1. Unit 4 Radiation Protection RAD 101
Protection of the Patient and Technologist During Diagnostic Radiography

2. Objectives
Explain the need for effective communication between the radiographer and the patient.
Explain the significance of adequate immobilization of the patient during a radiographic exposure.
Describe the various beam-limiting devices and identify the device which best confines the radiographic beam.
Explain the function of x-ray beam filtration in diagnostic radiology.
State the reason for using gonadal shielding during radiologic examinations and identify the types of shields used.
Discuss the need for using appropriate exposure factors for all radiologic procedures.
Explain how the use of IR combinations reduces radiographic exposure for the patient.
Discuss the value of good radiographic processing techniques in reducing radiographic exposure for the patient.
State the reason for reducing the number of repeat radiographs.
Explain how patient exposure can be reduced during fluoroscopic procedures

3. Equipment Design for Radiation Protection
Chapter 11

4. Equipment Design Control Panel Tube housing
Must be behind protective barrier w/ window
Must indicate condition of exposure and have light or audible x-ray indicator
Tube housing
Must be lead lined metal (protective tube housing)
Protects from off-focus or leakage radiation
Leakage can not exceed 100mR/hr at a distance of 1 meter when operating at the highest voltage
Table
Uniform thickness
Radiolucent- absorbs only minimal amount of radiation- commonly carbon fiber
SID
Must have a means of measurement from anode focal spot to IR
Distance must be accurate to 2% of SID
Centering must be accurate to 1% of SID

5. Beam Limiting Devices
Devices that limit the x-ray beam before it enters the patient
Benefits
Amount of tissue irradiated is less
Dose received is less
Amount of scatter radiation produced in the body is less
Image quality is improved
Types
Aperture diaphragm – fixed and variable
Cone/cylinders
Collimator

6. Aperture Diaphragm Lead square with a fixed circular opening-fixed
Placed below ( under) the tube
Restricts the beam dimensions to a given size
Pg 236

7. Cones/Cylinders
Fixed aperture device consisting of an extended metal structure
Cone – flared metal tube
Cylinder- straight tube , more restricting-
Longer cylinders are more restricting
Slide into attachment under tube housing
Uses:
Dental, detail , sinuses, spot L-spine

8. Collimators “Variable aperture or variable rectangular” Most versatile
More control over beam limitation
2 sets of shutters
1st set reduces off focus radiation from the primary beam- located below tube window
Off focus- radiation in tube that results from electrons hitting areas other that the focal spot)
2nd Set- 2 pairs; each pair can be independently adjusted- located below the light source and mirror
Most machines have PBL- positive beam limitations – but can be reduce further
NCRP requires light field to be accurate to no more than 2% of the SID
40” x2%= .8 “ of light showing around cassette

9. Filtration
The process of eliminating undesirable low-energy x-ray photons by the insertion of absorbing materials into the primary beam
Effects of filtration
Increase quality of the beam because boo penetrating x-rays are left- Beam gets “hardened”- removes low energy
Decreased quantity of x-rays- by absorbing some low energy beams- fewer overall beams are left
Reduces patient dose- especially to skin and superficial tissue
2 types
Inherent
Added

10. Inherent filtration Result of tube and housing composition
Glass envelope surrounding tube
Oil that surrounds tube ( oil helps in heat dissipation)
Glass window- most of inherent comes from here
Typical x-ray tube may have total inherent filtration of mm Al equivalent

11. Added Filtration
Any filtration occurring outside the tube and housing and before the IR
The collimators themselves are considered added filtration – avg 1.0mmAl eq.
Sheets of Al also added after tube window
Al is considered standard filtering material
All filtration is expressed in Al equivalences
Inherent + Added = total filtration
Operating levels require certain amts of filtration per NCRP #102
When filtration is increased, technical factors must be increased to maintain same density on film
Although exposure needs to be increased to pt, there is still a greater decrease in overall exposure to pt with filtration

12. Require Filtration NCRP #102 Box 11-2
OPERATING kVp
Total filtration Required (HVL)
Below 50kVp
.5 mm Al
50-70 kVp
1.5 mm Al
Above 70 kVp
2.5 mm Al
Mobile & fluoro units

13. Half Value Layer - HVL
The amount ( thickness) of an absorber ( Al) required to decrease the intensity of the primary beam by ½ (50%) of its original value
Expressed in terms of Al equivalent
Physicist measures beam quality
Shielding devices use HVL
TVL- amount of shielding required to reduce the radiation intensity to one-tenth its original value

