• Book : 226()
• Pub. Date : 2025
• Page : pp.112278
• Keyword :

• Book : 226()
• Pub. Date : 2025
• Page : pp.112281
• Keyword :

• Book : 239()
• Pub. Date : 2025
• Page : pp.115507
• Keyword :

• Book : 242(1)
• Pub. Date : 2025
• Page : pp.115890
• Keyword :

Abstract

In this paper, both semi-analytical method and numerical simulation is applied to investigate the hydrodynamic behavior of large arrays of point-absorber wave energy converters (WECs). To analyze wave interactions among multiple WECs within an array, a semi-analytical model is developed based on the potential flow theory and the matched eigen-function expansions method. The fluid domain is divided into two kinds of regions: interior regions underneath the cylinders and an exterior region surrounding all the cylinders. The matched eigen-function expansions method is employed to solve the radiation potential problem in each domain, and the hydrodynamic coefficients and motion response of the cylinders in the array are evaluated. To validate the accuracy of the semi-analytical method, wamit is adopted to simulate the wave energy park numerically and compared with the results by the semi-analytical model. The hydrodynamic characteristics and power absorption performance of the WECs within the wave energy park are analyzed. The power performance of a wave energy park is studied as functions of layout geometry, incident wave direction, and separation distance between WECs respectively. Finally, multi-objective particle swarm optimization based on a surrogate model is used to optimize the layout of wave energy array.

• Book : 147(4)
• Pub. Date : 2025
• Page : pp.042001
• Keyword :

Abstract

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 is reduced to: (Sign Correction); and (proposed techniques). The methods are found to be significantly different (p‐value ). 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.

• Book : 93(1)
• Pub. Date : 2025
• Page : pp.353-368
• Keyword :

Abstract

Purpose

Radiotherapy treatment planning (RTP) using MR has been used increasingly for the abdominal site. Multiple contrast weightings and motion‐resolved imaging are desired for accurate delineation of the target and various organs‐at‐risk and patient‐tailored planning. Current MR protocols achieve these through multiple scans with distinct contrast and variable respiratory motion management strategies and acquisition parameters, leading to a complex and inaccurate planning process. This study presents a standalone MR Multitasking (MT)-based technique to produce volumetric, motion‐resolved, multicontrast images for abdominal radiotherapy treatment planning.

Methods

The MT technique resolves motion and provides a wide range of contrast weightings by repeating a magnetization‐prepared (saturation recovery and T2 preparations) spoiled gradient‐echo readout series and adopting the MT image reconstruction framework. The performance of the technique was assessed through digital phantom simulations and in vivo studies of both healthy volunteers and patients with liver tumors.

Results

In the digital phantom study, the MT technique presented structural details and motion in excellent agreement with the digital ground truth. The in vivo studies showed that the motion range was highly correlated (R² = 0.82) between MT and 2D cine imaging. MT allowed for a flexible contrast‐weighting selection for better visualization. Initial clinical testing with interobserver analysis demonstrated acceptable target delineation quality (Dice coefficient = 0.85 ± 0.05, Hausdorff distance = 3.3 ± 0.72 mm).

Conclusion

The developed MT‐based, abdomen‐dedicated technique is capable of providing motion‐resolved, multicontrast volumetric images in a single scan, which may facilitate abdominal radiotherapy treatment planning.

• Book : 93(1)
• Pub. Date : 2025
• Page : pp.108-120
• Keyword :

• Book : 227()
• Pub. Date : 2025
• Page : pp.109706
• Keyword :

• Book : 226()
• Pub. Date : 2025
• Page : pp.112231
• Keyword :

• Book : 226()
• Pub. Date : 2025
• Page : pp.112244
• Keyword :