Patient Protection (full) (RADS 349)

Gonadal Shielding can reduce dose to the gonads by

90%

Gonads are considered a

critical organs as it is sensitive tissur and will effect future generations

-important to protect

Hospital Rule for Shielding

shield all males and females under the age of 65

The NCRP states that gonadal shielding SHOULD NOT be used on...

Abdomen or Pelvis radiography, may obscure anatomy of interest

When using Automatic Exposure Control

it can cause increase in exposure when used improperly

flat or contact type shield

can be simple as folding an apron or pieces of lead

Advantages of Flat or Contact Type Shield

-Inexpensive

-can be used with patient prone or supine

Disadvantages of Flat or Contact Type Shield

-Difficult to use in upright position

-Difficult to use in lateral and obliques

-Not appropriate in sterile Fields

-Requires manipulation by technologists

Which Gonadal Shielding is for Males Only?

Shaped Contact Shield

Advantages of Shaped Contact Shield

no manipulation by tech, can be used in upright/ lateral/ obliques

Disadvantages of Shaped Contact Shield

initial cost is expensive, has to be cleaned, no protection on PA view

Shadow Shields

Shields made from a radiopaque material (lead) attached and suspended from the collimator

Newer Type of Shadow Shield

Clear Lead Shields that slide on the collimator

advantages of shadow shields

always ready for use, no manipulation by tech, good for sterile fields

Disadvantages of shadow shields

initial cost is expensive, cannot be used with cones, may be misalignment of light beam, cannot be used for fluoro

Best gonadal shield for sterile fields

shadow shields

The best shield for protection of sensitive organs is

a qualified/certified radiographer

Primary interest for gonadal shielding

apply it when performing seated upper extremity radiography

Optimum kVp for fluoroscopy

85-100

Optimum mA for fluoroscopy

1.5-2 (max. is 10)

3 measures techniques for skin dose

-thermoluminescent dosimeter

-monogram

-yearly survey

Skin dose (Entrance Skin Exposure)

overall patient dose, most widely used because easiest to measure and is reasonably accurate

Thermoluminescent Dosimeter (TLD)

tapped on patients skin in center of x-ray field

-accurate within 5%

Nomogram

uses output intensity of radiographic unit if technique is known and applied it to an established graph to get skin dose

-output intensity varies widely, so only accurate within + or - 50%

Yearly Survey

performed by a physicist establishing an output for the machine in mR/mAs or mR/100 mAs at specified distance

-26 or 32 in. (SOD), or 40 in. (SID)

When is comes to imaging you want to use the highest speed imaging system, this would be?

Digital Radiography, if you use CR it is an ALARA violation

Filtration

lowers skin dose

For a scoliosis series you should use...

breast shields

To calculate skin dose from yearly survey you must know

intensity of radiation varies directly with the square of the change in kVp, if we double kVp intensity increase intensity by a factor of 4 (higher kVp is higher skin dose)

Intensity & kVp formula (skin dose)

I1/I2 = kVp1^2/kVp2^2

-direct relationship

inverse square law formula

I1/I2 = D2^2/D1^2

patient thickness is expressed in

cm, 1 in. = 2.54 cm

Estimate for fluoroscopic skin dose

0.02 Gya/mA-min

mean marrow dose (MMD)

average dose of radiation to the entire bone marrow system

-there are charts for obtaining estimates of % of bone marrow for different body parts

Genetically Significant Dose (GSD)

radiation dose to the population gene pool, genetic effects of radiation (effects future offspring)

-gonadal dose which if received by every member of the population would be expected to produce the total genetic effect in the population as the sum of the individual doses actually received

estimated GSD for US

20 mrad, higher than other countries

Sigma (GSD Formula)

sum

D (GSD formula)

average gonadal dose per exam

Nx (GSD Formula)

Number of people recieving exam

Nt (GSD Formula)

total number of people in the population

P (GSD formula)

expected future number of children per person

Genetically Significant Dose (GSD) is influenced by:

age

sex

number of offspring

type of examination

number of people

If it's a bucky exposure or we don't know what it is you subtract how much from the SOD

4 inches

If it's CR or a Cassette exposure we subtract how much from the SOD?

3 inches