14. Compensating Filters Placed outside under collimators
Placed outside under collimators
Designed to solve a problem of unequal subject densities
Adds an absorber to compensate for unequal absorption with the subject
Result – overall absorption of primary beam will be more equal and even densites on radiograph ( one end won’t be black and other underexposed)
Made of aluminum, leaded plastic or plastic ( acrylic)
Types
Wedge – bone and joint – T-spine, feet
Trough ( bilateral wedge) CXR-PA

15. Reproducibility/ Linearity
Consistent output in radiation intensity for identical generator setting from one exposure to the next
Any combo of kVp,mA and time
Variance of 5% or less
Linearity
Consistent output of radiation intensity at any selected kVp setting when generator setting are changed from mA/time combo to another
Cannot exceed 10%

16. Image Receptors Film Screen – CR- computed radiography
intensifying screens – convert x-ray energy to visible light- screens have phosphors ( crystals) that luminesce(give off visible light) when struck by x-rays
Screen-Speed- how fast a screen is capable of converting x-rays to light
Slow screens need more radiation to produce same density- higher pt dose but better detail
CR- computed radiography
Photostimulable phosphor plate- aprox equal to 200 speed screen film
Dose creep- results from practice of overexposing patients to create good images and avoid repeat images
DR- digital radiography
Latent image is formed by x-ray photons on a radiation detector- electronic latent image
Matrix size and pixel size determine image detail
Reduction in repeats reduce overall patient dose

17. Grids
Devices that remove scattered x-ray photons that emerge from the patient before the scatter reaches the film
Improves contrast and visibility of detail- image quality
Placed between the patient and IR
Pt dose will increase because bore technique is necessary
Used when thickness of part is >10cm
Made of alternating strips of lead and aluminum or plastic
Come in varying grid ratios- the higher the grid ratio the more grid lines-better absorption of scatter- higher patient dose

18. Dose Reduction for Mobile X-Ray ( portable)
Mobile radiography requires SSD of at least 30 cm (12 inches)
Recheck your positioning
Check previous radiographs for exposure factors, SID and body habitus – useful for CXR
Use high kVp technique ( gives a wider margin for exposure error and reduces dose)
Shield pt
Collimate
Warn personnel and family to reduce their dose- have family leave room

19. Dose Reduction during Fluoro
X-ray exam is performed and demonstrates dynamic, or active, motion of selected anatomy- real time (Regular x-ray is considered static images )
Use intermittent rather than continuous beam on
Dead-man switch for foot pedal must be equipped- fluoro only when switch is depressed
Collimate
Filtration of 2.5 mmAL required
Exposure rate cannot exceed 10R/min
5 minute reset timer- audible

20. Dose Reduction during Fluoro
Bucky slot shielding device of at least .25mmPb is required
Protective curtain min .25 mm lead
Stationary Fixed Fluoro SSD no less that 38 cm ( 15 inches)
Mobile fluoro (c-arm) requires SSD of at least 30 cm (12 inches)
Cannot operate in parked position
Primary protective barrier must be 2mmPb equivalent
Lower exposure factors for peds
Fluoroscopically Guided Positioning (FGP)
Practice of using fluoro to determine exact location of the central ray before taking a radiographic exposure
ASRT says “ unethical practice that increases patient dose”

21. Management of Patient Dose
Chapter 12

22. Effective Communication
“ The holistic approach” the use of verbal messages and body language to communicate with your patient
Advantages:
Reduces patient anxiety
Creates better tech/patient relationship- trust and caring
Increases chance of completing exams and reduce repeats
Consists of :
Clear concise instructions
Give patient time to ask questions and answer truthfully
Listen and offer empathy
Respond according to ethical guidelines
Don’t overemphasize pain ( may cause more anziety)

23. Immobilization
Sometimes needed based on patient and exam being performed
Reduces motion
2 types of motion
Voluntary- patient controlled
Age
Breathing
Fear
Involuntary- body systems
Muscle spasms
Chills
Tremors
Shortened exposure time while maintaining mAs ( high mA , low seconds)
Good instructions

24. Protective Shielding
Devices made of lead or lead impregnated materials that will adequately attenuate ionizing radiation
Should reduce or eliminate radiation doses that can cause biological damage
Areas that should be shielded
Eyes
Breasts
Reproductive organs
Types of shields
Gonadal
Flat, shadow, shaped, clear
Specific area shielding
Breast, thyroid

