Iron oxide-enhanced MR lymphography: initial experience

The Role of Imaging of Lymphatic System to Prevent Cancer Related Lymphedema

Lymphedema is a progressive chronic condition affecting approximately 250 million people worldwide, a number that is currently underestimated. In Western countries, the most common form of lymphedema of the extremities is cancer-related and less radical surgical intervention is the main option to prevent it. Standardized protocols in the areas of diagnosis, staging and treatment are strongly required to address this issue. The aim of this study is to review the main diagnostic methods, comparing new emerging procedures to lymphoscintigraphy, considered as the golden standard to date. The roles of Magnetic Resonance Lymphangiography (MRL) or indocyanine green ICG lymphography are particularly reviewed in order to evaluate diagnostic accuracy, potential associations with lymphoscintigraphy, and future directions guided by AI protocols. The use of imaging to treat lymphedema has benefited from new techniques in the area of lymphatic vessels anatomy; these perspectives have become of value in many clinical scenarios to prevent cancer-related lymphedema.

Manganese porphyrin/ICG nanoparticles as magnetic resonance/fluorescent dual-mode probes for imaging of sentinel lymph node metastasis

Diagnosis of sentinel lymph node (SLN) metastasis and its status are key parameters for predicting overall disease prognosis. In this work, Pluronic F127 stabilized ICG/tetra(4-carboxyphenyl)porphyrin-Mn(III) (TCPP(Mn)) nanoparticles (F127-ICG/Mn NPs) as fluorescent/magnetic resonance (FL/MR) dual-modality probes were prepared. The application of F127-ICG/Mn NPs in SLN imaging was mainly evaluated from two perspectives: the difference between the normal LN and the metastatic SLN and the difference between micrometastasis and macrometastasis. Normal and metastatic SLNs and micro- and macro-SLN metastasis were successfully distinguished through fluorescence and MR imaging with the help of F127-ICG/Mn NPs. In contrast, for the ICG group, the micro- and macro-SLN metastasis status could not be differentiated by fluorescence imaging. Besides, the lymph nodes can be stained green by the F127-ICG/Mn NPs and clearly visualized by the naked eye. In general, F127-ICG/Mn NPs demonstrated the potential of the preoperative diagnosis of SLN metastasis and its status, as well as intraoperative navigation by green-stained SLN and NIR FL imaging. This work provides a reference for developing multimodal nanoparticles for SLN metastasis diagnosis.

Pelvic lymph node dissection in high-risk prostate cancer

INTRODUCTION

The therapeutic role of pelvic lymph node dissection (PLND) in prostate cancer (PCa) is unknown due to absence of randomized trials.

OBJECTIVE

to present a critical review on the therapeutic benefits of PLND in high risk localized PCa patients.

MATERIALS AND METHODS

A search of the literature on PLND was performed using PubMed, Cochrane, and Medline database. Articles obtained regarding diagnostic imaging and sentinel lymph node dissection, PLND extension, impact of PLND on survival, PLND in node positive "only" disease and PLND surgical risks were critically reviewed.

RESULTS

High-risk PCa commonly develops metastases. In these patients, the possibility of presenting lymph node disease is high. Thus, extended PLND during radical prostatectomy may be recommended in selected patients with localized high-risk PCa for both accurate staging and therapeutic intent. Although recent advances in detecting patients with lymph node involvement (LNI) with novel imaging and sentinel node dissection, extended PLND continues to be the most accurate method to stage lymph node disease, which may be related to the number of nodes removed. However, extended PLND increases surgical time, with potential impact on perioperative complications, hospital length of stay, rehospitalization and healthcare costs. Controversy persists on its therapeutic benefit, particularly in patients with high node burden.

CONCLUSION

The impact of PLND on biochemical recurrence and PCa survival is unclear yet. Selection of patients may benefit from extended PLND but the challenge remains to identify them accurately. Only prospective randomized study would answer the precise role of PLND in high-risk pelvis confined PCa patients.

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.

Hybrid 99mTc-magnetite tracer for dual modality sentinel lymph node mapping

Accuracy of sentinel lymph node identification using radioactive tracers in non-superficial cancers can be limited by radiation shine through and low spatial resolution of detection systems such as intraoperative gamma probes. By utilising a dual radioactive/magnetic tracer, sensitive lymphoscintigraphy can be paired with high spatial resolution intraoperative magnetometer probes to improve the accuracy of sentinel node detection in cancers with complex multidirectional lymphatic drainage. Dextran-coated magnetite nanoparticles (33 nm mean hydrodynamic diameter) were labelled with ^99mTc and applied as a lymphotropic tracer in small and large animal models. The dual tracer could be radiolabelled with 98 ± 2% efficiency after 10 min of incubation at room temperature. Biodistribution studies of the tracer were conducted in normal rats (subdermal and intravenous tail delivery, n = 3) and swine (subdermal hind limb delivery, n = 5). In rats the dual tracer migrated through four tiers of lymph node, 20 min after subdermal injection. Results from intravenous biodistribution test for radiocolloids demonstrated no aggregation in vivo, however indicated the presence of some lower-molecular weight radioactive impurities (^99mTc-dextran). In swine, the dual tracer could be effectively used to map lymphatic drainage from hind hoof to popliteal and inguinal basins using intraoperative gamma and magnetometer probes. Of the eight primary nodes excised, eight were positively identified by gamma probe and seven by magnetometer probe. The high-purity dual tracer shows early promise for sentinel node identification in complex lymphatic environments by combining sensitive preoperative lymphoscintigraphy with a high-resolution intraoperative magnetometer probe.

Using Imaging to Predict Treatment Response in Genitourinary Malignancies

CONTEXT

Over the previous2 decades, there have been numerous advancements in the diagnostic evaluation, therapeutic management, and postoperative assessment of genitourinary malignancies.

OBJECTIVE

To present a review of current and novel imaging modalities and their utility in the assessment of therapeutic response in the systemic management of renal, testicular, and prostate cancers.

