Lecture 1

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  • Neils Ryberg Finsen 1893 On the influence of light on the skin showed UV caused sunburn and not radient heat. (1903 Nobel Prize for UV treatment of lupus vulgaris)
  • LD(50/30) kill 50% in 30 days
  • Remainder: e.g. adrenals, brain, upper L intestine, small intestine, kidneys, muscle, pancreas, spleen, thymus, and uterus
  • LD(50/30) kill 50% in 30 days
  • DAP - barium enema 7-80 Gy.cm 2 UK annual collective dose for for chest X-rays - 166 manSv for cadiovascular interventional radiology = 904 manSv (4.7%) angiocardiology 1076 manSv
  • Lecture 1

    1. 1. Radiation Protection for Cardiologists John Saunderson Radiation Protection Adviser PRH ext 6690
    2. 2. Plan <ul><li>3 afternoons of lectures (30/1/04, 13/2/04, 26/3/04) </li></ul><ul><li>1 afternoon in Cath Lab with phantoms and dosemeters (2/4/04) </li></ul>
    3. 3. Radiation Protection? <ul><li>The law – IRMER – “adequate training” </li></ul><ul><li>Higher Medical Training Curriculum for Cardiology – April 2003 </li></ul><ul><li>Angiography = 0.8% of X-ray procedures, but 10% of X-ray dose </li></ul><ul><li>Radiation can be dangerous </li></ul>Why bother?
    4. 5. 700 CANCER CASES CAUSED BY X-RAYS X -RAYS used in everyday detection of diseases and broken bones are responsible for about 700 cases of cancer a year, according to the most detailed study to date.   The research showed that 0.6 per cent of the 124,000 patients found to have cancer each year can attribute the disease to X-ray exposure. Diagnostic X-rays, which are used in conventional radiography and imaging techniques such as CT scans, are the largest man-made source of radiation exposure to the general population. Although such X-rays provide great benefits, it is generally accepted that their use is associated with very small increases in cancer risk.   30 January 2004
    5. 6. Syllabus <ul><li>Physics & hazards of ionising radiation to patients & staff </li></ul><ul><li>Statutory requirements for Medical Exposures </li></ul><ul><li>Equipment </li></ul><ul><li>Factors affecting patient & staff dose </li></ul><ul><li>Important aspects of cardioradiology </li></ul><ul><li>Above covers IRMER “Core of Knowledge” . </li></ul>
    6. 7. www.hullrad.org.uk
    7. 8. Radiation Hazards
    8. 9. Wilhelm Roentgen <ul><li>Discovered X-rays on 8th November 1895 </li></ul>
    9. 10. Henri Becquerel <ul><li>Discovered radioactivity on 26 February 1896 </li></ul>
    10. 11. Frau Roentgen’s hand, 1895 Colles’ fracture 1896
    11. 12. Dr Rome Wagner and assistant
    12. 13. ” First radiograph of the human brain” 1896 In reality a pan of cat intestines photographed by H.A. Falk (1896)
    13. 14. First Reports of Injury <ul><li>Late 1896 </li></ul><ul><li>Elihu Thomson - burn from deliberate exposure of finger </li></ul>Edison’s assistant - hair fell out & scalp became inflamed & ulcerated
    14. 16. Mihran Kassabian (1870-1910)
    15. 17. Sister Blandina (1871 - 1916) <ul><li>1898, started work as radiographer in Cologne </li></ul><ul><li>held nervous patients & children with unprotected hands </li></ul><ul><li>controlled the degree of hardness of the X-ray tube by placing her hand behind of the screen. </li></ul>
    16. 18. Sister Blandina <ul><li>After 6 months strong flushing & swellings of hands </li></ul><ul><li>diagnosed with an X-ray cancer, </li></ul><ul><li>some fingers amputated </li></ul><ul><li>then whole hand amputated </li></ul><ul><li>whole arm amputated. </li></ul>
    17. 19. Sister Blandina <ul><li>1915 severed difficulties of breathing </li></ul><ul><li>extensive shadow on the left side of her thorax </li></ul><ul><li>large wound on her whole front- and back-side </li></ul><ul><li>Died on 22 nd October 1916. </li></ul>
