Learn the Basics of Planning and Positioning in MRI with this PDF Book
Planning and Positioning in MRI: A Guide for Beginners
Magnetic resonance imaging (MRI) is a powerful diagnostic tool that uses a strong magnetic field and radio waves to create detailed images of the internal structures of the body. MRI can provide information that other imaging modalities, such as X-ray, ultrasound or computed tomography (CT), cannot. For example, MRI can show soft tissue contrast, blood flow, functional activity, chemical composition, etc.
planning and positioning in mri pdf download
However, MRI is also a complex and challenging technique that requires careful planning and positioning of both the patient and the coil (the device that transmits and receives the radio signals). The quality of the MRI images depends largely on how well these factors are optimized. Poor planning or positioning can result in artifacts, noise, distortion, or incomplete coverage of the region of interest.
In this article, we will explain the basics of planning and positioning in MRI, including how different patient pathologies affect the appearance of MRI images, what considerations should be taken into account when positioning both the patient and the coil, what imaging protocols and sequences should be used for different body regions and pathologies, and how to optimize image quality and interpretation. We will also provide some examples of planning and positioning in MRI by body region, based on a popular clinical manual by Anne Bright .
Patient Pathology on MRI
One of the first steps in planning and positioning in MRI is to understand the patient pathology, or the disease or condition that affects the patient. Patient pathology can have a significant impact on the appearance of MRI images, as different pathologies can alter the signal intensity, contrast, or morphology of the tissues.
Some of the common indications for MRI scans are:
Brain and spinal cord disorders, such as tumors, strokes, infections, inflammation, demyelination, trauma, etc.
Musculoskeletal disorders, such as arthritis, fractures, ligament tears, tendon injuries, cartilage damage, etc.
Cardiovascular disorders, such as ischemic heart disease, myocardial infarction, cardiomyopathy, valvular disease, congenital heart disease, etc.
Abdominal and pelvic disorders, such as liver cirrhosis, pancreatic cancer, renal failure, prostate cancer, ovarian cysts, uterine fibroids, etc.
Breast disorders, such as breast cancer, benign lesions, implant rupture, etc.
Depending on the patient pathology, different imaging protocols and sequences may be required to obtain the best diagnostic information. For example, some pathologies may require contrast agents to enhance the signal or highlight abnormal tissues. Some pathologies may require functional or dynamic imaging to assess blood flow or tissue perfusion. Some pathologies may require specific sequences to suppress or emphasize certain tissues or fluids.
Considerations When Positioning Both the Patient and Coil
Patient Comfort and Safety
The patient comfort and safety are paramount when performing an MRI scan. The patient should be informed about the procedure and its risks and benefits. The patient should be screened for any contraindications or precautions for MRI, such as metal implants, pacemakers, claustrophobia, pregnancy, etc. The patient should be instructed to remove any metal objects or clothing that may interfere with the magnetic field or cause injury.
The patient should be positioned on the MRI table in a comfortable and stable manner. The patient should be aligned with the center of the magnet and secured with straps or cushions to prevent motion artifacts. The patient should be given earplugs or headphones to protect from the loud noise of the scanner. The patient should be given a call button or an intercom to communicate with the technologist during the scan. The patient should be monitored for any signs of distress or adverse reactions during the scan.
Coil Selection and Placement
The coil is the device that transmits and receives the radio signals in MRI. The coil selection and placement are crucial for obtaining optimal image quality and coverage. Different types of coils are available for different body regions and pathologies. Some coils are fixed inside the scanner (such as the head coil or the body coil), while others are flexible and can be wrapped around the body part (such as the knee coil or the breast coil).
The coil should be chosen according to the size and shape of the body part and the desired field of view. The coil should be positioned as close as possible to the body part to maximize the signal-to-noise ratio. The coil should be oriented according to the imaging planes and anatomical alignment. The coil should be connected properly to the scanner and checked for any defects or malfunctions.
Imaging Planes and Anatomical Alignment
The imaging planes are the directions in which the MRI images are acquired. The imaging planes can be axial (horizontal), sagittal (vertical), coronal (frontal), or oblique (angled). The imaging planes should be selected according to the body region and pathology. For example, axial images are commonly used for brain and spine MRI, sagittal images are commonly used for knee and spine MRI, coronal images are commonly used for chest and abdomen MRI, etc.
The anatomical alignment is how the images are aligned with the anatomical landmarks of the body part. The anatomical alignment can be parallel (along) or perpendicular (across) to a certain landmark. The anatomical alignment should be consistent and accurate for each imaging plane. For example, axial images of the brain should be parallel to a line connecting the anterior commissure (AC) and posterior commissure (PC) of the brainstem . Sagittal images of the knee should be perpendicular to a line connecting the medial and lateral femoral condyles . Coronal images of the chest should be parallel to a line connecting the sternal notch and xiphoid process .
Imaging Protocols and Sequences
Routine Sequences
The imaging protocol is a set of 71b2f0854b