EVIDENCE ACQUISITION

A PubMed/Medline search of the current published literature inclusive of prospective and retrospective original research, systematic reviews, and meta-analyses was conducted evaluating imaging modalities for renal cell carcinoma, prostate cancer, and testicular cancer. All relevant literature was individually reviewed and summarized to provide a concise description of the currently available imaging modalities and their efficacy in assessing treatment response of the genitourinary malignancies targeted in this review.

EVIDENCE SYNTHESIS

Conventional imaging techniques play a pivotal role in predicting the treatment response of genitourinary malignancies and have, therefore, been incorporated into clinical guidelines. Advancements in imaging technology have led to increased utilization for prognostication of a genitourinary cancer's response to therapy.

CONCLUSIONS

A good understanding of current recommended imaging techniques to evaluate treatment response in genitourinary malignancies is of paramount importance for today's clinician, who faces increasing treatment modalities.

PATIENT SUMMARY

In this review, we summarize available imaging modalities in the evaluation of treatment response in kidney, prostate, or testicular tumors. We believe that a good understanding of current imaging modalities is of paramount importance for healthcare providers treating these cancers.

Genotoxic evaluation of different sizes of iron oxide nanoparticles and ionic form by SMART, Allium and comet assay

In this study, the genotoxic potential of <50 nm, <100 nm iron oxide (Fe2O3) nanoparticles (IONPs) and ionic form were investigated using the wing somatic mutation and recombination test (SMART) and Allium and comet assays. In the SMART assay, different concentrations (1, 2, 5 and 10 mM) of NPs and ionic forms were fed to transheterozygous larvae of Drosophila melanogaster. No significant genotoxic effect was observed in <100 nm NPs and ionic form, while <50 nm IONPs showed genotoxicity at 1 and 10 mM concentrations. Allium cepa root meristems were exposed to five concentrations (0.001, 0.01, 0.1, 1 and 10 mM) of <50 nm and ionic forms for 4 h and three concentrations (2.5, 5 and 10 mM) for <100 nm of IONPs for 24 and 96 h. There was a statistically significant effect at 96 h at all concentrations of <100 nm IONPs. Similarly, <50 nm of IONPs and ionic forms also showed a statistically significant effect on mitotic index frequencies for all concentrations at 4 h. There was a dose-dependent increase in chromosomal abnormalities for IONPs and ionic form. Comet assay results showed time- and concentration-dependent increases in <100 nm NPs. There was a concentration-dependent increase in <50 nm NPs and ionic form ( p < 0.05). Consequently, the <50 nm of Fe2O3 was found toxic compared to 100 nm Fe2O3 and ionic form.

Increased transverse relaxivity in ultrasmall superparamagnetic iron oxide nanoparticles used as MRI contrast agent for biomedical imaging

Synthesis of a contrast agent for biomedical imaging is of great interest where magnetic nanoparticles are concerned, because of the strong influence of particle size on transverse relaxivity. In the present study, biocompatible magnetic iron oxide nanoparticles were synthesized by co-precipitation of Fe²⁺ and Fe³⁺ salts, followed by surface adsorption with reduced dextran. The synthesized nanoparticles were spherical in shape, and 12 ± 2 nm in size as measured using transmission electron microscopy; this was corroborated with results from X-ray diffraction and dynamic light scattering studies. The nanoparticles exhibited superparamagnetic behavior, superior T₂ relaxation rate and high relaxivities (r₁  = 18.4 ± 0.3, r₂  = 90.5 ± 0.8 s^-1 mM^-1 , at 7 T). MR image analysis of animals before and after magnetic nanoparticle administration revealed that the signal intensity of tumor imaging, specific organ imaging and whole body imaging can be clearly distinguished, due to the strong relaxation properties of these nanoparticles. Very low concentrations (3.0 mg Fe/kg body weight) of iron oxides are sufficient for early detection of tumors, and also have a clear distinction in pre- and post-enhancement of contrast in organs and body imaging. Many investigators have demonstrated high relaxivities of magnetic nanoparticles at superparamagnetic iron oxide level above 50 nm, but this investigation presents a satisfactory, ultrasmall, superparamagnetic and high transverse relaxivity negative contrast agent for diagnosis in pre-clinical studies. Copyright © 2016 John Wiley & Sons, Ltd.

Superparamagnetic iron oxide nanoparticles for in vivo molecular and cellular imaging

In the last decade, the biomedical applications of nanoparticles (NPs) (e.g. cell tracking, biosensing, magnetic resonance imaging (MRI), targeted drug delivery, and tissue engineering) have been increasingly developed. Among the various NP types, superparamagnetic iron oxide NPs (SPIONs) have attracted considerable attention for early detection of diseases due to their specific physicochemical properties and their molecular imaging capabilities. A comprehensive review is presented on the recent advances in the development of in vitro and in vivo SPION applications for molecular imaging, along with opportunities and challenges.

Lymphatic imaging: focus on imaging probes

In view of the importance of sentinel lymph nodes (SLNs) in tumor staging and patient management, sensitive and accurate imaging of SLNs has been intensively explored. Along with the advance of the imaging technology, various contrast agents have been developed for lymphatic imaging. In this review, the lymph node imaging agents were summarized into three groups: tumor targeting agents, lymphatic targeting agents and lymphatic mapping agents. Tumor targeting agents are used to detect metastatic tumor tissue within LNs, lymphatic targeting agents aim to visualize lymphatic vessels and lymphangionesis, while lymphatic mapping agents are mainly for SLN detection during surgery after local administration. Coupled with various signal emitters, these imaging agents work with single or multiple imaging modalities to provide a valuable way to evaluate the location and metastatic status of SLNs.

Lymphotropic nanoparticle-enhanced MRI in prostate cancer: value and therapeutic potential

Nodal staging in prostate cancer is suboptimal both with respect to current imaging modalities and pelvic lymph node dissection, and thus other techniques are being explored. Lymphotropic nanoparticle-enhanced MRI, also called magnetic resonance lymphography (MRL), is a technique that has shown high sensitivity (65-92 %) and excellent specificity (93-98 %) in detecting prostate cancer lymph node metastases. This technique aids in the detection of metastases in non-enlarged small nodes. MRL has been useful in determining the location and pathways of spread in nodal chains. Knowledge of the location of lymph node involvement is important for decisions regarding appropriate therapeutic options, such as image-guided therapy.. A geographic miss in radiotherapy can be avoided with the use of MRL-guided focal therapy. This paper provides an overview of current literature, lessons learned, and new therapeutic options with nanoparticle-enhanced MRI.

