Radiation- the facts Maybritt Kuypers, SEH-arts KNMG

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Radiation- the facts Maybritt Kuypers, SEH-arts KNMG

  1. 1. ACEP-RECAP 19 November 2008 Westfriesgasthuis
  2. 2. Linda A. Regan, MD,FACEP, Assistant Professor, Emergency Medicine, Johns Hopkins Medical Institutions “How Much IsToo Much? The REAL Risk of X –rays and CTs”
  3. 3.  Total radiation dosages of imaging studies ranging from plain radiography to CT scanning and risks  Ways to avoid certain high RAD imaging studies
  4. 4.  The rates of CT usage have dramatically increased over the past 25 years[ 1,2]  In 1980, there were 3.6 millionCT’s per year  In 1998, there were 33 million CT’s per year  In 2006, there were 62 million CT’s per year with 7 million in children < age of 15 years
  5. 5.  In 2000, data was published on CT usage at the University of New Mexico. [3]  33,713 consecutive CT exams  11% under 15 years  Peak group 36-50  55% males  99% Head CT without contrast  75% Chest with contrast  93% Abdomen with contrast (33% had prior)  30% had at least 3 scans; 7% had greater than 5 scans and 4% had more than 9 scans
  6. 6.  Radiation Exposure (Roentgens) Describes the amount of radiation in the air  Radiation Dose (Rads or MilliGrays or mGy) Amount of energy adsorbed per unit mass of tissue  Equivalent Dose (REM or MilliSieverts or mSv) Modifies Radiation Dose by biologic effects. This is because all types of radiation are not equal  Effective Dose (MilliSieverts/mSv) Accounts for where dose is adsorbed as all tissues are not equally sensitive to radiation. (The effective dose is averaged for age and sex )
  7. 7.  Note:When comparing data, most authors agree that for CT radiation: 1mSv = 1mGy 1mSv = 0.1 REM  Background Radiation ≈ 1-3 mSv per year  Where do we get our radiation exposure?  80-85% of radiation exposure  15-20% from medical imaging
  8. 8. TYPE OF STUDY (EFFECTIVE DOSE)  CXR (PA only) 0.02 mSv  CXR (PA and lat) 0.1 mSv  AbdXR 0.7 mSv  Cervical Spine 0.2 mSv  Thoracic Spine 1.0 mSv  Lumbar Spine 1.5 mSv TYPE OF STUDY (EFFECTIVE DOSE)  Head CT 2 mSv  Neck CT 3 mSv  Chest CT 7 mSv  Chest CT for PE 15 mSv  Abd CT 7.5 mSv  Pelvis CT 7.5 mSv Transatlantische vlucht Amsterdam - NewYork - Amsterdam = ongeveer 0,05 mSv.
  9. 9. WHAT ISTHE BASELINE CANCER RISK?  It is based on baseline population data  Lifetime Attributable Risk (LAR)  The LAR or the Incidence of cancer in the population is 42%  The Lifetime cancer mortality is 20%  When we talk about the LAR of radiation-induced cancers, we are talking about the percentage increase above the baseline risk. . WHAT ISTHE RISK BASED ON MSV?  Radiation induced cancer For a 10 mSv exposure, there is postulated risk of 1 additional cancer per 1,000 patients with an average of 50% mortality  Data from Atomic Bomb survivors [6]:  Strong data increased risk over 100 mSv  Good data increased risk 50-100 mSv  Reasonable data increased risk 10-50 mSv
  10. 10.  There is potentially NO threshold below which there is NO risk.  However, most authors agree that >100mSv appreciable increase in relative risk
  11. 11.  7 year period with 1.9% of patients having 3 or more visits (each with CT!)  130 patients underwent 1,744 CT's (55% ED)  Mean number of ED CT was 7.4 (max 41)  Mean cumulative dose: 64.7 mSv (max 330mSv)
  12. 12.  Lifetime cancer mortality risk is higher for children than for adults  LAR of cancer for a 10 year old at time of exposure Up to 50 mSv: 0‐2% increase over baseline 50‐500 mSv: 2‐17% increase over baseline  1 CT at age 1  Abdominal CT: LAR of dying from radiation induced cancer is 1 in 550  Head: LAR of dying from radiation induced cancer is 1 in 1500
  13. 13.  if 600,000 abdominal and headCT’s are performed per year, and we know that head CT’s are ordered at a rate of 2:1 compared to abdominal CT’s. . .  ≈ 600 children will die from cancer  Given a background rate of 140,000 children per year dying of cancer, this may seem like a small rate.The increase is “only” 0.43%
  14. 14. Pediatric study 2000 2006 % increase Head 443 544 23% Chest 17 91 435% Abd 148 220 49% Cspine 38 177 366%
