CT, MRI AND SONOGRAPHY IN STOMATOLOGY J.Stulík – Department of radiology and nuclear medicine FN Brno_modra_obdelnik ¢ ¢Computed tomography (CT) ¢ a)Classic CT b)Dental Cone Beam CT ¢CT images are acquired while the x-ray tube i rotating 360dg. around the patient ¢ ¢The x-ray beam is collimated in axial orientation and divergent to encompass the patient‘s width in the other orientation. ¢ ¢The intensity of attenuated x-rays emerging from the patient is measured with an array of minute detectors CLASSIC CT MULTISLICE CT ¢Several rows of detectors each above another ¢MS- detector array segmented in z axis, as a mosaic. ¢–Allows for simultaneous acquisition of multiple images in scan plane with ONE rotation. 07 08 CLASSIC CT INDICATION —Examination of facial soft tissue —parotid gland disease —diagnosing and staging tumors —diagnosis and assess the extent of osteomyelitis (inflammation of the jaw bone) —temporomandibular joint disorders —impacted teeth —complex traumatic injuries of facial skelet ¢ Complex fractures of facial skelet Absces The extensive osteolysis of the temporal bone Postprocessing - reconstructions Multiplanar rec. - MPR Volume rendering technique - VRT Shadow surface display - SSD 03-000_003_1 03-000_003_5 03-000_002_70 1 03-000_004_03 /7 10 HOW CBCT WORKS ¢Similar to current CT technology ¢Uses cone shaped x-ray beam ¢2-D flat panel detector ¢Gives volumetric data Theory Dental Cone Beam CT /7 11 ADVANTAGES IN DENTAL IMAGING ¢Lower dose than helical CT ¢Compact design ¢Superior images to Panoramic ¢Low cost ¢Low heat load ¢ Dose: Panoramic: 6-20 µSv CBCT: 20-70 µSv Conventional CT: 314 µSv /7 12 CBCT The i-Cat CBCT Cephalometric CBCT image Cephalometric Panoramic image /7 13 SHORTCOMINGS ¢Worse resolution in low contrast tissues ¢Long scan times = motion artifacts ¢Slightly Inferior quality to conventional CT Periodontal ligament spaces easily recognizable in the dental CT but not satisfactory in the CBCT CBCT /7 14 APPLICATIONS OF CBCT ¢Great for pre-planning for implant surgery ¢Virtual Surgery ¢Conventional CT diagnosis at 1/5 the dose ¢Tumor detection ¢Airway visualization ¢ 3D-transparent /7 15 CONCLUSIONS ¢CBCT offers less dose than conventional CT ¢CBCT offers superior images and diagnosis to panoramic ¢More practical than a conventional CT airway_Page_1_Image_0003 SONOGRAPHY 01 02 03 SOUND ¢Mechanical waves (energy transfer). ¢Sound use particles of enviroment for own transmision(so no sound in vacuum). ¢ ¢Infrasound 0-16 Hz ¢An audible sound 20 Hz-20 kHz ¢Ultrasound 20 kHz-10 GHz ¢Hypersound 10 GHz - ? SOUND ¢Wave propagation consists of cyclic compressions and decopressions of environmental particles compresion decompresion SOUND - GRAPHICALLY EXPRESSED ¢ -During longitudinal wave demo point out particle motion (http://members.xoom.com/Surendranath/LongWave.html) (http://members.xoom.com/Surendranath/TranWave.html) ZVUK •Vyšší frekvence = vyšší rozlišení, horší penetrace •Nižší frekvence = vyšší penetrace, horší rozlišení • SOUND - SPREAD RATE ¢ Air 330 m/s Water 1480 m/s Liver 1550 m/s Kidney 1560 m/s Soft tissue 1540 m/s SOUND ¢The spread rate is determined only by the characteristics of the environment - in particular with density (stiffness) density (stiffness) = Speed •The average sound velocity in the human body for ultrasound purposes is about 1540 m / s -use analogy of room full of people and passing a note to illustrate density and stiffness -takes longer to pass a note with a room full of people because more people must handle it -the less curious (more stiff) people are the faster the note will be passed ¢Basic principle of ultrasound image creation - reflections of ultrasound waves on the interface of two different environments with different acoustic impedance. ¢ ¢Reflections (echos) can be displayed in a 2D image, the reflected energy intensity is expressed on a gray scale (the strongest = lightest) . PULS ULTRASOUND ¢The probe sends a wave and detects the amplitude of returning wave. ¢ ¢According to the return time, it calculates from which depth the signal was reflected. ¢ ¢Depending on the amplitude, it assigns the brightness to the point on the screen ¢ ¢The same is repeated several times in the lateral direction and together all lines of points makes final picture . APLICATION OF DIAGNOSTIC ULTRASOUND IN STOMATOLOGY ¢Detection of cortical fracture lines in maxillo-facial