MRI of Implantation Sites Using Parallel Transmission of an Optimized Radiofrequency Excitation Vector

Abstract

Postoperative care of orthopedic implants is aided by imaging to assess the healing process and the implant status. MRI of implantation sites might be compromised by radiofrequency (RF) heating and RF transmission field (B1+) inhomogeneities induced by electrically conducting implants. This study examines the applicability of safe and B1+-distortion-free MRI of implantation sites using optimized parallel RF field transmission (pTx) based on a multi-objective genetic algorithm (GA). Electromagnetic field simulations were performed for eight eight-channel RF array configurations (f = 297.2 MHz), and the most efficient array was manufactured for phantom experiments at 7.0 T. Circular polarization (CP) and orthogonal projection (OP) algorithms were applied for benchmarking the GA-based shimming. B1+ mapping and MR thermometry and imaging were performed using phantoms mimicking muscle containing conductive implants. The local SAR10g of the entire phantom in GA was 12% and 43.8% less than the CP and OP, respectively. Experimental temperature mapping using the CP yielded ΔT = 2.5–3.0 K, whereas the GA induced no extra heating. GA-based shimming eliminated B1+ artefacts at implantation sites and enabled uniform gradient-echo MRI. To conclude, parallel RF transmission with GA-based excitation vectors provides a technical foundation en route to safe and B1+-distortion-free MRI of implantation sites.

Image-Guided Surgical and Pharmacotherapeutic Routines as Part of Diligent Medical Treatment

“…Recent work considering RDD has been reported in the literature; see e These regard USI-guided DD enhancement, microbubble-mediated USI DD, m patches for DD, DD to cancer cells, spatial, temporal, and dose control of DD, cles-based strategies to improve the delivery of therapeutic RNA in precision nanoparticle-based delivery systems in pancreatic cancer, and nano-drug deliv for cancer. Contributions on implanted technologies and their concerns could e.g., in [51][52][53][54][55][56][57][58][59]. These concern artefacts of biodegradable magnesium-based im sessment of implant-related pain and dysfunction, cochlear implant positioni imaging quality, adverse local tissue reactions near metal implants after total plasty, metal artefact reduction sequences for a piezoelectric bone conductio image quality and artifact reduction of a cochlear implant, MRI in patients w implantable electronic devices, and MRI artifacts caused by auditory implants treatment structures might manage confined conduct MI-imbedded equipm structures employ RDD for nearby tissue containing a specified area.…”