CT Radiation: What is the Radiation Risk to Your Patient? Pediatric Conference 5/19/2015 CT Radiation: What is the Radiation Risk to Your Patient? May 19, 2015 Megan Marine, MD Assistant Professor of Radiology and Imaging Sciences Pediatric Radiology Division LMEF

Disclosures None

Objectives Understand the risks of ionizing radiation Discover specifically the effects of CT radiation and how dose can be decreased Learn how to communicate radiation risk to patients and their families

Objectives Understand the risks of ionizing radiation Discover specifically the effects of CT radiation and how dose can be decreased Learn how to communicate radiation risk to patients and their families

Pediatric Conference 5/19/2015 Marshall island craters ---------------- bomb test spectators LMEF

Pediatric Conference 5/19/2015 LMEF

Shoe-Fitting Fluoroscope 1930’s-50’s

Risks of Radiation:1949 “…present evidence indicates that at least some radiation injuries are statistical processes that do not have a threshold…there is no exposure which is absolutely safe and which produces no effect.” Lewis, Leon; Caplan, Paul E. “The Shoe-Fitting Fluoroscope as a Radiation Hazard.” California Medicine 72 (1): 27. Jan 1, 1950.

Risks of Radiation:1949 “…present evidence indicates that at least some radiation injuries are statistical processes that do not have a threshold…there is no exposure which is absolutely safe and which produces no effect.” Lewis, Leon; Caplan, Paul E. “The Shoe-Fitting Fluoroscope as a Radiation Hazard.” California Medicine 72 (1): 27. Jan 1, 1950.

Background Radiation = Energy emitted from any source 2 Types: Ionizing Radiation: High frequency with energy to remove electron from atom/molecule X-rays, gamma rays, UV rays Non-ionizing Radiation: Low energy; do not directly damage DNA Visible light, infrared rays, microwaves, radiowaves

Pediatric Conference 5/19/2015 Background Radiation = Energy emitted from any source 2 Types: Ionizing Radiation: High frequency with energy to remove electron from atom/molecule X-rays, gamma rays, UV rays Non-ionizing Radiation: Low energy; do not directly damage DNA Visible light, infrared rays, microwaves, radiowaves Graph electromagnetic frequencies LMEF

Radiation Biology X-ray absorbed DNA strand breaks Recoil electron Single strand breaks Double strand breaks Unrepaired: Incorrect joining two chromosomes Basic lesion for biological effects of radiation Hall, Eric J. Radiation Biology for Pediatric Radiologists. Pediatr Radiol (2009) 39 (Suppl 1):S57-S64

Radiation Biology

Radiation Biology Three biological effects of concern Heritable Effects Effects on the Developing Embryo and Fetus Radiation Carcinogenesis

Radiation Biology Three biological effects of concern Heritable Effects Effects on the Developing Embryo and Fetus Radiation Carcinogenesis

Pediatric Conference 5/19/2015 Children are Unique More sensitive to carcinogenic effects Cells are rapidly dividing Longer lifespan Risk is greatest in early life Diagram for risk for age LMEF

Biological Effects Deterministic effects Stochastic effects Dose threshold Preventative Fluoroscopy Skin burns Stochastic effects No threshold Occurrence is dose-dependent Severity independent of dose Tumor

Biological Effects Deterministic effects Stochastic effects Dose threshold Preventative Fluoroscopy Skin burns Stochastic effects No threshold Occurrence is dose-dependent Severity independent of dose Tumor Hall, Eric J. Radiation Biology for Pediatric Radiologists. Pediatr Radiol (2009) 39 (Suppl 1):S57-S64

Deterministic Effects 18-21 months post coronary angiography Shope, Thomas B. Radiation-induced skin injuries from fluoroscopy. Radiographics 1996; 16:1195-1199.

Risk Models: Threshold 1949 …”statistical processes that do not have a threshold”… No threshold model Linear increase in risk for any dose Linear threshold assumes a finite minimum dose below which there is no increased risk Hormesis assumes a threshold below which radiation may have a (small) beneficial effect

Assume No Threshold No threshold model Attributable risk Dose (Hormesis)

Quantitative Prospective Studies re: Radiation Exposure and Cancer Risk Number of randomized controlled trials comparing medical radiation exposure to cancer risk:

Quantitative Prospective Studies re: Radiation Exposure and Cancer Risk Number of randomized controlled trials comparing medical radiation exposure to cancer risk:

