Rad T 110

1. Rad T 110 Radiation Monitoring and Protection

2. Personnel Monitoring • Required when a worker may receive 10% or more of the annual MPD • Typically monitoring is done when 1% is expected • Placement • Collar level • Outside the apron if used • Second may be used for pregnancy • Extremity monitors also

3. Types • Film badges • 10 mrem to 500 rem • Cheap • OSL; MC device today • Aluminum oxide which is read by a laser • Typically worn for 2 months • 1 mrem and sensitive to 5 keV to 40 MeV of energy

4. Types cont. • TLD • Lithium floride • Reasonably sensitive • Cannot be re-read • Pocket ionization chambers • Good for immediate feedback • Not very reliable • Sensitive to mechanical energy

5. Dosimetry Reports • Deep • Eye • Shallow doses

6. Patient Protection • Effective Communication • Verbal messages • Concise instructions • Appropriate communication

7. Immobilization • Voluntary motion • Lack of control • Immobilization devices work with this group • Involuntary motion • Fast exposure times with high mA helps • Possibly increasing kVp will help • 15% rule shorter exposure • Fast film/screen combinations

9. Beam Limiting Devices • Diaphragms • Cones • Collimators • Limit the amount of tissue the beam exposes • Also, limit the amount of scatter produced • Our exposure

10. Variable Collimator • 2 sets of lead shutters limit the divergence of the beam • Collimator and light field • +/- 2% of the SID • Positive beam limitation (PBL) • Automatic collimator, collimates to the field size put in the bucky tray

11. Filtration • Total filtration • Inherent plus added filtration • Inherent • Glass envelope • Oil • Window of the tube housing • 0.5 mm Al • Added • Aluminum added to meet requirements

12. Total Filtration • 2.5 mm Al > 70 kVp • 1.5 mm Al 50 – 70 kVp • 0.5 mm Al < 50 kVp • Mobiles/portables and Fluoro units are required to have at least 2.5 mm Al

13. Long wavelength photons Filter Short wavelength photons

14. Half Value Layer (HVL) • This is the amount of aluminum required to reduce the beam intensity to half its original value. • This is variable based on the selected kVp • As kVp is increased the penetrability of the beam increases • Therefore, the amount of Al necessary to halve the beam intensity will have to increase as well.

15. Protective Shielding • Gonadal shields • Gonads need to be shielded when they are within 5cm of the beam • Unless shielding will obscure anatomy • Required to have at least 0.5 mm Pb

16. Types of Gonadal Shields • Flat contact • Shadow • Shaped contact • Clear lead

17. Specific area shielding • Breast during scoliosis screening • Clear lead filter • PA instead of AP

18. Compensating filters • Trough or bilateral wedge • For chest images • Wedge filter • Specialized metal filters • Copper

20. Technical Factors • Technique charts • High kVp low mAs techniques • This is within a specific body part or region

21. Film Processing and QC • The processor has to work correctly. If not, films will be poor and repeats necessary. • QC insures that the processor is maintained to a standard level of acceptance

22. Film/Screen • Rare earth screens are generally faster • This occurs due to their higher atomic number which results in a higher absorption of photons. Consequently, more light is produced per photon meaning less photons have to be used for a good film.

23. Grids • Prevent scattered radiation from reaching the film. • They actually increase pt dose. • However, film quality is dramatically improved.

25. Repeat Analysis • Systematic review of repeated films to determine trends that can be eliminated thru education, procedural changes, or equipment maintenance.

26. Unnecessary Procedures • Make sure films are completed and recorded. • Listen to pts about possible previous exams. • When in doubt ask.

27. SID • Must be a minimum of 12 inches • The longer the SID the lower the pt dose

29. Digital Imaging • CR and DR are the two methods currently used for digital diagnostic imaging • Images are displayed on a computer for viewing • Analogous to digital pictures at home • Image quality can be manipulated post acquisition • Possible reduction in repeats

30. Fluoroscopy Procedures • High pt dose • Potentially high tech exposure • Exams provide dynamic info • ‘real time’ feedback for positioning of devices

31. Dose recording to patients • ESE • Entrance skin dose • GSD • Genetically significant dose • Bone marrow dose

32. Pregnant pts • Should not be radiographed • If necessary, informed consent should be obtained • Pts needed to be asked about potential pregnancy before the exam begins

33. Pediatrics • More radio-sensitive than adults • More likely to move • Need to get instructions they understand not fear • Gonadal shielding collimation

34. Protection of Personnel • MPD • ALARA

35. Dose Reduction Methods • No repeats • Patient is the source of scatter • Filtration • Protective apparel • Technical factors

36. Pregnant personnel • Lower MPD • Protective apparel • Additional monitoring • Work schedule alteration

37. Basic Principles of Protection • Time • Distance • Shielding

38. Structural Shielding • Primary • 7 feet high • 1/16 in Pb • Secondary • 1/32 in Pb • Operator booth • Photons should scatter at least twice before entering the booth area • Secondary barrier