MRI AND ITS APPLICATIONS IN DENTISTRY.pptx

MRI and its application

1. MAGNETIC RESONANCE IMAGING AND ITS APPLICATIONS IN DENTISTRY M.SAI NISHANTH POST GRADUATE

2. Introduction Principles Protons Precession Resonance Magnetic resonance signal T1 and T2 relaxation Radiofrequency pulse sequence Contrast agents Gradient coils Spin-echo technique Image reconstruction CONTENTS

3. Advantages Disadvantages Applications of MRI

4. Paul Lauterbur described the first magnetic resonance image in 1973 and Peter Mansfield further developed use of the magnetic field and the mathematical analysis of the signals for image reconstruction. MRI was developed for clinical use around 1980. In 2003 Lauterbur and Mansfield were awarded the Nobel Prize in Physiology and Medicine. MRI is a non-invasive method to detect the internal structures, differentiate between soft tissues and hard tissues and certain aspects of functions within the body. INTRODUCTION

5. To make a magnetic resonance image, the patient is first placed inside a large magnet. This magnetic field causes the nuclei of many atoms in the body, particularly hydrogen, to align with the magnetic field . The scanner then directs a radiofrequency (RF) pulse into the patient, causing some hydrogen nuclei to absorb energy (resonate). When the RF pulse is turned off, the stored energy is released from the body and detected as a signal in a coil in the scanner. This signal is used to construct the magnetic resonance image, in essence a map of the distribution of hydrogen.

6. PROTONS Individual protons and neutrons (nucleons) in the nuclei of all atoms possess a spin, or angular momentum. In nuclei having equal numbers of protons and neutrons the spin of each nucleon cancels that of another, producing a net spin of zero. The most common of these atoms, the magnetic resonance active nuclei, are hydrogen, carbon 13, nitrogen 15, oxygen 17, fluorine 19, sodium 23, and phosphorus 31. Hydrogen is by far the most abundant of these atoms in the body. PRINCIPLES

7. A hydrogen nucleus consists of a single unpaired proton and therefore acts as a magnetic dipole. Normally these magnetic dipoles are randomly oriented in space. When an external magnetic field is applied, the hydrogen nuclear axes align in the direction of the magnetic field . Two states are possible: spin-up, which parallels the external magnetic field , and spin-down, which is antiparallel with the field .

8. Because more energy is required to align antiparallel with the magnetic field , those hydrogen nuclei are considered to be at a higher energy state than those aligned parallel with the field . Nuclei prefer to be in a lower energy state, and usually more are aligned parallel with the magnetic field . This results in a net magnetization vector in the direction of the magnetic field . Increasing the magnetic field strength increases the magnitude of the net magnetization vector.

9. the orientations of the axes of spinning protons actually oscillate with a slight tilt from a position absolutely parallel with the flux of the external magnet. This tilting of the spin axis, called precession. PRECESSION

10. the presence of the magnetic field causes the axis of the spinning proton to wobble (or precess ) around the lines of the applied magnetic field . The rate or frequency of precession is called the precessional , resonance, or Larmor frequency. The precessional frequency depends on the species of nucleus (hydrogen nucleus or other) and is proportional to the strength of the external magnetic field .

11. The magnetic field in a magnetic resonance scanner is provided by an external permanent magnet. Magnetic resonance field strengths range from 0.1 to 4 Tesla (T) with 1.5 T being the most common. (1.5 T is about 30,000 times the strength earth ’s magnetic field .) The Larmor precession frequency of hydrogen is 63.86 megahertz in a magnetic field of 1.5T .

