1 Tomography, CT, MRI, Sialography, and Ultrasongraphy 2 It is radiographic technique designed to image more clearly objects lying within a plane of interest. This is accomplished by blurring the images of structures lying superficial and deep to the plane of interest through the process of motion unsharpness. 3 As the x-ray tube move from Lt to Rt the film moves in the opposite direction. The focal plane is the most clear area. 4 1-the physical location of the fulcrum within the object to be imaged. 2- Tomographic movement. 3-Tomographic angle or arc. 5 Linear Circular Elliptical Hypocycloidal Spiral 6 A ) mandibular tomogram B) maxillary tomograms in premolar region (dome shaped opacity in the floor of maxillary sinus) 7 A B Disadvantages of linear tomography Parasite lines. Inconsistent magnification Dimensional instability Non uniform density. 8 Tomographic layer is the thickness of tissue in the focal plane. It is determined by the position of the fulcrum and its width by tomographic angle or arc. Wide angle tomography. The tomographic angle is more than 10 degree Produce images of reduced contrast. Tissues of greater physical density as bone is imaged 9 Complex movements result in maximal blurring of the images of objects lying superficial and deep to the focal plane of focus the streaking parasite lines are therefore absent 10 Uses an angle of less than 10 degree, it is called zonography. Thickness of tissue up to 25mm is sharply imaged It is useful when subject contrast is low 11 The thick plane of focus allowed the supernumerary tooth and adjacent permanent teeth to be imaged clearly in one depth of the field. The diagnostic value of these images is increased by their having been steroscopically, allowing for localization of supernumerary tooth relative to clinically erupted teeth 12 The tomographic angle is more than 10 degree Allow visualization of fine structures which that normal obscured by superimpositions in conventional radiography. Disadvantages Produce images of reduced contrast. Subject contrast results partly from the different thickness of adjacent structures. Wide angle tomography reduce these difference by the thinness of its cut. Application of wide angle tomography Tissues of greater physical density as bone is imaged. As evaluation of maxilla and mandible before implant placing. 13 It is a technique that uses a narrowly collimated, fan shaped beam of irradiation to scan an area of interest. It demonstrate higher contrast with perception of greater details. 14 This view demonstrates higher contrast and greater detail. The diagnostic value of such images is increased by their having been steroscopically, which allows for the perception of depth. 15 Dr. maha Eshaq Amer16 Limitation of conventional radiography 1- Super imposition. 2- Qualitative rather than quantitative. Limitation of conventional Tomography 1- Image blurring 2- Degradation of image contrast 3- Magnification of screen film combination 17 1-CT minimize the problem of superimposition. 2-Improving the contrast of the image. 3-Finding a way to record very small difference in tissue contrast by: A beam of x-rays is transmitted through a specific cross section of the Pt. The beam of x-ray is highly collimated into a thin beam that only passes through the cross section The x ray beam strikes special detectors that they are quantitative. 18 Data acquisition Collection of data by either slice by slice or volume data acquisition. Relative transmission =log Io/I Data processing Raw data undergo some form of preprocessing Conversion of transmission measurement into CT images Each pixel is assigned CT number related to linear attenuated coefficient Image display Relation between CT number and brightness is referred to as windowing Storage and documentations 19 A finally collimated fan x-ray beam is directed to the series of scintillation or ionization chamber. Both the radiographic tube and detectors rotate synchronously around the Pt The CT image is reconstructed by the computers which mathematically maniputes the transmission data obtained from multiple projections 20 The x-ray tube and detectors are in perfect alignment. the x-ray tube and detectors move around the Pt to collect a large number of transmission measurement. As the beam leave the tube it is shaped by a filter. The beam is collimated to pass through only a slice of interest. The beam is attenuated by Pt and the transmitted photons is measured by detectors. The detectors convert the photon into electrical pulse (analog). The electrical signals converted into digital by ADC The digital data are sent to the computer for processing 21 Data for a single plan image is acquired from multiple projection made during the course of 360 degree rotation around the Pt. The single plane image is constructed from absorption characteristics of the subject and displayed as a differences in optical density ranging from to The CT is recorded and displayed as a matrix of individual blocks (voxel ) each square of image matrix is a pixel. The size of pixel (0.1 mm) is determined by computer program used to construct the image. The length of the voxel (1 to 20 mm) is determined by width of x ray beam, which is controlled by pre-Pt and post Pt collimators. Each pixel is assigned CT number representing density. The number is proportional to the degree to which the material within the voxel has attenuated the x-ray beam. 23 The absorption measurement range in CT expressed in HU is referred to as the ww. It determine the maximum number of shades of gray that can be displayed on the CT monitor. The CT number range from-1000 to As ww the contrast . contrast is optimized with medium ww WL is the middle of ww 24 25 26 27 28 29 1-Sella tursica, 2-temporal horn of lateral ventrical, 3- mid brain, 4-fourth ventrical, 5-cerebellum 30 1- Lt cerebellum, 2-tentorum cerebelli, 3- insular cortex, 4-fourth ventricle, 5- Lt frontal lobe, 6-falx cerebi 31 1-Caudate nucleus, 2-lateral ventricle, internal capsule limbs 3-anterior, 4 posterior 5-Lentiform nuclei 6-Third ventricle. 