Planning And Positioning In Mri Pdf Download

Planning and Positioning in MRI: A Guide for Beginners

Magnetic resonance imaging (MRI) is a powerful and versatile diagnostic tool that uses a strong magnetic field and radio waves to produce detailed images of the body's internal structures. MRI can be used to examine various organs, tissues, and systems, such as the brain, spine, joints, muscles, blood vessels, heart, and more. However, to obtain high-quality images that are accurate and informative, it is essential to plan and position the patient and the imaging coil correctly. This article will provide some basic tips and resources for planning and positioning in MRI.

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What is planning and positioning in MRI?

Planning and positioning in MRI refers to the process of selecting the appropriate imaging parameters, such as the field of view (FOV), slice thickness, matrix size, number of slices, and pulse sequence, as well as aligning the patient and the coil with the desired imaging plane. Planning and positioning are crucial for optimizing the image quality, reducing artifacts, covering the relevant anatomy, and minimizing scan time.

Why is planning and positioning important in MRI?

Planning and positioning are important in MRI for several reasons:

• They affect the signal-to-noise ratio (SNR), which is a measure of how well the signal from the tissue of interest can be distinguished from the background noise. A higher SNR means a clearer image with more details. The SNR depends on factors such as the coil size and type, the distance between the coil and the tissue, the FOV, the slice thickness, and the number of signal averages.

• They influence the contrast resolution, which is a measure of how well different tissues can be differentiated based on their signal intensity. The contrast resolution depends on factors such as the tissue relaxation properties, the pulse sequence, the repetition time (TR), the echo time (TE), and the inversion time (TI).

• They determine the spatial resolution, which is a measure of how well small structures can be resolved in the image. The spatial resolution depends on factors such as the matrix size, the FOV, the slice thickness, and the interpolation method.

• They prevent or reduce artifacts, which are distortions or errors in the image caused by various sources, such as patient motion, metal implants, magnetic field inhomogeneity, chemical shift, aliasing, cross-talk, eddy currents, and susceptibility effects.

• They ensure that the relevant anatomy is covered and displayed in an optimal orientation. This is important for accurate diagnosis and interpretation of pathological findings.

• They optimize the scan time by avoiding unnecessary slices or sequences. This is important for patient comfort and compliance, as well as for efficiency and cost-effectiveness.

How to plan and position in MRI?

The planning and positioning process in MRI can vary depending on the scanner type, software version, coil availability, protocol selection, patient condition, and clinical indication. However, some general steps can be followed:

• Select a suitable coil for the body region to be imaged. The coil should be as close as possible to the tissue of interest to maximize SNR. The coil should also match the shape and size of the anatomy to avoid gaps or overlaps.

• Position the patient on the scanner table according to the coil instructions. The patient should be comfortable and stable to avoid motion artifacts. The patient should also be aligned with the scanner's coordinate system (x-, y-, z-axes) to facilitate image planning.

• Perform a localizer scan to obtain scout images in three orthogonal planes (sagittal, coronal, axial). The localizer scan helps to identify anatomical landmarks and adjust FOV.

• Plan each imaging sequence by selecting or modifying parameters such as FOV, slice thickness, matrix size, number of slices, TR, TE, TI, flip angle (FA), bandwidth (BW), phase encoding direction (PED), fat suppression technique (FST), etc. The parameters should be chosen based on the desired image quality (SNR, contrast resolution, spatial resolution), scan time, and clinical indication.

• Position each imaging plane by adjusting its orientation, location, and angulation relative to the localizer images. The imaging plane should be parallel or perpendicular to the anatomical structures of interest to avoid partial volume effects and display them in a standard or optimal view.

• Review the planned images and sequences before starting the scan. Check for any errors, artifacts, or missing anatomy. Make any necessary corrections or additions.

Where to find more information and resources on planning and positioning in MRI?

There are many sources of information and resources on planning and positioning in MRI, such as textbooks, journals, websites, online courses, and workshops. Some examples are:

• by Anne Bright: This is a clinical manual that focuses on patient positioning and image planning for various body regions. It provides valuable insights into patient pathology, coil and patient considerations, imaging planes, anatomical image alignment, and routine and supplementary sequences.

• by Geisel School of Medicine at Dartmouth: This is a protocol book that covers the musculoskeletal system, including the spine, shoulder, elbow, wrist, hand, hip, knee, ankle, foot, and temporomandibular joint. It provides detailed instructions on coil selection, patient positioning, sequence parameters, imaging planes, and normal anatomy.

• by Muhammed Elmaoglu and Azim Celik: This is a handbook that presents a concise review of the physical principles underlying MRI, explaining MR physics, patient positioning, and protocols in an easy-to-read format. It covers various applications of MRI, such as neuroimaging, cardiac imaging, breast imaging, abdominal imaging, and more.

I hope this article has been helpful for you to learn more about planning and positioning in MRI. If you have any questions or feedback, please feel free to contact me.