25. Gonadal Shielding
Used to protect reproductive organs when organs are within 5cm of the beam
Used unless it will compromise the exam (pelvic, abdominal )
Females receive 3 x the exposure to reproductive organs than males during exams of the pelvic region
Female dose- can be reduced by up to 50% with contact shield – placed 2.5cm medial to ASIS
Male dose- can be reduced by up to 90-95% with contact shield- placed below symphysis pubis

26. Types of Gonadal Shielding
Flat contact shields
Lead strips
Placed directly over patient’s reproductive organs
Best when used in AP or PA recumbent position
Under the patient during fluoro
Shadow shields
Made of radiopaque material
Suspend from above the tube collimator box
Hang over patient and shadow area to be shielded- gonad and breast
Can’t use during fluoro
Can use during sterile procedures
Reduce patient embarrassment

27. Types of Gonadal Shielding Cont’d
Shaped Contact shields
1 mm of lead and are contoured to enclose male
reproductive organs
Can be used with disposable or washable briefs
Can be used for recumbent or nonrecumbent positions- AP, oblique, and lateral – not for use with PA projections- only covers anterior and lateral
Can be used for fluoro exams
Have patient place when changing for exam
Clear Lead Shields
Transparent lead acrylic impregnated with approx. 30% lead by weight
Can be gonad and breast shielding for scoliosis exams

28. Specific Area Shielding
Used for radiosensitive organs and tissues
Thyroid
Breast ( or PA positioning can reduce dose)
Eyes
Can be contact, shadow or clear plastic

29. Technical Exposure Factors
Essential to ensure a diagnostic image with minimal patient dose
Images must have:
Sufficient density (brightness) to display structures
Good contrast to differentiate structures
Maximum special resolution( detail) and minimal distortion
Low quantum noise or mottle – results from insufficient technique

30. Technique Charts
Used when AEC ( automatic exposure control) is not used
Standardized set of techniques based on equipment and patient size
Departments establish own protocols
Ensures consistency
Minimizes errors if used correctly

31. SAMPLE TECHNIQUE CHART

32. Exposure Factor Typically high kVp and low mAs will reduce dose
Increasing kVp by 15% and reducing mAs ( ½) will reduce radiation exposure
Select the highest practical kVp within optimal range for the position and part along with sufficient mAs that will produce and optimal radiograph

33. Radiographic Processing
Of main concern with film-screen imaging
Correct processing promotes archival quality
Inadequate processing will produce poor films leading to repeats and extra exposures
Digital Imaging- also concern on post-processing
Artifacts
Software problems

34. Quality Control Program/ Repeat Analysis Program
Ensures standardization in processing in film and digital
Regular monitoring and maintenance of processor and image display
Types of QC
Acceptance testing
Calibration
PM schedule
Repeat analysis program
Repeats and reasons for repeats are evaluated
Increases awareness about quality of images
In-service if consistent problems arise

35. The Pregnant Patient Screen all women of child bearing age Ask LMP
Some hospitals have specific ages outlined
Ask LMP
NCRP- Elective exams should be completed in the first few days after the onset of menses to minimize possible radiation of an embryo.
“Ten day rule” ICRP for woman of reproductive age. States that "whenever possible, one should confine the radiological examination of the lower abdomen and pelvis to the 10-day interval following the onset of menstruation.”
Consideration for replacing with 28 day rule. Pt is considered not pregnant until a menstrual period is skipped then they are until proven otherwise.
Shield is recommended if the ovaries and uterus are less than 5 cm from edge
Some facilities will require HCG

36. Figuring Fetal Dose List in as much detail about the x-ray exam
Projections
Number of views
Film size
Technique
SID
Shielding used?
Patient thickness
Fluoro time
Number Spot films taken
Report information to RSO or Medical Physicist- they will determine EqD

37. Management of Tech Dose
Chapter 13

38. The Patient as a Beam Emitter
During the exam- the patient becomes a source of radiation for the tech- scattered radiation because of Compton interaction
Greatest occupational hazard
Lowest scatter area is at to the patient
Ways of reducing
Beam limiting devices –PBL
Filtration- (primarily benefits pt)
Protective apparel
Technical factors
Cardinal principles
Structure of dept