fractures ¢Position of mandibular condyls. ¢Detection of diseases of the salivary glands (inflammation, tumors, sialolithiasis, dilation of the outlets) ¢Detection of lymphadenopathy ¢navigational interventions (biopsy, puncture) at palpably inaccessible departments, TMJ ozonotherapy ¢Surface soft-tissue affection of the maxillo-facial region, differential diagnosis (significantly better resolution than CT) ¢ THERAPEUTIC UZ - CONSERVATIVE THERAPY THERAPEUTIC ULTRASOUND - PRINCIPLE ¢The main mechanism of therapeutic effect is high-frequency micromassage of tissues together with heat inducing hyperaemia and physico-chemical changes in the environment. ¢ ¢Its application enhances membrane permeability, accelerates diffusion in tissues, has a suppressive effect on the transmission of nerve impulses, changes the pH of the tissues. ¢ ¢The result is an analgesic and spasmolytic effect, increased local blood circulation and consequently also metabolism . THERAPEUTIC ULTRASOUND - INDICATION ¢Myofacial pain dysfunction sy ¢TMJ diseases ¢Sialolitotrypsis (extracorporeal shock wave - ESWL) ¢Algic syndromes, bone healing ¢It inhibits the release of inflammatory mediators from the cells ¢Accelerates healing ¢Increases the elasticity of collagen fibers ¢Reduces joint stiffness ¢Reduces muscle spasms, improves mobility ¢ ¢ Prospective utility of therapeutic ultrasound in dentistry—Review with recent comprehensive update, Shalu Rai, Mandeep Kaur, Shailly Singh, Adv Biomed Res. 2012; 1: 47. ¢Ultrasound dental descaler - tartar removal. ¢ ¢It is a device with a source of low-frequency ultrasonic waves (25-42 kHz), the end of which is equipped with a working extension. The tip of the extension vibrates and mechanically disturbs dental plaque. ¢ ¢However, in addition to the direct mechanical effect of the oscillating tip, effect of ultrasonic cavitation is also involved. http://pimg.tradeindia.com/00152947/b/0/Ultrasonic-Scaler.jpg http://img.tfd.com/mosby/thumbs/50021X-fx7.jpg THERAPEUTIC UZ - CONSERVATIVE THERAPY THERAPEUTIC ULTRASOUND - DENTAL DESCALER ULTRASOUND OF SALIVARY GLANDS Cysts http://www.ultrasoundcases.info/files/Jpg/52758-Afbeelding1.jpg Pleomorf adenoma http://images.radiopaedia.org/images/933307/9eec828b2f32f6c32a00b6a2d9a1ed.jpg Sialolithiasis ADVANTAGES OF ULTRASOUND EXAMINATIONS ¢safe, cheap and affordable method ¢ ¢there are practically no contraindications ¢ ¢accessibility at the patient's bed ¢ ¢significant spatial resolution ¢ ¢Doppler option, flow display, blood circulation ¢ ¢ ¢ ¢ultrasound examination with i.v. application of special contrast media ¢microbubbles stabilized by phospholipid ¢100 million x higher soundwaves reflection of microbubbles than of blood. CEUS cévaSF6krvinky • nontoxic • no special patient preparation is required • there are no allergic reactions • is excreted after about 10 minutes with lungs • only contraindication: AIM • Pure intravascular contrast agent POSSIBILITY OF QUANTIFICATION C:\Documents and Settings\Administrator\Dokumenty\PREZENTACE od 2010\CEUS\DANAY\LIVER\FNH\FNH 2 Quantification.jpg DISADVANTAGES, LIMITATIONS OF ULTRASOUND ¢number of artifacts ¢ ¢subjective examination ¢ ¢limited investigability in non-cooperating patients MAGNETIC RESONANCE MAGNETIC RESONANCE ¢Hydrogen nuclei (1H) have a magnetic behavior ¢We use a strong magnetic field (0,2-2T) ¢radiofrequency pulses - a resonance of frequencies - transfer of energy - 1H raising from lower to higher energy states ¢signal from protons = from the pacient body - induction of a current in a receiver coil - computer reconstruction - resulting image DISADVANTAGES OF MRI ¢Strong magnetic field! (whole patient is placed in) ¢duration of examination - untill 60 min. ¢limited examination space ¢the price = availability ¢limited examination field (brain + Csp., C+Th, Th+L) BENEFITS OF MRI ¢Noninvasive technique ¢unprecedented soft tissue contrast ¢arbitrary plane of cross-section ¢MR angiography, ERCP, PMG (without a contrast medium) ¢contrast media - Gd (minimal risk of allergic reaction) CONTRAINDICATIONS OF MRI ¢ABSOLUTE ¢presence of magnetic metallic implants in otbit or intracranialy ¢Magnetic implante in other location shorter than 6 weeks after implantaion ¢pacemaker/ICD ¢ ¢RELATIVE ¢claustrophobia ¢non-cooperative patient ¢I. trimestr of pregnancy MR PRINCIPLES ¢Nuclear magnetic resonance (NMR) is a non-invasive means of obtaining