12. Nuclei can be made to undergo transition from one energy state to another by absorbing or releasing energy. Energy required for transition from the lower to the higher energy level can be supplied by electromagnetic energy in the RF portion of the electromagnetic spectrum In an MRI scanner the RF broadcast from an antenna coil is directed to tissue with protons (hydrogen nuclei) aligned in the Z axis (long axis of a patient) by the external static magnetic field . When the frequency of the RF pulse matches the Larmor frequency of the protons in the tissue, the protons resonate and absorb the RF energy. This causes some of the low-energy nuclei (parallel) to gain energy to convert to the high-energy ( antiparallel ) state. As a consequence, the longitudinal magnetic vector is reduced. RESONANCE

13. The longer the RF pulse is applied, the less the longitudinal magnetic vector. The RF pulse also causes the protons to precess in phase with each other, resulting in a net tissue magnetization vector in the transverse plane (XY plane) perpendicular to longitudinal alignment (Z axis) If the RF pulse is of sufficient intensity and duration, the longitudinal magnetic vector is reduced to zero. An RF pulse that accomplished this is called a 90-degree RF pulse or having a flip angle of 90 degrees. At this time the net magnetic vector in the transverse plane is maximized because the magnetic moments of all nuclei are in phase.

14. The precession of the net magnetic vector, that is, the precession of the magnetic moments of the hydrogen nuclei in phase in the transverse plane, induces a current flow in a receiver coil, the MR signal. The frequency of this alternating current signal matches the frequency of the RF pulse and the Larmor precessional frequency of hydrogen nuclei. The magnitude of this signal is proportional to the overall concentration of hydrogen nuclei (proton density) in the tissue. This strength of the signal also depends on the degree to which hydrogen is bound within a molecule. MAGNETIC RESONANCE SIGNAL

15. Tightly bound hydrogen atoms, such as those present in bone, do not align themselves with the external magnetic field and produce only a weak signal. Loosely bound or mobile hydrogen atoms such as those in soft tissues and liquids react to the RF pulse and thus produce a detectable signal at the end of the RF pulse. The concentration of loosely bound hydrogen nuclei available to create the signal is referred to as the proton density or spin density of the tissue in question. The higher the concentration of these nuclei of loosely bound hydrogen atoms, the stronger the net transverse magnetization, the more intense the recovered signal, and the brighter the corresponding part of the magnetic resonance image.

16. Then the RF pulse is turned off, the nuclei begin to return to their original lower-energy spin state, a condition called relaxation. As they give up the energy absorbed by the RF pulse, some of the high-energy nuclei return to the low-energy state and the net longitudinal magnetic vector returns to its original state. Additionally, and independently, the individual magnetic moments of the protons begin to interact with each other and dephase . This results in reduction of the magnetization in the transverse plane, a condition called decay.

17. As a result of the loss of transverse magnetization and the dephasing of the hydrogen nuclei, there is a loss of intensity of the magnetic resonance signal. The reduced voltage induced in the receiving coil is called the free induction decay (FID) signal. In sum, the FID of the MR signal results from the loss of the transverse net magnetization vector. This results from return of the net magnetization vector to the longitudinal plane and dephasing of the hydrogen nuclei.

18. Relaxation at the end of the RF pulse results in recovery of the longitudinal magnetization. This is accomplished by a transfer of energy from individual hydrogen nuclei (spin) to the surrounding molecules (lattice). This is an exponential process and the time required for 63% of the net magnetization to return to equilibrium (the time constant) by this transfer of energy is called the T1 relaxation time or spin-lattice relaxation time. The T1 relaxation time varies with different tissues and reflects the ability of their nuclei to transfer their excess energy to surrounding molecules T1 AND T2 RELAXATION

19. Additionally, and the end of the RF pulse, the magnetic moments of adjacent hydrogen nuclei begin to interfere with one another, causing the nuclei to dephase with a resultant loss of transverse magnetization. The time constant that describes the exponential rate of loss of transverse magnetization is called the T2 relaxation time or the spin-spin relaxation time. As the transverse magnetization rapidly decays to zero, so does the amplitude and duration of the detected radio signal. T2 relaxation occurs more rapidly than T1 relaxation.

