Integrated Management & Educational Consultancy

Transcription

1 Integrated Management & Educational Consultancy Services MANDEC Radiology Update Seminar for The Dental Team Dr. Richard DeCann & Mr. Tim Reynolds IMECS Radiography Consultants Tel:

2 Seminar Content I (Legislation) Background to the legislative framework IRR (1999) Radiation Safety in the Workplace IR(ME)R 2000 Patient care and safety

3 Seminar Content II (Clinical Practice) Nature and Effects of Radiation The Image Formation Process Film and digital systems Radiographic techniques and the use of film holders, orthopantomography Image evaluation and radiographic audit

4 UK Dose Distribution 14% Comparison between dose sources in the UK 86%

5 Man Made Dose Distribution 10% Medical dose compared with other man made sources 90%

6 Comparing Medical Doses 3% General medical dose compared with dental 97%

7 Radiological Examinations in the UK 70% 30% Number of general medical examinations compared with dental

8 Potential for Dose Saving 45% 10% 45% Up to 50% of the medical dose delivered in the UK is unnecessary

9 Workshop List the characteristics of x-rays e.g. travels in straight lines

10 Nature of Ionising Radiation Travels in straight lines at the speed of light Obeys the inverse square law Penetrates, excites and ionises matter Chemical and biological effect Photographic and fluoroscopic effect Unaffected by magnetic or electric fields

11 Electromagnetic Spectrum Energy low high radio waves micro waves visible light X & gamma rays cosmic rays

12 Workshop What units are used to measure radiation exposure and dose?

13 Units of Radiation Measurement Exposure = COULOMBS PER KILOGRAM Kinetic Energy Released per unit Mass (KERMA) Absorbed Dose = GRAY Joules per Kilogram Dose Equivalent = SIEVERT Gray x Q (x-rays=1, protons=10, alpha=20) Effective Dose = SIEVERT Biological Effect (dose equivalent x tissue sensitivity) msv = 1 / 1000 (10-3 ) usv = 1 / 1,000,000 (10-6 )

14 Radiobiology Random interactions causing direct and indirect tissue damage Critical body macromolecules: protein, DNA (damage with incomplete or misrepair) H 2 O affected because of large size and content Ionised water becomes chemically reactive and can affect DNA by indirect action Formation of free radicals: HO 2 (peroxyls) H 2 O 2 (peroxides)

15 Radiobiology The exposure of a cell to radiation may result in: The premature death of the cell Prevention or delay in cell division Changes in cell structure and/or functions which may be passed on to daughter cells

16 What is damaged? DNA Any of the cytoplasmic organelles I bet they say MITOCHONDRIA

17 What Type of Damage Can Occur? Stochastic Deterministic

18 Who it Effects Somatic Genetic

19 Variations with Age at Exposure Detriment vs Age at Exposure 0 to 5 years 5 to 10 years 10 to 20 years 20 to 30 years 30 to 40 years 40 to 50 years 50 to 60 years

20 Plain Radiography The Image Formation Process X-ray tube Electrical energy to 99% heat 1% x-rays object image Differential tissue absorption density contrast sharpness

21 X-ray tube designs

22 Developer Latent Image to Visible Image Exposure Separation of silver bromide crystal Weakness in crystal Developer enters exposed crystal through weakness Converts whole crystal to solid silver

23 Rinse Stops development Washes off developer

24 Fixer Makes image permanent Washes off unexposed crystals Hardens the emulsion Film has a range of different levels of silver Density, Contrast etc

25 Wash Washes out remaining chemistry Archival permanence

26 Digital Dental Radiography Direct Close Coupled Devices (wired systems) Indirect Photo phosphor plates

27 Direct Digital Dental Radiography Charge Coupled Devices (wired systems) Indirect Photo phosphor plates

28 Digital vs Conventional Intra-oral Radiography Against Detector/sensor bulk Sensor handling damage Limited sensor sizes Paralleling film holders Cross infection control Cost For No processing (COSHH) Image consistency Instant image Image manipulation Patient care & education Archiving Image transfer

29 Intra-oral techniques

30 Film Holders Preferred technique because Accurate image (no distortion) Less repeats due to error (dose reduction) More reproducible Able to use rectangular collimator to reduce dose

31 Orthopantomography vs Full mouth of PAs Advantages Disadvantages Full dentition and associated structures on single image Less invasive Lower dose Can patient keep still? Lower quality image Cost of equipment Quicker

32 Subjective quality rating and quality standards for radiographs Rating/Quality Basis 1. Excellent: No errors of exposure, positioning or processing. Not less than 70%. 2. Acceptable Some errors which do not detract from the diagnostic use. Not greater than 20%. 3. Unacceptable Errors which render the radiograph diagnostically unacceptable. Not greater than 10%.

33 Guidelines for Image Critiques Area: film position and orientation (axis, border, blip) Projection: beam centring and angulation Density: level of blackness Contrast: difference in density for a range of structures Sharpness: level of detail Artifacts: something on the film that shouldn t be there If any of the above are not correct what needs to be done?

34 Integrated Management & Educational Consultancy Services MANDEC Radiology Update Seminar for The Dental Team Dr. Richard DeCann & Mr. Tim Reynolds IMECS Radiography Consultants Tel:

35 Contacts Richard Tim