If there is any suspicion or lack of information on the implant, do not take any risk with the patient safety and do not scan the patient. Design of the First MR Scanner In 1972, Raymond Damadian (Downstate Medical Centre, Brooklyn) measured the T1 and T2 relaxation times of the normal tissue and tumor in rats and showed that tumors had longer relaxation times using an NMR apparatus. As the last line of patient safety, it is also a good practice to scan patient with a handheld metal detector before taking the patient to MRI room. Disclaimer.fm Pa, q 2007 by Taylor & Francis Group, LLC Figure 8.32 A sample for feet first and supine patient positioning in a multichannel transmit/ receive knee coil is shown. CENTRAL NERVOUS SYSTEM: MRI PROTOCOLS, IMAGING PARAMETERS 159 Figure 7.41 Patient positioning on an eight CH neurovascular coil for brachial plexus is shown. Figure 11.3 Sagittal planning from coronal and axial images is shown. Sample Imaging Protocols A sample imaging protocol for a patient referred to the MRI for long bone scan is given in Tables 8.26 and 8.27. pathological processes (such as possible visualization of the The images on the top row show an optimum TI time of 200 ms to suppress the healthy myocardium and perfectly delineate the infarct area shown (pointed with the arrow). should be entirely included on one or two single radiographs. Technical factors A review of normal tissue hydrogen NMR relaxation times and relaxation mechanisms from 1100 MHz: dependence on tissue type, NMR frequency, temperature, species, excision, and age. The patient is positioned supine on the radiographic table, with This special view is known as a Grashey projection. In three-point or two-point Dixon methods, the relevant numbers of slightly different TE times are applied to create a phase difference between fat and water. views. If you are scanning mainly for globes, use a T1 Fat sat imaging and repeat it postcontrast. Axial or sagittal FSE T1. 2.9. 2.6. If you M. Elmaolu and A. elik, MRI Handbook: MR Physics, Patient Positioning, and Protocols, DOI 10.1007/978-1-4614-1096-6_8, Springer Science+Business Media, LLC 2012 181 182 MRI HANDBOOK have one of the new multichannel brain coils but not the loop coils, you can still follow the guidance in the book to acquire very nice TMJ images. If you have a rectangular matrix, then resolution can be stated as resolution in frequency and resolution in phase direction using the same exact formula as above. position (recumbent or upright). Especially, 3D T2 imaging with thin slices can be used for better resolution and quality. New Jersey: Humana Press Inc. Hodler, J., Schulthess, G.K. & Zollikofer, C.L., 2007. NMR relaxation data of water proton in normal tissues. Position the arm in the external, internal, or neutral phalanges. of the scapula. Figure 7.58 Coronal slice prescription from sagittal and axial images is shown. Diffusion can be applied as an additional sequence with multiple b values. 9.12). By following these Recommended Standards of Practice, the surgical team can reduce the chances of patient complications, related to positioning as well as contribute to preventing team members suffering a musculoskeletal injury. This e-book is for absolutely everyone who owns a small commercial employer or is interested in prolonging their own retirement. This option gives the full decision power to the user with the real-time monitoring of the contrast arrival. Please make sure that you give the patient alarm/buzzer to patients hand and test it. Due to low flip angle (smaller rf pulse), their SAR exposure is much less than SE family. CENTRAL NERVOUS SYSTEM: MRI PROTOCOLS, IMAGING PARAMETERS Figure 7.14 133 Coronal slice prescription from sagittal and axial images is shown. Table 7.22 Imaging parameters for an eight channel brain coil is shown. Wrist Imaging Similar to elbow imaging, wrist imaging can be done with several different coils. Access to Medical Care for Individuals with Mobility Disabilities shoulder dislocations. superimposed over the first two cervical vertebrae. 