Chapter 19 Paralleling Technique, Radiology 1

Paralleling technique is also known as -what is it used to expose?

-Extension Cone Paralleling Technique (XCP)
-right-angle technique
- long-cone technique
Used to expose periapical and bitewing image receptors

Parallel

Moving or lying in the same plane, always separated by the same distance. Not intersecting.

Intersecting

to cut across or through

Perpindicular

Intersecting at or forming right angles

Right angle

an angle of 90 degrees formed by two lines perpendicular to each other

Long axis of the tooth

Imaginary line dividing the tooth longitudinally (vertically) into two equal halves

Central ray

The central portion of the primary beam of x-radiation

The paralleling technique is based on the concept of

parallelism

The basic principles of paralleling technique are

1. 1. The receptor is placed in the mouth parallel to the long axis of the tooth being radiographed
   
   2. The central ray of the X-ray beam is directed perpendicular (at a right angle) to the receptor and the long axis of the tooth.
   
   3. A beam alignment device must be used to keep the receptor parallel with the long axis of the tooth. The patient cannot hold the receptor in this manner

Rules for paralleling technique

Receptor covers area to be examined
•Thereceptorr is placed parallel to the long axis of the tooth being examined
• The central ray of the X-ray beam is directed perpendicular to the receptor and the long axis of the tooth
• Vertical angulation: central ray perpendicular to receptor/long axis of the tooth
• Horizontal angulation: central ray through contacts between teeth
• Failure to center beam to receptor results in closed contacts

To achieve parallelism between the receptor and the tooth, the ___ distance must be increased to keep the receptor parallel with the long axis of the tooth.

object receptor distance (distance between tooth and receptor)

To achieve parallelism between the receptor and the tooth the receptor must be placed

away from the tooth and toward the middle of the oral cavity

increased object-receptor distance

results in increased image magnification

Target-receptor distance

distance between source of x-rays and receptor

To compensate for image magnification the target receptor distance must also be

increased to ensure that only the most parallel rays will be directed at the tooth and receptor

long (16 inch) target receptor distance must be used with

paralleling technique

Sometimes called long cone technique

long refers to the length of the cone or the PID

What results in less image magnification and increased definition

Long target receptor distance

A rectangular collimator is used in this technique to

reduce the amount of radiation that the patient recieves

Paralleling technique requires the use of a

beam alignment device or a receptor holder to position the receptor parallel to the long axis of the tooth

Beam alignment devices

used to position an intraoral receptor in the mouth and maintain the receptor in position during exposure

Examples of commercially available intraoral beam alignment devices include the following Dentsply Rinn products

-The Rinn XCP extension cone paralleling technique
-The Rinn XCP-ORA
-The Rinn XCP-DS FIT universal sensor holder
-The Rinn flip-ray system

The Rinn XCP extension cone paralleling

-Includes 3 plastic bite blocks, 3 plastic aiming rings, and 3 metal indicator arms.
-Different bite blocks are available that accommodate film and PSP sensors, as well as digital sensors.
-The plastic bite blocks are color-coded to aid in assembly
-blue used in the anterior regions
-yellow used in the posterior regions
-red are used for bite wing projections
- green are used in endodontic procedures

The Rinn XCP-ORA

Reduced number of component parts- (One Ring & Arm) one aiming ring and one indicator arm; different bite blocks for different receptor sizes

The Rinn XCP-DS FIT universal sensor holder

Bite block that includes self-adjusting clip that stretches to accommodate the size of the digital sensor regardless of what brand or size.
-These bite blocks may be used with the Rinn XCP or Rinn XCP-ORA systems

The Rinn flip-ray system

uses a rotating bite-block and ring to eliminate multiple positioning parts
-May be used with film or PSP sensors

Examples of receptor holding devices that are used with the paralleling technique to position an intra oral receptor are

The stabe bite block
Rinn Snap A Ray holder

The Rinn snap a ray holder

Comes in two versions, one for film and one for digital sensors. This receptor holding device can be used in both anterior and posterior areas

The stabe bite block

a disposable receptor holder made of Styrofoam and is designed for one time use only

The Rinn XCP beam alignment device insturments are recommended for exposure of

periapical receptors- they aid in the alignment of PID with receptor

The size of the intraoral receptor used with the paralleling technique depends on

which teeth are being radiographed

Anterior teeth

-Size 1 receptor is used
-This narrow size is needed to permit placement high in the palate without bending or curving.

Size 1 is always positioned with the long portion of the receptor in a

vertical (upright) direction

Posterior region

Size 2 receptor is used.
Size 2 is always placed with the long portion of the receptor in a horizontal (sideways) direction

5 basic rules should be followed when using the paralleling technique

1. Receptor placement- it must be positioned to cover the prescribed area of the tooth to be examined.

2. Receptor position- it must be positioned parallel to the long axis of the tooth. The receptor and beam alignment device must be placed away from the teeth and toward the middle of the oral cavity

3. Vertical angulation- The central ray of the x-ray beam must be directed perpindicular (at a right angle) to the receptor and long axis of the tooth.

4. Horizontal angulation- the central ray of the x-ray beam must be directed through the contact areas between the teeth.

5. Receptor exposure- The x ray beam must be centered on the receptor to ensure that all areas are exposed. Failure to center the x-ray beam results in a partial image on the receptor or a "cone-cut". Cone cuts can either be produced with a round or rectangular PID.

