rad protection unit 3

What is ‘lead-lined metal that protects personnel and patients from leakage and off-focus radiation’?

Protective Tube Housing

Protective Tube Housing cannot exceed more than how much mGy per hour?

1 mGy per hour at 1m away from housing (Air Kerma of 0.88mGy/hr)

Should anyone be touching the x-ray tube housing during an exposure?

NO!

What is the technologist workspace where you can set up the console, technique, and take the exposure?

Control Panel/Console

What are some characteristics of the Control Panel/Console?`

• Properly shielded barrier

• Exposure button must be affixed to the console so the exposure can’t be taken in an unshielded area

• Displays when the x-ray tube is energized

What does kVp stand for?

kilovoltage peak

What is the ‘maximum possible energy of a photon that exits the x-ray tube, this is a unit selected on the operating console’?

kVp

What is indirectly proportional to patient exposure?

kVp

What does mA stand for?

milliamperage

What is ‘measurement of x-ray tube current or the number of electrons crossing the tube from cathode, this is a unit selected on the operating console’?

mA

What is directly proportional to patient exposure?

mA and mAs

What does mAs stand for?

milliampere secondsControls the amount of radiation produced by the x-ray tube

What controls the amount of radiation produced by the x-ray tube?

mAs

What does AEC stand for?

Automatic Exposure Control

What is it called when ‘exposure will terminate when a predetermined amount of radiation is reached for the selected body part’?

AEC

What can only be used on body parts big enough to cover the cells?

AEC

What will SID be accurately measured?

digital or tape measure

What “limits the primary beam to a smaller area, decreases exposure by reducing the amount of tissue that is exposed to radiation, reduces scatter?'“

Beam Limiting Devices

What are the 3 types of Beam Limiting Devices?

• Aperture diaphragm

• Cones

• Collimators

What is the Aperture Diaphragm?

Flat lead with a shape and size cut into it that is placed below the window

What is the most common Aperture Diaphragm?

Rectangular

Does an Aperture Diaphragm reduce scatter?

Yes, it does reduce scatter

What are circular metal cylinders connected to the tube housing that limit the size of the beam?

Cones

What are characteristics of cones?

• Can be flared or straight

• Can be telescoped (10-12 inches) for smaller exposure area called extensive cylinders

• Have mostly been replaced by collimators

• Mostly used in dental radiography but can be used for the heel, skull and spine imaging

What is a light-localizing variable-aperture rectangular item?

Collimators

What are attributes to collimators?

• Must be bright enough to outline the anatomy to include

• Most versatile beam restriction

• Can change size

• Should not be opened larger than the size of the image receptor or body part being imaged

• Post shuttering- part of ASRT Practice Standards

• Can reduce exposure by 20-30%

• Careful not to over collimate which causes repeat images

What are 2 sets of shutters 90 degrees from one another?

Collimators

What are the Near (upper) part of the Collimator?

• Located close to the window

• reduces exposure from off-focus radiation

What are the Far (lower) part of the Collimator?

• Located closer to the light source

• confines the beam to the area of interest

What is Skin-Sparing?

• Minimizes skin exposure by requiring a 15 cm distance from the skin to the collimator

• Can be achieved with spacer bars mounted on the tube

What does PBL stand for?

Positive Beam Limitation

What are electronic sensors in the bucky that sense the image receptor size that you are using and open the light field to that size?

Positive Beam Limitation

What reduces user errors by matching the light field to the image receptor size?

Positive Beam Limitation

What is the same term as automatic collimation?

Positive Beam Limitation

What ‘hardens the beam by cleaning up the low energy (longer wavelength) x-rays’?

Filtration

What reduces the skin and superficial exposure to the patient?

Filtration

What decreases patient’s absorbed dose because the remaining photons are higher energy (shorter wavelength)?

Filtration

What lowers energy photons (which were removed) would be more likely to be totally absorbed and provide no detail to the image?

Filtration

What is the total filtration built into the housing is operating above 70kVp?

2.5mm Al equivalent for units

What are 2 types of Filtration?

Inherent and Added

What material is connected with Filtration?

Aluminum

What is the Al equivalent to Inherent Filtration?

0.5 mm

What is the Al equivalent to Added Filtration?

2.0 mm

What are types of Inherent Filtration?

Glass envelope, insulating oil, and glass window

What are types of Added Filtration?

• Sheets of Al were added outside the glass window above the collimator shutters

• Accessible by a service person

• Can be changed as the tube ages

Diagnostic x-ray beam must always have adequate filtration according to which NCRP report?

#102

What is the Half value layer test?

• Measures beam quality or effective energy of the beam

• Measured at least once a year by a physicist or if the tube is replaced or repairs are made

How does intensity decrease with filtration using HVL?

Intensity Decreased:

1 HVL= 50%

2 HVL= 25%

3 HVL= 12.5.%

4 HVL= 6.25%

What does an Insufficient HVL test mean?

improper filtration

What is TVL?

Tenth value layer- thickness that will decrease the intensity of the beam by 1/10th

What is used when x-raying a part that has varying thickness to reduce dose and provide a uniform density across the image?