112 MRI HANDBOOK Sample Imaging Parameters for 1.5 T See Table 7.5 Graphical Prescription Axial, coronal, and sagittal planning is same as routine brain as you can expect. If there are any surgical implants, radiologist on duty has to make a decision based on implant type and MR compatibility. Patient Positioning: The spine coil should be centered on the table. A closed or narrowed obturator foramen indicates rotation T2* Relaxation T2* relaxation time is essentially same as T2 relaxation time. Right and left markers, as well as markers indicating with and The first nonselective inversion pulse inverts all the spins in the broad range of anatomy and the second selective inversion pulse inverts nonmoving tissues back to initial state within the selected slice. Table 7.8 Sample protocol for hemorrhage patients. It must be signed by the patient or legal guardians and confirmed by MR personnel. MUSCULOSKELETAL IMAGING: MRI PROTOCOLS, IMAGING PARAMETERS 209 Knee Imaging Knee joints are usually imaged unilaterally using dedicated coils. The decision to administer MR contrast agent to pregnant patients should be accompanied by a welldocumented and thoughtful risk-benefit analysis (ACR guidance, 2007) Contrast Agents: According to ACR guidance cleared in 2007, no patient is to be administered prescription MR contrast agents without orders from a duly licensed physician. Seat the patient at the end of the table on a stool or chair. However, if 6. forearm. direction. forearm in contact 1. with the table and the hand in the lateral Kinematic imaging requires imaging TMJ joint while the mouth is closed and opened at different levels, so that the joint and disc position can be imaged dynamically. In practice, we can also measure T2 value of any tissue by choosing a minimum of three or four different TE times and fitting the resulting signal intensities to an exponential function. However, due to their widespread use, we discuss them in a separate section. separated. Either in mm or in percentage, more than 25% slice spacing is recommend for routine 2D imaging. Fat Separation: Fat separation is almost a new concept in routine imaging with the emergence of new pulse sequences separating water and fat. jewelry as well. Additionally, you can use the end of the pillow to create knee extension after a total knee replacement. Then, by simply looking at the MR signal difference at each TE times, we can calculate the optimal TE times resulting T2 Decay Curve for WM and CSF MR Signal (Mxy) B0 1 0,9 0,8 0,7 0,6 0,5 0,4 0,3 0,2 0,1 0 CSF WM TE = 178ms, max contrast 0 100 200 300 400 500 600 700 800 900 1000 TE (miliseconds) Figure 3.7 The T2 relaxation curve is shown for CSF and WM using (3.3). Effective Echo Time (Eff TE): For multiple echo images, the TE time can be selected by the user as well. The main difficulty of cardiac MR examinations is the need for repeated breath holds due to the obvious need of eliminating the respiratory artifacts. Despite the incredible recon speeds of the new MR scanners today, the recon speed may still be a limiting factor in certain MR acquisition. Practical planning 1: Assuming a single dose injection with a half molar contrast agent such as omniscan, magnevist, dotarem, etc. T2 Relaxation I am hoping that you learned what the T1 relaxation is and how to measure it. radiographic table with 1. a pillow for the head (use the same body Table 7.54 A sample lumbar spine trauma protocol is shown. T2* PD fat sat T1 Plan Axial Coronal Coronal Sagittal Sagittal Axial Axial Sequence type MERGE FRFSE FSE FRFSE FRFSE FRFSE FSE TE MinFull 40 MinFull 37.5 85 40 MinFull TR 513 2,420 560 2,560 3,040 2,480 740 9 3 9 15 9 2 ETL PD fat sat T2 PD fat sat T1 BW 31.25 20.83 50.0 20.83 31.25 20.83 41.67 Slice thickness 4.0 4.0 4.0 3.0 3.0 4.0 4.0 Slice spacing 1.0 1.0 1.0 1.0 1.0 1 1.0 FOV 17 1416 1416 16 16 1417 1417 Matrix 288 224 256 224 352 256 320 224 352 320 320 256 384 224 NEX/NSA 2 4 3 4 2 3 2 Freq direction R-L S-I S-I R-L SAT band/zip TI/FA RL/Z512 S-I S-I R-L I I I 25 TE (around 3540 ms) and ETL (89) for PD sequences in this book to create somewhat a hybrid PD contrast with additional T2 weighting. The central ray (CR) should be perpendicular to the GUIDELINES FOR PATIENT POSITIONING Explain the procedure. performed in an upright position. FUNDAMENTALS OF MAGNETIC RESONANCE IMAGING 19 Figure 2.10 A typical gray-scale k-space and a simple color-coded k-space that is identical to the gray scale image are shown to visualize the extension of k-space information. Sample Imaging Parameters for 1.5T Table 10.6. Some of those may require a so-called calibration scan to create a sensitivity map of each coil elements. This type of sequence provides better contrast between soft tissue (e.g., cartilage, disk, and labrum) and fluid. BODY IMAGING: MRI PROTOCOLS, IMAGING PARAMETERS 261 Table 9.12 A sample routine pelvis protocol. Axial plane is exactly perpendicular to sagittal and coronal planes. The acqusition should cover at least 68 min post injection. Patient Positioning: Patient head should be centered at the brain coil, chin pointing upward as shown in the figure below. Well, spoiling the magnetization at the end of TR cycle means that