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Imaging Radiation Dose And The Use Of Bismuth Shielding In Scoliosis Imaging Carolyn Heyes Medical Imaging Department Royal Children’s Hospital Melbourne “Research indicates an increased risk of childhood acute lymphocytic leukaemia in plain film studies and an increased risk of fatal breast cancer from scoliosis series. The linear, no-threshold model, which states that no level of radiation exposure is without consequence, is currently the best estimate of risk. The younger the patient at the time of exposure, the greater the risk of developing a fatal cancer “ Radiology February 2005 U.S. National Cancer Institute Retrospective study 5,466 women with scoliosis Average of 24.7 x-rays prior to 1976 70% higher chance of developing breast cancer Radiation exposure is proportional to an increased cancer risk Full spine dose 1940 to 1959 6-200 times higher than today ALARA principle should always be followed Bismuth Heavy Metal Chemical Symbol Bi Atomic Number 83 Causes beam hardening and therefore decreases absorbed radiation dose Radiolucent Study Aims Multi-stage study commenced in April 2005 To identify the modality with the lowest recorded skin entry and exit doses To standardise the imaging performed Evaluate the effectiveness of bismuth shielding Breast Shields RCH current protocol does not use breast shields Copper shielding used in chiropractic spine imagining Bismuth more flexible and user friendly No research available on bismuth use in general imaging Commercially available bismuth shields Method Method 85 kg Alderson Rando Anthropomorphic phantom Tape placed at Thyroid, Breast and Symphysis 2.4m FFD PTW Diados Dosometer used Philips MD Eleva Fluoroscopy room on High Pilot test showed no variation in exposures within each modality Philips general room with AGFA CR Full Leg/Full Spine cassette holder with a 1.5m FFD Philips Digital Diagnost DR room with a fixed Quality mode with a fixed 1.25m FFD Bismuth shielding reduced doses by: Method 5 exposures for each level z z z No shielding Lead shielding Bismuth shielding Shielding placed on posterior surface Phantom positioned PA erect 4ply sheet of bismuth 0.06mm lead equivalent Skin entrance dose Skin exit dose z Thyroid 40% z Thyroid 15% z Breast 50% z Breast 30% z Gonads 20% z Gonads 20% Skin Entry Dose - Bismuth Skin Exit Dose - Bismuth Skin Entry Dose 120 CR DR Fluoro 100 M i c r o g r a y 80 Skin Exit Dose M i c r o g r a y 60 40 20 20 CR 15 DR Fluoro 10 5 0 Thryoid 0 Thryoid Breast Gonads Breast Gonads Overall Dose - Bismuth Dose measurements 300 Total D ose CR Skin Entry DR Skin Entry Fluoro Skin Entry CR Skin Exit DR Skin Exit Fluoro Skin Exit 140 120 M i 100 c r 200 150 100 50 60 r a total skin entry total skin exit 80 o g 250 0 40 y 20 CR No Shielding CR Bismuth Shielding DR No Shielding DR Bismuth Shielding Fluoro No Shielding Fluoro Bismuth Shielding 0 Images from each room DR Fluoroscopy Limitations of Study Measurements were recorded for a small area only Image quality has not been measured accurately. The phantom is the equivalent of an 85kg adult. CR The Future References Orthopaedic surgeons happy with bismuth shielding Discussions with bismuth manufacturers Further work with equipment specialists to optimize image processing Further studies on the use of Bismuth shielding in general examinations Doody, Michele Morin, et al. (2005) Breast Cancer Mortality After Diagnostic Radiography: Findings From the U.S. Scoliosis Cohort Study Spine, Vol 25, No.16. Kusher, David C, et al. (1986) Radiation Dose reduction in the Evaluation of Scoliosis: An Application of Digital Radiography Radiology 161:175-181 Geijer, Hakan, et al. (2001) Digital Radiography of Scoliosis with a Scanning Method: Initial Evaluation Radiology 218:402-410 Fahr, Michael J, et al. (2003) Digital Radiography in the Diagnosis of Toddler’s Fracture Southern Medical Journal Vol96 No3 234-239 Fricke, Bradley L, et al (2002) In-Plane Bismuth Breast Shields for Pediatric CT: Effects on Radiation Dose and Image Quality Using Experimental and Clinical Data AJR 180 407-411 Rehani, Madan M, Berry, Manorma (2000) Radiation Doses in Computed Tomography BMJ 320 593-594 Hopper, Kenneth D et al. (2001) Radioprotection to the Eye During CT Scanning AJNR 22 1194-1198 Frush, Donald P et al. (2003) Computed Tomography and radiation Risks: What Pediatric health care providers Should Know Pediatrics Vol112 951-956 Ullrich, Peter F (2001) Understanding idiopathic scoliosis www.spine-health.com (Updated March 30, 2004) Mayo Clinic Scoliosis www.mayoclinic.com Blackman, Ronald, Smith, Jason Scoliosis Treatment www.scoliosisrx.com (updated October 5th 2005) Fenner, Louise (1984) Reducing Patient Exposure During Scoliosis Radiography Dept of health and Human Services (U.S.) publication The Scoliosis Association of Australia What is Scoliosis? www.scoliosis.org.au References Egan, Ingrid. (1992) Comparison of imaging techniques currently used for limb measurement. The Radiographer 39, 1 pp4-8. Horsfield D & Jones SN (1986) Assessment of inequality in length of the lower limb. Radiography (UK) v52,no605 pp223-227. Tostevin J.(1992) Leg Length Measurement - A Simple Rule. The Radiographer vol 39, no.1, pp.9-10. Willis, Charles E, Slovis, Thomas L. (2005) The ALARA concept in pediatric CR and DR: Dose reduction in pediatric radiographic exams-a white paper conference executive summary. Pediatric Radiology 2004 34 Suppl.3ppS162S164. ICRP web module Radiation and your patient: A guide for medical practitioners. Neitzel, U. (2004) Pediatric radiation dose management in digital radiography. MedicaMundi 48/3 pp12-18. Williams, Peter F. Orthopaedic Management. Blackwell Scientific Publications 1982 pp153-162. Tachdjian,Mihran O. Pediatric Orthopedics W. B. Saunders Company. Second edition 1990 pp27-59.