Oral superparamagnetic contrast agent (ferumoxsil): tolerance and efficacy in MR imaging of gynecologic diseases

Advances of functional nanomaterials for magnetic resonance imaging and biomedical engineering applications

Functional nanomaterials have been widely used in biomedical fields due to their good biocompatibility, excellent physicochemical properties, easy surface modification, and easy regulation of size and morphology. Functional nanomaterials for magnetic resonance imaging (MRI) can target specific sites in vivo and more easily detect disease-related specific biomarkers at the molecular and cellular levels than traditional contrast agents, achieving a broad application prospect in MRI. This review focuses on the basic principles of MRI, the classification, synthesis and surface modification methods of contrast agents, and their clinical applications to provide guidance for designing novel contrast agents and optimizing the contrast effect. Furthermore, the latest biomedical advances of functional nanomaterials in medical diagnosis and disease detection, disease treatment, the combination of diagnosis and treatment (theranostics), multi-model imaging and nanozyme are also summarized and discussed. Finally, the bright application prospects of functional nanomaterials in biomedicine are emphasized and the urgent need to achieve significant breakthroughs in the industrial transformation and the clinical translation is proposed. This article is categorized under: Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Diagnostic Tools > Diagnostic Nanodevices Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

Nanomedicines - Tiny particles and big challenges

After decades of research, nanotechnology has been used in a broad array of biomedical products including medical devices, drug products, drug substances, and pharmaceutical-grade excipients. But like many great achievements in science, there is a fine balance between the risks and opportunities of this new technology. Some materials and surface structures in the nanosize range can exert unexpected toxicities and merit a more detailed safety assessment. Regulatory agencies such as the United States Food and Drug Administration or the European Medicines Agency have started dealing with the potential risks posed by nanomaterials. Considering that a thorough characterization is one of the key aspects of controlling such risks this review presents the regulatory background of nanosafety assessment and provides some practical advice on how to characterize nanomaterials and drug formulations. Further, the challenges of how to maintain and monitor pharmaceutical quality through a highly complex production processes will be discussed.

Advocating the Development of Next-Generation High-Relaxivity Gadolinium Chelates for Clinical Magnetic Resonance

The question of improved relaxivity, and potential efficacy therein, for a next-generation of magnetic resonance gadolinium chelates with extracellular distribution and renal excretion, which could also be viewed from the perspective of dose, is addressed on the basis of historical development, animal experimentation, and human trials. There was no systematic evaluation that preceded the choice of 0.1 mmol/kg as the standard dose for human imaging with the gadolinium chelates. In part, this dose was chosen owing to bloodwork abnormalities seen in phase I and phase II studies. Animal investigations and early clinical trials demonstrated improved lesion detectability at higher doses in the brain, liver, and heart. By designing an agent with substantially improved relaxivity, higher enhancement equivalent to that provided with the conventional gadolinium agents at high dose could be achieved, translating to improved diagnosis and, thus, clinical care. Implicit in the development of such high-relaxivity agents would be stability equivalent to or exceeding that of the currently approved macrocyclic agents, given current concern regarding dechelation and gadolinium deposition in the brain, skin, and bone with the linear agents that were initially approved. Development of such next-generation agents with a substantial improvement in relaxivity, in comparison with the current group of approved agents, with a 2-fold increase likely achievable, could lead to improved lesion enhancement, characterization, diagnosis, and, thus, clinical efficacy.

Leveraging Physiology for Precision Drug Delivery

Physiological characteristics of diseases bring about both challenges and opportunities for targeted drug delivery. Various drug delivery platforms have been devised ranging from macro- to micro- and further into the nanoscopic scale in the past decades. Recently, the favorable physicochemical properties of nanomaterials, including long circulation, robust tissue and cell penetration attract broad interest, leading to extensive studies for therapeutic benefits. Accumulated knowledge about the physiological barriers that affect the in vivo fate of nanomedicine has led to more rational guidelines for tailoring the nanocarriers, such as size, shape, charge, and surface ligands. Meanwhile, progresses in material chemistry and molecular pharmaceutics generate a panel of physiological stimuli-responsive modules that are equipped into the formulations to prepare “smart” drug delivery systems. The capability of harnessing physiological traits of diseased tissues to control the accumulation of or drug release from nanomedicine has further improved the controlled drug release profiles with a precise manner. Successful clinical translation of a few nano-formulations has excited the collaborative efforts from the research community, pharmaceutical industry, and the public towards a promising future of smart drug delivery.

