Comparison of Lymphotropic Nanoparticle-Enhanced MRI Sequences in Patients with Various Primary Cancers

Advancing MRI with magnetic nanoparticles: a comprehensive review of translational research and clinical trials

The nexus of advanced technology and medical therapeutics has ushered in a transformative epoch in contemporary medicine. Within this arena, Magnetic Resonance Imaging (MRI) emerges as a paramount tool, intertwining the advancements of technology with the art of healing. MRI's pivotal role is evident in its broad applicability, spanning from neurological diseases, soft-tissue and tumour characterization, to many more applications. Though already foundational, aspirations remain to further enhance MRI's capabilities. A significant avenue under exploration is the incorporation of innovative nanotechnological contrast agents. Forefront among these are Superparamagnetic Iron Oxide Nanoparticles (SPIONs), recognized for their adaptability and safety profile. SPION's intrinsic malleability allows them to be tailored for improved biocompatibility, while their functionality is further broadened when equipped with specific targeting molecules. Yet, the path to optimization is not devoid of challenges, from renal clearance concerns to potential side effects stemming from iron overload. This review endeavors to map the intricate journey of SPIONs as MRI contrast agents, offering a chronological perspective of their evolution and deployment. We provide an in-depth current outline of the most representative and impactful pre-clinical and clinical studies centered on the integration of SPIONs in MRI, tracing their trajectory from foundational research to contemporary applications.

Ferumoxytol-enhanced MR imaging for differentiating intrapancreatic splenules from other tumors

Objectives

Ferumoxytol is an ultra-small superparamagnetic iron oxide (USPIO) agent that is taken up by splenic tissue. This study describes our initial institutional experience of ferumoxytol-enhanced MRI (feMRI) for differentiating intrapancreatic splenules (IPS) from other pancreatic lesions.

Methods

In this retrospective study, patients with computed tomographic imaging that identified small enhancing lesions in the tail of the pancreas subsequently underwent feMRI for further characterization. The feMRI protocol included T2-weighted (T2w) imaging with and without fat suppression (FS), R2* mapping, diffusion-weighted imaging (DWI), and T1-weighted (T1w) imaging with FS, prior to contrast injection. Immediately after slow intravenous infusion with 3 mg/kg body weight ferumoxytol, T1w was repeated. Delayed imaging with all sequences were obtained 24–72 h after ferumoxytol administration.

Results

Seven patients underwent feMRI. In two patients, the pancreatic lesions were presumed as pancreatic neuroendocrine tumor (PNET) from feMRI and in the remaining 5 IPS. One of the two patients with PNET was symptomatic for NET. In another symptomatic patient with pathologically proven duodenal NET and suspected PNET, the pancreatic lesion was proven to be an IPS on feMRI. IPS demonstrated strong negative enhancement in feMRI on T2w and increased R2* values consistent with splenic tissue, while the presumed PNETs did not enhance. T2w FS was helpful on the pre-contrast images to identify IPS, while R2* did on post-contrast images. Neither DWI nor T1w contributed to differentiating PNETs from IPS.

Conclusions

This study demonstrates the potential utility of feMRI as a helpful adjunct diagnostic tool for differentiating IPS from other pancreatic lesions. Further studies in larger patient cohorts are needed.

SPIO processing in macrophages for MPI: The breast cancer MPI-SNLB-concept

Introduction

Breast cancer (BC) is the most common cancer in women worldwide. We aim to develop a new sentinel lymph node biopsy (SLNB) method with superparamagnetic iron oxide nanoparticles (SPIOs) and magnetic particle imaging (MPI) in BC to avoid tissue damaging while axillary surgery. As we know from i.v. SPIO application in magnetic resonance imaging (MRI), macrophages (MP) are key role player in processing of SPIOs (e.g. in liver) causing a drop of signal intensity. But, knowledge lacks concerning enrichment processes of SPIOs after injection in breast tissue, the adjacent lymphatic tissues and associated cells, especially in BC and metastatic lymph nodes. We already evaluated the distribution of SPIOs in an in vivo healthy and tumor mouse model. Based on these studies we investigate the processing of the SPIOs in MP.

Material and Methods

To evaluate SPIO processing, a mouse MP cell line J774A.1 was incubated either by Resovist in culture medium (RPMI, FBS), or culture medium only as control. MP were than analyzed by transmission electron microscopy (TEM). Additionally, this process was observed in vivo by multiphoton microscopy. Detection of SPIOs was realized by excitation at 1200 nm.

Results

Resovist had no toxic effects on cells.MP showed activity in phagocytosis of Resovist after incubation in TEM as well as in multiphoton microscopy. SPIOs were detectable within intracellular vesicles by TEM and 3-photon process. The first cell associated SPIO signal was detected after 1,5 min of incubation by in vivo imaging.

Conclusion

To our knowledge this is the first time a 3-photon device was used to image SPIOs in a bio-medical context. System wide scanning is known (MRI, MPI), but nowwe are also able to identify the link to subcellular processing and localization of SPIOs. Further processing of SPIOs in MP is under development.

Accurate prediction of nodal status in preoperative patients with pancreatic ductal adenocarcinoma using next-gen nanoparticle

OBJECTIVE

The objective of this study is to assess lymphotropic nanoparticle-enhanced magnetic resonance imaging (LNMRI) in identifying malignant nodal involvement in patients with pancreatic ductal adenocarcinoma.

