Panoramic Radiography Abeer A Almashraqi Ass
Panoramic RadiographyAbeer A Almashraqi Ass. Professor of Oral and Maxillofacial Radiology Definition It is an extra-oral radiographic technique for producing a single image of both the maxillary & mandibular dental arches & their supporting structures. Principles Scanography (slit beam).
Tomography (curved surface rotation). Panoramic Imaging : General Principles
Tomography: allows radiographing in one plane of an object while blurring or eliminating images from structures in other planes. Tomo is Greek for section View sections or radiographic slices Panoramic Imaging : General Principles
Tomogram Patient remains stationary while x-ray source & film move in opposite directions in a fixed relationship through one or a series of rotation points. Rotation points can be inside or outside of the focal trough Panoramic Imaging : General Principles
Focal trough in tomogram Or plane of acceptable detail, or image layer, is the plane that is not blurred on the radiograph Panoramic Imaging : General Principles
Focal trough in pantogram Width & thickness governed by many factors Objects lying within the focal spot are shown clearly; objects outside are blurred Panoramic Imaging : General Principles
Curved surface A panoramic radiographor pantomogram is produced using curved-surface tomography. Flat surface Panoramic Imaging : General Principles
Rotational panoramic radiography: It is accomplished by rotating a narrow beam of radiation in the horizontal plane around an invisible pivot point/axis positioned intraorally. Cassette & tube travel in opposite directions around the patient Panoramic Imaging : General Principles
Patient remains stationary as x-ray tube and film cassette-holder (which are connected) both rotate around the client Panoramic Imaging : General Principles
A vertical, narrow beam (scanography) is used compared with the larger, circular or rectangular beam used in conventional intraoral radiography Panoramic Imaging: Principles of Image Layer Formation
Film placed on circular drum or a moving flat cassette Horizontal magnification is reduced to match vertical magnification by adjusting speed of film in respect to projection of beam Panoramic Imaging: Principles of Image Layer Formation
The image layer is called the focal trough Panoramic Imaging: Image Layer/Focal Trough Defined
A three-dimensionalzone in which structures are reasonably well-defined. A zone in an object defined as containing those object points depicted with sufficient detail to be distinguished. Determines where dental arches must be positioned to achieve clearest image Panoramic Imaging: Principles of Image Layer Formation
Objects outside this sharply depicted plane will appear distorted, fuzzy, or may not be visible Indications Assessment of impacted teeth.
Assessment of both jaws before implant placement. Assessment of both jaws before planning for dentures. Indications: Demonstrating fractures of the mandible. Indications: 5- Demonstrating cysts, tumors & other pathological conditions affecting both jaws. Indications: Demonstrating periodontal disease in overall view (allowing intra-oral films to be kept minimal). Indications: Demonstrating an anterior view of the sinuses & thefloor of the nasal cavity. Orthodontic assessment & evaluation of the eruption patterns, growth & development. Advantages It allows examination of both jaws in one radiograph.
Its procedures are relatively simple to perform & require minimal time. It requires minimal patient cooperation. It can be used with patient unable to open their mouth.
It delivers radiation dose less than full mouth survey. It is useful in case presentation & patient education. Limitations 1. Image quality: - Magnification and distortion
- Poor definition compared to intraoral - Overlap - Superimposition & ghost images Limitations: 1- image quality
- Certain amount of magnification ( film object distance) & overlapping is present even with proper technique. Limitations: image quality
- Poor definition (lack of details) compared to intraoral due to: 1- The use of intensifying screen & fast films. 2- Tomographic process. 3- Increased object-film distance. Panoramic Periapical Periapical & Bitewing radiographs are preferred over Panoramic radiograph for:
Caries Periodontal involvement Early or limited periapical pathology Endo. treatment Limitations: 2- Focal Trough (Image Layer) limitation:
- Areas outside are not visible - Size & shape limits to those structures which fit into the image layer - Size & shape not adjustable so not all patients arches image equally well 3- The high cost of the equipment. Components of Panoramic Units
All machines share main components: -X-ray tube head & slit collimator. -Cassette & cassette-carriage assembly. -Head positioning apparatus. -Exposure controls. -Standing or sitting patient position. - Pan / Ceph or Pan only X-ray tube head and slit collimator Intraoral Collimation Panoramic Curved /Rigid Straight /Rigid Flexible/ Soft Head Positioner/Cassette Holder Exposure control Sitting / Standing Pan/Ceph Panoramic Technique 1- Patient Preparation
2-Machine Preparation ( Setting Exposure Parameters) 3-Patient Positioning Patient preparation: Explain the procedure to the patient & ask him to remain still without motion. Ask the patient to remove any dental appliance, earrings, hair pins, necklace, eyeglass & any other metallic object in the head & neck region. Ask the patient to wear a lead apron without a thyroid collar. The apron must be placed low Equipment Preparation:
Loading the panoramic cassette. Sterilize bite block between patients or cover it with a disposable plastic cover. Set the exposure factors according to manufacturers recommendations to accommodate patients height & age. Patient positioning: Ask the patient to sit/stand with the back straight & erect. Position the mid sagittal planeperpendicular to the floor. Patient positioning: Instruct the patient to bite on the plastic bite-block. N.B. Upper & lower anterior teeth must be placed in the groove found in the bite block (in an edge to edge position). Patient positioning: :
Position the Frankfort plane (plane passing from the floor of the orbit to the external auditory meatus) parallel to the floor. Ask the patient to close his lips & to place the tongue against the hard palate.