39. Protective Apparel Lead aprons, gloves and shielded barriers
Protect from secondary ( scatter and leakage)
Standard apron thickness .5 mm lead equivalent at 100kVp reduces by 75%
.25 mm is minimum (mammo) 1 mm is maximum ( rare because of weight)
Lead should be hung on racks or draped over a bar- never folded or crunched
Must be inspected yearly for integrity ( use high kVp to reduce dose)
Thyroid shields- .5 mm lead
Glasses .35 mm lead
Gloves .25 mm lead

40. Cardinal Principles (Time, Distance, Shielding )
The most effective means of protection from ionizing radiation
Inverse Square Law
Expresses the relationship between distance and intensity ( quantity) of radiation
“The intensity of radiation is inversely proportional to the square of the distance from the source”
Decrease in radiation intensity physically occurs because of the area-
Expressed as an equation:
I 1 = (d2)2
I (d1)2
Where : I 1 = original intensity & I2 = new intensity
(d2)2 = new distance & (d1)2 = original distance

41. Practice Problem
If a radiographer stands 3 m from an x-ray tube and is subjected to an exposure of 9mR/h, what will the exposure be if the same radiographer moves to a position 6 m from the x-ray tube?
I 1 = (d2) = (6)2
I (d1) I (3) cross multiply
36I2 = divide
I2 = mR/h

42. Protective Structural Shielding
Primary Protective Barrier-
prevents DIRECT or unscattered, radiation from reaching personnel or public
perpendicular to line of travel of primary beam
1/16 inch lead
Extends 7 feet
Secondary Protective Barrier-
protects against leakage and scatter-
Any wall or barrier that is never struck by primary beam
Located parallel to the direction of the beam
1/32 inch lead
Extends to ceiling and should overlap primary by 1/2”
Includes ceiling and control booth
Doors are considered secondary 1/32 inch lead – must remain closed during exposure

43. Protective Structural Shielding
Control Booth Barrier- considered secondary barrier
Permanent or nonportable equipment require permanent control booth
Should be positioned where x-rays scatter a min of 2 x before reaching behind barrier
Contains window for personnel 1.5 mm lead equivalent ( can be .3-2 mm)
Max allowance of 1 mSv (100mrem) per week
Exposure cord must be short enough that the tech cannot operate outside booth
Tube should never be pointed at control booth
Ceiling mount - Overhead lead acrylic
Used during special procedures
Typically .5 mm

44. Workload Used to determine barrier shield requirements
Since x-ray units do not have constant on-time a formula is used to determine approx. amount of radiation “output-weighted time”
Expressed in mAs per week or mA-min per week
Workload (W)= mA x time x days per week x #pts x #img per pt

45. Use Factor & Occupancy Factor
If no one will ever be present beyond an existing wall- no additional shielding is needed ( courtyard)
Use Factor- the factor that represent the portion of beam-on time that the x-ray beam is directed at a primary barrier during the week ( table 13-2 pg 328)
Occupancy Factor- use to modify shielding based on the fraction of the work week during which the space beyond the barrier is occupied (table 13-3 p 329)
Controlled area- used only by x-ray personnel
1mSv (100mrem)
Uncontrolled area- general public – hallway, stairwell
Weekly max dose 20microsieverts ( 2mrem)

46. Caution Signs
Posted signs warning for radiation “Catution” and radiation symbol : Must be magenta, purple or black on a yellow background Must read: “Radiation Area” “High Radiation Area” “Very High Radiation Area” Departments usually have “If you think you are pregnant please tell the technologist”

47. Where to stand during exams
Fluoro
Stand as far away from the patient as practical or behind radiologist
Book recommends control booth….. Usually not practical
Portable
Cord must be 6 foot
90 degrees to beam
C-arm
As far as achievable – use of foot pedal for exposure helps
Position image intensifier as close to patient as possible ( decreases scatter)
If possible place tube under table and image intensifier over table

48. Holding Patients DO NOT stand in primary beam to restrain patient
Use mechanical holding devices first : tape, Pigg-O-Stat
Use nonoccupational persons second– family / parent / ancillary staff/ nursing
Order
Male relative
Female relative
Nonradiology personnel
Radiology personnel
Always provide lead
Pregnant women are never to hold patients
Rotate human holder
Resources:
Radiation Protection in Medical Radiography by Mary Alice Statkeiwicz Sherrer, Paula Visconti, E. Russell Ritenour and Kelli Welch Haynes. 6th and 7th Edition. Elsevier online.
Essentials of Radiographic Physics and Imaging. James N. Johnston and Terri L Fauber. 1st Edition. Elsevier Online.

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