Magnetic resonance imaging diagnosis of metastatic lymph nodes in a rabbit model: efficacy of PJY10, a new ultrasmall superparamagnetic iron oxide agent, with monodisperse iron oxide core and multiple-interaction ligands

Background

Accurate diagnosis of lymph node metastasis is crucial in treatment planning for cancer patients. Despite the use of various parameters, making correct diagnosis of a small metastatic or a hyperplastic benign node is still a challenge. In this study, we evaluated the feasibility of detecting lymph node metastasis using a new ultrasmall superparamagnetic iron oxide particle, PJY10, in a rabbit model.

Methods

To make metastatic and benign lymph nodes, either VX2 carcinoma or fecal material suspension was inoculated into thighs of 56 rabbits three weeks or three days before magnetic resonance (MR) imaging, respectively. T2*-weighted 3T MR imaging was performed before and 24 hours after PJY10 injection (5.2 [n = 15], 7.8 [n = 17], and 10.4 [n = 24] mg Fe/kg). MR images were correlated with pathologic results to calculate sensitivity and specificity. Quantitative analysis of the signal intensity (SI) – number of voxels_[low] (the fraction of the number of voxels with the normalized SI on the postcontrast image lower than that on the precontrast image) and mean SI ratio – was also performed for each lymph node.

Results

Sensitivities were 100% at all three dosages, whereas specificity increased with increasing dosage (89% at 10.4 mg Fe/kg). The benign nodes had a significantly higher number of voxels_[low] and a lower mean SI ratio than the metastatic nodes at the dosage of 10.4 mg Fe/kg (P<.001). Az values were 0.905 for the number of voxels_[low] and 0.952 for the mean SI ratio. The number of voxels_[low] (P = .019) and the mean SI ratio (P = .034) had significant correlations with the histopathologic area ratio of metastatic foci in the metastatic nodes at 10.4 mg Fe/kg.

Conclusions

PJY10 enabled clear demonstration of lymph node metastasis with high sensitivity and specificity at its optimal dosage of 10.4 mg Fe/kg.

Multimodal detection of iron oxide nanoparticles in rat lymph nodes using magnetomotive ultrasound imaging and magnetic resonance imaging

Detection and removal of sentinel lymph nodes (SLN) is important in the diagnosis and treatment of cancer. The SLN is the first regional lymph node draining the primary tumor, and if the cancer has spread, it is most likely to find metastases in the SLN. In this study, we have for the first time been able to image the very same contrast agent, superparamagnetic iron oxide nanoparticles (SPIO-NPs), in rat SLNs by using both our frequency- and phase-gated magnetomotive ultrasound (MMUS) algorithm and conventional magnetic resonance imaging (MRI); MMUS post mortem, MRI in vivo. For both higher NP-concentration and smaller NPs, we found that the MMUS data showed a larger magnetomotive displacement (1.56 ± 0.43 and 1.94 ± 0.54 times larger, respectively) and that the MR-images were affected to a higher degree. The MMUS displacement also increased with lower excitation frequency (1.95 ± 0.64 times larger for 5 Hz compared with 15 Hz) and higher excitation voltage (2.95 ± 1.44 times larger for 30 V compared with 10 V). The results show that MMUS has potential to be used as bedside guidance during SLN surgery, imaging the same particles that were used in prior staging with other imaging techniques.

Magnetic resonance lymphography of sentinel lymph nodes in patients with breast cancer using superparamagnetic iron oxide: a feasibility study

BACKGROUND

The sentinel lymph node (SLN) biopsy technique using superparamagnetic iron oxide (SPIO) as a tracer instead of radioisotopes has been described. To further advance this technique, we evaluated preoperative SPIO-MR sentinel lymphography to facilitate the accurate identification of the lymphatic pathways and primary SLN.

METHODS

A prospective study was performed in ten patients with breast cancer and clinically negative axillary lymph nodes. None of the patients received preoperative chemotherapy. After 1.6 ml of SPIO (ferucarbotran) was injected in the subareolar breast tissue, sentinel axillary lymph nodes were detected by MRI in T2*-weighted gradient echo images and resected using the serial SPIO-SLN biopsy procedure with a handheld magnetometer.

RESULTS

In one patient, gadolinium-enhanced MR imaging was performed at the same time as SPIO-MR lymphography, and this patient was excluded from further analysis. In all patients (9/9) SLNs were detected by SPIO-MR sentinel lymphography and successfully identified at surgery. The number of SLNs detected by lymphography (mean 2.7) significantly correlated with SLNs identified at surgery (mean 2.2). One patient had nodal metastases. In one patient, skin color changed to brown at the injection site and resolved spontaneously. There were no severe reactions to the procedure or complications in any patient.

CONCLUSIONS

This is the first study to evaluate SPIO both as a contrast material in MR sentinel lymphography and as a tracer in SLN biopsy using an integrated method. The acquired three-dimensional imaging demonstrated excellent image quality and usefulness to identify SLN in conjunction with SLN biopsy.

Dextran and polymer polyethylene glycol (PEG) coating reduce both 5 and 30 nm iron oxide nanoparticle cytotoxicity in 2D and 3D cell culture

Superparamagnetic iron oxide nanoparticles are widely used in biomedical applications, yet questions remain regarding the effect of nanoparticle size and coating on nanoparticle cytotoxicity. In this study, porcine aortic endothelial cells were exposed to 5 and 30 nm diameter iron oxide nanoparticles coated with either the polysaccharide, dextran, or the polymer polyethylene glycol (PEG). Nanoparticle uptake, cytotoxicity, reactive oxygen species (ROS) formation, and cell morphology changes were measured. Endothelial cells took up nanoparticles of all sizes and coatings in a dose dependent manner, and intracellular nanoparticles remained clustered in cytoplasmic vacuoles. Bare nanoparticles in both sizes induced a more than 6 fold increase in cell death at the highest concentration (0.5 mg/mL) and led to significant cell elongation, whereas cell viability and morphology remained constant with coated nanoparticles. While bare 30 nm nanoparticles induced significant ROS formation, neither 5 nm nanoparticles (bare or coated) nor 30 nm coated nanoparticles changed ROS levels. Furthermore, nanoparticles were more toxic at lower concentrations when cells were cultured within 3D gels. These results indicate that both dextran and PEG coatings reduce nanoparticle cytotoxicity, however different mechanisms may be important for different size nanoparticles.