METHODS

Magnetic resonance imaging was performed in 13 patients with known or high index of suspicion of pancreatic cancer and who were scheduled for surgical resection. Protocols included T2*-weighted imaging before and after administration of Ferumoxytol (Feraheme) for the evaluation of lymph node involvement. Eleven of the 13 patients underwent a Whipple procedure and lymph node dissection. Nodes that lacked contrast uptake were deemed malignant, and those that demonstrated homogeneous uptake were deemed benign.

RESULTS

A total of 264 lymph nodes were resection, of which 17 were malignant. The sensitivity and specificity of LNMRI was 76.5% and 98.4% at a nodal level and 83.3% and 80% at a patient level.

CONCLUSION

LNMRI demonstrated high sensitivity and specificity in patients with pancreatic ductal adenocarcinoma.

Does quantification of USPIO uptake-related signal loss allow differentiation of benign and malignant normal-sized pelvic lymph nodes?

Ultrasmall superparamagnetic iron oxide (USPIO) particles are promising contrast media, especially for molecular and cellular imaging besides lymph node staging owing to their superior NMR efficacy, macrophage uptake and lymphotropic properties. The goal of the present prospective clinical work was to validate quantification of signal decrease on high-resolution T(2)-weighted MR sequences before and 24-36 h after USPIO administration for accurate differentiation between benign and malignant normal-sized pelvic lymph nodes. Fifty-eight patients with bladder or prostate cancer were examined on a 3 T MR unit and their respective lymph node signal intensities (SI), signal-to-noise (SNR) and contrast-to-noise (CNR) were determined on pre- and post-contrast 3D T(2)-weighted turbo spin echo (TSE) images. Based on histology and/or localization, USPIO-uptake-related SI/SNR decrease of benign vs malignant and pelvic vs inguinal lymph nodes was compared. Out of 2182 resected lymph nodes 366 were selected for MRI post-processing. Benign pelvic lymph nodes showed a significantly higher SI/SNR decrease compared with malignant nodes (p < 0.0001). Inguinal lymph nodes in comparison to pelvic lymph nodes presented a reduced SI/SNR decrease (p < 0.0001). CNR did not differ significantly between benign and malignant lymph nodes. The receiver operating curve analysis yielded an area under the curve of 0.96, and the point with optimal accuracy was found at a threshold value of 13.5% SNR decrease. Overlap of SI and SNR changes between benign and malignant lymph nodes were attributed to partial voluming, lipomatosis, histiocytosis or focal lymphoreticular hyperplasia. USPIO-enhanced MRI improves the diagnostic ability of lymph node staging in normal-sized lymph nodes, although some overlap of SI/SNR-changes remained. Quantification of USPIO-dependent SNR decrease will enable the validation of this promising technique with the final goal of improving and individualizing patient care.

The role of magnetic resonance imaging in oncology

Conventional diagnostic magnetic resonance imaging (MRI) techniques have focused on improving the spatial resolution and image acquisition speed (whole-body MRI) or on new contrast agents. Most advances in MRI go beyond morphologic study to obtain functional and structural information in vivo about different physiological processes of tumor microenvironment, such as oxygenation levels, cellular proliferation, or tumor vascularization through MRI analysis of some characteristics: angiogenesis (perfusion MRI), metabolism (MRI spectroscopy), cellularity (diffusion-weighted MRI), lymph node function, or hypoxia [blood-oxygen-level-dependent (BOLD) MRI]. We discuss the contributions of different MRI techniques than must be integrated in oncologic patients to substantially advance tumor detection and characterization risk stratification, prognosis, predicting and monitoring response to treatment, and development of new drugs.

Contrast-enhanced MR imaging of lymph nodes in cancer patients

The accurate identification and characterization of lymph nodes by modern imaging modalities has important therapeutic and prognostic significance for patients with newly diagnosed cancers. The presence of nodal metastases limits the therapeutic options, and it generally indicates a worse prognosis for the patients with nodal metastases. Yet anatomic imaging (CT and MR imaging) is of limited value for depicting small metastatic deposits in normal-sized nodes, and nodal size is a poor criterion when there is no extracapsular extension or focal nodal necrosis to rely on for diagnosing nodal metastases. Thus, there is a need for functional methods that can be reliably used to identify small metastases. Contrast-enhanced MR imaging of lymph nodes is a non-invasive method for the analysis of the lymphatic system after the interstitial or intravenous administration of contrast media. Moreover, some lymphotrophic contrast media have been developed and used for detecting lymph node metastases, and this detection is independent of the nodal size. This article will review the basic principles, the imaging protocols, the interpretation and the accuracies of contrast-enhanced MR imaging of lymph nodes in patients with malignancies, and we also focus on the recent issues cited in the literature. In addition, we discuss the results of several pre-clinical studies and animal studies that were conducted in our institution.

Magnetic resonance lymphography in gynaecological malignancies

Following the submission of this article to Cancer Imaging, unfortunately the European manufacturer of ferumoxtran-10 (Guerbet) has withdrawn the product pending further phase III studies. This is secondary to the view of the Committee for Medicinal Products for Human Use that the phase III data did not provide adequate statistical demonstration of the product's efficacy.

Magnetic resonance lymphography holds much promise for the non-invasive evaluation of lymph nodes. The technique utilizes ultrasmall superparamagnetic particles of iron oxide and has been shown to be highly sensitive and specific in the diagnosis of malignant lymph nodes. This article reviews the technique and the performance of magnetic resonance lymphography in studies to date; alternative newer methods of nodal assessment such as fluorodeoxyglucose-positron emission tomography/computed tomography and diffusion-weighted magnetic resonance imaging are also discussed, with emphasis on gynaecological malignancies.

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.