Projection Geometry 6 PDF

Ch. 6: Projection Geometry Pages: 238 – 256 By: Hussein Hilal, Majd Barham Date: 2023/10/01 1 8)> *. & ⑧..wa Altan 4 ⑧>8. ⑤ 2 Outline Introduction Image Quality Paralleling And Bisecting-angle Techniques  Eggshell Effect 3...

Ch. 6: Projection Geometry Pages: 238 – 256 By: Hussein Hilal, Majd Barham Date: 2023/10/01 1 8)> *. & ⑧..wa Altan 4 ⑧>8. ⑤ 2 Outline Introduction Image Quality Paralleling And Bisecting-angle Techniques  Eggshell Effect 3 Introduction Two-dimensional (2D) images are called plain or projection views & d : : Isn The entire volume of tissue between the x-ray source and the image receptor (digital sensor or film) is projected onto a 2D image receptor Source is 1,$1 :I I 3D volumetric structure / 5 2 :1812D & ! I : structure : ~ Dist The term image quality refers to the reliability of the image to represent the true state of the anatomic region examined & I Kiss 11 image quality. & se 8 , 1 es si ianatomical structure. 4 Image quality Parameters that define radiographic image quality include: o Image sharpness I o Spatial resolution Is I 9 o Contrast resolution - :. 1.. Parameters o Magnification image quality o Distortion 5 Image quality For optimal diagnosis, the radiographic imaging system should make an image that: /151861sa -> *31 , ▪ Has minimal magnification and distortion ▪ And with a contrast and spatial resolution that is adequate for the intended diagnostic task ↳ magnification b distortion Optimalagnosis ↑ + For spatial resolution adequate cantrast + 6 ↓ focal spot Principle for fab / / Objeal-receptor between them distance objed receptor parallel E +.. -> high image & Source - receptor distance quality Source X-ray beam 3 with object + receptor is perbendicat 7 Image Sharpness and Resolution Sharpness measures how well a boundary between two areas of differing radiodensity is revealed Dentin framel :. is Ess :. D5J : 2 different denstiess boundary all iss sad - s 6 Image spatial resolution measures how well a radiograph reveals small objects that are close together ↳ 259-6- fine details - I. - is -se small objects s - 1 &.... ↑ S. resolution e : -.. -iss : = Sharpness and spatial resolution are interdependent, being influenced by the same geometric variables Sharpness + S resolution ependent variables * ii optimal depends Same sharpness. on -> -$$) ~ optimization S. resolution variables 8 For intraoral images periapical j 23 technique - Long come  The paralleling technique is the preferred method for making intraoral radiographs intraoral is sad st - , I I * -360 1, /I objec [I receptor : + : = : - - with source :Sal : distortion s I - This technique seeks to minimize distortion by placing the image receptor parallel to the long axis of the tooth, and directs the central x-ray beam perpendicular to both the long axis of the tooth and the receptor  ↳ 51 938 : ! - Max anteriors ,. - 5. - : 188 receptor. - ▪ Limitations: - periapical ji. %1cervature --- Palate I objects is i s receptor /. Palate iss 29 is -s object 5 11 - 1. less , receptor %15) gas - : j - a. 24 - receptors object Position the image receptor toward the middle of the oral : ↑ magnification + ↓ sharpness cavity, away from the teeth, which increases the object to receptor distance and causes magnification and geometric unsharpness ? 5By s object Source is -. Dis -long : cylinder 9:14 holder - object receptor is paralleling & xs- ▪ Solution: To overcome this ▪ Use long open-ended aiming cylinder (“cone”) to increase the source-to-object distance ? Positions 5>- , : vertical i? I -"Anteriors' - receptors ▪ Use image-receptor holders 11 - s holder is - is receptor I#...... ob · , ect - " receptor &is be... interall I-....... &S.. bite.. -$15s+ cylinder - - receptor object a -> aiming // migin ring + + I. 6 j5 ring I mouth s source. cylinders - , b : 5 3 - external device E device d. bite -  S Paralleling lechneques) 31 8011 i - - full of teeth's receptor is : more interiorly coss: Palate. : Shallow Palate : I length I S : Palatal tori= hard Palates excessive bony Structure receptorie Sis : "dome shaped I · surface s receptor Six S , full layth % Lingual & s =. D , Is 3 st foreshotining Is ! it object & receptor & Elongation : is s distortion is. 50 -s : : distortion distortion si : P. " crest in alveolar line dis ? distortion is receptor is scid'ss Imaginar disector I imagary of tooth a axis. Long , - receptor ; - Source - ? holder Sa bisector - 1 : 3 - imaginary holder 10. receptor sit receptor ? receptor - jed - in receptor : : is 41 i 3. -: I bisedor is ~!? ! 3 & -. reference -sil is it -- - I - I've sales a e. s : Assessed I -5. 