MR imaging of rectal cancer before and after chemoradiation therapy

PURPOSE

This study was done to determine the diagnostic accuracy of magnetic resonance (MR) imaging in patients with rectal carcinoma by comparing post-chemoradiation MR imaging with pathological specimens.

MATERIALS AND METHODS

We enrolled 39 patients with locally advanced rectal cancer. All patients received chemoradiation therapy before surgery and neoadjuvant chemoradiation therapy followed by MR imaging. MR images were analysed by a team of two expert radiologists unaware of the clinical and histopathological findings.

RESULTS

Following neoadjuvant chemoradiation therapy, the analysis of MR images showed 23 (59%) patients with a rectal disease staged ≤T2 and 16 (41%) with a disease staged >T2. Post-treatment histological staging (TNM) revealed 13 patients with a disease >T2 and 26 patients with a disease ≤T2. Cohen's kappa to measure concordance between post-chemoradiation MR staging and histological response showed 83.6% concordance for disease confined to the serosa (≤T3): concordance was 97.22% for disease ≤N1 and 33.33% for disease >N1.

CONCLUSIONS

MR imaging is critical for discovering T3 disease; moreover, morphological MR imaging does not always provide the opportunity to discern small residual cancer cells hidden in fibrotic tissue that could cause involvement of circumferential resection margin (CRM) on histology.

99mTc-labeled superparamagnetic iron oxide nanoparticles for multimodality SPECT/MRI of sentinel lymph nodes

The purpose of this study was to develop multimodality SPECT/MRI contrast agents for sentinel lymph node (SLN) mapping in vivo.

METHODS

Nanoparticles with a solid iron oxide core and a polyethylene glycol coating were labeled with (99m)Tc. The labeling efficiency was determined with instant thin-layer chromatography and magnetic separation. The stability of the radiolabeled superparamagnetic iron oxide nanoparticles (SPIONs) was verified in both sterile water and human serum at room temperature 6 and 24 h after labeling. Five Wistar rats were injected subcutaneously in the right hind paw with (99m)Tc-SPIONs (25-50 MBq, ∼0.2 mg of Fe) and sacrificed 4 h after injection. Two animals were imaged with SPECT/MRI. All 5 rats were dissected; the lymph nodes, liver, kidneys, spleen, and hind paw containing the injection site were removed and weighed; and activity in the samples was measured. The microdistribution within the lymph nodes was studied with digital autoradiography.

RESULTS

The efficiency of labeling of the SPIONs was 99% 6 h after labeling in both water and human serum. The labeling yield was 98% in water and 97% in human serum 24 h after labeling. The SLN could be identified in vivo with SPECT/MRI. The accumulation of (99m)Tc-SPIONs (as the percentage injected dose/g [%ID/g]) in the SLN was 100 %ID/g, whereas in the liver and spleen it was less than 2 %ID/g. Digital autoradiography images revealed a nonhomogeneous distribution of (99m)Tc-SPIONs within the lymph nodes; nanoparticles were found in the cortical, subcapsular, and medullary sinuses.

CONCLUSION

This study revealed the feasibility of labeling SPIONs with (99m)Tc. The accumulation of (99m)Tc-SPIONs in lymph nodes after subcutaneous injection in animals, verified by SPECT/MRI, is encouraging for applications in breast cancer and malignant melanoma.

Interaction between novel porphyrin-dextran nanoparticles and human serum albumin

A novel porphyrin-dextran coated Fe3O4 nanoparticle (5) was designed and synthesized. The structure of 5 was confirmed by IR, UV-vis and inductively coupled plasma atomic emission spectrometry, and dynamic laser scattering (DLS); magnetic property was measured by a vibrating sample magnetometer (VSM). The interaction between compound 5 and human serum albumin (HSA) was investigated through UV-vis absorbance spectra and fluorospectrophotometer, compared with the 5-(4-aminophenyl)-10,15,20-tris-(4-sulfonatophenyl)porphyrin, trisodium salt (3). The results showed compound 5 containing porphyrin moiety and 3 could interact with HSA. The quenching constant (Ksv) was 4.739 × 105 M-1 for 3, and 2.846 × 105 M-1 for 5; the apparent affinity binding constant (KA) was 8.562 × 103 M-1 for 3, and 4.978 × 104 M-1 for 5.

Targeted delivery of mannan-coated superparamagnetic iron oxide nanoparticles to antigen-presenting cells for magnetic resonance-based diagnosis of metastatic lymph nodes in vivo

Metastatic lymph nodes (LN) originate from primary cancer cells that metastasize to the lymphatic system. It is difficult to non-invasively discriminate between metastatic LN and normal LN because of their similarities in size and shape. Magnetic resonance (MR) contrast agents are widely utilized to enhance the image contrast among different tissues. Currently available dextran-based contrast agents are non-specifically internalized by macrophages. Therefore, the aim of this study was to develop mannan-coated superparamagnetic iron oxide nanoparticles (mannan-SPION) for specific delivery to immune cells in LN by receptor-mediated endocytosis for facilitated uptake in the target cells and faster acquisition of MR images. Mannan is a water soluble polysaccharide with a high content of D-mannose residues that can be recognized by mannose receptors on activated macrophages and dendritic cells. Mannan-SPION are proven to be suitable for MRI due to their small size, excellent aqueous stability, and lower cytotoxicity. Mannan-SPION are taken up by antigen-presenting cells such as macrophages and dendritic cells, which could be confirmed by Prussian blue and fluorescent staining. In addition, mannan-SPION exhibit enhanced delivery efficiency in targeting macrophages in LN in vivo compared with polyvinyl alcohol (PVA)-SPION. More specifically, the enhancement of MRI of LN by mannan-SPION increased dramatically during the earlier stages after intravenous injection, compared with PVA-SPION as a control, which indicates the potential for successful and early detection of metastastatic LN.

