Dose-equivalent equivalent = absorbed

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UCSF General Surgery 2010 Radiation Risks of Diagnostic

, FACS University of California, San Francisco San Francisco

for (fill in blank) Persistent interest in screening whole

surveillance in trauma Comparative observations Estimated CT

Radiation (BEIR) reports Longitudinal studies of ~120,000

1 UCSF General Surgery 2010 Radiation Risks of Diagnostic Radiology in Trauma Robert A. Izenberg, M.D., FACS University of California, San Francisco San Francisco General Hospital Context Increasingly liberal use of CT scans for (fill in blank) Persistent interest in screening whole body scans (despite data) Expanded CT technology CT for surveillance in trauma Comparative observations Estimated CT scans performed annually Biological effects of Ionizing Radiation (BEIR) reports Longitudinal studies of ~120,000 survivors within 2.5 km of Hiroshima & Nagasaki blasts Data used to estimate risks for LET radiation Page 1

Trauma & ACS trends Whole body pan-scans used increasingly Serial CT scanning for TBI, solid organs Almost ubiquitous use of CT for the acute abdomen Use in FUO evaluation of many ICU pts.

2 Trauma & ACS trends Whole body pan-scans used increasingly Serial CT scanning for TBI, solid organs Almost ubiquitous use of CT for the acute abdomen Use in FUO evaluation of many ICU pts. Expanded use in blunt chest trauma (including more minor mechanisms) Thin cut reconstruction of axial spine Utilization Aucar et.al., Am J Surg. 2007: CT scan utilization (4 yr period) => increase of 2.68 scans/patient (to total of 6.88 s/p), increase of > 250%! Kim et.al., J Trauma 2004: Report of CT utilization in ICU patients: 70 plain film radiographs (mean), 7.8 CT scans (mean), 2.5 fluoroscopic studies (mean) What are the additional risks of LET radiation associated with the prolific use of imaging studies, if any, and should these be a consideration in imaging utilization? Radiation damage (risk) Mutagenesis genetic effects in children of radiation-exposed persons. Extremely low for LET radiation. Teratogenesis altered fetal development Carcinogenesis cummulative, most important & widespread risk Page 2

01 Gy, 100 Rads = 1 Gy 1 Rem = 0.01 Sv, 100 Rem = 1 Sv msv or mgy Rads or rems CXR equivalent dose Equivalent time-dose from natural background radiation Chest X-R 0.02 2 1 2.4 days Skull X-R 0.

3 Units of exposure Dose-equivalent equivalent = absorbed dose X quality factor. For LET radiation, QF = 1.0 Therefore for this discussion: dose equivalent = absorbed dose Units of exposure 1 Rad (absorbed dose) = 1 Rem (d-e) 1 Gray (Gy) (ad) = 1 Sievert (Sv) (d-e) 1 Rad = 0.01 Gy, 100 Rads = 1 Gy 1 Rem = 0.01 Sv, 100 Rem = 1 Sv msv or mgy Rads or rems CXR equivalent dose Equivalent time-dose from natural background radiation Chest X-R days Skull X-R days Lumbar spine days Upper GI series year BaE years CT head days CT abdomen years Arteriography IR procedures ,000 Hiroshima & Nagasaki survivors estimated to have received, at the lowest, a dose in the range of 5-20 msv! , years , years Basis for discussion Direct attribution of cancer to CT or other imaging does not exist Guidelines & assumptions based on extrapolation from past observations BEIR VII report (Nat. Acad. Sci): Risk of cancer proceeds in linear fashion at lower doses, without a threshold. International Commission on Radiation: Risk of cancer will rise in direct proportion to absorbed doses, even in low dose range Page 3

Teratogenesis Maximum acceptable total dose during pregnancy = 5 rads (50mGy) to the uterus Growth retardation: 8-56 days post- conception Neurological effects: 2-15 weeks P.C.

4 Teratogenesis Maximum acceptable total dose during pregnancy = 5 rads (50mGy) to the uterus Growth retardation: 8-56 days post- conception Neurological effects: 2-15 weeks P.C. Childhood cancers: 1 st trimester 1-2 rads may increase incidence of leukemia from 3.6/10,000 to 5/10,000 Teratogenesis 1-2 rads may increase incidence from 3.6/10,000 to 5/10,000 Estimated doses: Unshielded CTabd: 3 rads Shielded CT upper abd: 1 rad Shielded CT head: ( 0.5 rads) Brenner & Elliston, Radiology 2004: Used estimated CA risks derived from LifeSpan study cohort (a-bomb survivors). Single full-body CT imaging => attributable CA mortality risk of 0.08% (at age 45). 30 x full body CT scans (to age 75) => attributable CA mortality risk of 1.9%. Page 4

Sifri et.al., J Trauma 2006: Studied the value of routine repeat CT head for patients with (+) scans but otherwise minimal injury.

5 J Trauma 2007: Dosimeter study of 172 trauma patients (mean ISS 23). Group received mean effective dose of 22.7 msv. Linear no- threshold model estimated an additional 190 cancer deaths in a population of 100,000 patients similarly radiated, including 4.4 additional thyroid cancers. Are all these scans necessary? Sifri et.al., J Trauma 2006: Studied the value of routine repeat CT head for patients with (+) scans but otherwise minimal injury. Patients with normal neurological exams derived no benefit from additional scanning & neuro exam had neg predictive value of 100%. Velmahos et.al., J Trauma 2006: Similar results. In the absence of clinical signs, no patient required change in management Risk mitigation Weigh benefits of imaging, particularly serial CT scans, in light of small of significant additional cummulative risk Alternatives to CT imaging: U/S, MRI Minimize pelvic imaging in pregnant patients and the very young. Limit number of cuts (including scout & delayed scans) Develop collaborative dose-reduction strategies with radiology Page 5

6 Summary Small but significant radiation risks occur with LET ionizing radiation, even at low doses. The potential for the un-modulated use of CT imaging to increase risk of radiation injury over time, is real The cummulative effect of multiple trauma imaging (in younger patients) coupled with more general increased utiliziation of CT may significant increase risks Mitigation strategies for CT utilization should be incorporated into overall trauma management protocols Radiation Risks of Diagnostic Radiology in Trauma Robert A. Izenberg, M.D., FACS University of California, San Francisco San Francisco General Hospital Page 6

Debra Pennington, MD Director of Imaging Dell Children s Medical Center

Debra Pennington, MD Director of Imaging Dell Children s Medical Center 1 Gray (Gy) is 1 J of radiation energy/ 1 kg matter (physical quantity absorbed dose) Diagnostic imaging doses in mgy (.001 Gy)