In vivo delivery, pharmacokinetics, biodistribution and toxicity of iron oxide nanoparticles

Iron oxide nanoparticles (IONPs) have been extensively used during the last two decades, either as effective bio-imaging contrast agents or as carriers of biomolecules such as drugs, nucleic acids and peptides for controlled delivery to specific organs and tissues. Most of these novel applications require elaborate tuning of the physiochemical and surface properties of the IONPs. As new IONPs designs are envisioned, synergistic consideration of the body's innate biological barriers against the administered nanoparticles and the short and long-term side effects of the IONPs become even more essential. There are several important criteria (e.g. size and size-distribution, charge, coating molecules, and plasma protein adsorption) that can be effectively tuned to control the in vivo pharmacokinetics and biodistribution of the IONPs. This paper reviews these crucial parameters, in light of biological barriers in the body, and the latest IONPs design strategies used to overcome them. A careful review of the long-term biodistribution and side effects of the IONPs in relation to nanoparticle design is also given. While the discussions presented in this review are specific to IONPs, some of the information can be readily applied to other nanoparticle systems, such as gold, silver, silica, calcium phosphates and various polymers.

Magnetic-nanoparticle-doped carbogenic nanocomposite: an effective magnetic resonance/fluorescence multimodal imaging probe

A novel and facile approach is developed to synthesize a magnetic nanoparticle (iron oxide)-doped carbogenic nanocomposite (IO-CNC) for magnetic resonance (MR)/fluorescence imaging applications. IO-CNC is synthesized by thermal decomposition of organic precursors in the presence of Fe(3) O(4) nanoparticles with an average size of 6 nm. IO-CNC shows wavelength-tunable fluorescence properties with high quantum yield. Magnetic studies confirm the superparamagnetic nature of IO-CNC at room temperature. IO-CNC shows MR contrast behavior by affecting the proton relaxation phenomena. The measured longitudinal (r(1) ) and transverse (r(2) ) relaxivity values are 4.52 and 34.75 mM(-1) s(-1) , respectively. No apparent cytotoxicity is observed and the nanocomposite shows a biocompatible nature. In vivo MR studies show both T(1) and T(2) * contrast behavior of the nanocomposite. Fluorescence imaging indicates selective uptake of IO-CNC by macrophages in spleen.

Comparison of MR enteroclysis with colonoscopy in Crohn's disease--first locust bean gum study from Turkey

BACKGROUND/AIM

The aim of this study was to compare magnetic resonance enteroclysis (MRE) findings with those of colonoscopy, using locust bean gum (LBG) as an oral contrast agent in the diagnosis and follow-up of patients with Crohn's disease.

MATERIALS AND METHODS

Nine patients with histologically proven Crohn 's disease were enrolled in this study; MRE was performed within a week of colonoscopy. All patients were examined using a 1.5 T MR Scanner after per os administration of 850 mL of a combination of LBG and mannitol. After intravenous administration of 50 mg Eritromisin and 40 mg Scopolamine, images were obtained using a T2-weighted, balanced GRE, fat-suppressed T1-weighted sequence, before and after intravenous gadolinium administration. Bowel wall thickness and enhancement of inflamatory bowel wall were measured.

RESULTS

The oral ingestion of LBG was well tolerated and allowed optimal small and large bowel distention in all patients. MR findings correlated with the colonoscopy results. Additional inflammatory lesions of the colon and mesenteric inflamatory changes such as lymphadenopathy, conglomerate tumor, and fistulas were demonstrated. Contrast enhancement of the affected bowel wall was markedly increased and positive correlation was obtained between bowel wall enhancement and bowel wall thickness.

CONCLUSION

Gadolinium-enhanced MRE with oral locust bean gum is very efficient in the detection and follow-up of the intestinal and extraintestinal findings of Crohn's disease.