1 des id s Horizontal Plane floor s g : '. g -8 , Man I Max Si Post Si Ant.... "! ssils -  -  The bisecting-angle technique, -> Less frequently used 25 The image receptor is placed as close to the teeth as possible without deforming it, but not parallel to the long axes of the teeth This arrangement inherently causes distortion → Directing the central ray perpendicular to an imaginary plane that bisects the angle between the teeth and the image receptor  - 26 ▪ Limitations: Although the projected length of a tooth is correct, these images display a distorted image of the position of alveolar crest with respect to the cementoenamel junction of a tooth In recent years, the bisecting-angle technique is used less frequently for general periapical radiography as use of the paralleling technique has increased  -- -- 02 D s is 98 -. Object Localization of buccolingual area : it : ex 3D Structure -> seled 3D location a objec by- - : es 2D ! 2D ing es 27. An inherent limitation of plain radiography is the two-dimensional nature of the image For example, the dentist may need to determine the location of an impacted tooth, or a foreign object within the jaw 2D images - 3D Structur & $ occlusal view with periapical Planes iss 190D s:, is ↑ : 2D S A a ↳ : CBCT. CT  Examine two images projected at right angles to each other. 28 The clinician identifies the position of the object of interest relative to surrounding anatomic landmarks on both projections Occlusal view of Max arch of Max Periapical view. right anteriors or impacted unerupled fatss ego inte Palatal side - canine 13 in the Palatal side nu C 12 DP  Use the tube-shift technique employing conventional periapical views ① ② (buccal-object rule and Clark's rule) Sis i I 29 its is 1 , I ⑮ ③ -> ~ As 1 i stubes Shift SLOB: same lingual, opposite buccal - - l periapical view of Man Left.. Posteriors. , a receptors.. 3. s object's position is is horizentally s " ! -= 3581s D el U · D ! reference ? contact area &"3 *8 5 6 7 ⑧ Sin , swi - si - reference point iss -> lingual or buccal side radiopaque circle - -: re Point i ere reference Point Compare the positions of I the object in question on = - 11 is !59 ! apex Di 3501 , s: each radiograph with a el D & reference structure 4 3 5 Point 1 ? i s ⑤S- Shift 8 2 slis 5 reference !* is $ It : - or shift lubes shift sig i nal side git* j5jss - ~ : 6 receptor si Patient Shift o I -is li! * elesial buccal : elesial -I : Canines. $ Shift use -:I  " shift lecheque - + i teeth g is impacted teeth - supernumvary 30 roof canals 29 * Y 56 roof or 7 & : Shift ss0 Mesial - Distal - Superior Inferior shift ! Dis Si 'scanine.. I ? Mesial shift - 8 : el D 34 E 6 I reference Point -> - - distally ps shift o buccal sidee.. desial shift. : 31 Applications of the SLOB technique 1 -This technique assists in determining the position of impacted teeth, the presence of foreign objects, and identification of multiple pulp canals 2- The dentist may have two radiographs of a region of the dentition that were made at different angles, but no record exists le of the orientation of the x-ray machine. -- As 1. - a? a is - - buccal side inqual s < 1s - ! i! I , or -6 sp. : s Des I o reference >0: 558/ Comparison of the anatomy displayed on the images helps ·?? SLOB Shiff distinguish changes in horizontal or vertical angulation d structures 8 - -is - 89 is 5 -  · impadeds 9 i ! - iss- biforcation 32 B & S5 & ↑ reference. references I brackets - Orthobracket -1 el Noof of Man Night Posteriors -S buccally Periapical · view. E 6 I 6 I 7 jo ① S 5 -sch Mlesial shift , is? : - sid Reference & impaction i distally Is unerupted or impacted toothy Point bracket ; s sixis buccal side : 836 $ 1, $ - impacted buccaly or lingually  ? Shift 1 basis process o - ! Zygomatic ⑧ - buccal side. :5: 33 ② S i ~ processin? shift so Mesial ->. reference I i ! I : distal 2. process Palatal root structures buccal side in 7 elesial s ~ 6 S U reference) i ! Mesial shift: I buccal side's 2 process : ? distally Mesial "sLe. - Shift - : 8: 3 distal shift : -- $1. S - / % S ! A - - · is $1 reference 13 ① rool of 7 Palatal roof of 6 elB s - - · I * reference I reference reference's B ⑮ Z process & - iggs i *81 - I Me 6 Lamina cura: S 4 3 radiopaque line surround the tooth socket  - Lamina dura :. 110 el D. s radiopaqueline. sings. iss - 9 B sL - -Is !.. -. 34 Eggshell Effect density is - 1 I s This eggshell effect accounts for why normal structures such as the lamina dura, the border of the maxillary sinuses and nasal fossa, and abnormal structures, including the corticated walls of cysts and benign tumors, are well demonstrated on plain radiographs Soft tissue masses, such as the nose and tongue, do not show an eggshell effect because they are uniform rather than being composed of a dense layer surrounding a more lucent interior 35 -  -- &. Lesion , : mandible) occlusal view I i $ -. = sbuccal cortex & expansion &9 posterior border , 8 ? & radiopaque. : border. - radiolucent -5. I ! --- ,138 , buccal :4 9. x density 581's border i 18 - 199 Issible bone eggshell effed ? : radiopaque Igor t - - 51 - ↳ Siss It tangential path.. is so - jesig : st ~' si is jeggshell ess ! : :1 eggshell i : : , s -1 , = =Y - 112 attenuation 89 , 41, I Is density 81 - is / attenuation jet ! I is opacity By Softlisme/ A "ss "" : 1518 19 18 :1 - $5 Aln of A B - Jose attenuation j's +. - :- So enuation - -- , , is i yo - B , A ig & 858 89 ↑ attenuation -> radiopaque