Studied Population Exposure type Effects Early radiologists Fluoroscopy, scatter, brachytherapy Leukemia, cataracts, skin cancers Japanese atomic bomb survivors Direct gamma exposure, fallout (I-131) Leukemia, thyroid cancers, congenital defects Marshall Island survivors Fallout (mostly I-131) Thyroid cancers Tinea capitis patients Gamma to head Thymoma patients Gamma to neck "Radium girls" Radium ingestion Oropharyngeal cancers, bone sarcomas, leukemia Uranium miners Inhaled radon Lung cancer Chest fluoroscopy in TB sanitaria (prior to 1953) Gamma to breast (doses were VERY high) Breast cancer

Pediatric Conference 5/19/2015 Early radiologist ------------- From the movie “the Fall” LMEF

Pediatric Conference 5/19/2015 LMEF

Pediatric Conference 5/19/2015 Scalp necrosis after gamma therapy for tinea capitis LMEF

Risk Model Issues Based on retrospective data Based on doses much, much higher than are used in diagnostic imaging currently i.e. atomic bomb survivors Can we assume a linear relationship between a single acute very high dose and multiple/fractionated low doses accumulated over long periods of time? Assumes a “standard” mid-20s, 70 kg, otherwise healthy patient Ethnicity effects? Data is population-based/epidemiologic, which is not necessarily specifiable to individual patient risk

ALARA “As Low As Reasonably Achievable” Potential low risk at population level Conservative approach In reducing dose, and thus reducing the assumed risk, we should take care not to reduce dose to the point that the study is non-diagnostic

Objectives Understand the risks of ionizing radiation Discover specifically the effects of CT radiation and how dose can be decreased Learn how to communicate radiation risk to patients and their families

Pediatric Conference 5/19/2015 Early 1980s Slovis T. Where we were, what has changed, what needs doing: a decade of progress. Pediatr Radiol (2011) 41 (suppl 2): S456-S460. LMEF

Pediatric Conference 5/19/2015 Early 1980s 15% Slovis T. Where we were, what has changed, what needs doing: a decade of progress. Pediatr Radiol (2011) 41 (suppl 2): S456-S460. LMEF

Pediatric Conference 5/19/2015 2006 Pediatric Conference 5/19/2015 Slovis T. Where we were, what has changed, what needs doing: a decade of progress. Pediatr Radiol (2011) 41 (suppl 2): S456-S460. LMEF

Pediatric Conference 5/19/2015 2006 Pediatric Conference 5/19/2015 48% Slovis T. Where we were, what has changed, what needs doing: a decade of progress. Pediatr Radiol (2011) 41 (suppl 2): S456-S460. LMEF

Why CT? Not most common exam CT scans largest contributor 7 million CT exams in children/year in US Dose ~100x

Effects of CT Radiation Risk from low-level radiation from single pediatric CT uncertain Challenge US risk cancer 25% Added risk CT 0.03- 0.05% Inherent uncertainties Dose calculation Frush, Donald P. Ct dose and risk estimates in Children. Pediatr Radiol (2011) 41 (Suppl 2): S483-S487

Pediatric Conference 5/19/2015 CT Dose Estimate Dose CTDI vol DLP Age patient Sex patient Exam type Organ dose: phantoms- computerized simulated body 3D LMEF

CT Dose Estimate Objective Data Estimate CTDI volume: CT output Based on phantom data DLP: Length irradiated Estimate Wrong by an order of magnitude No organ-specific risk

Can We Predict Risk for Individual Patients? CTDI and DLP do not represent individual patient dose Not designed to characterize dose or risk to individual patients Designed for demonstrating exposures of standard populations By some estimates, error in estimating cancer risk based on individual exposures may be up to 500% Some data indicate that risk has far more to do with inherent variability in patient-specific DNA repair capacity than with radiation dose Fanconi’s anemia, Riddle syndrome, ataxia-telangiectasia, etc.

Literature on CT Radiation “In the United States, of approximately 600,000 abdominal and head CT examinations annually performed in children under the age of 15 years, a rough estimate is that 500 of these individuals might ultimately die from cancer attributable to the CT radiation.” Death from cancer will increase from 25% to 25.08% Brenner DJ, Elliston CD, Hall EJ et al (2001) Estimated Risks of radiation-induced fatal cancer from pediatric CT, AJR 176:289-296.