7-fourth ventricle, 8-corpus callosum 32 1 Lt max antrum, 2 nasopharynx, 3-spinal cord, 4- odontoid processC2, 5-mastoid air cells, 6- masseter muscle, 7-MD, 8-zygomatic bone, 9-lateral pterygoid muscle, 10-trapezius 33 1-Lt Ms. 2-Nasopharynx. 3-spinal cord, 4- odontoid process, 5-mastoid air cells, 6-masseter muscle, 7-MD, 8-zygomatic bone, 9-lat Pterygoid muscle, 10- trapezius muscle 34 1-medulla, 2-clivus, 3-condyle, 4-zygomatic arch, 5- temporal muscle, 6-sphenoid sinus, 7- external auidatory meatus. Foramen magnum arrow head 35 1-Rt eye, 2-sphenoid bone, 3-cerebulum, 4-internal auidatory meatus. 5-nasal cavity 6- Rt temporal fossa. 7-Rt medial rectus muscle. 36 1-Sphenoid sinus, 2-temporal lobe, 3-clivus, 4-mastoid air cell, 5- cerebellum, 6- fourth ventrical, 7- internal occipital protuberance 37 Dr. maha Eshaq Amer38 It is radiographic demonstration of major salivary gland by introducing a radiopaque contrast medium into their ductal system. Procedure I-Pre operative phase: A-Preliminary pre- operative radiography. B- Preparation of the patient. II-Filling phase: 1. Exploration of duct orifice. 2. Dilatation of the duct by lacrimal probs. 3. Canuula is inserted into the dilated duct and connected with syringe which contain the contrast media. 4. Injection is performed slowly until the Pt fill fullness 5. The filling phase radiograph is taken. 39 III-Emptying phase The cannula is removed and gland is stimulated to excretion by massaging while salivary flow is Stimulated by sucking lemon. After 5 min the emptying phase radiographs is taken. One hour later, other radiographs are taken. 40 They must posses sufficient radiopacity to provide good delineation of the anatomic structures. It must have proper viscosity, not very high as need more pressure, not very low as it will escape the gland. It must be readily excreted from the gland. It must be non toxic, and non harmful. It must possess physiologic properties similar to those of saliva. 41 Water soluble contrast media: Have less radiographic density. Dissipate more quickly and are less irritating. E.example urografin and renografin Oil based contrast medium: Need higher injection pressure due to higher viscosity. Prolonged retention in gland with risk of allergic reaction. Have higher radiopacity Example lipidol, and pantopaque 42 I-Chronic inflammation of salivary gland (sialectasia ) this may be: A-Obstructive inflammatory due to calculi (sialolithiasis); strictures (constriction of the ductal wall near the orifice), or stenosis (construction of the ductal wall along the whole course of the main duct) B- Non obstructive inflammation : Due to autoimmune disease, or due to bacterial infection as acute suppurative parotitis, recurrent parotitis, or due to viral infections as mumps, or due to inflammation secondary to allergic reaction 43 II-Neoplasm of salivary gland. A-Extrinsic (normal architecture of the gland and its secretory function but deviation of the ducts due to external pressure of the tumor) B- Intrinsic which arise from the gland itself it can be benign or malignant as pleomorphic adenoma, Warthins tumors, mucoepidermoid carcinoma and cylindroma. III-Developmental disturbance of SG As Tracher collin syndrome, and Goldenhar syndrome. IV-Trauma of salivary gland Hemorrhage lead to hematoma lead to fibrosis lead to sialocele V- Metabolic diseases As diabetus mellitus 44 Allergy to compounds contained in contrast media. Period of acute inflammations. When preoperative radiograph shows calculus close to duct orifice. Pt performing thyroid function test using iodine-containing material 45 This lateral view demonstrates parenchymal blushing. Normal fine branching is visible. Lack of parenchymal blushing at the anteroinferior margin is caused by radiographic burnout. 46 A, Lateral projection of the parotid demonstrating opacification all the way to the terminal ducts and acini. B, Anterior-posterior projection of the same gland demonstrating "parenchymal blushing" from acinar opacification. 47 AB, Slightly oblique lateral view demonstrating parenchymal opacification of the submandibular gland. Arrowhead points to an obstruction (radiolucent sialolith) within the main duct. Opacification of the parenchyma is patchy resulting from fibrosis secondary to chronic obstruction. 48 Lateral view of submandibular glands demonstrating a radiolucent sialolith in the main duct. This is to be differentiated from inclusion air bubbles, in which the interface with the contrast media is convex. 49 Lateral view of the submandibular gland shows prominent intermittent stricture and dilation of the main and secondary ducts, which is typical of advanced sialodochitis. 