  15. 15. Adult study 2000 2005 %increase Head 3504 5289 51% Chest 490 1596 226% Abd 1845 3179 72% C-spine 260 1464 463%
  16. 16.  Major increase in the 13‐17 year olds where the numbers almost mirror adults  This is concerning! physicians treat adolescents as adults by using the same imaging ordering patterns
  17. 17. HEAD CT  Neonate ≈ 0.075%  5 yo ≈ 0.04%  15 yo ≈ 0.013%  25 yo ≈ 0.008%  50 yo ≈ 0.006% ABD CT  Neonate ≈ 0.14%  5 yo ≈ 0.09%  15 yo ≈ 0.07%  25 yo ≈ 0.05%  35 yo ≈ 0.02%
  18. 18.  Even though doses for head CT are higher due to the larger doses needed to penetrate the bone, the risks are higher for abdominal CT  This is due to the radiosensitivity of the abdominal organs.This increased risk continues to be noted until around the age of 40  This is one of the main reasons to be concerned about the increased use of CT scans in the younger population
  19. 19.  Any conerns??  Spontneous abortion, birth defects, cancer?  Who is more at risk, mom or unborn child?
  20. 20. Before 2 weeks: Fetal doses of > 100 mSv place the pregnancy at risk for spontaneous miscarriage However, if implantation is maintained, there is no risk of loss related to this exposure and teratogenic effects are typically not seen Teratogenic effects  Between 2‐20 weeks teratogenic effects can be seen at doses greater than 50‐150 mSv.  These can include growth retardation, mental delay and retardation, as well as physical deformities.  At < 2 and > 20 weeks, the risk of teratogenic effects is very unlikely, except in very high exposure doses
  21. 21. Always a risk…  Baseline risk of fatal childhood cancer is 1 in 2,000  At a fetal dose of 50 mSv, a Relative Risk of 2 this increases the risk of developing a fatal childhood cancer to 2 in 2,000.  This risk may be higher in the first trimester (RR of 3) and lower in subsequent trimesters (RR 2)
  22. 22.  CT or ventilation- perfusion scan?
  23. 23. Type of study Fetal radiation dose in mSv or mGy Abd X-ray 2-3 Lumbar spineAP/LAT 2 Abd CT 1-2 Pelvis CT 10-50 Chest CT for PE 0.06 Ventilation 0.02 Perfusion 0.22 !!
  24. 24. Radiology Staff/Department Dependent  Tube current modulations  Tube current  Rotation time (detector row dependent)  Tube rotation time is decreased with faster rotations, which occur with higher detector row numbers.This decreases the dose delivered  Higher detector row scanners are capable of thinner slices, the tube current is often increased to maintain similar noise level and preserve the image quality.
  25. 25. Individual Dependent  Shielding (breast, thyroid, eye, gonads)  Overlap of images  Weight based tube current changes (under 70kg)  Studies show that there is good quality under 80 kg at 50% reduced tube current.
  26. 26.  Do we really need that many CTs?  USA vs. NL  Child vs Unborn vs Adult  Morbidty&mortality prevented by use of CT/X ray vs.  Morbidity&mortality caused by CT/X ray  Remember you are not the only one making X- rays and CTs…
  27. 27. 1. Nickoloff, E.L. & P.O. Alderson. (2001). Radiation exposures to patients from CT: reality, public perception, and policy.AJR.American Journal of Roentgenology 177, 285-287. 2. Sodickson,A., P.F. Baeyens, K.P. Andriole, L.M. Prevedello, R.D. Nawfel, R. Hanson & R. Khorasani. (2009). Recurrent CT, cumulative radiation exposure, and associated radiation-induced cancer risks from CT of adults. Radiology 251, 175-184. 3. Mettler, F.A.,Jr, P.W.Wiest, J.A. Locken & C.A. Kelsey. (2000). CT scanning: patterns of use and dose. Journal of Radiological Protection : Official Journal of the Society for Radiological Protection 20, 353-359. 4. Hui, C.M., J.H. MacGregor, H.C.Tien & J.B. Kortbeek. (2009). Radiation dose From initial trauma assessment and resuscitation: review of the literature. Canadian Journal of Surgery.Journal Canadien De Chirurgie 52, 147-152. 5. Mettler, F.A.,Jr,W. Huda,T.T.Yoshizumi & M. Mahesh. (2008). Effective doses in radiology and diagnostic nuclear medicine: a catalog. Radiology 248, 254-263. 6. Brenner, D., C. Elliston, E. Hall &W. Berdon. (2001). Estimated risks of radiation-induced fatal cancer from pediatric CT. AJR.American Journal of Roentgenology 176, 289-296.
