GROUP 4

Garrett Robak

Griffin Walker

Kristin Innocenzi

Mohammed Javed

Noel Baquilod

Suzanne James

O I DMagnification

andS I D

Our Objective was to demonstrate the direct relationship between OID and

magnification, and the adjustments in SID and technique needed to compensate

for increased OID

OBJECTIVE

MATERIALS 4. 10 X 12 Detail film screen cassette (Wolf) RSS = 200CR X ray machine (Summit)Film Processor (AFP mini-mod 90)Phantom (Right Hand)Medical TapeMarkers (Numerical 1-4) (Alphabetical R)Pens, Pencils, PaperRuler, Tape MeasureCalculatorCollimator4 x 2 inch radiolucent sponges3.5 SandbagsRadiographic table topFloorSliding Board (Atom Lab EZ Mover)DensitometerDosimetersLight Box

PROCEDURE Using the phantom a series of four images of the right hand were taken.

Exposure 1 - Radiographic Table

EXPOSURE 1

•Position the hand of the phantom in a PA projection lengthwise onto a 10 X 12 detail cassette.•Using a 40’ SID, direct the central ray to the 3rd metacarpal and ensure that a proper marker R is used along with a proper numerical marker which should be labeled 1.•Set the KVP, MA and time on the control panel.•Take exposure, process the film in the darkroom, and refill cassette with a new film.

PROCEDURE Using the phantom a series of four images of the right hand were taken.

Exposure 2 - Radiographic Table

EXPOSURE 2

Position the hand of the phantom lengthwise on top of a vertical row of sponges measuring 8 inches.Secure the hand of the phantom to the sponge using tape to ensure it is flat on top of the sponges and place a 10 X 12 lengthwise cassette underneath of the sponges.Maintain a 40’ SID, direct central ray to the 3rd metacarpal and use proper markers R, 2.Keep all technique factors (KVP, MA and Time) constant on the control panel.Take exposure, process the film in the darkroom, and refill cassette with a new film.

PROCEDUREExposure 3 - Floor

EXPOSURE 3•Carefully position the phantom on the floor, and position the hand on top of the 8 inch sponge similar to exposure 2.•Align x ray tube to the cassette and center the central ray to the 3rd metacarpal.•Measure SID with a tape measure.•Mark cassette with proper markers R, 3.•Keep the same KVP, MA and time on the control panel.•Take exposure, process the film in the darkroom, and refill cassette with a new film.

PROCEDUREExposure 4 - Floor

EXPOSURE 4EXPOSURE 4Maintain the same position as Exposure 3.Maintain the same position as Exposure 3.Align x ray tube to the cassette and center the central ray to the 3Align x ray tube to the cassette and center the central ray to the 3rdrd metacarpal. metacarpal.Maintain the same SID as Exposure 3.Maintain the same SID as Exposure 3.Mark cassette with proper markers R, 4.Mark cassette with proper markers R, 4.Keep the same KVP, but adjust the MAS to account for the OID of 8 inch that the sponge Keep the same KVP, but adjust the MAS to account for the OID of 8 inch that the sponge has created.has created.Take exposure, process the film in the darkroom, and refill cassette with a new film.Take exposure, process the film in the darkroom, and refill cassette with a new film.

DATAIMAGE 1• SID = 40 inches (100 cm)• OID = 0• Collimation = 11” X 10”• KVP = 55 MAS = 2 MA = 100 Time = 20ms• Length of 3rd metacarpal = 68 mm• Densitometer reading = .84

IMAGE 2• SID = 40 inches (100 cm)• OID = 8 inches• Collimation = 11” X 10”• KVP = 55 MAS = 2 MA = 100 Time = 20ms• Length of 3rd metacarpal = 86 mm• Magnification factor = 1.25 (clinically unacceptable) Densitometer reading = .58+26% Magnification

DATAIMAGE 3• SID = 71 inches (177.5 cm)• OID = 8• Collimation = 11” X 10”• KVP = 55 MAS = 2 MA = 100 Time = 20ms• Length of 3rd metacarpal = 75 mm• Magnification factor = 1.1 (clinically acceptable)• +10 % Magnification• Densitometer reading = .24 (clinically unacceptable)

IMAGE 4• SID = 71 inches (177.5 cm)• OID = 8• Collimation = 11” X 10”• KVP = 55 MAS = 6.3 MA = 100 Time = 63ms• Length of 3rd metacarpal = 75 mm• Magnification factor = 1.1 (clinically acceptable)• +10 % Magnification• Densitometer reading = .51 (clinically acceptable)

CONCLUSIONThrough experimentation, we demonstrated the direct relationship between OID and magnification,

and compensated by increasing SID and ultimately MAS to produce a clinically acceptable radiographic image.

The first image, with all factors normal, was clinically acceptable in density and magnification factor.

The second image, because of increased OID, had a noticeable increase in magnification with a factor of 1.25. That is clinically unacceptable. This proved that there is a direct relationship between OID and magnification.

To compensate for the magnification of image 2 (a result of increased OID), we increased SID to 71 inches.

The third image therefore demonstrated a magnification factor of 1.1, which is clinically acceptable. However, the density of image three was .24, which, while clinically acceptable, would necessitate a repeat in most clinical situations.

To compensate for the loss in density, we used the string equation to find a new MAS.

The fourth image, with an updated higher MAS at 71 inch SID produced a clinically acceptable image in terms of density and magnification.

Thank You.QUESTIONS?

References:

1. Selman J. The Fundamentals of X-Ray and Radium Physics .4th Ed. Springfield Il: Charles C. Thomas, Publisher; 1965

2. Laver OG, Mayes JB, Thurston RP. Evalutating Radiographic Quality Mankato MN: The Burnell Co.; 1990

3. Saia DA. Radiography Examination. 7th Ed. McGraw-Hill Companies Inc; 2008

4. Bushberg JT. The Essential Physics of Medical ImagingPhiladelphia PA: Lippincott, Williams & Wilkins; 2002

Student Table:

Objective: Sue/GriffinMaterials: Kristin/MohammedProcedure: Garrett/MohammedData: Griffin/SueConclusion: AllReferences: Noel/KristinStudent Table: Garrett/Noel