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Optimizing Patient Radiation Safety in the
Era of Multidetector Helical CT
Steven Birnbaum, M.D.
Staff Radiologist and Radiation Safety Officer
Southern New Hampshire Medical Center
Nashua, New Hampshire
Parkland Medical Center
Derry, New Hampshire
Member, American College of Radiology Blue Ribbon Panel on
Radiation Dose in Medicine
Optimizing Patient Radiation Safety in the Era of
Multidetector Helical CT

Arthur Schopenhauer
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19th Century German Philosopher
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“All truth passes through three stages.
First, it is ridiculed.
Second, it is violently opposed.
Third, it is accepted as being self-evident.”
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Adapted from Budoff and Shinbane, Cardiac CT Imaging, Springer Verlag, 2006
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Optimizing Patient Radiation Safety in the Era of
Multidetector Helical CT
• Recent Events-
• 2007: Brenner and Hall Review in NEJM/Published during RSNA
• 2009: Cedars-Sinai CT Perfusion Overexposures for Perfusion Head
CT’s
• 2009: Smith-Bindman et al, Archives of Internal Medicine: Variable
Output by 13 fold of SF Bay Area CT scanners
• 2010: FDA Initiative to Alert Clinicians
and Patients about CT
Text
Exposure Issues
• 2010: California Legislation Requiring Dose Data on Reports
Optimizing Patient Radiation Safety in the Era
of Multidetector Helical CT
– Radiation Risks
– What are they?
– There are no Answers/Only Extrapolations and
Best Guesses
– We Don’t Know
– I am NOT a Physicist
Optimizing Patient Radiation Safety in the Era
of Multidetector Helical CT
• Units of Dosage
– Millisievert
• Measurement of effective radiation dose
• Different organs in the body have different
sensitivities to radiation
• Effective dose takes into account these differences
and averages organ absorbed doses over the entire
body
• Effective dose allows comparison between different
types of exams, natural background radiation, and
different types of ionizing radiation
Optimizing Patient Radiation Safety in the Era
of Multidetector Helical CT
•
Other Units of Radiation Dose Pertinent to CT
– C.T. Dose Index (C.T.D.I.w)
• Measure of CT Radiation Dose Delivered
• Manufacturer Requirement for each Scanner Placed on Console
• Calculated using Reference Phantoms on Single Axial Image
– C.T.D.I.vol
• Adjusts for Scanning Parameters
• Pitch
• Beam Width
– Dose Length Product (D.L.P.)
• Calculated from CTDIvol Times Area Scanned
• Provided on user interface of all scanners
• Can be converted to effective dose with a table of conversion
• Standardized dose ranges are used in ACR CT accreditation program
– Estimated Dose
• Can be Grossly Estimated from DLP Using “Fudge” Factor
• Heads-0.0023/Chest-0.017/Abdomen-0.015/Pelvis-0.019
Optimizing Patient Radiation Safety in the Era
of Multidetector Helical CT
•
Radiation Dosage and Effect
– 10,000 mSv- Radiation sickness
with immediate illness and death
w/i several weeks
– 1,000 mSv- Immediate radiation
sickness , unlikely to cause death
– 100-1000 mSv –Clear dose related
increasing risk of carcinogenesis
– 50 mSv- Clearly associated with
increased cancer risk and the
highest dose recommended yearly
in occupational exposure
– 20 mSv/year averaged over 5
years- Highest recommended
allowable dose for radiation
workers
– 3-5 mSv/year- Typical dose rates
of uranium miners in Australia and
Estimated Radiation Dosages of
Common Medical Procedures
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Chest X-Ray- 0.1-0.2 mSv
Infant VCUG- 0.8 mSv
Head CT- 2 mSv
Chest CT- 8 mSv
CT Pulmonary Arteriogram- 8 mSv
Cardiac Catheterization- 2.5 mSv
Helical Cardiac CT/Male- 8.8 mSv
Helical Cardiac CT/Female- 10.5 mSv
Renal Stone CT - 10 mSv
“Low Dose” Renal Stone CT- 6 mSv
Abdomen- Pelvis CT- 10 mSv
PET/CT Fusion-20 mSv
Optimizing Patient Radiation Safety in the Era
of Multidetector Helical CT
• The Scope of the Problem
– Over 70 Million CT studies Performed in the U.S. in
2009
– 15% of the Volume of Radiographic Procedures
– 60% of the Estimated Population Exposure from
Diagnostic Radiation Comes from CT
– Southern New Hampshire Medical Center- 2,000 CT
studies in 1985/18,000 in 2006/20,000 + in 2009
– Outsourcing of CT Reading in Off Hours
Optimizing Patient Radiation Safety in the
Era of Multidetector Helical CT
• Clinical Examples From Our Practice
– Patient 1- 14 year old with hypercalciuria and multiple episodes of renal
colic was noted to have had 14 renal stone CT studies in a four year
period. Total “estimated dosage”- 140 mSv.
