Lesson 6 - Management of Patient Radiation Dose

Why do we need to manage patient dose?

Doctors are relying on imaging for diagnosis of patient pathology more
and more all the time, so the frequency of x-ray examinations is
increasing.
Diagnostic imaging procedures contribute to a large percentage of the
amount of ionizing radiation the general public is exposed to.

Doctors are relying on imaging for diagnosis of patient pathology more
and more all the time, so the frequency of x-ray examinations is
increasing.
Diagnostic imaging procedures contribute to a large percentage of the
amount of ionizing radiation the general public is exposed to.

What happened in the early 1900s

It was known that X-Rays can cause damage to human tissues soon after
their discovery.

What happened in the mid 1900s - 2019

Gonadal shielding was used to protect the patient as well as their future
offspring from the effects of ionizing radiation

What happened in the mid 1900s - now

• Advancements in technology have resulted in an accurate X-Ray beam
with little to no leakage radiation.
• Newer equipment can produce diagnostic images while using a much
lower technique than what was required in early equipmen

What happened in 2000s?

• Studies indicate that the radiosensitivity of gonads is lower than
previously thought.
• ICRP recommends the discontinue routine use of gonadal shields on
patients.

What happened in 2021?

• The CAMRT publishes a position statement advising that gonadal shields
are not required ROUTINELY on patients.
• CAMRT Position Statement
• Manitoba adopts the practice of no longer ROUTINELY placing gonadal
shields on patients.
• If a patient requests it, then we are obligated to provide it

What are ways to reduce patient dose?

1. collimate

2. appropriate technique

3. use of grids

4. AEC properly

5. shield patient if necessary

6. ALARA

why do we not use gonadal shields?

may obstruct some other anatomy, repeat images, and gonads are found to not be that radiosensitive

where should flat contact shields be placed?

outside of the collimated field

which body parts should always be protected?

breast, lens of the eye, and thyroid gland

how should the gonad shielding be placed on a supine female?

palpate the ASIS placing the shield ~ 2.5 cm medial to each ASIS (anterior superior iliac spine)

how should the gonad shielding be placed on a supine male?

the top of the shield should be placed at the level of the symphysis pubis

insteading of using a shield to protect breasts, what can you do?

imaging the patient in PA

If kV is increased by 15%, then IR
exposure is doubled. True or false?

true

If mAs doubles, then IR exposure
doubles. True or false?

true

What is dose creep?

too much mAs, overexposure to the patient

what are the 4 things you should always do?

1. avoid unnecessary examinations

2. employ proper imaging techniques

3. use optimal technique

4. use shielding when required

should gonadal imaging be done on adolescents?

no, their cells are too immature and must only be done if the benefit outweighs the conse

protective gonad shields must have a lead equivalency of at least x
mm of Pb

0.25 mm lead

protective gonad shields must have a lead equivalency of at least x
mm of Pb at 150 kVp

0.5 mm lead

what are good radiograph techniques for the chest?

75 kVp 16 mAs or 100 kVp 4.5 mAs

what is the air gap technique?

increased object to image receptor distance creating less scatter on the IR but the dose will be higher. usually used in chest radiographs

what should you do when you radiograph someone who didn’t know they were pregnant?

recount the event and fill out a form and present it to a physician to calculate EqD