    18. 20. First Radiotherapy Treatment Emil Herman Grubbé <ul><li>29 January 1896 </li></ul><ul><li>woman (50) with breast cancer </li></ul><ul><li>18 daily 1-hour irradiation </li></ul><ul><li>condition was relieved </li></ul><ul><li>died shortly afterwards from metastases. </li></ul>
    19. 21. Radiotherapy 1899 Basal Cell Carcinoma A) Before B) 30 years on
    20. 22. William Rollins <ul><li>Rollins W. X-light kills . Boston Med Surg J 1901;144:173. </li></ul><ul><li>Codman EA. No practical danger from the x-ray . Boston Med Surg J 1901;144:197 </li></ul>
    21. 23. Early Protective Suit <ul><li>Lead glasses </li></ul><ul><li>Filters </li></ul><ul><li>Tube shielding </li></ul><ul><li>Early personal “dosemeters” </li></ul><ul><li>etc. </li></ul>
    22. 24. Protection Progress <ul><li>1898 Roentgen Society Committee of Inquiry </li></ul><ul><li>1915 Roentgen Society publishes recommendations </li></ul><ul><li>1921 British X-Ray and Radiation Protection Committee established and reported </li></ul><ul><li>1928 2nd International Congress of Radiology adopts British recommendations + the Roentgen </li></ul><ul><li>1931 USACXRP publishes first recommendations (0.2 r/d) </li></ul><ul><li>1934 4th ICR adopts 0.2 Roentgens per day limit </li></ul>
    23. 27. Life Span Study <ul><li>About 94,000 persons, </li></ul><ul><li>> 50% still alive in 1995 </li></ul><ul><li>By 1991 about 8,000 cancer deaths </li></ul><ul><li> 430 of these attributable to radiation </li></ul><ul><li>21 out of 800 in utero with dose > 10 mSv severely mentally retarded individuals have been identified </li></ul><ul><li>No increase in hereditary disease </li></ul><ul><li>http://www.rerf.or.jp/eigo/glossary/lsspopul.htm </li></ul>
    24. 28. Mechanisms of Radiation Injury <ul><li>LD(50/30) = 4 Gy </li></ul><ul><ul><li>280 J to 70 kg man </li></ul></ul><ul><ul><li>1 milli-Celsius rise in body temp. </li></ul></ul><ul><ul><li>drinking 6 ml of warm tea </li></ul></ul>i.e. not caused by heating, but ionisation .
    25. 30. Radiation Quantities and Units <ul><li>Absorbed dose </li></ul><ul><li>Equivalent dose </li></ul><ul><li>Effective dose </li></ul><ul><li>others . </li></ul>
    26. 31. Absorbed Dose (D) <ul><li>Amount of energy absorbed per unit mass [D=d  /dm] </li></ul><ul><li>1 Gray (Gy) = 1 J/kg </li></ul><ul><li>Specific to the matierial, e.g. </li></ul><ul><ul><li>absorbed dose to water </li></ul></ul><ul><ul><li>absorbed dose to air </li></ul></ul><ul><ul><li>absorbed dose to bone . </li></ul></ul>
    27. 32. Typical Values of D <ul><li>Radiotherapy dose = 40 Gy to tumour (over several weeks) </li></ul><ul><li>LD(50/30) = 4 Gy to whole body (single dose) </li></ul><ul><li>Typical 1 minute screening = 20 mGy skin dose </li></ul><ul><li>Chest PA = 160 uGy skin dose </li></ul><ul><li>Threshold for transient erythema = 2 Gy . </li></ul>
    28. 33. Equivalent Dose (H T,R ) <ul><li>Absorbed dose to tissue x radiation weighting factor [H T,R = w R .D T,R ] </li></ul><ul><li>Units are Sieverts (Sv) </li></ul><ul><ul><li>All photons, electrons and muons, w R = 1 </li></ul></ul><ul><ul><li>Neutrons, w R = 5-20 (depending on energy) </li></ul></ul><ul><ul><li>Protons, w R = 5 </li></ul></ul><ul><ul><li>Alpha particles, w R = 20 </li></ul></ul><ul><li>For X-rays and gamma rays, 1 Gy = 1 Sv </li></ul><ul><li>For beta particles and positrons, 1 Gy = 1 Sv </li></ul><ul><li>For alphas, 1 Gy = 20 Sv . </li></ul>
    29. 34. Effective Dose (E) <ul><li>Sum of equivalent doses to each tissue/organ x organ weighting factors [E =  T w T .H T ] </li></ul><ul><li>Units are Sieverts (Sv) </li></ul>Tissue or organ w T Gonads 0.20 Red bone marrow 0.12 Colon 0.12 Lung 0.12 Stomach 0.12 Bladder 0.05 Breast 0.05 Liver 0.05 Oesphagus 0.05 Thyroid 0.05 Skin 0.01 Bone surfaces 0.01 Remainder 0.05 e.g. if gonads alone received 2 Gy to tissue, E = 0.20 x 2 = 0.4 Sv .