clinical images and of studying tissue metabolism in vivo. Bloch and Purcell independently discovered NMR in 1946. Six years later they were awarded the Nobel Prize for their achievements. Since then, the development of NMR spectrometers and NMR scanners has led to the opening up of whole new branches of physics, chemistry, biology and medicine. ¢ Achievements - úspěchy ¢Nuclei with an odd number of protons and neutrons possess a property called spin. In quantum mechanics spin is represented by a magnetic spin quantum number. Spin can be visualised as a rotating motion of the nucleus about its own axis. As atomic nuclei are charged, the spinning motion causes a magnetic moment in the direction of the spin axis. This phenomenon is shown in figure. The strength of the magnetic moment is a property of the type of nucleus. Hydrogen nuclei (1H), as well as possessing the strongest magnetic moment, are in high abundance in biological material. Consequently hydrogen imaging is the most widely used MRI procedure. ¢ A charged, spinning nucleus creates a magnetic moment which acts like a bar magnet (dipole). Odd - lichý consequently - následkem (toho) ¢The first step in creating a magnetic resonance image is placing the subject in a strong magnetic field. ¢ shim - destička pro nastavení vůle shim - kotouček pro nastavení vůle shim - vymezovací podložka shim - vyrovnávací podložka ¢Presence of a strong magnetic field causes the nuclear spins of certain atoms within the body, namely those atoms that have a nuclear spin dipole moment, to orient themselves with orientations either parallel or antiparallel to the main magnetic field (Bo). ¢ ¢A collection of 1H nuclei (spinning protons) in the absence of an externally applied magnetic field. The magnetic moments have random orientations. (b) An external magnetic field B0 is applied which causes the nuclei to align themselves in one of two orientations with respect to B0 (denoted parallel and anti-parallel). ¢ align - seřadit denoted - označený (mat.) ¢The spin axes are not exactly aligned with B0, they precess around B0 with a characteristic frequency ¢(a) In the presence of an externally applied magnetic field, B0, nuclei are constrained to adopt one of two orientations with respect to B0. As the nuclei possess spin, these orientations are not exactly at 0 and 180 degrees to B0. (b) A magnetic moment precessing around B0. Its path describes the surface of a cone. ¢ ma2 constrained - nucený ¢The nuclei precess about Bo with a frequency called the resonance or a Larmor frequency. ¢Because the parallel state is the state of lower energy, slightly more spins reside in the parallel configuration, creating a net magnetization represented by a vector M. A collection of spins at any given instant in an external magnetic field, B0. A small net magnetisation, M, is detectable in the direction of B0. instant - chvíle reside - spočívat v (o moci) reside - sídlit reside - zdržovat se (bydlit); kniž. ¢Magnetic resonance occurs when a radiofrequency pulse , applied at the Larmor frequency, excites the nuclear spins raising them from their lower to higher energy states. Classically this can be represented by a rotation of the net magnetization, ¢ away from its rest of equilibrium state. frame - koncipovat frame - konstrukce (nosná) frame - konstruovat frame - kostra (stavby, stroje, lodi apod.) After a 90 degrees RF pulse, M lies in the x-y plane and rotates about the z-axis. The component of M in the x-y plane decays over time. An alternating current is induced in the receiver coil. ma3 ma4 ma6 ma7 ¢Once the magnetization is deflected, the RF field is switched of and the magnetization once again freely precesses about the direction of Bo. ¢This time dependent precession will induce a current in a receiver coil. ¢The resultant exponentially decaying voltage, referred to as the free induction decay (FID), constitutes the MR signal. After a 90 degrees RF pulse, M lies in the x-y plane and rotates about the z-axis. The component of M in the x-y plane decays over time. An alternating current, shown in Figure (b), is induced in the receiver coil. deflect - odchýlit (se) deflect - odklonit (se) ¢During the period of free precession the magnetization returns to its original equilibrium state by a process called relaxation which is characterized by two time constants, T1 and T2. T1 and T2 depend on certain