Compensating Filters

What decreases the entrance skin exposure (ESE)?

Compensating Filters

What is constructed of aluminum or lead-acrylic that is attached to the bottom of the collimation?

Compensating filters

What is a Wedge filter used for?

Foot and spine

What is a Trough filter or bilateral wedge used for?

Used on chest x-rays

Thicker on both sides and thin in the middle

What is Ferlic used for?

Hips

What is Boomerang used for?

Shoulders

What is this, and what is this used for?

Wedge filter, foot and spine

What is this and what is it used for?

Trough Filter (bilateral wedge), used for chest x-rays

What is this and what is it used for?

Ferlic Filter, Hips

What is this and what is it used for?

Boomerang Filter, shoulder

What is Exposure Reproducibility?

System must duplicate exposure when taken at the same exposure

What is the variance amount of Exposure Reproducibility?

5%

What is Exposure Linearity?

The system must consistently produce radiation output when mA and time are changed

What is the variance amount of Exposure Reproducibility?

10%

What is the material of Radiographic Grids?

parallel radiopaque material of very thin lead, aluminum or plastic fiber

How is the quality of an x-ray if scatter does not reach the image receptor?

Better

What is the Rule of thumb is to use a grid when the part thickness is over what amount?

12cm at 60 kVp or higher

Grids _______ patient dose but _______ the quality of the image which provides a better diagnosis.

Increase, improves

What is Grid ratio?

height of lead strip divided by distance between strips

What is the difference between higher and lowest grid ratio?

Use the lowest grid ratio (ex. 6:1) sufficient for the body part

Higher grid ratio (ex. 12:1)= higher patient dose

What is the minimal source to skin distance on a mobile fluoroscopy unit?

12 inches (30 cm)

The ______ the source to skin distance the ______ the entrance exposure.

smaller, larger

Who do we only perform portable x-rays on?

Patients that cannot be transported to the department

What are the different aspects of Digital Imaging?

• Just because the image can be electronically manipulated, does not excuse overexposing the patient

• Utilization of technique charts

• Grids

• Digital Radiography (DR) has lower doses, immediate images, image manipulation, less maintenance

What is the largest exposure to patients in diagnostic radiology?

Fluoroscopy

What are all the ways to limit exposures in Fluoroscopy?

• Image Intensification

• Increases brightness on screen

• Intermittent or pulse fluoro

• Limit magnification mode

• Limiting field size

• Technical factors- patient size appropriate

• Filtration

• Reduces skin dose

• Source to skin distance

• NCRP states 15 inches (38 cm) for fixed units and 12 inches (30 cm) for mobile

What is the Source to skin distance for fixed units?

15 in (38cm)

What is the Source to skin distance for mobile units?

12 inches (30 cm)

What is the Cumulative timing device?

Audible alarm or interrupt of fluoro every 5 minutes of time

What is the technologist responsible for in the electronic medical record?

to record the fluoro time and dose

Federal regulations tabletop exposure rates should not exceed how much?

88 mGy per minute

What is Automatic Brightness Control/ Stabilization (ABC/ ABS)?

No matter the kVp or mA varying, the brightness of the image remains the same

What is Automatic Exposure Rate Control (AERC)?

Adjusts exposure factors automatically as the beam moves over varying thicknesses

What are ‘foot pedals that requires direct pressure to continue fluoro exposure’?

Fluoro Exposure Switch/Dead Man Switch

What is C-arm Fluoroscopy used in?

OR, Cardiac Cath, and IR

What is the minimal distance to the patient in C-arm Fluoroscopy?

12 inch (30 cm)

What are usually placed to maintain a safe distance in C-arm fluoroscopy?

Spacers

Why should C-arm should be positioned with the II on the top?

Reduces scatter and patient dose

What is beam turns off while image is scanned and then turns back on, pulsed?

Digital Fluoroscopy

What is Dose Area Product (DAP)?

Newer fluoro systems provide the sum of the air kerma (energy) over the exposed area of the patient

What is Last image hold?

When the foot comes off the pedal, it holds the last image and displays it on the screen until the foot pedal is activated again

What is Digital Subtraction Angiography (DSA) used in?

• Used in interventional and vascular

• Used to visualize occlusions, stenosis, or aneurysms

• Uses software to remove superimposing anatomy so you only see the area of interest

What is Interventional Radiology?

Invasive sterile procedures performed by a physician under fluoro (ex. Drainage, biopsy, occlusions)

In IR, FDA requires documentation in the patient chart if skin dose is how much?

1-2 Gy

Federal regulations for table-top exposure rates for procedures with high level control fluoro (HLCF) exposure limits are how much per minute?

176 mGy

What are different parts of Equipment Safety?

• On and off switches

• Interlocks

• Detents

• Fluoro locks

• Visual/ audio monitors

• Control panel

• Laser light

• Tape measures

• Emergency controls

CQ: What is the function of the AEC?

Automatically terminates when a predetermined amount of radiation is reached for the body part

CQ: What type of filter could be used to perform an AP foot?

Wedge

CQ: What is the total amount of filtration required for diagnostic x-ray equipment?

2.5mm Al