CT Radiation Dose: Current status and future strategies. Donald P. Frush, MD

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1 CT Radiation Dose: Current status and future strategies Donald P. Frush, MD Division of Pediatric Radiology Department of Radiology Duke University Medical Center

2 I consider the radiologist s responsibility with (radiation) dose to be the same as any physician s with (medication) dose. Over (or under) dosing is a medical error.

3 Current Concerns Are CT doses high? Is this a problem? Strategies to control medical radiation

4 Current Concerns Are CT doses high? Is this a problem? Strategies to control medical radiation

5 Low-level Radiation < msv

6 Background Radiation msv per year

7 Measures of CT Dose Physical measurements e.g. anthropomorphic phantoms Monte Carlo DLP method Published estimations

8 Mettler, Huda, Yoshizumi, Mahesh. Radiology. 2008; 248;

9 Mettler, Huda, Yoshizumi, Mahesh. Radiology. 2008; 248;

10 Typical Medical Radiation Doses: 5 year-old (msv) 3-view ankle view chest.02 Tc-99m radionuclide gastric emptying.06 Tc-99m radionuclide cystogram.18 Tc-99m radionuclide bone scan 6.2 FDG PET 15.3 Fluoroscopic cystogram <.33 Chest CT up to 3 Abdomen CT up to 5 CXR Equivalents 1/14 th

11 Can Be High Dose: 64-slice MDCT ED (msv) SD (msv) Chest with modulation Chest w/o modulation Chest Extreme 42.95!!! 0.55 Abdomen with modulation Abdomen w/o modulation Abdomen Extreme 118.9!!! 1.85

12 How much do we understand about CT radiation dose?

13 Under estimation by 75% of MDs! Lee et al. Radiology. 2004; 231:

14 Current Concerns Are CT doses high? Is this a problem? Strategies to control medical radiation

15 CT: Patterns of Use million examinations in U.S. U.S. : 25-60% of world total Up to 11% of CT exams are pediatric 4-7 million pediatric CTs 17% of these in children 0-5 years old

16 Multidetector CT: U.S. 65,000,000 examinations per year If 50% involve two phases. 97,500,000 dose events per year 2002 US population: 281,000,000 1 CT for every 3.5 people Conservative: 1 CT for 9.6 people

17 Mettler et al Health Physics. In press Oct 2008

18 Pediatric Procedure Volumes Computed Tomography Magnetic Resonance 600, , , ,000 37% CAGR 200, ,000 30% CAGR 300, , , ,000 50, Source: AMR, As referred by Pediatrician Source: AMR, As referred by Pediatrician Positron Emission Tomography Conventional X-Ray 3,000 2,500 2,000 38% CAGR 250, , ,000 5% CAGR 1,500 1, , , Source: AMR, As referred by Pediatrician Source: AMR, As referred by Pediatrician Privileged & Confidential GE Healthcare, David Dobson 18

19 Scope of CT Radiation All Medical X-Ray X Imaging Modalities CT: 5% frequency of use but contributes 40%-67% of medical radiation Head 6% GI Tract 5% Abdomen 5% CT 5% Angio/ Interventional 1% Other 8% Skeleton 29% UNSCEAR 2000 Report to the General Assembly, Annex D: Medical Radiation Exposures. Mettler et al J Radiol Prot. 2000; 20: Chest 41%

20 (old) Estimated Annual Radiation Exposure 15% 81.2% Background Medical Kimball s Biology; NCRP Consummer Products Other

21 Mettler et al Health Physics. In press Oct 2008

22 Why?

23 Driving CT Use We drive use Industry drives use Non-radiologists drive use Media drives use Public drives use

26 Isn t it easier just to get a CT?

27 ED Imaging

28 Increased Pediatric CT in the Emergency Department Broder et al. Emerg Radiol 2007; 14:227-32

29 But I thought that the ED was different than the clinic. and we should order more [CTs] resident, June 4 th, 2008

30 Screening

31 Dr. Oz

32 There are Two Types of Bio Effects Dose dependent: severity depends on dose there is a threshold burns, hair loss This is a deterministic effect

34 There are Two Types of Bio Effects Non dose dependent: severity is independent of dose risk of event occurring is dependent on dose there is no threshold cancer, genetic mutations This is a stochastic effect

36 Is it safe?

37 Low-Level Level Radiation Risk: Four Perspectives We don t know Data indicate low-level harmful Data indicate low-level not harmful Data indicate low-level helpful Concept of hormesis

38 100 msv exposure 1:100 cancer incidence Background 43:100

40 Pediatric Fatal Cancer Risk Estimated Debated May be zero May be 1 in ,000 risk from single CT

41 Health care cost Reimbursement Lee CI, Foreman HP. The hidden costs of CT bioeffects. (2007) JACR 5:78-79

43 Radiation Risks in Children: No Debate Tissues are more radiosensitive Longer lifetime to manifest radiationinduced injury (cancer, cataracts) Each exam (dose) is cumulative Same settings: higher dose for children

44 Adhere to ALARA principle

45 Current Concerns Are CT doses high? Is this a problem? Strategies to control medical radiation

46 Radiation Dose Reduction Strategies for CT Judicious use of CT - avoid unnecessary exams - consider alternate modalities - focus exams: limit coverage Adjust scan techniques

47 Judicious use of CT: this is extremely complicated

48 Radiation Dose Reduction Strategies for CT Judicious use of CT Adjust scan parameters - scan indication - scan region/organ system - adjust individual parameters - simplify scanning

49 Radiation Dose Reduction Strategies for CT Judicious use of CT Adjust scan parameters - scan indication - scan region/organ system - adjust individual parameters - simplify scanning

50 Radiation Dose Reduction Strategies for CT Judicious use of CT Adjust scan parameters - scan indication - scan region/organ system - adjust individual parameters - simplify scanning

51 Radiation Control: Adjustable CT Parameters Tube Current (ma) Gantry cycle time ( seconds) Kilovoltage (kvp) Pitch

52 15 mas

53 8mAs

54 340 ma 40 ma

58 AJR January 2008: 190

59 Paulson, et al. AJR 2008; 190:

62 3D Nodule Simulation Real Simulated

63 Simulated Sarcoma Metastases

64 Results: area under ROC --- preliminary analysis

65 Radiation Dose Reduction Strategies for CT Judicious use of CT Adjust scan parameters - scan indication - scan region/organ system - adjust individual parameters - simplify scanning

66 Color Coding for KIDS Weight-Based Pediatric Protocols Selecting a Pediatric Anatomical Region brings up color selector

67 Tube Current Modulation (ATCM) Angular (x, y) Z-axis Kalra et al. Radiology 2004; 233:

70 How Are We Doing?

72 SPR Survey 2001 vs 2006: chest kvp abdomen

73 SPR Survey 2001 vs 2006: chest ma abdomen

74 Guidelines for Pediatric CT

75 Take Home Points Imaging is helpful Radiation is necessary Wise to consider any radiation a risk There are many ways to be safe Radiologists are consultants

The Challenge of CT Dose Records

The Challenge of CT Dose Records Kimberly Applegate, MD, MS, FACR Professor of Radiology and Pediatrics Emory University *financial disclosures: -Springer Textbook contracts -AIM advisory board for patient