Radiofrequency excitation-related 23 Na MRI signal loss in skeletal muscle, cartilage, and skin.

PURPOSE: To assess the sodium MRI signal loss resulting from typically used RF excitation pulses in human skeletal muscle, patellar cartilage, and skin. METHODS: A double flip-angle experiment was performed 3 times on the knees of 5 healthy volunteers with prescribed ω1 = γB1 of 1.67 kHz, 0.333 kHz, and 0.167 kHz. This was done to search for ω1 -dependent increased rates of sodium-23 central resonance flipping known to result from residual quadrupole splitting (ωQ ), as this flip-angle effect is associated with signal loss. This study facilitated in vivo regression of Gaussian-distributed residual quadrupole splitting SD (ωQ(SD) ) as well as T2fast and T2slow . Signal loss predicted from simulation was then compared with images acquired using 90° RF pulse lengths of 0.5 ms, 0.25 ms, and 0.15 ms. RESULTS: Sodium-23 central resonance flipping was significantly greater than prescribed (44% cartilage, 23% skin, 9% muscle) using ω1 = 0.167 kHz, but only 4% cartilage, 5% skin, and 2% muscle using ω1 = 1.67 kHz. Regression yielded ωQ(SD) = 420 ± 50 Hz for cartilage but no significant ωQ(SD) for skin or muscle. This points to rapid biexponential relaxation as the cause of the flip-angle effect for skin/muscle. The T2fast(60%) /T2slow(40%) values were 1.6 ± 0.8 ms/16.1 ± 2.5 ms for muscle, 2.7 ± 0.9 ms/18.4 ± 2.5 ms for cartilage, and 0.4 ± 0.1 ms/9.3 ± 1.7 ms for skin. Simulation predicted signal loss of 6% ± 3%, 3% ± 1%, and 2% ± 1% for muscle, 16% ± 3%, 6% ± 1%, and 3% ± 1% for cartilage, and 26% ± 7%, 15% ± 4%, and 10% ± 3% for skin when using 90° RF pulse lengths of 0.5 ms, 0.25 ms, and 0.15 ms, matching experiment. CONCLUSION: High-power (short) RF pulses are necessary to reduce excitation-related signal loss, particularly for sodium-23 imaging of cartilage and skin.

Predicted vs Observed Valve to Coronary Distance in Valve-in-Valve TAVR: A Computed Tomography Study.

BACKGROUND: Preprocedural computed tomography (CT) workup with assessment of virtual transcatheter heart valve-to-coronary ostia (VTC) distance and transcatheter heart valve-to-sinus (VTS) distances is recommended to assess the risk of coronary obstruction following valve-in-valve (ViV) transcatheter aortic valve replacement (TAVR). OBJECTIVES: The authors sought to investigate the agreement of predicted VTC and VTS distances and observed post-TAVR anatomy on CT and their relationship with transcatheter heart valve (THV) expansion and deployment conditions. METHODS: Fifty-one patients who underwent a balloon-expandable ViV procedure were included in this study. The expansion of the THV stent frame was evaluated at 4 levels: THV inflow, surgical heart valve (SHV) sewing ring, SHV outflow, and THV outflow. Assessment of the VTC/VTS distances was performed on the pre-TAVR CT, and THV-to-coronary ostia and THV-to-sinus distances were assessed on the post-TAVR CT. RESULTS: Following the ViV procedure, the THV stent frame flared toward the outflow but was generally underexpanded at all levels, particularly at the SHV sewing ring level. Postdilatation impacted the extent of THV expansion, resulting in greater expansion than nominal balloon filling at all 4 THV levels (P < 0.001). Observed THV-to-coronary ostia distances were systematically larger than predicted by the VTC distance (mean difference 1.25 ±1.28 mm) in patients with nominal balloon filling but systematically smaller in case of postdilatation (mean difference -0.45 ± 0.52 mm). A similar relationship was observed between VTS and THV-to-sinus distance measurements. CONCLUSIONS: With nominal balloon filling, VTC and VTS distances underestimate postprocedural distances due to THV frame underexpansion. However, postdilatation may lead to distances smaller than predicted due to THV overexpansion at the outflow level.

