1. RADIATION PROTECTION IN DIAGNOSTIC AND INTERVENTIONAL RADIOLOGY
Part No...., Module No....Lesson No
Module title
IAEA Training Material on Radiation Protection in Diagnostic and Interventional Radiology
RADIATION PROTECTION IN DIAGNOSTIC AND INTERVENTIONAL RADIOLOGY
Part 15.3: Optimization of protection in radiography
Practical exercise - HVL measurement
Part …: (Add part number and title)
Module…: (Add module number and title)
Lesson …: (Add session number and title)
Learning objectives: Upon completion of this lesson, the students will be able to: …
. (Add a list of what the students are expected to learn or be able to do upon completion of the session)
Activity: (Add the method used for presenting or conducting the lesson – lecture, demonstration, exercise, laboratory exercise, case study, simulation, etc.)
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IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

2. Part No...., Module No....Lesson No
Module title
Overview / Objectives
Subject matter : HVL measurement
Step by step procedure to be followed to implement the considered QC test
Interpretation of results
Explanation or/and additional information
Instructions for the lecturer/trainer
15.3: Optimization of protection in radiography
IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

3. Part 15.3: Optimization of protection in radiography
Part No...., Module No....Lesson No
Module title
IAEA Training Material on Radiation Protection in Diagnostic and Interventional Radiology
Part 15.3: Optimization of protection in radiography
HVL (Filtration) Measurement
Part …: (Add part number and title)
Module…: (Add module number and title)
Lesson …: (Add session number and title)
Learning objectives: Upon completion of this lesson, the students will be able to: …
. (Add a list of what the students are expected to learn or be able to do upon completion of the session)
Activity: (Add the method used for presenting or conducting the lesson – lecture, demonstration, exercise, laboratory exercise, case study, simulation, etc.)
Duration: (Add presentation time or duration of the session – hrs)
Materials and equipment needed: (List materials and equipment needed to conduct the session, if appropriate)
References: (List the references for the session)
IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

4. Half Value Layer (HVL) (I)
Possibly the most important test
Checks whether there is sufficient filtration in the x-ray beam to remove damaging low energy radiation
15.3: Optimization of protection in radiography

5. What Minimum Equipment is Needed?
Electronic device (multi-function meter) to measure dose
High purity aluminium layers. (Most aluminium has high levels impurities, e.g., Cu)
Stand to hold the dosimeter, e.g., laboratory stand
Tape measure, spirit level
Roll of removable tape
15.3: Optimization of protection in radiography

6. Tape Measure, Spirit Level
15.3: Optimization of protection in radiography

7. Half Value Layer (II)
Method (simplest - using a multifunction test meter) :
Place the detector half way between the front of the collimator and the table top.
Set 80 kVp, fixed mAs (e.g., 50 mAs)
Collimate x-ray beam to size of detector
Measure exposure three times
15.3: Optimization of protection in radiography

8. HVL Measurement Geometry
X-Ray Tube
Collimator
Aluminium Sheets
X-Ray Beam
Detector
Table top
15.3: Optimization of protection in radiography

9. Half Value Layer (III)
Tape a 1 mm sheet of aluminium to the front of the collimator and measure the dose
Add another 1 mm sheet of aluminium, measure again, and repeat until the dose has fallen to below 50% of the initial, unattenuated, value
Remove all aluminium, and make 3 more exposures
15.3: Optimization of protection in radiography

10. Half Value Layer (IV) Analysis : Average all the “no Al” measurements
Plot all results on semi-log graph paper
From the graph, find the thickness of Al required to reduce the unattenuated dose by 50% - this is the HVL
The HVL must be at least that specified in local regulations, e.g., 2.3 mm Al at 80 kVp
Ideally, it should be at least 3.0 mm Al or higher to assist in minimizing patient dose
15.3: Optimization of protection in radiography

11. HVL Measurement (initial value = 9 Dose mm Al
Be careful of beam hardening (semi-log plot is not a straight line)
Use points either side of half initial value
Calculate HVL :
(initial value = 9
50% of this = 4.5,
thus HVL = 2.6 mm Al)
mm Al
15.3: Optimization of protection in radiography

12. Minimum HVL Values (IEC)
Acceptable
Not acceptable
15.3: Optimization of protection in radiography

13. Where to Get More Information
Quality Control in Diagnostic Imaging, Gray JE, Winkler NT, Stears J, Frank ED. Available at no cost.
15.3: Optimization of protection in radiography