Preclinical lymphatic imaging

Noninvasive in vivo imaging of lymphatic vessels and lymphatic nodes is expected to fulfill the purpose of analyzing lymphatic vessels and their function, understanding molecular mechanisms of lymphangiogenesis and lymphatic spread of tumors, and utilizing lymphatic molecular markers as a prognostic or diagnostic indicator. In this review, we provide a comprehensive summary of in vivo imaging modalities for detecting lymphatic vessels, lymphatic drainage, and lymphatic nodes, which include conventional lymphatic imaging techniques such as dyes and radionuclide scintigraphy as well as novel techniques for lymphatic imaging such as optical imaging, computed tomography, magnetic resonance imaging, ultrasound, positron emission tomography using lymphatic biomarkers, photoacoustic imaging, and combinations of multiple modalities. The field of lymphatic imaging is ever evolving, and technological advances, combined with the development of new contrast agents, continue to improve the research of lymphatic vascular system in health and disease states as well as to improve the accuracy of diagnosis in the relevant diseases.

Characterization of mediastinal lymphadenopathy with diffusion-weighted imaging

PURPOSE

To predict malignancy of mediastinal lymphadenopathy with diffusion-weighted imaging.

MATERIAL AND METHODS

A prospective study was conducted on 35 patients with mediastinal lymphadenopathy (28 malignant and seven benign nodes). They underwent echoplanar diffusion-weighted magnetic resonance imaging of the mediastinum with b-factors of 0, 300 and 600 s/mm(2). The apparent diffusion coefficient (ADC) values of the mediastinal lymph nodes were calculated. The ADC values were correlated with the biopsy results and statistical analysis was done. A value of P<.05 was considered significant.

RESULTS

The mean ADC value of malignant mediastinal lymphadenopathy (1.06±0.3×10(-3) mm(2)/s) was significantly lower (P=.001) than that of benign lymphadenopathy (2.39±0.7×10(-3) mm(2)/s). There was an insignificant difference in the ADC values between metastatic and lymphomatous mediastinal lymph nodes (P=.32) as well as within benign nodes (P=.07). When an ADC value of 1.85×10(-3) mm(2)/s was used as a threshold value for differentiating malignant mediastinal nodes from benign nodes, the best results were obtained with an accuracy of 83.9%, a sensitivity of 96.4%, a specificity of 71.4%, a negative predictive value of 95.2% and a positive predictive value of 77.1%. The area under the curve was 0.98.

CONCLUSION

Diffusion weighted magnetic resonance imaging is a promising noninvasive imaging modality that can be used for characterization of mediastinal lymphadenopathy and differentiation of malignant from benign mediastinal lymph nodes.

Temporal and noninvasive monitoring of inflammatory-cell infiltration to myocardial infarction sites using micrometer-sized iron oxide particles

Micrometer-sized iron oxide particles (MPIO) are a more sensitive MRI contrast agent for tracking cell migration compared to ultrasmall iron oxide particles. This study investigated the temporal relationship between inflammation and tissue remodeling due to myocardial infarction (MI) using MPIO-enhanced MRI. C57Bl/6 mice received an intravenous MPIO injection for cell labeling, followed by a surgically induced MI seven days later (n=7). For controls, two groups underwent either sham-operated surgery without inducing an MI post-MPIO injection (n=7) or MI surgery without MPIO injection (n=6). The MRIs performed post-MI showed significant signal attenuation around the MI site for the mice that received an intravenous MPIO injection for cell labeling, followed by a surgically induced MI seven days later, compared to the two control groups (P<0.01). The findings suggested that the prelabeled inflammatory cells mobilized and infiltrated into the MI site. Furthermore, the linear regression of contrast-to-noise ratio at the MI site and left ventricular ejection function suggested a positive correlation between the labeled inflammatory cell infiltration and cardiac function attenuation during post-MI remodeling (r2=0.98). In conclusion, this study demonstrated an MRI technique for noninvasively and temporally monitoring inflammatory cell migration into the myocardium while potentially providing additional insight concerning the pathologic progression of a myocardial infarction.

Diagnostic performance of USPIO-enhanced MRI for lymph-node metastases in different body regions: a meta-analysis

OBJECTIVES

USPIO (ultrasmall superparamagnetic iron oxide contrast agent) MRI was a promising imaging modality in the detection of lymph-node metastases. And this meta-analysis is performed to compare the diagnostic accuracy of USPIO-enhanced MRI with non-enhanced MRI, USPIO-enhanced MRI in various body regions, and postcontrast alone for diagnosis of lymph-node metastases.

METHODS

A comprehensive and systematic search was conducted in PubMed and EMBASE databases. After a systematic review of the studies, sensitivity, specificity, the Q* value and other measures of accuracy of USPIO-enhanced MRI in the diagnosis of lymph-node metastases were summarized. The overall test performance was based on summary receiver operating characteristic curves.

RESULTS

Summary of ROC curve analysis for per-lymph-node data shows a pooled sensitivity of 0.90 (95% confidential interval [CI]: 0.88-0.91) and overall specificity of 0.96 (95% CI: 0.95-0.97) for USPIO-enhanced MRI, the Q* value for USPIO-enhanced MRI is 0.9195, diagnostic odds ratio (DOR) is 162.28 (95% CI: 91.82-286.81). Non-enhanced MRI had less overall sensitivity 0.39 (95% CI: 0.34-0.43) and specificity 0.90 (95% CI: 0.89-0.91), respectively, the Q* value for USPIO-enhanced MRI was 0.6321, DOR is 5.81 (95% CI: 3.64-9.82). Postcontrast MRI alone had sensitivity 0.85 (95% CI: 0.81-0.88) and specificity 0.93 (95% CI: 0.91-0.95), respectively, the Q* value for USPIO-enhanced MRI was 0.8976, DOR is 76.92 (95% CI: 34.21-172.93). There was significant heterogeneity for studies reporting enhanced MRI and non-enhanced MRI.