20. the components of the RF pulse sequence are set by the operator and determine the appearance of the resultant image. The most basic features of a pulse sequence are the repetition time (TR) and echo time (TE). The TR time is the duration between repeat RF pulses. The time between pulse repetitions determines the amount of T1 relaxation that has occurred at the time the signal is collected. The TE time is the time after application of the RF pulse when the magnetic resonance signal is read. It controls the amount of T2 relaxation that has occurred when the signal is collected. RADIOFREQUENCY PULSES SEQUENCES (AND IMAGE CONTRAST)

21. Image contrast between tissues is governed by intrinsic features of the tissues, including proton density, T1 and T2 times of the issues being imaged, and how the TR and TE times are adjusted to emphasize these features. For instance, a tissue that has a high proton density and strong transverse magnetization vector (protons precessing in phase) at TE will produce a strong magnetic resonance signal that will appear bright on a magnetic resonance image. Conversely, a tissue with a low proton density or low transverse magnetization vector at TE produces a weak signal and appears dark on a magnetic resonance image. TISSUE CONTRAST

22. T1-weighted image emphasizes differences in T1 values of tissues. This is accomplished by use of short TR times, typically 300 to 700 ms, and short TE times (20 ms). In such images tissues with fast T1 times, such as fat, will appear bright, whereas those with long T1 times, such as cerebrospinal fluid (CSF) (water), will appear dark. T1-weighted images are more commonly used to demonstrate anatomy. T1-Weighted Image

23. T2-weighted image emphasizes differences in T2 values of tissues. This is accomplished by use of long TR times (2000 ms) and long TE times, typically 60 ms or more. In such images tissues with long T2 times, such as CSF for temporomandibular (TMJ) joint fluid , will appear bright, whereas tissues with short T2 times, such as fat, will appear dark. Images with T2 weighting are most commonly used for identifying inflammatory or other pathologic changes. Techniques such as spin echo and gradient echo allow images to be captured rapidly. Other techniques allow the signal from fat, or water, to be enhanced or suppressed. A technique called “ fat saturation ” nulls the signal from fat. T2-Weighted Image

24. Contrast agents, most commonly gadolinium, may be administered intravenously to improve tissue contrast. Gadolinium is not imaged itself, but rather it shortens the T1 relaxation times of enhancing tissues, making them appear brighter. It is useful for enhancing some tumors by allowing them to be better differentiated from surrounding normal tissue. For imaging the head and neck, it is common practice to obtain T1, T1 postgadolinium administration and with fat saturation, and T2 with fat saturation images. It should be noted that just recently there is evidence that gadolinium-based contrast media could be a cause of a debilitating disease called nephrogenic systemic fibrosis in some patients with renal dysfunction. The implications of this finding are under active study. Contrast Agents

25. MRI Images. MRI examination performed to evaluate neck mass in a patient with known diagnosis of multiple myeloma. A, Axial T1 precontrast (no fat saturation) image through mandible. Note abnormally dark marrow in posterior right mandible ( arrow, compare with left side) and mass in right carotid space (other arrow) . B, Axial T1 postcontrast image with fat saturation. Note abnormal enhancement of both marrow in right mandible and of the mass in the right carotid space.

26. MRI Images. MRI examination performed to evaluate neck mass in a patient with known diagnosis of multiple myeloma C, Axial T2 with fat saturation demonstrating abnormally bright signal in both marrow in right mandible and of the mass in the right carotid space. (Courtesy Dr. Thomas Underhill, Radiology Associates, Richmond, Va.)

27. Producing an image from the NMR signals (i.e., MRI) requires that a specific slice within the patient's body be examined, and that voxels be designated within the slice. Three functions select the slice and voxels : 1. A magnetic field gradient along the z axis is the slice selection gradient. 2. The Y-gradient produces phase encoding within the slice. 3. The X-gradient produces frequency encoding within the slice. MAGNETIC FIELD GRADIENT COILS

28. Preparation for slice selection is done with a pair of magnetic field gradient coils. The coils produce a gradient along the z axis of the patient. Typical gradient coil magnetic field strengths are 0.2 to 1.0 gauss per cm (.00002 to .0001 tesla per cm). Consider a 30-cm imaging volume, a 1-tesla magnet, and a gradient field of 1.0 gauss per em . Magnetic field strength will vary from .9985 T toward the patient's feet, to 1.0015 toward the head, and will be 1.0000 T in the center of the imaging volume. Slice Selection

