Mapping of Proton Relaxation Near Superparamagnetic Iron Oxide Particle–Loaded Polymer Threads for Magnetic Susceptibility Difference Quantification:

Magnetic resonance visualization of iron-loaded meshes in patients with pain after inguinal hernia repair

PURPOSE

Chronic post-operative inguinal pain (CPIP) is defined as pain lasting more than 3 months and the incidence is less than 4% after laparoscopic hernia repair. CPIP can have several causes. In this study, we aimed to show that 3D-iron loaded mesh preparations are useful in radiological evaluation of post-operative complications, especially patients with chronic pain and the mesh status of operated inguinal hernia cases.

METHODS

A total of 450 cases who had been operated for inguinal hernia with 3D-iron loaded mesh and who had ongoing pain at the post-operative period were included in this study. MRI (Magnetic Resonance Imaging) was performed at the post-operative 90th day of the seven symptomatic (groin pain, limitation of movement) cases which were operated using a 3D-iron loaded mesh, 10 × 15 cm in size, (DynaMeshEndolap visible with 25% MRI-visible filaments, FEG TextiltechnikmbH, Aachen, Germany) for inguinal hernia repair to evaluate mesh status, localization, and local complications. Gradient echo sequences in the sagittal, axial, and coronal sections on MRI were discussed by two radiologists. Mesh localizations, their relationship with surrounding structures and their complications related with mesh were evaluated by two radiologists (D.Y, D.E.T.Ş).

RESULTS

No significant radiological findings related to defined anatomical structures were found in the MRI images of the study group. The dimensions measured on the sagittal, axial and coronal images were correlated with original mesh sizes and no significant shrinkage was detected.

CONCLUSION

Mesh position and deformation as shrinkage can be the mesh-related cause of pain. The incidence of CPIP in our patients is less than 2%. 3D-iron loaded meshes were monitored with MRI in CPIP patients and there was no mesh-related changes found in our study. The use of MRI-visible meshes will most likely help us to monitor mesh preparations and show potential time-dependent changes in mesh characteristics and consequent complications. In case of doubtful clinical postoperative hernia recurrence or chronic groin pain, mesh position can be identified by MRI and unnecessary surgical intervention can be avoided.

In vivo visualization of polymer-based mesh implants using conventional magnetic resonance imaging and positive-contrast susceptibility imaging

PURPOSE

Polymer-based textile meshes for abdominal hernia treatment are invisible by conventional imaging methods, including magnetic resonance imaging (MRI). Integration of iron particles in the mesh base material allows MRI visualization of meshes. Positive-contrast susceptibility imaging (PCSI) was implemented to separate susceptibility-induced voids from proton-deficient voids. The purpose of this study was to compare PCSI with conventional gradient echo and turbo spin echo (TSE) sequences for the in vivo assessment of superparamagnetic iron oxide particle-loaded surgical meshes in an animal model.

METHODS AND MATERIALS

Iron-loaded polymer meshes were implanted into the abdominal wall of 10 rabbits. At days 1, 30, and 90 after surgery, conventional gradient echo, TSE, and PCSI were performed at 1.5 T in the sagittal and axial planes. Images were scored by 2 radiologists with respect to mesh visibility, delineation of the surrounding tissue, differentiation from other structures, and overall diagnostic use, on a 4-point scale ranging from 1 (insufficient) to 4 (excellent). The results were compared using Wilcoxon signed-rank tests. The mesh shape, possible deformation or fracture, and possible mesh migration were evaluated on the different pulse sequences and compared with the results at surgery and autopsy.

RESULTS

The iron-loaded meshes appeared as hypointense signal voids on gradient echo sequences, as a hyperintense line on PCSI, and as a very thin dark line on TSE images. In all animals, a precise depiction of the mesh location and its spatial configuration and integrity was possible by MRI and confirmed by surgical and autopsy results. In all 4 categories and at all 3 time points of imaging, image quality scores were significantly higher for gradient echo imaging (range, 3.60-3.80) compared with PCSI (range, 3.12-3.42) and TSE (range, 1.64-1.89). At day 90, the image quality ratings of gradient echo and PCSI were comparable. In 2 cases, the complete delineation of mesh borders was impossible because of signal voids of adjacent anatomical structures, whereas PCSI helped achieve this differentiation.

CONCLUSION

In this rabbit model of iron-loaded implanted abdominal meshes, standard gradient echo imaging was best suitable to assess implant location, integrity, and configuration. In 2 of 10 animals, PCSI helped achieve a complete delineation of mesh borders.

A historical overview of magnetic resonance imaging, focusing on technological innovations

Magnetic resonance imaging (MRI) has now been used clinically for more than 30 years. Today, MRI serves as the primary diagnostic modality for many clinical problems. In this article, historical developments in the field of MRI will be discussed with a focus on technological innovations. Topics include the initial discoveries in nuclear magnetic resonance that allowed for the advent of MRI as well as the development of whole-body, high field strength, and open MRI systems. Dedicated imaging coils, basic pulse sequences, contrast-enhanced, and functional imaging techniques will also be discussed in a historical context. This article describes important technological innovations in the field of MRI, together with their clinical applicability today, providing critical insights into future developments.