Size ____would be used on pedo (child) patient for post/ant images, but in some cases, size 1 or 2 may be used depending on age of the child

0

Patient Prep

• Explain the procedure: "inform before you perform"
• Adjust chair and headrest (maxillary parallel to the floor, midsaggital plane perpendicular to the floor)
• Place lead apron/thyroid collar on pt.
• Remove all objects such as eyeglasses. Any other items to remove prior to exposure? Dentures, retainers

Equipment prep

After patient prep all equipment must be prepared before the exposure of any receptors

Set all exposure factors such as (_) BEFORE placing receptor in mouth

kv, ma

Open sterilization bags and glove when assembling receptor holder

place receptor in holder

Make sure receptor is

centered when looking through aiming ring!!!!!

Exposure sequence

A definite order for periapical receptor placement and exposure that must be followed in the placement and exposure of intraoral films.

Anterior exposure sequence

-Begin with the maxillary right canine tooth
-Expose all of the maxillary anterior teeth
-End with the maxillary left canine
-Move to the mandibular arch
-Begin with the mandibular left canine
-Expose all of the mandibular anterior teeth
-Finish with the mandibular right canine

Why do you always begin with the anterior teeth? when exposing periapical receptors

The size 1 receptor used for anterior exposures is small, less uncomfortable, and easier for the patient to tolerate. Some practitioners use a size 2 receptor instead, which may be more difficult to place.
-The more tolerable anterior placements allow the patient to become more accustomed to the beam alignment device used in the paralleling technique.
-anterior is less likely to cause the patient to gag.

With size 1 receptor, a total of _ anterior receptor placements are used in the paralleling technique.

7 anterior, 4 maxillary exposures and 3 mandibular exposures

If size 2 is used then there are _ anterior receptor placements

6- 3 maxillary and 3 mandibular

Exposure sequence for the Rinn XCP beam alignment device is

1. 1. assemble the anterior Rinn XCP instrument
   2. Begin with the maxillary right canine (tooth 6)
   3. Expose the anterior teeth working from the patients right to the patients left.
   4. End with the maxillary left canine (tooth 11)
   5. Next move to the mandibular arch
   6. Begin witht the mandibular left canine (tooth 22)
   7. Expose all the mandibular anterior teeth working from the patients left to right.
   8. Finish with the mandibular right canine (tooth 27)

Posterior exposure sequence for paralleling technique

Always expose the premolar receptor first and then the molar receptor
-Premolar easier for the patient
-less likely to gag

____ posterior placements may be used

8- 4 maxillary exposures and 4 mandibular exposures

Posterior periapical exposure sequence for the XCP

1. begin with the maxillary right quadrant
2. assemble the posterior Rinn XCP Instrument
3. First expose the premolar receptor(teeth 4 and 5) then expose the molar receptor (teeth 1, 2 and ,3)
4. Don't reassemble, move to the mandibular left quadrant
5. Expose the premolar receptor (teeth 20 and 21) then expose the molar receptor (teeth 17, 18, and 19)
6. reassemble the posterior rinn XCP over a covered work surface
7. next move the the maxillary left quadrant
8. Expose the premolar receptoir (teeth 12 and 13) and then expose the molar receptor (14, 15, and 16)
9. finish with the mandibular right quadrant
10. expose the premolar receptor (28 and 29) and then expose the molar receptor (30, 31, and 32)

Shallow palate or "low palatal vault"

use cotton rolls on bite-block---run it with the length of the receptor biteblock
-Adjust vertical angulation by 5-15 degrees sometimes distortion occurs

Bony growths: Tori/Torus

Maxillary "torus palatinus": place receptor on far side of tori/torus---never on tori •
Mandibular "torus mandibularis": place receptor between tori/torus and tongue---never on tori

receptor placement

The specific area where the receptor must be positioned before exposure.

The anterior Rinn XCP is used for all

anterior receptor placements
After the anterior rinn XCP has been assemled a size 1 receptor is inserted vertically into the bite block and secured in the slot.
a total of 7 anterior placements including the following
- two maxillary canine exposures
-Two maxillary incisor exposures
-two mandibular canine exposures
-one mandibular incisor exposure

posterior receptor placement

The posterior Rinn XCP- after the posterior Rinn XCP has been assembled a size 2 receptor is inserted horizontally into the bite block and secured.
-A total of 8 posterior placements include the following
- two maxillary premolar exposures
-two maxillary molar exposures
-two mandibular premolar exposures
-two mandibular molar exposures

torus

A bony growth in the oral cavity

maxillary torus

a nodular mass of bone seen along the midline of the hard palate

mandibular torus

Bone growth noted on the lingual aspect of the mandibular arch.

advantages of paralleling technique

-accuracy: the image is free of distortion.
-simplicity: eliminates the need to determine horizontal and vertical angulation. eliminates chances of dimensional distortion.
-duplication: comparison of serial radiographs has great validity.

disadvantages of paralleling technique

-Receptor placement may be difficult
-Discomfort: beam alignment device may cause discomfort

What happens to the image when the object-receptor distance is increased?

Increased image magnification & Loss of definition

For the paralleling technique the exposure of the mandibular incisors should show

Entire crowns & roots of 4 mandibular incisors.
Contacts of the central incisors must be visible.

For the paralleling technique the exposure of the mandibular canine should show

entire crown & root of canineInterproximal alveror bone
Mesial & distal contacts

For the paralleling technique the exposure of the maxillary canine should show

entire crown & root of canine
Apex
alveror bone
Mesial Contact

For the paralleling technique the exposure of the maxillary incisors should show

entire crown & root of one lateral & one central incisor
Mesial contact of the adjacent central incisor & Mesial contact of the adjacent canine