29. Apply a Z-gradient so protons in one slice precess at a unique Larmor frequency, different from all other protons in the imaging field. Tip the resulting magnetization (M) vector with a 90 degree RF pulse that matches the unique Larmor frequency. Assume a 1-cm thick slice. Calculate the Larmor frequency along each side of the slice if the magnetic field varies from 1. 00 1 0 T to 1. 00 11 T across the slice: (42,580,000) X (1.0011) = 42,626,838 Hz (42,580,000) x (1.001 0) = 42,622,580 Hz

30. In our example, a 1-cm slice is represented by a Larmor frequency difference of 4258 Hz (or 4.258 kHz). To select the slice in question, the RF transmitter is tuned to transmit frequencies from a low of about 42.6226 mHz to a high of about 42.6268 mHz. A 90 degree pulse transmitted at this frequency range will cause the m vector to rotate 90 degree in only the 1-cm slice in question. In a 1-tesla magnet with a gradient of 1.0 gauss per cm, an RF pulse width of 4.258 kHz will select a 1-cm wide slice, whereas a 2.12g-kHz pulse width will select a 0.5- cm wide slice. Thus, the frequency of the RF pulse selects the location of slice, and the band width of the RF pulse selects the thickness of the slice

31. Phase encoding is the first step in dividing a slice into voxels for purposes of image reconstruction. A y-axis magnetic field gradient is applied in a fashion similar to the z-axis gradient. Two pairs of Y -gradient coils ( 4 coils total) are positioned. PHASE ENCODING

32. Alignment of the coils changes the magnetic field strength from the back to the front of the patient. When the Y -gradient coils are on, the protons near the front of the patient will precess faster (because they are in a higher magnetic field) than those protons near the back of the patient. The Y -gradient is turned on at the end of the 90 degree RF pulse, and is left on for a short time (about 3 to 5 ms). The purpose of the Y -gradient is to change the phase of the magnetization vectors in each row of the slice being imaged.

33. row 1 is assumed to be about in the middle of the patient (where there is little or no gradient), and row 3 near the front of the patient where the gradient is positive and at a maximum. Since row 3 is in the strongest magnetic field, all its protons will precess faster than will the protons in row 2 or row 1. the effect by showing the Mxy in row 2 is 90 degree ahead of row 1, and the Mxy vector in row 3 is 180° ahead of row 1.

34. Now the Y-gradient is suddenly turned off. Immediately, all protons in rows 1, 2, and 3 begin to precess at the same rate (determined by the main magnetic field H). But, each Mxy vector "remembers" and maintains the phase at which it was precessing at the end of the Y-gradient pulse. This row-by-row phase difference has divided the previously uniform slice into horizontal rows. At the end of a Y -gradient pulse, all Mxy vectors are precessing at the same rate, but not all Mxy vectors are in the same phase.

35. The Z-gradient allowed slice selection. The Y-gradient allowed each slice to be phase encoded. Now an X-gradient is going to allow each slice to be divided by frequency encoding. The purpose of the Xgradient is to change, very slightly, the magnetic field in the imaging volume to create a gradient along the x axis. Frequency Encoding

36. the main magnetic field is reduced on the patient's right side and increased on the left side. The X gradient will cause the protons in different vertical columns (columns A, B, and C in to experience slightly different magnetic fields. Protons in different magnetic fields will precess at different frequencies with the magnetization vectors in column A precessing slower than those in column B. The X-gradient is the frequency-encoding gradient. In this example, frequency encoding provides a way to divide the slice into vertical columns. The Y-gradient uses phase encoding to divide the slice into horizontal rows.

