human lymph nodes (LNs) and (ii) LN relaxometry differences between healthy LNs and LNs from patients with lymphatic insufficiency secondary to breast cancer treatment-related lymphedema (BCRL). MR relaxometry was performed over bilateral axillary regions at 3.0 T in healthy female controls (105 LNs from 20 participants) and patients with BCRL (108 LNs from 20 participants). Quantitative T1 maps were calculated using a multi-flip-angle (20, 40, 60°) method with B1 correction (dual-TR method, TR1 /TR2  = 30/130 ms), and T2 maps using a multi-echo (TE  = 9-189 ms; 12 ms intervals) method. T1 and T2 were quantified in the LN cortex and hilum. A Mann-Whitney U-test was applied to compare LN relaxometry values between patients and controls (significance, two sided, p < 0.05). Linear regression was applied to evaluate how LN relaxometry varied with age, BMI, and clinical indicators of disease. LN substructure relaxation times (mean ± standard deviation) in healthy controls were T1 cortex, 1435 ± 391 ms; T1 hilum, 714 ± 123 ms; T2 cortex, 102 ± 12 ms, and T2 hilum, 119 ± 21 ms. T1 of the LN cortex was significantly reduced in the contralateral axilla of BCRL patients compared with the axilla on the surgical side (p < 0.001) and compared with bilateral control values (p < 0.01). The LN cortex T1 asymmetry discriminated cases from controls (p = 0.004) in a multiple linear regression, accounting for age and BMI. Human 3.0 T T1 and T2 relaxation times in axillary LNs were quantified for the first time in vivo. Measured values are relevant for optimizing acquisition parameters in anatomical lymphatic imaging sequences, and can serve as a reference for novel functional and molecular LN imaging methods that require quantitative knowledge of LN relaxation times.

Tissue Sodium Content is Elevated in the Skin and Subcutaneous Adipose Tissue in Women with Lipedema

OBJECTIVE

To test the hypothesis that tissue sodium and adipose content are elevated in patients with lipedema; if confirmed, this could establish precedence for tissue sodium and adipose content representing a discriminatory biomarker for lipedema.

METHODS

Participants with lipedema (n = 10) and control (n = 11) volunteers matched for biological sex, age, BMI, and calf circumference were scanned with 3.0-T sodium and conventional proton magnetic resonance imaging (MRI). Standardized tissue sodium content was quantified in the calf skin, subcutaneous adipose tissue (SAT), and muscle. Dixon MRI was employed to quantify tissue fat and water volumes of the calf. Nonparametric statistical tests were applied to compare regional sodium content and fat-to-water volume between groups (significance: two-sided P ≤ 0.05).

RESULTS

Skin (P = 0.01) and SAT (P = 0.04) sodium content were elevated in lipedema (skin: 14.9 ± 2.9 mmol/L; SAT: 11.9 ± 3.1 mmol/L) relative to control participants (skin: 11.9 ± 2.0 mmol/L; SAT: 9.4 ± 1.6 mmol/L). Relative fat-to-water volume in the calf was elevated in lipedema (1.2 ± 0.48 ratio) relative to control participants (0.63 ± 0.26 ratio; P < 0.001). Skin sodium content was directly correlated with fat-to-water volume (Spearman's rho = 0.54; P = 0.01).

CONCLUSIONS

Internal metrics of tissue sodium and adipose content are elevated in patients with lipedema, potentially providing objective imaging-based biomarkers for differentially diagnosing the under-recognized condition of lipedema from obesity.