physical and chemical characteristics unique to tissue type, therefore contributing substantially to the capability of MRI to produce detailed images of the human body with unprecedented soft tissue contrast. therefore - proto (tedy) therefore - pročež contribute - přispívat substantially - podstatně RECONSTRUCTION OF MR IMAGE ¢How do we make the voxels (volume elements)? ¢How do we know, from which part of the body cames the signal, how we make the final image? ¢Complex and complicated process, we need a physical and mathematical device Device - aparát, prostředek, deviza ¢ Slice Selection ¢The first step is the selection of a slice, which is achieved by applying a magnetic field gradient along the z-axis (Gz) during a 90o rf pulse of a specific frequency bandwidth (period 1 of Figure 9.7). When the slice select gradient, Gz, is applied along the z-axis,the resonance frequencies of the protons become linearly related to position along the z-axis. Individual resonance frequencies correspond to individual planes of nuclei. ¢ bandwidth - vnímací schopnost; hovor. hanl. bandwidth - šířka pásma ¢ Frequency Encoding ¢After slice selection, the next task is to distinguish signal from different spatial locations within this slice. This is accomplished in the x-direction by applying a gradient (Gx), the frequency-encoding gradient, during the acquisition of the signal. (time period 3 in Figure 9.11). The sequence of RF power and gradient ampitudes used to excite one slice and encode the positions of the spins within that slice into the signal. In this “frequency encoding,” the positions of the spins encoded by applying a magnetic field gradient in one of the directions in the excited slice during the acquisition. accomplished - dokonalý accomplished - hotový A series of steps illustrating the concept of frequency encoding to distinguish the signal coming from two point sources of magnetization, e.g. small vials of water, in an object.(left) When no gradient is applied, both sources of magnetization resonate at the same frequency and the signal is a simple decaying sinusoid. When this signal is Fourier transformed, the signal is shown to contain only one frequency.(right) When a gradient is applied, one of the sources of magnetization precesses at a higher frequency than the other. The resulting signal is an interference pattern of the two frequencies and is shown to contain by Fourier transformation to contain two distinct frequencies. Notice that the Fourier transformed signal is the projection of the amount of magnetization along the axis along which the gradient was applied. That is, in this one dimensional case, the frequency content of the signal is the image. vial - ampulka (lahvička) pattern - obrazec Spatial locations of the spins are encoded into the signal by applying three orthogonal gradients, techniques that are called slice selection, frequency encoding, and phase encoding. In period 1, a 90 degree pulse and a slice selection gradient excite one slice. In period 2, the initial frequency encoding gradient and the phase encoding gradient are applied. In period 3, a 180 degree pulse is applied, along with a slice selection pulse (such that only the spins in the same excited slice are “flipped,”) and in period 4 the frequency encoding gradient is applied and the signal is acquired. The sequence shown here is repeated numerous times (128, 256, 512, etc. depending on the desired resolution) each time with a different strength of the phase encoding gradient. A complete pulse sequence diagram for the spin echo sequence. ¢Although the signal obtained from one acquisition (slice selection, phase encoding and frequency encoding) contains information from all voxels in the imaging slice, the information gathered from one iteration of this sequence is not sufficient to reconstruct an image. Consequently, the sequence has to be repeated with different settings of the phase-encoding gradient Gy. ¢To construct a 256 x 256 pixels image a pulse sequence is repeated 256 times with only the phase encoding gradient changing. ¢A Fourier transformation allows phase information to be extracted so that a pixel (x, y) in the slice can be assigned the intensity of signal which has the correct phase and frequency corresponding to the appropriate volume element. The signal intensity is then converted to a grey scale to form an image. ¢ ¢ MR AND