37. to assemble the RF pulses and magnetic field gradients into a temporal package that will allow acquisition of an image. The spin echo pulse sequence with 2D-FT transformation is most commonly used in clinical imaging. THE SPIN ECHO IMAGING SEQUENCE

38. This is a line diagram of the timing of the components of the spin echo sequence. During segment l of the spin echo pulse an RF pulse and Gz allow slice selection. During segment 2, Gy produces phase encoding. When Gy is turned off, protons once again begin precessing about H at the Larmor frequency. Dephasing of protons begins as a result of T1/2, and an FID is produced. Fid is not detected. Instead, preparation for an echo is made by applying a 180° pulse (the 180° pulse occurs in segment 3. The slice selection gradient ( Gz ) is on during the 180° RF pulse. The echo is detected during segment 4 of the pulse sequence.

39. During echo detection, the frequency encoding gradient, Gx is turned on. Since Gx on during detection, or "reading," of the echo; Gx is often called the "readout gradient." Segment 5 is the long interval following the readout of the echo, before another 9o% pulse starts the sequence all over again.

40. The imaging technique is a twodimensional Fourier transform (2D-FT) spin echo technique. This technique includes phase encoding, frequency encoding, and the spin echo pulse sequence. to perform a Fourier transform in the frequency direction and then a Fourier transform in the phase direction (these are the two dimensions of the 2D-FT). These transforms are performed within the system computer. Since computers work on a binary system, the computer give us information in a pixel format that is based on powers of two (2n). Image Reconstruction

41. the computer may digitize the continuously varying frequency in the echo signal into 256 discrete frequency values (256 = 28). To obtain equal resolution throughout the image, it is necessary to have 256 different phase divisions as well as the 256 frequency divisions. These phase divisions are accomplished by varying the GY gradient 256 times per image. From these two transforms the computer can form the final image, and assign display values to selected pixel sizes.

42. Z axis-slice selection Y axis phase encoding X axis frequency encoding

43. No detrimental effect as it uses non- ionizing radiation. Helps to differentiate soft tissue from one another due to contrast resolution. Multiplanar image ( sagittal , coronal, oblique) can be obtained. Safe in pregnant ladies and children. Artifacts with dental filling are not seen. Manipulation of image can be done ADVANTAGES

44. the difficult visualization of tissues poor in water. Patients suffering from claustrophobia, the presence of devices that prevent the examination from taking place (contain ferromagnetic metals (e.g., cardiac pacemakers, some cerebral aneurysm clips or ferrous foreign bodies in the eye), artifacts from materials and movements, the cost, the lack of availability, and the long examination time DISADVANTAGES

45. TMJ disorders MRI demonstrates the internal structure of TMJ with great precision and contrast resolution. TMJ dysfunction is a common condition that is best evaluated with MRI. The MRI findings in terms of functional aspect of disc position, degree of disc displacement, disc deformity, joint effusion, and osteoarthritis has been used for the prediction of Temporomandibular Dysfuction (TMD) symptoms in patients with and without TMJ disorders. APPLICATION IN DENTISTRY

46. At sagittal MR imaging, the meniscus appears as a biconcave structure with homogeneous low signal intensity that is attached posteriorly to the bilaminar zone, which demonstrates intermediate signal intensity. The posterior band and retrodiskal tissue are best depicted in the open-mouth position. Typically, the anterior band and the intermediate zone are hypointense and the posterior band is slightly hyperintense , although the posterior band is more frequently hypointense in patients with disk disease. The anterior band lies immediately in front of the condyle and the junction of the bilaminar zone, and the disk lies at the superior part of the condyle . The anterior band can be seen as a bulge, which some authors have described as a normal variant of the disk. Disk Evaluation in MRI

47. Maxillary Sinus Diagnosis and Surgery In maxillary sinus surgery for implant placement, it is important to know and visualize the state of the Schneiderian membrane and any reactive thickening phenomena. CBCT allows for visualizing the three-dimensional bone morphology, but the mucosa is poorly defined , despite exposure to ionizing radiation. In this evaluation, MRI is positioned as a very interesting exam with great margins for improvement, having also demonstrated its usefulness in complete implant planning and in defining the state of health of the maxillary sinus and the Schneiderian membrane for any bone regeneration