Basics of Magnetic Resonance Imaging and Magnetic Resonance Spectroscopy

In this chapter, the basic principles of magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) (Sects. 2.2, 2.3, and 2.4), the technical components of the MRI scanner (Sect. 2.5), and the basics of contrast agents and the application thereof (Sect. 2.6) are described. Furthermore, flow phenomena and MR angiography (Sect. 2.7) as well as diffusion and tensor imaging (Sect. 2.7) are elucidated.

Post-treatment fistulas in patients with rectal cancer: MRI with rectal superparamagnetic contrast agent

MRI is the standard modality in the pre- and post-treatment evaluation of patients with rectal cancer, particularly in those cases with locally advanced disease. We routinely employ a superparamagnetic iron oxide (SPIO) contrast enema to distend the rectal lumen and achieve maximal tumor-to-lumen contrast gradient. This practice also allowed the identification of a fistula in 24% of patients treated for rectal cancer. Contrast agent-related low intensity signal could be seen filling the tract and eventually opacifying surrounding organs (i.e., vagina) or collections (i.e., presacral abscess). Fistula formation after radiochemotherapy and surgery for rectal cancer is not uncommon. MRI with dark lumen contrast enema allows an effective demonstration of this complication in a high number of patients.

Small bowel

MR imaging, using modern equipment and a rigorous technical approach, can offer detailed morphologic information and functional data on the small bowel. The optimal study technique is debatable, although the oral administration of contrast material as a first-line approach is less expensive, faster, easier to perform, and better tolerated by patients. MR enteroclysis might be reserved for selected cases as a second-line study. The major clinical indication is the evaluation of patients who have suspected or known Crohn's disease. The absence of ionizing radiation, considering the young age of most of the patients and the frequency of the examinations, is an important advantage over other techniques (radiograph and CT enteroclysis).

Safety of magnetic resonance contrast media

Intravenous contrast media, specifically the gadolinium chelates, are well accepted for use in the clinical practice of magnetic resonance imaging. The gadolinium chelates are considered to be very safe and lack (in intravenous use) the nephrotoxicity found with iodinated contrast media. Minor adverse reactions, including nausea and hives, occur in a low percentage of cases. The four agents currently available in the United States cannot be differentiated on the basis of these adverse reactions. Severe anaphylactoid reactions are also known to occur with all agents, although these are uncommon. This review discusses the safety issues involved with intravenous administration of the gadolinium chelates and off-label use. The latter is common in clinical practice and permits broader application of these agents.

Synergistic effect between iron and gadolinium in MRI

Different combinations of iron glycerophosphate (Fe) and gadolinium-diethylene triamine pentaacetic acid (DTPA) (Gd) were imaged with a three-dimensional (3D) gradient-recalled echo (GRE), a 2D GRE, and a HASTE sequence on a 1.5-T MR scanner. A combination of Fe and Gd results in a synergistic effect, which improves the signal gain for selective 3D imaging of the colon and simultaneously decreases the endoluminal signal on the HASTE and 2D GRE images for better visualization of water and Gd-enhanced structures in the gut wall.

MRI of the female and male pelvis: current and future applications of contrast enhancement

Magnetic resonance imaging (MRI) of the pelvis has proven to be a most valuable diagnostic tool to examine pathologies of various organ systems in the pelvis. For most conditions MRI was found to be superior to other imaging modalities, like ultrasound and computed tomography. Controversy still exists on the value of intraluminal and intravenous contrast enhancement. This article gives an overview on currently available intraluminal and intravenous contrast agents. The techniques and results for contrast-enhanced MRI in the female and male pelvis are discussed based on a review of the literature. New developments and upcoming techniques, such as lymph node specific contrast agents and breathhold volumetric MRI, are described and initial results are presented.