  28. 28. 7. Griffey, R.T. & A. Sodickson. (2009). Cumulative radiation exposure and cancer risk estimates in emergency department patients undergoing repeat or multiple CT. AJR.American Journal of Roentgenology 192, 887-892. 8. Online resource: http://www.bt.cdc.gov/radiation/prenatalphysician.asp 9. Broder, J., L.A. Fordham & D.M. Warshauer. (2007). Increasing utilization of computed tomography in the pediatric emergency department, 2000-2006. Emergency Radiology 14, 227-232. 10. Broder, J. & D.M.Warshauer. (2006). Increasing utilization of computed Tomography in the adult emergency department, 2000-2005. Emergency Radiology 13, 25-30. 2007). Computed tomography--an increasing source of radiation exposure.The New England Journal of Medicine 357, 2277-2284. 12. Chen, M.M., F.V. Coakley, A. Kaimal & R.K. Laros Jr. (2008). Guidelines for computed tomography and magnetic resonance imaging use during pregnancy and lactation. Obstetrics and Gynecology 112, 333-340. 13. Online resource: http://brighamrad.harvard.edu/education/fetaldose/fetaldose.pdf 28. Kalra, M.K., M.M. Maher,T.L.Toth, L.M. Hamberg, M.A. Blake, J.A. Shepard & S. Saini. (2004). Strategies for CT radiation dose optimization. Radiology 230, 619-628.
  29. 29.  Cosmic radiation in commercial aviation Travel Medicine and Infectious Disease, Volume 6, Issue 3, May 2008, Pages 125-127 Michael Bagshaw “International Commission on Radiological Protection recommends maximum mean body effective dose limits of 20 mSv/yr (averaged over 5 years, with a maximum in any 1 year of 50 mSv). Radiation doses can be measured during flight or may be calculated using a computer-modelling program such as CARI, EPCARD, SIEVERT or PCAIRE. Mean ambient equivalent dose rates are consistently reported in the region of 4–5 μSv/h for long-haul pilots and 1–3 μSv/h for short- haul, giving an annual mean effective exposure of the order 2–3 mSv for long- haul and 1–2 mSv for short-haul pilots. Epidemiological studies of flight crew have not shown conclusive evidence for any increase in cancer mortality or cancer incidence directly attributable to ionising radiation exposure.Whilst there is no level of radiation exposure below which effects do not occur, current evidence indicates that the probability of airline crew or passengers suffering adverse health effects as a result of exposure to cosmic radiation is very low.”
  30. 30.  Some cosmic radiation dose measurements aboard flights connecting Zagreb Airport Applied Radiation and Isotopes, Volume 66, Issue 2, February 2008, Pages 247-251 B.Vuković,V. Radolić, I. Lisjak, B.Vekić, M. Poje, J. Planinić  The estimated occupational effective dose for the aircraft crew (A320) working 500 h per year was 1.64 mSv.  Another experiment was performed by the flights Zagreb–Paris– Buenos Aires and reversely, when one measured cosmic radiation dose; for 26.7 h of flight, theTLD dosimeter registered the total dose of 75 μSv and the average dose rate was 2.7 μSv/h. In the same month, February 2005, a traveling to Japan (24 h flight: Zagreb–Frankfurt–Tokyo and reversely) and theTLD-100 measurement showed the average dose rate of 2.4 μSv/h
  31. 31.  www.nrg.eu  Straling die direct of indirect van bronnen buiten de aarde afkomstig is. De kosmische straling maakt deel uit van de natuurlijke achtergrondstraling. Het stralingsniveau van de kosmische straling afhankelijk van de hoogte boven het zeeniveau. Op zeeniveau bedraagt het dosisequivalenttempo 0,3 mSv/a, op 3000 m hoogte ongeveer 1,2 mSv/a. Bij vliegreizen veroorzaakt de kosmische straling een extra dosisequivalent:  op een transatlantische vlucht Amsterdam - New York - Amsterdam ongeveer 0,05 mSv.

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