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Článek

Two-parametric prescan calibration of gradient-induced sampling errors for rosette MRI

Latta, Peter
Autor Latta, Peter ORCID Central European Institute of Technology, Masaryk University, Brno, Czech Republic
Jiřík, Radovan
Autor Jiřík, Radovan ORCID Institute of Scientific Instruments of the Czech Academy of Sciences, Brno, Czech Republic
Vitouš, Jiří
Autor Vitouš, Jiří ORCID Institute of Scientific Instruments of the Czech Academy of Sciences, Brno, Czech Republic
Macíček, Ondřej
Autor Macíček, Ondřej ORCID Institute of Scientific Instruments of the Czech Academy of Sciences, Brno, Czech Republic
Vojtíšek, Lubomír
Autor Vojtíšek, Lubomír Central European Institute of Technology, Masaryk University, Brno, Czech Republic
Rektor, Ivan
Autor Rektor, Ivan Central European Institute of Technology, Masaryk University, Brno, Czech Republic
Standara, Michal
Autor Standara, Michal Department of Radiology, Masaryk Memorial Cancer Institute, Brno, Czech Republic
Křístek, Jan
Autor Křístek, Jan Department of Radiology, Masaryk Memorial Cancer Institute, Brno, Czech Republic
Starčuk, Zenon
Autor Autorita ORCID Institute of Scientific Instruments of the Czech Academy of Sciences, Brno, Czech Republic

Magnetic resonance in medicine. 2025 ; 93 (3) : 1285-1297. [pub] 20241022

Magn Reson Med
ISSN 1522-2594
Medvik
Zdroj

PURPOSE: The aim of this study was to develop a simple, robust, and easy-to-use calibration procedure for correcting misalignments in rosette MRI k-space sampling, with the objective of producing images with minimal artifacts. METHODS: Quick automatic calibration scans were proposed for the beginning of the measurement to collect information on the time course of the rosette acquisition trajectory. A two-parameter model was devised to match the measured time-varying readout gradient delays and approximate the actual rosette sampling trajectory. The proposed calibration approach was implemented, and performance assessment was conducted on both phantoms and human subjects. RESULTS: The fidelity of phantom and in vivo images exhibited significant improvement compared with uncorrected rosette data. The two-parameter calibration approach also demonstrated enhanced precision and reliability, as evidenced by quantitative T2*$$ {\mathrm{T}}_2^{\ast } $$ relaxometry analyses. CONCLUSION: Adequate correction of data sampling is a crucial step in rosette MRI. The presented experimental results underscore the robustness, ease of implementation, and suitability for routine experimental use of the proposed two-parameter rosette trajectory calibration approach.

MeSH
algoritmy * MeSH
artefakty * MeSH
fantomy radiodiagnostické * MeSH
kalibrace MeSH
lidé MeSH
magnetická rezonanční tomografie * metody MeSH
mozek diagnostické zobrazování MeSH
počítačové zpracování obrazu * metody MeSH
reprodukovatelnost výsledků MeSH
Check Tag
lidé MeSH
Publikační typ
časopisecké články MeSH

Článek

Denoising of dual-VENC PC-MRI with large high/low VENC ratios

Magnetic resonance in medicine. 2025 ; 93 (1) : 353-368. [pub] 20240918

Magn Reson Med
ISSN 1522-2594
Medvik
Zdroj

PURPOSE: Dual velocity encoding PC-MRI can produce spurious artifacts when using high ratios of velocity encoding values (VENCs), limiting its ability to generate high-quality images across a wide range of encoding velocities. This study aims to propose and compare dual-VENC correction methods for such artifacts. THEORY AND METHODS: Two denoising approaches based on spatiotemporal regularization are proposed and compared with a state-of-the-art method based on sign correction. Accuracy is assessed using simulated data from an aorta and brain aneurysm, as well as 8 two-dimensional (2D) PC-MRI ascending aorta datasets. Two temporal resolutions (30,60) ms and noise levels (9,12) dB are considered, with noise added to the complex magnetization. The error is evaluated with respect to the noise-free measurement in the synthetic case and to the unwrapped image without additional noise in the volunteer datasets. RESULTS: In all studied cases, the proposed methods are more accurate than the Sign Correction technique. Using simulated 2D+T data from the aorta (60 ms, 9 dB), the Dual-VENC (DV) error 0.82±0.07$$ 0.82\pm 0.07 $$ is reduced to: 0.66±0.04$$ 0.66\pm 0.04 $$ (Sign Correction); 0.34±0.04$$ 0.34\pm 0.04 $$ and 0.32±0.04$$ 0.32\pm 0.04 $$ (proposed techniques). The methods are found to be significantly different (p-value <0.05$$ <0.05 $$ ). Importantly, brain aneurysm data revealed that the Sign Correction method is not suitable, as it increases error when the flow is not unidirectional. All three methods improve the accuracy of in vivo data. CONCLUSION: The newly proposed methods outperform the Sign Correction method in improving dual-VENC PC-MRI images. Among them, the approach based on temporal differences has shown the highest accuracy.