48. Implantology In implantology it is very important to consider the anatomical limitations. For example, the mandibular canal position, an extremely important limitation in the posterior atrophic mandible, is excellently displayed with the use of the T1-weighted 3D sequence. In radiographic imaging, the problem of artefacts is always present, but peri -implant bone defect evaluation, or studies about bone morphology near the implant, are still being carried out. radiographic imaging is used for patient follow-up, but always with exposure to a certain dose of ionizing radiation. magnetic resonance imaging can become an easily repeatable diagnostic test with an excellent risk/ benefit ratio. magnetic resonance imaging allows for the detailed measurement of mucosal thickness and can aid in the planning of palatal tissue harvesting to obtain soft tissue augmentation

49. MR-evaluation of implant osseointegration with three chosen axial views (cavity, thread, peri -apical implant site). The dental implant is visible as round black circle. The implantation area is detectable in peri -apical slice images after two and four weeks healing period as circular region with slightly darker grey scale (marked by the dashed orange line and circle). The scale bars represent 1 mm.

50. Apical Periodontitis Diagnosis The need for a diagnostic exam is highlighted, such as MRI, free from biological damage, unlike CBCT or CT, and able to evaluate in vivo the nature of the lesion and to orient the clinician towards the most appropriate treatment, whether it is surgical for true root cysts or endodontic, orthograde retreatment for periapical pocket cysts or granulomas . MRI not only provides excellent soft tissue contrast but also allows for the evaluation of specific tissue components in different sequences. MRI has shown diagnostic superiority over CT techniques in various soft tissue associated pathologies in the head and neck region, in fact, MRI is the most suitable examination for the study of brain and solid tumors

51. Only Geibel and colleagues have systematically analyzed apical bone lesions with MRI; in a comparison between MRI and CBCT for the diagnosis of periapical lesions, they concluded MRI has shown greater sensitivity in diagnosing periapical lesions than CBCT, in particular, when cystic fluid was present, thus excluding that it may be a vascularized lesion, such as a peri -apical granuloma . Moreover, it can more precisely diagnose the true dimensions of a lesion, and can provide a better estimation of the relationship between a lesion and critical structures, such as nerves and vessels. dental MRI could detect inflammatory pathologies at an early stage, long before CBCT or conventional radiographs.

52. Evaluation of Dental Fractures Regarding dental fractures, MRI has the potential to help in determining the presence and extent of cracks and fractures in teeth due to good contrast, and especially without exposure to ionizing radiation as with CBCT, which is considered the current clinical standard.

53. Endodontics , Endodontic Anatomy and Conservative Dentistry MRI offers high-level tissue visibility, equal to or even greater than CT and CBCT, but it requires sufficient resolution that tends to be achieved only with much longer scan times, without, however, exposure to ionizing radiation. The high-intensity signal from water and the lack of signal from mineralized tissues produce a high contrast that allows for the recognition of the dental crown and the outline of the pulp chamber, root canals, and carious lesion. In order for magnetic resonance imaging to be applied to endodontic clinical practice, it is necessary to scan at the microscopic level, with microscopy MRI defined as an MRI with voxel resolutions better than 100 mm3.

54. Magnetic resonance microscopy chambers are generally small, typically less than 1cm3. With are solution of about 100–300mm, magnetic resonance microscopy could lead to a better understanding of processes that occur inside the teeth. MRI can therefore be useful in evaluating reperfusion, for example, that concerning regenerative endodontic procedures (REPs) and dental trauma. The application limit of this examination is that, to obtain a sufficient resolution for clinical evaluation in vivo, it takes up to 90 min. The visualization of hard tissues, such as enamel and dentin that do not have MRI signals, considering the low content of protons, remains the real technical challenge to be faced in making MRI a daily diagnostic exam in dentistry.