50 A) Lateral projection demonstrates punctate sialectases distributed throughout the gland, which is suggestive of autoimmune sialadenitis. The "sausage-link" appearance of the main duct indicates that sialodochitis is present. B) A-P projection of the same gland. 51 A B Punctate (small spherical), globular (larger spherical), and cavitary (larger, irregular) sialectases with some dilation of the main duct are suggestive of advanced autoimmune disease with parenchymal destruction with retrograde infection in lateral (A) and AP ( B ) projections. 52 A B Sialogram of left parotid gland (AP view). A mass within the gland is inferred by the appearance of the ducts displaced around the lesion. This is referred to as the "ball-in-hand" appearance, which is suggestive of a space occupying mass. 53 Dr. maha Eshaq Amer54 MRI A hydrogen nuclei in an external magnetic field. most nuclei are in lower energy state and are aligned parallel with magnetic field. B the axis of spinning protons ossilate with slight tilt from being absolutely parallel with the flux of the external magnet. 55 A B 1-Precession. The tilting of the spinning hydrogen nuclei around the direction of the external magnetic field. The rate of precession is resonant or Larmor frequency. 2-Spin up and spin down The combined effect of spinning up and spinning down energies state is a weak net magnetic momentum, (MV) parallel with applied external magnetic field. When RF is directed to tissues with H2 nuclei that are aligned in z axis by external static magnet field, the proton in the tissues that have Larmor frequency matching that of RF absorb enrgy and shift from the direction induced by imaging magnet. 57 Repetition time (TR) is the time between the excitation pulses. Echo time (TE) is the time between last excitation and echo. T1 and T2 are the relaxation time, it will determine the relative densities of different tissue on the final image. T1-weighted image is produced with short TR and TE tissues as fat appear bright while tissues with high water content as CSF, and cyst appear dark. T2-weighted image is produced with long TR and TE tissues as CSF, cysts, necrotic LN appear bright and muscles appear dark 58 Indication Tumor staging evaluation of the size, site, and extent of soft tissue. Investigation of TMJ to show hard and soft tissue components of the joint. Assessment of intra- cranial lesion. Advantages Not using ionized radiations High resolution images. Excellent differentiation between soft tissue Metallic restoration do not produce artifact. Disadvantages Cortical bone is not imaged Scanning time is long & very annoying to pt. Limited availability& expensive Pt with pacemaker cannot be imaged 59 A)T1 B) T2 C) proton denisty 60 AB C 61 A) Closed sagittal view showing the disk with its posterior band (arrow) anterior to the condyle. B) Open view showing the normal relationship of the disk and condyle and the posterior band of the disk (arrow). C, Coronal view showing the disk (white arrow) laterally displaced. The joint capsule (black arrowhead) bulges laterally. 62 A well-defined mass in the deep lobe of the right parotid gland as imaged with coronal Tl-weighted format (A) and axial T2-weighted format (B). The tumor (arrows) is low-signal on the Tl-weighted image and high-signal on T2-weighted images. Histopathologic diagnosis was benign mixed tumor. 63 Dr. maha Eshaq Amer64 US Sound is a result of periodic changes in the pressure of air against the ear drum. Audible sound is 15 to 20 KHz while ultrasound used in diagnosis from MHz. Transducer is device used to convert electric current into ultra sound and vice versa. As US pass through tissue or interact with tissues of different acoustic impedance, it is attenuated by a combination of absorption, reflection, refraction and diffusion. Sonic waves that are reflected back (echoed) to the transducer in turn produce electric signal that is amplified, processed, and displayed on a monitor. 65 Examination of SG Examinations of swelling of the neck including LN and thyroid gland. Examination of maxillary sinus. It is sometimes used to locate the apex of the root. Assessment of blood flow in the carotid artery thus aiding in the detection any aneurysm, stenosis, or thrombosis of the carotids as well as carotid body tumors. 66 Advantages 1-Sound waves are not ionizing radiation 2-Show good differentiation between soft tissues. 3-Shows good differentiation between soild and cystic lesions 4- widely available and inexpensive Disadvantages 1-limited use in head and neck because sound waves are absorbed by bone. 2-technique is operator dependent. 3-images are difficult to interpret for inexperienced operators. 67 Parasagittal image of TMJ area showing the articular disk in its normal position superior to the condyle in the closed mouth position. Glenoid fossa (curved row), articular disk (long arrow), and condyle (short arrow) 68 well-delineated, solid mass is suggested by echo returns within the lesion. Ultrasound appearance is typical of a benign salivary tumor. 69 Echo-free mass with well-defined margins presents a typical cystic appearance. 70 The mass in the submandibular gland (arrowheads) demonstrates a heterogeneous hypoechoic pattern compared with the adjacent tissue. The histopathologic diagnosis was adenoid cystic carcinoma. 71 72