the previous history of applied gradients does not affect us (theoretically) and we can get a clean T1 weighting. If we somehow label FUNDAMENTALS OF MAGNETIC RESONANCE IMAGING 15 those protons with small frequency change with respect to their location (spatial encoding), then each proton will start precessing with a frequency slightly less or more than the Larmor frequency wo. Sequences Comments Three plane localizer Acquire 35 slices in each plane Sagittal T2 Plan 3 mm sagittal slices over coronal image where you can see the spinal cord to cover the whole spinal canal Slice order R-L Sagittal T1 Same as above R-L Axial T2 Plan 34 mm oblique axial slices from sagittal images. Table 9.1 A sample thorax protocol for potential indications such as tumor, trauma, aneurysm, or bone lesion is given. In addition, we can call them routine, fast, or ultrafast sequences. MR power cutoff button should be in an easily accessible location and direct MR staff should be trained on the presences and usage of this button. Therefore, we can only produce a T2* weighted MR contrast from gradient echo EPI sequences. Figure 8.13 A sample patient positioning for elbow in a general purpose flexible coil. The vertebrae should be aligned down in However, 1020% overlap makes the image pasting more efficient. MUSCULOSKELETAL IMAGING: MRI PROTOCOLS, IMAGING PARAMETERS 211 Figure 8.34 A sample single channel transmit/receive knee coil is shown. Disease of the Heart, Chest & Breast. Also explain that patient motion will make a negative effect on images quality. the hips and knees 1. flexed and the head on a pillow so that their The loop coil center should be placed directly at the TMJ joint. Echo Planar Imaging (EPI) Sequences Echo planar imaging (EPI) sequences, like SSFSE sequences, can be considered as one of the ultrafast sequences as well. 98 MRI HANDBOOK Relatively Contraindicative Implants: A growing list of safer implants is in development for patients today. of the hand and wrist should be aligned to the long axis of the Later on, he returned back to Zurich and died there in 1983. We will be using the graphical prescription term for slice positioning in these planes. The skin should be cleaned well to remove the dead skin layer for better connectivity. 7.197.21). The knee and foot coils are usually what we call transmit/receive coils rather than receive only coils. Figure 8.55 Sagittal prescription from axial and coronal images is shown. For kinematic exams, even though there are specific tools CENTRAL NERVOUS SYSTEM: MRI PROTOCOLS, IMAGING PARAMETERS 179 Figure 7.63 Radial planning from sagittal and axial slices is shown. exactly superimposed to prevent rotation. superimposed. If you do not have a dedicated coil, it is possible to use other available coils. Patient Positioning | PDF | Vein | Anatomical Terms Of Motion - Scribd 154 MRI HANDBOOK Figure 7.35 Coronal slice prescription from sagittal and axial slices is shown. 2.7, frequency encoding gradient is applied only in one direction to spatially encode the precession wo-5 wo-4 wo-3 wo-2 wo-1 wo wo+1 wo+2 wo+3 wo+4 wo+5 wo-5 wo-4 wo-3 wo-2 wo-1 wo wo+1 wo+2 wo+3 wo+4 wo+5 wo-5 wo-4 wo-3 wo-2 wo-1 wo wo+1 wo+2 wo+3 wo+4 wo+5 wo-5 wo-4 wo-3 wo-2 wo-1 wo wo+1 wo+2 wo+3 wo+4 wo+5 wo-5 wo-4 wo-3 wo-2 wo-1 wo wo+1 wo+2 wo+3 wo+4 wo+5 Frequency Encoding Gradient Figure 2.7 Frequency encoding gradient is applied only in one direction here to encode all the protons in the same column with the same frequency as shown with the color-coded figure above. Please make sure that you give the patient alarm bell to patient and ask them to test it before sending in. 2.1b., this magnetization can be represented by a vector called magnetic vector. INTRODUCTION TO SAFE CLINICAL SCANNING 99 Gadolinium-based Contrast Agents and Nephrogenic Systemic Fibrosis (NSF): It has been recently appeared that there might be serious effect of gadolinium-based contrast agents for development of NSF in patients with severe renal dysfunction. 8.328.35). We have witnessed again and again that MRI scanning and applications may differ significantly depending on countries and institutes. Figure 7.10 Axial slice prescription from sagittal and coronal images is shown. CENTRAL NERVOUS SYSTEM: MRI PROTOCOLS, IMAGING PARAMETERS 131 Internal Acoustic Canal (IAC) Patient Preparation and Positioning It is same as brain (please refer to Head Imaging). For example, if you enter a TE time of 100 ms for your T2 weighted FSE or TSE acquisition, you may end up getting an image with an effective TE time of 97.6 or 102 ms. pubic symphysis. 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