Transcript VETT 116 Veterinary Diagnostic Imaging 1

Week Seven
VETT 116: Veterinary Diagnostic Imaging 1
Overview of Week 7
A technique chart provides a consistent method of
choosing the proper radiograph settings without having to
calculate all of the components by hand with each
exposure. Taking the time to prepare a technique chart in
the beginning will help to save time, money, and radiation
exposure to both the patient and staff.
A technique chart is not a “one-size fits all”. Depending on
the types of radiographs, film, intensifying screens, and
equipment, many different types of technique charts may
need to be created for the same machine. A technique
chart is an essential component in obtaining a consistent
diagnostic radiograph with every exposure.
VETT 116: Veterinary Diagnostic Imaging 1
Week 7 Objectives
Objectives:
•Purpose, use, and benefits of the technique chart.
•Explore factors that will effect the accuracy of the
technique chart.
•Practice techniques and skills required to develop a
technique chart.
VETT 116: Veterinary Diagnostic Imaging 1
Week 7 Required Reading
Clinical Textbook for Veterinary Technicians, by
McCurnin and Bassert, pp. 282-283.
Radiography in Veterinary
Technology, pp. 97-103.
VETT 116: Veterinary Diagnostic Imaging 1
Important Dates and Deadlines
Week 7 assignment due date.
Week 8 – Exam 2
Please see the Student Handbook for a complete schedule
with calendar due dates.
VETT 116: Veterinary Diagnostic Imaging 1
Week 7 Directed Learning
Part 1: Radiographic Technique Charts
Reading Assignment: Clinical Textbook for Veterinary Technicians,
pp. 282-283.
Also View: Rad Physics for Vet Students – Chapter 5
Upon completion of the reading assignment and viewing of this section
of the weekly lesson, please answer the questions at the end of this
section.
Small Animal
Radiographic Technique Charts
Purpose:
• Consistent quality radiographs
• Reduced number of repeat films
– Reduced radiation to patient and staff
• Reduced cost and time
Factors Affecting Technique Charts
Several factors may influence the development and
accuracy of the technique chart. Some of these include:
•Speed of screens
•Age of screens
•Speed of film
•SID
•Amount of beam filtration
•Temperature and time of film processing
•Type of grid
Suggested Charts
Required charts may include the following:
•Screen and nonscreen
•Grid and nongrid
•Various film-screen combinations
•Species specific
•Anatomy specific
Variable kVp Technique Chart
Step 1: Select a Patient for Test Radiograph
A) The ideal subject will be:
•Cooperative adult dog (sedation may be required)
•Moderate size and muscling
•Average weight (about 50 lbs)
•Hair coat clean with medium to short length
B) Patient in lateral recumbency, measure widest
part with calipers.
Variable kVp Technique Chart
Step 2: Evaluate the x-ray machine.
Evaluate some of the basic constant factors:
•Line voltage (does voltage to the machine remain
constant?)
•Source-image Distance (SID)
Variable kVp Technique Chart
Step 3: Exposure Technique
A) Kilvoltage
•Santes’ Rule
(2 x tissue thickness in cm) + SID + grid factor = kVp
Example 1:
Thickness: 20 cm
SID: 40 inches
Grid: 8:1
Calculation:
(2 x 20) + 40 + 8 = 88 kVp
Variable kVp Technique Chart
Step 3: Exposure Technique
A) Kilvoltage
Example 2:
Thickness: 15 cm
SID: 40 inches
Grid: 12:1
Example 3:
Thickness: 9 cm
SID: 40 inches
Grid: None
Answers:
Example 2 – 82 kVp
Example 3 – 58 kVp
Variable kVp Technique Chart
Step 3: Exposure Technique
B) Milliamperage (mA) – select highest setting
possible with least amount of exposure..
C) Exposure time – select fastest setting
appropriate for mA
Which would be a faster
time?
1/120
1/40
1/8
Time settings will be chosen
according to specifications of
intensifying screens.