METALLIC DENTAL MATERIALS ¢Different grade of artifacts according to the material used ¢ ¢It depends mainly on material susceptibility (pronounced in amalgam, titanium, less nickel-chromium or cobalt-chromium) ¢ ¢So if it can be removed, then take off before the examination MR IN STOMATOLOGI ¢The most common use is in temporomandibular joint diseases —Pseudodynamic sequences are used — ¢Ameloblastoma ¢Osteomyelitis ¢Dif.dg. Cystic lesions ¢Range of hemangiomas, spread of tumors in general ¢Localization of the neurovascular bundle before planning potential sites for implants DISEASES OF THE TEMPOROMANDIBULAR JOINT ¢dysfunctional syndrome ¢inflammatory and degenerative changes ¢iatrogenic lesions (repeated injections of steroids) ¢M. Paget ¢Gout ¢Tumors ¢osteochondritis dissecans (avaskular necrosis) ¢Pigmented vilonodular synovitis ¢Ancylosis of TMJ ¢Hyperplasis of processus coronoideus INTRACAPSULAR DISEASE = DISCOPATHY ¢Discus artikularis – an important part of the temporomandibular joint ¢Disc – biconcav fibrocartilage structure dividing the joint into the upper and lower compartments ¢The correct position prevents damage to the mandible ¢The movement of the disc is limited by a strong rear ligament ¢Dorsal part - neurovascular structures = retrodiscular tissue (bilaminar zone) ¢ DISKOPATHY ¢ ¢due to the pathological location of the articular disk or the adhesion of the disc ¢ ¢disc dislocation with reposition::the disk is dislocated at rest (most often anterior to the joint head), in the movement is repositioned, asymmetric opening, sound phenomena (most often in the sense of clicking), eventually. with the presence of pain. There is no limitation of opening mouth ¢ ¢disc dislocation without repositioning:: ¢ the disk is dislocated, but it does not reposition, the movement of the joint is so limited. In addition to limited opening, pain may be present, but no sound phenomena are present. ¢ ¢Adhesion of intraarticular disc: ¢ the disk is at rest in the correct, physiological, position, however its mobility is limited. The reduction of the opening of the mouth is characteristic. ¢ ¢ MRI PSEUDODYNAMICLY 18 YEAR OLD PATIENT WITH DD WITH REPOSITION Zavř 2 Otevř 2 sono1 def Sono2 def 17 YEAR OLD PATIENT WITH DD WITHOUT REPOSITION Zavř 2 Otevř sono 1 zavř DWI – DIFFUSION-WEIGHTED IMAGING ¢Diffusion - Random movement of water molecules in the tissue (Brown's motion) ¢ ¢The degree of diffusion often differs between individual tissues or between healthy and pathological tissues ¢ ¢The MR imaging of diffusion adds additional diagnostically valuable information. obr4 Diffusion imaging in different directions DTI –DIFFUSION TENSOR IMAGING ¢Method based on DWI principles ¢ ¢ ¢Anisotropy of diffusion in the white matter of the brain and spinal cord: the movement of water molecules proceeds more easily along the nerve fibers ¢ ¢The intensity of the DWI image signal depends on the direction of the additional magnetic gradient used ¢ ¢By repeated measurement with different diffusion directions we can detect the dominant direction of diffusion → the course of the nerve pathways DTI FIBERTRACKING: GLIOMA GR. II Tractus corticospinalis Fasciculus arcuatus PCA: CSF CIRCULATION MEASURMENT MR kontrola FUNKČNÍ MR 40545_2_1500 •It enables the resolution of active and inactive brain tissue regions by detecting changes in deoxyhemoglobin concentration occurring during activation • • Measurement is performed repeatedly at rest and during activation - the patient performs some specific action Neurosurgery - Preoperative mapping of the location of important centers 11 1)The figure on the left shows the situation before the operation: The speech center activity during the verbal test is located in the immediate vicinity of the tumor mediodorsally 2)In the figure on the right, a postoperative state is visible: The activity area during the speech center remains intact near the bed after tumor resection. No verbal function deficit was found in the patient after surgery. www.fmri.org POSSIBLE APPLICATIONS FMRI CASE – MEN *1979 ¢Personal anamnesis: hypertension, smoker ¢ ¢Before two weeks purulent pouch in the oral cavity, self-emptying, since then but chills. ¢ ¢ now a few days of headache ¢ ¢For headaches and prefrontal syndrome examined for CT CT MR T2 T1 DWI T1 + contrast DG. ¢Brain absces ¢He underwent neurosurgical evacuation Thanks for your attention