    30. 35. Typical Values of E <ul><li>Pulmonary angiography = 5.4 mSv </li></ul><ul><li>CT abdomen = 10 mSv </li></ul><ul><li>Conventional abdomen X-ray = 1 mSv </li></ul><ul><li>Chest PA = 20 uSv </li></ul><ul><li>Annual dose limit for radiation workers = 20 mSv </li></ul><ul><li>Annual background dose = 2.5 mSv </li></ul><ul><li>(risk of inducing cancer or hereditary disease is proportional to Effective Dose) . </li></ul>
    31. 36. Others <ul><li>Dose area product (Gy.cm 2 ) - dose x field size </li></ul><ul><li>Collective dose (manSv) - effective dose x number of people exposed (e.g.Angiography gave 1,923 manSv in UK in 2000) </li></ul><ul><li>Exposure (R or C/kg) - charge produced in 1 kg of air </li></ul><ul><li>Air kerma (Gy) - energy released in 1 kg of air (dose meters usually read in air kerma) </li></ul><ul><li>Dose equivalent (Sv) - superseded by equivalent dose </li></ul><ul><li>Effective dose equivalent (Sv) - superseded by effective dose </li></ul><ul><li>Ambient dose equivalent (Sv) - dose a particular depth (often used for personal dosimeter results) </li></ul><ul><li>CTDI (mGy), DLP (mGy.cm) </li></ul><ul><li>Committed effective dose (Sv) – from ingested radionuclides over 50 y . </li></ul>
    32. 37. Old Units <ul><li>100 rad = 1 Gy = 100cGy </li></ul><ul><li>100 rem = 1 Sv </li></ul><ul><li>100 R  0.9 Gy </li></ul>Main Units for Cardiology <ul><li>Effective dose in mSv </li></ul><ul><li>Skin dose in mGy or mSv </li></ul><ul><li>DAP in Gy.cm 2 </li></ul>
    33. 38. Two Types of Effect <ul><li>Deterministic effects (“threshold effects”) </li></ul><ul><li>Stochastic effect (“chance effects”) . </li></ul>
    34. 39. Deterministic Effects <ul><li>Caused by significant cell necrosis </li></ul><ul><li>Not seen below a threshold dose </li></ul><ul><li>Above the threshold, the bigger the dose, the worse the effect </li></ul><ul><li>Do not accumulate over long term . </li></ul>
    35. 41. From FDA, Sept 1994, “Avoidance of serious x-ray induced skin injuries to patients during fluoroscopically-guided procedures”
    36. 42. Example of Radiation Injury in Cardiology <ul><li>40 year old male </li></ul><ul><li>coronary angiography </li></ul><ul><li>coronary angioplasty </li></ul><ul><li>second angiography procedure due to complications </li></ul><ul><li>coronary artery by-pass graft </li></ul><ul><li>all on 29 March 1990 . </li></ul>
    37. 43. Fig. A 6-8 weeks after multiple coronary angiography and angioplasty procedures
    38. 44. Fig. B 16 to 21 weeks after procedure, with small ulcerated area present
    39. 45. Fig. C 18-21 months after procedure, evidencing tissue necrosis
    40. 46. Fig. D Close up of lession in Fig. C From injury, dose probably in excess of 20 Gy .
    41. 47. Fig. E Appearance after skin grafting procedure .
