RTR. 1 Integrate safe Principles and procedures into practice

Leakage radiation cause

loss of the tube vacuum insert

Pregnant MRT dose limit

4mSv

Whole Body Public and Students Annual Dose Limit

1mSv

Eye Lense Public and Students Annual Dose Limit

15mSv

Skin Public and Students Annual Dose Limit

50mSv

Annual MRT dose limit

50mSv (in any single year)

Whole Body Annual Dose Limit for Radiation Workers

20mSv (5 year averaged into one)

Eye Lense Annual Dose Limit for Radiation Workers

20mSv

Skin Annual Dose Limit for Radiation Workers

500mSv

Hands and Feet Annual Dose Limit for Radiation Workers

500mSv

<100kV Lead Equivalence

0.25mm

100-150kV Lead Equivalence

0.35mm

>150kV Lead Equivalence

0.5mm

Front and Back Lead Gown Pb Equivalence

• front: 0.5mm

• back: 0.25mm

Thyroid Shield Pb Equivalence

0.5mm

Recommened Eye Shield Pb Equivalence

0.75mm

Gloves or Gaunlets Pb Equivalence

0.25mm

Lead Acrylic screens or Movable Shields

0.5mm

Three ALARA Principles

• Time

• Distance

• Shielding

Absorbed Dose

(Gy) the amount of dose absorbed into material

Effective Dose

(mSv) counts the degree of biological damage that may be caused by the type of ionizing radiation

Types of Radiation and Matter Interactions

• Coherent scatter = low-energy photon changes direction after interaction 

• Photoelectric absorption = photon ejects an inner-shell electron, which the ejected electron gets absorbed; has the cascading effect

• Compton scatter = photon ejects an outer-shell electron

Effects on Compton Scatter and PE Absorption as kV increase

• fewer compton

• many FEWER photoelectric

• more transmission

Effects on Compton Scatter and PE Absorption as Tissue Atomic # increases

• no change in compton

• many more photoelectric

• less transmission

Effects on Compton Scatter and PE Absorption as Tissue Mass Density increases

• proportional increas in compton

• proportional increase in photoelectric

• proportional decrease in transmission

Radiosensitive Cells

• Immature/non-specialized 

• Rapid cell division/ high reproductivity 

• High oxygenated tissues

Radiosensitive Tissue Rank

1. Most radiosensitive blood cells: Lymphocytes 

2. Highly radiosensitive: Epithelial

3. Insensitive: Muscles

4. Insensitive: Adult nerve cells

Somatic Effects

effects on the individual irradiated

Early tissue reactions

• Acute Radiation Syndrome

  • Hematopoietic syndrome

  • GI syndrome 

  • CV syndrome

• radiatio burn (erythema)

Late Effects

• Cataracts

• Fibrosis

• Organ atrophy

• Reduced fertility/ sterility

• Teratogenic effects (fetus)

When is the Fetus most susceptible to radiation-induced congenital abnormalities

During Organogenesis (10-12 weeks)

Stochastic Effects

= probability depends on received dose, but the severity does not

• cancer

• genetic/hereditary effects

Genetic/ Non-somatic effects

 effects on future generations due to the irradiation of previous generations 

• Gonadal doses as low as 0.1 Gy can depress the male sperm population, cause genetic effects, and may delay or suppress menstruation

CT Dose Reduction Strategies

• Tube current modulation (AEC)

• Iterative reconstruction

• Tube voltage and scan parameter optimization 

• Isocentering

Mobile Radiation Safety

• The radiographer must wear protective garments.

• The radiographer should stand at least 2 m away from the X-ray tube and useful beam.

• If possible, the radiographer should also stand at a right angle to the x-ray beam–scattering object (the patient) line.

as SID increases… energy and intensity?

• no change in energy

• decrease in intensity

Inverse Sqaure Law

mAs2/mAs1 = (SID2)2/(SID1)2

Dosimeter Placement for Routine Radigraphs

collar level with no PPA

Dosimeter Placement for Fluoro

outside the apron at collar level

Dosimeter Placement for IR

1. outside the apron at collar level

2. second montior for lengthy IR procedures should be placed under the apron at the waist level

Dosimeter Placement for Pregnant MRT

second monitor placed under the apron, at waist level