CONCLUSIONS

This meta-analysis has shown that USPIO-enhanced MRI offers higher diagnostic performance than conventional MRI, and is sensitive and specific for the detection of lymph-node metastases. Postcontrast images alone can equate diagnostic performance pre- and postcontrast MRI has achieved for lymph-node characterization. And the role of USPIO-enhanced MRI in clinical practice still needs to be investigated in future studies.

A novel method to prepare water-dispersible magnetic nanoparticles and their biomedical applications: magnetic capture probe and specific cellular uptake

A novel and simple method to form water-dispersed magnetic nanoparticles was successfully developed through glucosaminic acid-surface modification of iron oxide nanoparticles. The resultant glucosaminic acid-modified magnetic nanoparticles (GA-MNPs) had not only good uniformity in spherical shape with diameter of about 10-13 nm, but also possessed excellent water-dispersity and stability. In cell culture experiments, the internalization of GA-MNPs into different kinds of cells was observed over a 5-day period. The results indicated that the internalization of GA-MNPs into mouse macrophage cells and mouse embryonic fibroblast cells was not observed after 40 h of culturing. However, the GA-MNPs were internalized quickly into cancer cells after just 24 h of culturing. TEM images of the GA-MNPs uptake in ECA-109 cells were used to study the internalization mechanisms of GA-MNPs and their distribution in ECA-109 cells. Additionally, a water-dispersed magnetic capture probe was prepared by immobilization of oligonucleotides onto GA-MNPs, and the probe was used for detection and separation of their complementary oligonucleotides sequence.

MR relaxivity measurement of iron oxide nano-particles for MR lymphography applications

The aim of this study was to assess the T1, T2 and T2* relaxivity of Ultrasmall Super Paramagnetic Iron Oxide (USPIO) nano-particles in vitro and in vivo in rat models with magnetic resonance imaging at 1.5T. First, relaxation properties of USPIO nano-particles at different doses were measured using related SE and GRE MR imaging protocols. The relation between dose and relaxation were observed which is linear; Higher dose of the nano-particles means higher relaxivity. Based on this relation, an optimum protocol can be proposed for obtaining the best image contrast at each situation. Then detection ability of MRI protocols was studied for USPIO nano-particles with injection of the particles in the rat. The optimum MR protocols were used to observe the signal change of lymph nodes in rat.

Transrectal high-intensity focused ultrasound ablation of prostate cancer: Effective treatment requiring accurate imaging

Transrectal HIFU ablation has become a reasonable option for the treatment of localized prostate cancer in non-surgical patients, with 5-year disease-free survival similar to that of radiation therapy. It is also a promising salvage therapy of local recurrence after radiation therapy. These favourable results are partly due to recent improvements in prostate cancer imaging. However, further improvements are needed in patient selection, pre-operative localization of the tumor foci, assessment of the volume treated and early detection of recurrence. A better knowledge of the factors influencing the HIFU-induced tissue destruction and a better pre-operative assessment of them by imaging techniques should improve treatment outcome. Whereas prostate HIFU ablation is currently performed under transrectal ultrasound guidance, MR guidance with real-time operative monitoring of temperature will be available in the near future. If this technique will give better targeting and more uniform tissue destruction, its cost-effectiveness will have to be carefully evaluated. Finally, a recently reported synergistic effect between HIFU ablation and chemotherapy opens possibilities for treatment in high-risk or clinically advanced tumors.

USPIO-enhanced MR imaging of macrophage infiltration in native and transplanted kidneys: initial results in humans

The purpose of this study was to evaluate the detection and characterization of macrophage infiltration in native and transplanted kidneys using ultrasmall superparamagnetic iron oxide particles (USPIO). Among 21 patients initially enrolled, 12 scheduled for renal biopsy for acute or rapidly progressive renal failure (n = 7) or renal graft rejection (n = 5) completed the study. Three magnetic resonance (MR) sessions were performed with a 1.5-T system, before, immediately after and 72 h after i.v. injection of USPIO at doses of 1.7-2.6 mg of iron/kg. Signal intensity change was evaluated visually and calculated based on a region of interest (ROI) positioned on the kidney compartments. Histological examination showed cortical macrophage infiltration in four patients (>5 macrophages/mm(2)), two in native kidneys (proliferative extracapillary glomerulonephritis) and two in transplants (acute rejection). These patients showed a 33 +/- 18% mean cortical signal loss on T2*-weighted images. In the remaining eight patients, with <5 macrophages/mm(2), there was no cortical signal loss. However, in three of these, presenting with ischemic acute tubular necrosis, a strong (42 +/- 18%) signal drop was found in the medulla exclusively. USPIO-enhanced MR imaging can demonstrate infiltration of the kidneys by macrophages both in native and transplanted kidneys and may help to differentiate between kidney diseases.

Iron hydroxide nanoparticles coated with poly(ethylene glycol)-poly(aspartic acid) block copolymer as novel magnetic resonance contrast agents for in vivo cancer imaging

PEG-coated beta-FeOOH nanoparticles were prepared through electrostatic complex formation of iron oxide nanoparticles with poly(ethylene glycol)-poly(aspartic acid) block copolymer [PEG-P(Asp)] in distilled water. By dynamic light scattering (DLS) measurement, the nanopaticle size was determined to be 70 nm with narrow distribution. The FT-IR and zeta potential experimental results proved that PEG-PAsp molecules bound to the surface of the iron oxide nanoparticles via the coordination between the carboxylic acid residues in the PAsp segment of the block copolymer and the surface Fe of the beta-FeOOH nanoparticles. The PEG-coated nanoparticles revealed excellent solubility and stability in aqueous solution as well as in physiological saline. In vivo MRI experiments on tumor-bearing mice demonstrated that the PEG-coated nanoparticles prepared by the current approach achieved an appreciable accumulation into solid tumor, suggesting their potential utility as tumor-selective MRI contrast agents.

