Effect of magnetic resonance imaging on implantable eyelid weights

nanoGold and µGold inhibit autoimmune inflammation: a review

The newest data on metallic gold have placed the noble metal central in the fight for the safe treatment of autoimmune inflammation. There are two different ways to use gold for the treatment of inflammation: gold microparticles > 20 µm and gold nanoparticles. The injection of gold microparticles (µGold) is a purely local therapy. µGold particles stay put where injected, and gold ions released from them are relatively few and taken up by cells within a sphere of only a few millimeters in diameter from their origin particles. The macrophage-induced release of gold ions may continue for years. Injection of gold nanoparticles (nanoGold), on the other hand, is spread throughout the whole body, and the bio-released gold ions, therefore, affect multitudes of cells all over the body, as when using gold-containing drugs such as Myocrisin. Since macrophages and other phagocytotic cells take up and transport nanoGold and remove it after a short period, repeated treatment is necessary. This review describes the details of the cellular mechanisms that lead to the bio-release of gold ions in µGold and nanoGold.

Imaging of the Postoperative Eye and Orbit

There is a plethora of surgical procedures that are performed in the eye and orbit. The consequences of these procedures can often be observed on diagnostic imaging through the presence of various implants and altered anatomy. The expected postoperative changes in the eye and orbit, the impact of implants on image quality and safety, and potential associated complications are reviewed in this article. Conventional computed tomography and MR imaging scans are useful for the postoperative assessment of the eye and orbit. The computed tomography and MR imaging findings related to the postoperative eye and orbit are reviewed in this article.

Facial reanimation procedures depicted on radiologic imaging

Various facial reanimation procedures can be performed for treating patients with chronic facial nerve paralysis. The radiologic imaging features of static and dynamic techniques are reviewed in this article with clinical correlation, including brow lift, eyelid weights and springs, gracilis free flaps, fascia lata grafts, temporalis flaps, and Gore-Tex suspension slings. Although the anatomic alterations resulting from facial reanimation surgery may not necessarily be the focus of the imaging examination, it is important to recognize such changes and be familiar with MR imaging compatibility of the associated implanted materials. Furthermore, imaging is sometimes used to specifically evaluate the postoperative results, such as vessel patency following free gracilis transfer.

Effect of 7.0 Tesla MRI on Upper Eyelid Implants

To ensure the MRI compatibility of various eyelid implants in high-field MRI, 3 eyelid weights made of pure gold (99.99%), pure platinum (99.95%), and a platinum (97%)/iridium (3%) alloy were examined in vitro. Temperature changes, position changes, and imaging artifacts of the different implants were determined in a small-bore 7.0 Tesla MRI system. The 7.0 Tesla MRI system demonstrated that none of the eyelid implants carried a risk of heating or dislocation; therefore, these implants are MRI compatible up to a magnetic field strength of 7.0 Tesla.

Einfluss der Magnetresonanztomographie auf Oberlidimplantate

BACKGROUND

For the therapy of lagophthalmos in facial palsy, gold (99.99%), platinum (99.95%) and platinum/iridium (97%/3%) alloy weights are implanted into the upper eyelid. Investigations on the MRI compatibility of the different eyelid implants with 1.5 and 3.0 Tesla-MRT-systems, which are often used for the diagnosis of head and neck tumours, are still missing.

METHODS

Three different eyelid implants made of pure gold, pure platinum and a platinum/iridium alloy were tested in vitro. As parameters, temperature changes, movements of the implants and picture artefacts of the different implants were determined using a 1.5 and 3.0 Tesla MR system. The deflection forces of the implants were evaluated by thread test, lying in a Petri dish and floating in a water bath.

RESULTS

No rise in temperature was recorded in any implant. On the water surface, all three implants changed their positions and floated towards the magnetic field. The velocity of the implants increased in the 3.0 Tesla system. Increasing the frictional resistance by lying the implants in a Petri dish, there was no movement in the 1.5 or 3.0 Tesla systems. In addition, no movement of the implants could be observed in the thread test. All implants made few artefacts, with gold showing the least artefacts.

CONCLUSION

MR imaging at 1.5 or 3.0 Tesla may be performed safely for warming up or dislocation of the implant in patients with eyelid implants made of pure gold, pure platinum or a platinum/iridium alloy.

Safety issues in magnetic resonance imaging

Although generally considered safe, magnetic resonance imaging (MRI) has a number of safety issues, including the effects of high magnetic fields and radiofrequency pulses on the body, and on implanted devices, the side effects of contrast agents, toxicity during pregnancy, claustrophobia, and hearing loss.

The AAPM/RSNA physics tutorial for residents. MR imaging safety considerations. Radiological Society of North America

Experience and research over the past decade have demonstrated that diagnostic magnetic resonance (MR) imaging is a biologically safe imaging modality. Specifically, there is currently no convincing evidence that there is any long-term or irreversible biologic effects associated with the radiation and magnetic fields used in MR imaging, specifically radio-frequency (RF) radiation, static magnetic fields, and time-varying gradient fields. However, numerous hazards of MR imaging do exist that can cause severe injuries or even death. These hazards are primarily the result of (a) strong magnetic fields and the strong force that they exert on ferromagnetic objects brought into their influence, including interference with electronic devices such as pacemakers and other implanted electronic devices, and (b) RF burns resulting from inadvertently induced currents in conductive loops placed on the patient's skin surface (eg, electrocardiographic leads and other monitoring devices). Other potential concerns are peripheral nerve stimulation resulting from rapidly switched gradients and auditory noise levels. Establishing a complete and coordinated educational program for all MR imaging facility personnel and conducting effective screening and preparation of patients scheduled for MR imaging procedures are essential to avoid accidents and RF burns and to maintain a safe MR imaging facility.

Early eyelid rehabilitation in facial nerve paralysis

Upper-lid gold-weight insertions and lower-lid-shortening procedures are standard surgical techniques used to restore eyelid function and protect the cornea in patients with facial nerve paralysis. Different opinions exist in the literature regarding the correct timing and the morbidity of these interventions. The retrospective analysis of 45 patients over a 5-year period revealed extrusion of the gold weight in one (2.2%) patient and delayed infections in three (6.6%). Sixty percent of all gold-weight insertions were performed within 4 weeks after the onset of facial nerve paralysis. We strongly favor gold-weight insertion, often combined with lower-lid-shortening procedures, as a simple, reliable, reversible, and successful technique for early rehabilitation of the paralyzed eyelid. Using these guidelines, we have markedly reduced the need for tarsorrhaphies.