1! Panoramic Imaging Panoramic Imaging !!Or pantomography !!Extraoral technique - Image receptor and source are located extraorally !!Digital Image receptors (sensors or photostimulable PSP plates) or indirect exposure conventional film is used !!Single tomographic image of the facial structures including maxillary & mandibular dental arches & the supporting structures Patient Positioning ?!Mid sagittal plane light ?!Canine light (should be on mesial of maxillary canine) ?!Horizontal plane light Bite block Horizontal plane: Frankfort plane: lower border of orbit & sup. point of tragus Or tragus to outer canthus of eye Panoramic Imaging !! Reciprocal movement of Image receptor & x-ray source around a central point or plane called image layer in which object of interest is located !! Image receptor & x-ray source move simultaneously but in opposite directions during exposure !! Shadows of superimposed structures are blurred out to show the area of interest more clearly Panoramic Imaging Advantages: !!Convenience; simple to perform !!Broad anatomical coverage !!Low patient dose (dose equivalent to 4 BW) !!Short Imaging time (<3-4 min including patient preparation time and infection controls steps) !!Readily available in most dental offices 2! Panoramic Imaging Advantages: !!Useful as initial screening tool !! For treatment planning, dental anomalies, trauma, etc. !!May provides insight or assist in determining the need for other projections !! Minimal infection control procedures required !! Well accepted by patients - patient education Panoramic Imaging Disadvantages: !! Lack of fine anatomical detail !! Lesser detail & definition than periapical images !! Should not be substituted for periapicals !! Overlapping of the structures !! Premolar interproximal surfaces !! Magnification (20 - 30 %) and distortion of structures !! Initial expense is more Panoramic Imaging Disadvantages?. !!Patient positioning is important !!Artifacts, ghost images !!Incorrect interpretation Image formation If patient positioning is NOT correct, following problems will result with both conventional & digital machines: !!geometric distortion, magnification, elongation, ghost image formation, superimposition of structures, overlap, left- right size variations X-ray Beam !!A narrow vertical beam (-7 to -10°) rotates in a horizontal plane around a rotation center. Rotation center is invisible and positioned intraorally Conventional Beam Narrow Vertical Beam Lead collimator with vertical slit F ! Conventional PA Technique! Panoramic Technique! Negative Vertical Beam Angulation (-7 to -10 degrees) 3! Center of rotation is located off to the side, away from the object being imaged During the cycle, the machine automatically shifts one or more rotation centers Rate of movement of the receptor is regulated to be the same as that of CR sweeping through the structures nearest the receptor Most machines have continuously moving rotation centers Some points?.. !!Only structures near the image receptor are usefully captured on the resultant image !!Structures near the x-ray source appear diffused or blurred or ghost-like! Rotograph: single rotation center Panorex: one or two rotation centers (split image) Orthopantomograph model OPI : three rotation centers (continuous image) Penelipse, Versaview: continuous image utilizing a continuously sliding rotation center Orthopantomograph model OP2 & OP3 & Cranex: continuous image utilizing a combination of stationary & moving rotation centers Panorex F ! D ! Stationary source compared ! with moving source! Combination of moving Image receptor and! Rotating beam! 4! If a rotating narrow beam is used with a stationary image receptor: !!magnification in the horizontal direction would be greater than that in vertical dimension !!Therefore, a moving Image receptor is used to equalize the magnification Focal trough / image layer: !! Zone of sharpness !! A 3-dimensional curved zone or image layer in which structures are reasonably well defined !! Vertical & horizontal magnification will only match if object lies within the central plane of the focal trough !! Objects outside the focal trough are not sharp and appear fuzzy on the radiograph !!Focal Trough : !!Objects outside the focal trough may be blurred, magnified, or reduced in size. !!All machines produce a focal trough that approximates the shape of the jaws Width of focal trough / image layer depends on: !! Directly related to the distance from center of rotation to central plane of image, which is called ?effective projection radius.? !! The longer the radius, the thicker the image layer. !! Layer thickness is inversely proportional to the width of the long narrow slit beam. !! The narrower the beam, the wider the image layer. The longer the radius, the wider the image layer The narrower the beam, the wider the image layer Width of the image layer (Radius = distance between rotation center & center of image layer) (Narrow collimator width) 5! Various shapes of the focal trough or ! image layer:! ?!Narrow in anterior region, ! ?!Thicker in posterior region! ?!Image layer is shaped to center the jaws and adjacent structures within its boundaries! Adjustable Focal trough: !!Some companies now have software programs that enable the units to have adjustable focal troughs !!Optimized for all anatomical conditions !!Adjustable to fit patient?s arch form Bite Block & Notch Image Analysis: is the object in the ! focal trough or not?! B L !!When object is displaced to the lingual side of the focal trough, towards the source, the beam passes more slowly through the object compared with the Image receptor speed and the structure is elongated horizontally on the Image receptor Positioned too far back !!When the object is displaced towards the buccal aspect of the focal trough, closer to the Image receptor, the beam passes at a faster rate through the structures,and the structure is horizontally compressed. !!There appears to be more vertical magnification Positioned too far forward 6! Principles of Panoramic Imaging Magnification in Panoramic