– Patient 2- 28 year old AIDS patient with multiple Emergency Room visits
receives 8 renal stone CT studies and 2 abdomen and pelvis studies in a
2 year period. Total “estimated dosage”- 100 mSv.
– Patient 3- 22 year old patient with multiple visits to the Emergency
Room over 5 years receives 5 Head CT studies, 7 Abdomen and Pelvis
CT studies, and 5 CT pulmonary arteriograms. Total “estimated dosage”120 mSv. The mammographic equivalent exposure for this 22 year old
patient would be 50-125 2 view screening mammograms.
Optimizing Patient Radiation Safety in the
Era of Multidetector Helical CT
• Clinical Examples From Our Practice
– Patient 4- 39 year old patient has 4 neck CT studies and 3 CT and
globus pulmonary arteriogram studies in a one year interval for panic
attacks. Total “estimated dosage”- 60 mSv.
– Patient 5- 31 year old female with renal stones and many episodes of
renal colic. She had 14 renal stone CT’s at one of our hospitals and
reports an additional 20 studies done at a tertiary care hospital in Boston.
Total “estimated dosage”- 340 mSv.
– Patient 6- 46 year old female patient with multiple episodes of renal
colic. She has had 23 renal stone CT’s and 73 KUB’s at one of our
hospitals over a 7 year interval. Total “estimated dosage”- 370 mSv.
Optimizing Patient Radiation Safety in the Era
of Multidetector Helical CT
– Demographics of Frequent Exposure to CT at SNHMC, 11/2008
• PATIENT DEMOGRAPHIC
NUMBER OF PATIENTS
•ER Patients/No Insurance/Episodic Care/Multiple Medical Problems 21
•Renal Stone Disease
•Chronic Abdominal Pain w/Normal Imaging
•Pulmonary Embolus Evaluation
•Diverticulitis
•Crohn's Disease
•RIS Data Mining with Crystal Reports
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Optimizing Patient Radiation Safety in the Era
of Multidetector Helical CT
• Technical Factors Under Radiologist Control
– Bismuth Breast Shields
– Initial Scout Views Done in PA Projection in Female Patients
– Minimize Technique (mA and kV) in order to Minimize Exposure
• Manually or Automatically
• Dose Modulation in One or Multiple Planes
• Use Shielding After Scout Views with Automatic Dose Modulation
– Center Patient in Gantry
– Iterative Reconstruction Algorithms
– Cardiac CTA
• Breast Shields Cause Streak Artifact in Distribution of RCA
• EKG Dose Modulation-Needs Very Low Heart Rates to be Effective
– Minimize Body Area to be Scanned
– Avoid Dual/Multiphase Imaging when Possible
– Decrease Scan Time/Increase Pitch
– Spot Check Dose Reports Now Sent to PACS on Most Scanners
– Avoid Repeats, “Re-does” and “Extra” Images
• Careful Explanation by the Technologist of Breath Holding
Optimizing Patient Radiation Safety in the Era of
Multidetector Helical CT
Optimizing Patient Radiation Safety in the Era
of Multidetector Helical CT
– Education (!!!!!!!!!!!!!): Spearheaded by
Radiologists
• Radiologists at Each Institution as “Champions”
• Radiologists
• Emergency Physicians
• Cardiologists and Surgeons
• Encourage Evidence Based Practice
• Encourage Use of Non-ionizing Modalities as
Alternatives
• Will the Study Change Management?
