Multi-Echo EPI

1 Basic principles

1.1 Principle of Multi-Echo EPI

The basic timing scheme of Multi-Echo EPI is shown in Figure 1. It is based on the original EPI sequence proposed by Mansfield (1). After a single RF-excitation, n complete EPI images are acquired in a single shot. The phase gradient is rewound to the original starting position after each echo-image to ensure identical k-space trajectories for all echo-images (2).

RF

GS

GR

GP

echo-image loop

n

Figure 1 – Basic timing of the Multi-Echo EPI sequence. The shaded gradient in phase encoding direction ensures identical k-space trajectories for all echo-images.

The resulting echo-images have different increasing echo times and thus T2*- weighting. The single echo-images correspond to standard gradient echo EPI images with the same echo time.

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Siemens 4A21 manual Basic principles, Principle of Multi-Echo EPI

4A21 specifications

The Siemens 4A21 is an advanced versatile automation controller that reflects the company's commitment to innovation and efficiency in industrial automation. Designed for a variety of applications, the 4A21 provides users with a powerful platform for integrating various automation processes seamlessly.

One of the main features of the Siemens 4A21 is its high performance and speed. The controller is equipped with a robust processing unit that can handle complex calculations and execute multiple tasks simultaneously. This capability is essential for time-sensitive applications where delays can lead to operational inefficiencies.

The 4A21 incorporates a flexible communication architecture that supports multiple protocols, including PROFINET, Ethernet/IP, and Modbus TCP. This feature enables the controller to communicate with a wide range of devices and systems, allowing for easier integration of existing equipment and facilitating future expansions. Additionally, the built-in security measures ensure that data remains protected against unauthorized access, making it suitable for industries that require stringent compliance to safety standards.

Another standout characteristic of the Siemens 4A21 is its modular design, which provides users with the flexibility to customize their systems according to specific requirements. This design allows for straightforward upgrades, enabling businesses to adapt to changing technologies or production demands without having to overhaul their entire automation infrastructure.

The controller also supports a variety of I/O modules, which can be tailored to accommodate different input and output needs. This configurability is crucial for applications across various sectors, from manufacturing to process automation. The 4A21 is also optimized for real-time data processing, which enhances its ability to monitor and control processes accurately and efficiently.

A significant aspect of the Siemens 4A21 is its user-friendly interface, featuring intuitive programming tools that simplify the development of automation solutions. Programmers can take advantage of Siemens' TIA Portal, which allows for seamless project creation and management, reducing the time required for system implementation.

Overall, the Siemens 4A21 is a cutting-edge automation controller that combines high performance, flexibility, and a comprehensive communication framework. Its ability to integrate with existing systems and its user-friendly programming capabilities make it an excellent choice for industries looking to enhance their automation processes. This versatility ensures that the 4A21 remains a valuable tool in the ever-evolving landscape of industrial automation.