How to take Radiographs Flashcards
Define Radiograph, Radiology and Radiography
- Radiograph - A record of an image produced by transmission of –x-rays through an object
- Radiology - This the interpretation of a
radiographic image - Radiography - These are techniques involved
in producing various radiographic images
How can dental radiography be justified
For an exposure to be justified, the benefit to the patient from the diagnostic information obtained should outweigh the detrimental effects of the exposure
What is diagnostic information dependent upon
- Patient preparation
- Patient positioning
- Radiation exposure
- Image processing
What is needed to take a radiographic image
- Patient
- X-ray machine
- Image Receptors
- Film Holder
- Operator
- Processing facility
- Reading facility
Name examples of single plane intra oral radiographs
Peri-Apical
Bitewing
Occlusal
Name examples of single plane extra oral radiographs
Panoramic tomogram
Lateral ceph
Lateral oblique
Name a type of multiplanar radiograph
Cone beam computed tomography (CBCT)
Describe the ideal conditions when taking an intra oral radiography
- Tooth and sensor should be as close together as possible
- The long axis of the tooth and sensor/film should be parallel to one another
- The x-ray beam should be positioned so it meets the tooth and sensor/film at 90⁰
- The position should be reproducible
What problems can be encountered when taking radiographs
- Teeth lie within bone- impossible to accurately determine root direction
- Multi-rooted teeth
- Anatomical structures (palate/floor of mouth) prevent direct contact without bending the image receptor
And so its not always possible to achieve the ideal response
Describe periapical radiography
Intra-oral radiograph shows the entire tooth and surrounding structures. Ideally needs to demonstrate 2-3 mm of bone all around the apex of the tooth.
What are the 2 techniques for periapical radiography
- Paralleling technique
- Bisecting angle technique
Why is the paralleling technique preferred to the bisecting angle technique
- Accurate
- Reproducible
- Minimal distortion
- Reduction of radiation dose - - Positioning aids
How is the paralleling technique carried out
- Sensor/film is placed into a beam aiming device
- This is positioned in the mouth so sensor/film is parallel to the long axis of tooth
- X-ray tube is angled perpendicular to the sensor
- Provides a reproducible image
(picture on lecture is litty)
Why is the bisecting angle not preferred and why is it still used
- Some distortion of image, no positioning aids, operator dependent thus not easily reproducible
- May be the only way to visualise apical pathology in
some cases
How is the bisecting angle technique done
- Place the sensor/film as close to the tooth as possible without bending it
- The angle formed between the long axis of the tooth and the long axis of the sensor/film
is estimated and mentally bisected - X ray tube head is positioned at 90⁰ to the bisecting line with the central beam aimed at the apex of the tooth
- Very operator dependent – no holder and no beam aiming device
When would you need to use periapical radiography (loads)
- Detection of apical infection/inflammation
- Assessment of the periodontal status
- After trauma to the teeth and associated alveolar bone
- Assessment of the presence and position of unerupted teeth
- Assessment of root morphology before extractions
- During endodontics
- Preoperative assessment and postoperative appraisal of apical surgery
- Detailed evaluation of apical cysts and other lesions within the alveolar bone
- Evaluation of implants postoperatively.
What are the 2 types of occlusal radiography and give quick description
Maxillary and Mandibular
These are radiographs where the image receptor is
placed in the occlusal plane
What are the 2 types of maxillary occlusal radiograph
Upper Standard Occlusal
Upper Oblique Occlusal
How do you have to position the x ray tube for maxillary occlusal radiographs
place it at 60-70 degrees from the sensor ting and on the ridge of the nose
What indications (reasons) are there to use maxillary occlusal radiogrpah
- Periapical assessment of teeth (if cannot tolerate IOPA)
- Detecting presence of pathology (#, cysts)
- Parallax for unerupted teeth
- Fractures of teeth/alveolar bone
- Assessment of antrum/roots displaced
Why is it important to give a patient a thyroid collar
to protect the thyroid as it is very radiosensitive
AY BAWS CAN I HABE DE NOTE PLZ
Make sure you learn what all these types of radiograph look like
What are the 3 types of mandibular occlusal radiographs
- Lower 90 occlusal (true occlusal)
- Lower 45 occlusal
- Lower oblique occlusal
What are the indications/reasons to take a mandibular occlusal radiograph
- Presence of radiopaque calculi in submandibular salivary ducts
- Buccolingual position on teeth/pathology
- Expansion caused by tumours/cysts
- Assess mandible width prior to implant placement
Why is an extra-oral panoramic radiography a very popular technique in dentistry
- All the teeth and supporting structures can be shown in one image.
- Its very simple to carry out.
- Patients are able to tolerate this more than a periapical.
What are the indications/reasons to take an extra oral panoramic radiograph
- 3rd molar assessment prior to extraction
- Orthodontics
- Mandibular fractures
- TMJ problems (changes in occlusion/trauma/change in range of motion)
- Multiple extractions
- Bony lesions/unerupted tooth which cannot
be fully visualised on intraoral images - In the case of a grossly neglected mouth.
What are the disadvantages of taking a panoramic radiograph
- Image Quality
- Operator dependant/ patient dependent
- Ghost images and superimposition
- Dose
- Magnification
How does the tube head and sensor move relative to the patient in a panoramic tomography
the patient stands still and the tube head and sensor move around the patients head
Describe the image produced in a panoramic tomography
This movement of the tube head and sensor creates blurring of all structures that do not lie within the “focal trough” or “focal plane”
What is a “focal trough” and what shape is it in a panoramic machine and why
- A three-dimensional area within which structures are reasonably well defined on the final image.
- In the panoramic machine, the focal trough is designed to be horseshoe shaped to correspond to the shape of the dental arches.
How should you position the head for a panoramic tomography
- Mid saggital plane should be vertical
- Frankfort plane (infraorbital rim to top of ear canal) horizontal and parallel to the ground
- Front incisors biting in the groove of bite block
- Machine is adjusted to the size of patient – using callipers or “canine light”
What aids does the panoramic machines have to aid positioning the patient
- Machine consists of patient-positional aids i.e. chin rest, forehead rest, lateral head supports, bite block.
- Laser lights to help align patient correctly
When are cephalometric radiographs normally used
Normally used for orthodontic treatment planning
What does a cephalometric radiograph show
This type of image shows the relationship between your teeth, jaw and profile (facial skeleton), which makes it especially helpful for orthodontic planning and realignment treatment
What machine is used to do cephalometric radiography
A Cephalostat
What are the indications/reasons to do cephalometric radiography
- Skeletal/soft tissue abnormalities
- Treatment planning
- Monitoring progress
- Assess results of treatment
Describe the technique to take a cephalometric radiography
- Patient positioned in cephalostat with mid sagittal plane vertical and Frankfort plane horizontal
- Teeth should be in occlusion
- Head immobilised with ear rods in EAM
- Ruler dropped to nasal bridge