Variable kVp Technique Chart
Step 4: Film-screen system
•Select the intensifying screen that best
represents an average speed
•Select film that is not expired or damaged.
Step 5: Grid
•Double check Grid Ratio
•Ensure Grid is in place
Create Base Chart
Step 6: Test Exposure
•Using calculated kVp and mAs, set the kVp, mAs, and
time on the control panel of the machine. Verify mA.
•Process film in standardized dark room with
adequate developing and fixing solutions.
Step 7: Evaluate Radiograph
•Too dark: Decrease mAs by 30% - 50% or
kVp 10% - 15%
•Too light: Increase mAs by 30% - 50 % or
kVp 10% - 15%
•Repeat Developing and Evaluation process.
Create Base Chart
Step 8: Formulate and Plot Technique Chart
•If the measure of thickness is less than 10 cm – a grid is
normally not used. (this will also adjust the mAs and time)
•For every cm above the base setting – increase kVp by 2.
•For every cm below the base setting – decrease kVp by 2
•For kVp settings greater than 80 – increase kVp by 3.
VETT 116: Veterinary Diagnostic Imaging 1
Week 7 Directed Learning
Part 1: Radiographic Technique Charts – Review Questions
Upon completion of the reading assignment and reviewing the weekly
lesson, be able to answer the following questions.
1) What is Santes’ rule? How does it apply to producing a radiology and
what is the formula?
2) Using Santes’ rule, calculate kVp using the following information:
Thickness of area: 11 cm
Grid factor: 12
SID = 40
What is the kVp?
Please remember a printable copy of this assignment, may be accessed by clicking on the paperclip icon
that is located on the presentation toolbar below.
VETT 116: Veterinary Diagnostic Imaging 1
Week 7 Directed Learning
3) How is a technique chart created?
4) What factors will influence the technique chart?
5) What type of patient should be used for creating a
technique chart? Describe the physical
characteristics.
VETT 116: Veterinary Diagnostic Imaging 1
Week 7 Directed Learning
6) Any body part exceeding this measurement
requires the use of a grid to reduce fog-producing
scatter radiation.
a)
b)
c)
d)
20 cm
10 cm
2.5 cm
30 cm
7) If an initial radiograph is too light, how should the kVp
and mAs be adjusted?
8) If an initial radiograph is too dark, how should the
kVp and mAs be adjusted?
VETT 116: Veterinary Diagnostic Imaging 1
Week 7 Directed Learning
Part 2: Development of a Technique Chart
For this assignment, you will create a technique chart based on the
given factors:
Measurement: 10 cm (Lateral abdomen)
Film Speed: Medium (5 mAs to 12.5 mAs)
Grid ratio: 8:1
SID: 40 inches
mA = 300
Your assignment is to:
•Calculate the kVp, mAs, and time that should be used for
the initial radiograph.
•Develop your technique chart for measurements of 5 cm
through 25 cm in increments of 1 cm.
VETT 116: Veterinary Diagnostic Imaging 1
Week 7 Directed Learning
Your technique chart should include the following information:
Thickness
(cm)
kVp
mA
Time
(seconds)
mAs
SID
Grid
Submit this assignment to your course instructor by the week 7
assignment due date. (20 points)
Additional Resources
Creating a Radiographic Technique Chart
Creating Your Technique Chart
Developing Your Own Technique Chart
VETT 116: Veterinary Diagnostic Imaging 1
Conclusion
This concludes Week 7 assignments for Diagnostic Imaging 1. Please
make sure you have completed all reading and written assignments. You
may be asked this information again through quizzes, discussion, or
exams.
Please submit the following to your Course Instructor:
•Week 7, Part 2 Technique Chart
•Complete the Assignment Verification checklist through your WebCT
course website
If you have any questions regarding any of the assignments or
information presented during this week, please contact your course
instructor.
Resources
Clinical Textbook for Veterinary Technicians, McCurnin and
Bassert
Radiography in Veterinary Technology, Lavin, 4th edition.
Practical Radiograph for Veterinary Nurses, Easton.