Preoperative staging of rectal cancer with MR Imaging: correlation with surgical and histopathologic findings

Rectal cancer is a common malignancy that continues to have a highly variable outcome, with local pelvic recurrence after surgical resection usually leading to incurable disease. The success of tumor excision depends largely upon accurate tumor staging and appropriate surgical technique, although the results of recent surgical trials indicate that evaluation of the involvement of the mesorectal fat and mesorectal fascia is even more important than T staging for treatment planning. Magnetic resonance (MR) imaging is increasingly being used to evaluate tumor resectability in patients with rectal cancer and to determine which patients can be treated with surgery alone and which will require radiation therapy to promote tumor regression. High-spatial-resolution MR imaging has proved useful in clarifying the relationship between a tumor and the mesorectal fascia, which represents the circumferential resection margin at total mesorectal excision. Phased-array surface coil MR imaging in particular plays a vital role in the therapeutic management of rectal cancer. At present, phased-array MR imaging best fulfills the clinical requirements for preoperative staging of rectal cancer. However, preoperative evaluation of the other prognostic factor, nodal status, is still problematic, and further studies will be needed to better define the role of MR imaging in this context.

Prostate cancer evaluated with ferumoxtran-10-enhanced T2*-weighted MR Imaging at 1.5 and 3.0 T: early experience

PURPOSE

To prospectively evaluate the feasibility of ferumoxtran-10-enhanced magnetic resonance (MR) imaging at high magnetic field strength (3.0 T) and to compare image quality between 1.5- and 3.0-T MR imaging in terms of lymph node detection in patients with prostate cancer.

MATERIALS AND METHODS

This study was institutional review board approved, and all patients gave written informed consent. Forty-eight consecutive patients aged 51-79 years (mean, 65.5 years) with prostate cancer were enrolled. T2*-weighted 1.5- and 3.0-T MR images of the pelvis were acquired in a sagittal plane parallel to the psoas muscle 24 hours after ferumoxtran-10 administration. A pelvic and body phased-array coil was used and yielded an in-plane resolution of 0.56 x 0.56 x 3.00 mm at 1.5 T and 0.50 x 0.50 x 2.50 mm at 3.0 T. All images were evaluated by three readers for total image quality, lymph node border delineation, muscle-fat contrast, and vessel-fat contrast. Statistical significance was calculated by using the Mann-Whitney U test. Subsequently, the general linear mixed model was used to estimate the contributions of three factors-patient, reader, and technique-to the variability of the imaging results.

RESULTS

Significantly (P < .05) better muscle-fat contrast, vessel-fat contrast, lymph node border delineation, and total image quality were observed at 3.0-T MR imaging. The general linear mixed model revealed that the variability of all results could be attributed to the use of 3.0-T imaging.

CONCLUSION

Ferumoxtran-10-enhanced MR imaging can be performed at high magnetic field strengths and result in improved image quality, which may lead to improved detection of small positive lymph nodes.

Antibiofouling Polymer-Coated Superparamagnetic Iron Oxide Nanoparticles as Potential Magnetic Resonance Contrast Agents for in Vivo Cancer Imaging

We report the fabrication and characterization of antifouling polymer-coated magnetic nanoparticles as nanoprobes for magnetic resonance (MR) contrast agents. Magnetite superparamagnetic iron oxide nanoparticles (SPION) were coated with the protein- or cell-resistant polymer, poly(TMSMA-r-PEGMA), to generate stable, protein-resistant MR probes. Coated magnetic nanoparticles synthesized using two different preparation methods (in situ and stepwise, respectively) were both well dispersed in PBS buffer at a variety of pH conditions (pH 1-10). In addition, dynamic light scattering data revealed that their sizes were not altered even after 24 h of incubation in 10% serum containing cell culture medium, indicative of a lack of protein adsorption on their surfaces. When the antibiofouling polymer-coated SPION were incubated with macrophage cells, uptake was significantly lower in comparison to that of the popular contrast agent, Feridex I.V., suggesting that the polymer-coated SPION can be long-circulated in plasma by escaping from uptake by the reticular endothelial system (RES) such as macrophages. Indeed, when the coated SPION were administered to tumor xenograft mice by intravenous injection, the tumor could be detected in T2-weighted MR images within 1 h as a result of the accumulation of the nanomagnets within the tumor site. Although the poly(TMSMA-r-PEGMA)-coated SPION do not have any targeting ligands on their surface, they are potentially useful for cancer diagnosis in vivo.

Breast imaging. Preoperative breast cancer staging: comparison of USPIO-enhanced MR imaging and 18F-fluorodeoxyglucose (FDC) positron emission tomography (PET) imaging for axillary lymph node staging--initial findings

Magnetic resonance (MR) imaging after ultra-small super paramagnetic iron oxide (USPIO) injection and 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) for preoperative axillary lymph node staging in patients with breast cancer were evaluated using histopathologic findings as the reference standard. USPIO-enhanced MR and FDG-PET were performed in ten patients with breast cancer who were scheduled for surgery and axillary node resection. T2-weighted fast spin echo, T1-weighted three-dimensional (3D) gradient echo, T2*-weighted gradient echo and gadolinium-enhanced T1-weighted 3D gradient echo with spectral fat saturation were evaluated. MR imaging before USPIO infusion was not performed. The results were correlated with FDG-PET (acquired with dedicated PET camera, visual analysis) and histological findings. The histopathologic axillary staging was negative for nodal malignancy in five patients and positive in the remaining five patients. There was one false positive finding for USPIO-enhanced MR and one false negative finding for FDG-PET. A sensitivity (true positive rate) of 100%, specificity (true negative rate) of 80%, positive predictive value of 80%, and negative predictive value of 100% were achieved for USPIO-enhanced MR and of 80%, 100%, 100%, 80% for FDG-PET, respectively. The most useful sequences in the detection of invaded lymph nodes were in the decreasing order: gadolinium-enhanced T1-weighted 3D gradient echo with fat saturation, T2*-weighted 2D gradient echo, T1-weighted 3D gradient echo and T2-weighted 2D spin echo. In our study, USPIO-enhanced T1 gradient echo after gadolinium injection and fat saturation emerged as a very useful sequence in the staging of lymph nodes. The combination of USPIO-enhanced MR and FDG-PET achieved 100% sensitivity, specificity, PPV and NPV. If these results are confirmed, the combination of USPIO MR with FDG-PET has the potential to identify the patient candidates for axillary dissection versus sentinel node lymphadenectomy.

