Search Results (3)

Introduction: An efficient pipeline for rosette trajectory magnetic resonance imaging reconstruction is proposed, combining the inverse Fourier transform with a vision transformer (ViT) network enhanced with a convolutional layer. This method addresses the challenges of reconstructing high-quality images from non-Cartesian data by leveraging the ViT’s ability to handle complex spatial dependencies without extensive preprocessing. Materials and Methods: The inverse fast Fourier transform provides a robust initial approximation, which is refined by the ViT network to produce high-fidelity images. Results and Discussion: This approach outperforms established deep learning techniques for normalized root mean squared error, peak signal-to-noise ratio, and entropy-based image quality scores; offers better runtime performance; and remains competitive with respect to other metrics. Full article

Background: Stereotactic biopsy of posterior fossa lesions, which are often inoperable, enables a safe trajectory and provides tissue samples for accurate diagnosis, which is crucial for correct treatment since the latest World Health Organization Classification of Tumors of the Central Nervous System from 2021 places immense emphasis on molecular diagnostics. Stereotactic biopsy using the Leksell Vantage headframe is, due to its rigid design, extremely accurate, but stiffer, making the procedure more challenging and the learning curve steeper. Methods: This retrospective analysis demonstrates the introduction of the new Leksell Vantage headframe in day-to-day practice at the University Medical Center in Maribor, Slovenia, in demanding procedures of posterior fossa biopsies, and also provides a review of the literature available on the topic with emphasis on the technical aspect of posterior fossa biopsy using the Leksell Vantage headframe in adults. Results: In the observed series of three patients with posterior fossa lesions, all biopsies were representative, despite tissue samples being small, providing conclusive histopathologic reports (glioblastoma, rosette-forming glioneuronal tumor and metastasis of melanoma) with additional molecular diagnostics. After the initial biopsy case, the preoperative planning times and procedure times were shortened as we learnt about the importance of a tailored approach from the first case. In all cases, the biopsy was performed under local anesthesia with patients being awake throughout surgery. Conclusions: The rigid Leksell Vantage headframe makes access to the posterior fossa tougher when compared to its predecessors. However, the procedure is very accurate but requires precise preoperative planning and a customized approach when placing the headframe. Full article

Background/Objectives: The increased SNR available at 7T combined with fast readout trajectories enables accelerated spectroscopic imaging acquisitions for clinical applications. In this report, we evaluate the performance of a Hadamard slice encoding strategy with a 2D rosette trajectory for multi-slice fast spectroscopic imaging at 7T. Methods: Moderate-TE (~40 ms) spin echo and J-refocused polarization transfer sequences were acquired with simultaneous Hadamard multi-slice excitations and rosette in-plane encoding. The moderate spin echo sequence, which targets singlet compounds (i.e., N-acetyl aspartate, creatine, and choline), uses cascaded multi-slice RF excitation pulses to minimize the chemical shift dispersion error. The J-refocused sequence targets coupled spin systems (i.e., glutamate and myo-inositol) using simultaneous multi-slice excitation to maintain the same TE across all slices. A modified Hadamard slice encoding strategy was used to decrease the peak RF pulse amplitude of the simultaneous multi-slice excitation pulse for the J-refocused acquisition. Results: The accuracy of multi-slice and single-slice rosette spectroscopic imaging (RSI) is comparable to conventional Cartesian-encoded spectroscopic imaging (CSI). Spectral analyses for the J-refocused studies of glutamate and myo-inositol show that the Cramer Rao lower bounds are not significantly different between the fast RSI and conventional CSI studies. Linear regressions of creatine/N-acetyl aspartate and glutamate/N-acetyl aspartate with tissue gray matter content are consistent with literature values. Conclusions: With minimal gradient demands and fast acquisition times, the 2.2 min to 9 min for single- to four-slice RSI acquisitions are well tolerated by healthy subjects and tumor patients, and show results that are consistent with clinical outcomes. Full article