That Lancet article 179,000 pediatric patients receiving head CT (283,919 total scans) Radiation exposure from CT scans in childhood and subsequent risk of leukaemia and brain tumours: a retrospective cohort study Lancet, Volume 380, No. 9840, p499–505, 4 August 2012

Pediatric Conference 5/19/2015 Results 1 excess case of leukemia and 1 brain tumor per 10,000 children LMEF

But… Limitations No standardization of scan protocol Dates of scans from 1985 to 2002 Protocols are MUCH improved, doses MUCH lower Questionable statistics The authors themselves acknowledge: Risk found in the study very small compared with the lifetime cancer risk of the general population Risk likely small compared with the benefits of a clinically justified scan

Even if the 1 in 10,000 number is true, how many of those 10,000 lives were saved or prolonged by their scan?

Even if the 1 in 10,000 number is true, how many of those 10,000 lives were saved or prolonged by their scan? Estimated latency of 2 years for leukemia, 5 years for thyroid cancer, 10+ years for solid tumors Observed risk of a patient dying within 5 years from underlying disease process is 10-100x higher than the theoretical risk of a leukemia or thyroid cancer The yield of brain injury detection in pediatric head CT based on established CDM tools (blunt head trauma setting) is 1-8% Yield of an urgent incidental finding is ~1/700 Compared to 1/10,000 reported cancer risk…

ACR’s Official Response …results of a study (Pearce et al) to be published in the Lancet … should not keep parents from getting needed medical imaging care for their children If an imaging scan is warranted, the immediate benefits outweigh what is still a very small long-term risk. Children who get CT scans are doing so because of an immediate and significant health condition. These are not screening exams given to the general population of children.

Recently… Estimated risk of radiation-induced cancer from paediatric chest CT: two-year cohort study Pediatric Radiology, March 2015 issue 2 year cohort of 522 patients Relative risk of a chest CT is miniscule compared to lifetime baseline population risk But not 0 – risk/benefit analysis and appropriateness criteria for studies must still be followed

http://www.ucdmc.ucdavis.edu/radiology/health_info/CT_risk.pdf

http://www.ucdmc.ucdavis.edu/radiology/health_info/CT_risk.pdf

Riley Hospital for Children Low Dose Prior and ongoing studies working to decrease dose CT, radiography, fluoroscopy

Pediatric Conference 5/19/2015 Tube mAs Modulation — LMEF

Tailored Dose for Every Patient Pediatric Conference 5/19/2015 Tailored Dose for Every Patient Water equivalent diameter LMEF

Pediatric Conference 5/19/2015 Average dose reduction 20% LMEF

Pediatric Conference 5/19/2015 Abdomen CT Scan Dose LMEF

Pediatric Conference 5/19/2015 Chest CT Scan Dose LMEF

Pediatric Conference 5/19/2015 Head CT Scan Dose LMEF

Conclusions of CT Radiation Risk Literature demonstrates low risk No direct evidence that diagnostic CT increases mortality Assumption exists : ALARA Any radiation carries minimal risk

Objectives Understand the risks of ionizing radiation Discover specifically the effects of CT radiation and how dose can be decreased Learn how to communicate radiation risk to patients and their families

CT Dose Reporting at Riley Pediatric Conference 5/19/2015 CT Dose Reporting at Riley CT output Dose: CTDIvol (32 cm phantom): […] mGy We do our best to maintain the CT radiation dose as low as possible. The risk from CT radiation is very low. CTDI represents CT radiation dose output and not the risk or dose absorbed by the patient. These measurements help us ensure a maintenance of low dose CT scans. More information on CT radiation parameters and risks can be found at: http://iuhealth.org/riley/radiology-imaging/ct-scan/ LMEF

California Law: July 2013 Dose documentation of every CT study Annual verification of dose calculations/scanner calibration by medical physicist Required reporting of dose errors to patients (more than 20% above DRL)

Communicating Radiation Risk to Patients and Families

5 Common Questions 1. What are the risks from medical radiation? 2. How much radiation is my child receiving? 3. Will this cause cancer in my child? 4. How can we minimize the radiation dose? 5. Where can I learn more?

1. What are the Risks from Medical Radiation? No conclusive evidence radiation from diagnostic x-rays causes cancer Studies large populations exposed to radiation demonstrate slight increases in cancer risk To be safe, act as low doses radiation may cause harm

2. How Much Radiation is my Child Receiving? Exam Background Radiation Chest x-ray 1 Day Head CT Up to 8 months Abdominal CT Up to 20 months Background Radiation= Soil, rocks, building materials, water, air, and cosmic radiation

3. Will this Cause Cancer in my Child? We really do not know Differing medical opinions Estimated risk of cancer from 1 single CT 0.03-0.05% over lifetime Compares to 25% baseline risk

4. How can we Minimize Radiation Dose? Risks versus benefits ACR Appropriateness Criteria Avoid multiple scans when possible and image only indicated area Alternative studies Ultrasound, MRI

