RAD 208 Equipment design

A tube housing is required to protect the patient and imaging
personnel from ?

Leakage radiation (off-focus)

Any radiation that doesn’t exit glass window

Leakage radiation

A tube housing is designed so that leakage radiation is measured at what distance from the x-ray source?

1 meter

Tube housing is designed so that leakage radiation does not exceed how much intensity?

100 mR/hr

What are the types of radiation produced in an x-ray room

Primary

Leakage

Scatter

A control panel is located where?

behind protective barrier

What is mandatory for a control panel to have when x-ray tube is energized?

positive indication (can be a sound or light to indicate exposure was taken)

The technical factors in a control panel should or should not be adjustable?

should be

what type of exposure button should control panels have?

Affixed behind the booth (protects techs by keeping them behind booth for exposure)

The x-ray table is made out of what material?

carbon fiber

Why must x-ray tables be made out of carbon fiber?

so minimal x-rays absorbed and reduces PT dose

What film screen is best to reduce PT dose

Higher screen speed

What the common speed for a screen film in general x-ray

400 speed system

Provides a way to measure the distance from the anode focal spot to the image receptor (IR) to ensure that the correct SID is maintained

Source to image receptor distance

what is also used to measure SID

lasers

Tape measure attached to the tube housing

Source-to-Image Receptor Distance Indicator should be within how much of the indicated SID

2%

Used to minimize skin exposure to elections produced by photon interaction with the collimator

Skin Sparring

The patients skin surface should be how much below the collimator for fixed radiographic equipment

15 cm

The patients skin surface should be how much of source to skin distance for mobile radiographic units

30 cm

Most popular  is a light-localizing variable-aperture rectangular

collimator (predominant x-ray beam limitation device)

Purpose of a collimator

reduce scatter

The x-ray beam & the light beam must coincide how much w/ the SID

2%

A Positive Beam Limitation (PBL) is also known as what

automatic collimation

For PBL a tech must insure what ?

that collimation is adequate to the IR being used

PBL must be within how much of the SID

2%

Refers to brightness of a surface over a particular field of view

Luminance

Quantifies the intensity of a light source

luminance

what’s the unit for Luminance

•candela per square meter (nit)

Luminance is determined by measuring the concentration of light

over a particular field of view

Total filtration is how much in a tube?

2.5 mm/Al operated above 70 kVp

How much total filtration when operated between 50-70 kVp

1.5 mm

How much total filtration when operated below 50?

0.5 mm

What material is most common for filtration

Aluminum

When should HVL be measured?

once a year, or when x-ray tube is replaced or repair

What is the purpose of radiographic beam filtration?

To increase beam hardness, thereby reducing patient skin dose and the dose to superficial tissues

Used to accomplish dose reduction and uniform imaging of body parts that vary considerably in thickness or tissue composition

Compensating Filters

Consistency in output in radiation intensity for identical generator settings from one individual exposure to subsequent exposures. (Same kVp and mAs)

Exposure Reproducibility

For Exposure Reproducibility what variances is acceptable?

5% or less

Consistency in output radiation intensity at selected kVp settings when settings are changed from one mA and time combination to another

Exposure Linearity

The ratio of the difference in mR/mAs values between two successive generator settings to the sum of those mR/mAs values. It must be less than 0.1

Linearity

When settings are changed from one mA to a neighboring mA station, the most that linearity can vary is

10%

Minimum SSD of at least how much for mobile x-rays

30cm

Exposure switch for mobile is how long?

2m or 6ft

Where should the tech be standing when exposing a PT in a mobile study?

90 degrees from source

What radiographic procedures produce the largest PT radiation exposure rate?

Fluoroscopy

a radiation-reduction technique where the X-ray beam is produced in short, rapid bursts rather than a continuous stream

Intermittent (Pulsed) Fluoroscopy

Because radiation is produced only during pulses, the total exposure time is reduced and reduces PT dose

The tube has cooling time between pulses, reducing heat buildup. Less continuous exposure means less stress on the tube components.

Benefits of pulsing fluoro

Limiting the field size means restricting the x-ray beam to only the area of clinical interest using collimation some benefits are

• Reduces patient radiation dose

• Decreases scatter radiation

• Improves image contrast

• Reduces radiation exposure to staff

Regulations require that the x-ray beam cannot be larger than the image receptor or monitor display area

Fluoroscopic beam length and width limitation

Primary protective barrier in fluoro?

Fluoroscopy IR assembly (2mm of lead equivalent required)

A features that increase patient dose in fluro

Magnification mode

Why does magnification mode increase PT dose

An Increase in mA is needed to maintain a image quality as FOV decreases, thus resulting in increase patient dose

Selection of technical exposure factors for adult patients for fluro

75-100 kVp

SSD should not be less than what for stationary fluoro?

38cm (15in)

SSD should not be less than what for mobile fluoro?

30cm (12in)

Designed to ensure that the radiologist is aware of the relative beam-on time during each procedure

Cumulative Timer

When fluro time has exceeded the cumulative timer makes an audible sound after how many minutes

5 min

Position of the input phosphor surface of the image intensifier in relation to the patient should be maintained as close as is practical for what reason?

to reduce PT entrance exposure rate

How much technical exposure factors (kVp) for children be decrease in comparison to adults

25%

Depending on the area of the body being examined with a fluoroscopic image intensification system, for adult patients a range of … kVp is generally used

75-110

Portable x-ray unit that is C-shaped Has an x-ray-tube attached to one end of its arm and an image intensifier attached to the other end. Frequently used in the operating room for orthopedic procedures, cardiac imaging, interventional procedures, and other potentially lengthy tasks

C-arm

the last image formed remains on the monitor so that no further radiation exposure is needed to regenerate it

Last image hold

For Mobile C-Arm Fluoroscopy the Source-to-end of collimator assembly distance is required to be a minimum

30cm (12in)

Patient-image intensifier distance should be kept how?

as short as possible

To reduce PT dose how should the C-arm be position?

preferably under PT

With the C-arm x-ray tube positioned under the patient, scatter radiation is what

less intense

When the C-arm x-ray tube is positioned over the patient, scatter radiation becomes more intense, and radiation exposure of personnel increase or decreases?

Increases

is a quantity that reflects not only the patient radiation dose but also the amount of tissue irradiated

Dose Area Product (DAP)

DAP increases w/ increase field size and decreases w/ decrease field size while dose remains unchanged

DAP detectors positioned just after the collimators before the beam enters the patient

Unit of DAP

mGya-cm2

A DAP meter registers 625 mGy-cm^2 at 70 SID. The SID is then changed to  50SID. Now what is the patient DAP?

SID doesn’t affect DAP

Any wall to which the useful beam can be directed

Primary barrier

The intensity of scatter radiation 1 m from the patient is approximately … of the intensity of the useful beam at the patient

0.1%

Designed to shield areas from secondary radiation. Less thick than primary radiation

Secondary protective barrier

an area that can be occupied by anyone

uncontrolled area

The uncontrolled area has a limit of how much per year and week

week→2mrem/week

year→100mrem/year

It should ensure that no individual will receive more than 2.5 mrem/hr

protective barrier

During fluoroscopy the exposure to the collar is … times greater than the exposure to the trunk of the body under a protective apron

20

Every radiology department should provide a radiation safety program that includes…

training new employees

periodic in-services for all employees

counseling during pregnancy

The preferred way to hold patients who are unable to support themselves is to use a…

restraining device

A reasonable safeguard against accidental irradiation of a pregnant patient would be…

to post warning signs in the department

For diagnostic x-ray personnel, the highest occupational exposure occurs during… exams

Fluoroscopy

mobile radiography