MeSH
algoritmy * MeSH
aorta * diagnostické zobrazování MeSH
artefakty * MeSH
fantomy radiodiagnostické MeSH
interpretace obrazu počítačem metody MeSH
intrakraniální aneurysma diagnostické zobrazování MeSH
lidé MeSH
magnetická rezonanční tomografie * metody MeSH
mozek diagnostické zobrazování MeSH
počítačová simulace MeSH
počítačové zpracování obrazu * metody MeSH
poměr signál - šum * MeSH
reprodukovatelnost výsledků MeSH
Check Tag
lidé MeSH
Publikační typ
časopisecké články MeSH

Článek

Refining Treatment Planning in STereotactic Arrhythmia Radioablation: Benchmark Results and Consensus Statement From the STOPSTORM.eu Consortium

International journal of radiation oncology, biology, physics. 2025 ; 121 (1) : 218-229. [pub] 20240808

Int J Radiat Oncol Biol Phys
ISSN 1879-355X
Medvik
Zdroj

PURPOSE: STereotactic Arrhythmia Radioablation (STAR) showed promising results in patients with refractory ventricular tachycardia. However, clinical data are scarce and heterogeneous. The STOPSTORM.eu consortium was established to investigate and harmonize STAR in Europe. The primary goal of this benchmark study was to investigate current treatment planning practice within the STOPSTORM project as a baseline for future harmonization. METHODS AND MATERIALS: Planning target volumes (PTVs) overlapping extracardiac organs-at-risk and/or cardiac substructures were generated for 3 STAR cases. Participating centers were asked to create single-fraction treatment plans with 25 Gy dose prescriptions based on in-house clinical practice. All treatment plans were reviewed by an expert panel and quantitative crowd knowledge-based analysis was performed with independent software using descriptive statistics for International Commission on Radiation Units and Measurements report 91 relevant parameters and crowd dose-volume histograms. Thereafter, treatment planning consensus statements were established using a dual-stage voting process. RESULTS: Twenty centers submitted 67 treatment plans for this study. In most plans (75%) intensity modulated arc therapy with 6 MV flattening filter free beams was used. Dose prescription was mainly based on PTV D95% (49%) or D96%-100% (19%). Many participants preferred to spare close extracardiac organs-at-risk (75%) and cardiac substructures (50%) by PTV coverage reduction. PTV D0.035cm3 ranged from 25.5 to 34.6 Gy, demonstrating a large variety of dose inhomogeneity. Estimated treatment times without motion compensation or setup ranged from 2 to 80 minutes. For the consensus statements, a strong agreement was reached for beam technique planning, dose calculation, prescription methods, and trade-offs between target and extracardiac critical structures. No agreement was reached on cardiac substructure dose limitations and on desired dose inhomogeneity in the target. CONCLUSIONS: This STOPSTORM multicenter treatment planning benchmark study not only showed strong agreement on several aspects of STAR treatment planning, but also revealed disagreement on others. To standardize and harmonize STAR in the future, consensus statements were established; however, clinical data are urgently needed for actionable guidelines for treatment planning.

MeSH
benchmarking * MeSH
celková dávka radioterapie MeSH
komorová tachykardie chirurgie radioterapie MeSH
konsensus * MeSH
kritické orgány * účinky záření MeSH
lidé MeSH
plánování radioterapie pomocí počítače * normy metody MeSH
radiochirurgie * normy metody MeSH
radioterapie s modulovanou intenzitou metody normy MeSH
srdce účinky záření MeSH
srdeční arytmie MeSH
Check Tag
lidé MeSH
Publikační typ
časopisecké články MeSH
multicentrická studie MeSH
Geografické názvy
Evropa MeSH

Článek

Imiquimod nanocrystal-loaded dissolving microneedles prepared by DLP printing

Drug delivery and translational research. 2025 ; 15 (1) : 158-170. [pub] 20240312

Drug Deliv Transl Res
ISSN 2190-3948
Medvik
Zdroj

The utilization of 3D printing- digital light processing (DLP) technique, for the direct fabrication of microneedles encounters the problem of drug solubility in printing resin, especially if it is predominantly composed of water. The possible solution how to ensure ideal belonging of drug and water-based printing resin is its pre-formulation in nanosuspension such as nanocrystals. This study investigates the feasibility of this approach on a resin containing nanocrystals of imiquimod (IMQ), an active used in (pre)cancerous skin conditions, well known for its problematic solubility and bioavailability. The resin blend of polyethylene glycol diacrylate and N-vinylpyrrolidone, and lithium phenyl-2,4,6-trimethylbenzoylphosphinate as a photoinitiator, was used, mixed with IMQ nanocrystals in water. The final microneedle-patches had 36 cylindrical microneedles arranged in a square grid, measuring approximately 600 μm in height and 500 μm in diameter. They contained 5wt% IMQ, which is equivalent to a commercially available cream. The homogeneity of IMQ distribution in the matrix was higher for nanocrystals compared to usual crystalline form. The release of IMQ from the patches was determined ex vivo in natural skin and revealed a 48% increase in efficacy for nanocrystal formulations compared to the crystalline form of IMQ.