Indirect magnetic resonance lymphangiography in patients with lymphedema preliminary results in humans

PURPOSE

To assess the feasibility of indirect magnetic resonance (MR) lymphangiography with intracutaneous injection of gadodiamide, a commercially available, non-ionic, extracellular paramagnetic contrast agent for the detection of lymphatic vessels in patients with lymphedema.

MATERIALS AND METHODS

In 2005, three patients with lymphedema of the lower extremities (1 primary, 2 secondary) were referred by the Foeldi Clinic for Lymphology for indirect magnetic resonance lymphangiography. 4.5 mL of gadodiamide and 0.5 mL of mepivacainhydrochloride 1% were injected intracutaneously into the dorsal aspect of each foot. MR imaging was performed with a 1.5-T system equipped with high-performance gradients. For indirect magnetic resonance lymphangiography, a 3D Fast Low Angle Shot (FLASH) sequence (TR/TE: 5.1/1.23; flip angle: 25; matrix: 448 x 448; bandwidth: 330 Hz/pixel; 6/8 rectangular field of view with a maximum dimension of 500 mm; slices: 88; voxel size: 2.0 mm x 1.0 mm x 1.0mm; acquisition time: 0 min 31 s) was used.

RESULTS

Indirect magnetic resonance lymphangiography depicted lymphatic vessels of the lower and upper leg, and inguinal lymph nodes in all three patients. After 5 min of contrast material application, concomitant venous enhancement was detected. Collateral vessels with dermal back-flow were seen in two patients. A lymphocele in the inguinal region with the afferent lymphatic vessel was depicted in one patient.

CONCLUSION

In the presented small study group, indirect magnetic resonance lymphangiography was technically feasible, and no complications were observed after intracutaneous injection of gadodiamide. Visualizing the lymphatic vessels and accompanying complications non-invasively and without the use of radiation, the presented method has the capability to become a routine diagnostic imaging tool in patients with primary and secondary lymphedema. The method is not able to characterize lymph node morphology, but could provide additional information about the lymphatic vessels when lymph nodes are examined, e.g. with super-paramagnetic iron oxide particles.

CT and MRI of Lung Cancer

Computed tomography (CT) is still the cornerstone of imaging studies in the preoperative staging and post- therapeutic evaluation of lung cancer. The most recent developments in multidetector technology have dramatically improved the temporal and spatial resolution of CT. In the mean time, magnetic resonance imaging (MRI) has not become a routine examination in lung imaging and is today only used as a problem-solving tool in patients in whom CT remains equivocal. This article will describe the current tools developed in the multidetector CT era for evaluating the lung, and state-of-the-art MR examination of the chest. Then, the role of CT and MRI in nodule detection, the distinction between benign and malignant nodules, and the benefit of CT and MRI in the staging and post-therapeutic evaluation of lung cancer will be covered.

Ferumoxtran-10-enhanced MR lymphangiography: does contrast-enhanced imaging alone suffice for accurate lymph node characterization?

OBJECTIVE

Ferumoxtran-10 is a lymphotropic MR contrast agent that is currently under investigation. It has been shown to be effective in staging lymph nodes of patients with various primary malignancies. The current technique with ferumoxtran-10 involves imaging before and 24 hr after contrast administration. The purpose of this study was to evaluate the accuracy of ferumoxtran-10-enhanced images alone in characterizing lymph nodes for oncologic staging 24 hr after contrast enhancement.

MATERIALS AND METHODS

Seventy-seven patients (58 men, 19 women) with proven primary cancer (bladder [n = 20], breast [n = 10], endometrial [n = 1], renal [n = 3], penile [n = 4], prostate [n = 31], rectal [n = 1], testicular [n = 5], and ureteral [n = 2]) who were scheduled for surgical lymph node dissection were enrolled in the study. In these patients, 169 lymph nodes (mean size, 11.2 mm) were evaluated on T2*-weighted gradient-refocused echo MRI at l.5 T both before and 24-36 hr after the IV administration of ferumoxtran-10 (2.6 mg Fe/kg). Two blinded reviewers with differing levels of interpreting experience separately performed qualitative image evaluation. A 6-point scale was used to characterize lymph nodes on contrast-enhanced images alone and on combined unenhanced and contrast-enhanced images. Receiver operating characteristic (ROC) analysis was performed separately for both reviewers.

RESULTS

Of the 169 lymph nodes evaluated, 55 were benign and 114 malignant by histopathologic analysis. The results of the ROC analysis comparing contrast-enhanced images ([A(z) = area under ROC curve] reviewer 1, A(z) = 0.92; reviewer 2, A(z) = 0.94) alone with combined unenhanced and contrast-enhanced images (reviewer 1, A(z) = 0.94; reviewer 2, A(z) = 0.93) showed a statistically significant difference (p = 0.01) for reviewer 1 but no difference for reviewer 2 (p = 0.88). Reviewer 2 was more experienced in interpreting ferumoxtran-10-enhanced images than reviewer 1.

CONCLUSION

On ferumoxtran-10-enhanced MR lymphangiography, contrast-enhanced images alone may suffice for lymph node characterization. However, a certain level of interpretation experience may be required before contrast-enhanced images can be used alone.

Lymphotropic nanoparticle enhanced MR imaging (LNMRI) technique for lymph node imaging

Accurate nodal staging is important in the management of any primary malignancy. The presence of nodal metastases has both therapeutic and prognostic implications. Lymphotropic nanoparticles are a new class of MRI contrast agents, which are promising in detecting minimal metastatic nodal disease particularly in normal sized lymph nodes. This paper discusses the technique and interpretation of lymphotropic nanoparticle enhanced MRI (LNMRI) and reviews the various trials evaluating nodal staging with ferumoxtran-10 enhanced MRI.

IRM de la prostate : optimisation des protocoles techniques

This article details the imaging protocols for prostate MRI and the influence on image quality of each particular setting: type of coils to be used (endorectal or external phased-array coils?), patient preparation, type of sequences, spatial resolution parameters. The principle and technical constraints of dynamic contrast-enhanced MRI are also presented, as well as the predictable changes due to the introduction of high-field strength (3T) scanners.