Superparamagnetic agents in magnetic resonance imaging: physicochemical characteristics and clinical applications. A review

Superparamagnetic agents in magnetic resonance imaging: physico-chemical characteristics and clinical applications. Superparamagnetic agents have been the subject of extensive research over the last decade. They consist of iron oxide nanoparticles which are highly effective in Magnetic Resonance Imaging (MRI). The particle size varies widely and influences their physicochemical and pharmacokinetic properties. Their main present and future applications by the parenteral route are: imaging of gastrointestinal tract, liver and spleen, lymph nodes. Ultrasmall superparamagnetic iron oxide particles (USPIO) are also blood pool agents which could be used for perfusion imaging (i.e. brain or myocardial ischemic diseases) as well as for imaging of vessels in Magnetic Resonance Angiography. These agents open up an important field of research into more specific agents adapted to clinicians' needs in diagnostic imaging.

MR imaging in pelvic inflammatory disease: comparison with laparoscopy and US

PURPOSE

To assess the value of magnetic resonance (MR) imaging in the diagnosis of pelvic inflammatory disease (PID) and to compare MR imaging with transvaginal ultrasonography (US) and laparoscopy.

MATERIALS AND METHODS

Thirty consecutive patients hospitalized because they were clinically suspected of having PID underwent transvaginal US and T1-weighted spin-echo, T2-weighted turbo spin-echo, and inversion-recovery MR imaging at 1.5 T. All patients underwent laparoscopy after MR imaging.

RESULTS

PID was laparoscopically proved in 21 (70%) patients. The MR imaging diagnosis agreed with that obtained with laparoscopy in 20 (95%) of the 21 patients with PID. The imaging findings for PID were as follows: fluid-filled tube, pyosalpinx, tubo-ovarian abscess, or polycystic-like ovaries and free pelvic fluid. Findings at transvaginal US agreed with those at laparoscopy in 17 (81%) of the 21 patients with PID. The sensitivity of MR imaging in the diagnosis of PID was 95%, the specificity was 89%, and the overall accuracy was 93%. For transvaginal US, the corresponding values were 81%, 78%, and 80%.

CONCLUSION

MR imaging is more accurate than transvaginal US in the diagnosis of PID and provides information about the differential diagnosis of PID. MR imaging may reduce the need for diagnostic laparoscopy.

MRI of pelvic masses: efficacy of the rectal superparamagnetic contrast agent Ferumoxsil

The purpose of this study was to determine the potential value of rectally administered Ferumoxsil for pelvic MRI. Twenty patients with suspected rectosigmoid and ovarian tumors were prospectively examined before and after rectal administration of 300 to 600 ml of the superparamagnetic contrast agent Ferumoxsil. Imaging parameters (1.5-T system, phased-array coil, transverse T1-weighted spin echo (SE) and T2-weighted turbo-SE sequences, 6-mm slice thickness, 350-mm field of view [FOV], 512 x 512 matrix) were kept constant. Images were evaluated for tumor presence, lymphadenopathy, bowel involvement, and peritoneal implants. Precontrast and postcontrast studies were rated for bowel delineation, lesion/organ-to-bowel differentiation, presence of artifacts, and confidence of diagnosis. Delineation of rectum and sigmoid colon (P < .001) as well as separation of bowel and vagina, uterus/adnexa, dome of the urinary bladder, lymph nodes, and vessels improved significantly (P < .01) on both T1-weighted and T2-weighted postcontrast sequences. The rectal contrast agent did not increase the level of artifacts. Changes in diagnosis in 7 of 20 patients were mainly due to identification of colorectal tumors or bowel involvement on postcontrast images. The readers' diagnostic confidence was significantly higher on contrast-enhanced than on unenhanced studies (93 +/- 6.4% vs 68 +/- 25.2%). Rectal application of Ferumoxsil improves lesion/organ-to-bowel delineation and overall diagnostic confidence in pelvic MRI.

MR imaging contrast agents--what's in a name?

The purpose of this brief review is to reduce the confusion surrounding the nomenclature of MRI contrast agents. There are several different categories of contrast agents for potential use in human diagnosis and several alternative names for each contrast agent, an array of choices that actually changes over time. This review describes the general process by which these various agents are named, presents one general categorization by which these agents can be considered, and provides a concise table to which readers can refer to identify the proper name to use for each of the agents that has thus far been administered to humans.