5. Where can I Learn More? Image Gently Society of Pediatric Radiology website http://www.pedrad.org

Image Gently “…Goal is to change practice by increasing awareness of the opportunities to promote radiation protection in the imaging of children”

Image Gently Referring physicians, radiologists, technologists, physicists Parents FAQs

Image Gently Informational brochures CT Fluoroscopic procedures Interventional procedures Nuclear Medicine Digital Radiography

Image Gently “My Child’s Medical Imaging Record”

Conclusions The risk of an individual scan is extremely difficult to quantify precisely, but is certainly miniscule When a CT scan is indicated, the risk of not getting the scan almost always outweighs the risk of the scan itself ACR Appropriateness Criteria Worksheet

Helpful Information www.imagegently.org www.informationisbeautiful.net/visualizations/radiation-dosage-chart/ xkcd.com/radiation/ www.imagewisely.org iuhealth.org/riley/radiology-imaging/

Helpful Information Riley Radiology: Pediatric Radiologist iuhealth.org/riley/radiology-imaging/ 317-948-6315 mbshelto@iupui.edu

Riley Hospital for Children

Thank You

Pediatric Conference 5/19/2015 References 1. Peace M, Salotti J, Little M, et al. Radiation exposure from CT scans in childhood and subsequent risk of leukemia and brain tumors: A retrospective cohort study. www.thelancet.com. Published online June 7, 2012. 2. Pierce D, Preston D. Radiation-related cancer risks at low doses among atomic bomb survivors. Radiat Res (2000), 154:178-186. 3. Brenner D, Elliston C, Hall E, et al. Estimated risks of radiation-induced fatal cancer from pediatric CT. AJR (2001) 176:289-296. 4. Slovis T. Where we were, what has changed, what needs doing: a decade of progress. Pediatr Radiol (2011) 41 (suppl 2): S456-S460. 5. Shrimpton, P, Hillier M, Lewis M, Dunn M. National survey of doses from CT in the UK:2003. The British Journal of Radiol, 79 (2006), 968-980. 6. Norris B, Wilson J. Childata: The handbook of child measurements and capabilities – data for design safety. London, UK: Dept Trade and Industry, 1995. 7. Peebles L, Norris B. Adultdata: The handbook of adult anthropometric and strength measurements – data for design safety. London, UK: Dept Trade and Industry, 1998. 8. Kim K, Gonzalez A, Pearce M, et al. Development of a database of organ doses for pediatric and young adult CT scans in the UK. Radiation Protection Dosimetry (2012), 1-12. 9. Linet M, Kim K, Rajaraman P. Children’s exposure to diagnostic medical radiation and cancer risk: epidemiologic and dosimetric considerations. Pediatr Radiol (2009) 39 S4-S26. 10. Brenner, David J.; Hall, Eric J. (2007). "Computed Tomography — an Increasing Source of Radiation Exposure". New England Journal of Medicine 357 (22): 2277-2284. LMEF

References 11. Image Gently. http://www.pedrad.org/associations/5364/ig/. Accessed September 2012. 12. Kleinerman, Ruth A. Radiation-sensitive genetically susceptible pediatric sub-populations. Pediatr Radiol (2009) 39 (Suppl 1):S27-S31 13. Hall, Eric J. Radiation Biology for Pediatric Radiologists. Pediatr Radiol (2009) 39 (Suppl 1):S57-S64 14. Frush, Donald P. Ct dose and risk estimates in Children. Pediatr Radiol (2011) 41 (Suppl 2): S483-S487 Jablon, Seymour MA; Hrubec, Zdenek, ScD; Boice, John D Jr, ScD . Cancer in Populations Living Near Nuclear Facilities:  A Survey of Mortality Nationwide and Incidence in Two States. JAMA. 1991;265(11):1403-1408. Brenner DJ, Elliston CD, Hall EJ et al (2001) Estimated Risks of radiation-induced fatal cancer from pediatric CT, AJR 176:289-296. Linet MS, Kim KP, Rajaraman P (2009) Children’s exposure to diagnostic medical radiation and cancer risk: epidemiologic and dosimetric considerations. Pediatr Radiol 39:S4-S26. Brenner DJ, Doll R, Goodhead DT et al. (2003) Cancer risks attributable to low doses of ionizing radiation: assessing what we really know. Proc Nat Acad Sci USA 100(24):13761-13766. Shope, Thomas B. Radiation-induced skin injuries from fluoroscopy. Radiographic 1996; 16:1195-1199.