55. Exemplary images of a lower molar: I = native tooth; II = after root canal preparation; III = after obturation ; a = photography; b = periapical X-ray; c= cbct axial and sagittal , d = MRI axial and sagittal ; e = 3D-MRI reconstruction

56. Christensen's Physics of Diagnostic Radiology 4 th edition White SC, Pharoah MJ. White and pharoah's oral radiology e-book: principles and interpretation. Elsevier Health Sciences; 2018 Sep 12 . Reda , R.; Zanza , A.; Mazzoni , A.; Cicconetti , A.; Testarelli , L.; Di Nardo , D. An Update of the Possible Applications of Magnetic Resonance Imaging (MRI) in Dentistry: A Literature Review. J. Imaging 2021, 7, 75. https://doi.org/ 10.3390/jimaging7050075 Katti G, Ara SA, Shireen A. Magnetic resonance imaging (MRI)–A review. International journal of dental clinics. 2011 Jan;3(1):65-70. Niraj LK, Patthi B, Singla A, Gupta R, Ali I, Dhama K, Kumar JK, Prasad M. MRI in dentistry-a future towards radiation free imaging–systematic review. Journal of clinical and diagnostic research: JCDR. 2016 Oct;10(10):ZE14. REFERNCES

57. Geha H, Gaalaas LR, Nixdorf DR. MRI for Dental Applications. Dental Clinics of North America. 2018 Jul 1;62(3):467-80. Hilgenfeld T, Juerchott A, Jende JM, Rammelsberg P, Heiland S, Bendszus M, Schwindling FS. Use of dental MRI for radiation-free guided dental implant planning: A prospective, in vivo study of accuracy and reliability. European Radiology. 2020 Dec;30(12):6392-401. Hövener JB, Zwick S, Leupold J, Eisenbei β AK, Scheifele C, Schellenberger F, Hennig J, Elverfeldt DV, Ludwig U. Dental MRI: imaging of soft and solid components without ionizing radiation. Journal of Magnetic Resonance Imaging. 2012 Oct;36(4):841-6. Timme M, Masthoff M, Nagelmann N, Masthoff M, Faber C, Bürklein S. Imaging of root canal treatment using ultra high field 9.4 T UTE-MRI–a preliminary study. Dentomaxillofacial Radiology. 2020 Jan;49(1):20190183.

58. Dwivedi AN, Tripathi R, Gupta PK, Tripathi S, Garg S. Magnetic resonance imaging evaluation of temporomandibular joint and associated soft tissue changes following acute condylar injury. Journal of oral and maxillofacial surgery. 2012 Dec 1;70(12):2829-34. Tomas X, Pomes J, Berenguer J, Quinto L, Nicolau C, Mercader JM, Castro V. MR imaging of temporomandibular joint dysfunction: a pictorial review. Radiographics . 2006 May;26(3):765-81. Larheim TA. Role of magnetic resonance imaging in the clinical diagnosis of the temporomandibular joint. Cells Tissues Organs. 2005;180(1):6-21. Chua E, Navaratnam AV, St Leger D, Lam V, Unadkat S, Weller A. Comparison of MRI and CT in the Evaluation of Unilateral Maxillary Sinus Opacification . Radiology Research and Practice. 2021 Jul 9;2021.

59. Munhoz L, Júnior RA, Abdala R, Asaumi J, Arita ES. Diffusion-weighted magnetic resonance imaging in maxillary sinuses inflammatory diseases: Report of three cases and literature review. Journal of oral & maxillofacial research. 2018 Apr;9(2). Weiss F, Habermann CR, Welger J, Knaape A, Metternich F, Steiner P, Rozeh B, Schoder V, Bücheler E. MRI in the preoperative diagnosis of chronic sinusitis: comparison with CT. RoFo : Fortschritte auf dem Gebiete der Rontgenstrahlen und der Nuklearmedizin . 2001 Apr 1;173(4):319-24. Larheim TA. Role of magnetic resonance imaging in the clinical diagnosis of the temporomandibular joint. Cells Tissues Organs. 2005;180(1):6-21.