images: !! Certain degree of magnification in all images (25% - 30%) !! Varies from machine to machine !! Must take into this into account when making measurements !! Varies with position of objects in the arch and in the focal trough Concepts of Normal Panoramic Anatomy Panoramic Anatomy Concept 1: !!Jaws, maxillofacial structures and spines are imaged as if they were split vertically in half down the midsagittal plane with each half folded outwards !!Nose remains in middle & right & left sides of jaws are on each edge of the Image receptor Concept 1: Structures are flattened and spread-out !!Mandible, nasal turbinates & meati, zygomatic arch, maxillary sinuses, hard palate and mandibular canal Concept 1: Structures are flattened & Spread-out! Maxillary sinuses Hard palate & floor of nasal fossa Nasal Septum Mandibular canal Body of the mandible 7! Concept 1: Structures are flattened & Spread-out! Zygomatic arch Nasal turbinates & meati Zygomatic arch Mandibular canal Mandibular foramen Mental Foramen Mental Ridge or protuberance Lingula Zygomatic arch Nasal concha, turbinates & meati Zygomatic arch Concept 1: Structures are flattened & Spread-out! 8! Sigmoid notch Condyle Articular eminence & Glenoid fossa Coronoid process of mandible Sigmoid notch Mastoid process Cervical spine Concept 1: !!Undesirable if patient is positioned incorrectly in the machine !!Certain structures would be flattened & spread out although they normally would not be e.g. Hyoid bone & inferior turbinates meati of nose Posterior wall of max. sinus Zygomatic process of maxilla Anterior nasal spine Pterygomaxillary Fissure Infraorbital rim Posterolateral Wall of max. sinus Medial wall of max. sinus Inferior border of max. sinus Malar process 9! Infraorbital canal Styloid Process Stylo-hyoid ossicles Coronoid process Infraorbital canal Ethmoid sinus Styloid Process Anterior nasal spine Cervical spine Infraorbital Rim Articular eminence & Glenoid fossa Coronoid process of mandible Sigmoid notch 10! External oblique ridge Internal oblique ridge Genial tubercles & Lingual Foramen Concept 2: Formation of real images (single & double) Formation of ghosts (single & double) Concepts of Panoramic Radiology Concept 2: Real images form when the object is located between the rotation center of the beam & the Image receptor Concept 2. ! Formation of ! Double Real Images ! Rotation Center X-rays Rotation Center X-rays 11! Concepts of Panoramic Radiology Concept :2. ! Region where Real Images ! Form (vertical hatch marks)! Real Double images form in the central diamond-shaped area (objects are intercepted by the beam twice)! Concepts of Panoramic Radiology Characteristics of Double Images: !! One image is mirror image of the other !! Both images are real images !! Each image will have the same proportions & same location on the opposite side !! Double images only occur with midline objects falling in the diamond-shaped zone in the midline Double Real Images are normally formed by: Hard & soft palate Palatal tori Body of hyoid bone Epiglottis Cervical spine Real Double Images! Hard palate Floor of nasal cavity Ghost formation soft palate Real Double Images! Hyoid bone Real Double Images! Cervical spine - real image 12! Epiglottis Hyoid bone Epiglottis GHOST IMAGES! Concept 3: Ghost Images are Formed !!Form when the object is located between the x-ray source and center of rotation or the object is behind the rotation center. Concept 3.! Region where Ghost Images ! Form, Shown by horizontal ! hatch marks! Concepts of Panoramic Radiology Characteristics of ghost images: !!Same general shape as its counterpart-No mirror image formation !!Formed on the opposite side !!Appears to be higher on the Image receptor than the real counterpart !!Blurred and magnified - vertical component more blurry and enlarged than horizontal component 13! Structures that generally form ghost images on panoramic Image receptors: !! Cervical spine !! Horns of hyoid bone !! Ramus of mandible !! Hard palate !! Neck chains, ear rings, necklaces, markers Ghost image of inferior border of the mandible from the opposite side Ghost image of cervical spine Ghost image of inferior border of the mandible HP Floor NF Ghost!!! Ghost image of hyoid bone Real image of hyoid bone Ghost image Real Image 14! Concept 4: Soft tissues are seen !! Some soft tissues attenuate the beam to sufficient degree to become visible on radiograph !! Examples: posterior & superior edentulous regions, fluids, cartilaginous tissues like nose ear and epiglottis, soft palate & uvula, dorsum of tongue, lips, nasolabial fold, soft tissues of turbinates and septum, posterior pharyngeal wall and palatine tonsils Soft tissue of ear Styloid process Soft palate Dorsum of tongue Ear lobe or auricle Styloid process Epiglottis Hyoid bone Lip outline Soft palate Soft tissue of neck Concept 5: Air spaces are seen !!Air does not attenuate x-ray beam !!Air spaces appear black !!Air spaces include: !!nasopharyngeal !!oropharyngeal !!palatoglossal !!hypopharynx, maxillary sinus, nasal fossa, 15! Nasopharyngeal sir space Oropharyngeal air space or Glossophsryngeal air space Palatoglossal air space Nasopharyngeal sir space Oropharyngeal air space Air Spaces Oropharyngeal air space Nasopharyngeal sir space Palatoglossal air space Concept 6: Relative Radiolucencies & Radiopacities seen !! Machine & patient components may produce single or / and double real images and / or ghost images !! Multiple areas of relative density changes are produced Styloid process Ghost image of Hyoid bone Hearing Aid 16! Concept 6: To understand and separate multiple density changes , remember: !!Air obscures hard tissues !!Soft tissues obscure air !!Hard tissues obscure soft tissues !!Ghost Images obscure everything! Concept 7: Panoramic images are unique !!Helpful in assessment & interpretation !!Broad anatomical coverage !!Depict angular interrelationships of structures !!Excellent projection of variety of structures on single Image receptor Farah Masood Panoramic Imaging Theory I
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