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 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.

Week 7 assignment due date. 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 20) + 40 + 8 = 88 kVp x

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 Time settings will be chosen according to specifications of intensifying screens. 1/40 1/8

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 Step 7: Evaluate Radiograph 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. 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. 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.