Late Balloon Valvuloplasty for Transcatheter Heart Valve Dysfunction.

BACKGROUND: Transcatheter heart valve (THV) dysfunction with an elevated gradient or paravalvular leak (PVL) may be documented late after THV implantation. Medical management, paravalvular plugs, redo THV replacement, or surgical valve replacement may be considered. However, late balloon dilatation is rarely utilized because of concerns about safety or lack of efficacy. OBJECTIVES: We aimed to evaluate the safety and efficacy of late dilatation in the management of THV dysfunction. METHODS: All patients who underwent late dilatation for symptomatic THV dysfunction at 2 institutions between 2016 and 2021 were identified. Baseline, procedural characteristics, and clinical and echocardiographic outcomes were documented. THV frame expansion was assessed by multislice computed tomography before and after late dilatation. RESULTS: Late dilatation was performed in 30 patients a median of 4.6 months (IQR: 2.3-11.0 months) after THV implantation in the aortic (n = 25; 83.3%), mitral (n = 2; 6.7%), tricuspid (n = 2; 6.7%) and pulmonary (n = 1; 3.3%) position. THV underexpansion was documented at baseline, and frame expansion substantially improved after late dilatation. The mean transvalvular gradient fell in all patients. For aortic THVs specifically, mean transaortic gradient fell from 25.4 ± 13.9 mm Hg to 10.8 ± 4.1 mm Hg; P < 0.001. PVL was reduced to ≤mild in all 11 patients with a previous >mild PVL. Embolic events, stroke, annular injury, and bioprosthetic leaflet injury were not observed. Symptomatic benefit was durable at 19.6 months (IQR: 14.8-36.1 months) follow-up. CONCLUSIONS: Balloon dilatation late after THV implantation appears feasible and safe in appropriately selected patients and may result in THV frame expansion resulting in improvements in hemodynamic performance and PVL.

Evaluation of facial symmetry after jaw reconstruction surgery.

The current study proposes a 3D objective method of evaluating facial symmetry after reconstructive surgery of orofacial structures. 3D models of the craniofacial and soft tissue surfaces were reflected about the mid-sagittal plane. The original model was aligned with the reflection and the best plane of symmetry was found. A deviation contour map quantified the areas of asymmetry and gave a global score of the asymmetry. The asymmetry scores were successfully obtained for 18 patients who had underwent reconstruction of lower face. The asymmetry values at craniofacial and soft tissue levels were moderately correlated (R2=0.39). Overall, the developed method effectively highlights areas of asymmetry and can help evaluate aesthetic outcomes of facial reconstruction surgery.

A 3D bioprinted hydrogel mesh loaded with all-trans retinoic acid for treatment of glioblastoma.

Treatment of glioblastoma (GBM), as the most lethal type of brain tumor, still remains a major challenge despite the various therapeutic approaches developed over the recent decades. GBM is considered as one of the most therapy-resistant human tumors. Treatment with temozolomide (TMZ) chemotherapy and radiotherapy in GBM patients has led to 30% of two-year survival rate (American Brain Tumor Association), representing a demanding field to develop more effective therapeutic strategies. This study presents a novel method for local delivery of all-trans retinoic acid (ATRA) for targeting GBM cells as a possible adjuvant therapeutic strategy for this disease. We have used 3D bioprinting to fabricate hydrogel meshes laden with ATRA-loaded polymeric particles. The ATRA-loaded meshes have been shown to facilitate a sustained release of ATRA with tunable release rate. Cell viability assay was used to demonstrate the ability of fabricated meshes in reducing cell growth in U-87 MG cell line. We later showed that the developed meshes induced apoptotic cell death in U-87 MG. Furthermore, the use of hydrogel for embedding the ATRA-loaded particles can facilitate the immobilization of the drug next to the tumor site. Our current innovative approach has shown the potential to open up new avenues for treatment of GBM, benefiting patients who suffer from this debilitating disease.