– Renal/Ureteral Stone CT Studies in Renal Colic
Optimizing Patient Radiation Safety in the Era of
Multidetector Helical CT
Optimizing Patient Radiation Safety in the Era
of Multidetector Helical CT
• Patient Identification by Radiologists
– Patients Under the Age of 40
– Benign Diagnoses
– Use of 50 mSv Lifetime Threshold Dosage Estimate
– Review of Imaging Histories by Technologists and
Radiologists
• Empowerment of CT Technologists
– Review of Identified Patients by RSO
– Flagging of Patient in RIS
– Certified Letters to Providers and Patients
– Data “Mining” in RIS
• Crystal Reports
• Elimination of Referring Oncologists
Optimizing Patient Radiation Safety in the Era
of Multidetector Helical CT
• Patient Identification by Radiologists
– Imaging Consultation Required in “Flagged
Patients” Prior to CT Performance
– Index Patient- Three years and No CT Studies,
12 Renal Ultrasounds and 1 One-shot IVP
– Regular Imaging Consultation and Excellent
Clinician Acceptance
Optimizing Patient Radiation Safety in the Era of
Multidetector Helical CT
Optimizing Patient Radiation Safety in the Era
of Multidetector Helical CT
• Investigation of “Extreme Exposure” by
Radiologists
– More than 100 mSv Dose Estimate
– Notification of Provider and Patient via Certified Mail
– Availability of Counseling to Patients by RSO
– Empowerment of Patient
– Knowledge of Imaging Histories at Other Institutions
by Providers and Patients
Optimizing Patient Radiation Safety in the
Era of Multidetector Helical CT
Optimizing Patient Radiation Safety in the Era
of Multidetector Helical CT
• Regional and State Efforts at Patient Radiation Protection
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Educational Forums
“Tool Kits” for Hospitals, Imaging Centers and Offices
State Radiology Society Policy Initiative
Inter-specialty Cooperation
Modify Missions of State Radiation Protection Efforts
• Currently Device and Occupational Exposure Emphasis
• Change Emphasis to Patient Radiation Exposure Protection
• Recent California Legislation Requiring DLP on report
– Insurance Company Efforts at Radiation Protection
• Anthem Programs
– “Tool Kits” on Web and on Forest Products
– Provider Notification of Frequent Exposure
– Pay for Performance Initiatives
• National Imaging Associates/Magellan
– Use of Pre-certification Data to Identify Frequently Exposed Patients
Optimizing Patient Radiation Safety in the Era
of Multidetector Helical CT
• American College of Radiology Blue Ribbon
Panel on Radiation Dose in Medicine
– Followed NCRP Report, April, 2007
– Charge: Comprehensive Review of Current Issues,
Controversies and Directions of ACR Patient Radiation
Protection Efforts
– Members
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Academic and Private Practice Radiologists
ACR Staff Members
Health Physicists
Equipment and NEMA Representatives
FDA/CDRH Representative
Patient Advocate
Optimizing Patient Radiation Safety in the Era
of Multidetector Helical CT
• White Paper in May, 2007
• Recommendations
– “…the presumption is yes” whether the
increased cumulative exposure to ionizing
radiation will increase population cancer
incidence
Optimizing Patient Radiation Safety in the Era
of Multidetector Helical CT

Results of the SNHMC Radiation Safety Program
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Year 1- 52 “Flagged Patients” Had CT’s Ordered
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15% Cancelled
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15% Changed to Non-ionizing Modalities
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1 Study Performed at Patient Insistence
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30% Done at Clinician Insistence
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40% Done Following Clinician/Radiologist Consultation
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Performance Variability Among Radiologists
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“Just Do It”- The Nike Approach
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Leave it up to the Technologists
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Active Consultation Results in Fewer Repeat Studies
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Optimizing Patient Radiation Safety in the
Era of Multidetector Helical CT
• Conclusions of the ACR White Paper
– Rapid Increase in CT and Certain Nuclear Medicine
Studies Over the Last 20 Years May Result in an
Increased Incidence of Radiation Related Cancer
– We Can Do Something about this NOW Before it is too
Late.
• Is Patient Radiation Exposure in 2010 the
Medical Equivalent of Climate Change and
Global Warming?