    42. 48. 75-year-old woman with 90% stenosis of right coronary artery. Photograph of right lateral chest obtained 10 months after percutaneous transluminal coronary angioplasty shows area of hyper- and hypopigmentation, skin atrophy, and telangiectasia (poikiloderma)
    43. 49. 56-year-old man with obstructing lesion of right coronary artery. Photograph of right posterolateral chest wall at 10 weeks after percutaneous transluminal coronary angioplasty shows 12 x 6.5 cm hyperpigmented plaque with hyperkeratosis below right axilla
    44. 50. 49-year-old woman with 8-year history of refractory supraventricular tachycardia. Photographs show sharply demarcated erythema above right elbow at 3 weeks after radiofrequency cardiac catheter ablation
    45. 51. 48-year-old woman with history of diabetes mellitus and severe coronary artery disease who underwent two percutaneous transluminal coronary angioplasties and stent placements within a month. Photograph of left mid back 2 months after last procedure shows well-marginated focal erythema and desquamation
    46. 52. 69-year-old man with history of angina who underwent two angioplasties of left coronary artery within 30 hr. Photograph taken 1-2 months after last procedure shows secondary ulceration over left scapula
    47. 53. To prevent deterministic effects <ul><li>Keep skin dose below 2 Gy </li></ul><ul><li>Keep eye dose below 500 mGy . </li></ul>
    48. 54. Stochastic Effects <ul><li>Caused by cell mutation leading to cancer or hereditary disease </li></ul><ul><li>Current theory says, no threshold </li></ul><ul><li>The bigger the dose, the more likely effect </li></ul><ul><ul><ul><li>So how big is the risk? . </li></ul></ul></ul>
    49. 56. Cancer deaths between 1950 and 1990 among Life Span Study survivors with significant exposure (i.e. > 5 mSv or within 2.5 km of the hypercentre)
    50. 57. Fraction of cancers induced by radiation
    51. 58. Fraction of cancers induced by radiation  Risk of inducing fatal cancer = 5 x 10 -2 Sv -1
    52. 59. Data Sources for Risk Estimates <ul><li>North American patients - breast, thyroid, skin </li></ul><ul><li>German patients with Ra-224 - bone </li></ul><ul><li>Euro. Patients with Thorotrast - liver </li></ul><ul><li>Oxford study - in utero induced cancer </li></ul><ul><li>Atomic bomb survivors - leukaemia, lung, colon, stomach, remainder . </li></ul>
    53. 60. ICRP risk factors 5.0 x 10 -5 per mSv  1 in 20,000 chance .
    54. 61. Pregnancy - Radiation Risks
    55. 63. For diagnostic procedures <ul><li>Doses unlikely to be high enough to cause fetal death or malformation </li></ul><ul><li>Increased risk of childhood cancer </li></ul><ul><li>Risks must be assessed for each individual case . </li></ul>
    56. 64. Doses in Cardiology Taken from “ Real-time quantification and display of skin radiation during coronary angiography and intervention ”, den Boer A, et al., Oct 2001 <ul><li>332 patients </li></ul><ul><li>25 - 99 Gy.cm 2 dose-area product </li></ul><ul><li>4 - 18 mGy effective dose </li></ul><ul><li>1:5000 - 1:1100 risk of inducing fatal cancer . </li></ul>
    57. 65. Dose Area Product <ul><li>Stochastic risks approx. proportional to DAP </li></ul><ul><li>Skin dose is DAP / area irradiated </li></ul><ul><li>1 Gy.cm 2  3 mGy skin dose </li></ul><ul><li>1 Gy.cm 2  0.2 mSv effective dose . </li></ul>
    58. 66. 20/11/96 2 Gy erythema threshold  666 Gy.cm 2 DAP (v. approx!!)
    59. 67. “ Small” risks so why worry? <ul><li>Average effective dose for angiography = 6 mSv </li></ul><ul><li>Risk of fatal cancer from 6 mSv only 1 in 3,300 </li></ul><ul><li>But, large number of patients </li></ul><ul><ul><li>321,174 angiography procedures in 2000 </li></ul></ul><ul><ul><li>Therefore, high probability that radiation from angiography will kill some patients </li></ul></ul><ul><li>So </li></ul><ul><ul><li>All exposures must be JUSTIFIED </li></ul></ul><ul><ul><li>Doses to patients, and staff, must be A s L ow A s R easonably A chievable ( ALARA principle ) . </li></ul></ul>
    60. 68. Still to do <ul><li>Production and interaction of X-rays </li></ul><ul><li>Image formation </li></ul><ul><li>Dose reduction – patients and staff </li></ul><ul><li>Legislation and guidelines </li></ul><ul><li>Equipment </li></ul>
    61. 69. fin

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