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Dose Reduction in CT - Practical Lessons for All Technologists
Transcript of Dose Reduction in CT - Practical Lessons for All Technologists
CT Dose Reduction...
Daniel N. DeMaio
University of Hartford
Proper Utilization of CT
Tech error during CT neck - child burned
CT perfusion overdose at Cedar-Sinai Hospital
Walt Bogdanich series in the NY Times
Physicians & researchers
Patients & the media
Recent Media Coverage
1. National initiatives to reduce dose:
Amis, ES. CT Radiation Dose: Trending in the Right Direction. Radiology 2011; 261(1): 5-8.
Levin DC, et.al. The Recent Downturn in Utilization of CT: The Start of a New Trend?. JACR 2012; 9:795-798
Are We There Yet?
CT Utilization in the U.S
13.9% of all ER visits included CT in 2007 (3.2% in 1996)~
HMO: 52 CT exams per 1,000 patients in 1996 to 149 exams in 2010^
More than 85 million exams in 2011*
~Kocher, KE, Meurer, WJ, et.al. National trends in use of computed tomography in the emergency department. Annals of Emergency Medicine. 2011; 58(5): 452-462
^Smith-Bindman, R., et.al. Use of diagnostic imaging studies and associated radiation exposure for patients enrolled in large Integrated Healthcare systems, 1996-2010. JAMA. 2012; 307(22): 2400-2409.
*Brice, J. "CT's Growth rate slows, but users remain optimistic." Auntminnie.com 4 June 2012. Web. Accessed 10 June 2012.
CT and Radiation Dose
Annual radiation exposure in US is 7-times greater in 2006 compared to the 1980's.^
More than 45% of the effective dose from medical radiation exposure is attributed to CT.*
As many as 29,000 new cancers in US may be related to CT exams in 2007.~
^National Council on Radiation Protection and Measurements. Ionizing radiation exposure of the population of the United States (2009). NCRP report no.160. Bethesda, Md: National Council on Radiation Protection and Measurements, 2009.
*Fazel R, et.al. Exposure to low-dose ionizing radiation from medical imaging procedures. N Engl J Med 2009; 361:849-57.
~Berrington de Gonzalez, A, et.al. Projected cancer risks from computed tomographic scans performed in the United States in 2007. Arch Intern Med 2009; 169:2071-7.
2. Innovations from vendors
3. Downturn in utilization for 2010
for Medicare patients
for private offices*
Image Gently & Wisely
ACR Appropriateness Criteria and CT Dose Index Registry
CT utilization in the ER (Medicare)
The Lancet (June 2012)* - increased risk of leukemia & brain tumors
Institute of Medicine (IOM) - avoid CT examination to reduce the risk of breast cancer. ^
Wall Street Journal Report - June 19, 2012
*Pearce, MS, et.al. Radiation exposure from CT scans in childhood and subsequent risk of leukaemia and brain tumours: a retrospective cohort study. The Lancet, Early Online Publication, 7 June 2012 doi: 10.1016/
^Smith-Bindham, R. Environmental causes of breast cancer and radiation from medical imaging. Arch Intern Med. Online, 11 June 2012 doi:10.1001archinternmed.2012.2329
The Role of the CT Technologist in the Ongoing Dose-Risk Debate
We need to focus on:
Effective communication with patients, physicians, and other colleagues.
Elimination of errors
Dose reduction techniques
Practical methods of CT dose reduction:
System-based methods of CT dose reduction:
Precise beam control
Substantial (6-9 mm Al equiv.) filtration
Automatic Tube Current Modulation (ATCM)
Automated Tube Potential Selection (CARE kV)
Iterative reconstruction (ASIR, VEO, IRIS, iDose)
Protocol design & adaptation
...for the rest of us!
Utilization & Optimization
The CT technologist plays a vital role in each!
No CT head for uncomplicated headaches
Reconsider CTPA in absence of elevated d-Dimer and/or other associated risk factors
Ultrasound first, before CT in suspected cases of pediatric appendicitis
Imaging related guidelines:
Patient age, sex, and dimensions
Required phases of contrast enhancement
"...the process of maintaining diagnostic quality while minimizing the ionizing radiation dose required to capture an image." (Wallace, Goergen, 2010)
Customization of Protocols
"What technique do I use?"
How to optimize?
Promoting Alternative Studies
—12-year-old boy with known Crohn disease and increasing abdominal pain.
Coakley F V et al. AJR 2011;196:619-625
©2011 by American Roentgen Ray Society
Conspicuity of pathology
Tolerable noise level
To shield or not to shield?
Summary of Dose Reduction Strategies
Limit acquisition phases to the bare minimum
Make adjustments for every case - customize!
Turn up the noise...
More noise = less dose
How much noise will the indication (& the radiologist) tolerate?
Kalra, MK, et.al. Pointers for optimizing radiation dose in abdominal CT protocols. JACR 2011 Oct;8(10):731-4.
mAs = mA x time
Direct & linear relationship with patient dose
Use half the mAs and dose decreases by one-half (noise increases 40%)
Make reductions that are age-specific, size-specific, and "indication-specific."
Optimize protocols using CTDIvol
Coakley F V et al. AJR 2011;196:619-625
Singh S., et.al. JACR 2011; 8(5):369-372
Yu L et al. Radiographics 2011;31:835-848
Tube Potential (kVp)
Remember the 15% rule?
Reducing kVp from 140 to 120 results in a 35-40% dose savings
As kVp decreases, noise and contrast increase
CTA's - try 80-100 kVp
Perception is reality.....
Play an active role in the process of justification:
Empower Technologists to Adjust Protocols
"Experienced CT technologists can make significant dose-reducing modifications while maintaining diagnostic image quality."
CT Radiaton Dose: What Can You Do Right Now in Your Practice?
Coakley FV, et.al.
AJR 2011, 196:619-625
Dose Length Product (DLP)
Above and below patient
Always use when possible
Little risk when used correctly
In-plane bismuth shields:
can effectively reduce organ dose - breast, thyroid, orbits, etc.
may improve patient comfort & confidence
wastes radiation and decreases signal
causes some streak artifact
risk of AEC malfunction
"...the ways in which bismuth shielding can hurt outnumber the ways in which it helps. Equally or more effective alternatives exist to minimize radiation dose to the breast, thyroid, and lens of the eye without degrading image quality or wasting dose."
Bismuth Shields for CT Dose Reduction: Do They Help or Hurt?
McCollough CH, et.al.
JACR 2011, 8(12):878-879
The responsibility is ours....
Daniel N. DeMaio
University of Hartford
Dana Hall 433
200 Bloomfield Avenue
West Hartford, CT 06117
A word of caution:
"Increasing radiation causes a very small statistical future societal increased risk of cancer. Lowering radiation for a CT scan creates
a very real immediate risk
to the specific patient...This is the risk of
missing the correct diagnosis
because the exposure factors are too low and image quality is poor."
CT Radiaton Dose Reduction: Can We Do Harm by Doing Good?
Pediatr Radiol 2012, 42:397-398
May 18, 2013
During CT of the chest, the glandular dose exceeds MQSA's recommended maximum of 3 mGy. Therefore the author's state:
"...in plane breast shielding remains a feasible and effective technique for breast protection."
CT Bismuth Breast Shielding: Is It Time to Make Your Own Decision? Zhang J & Oates ME
JACR 2012, 9(12):856-858
Goals of our discussion:
Review the current state of the CT dose issue.
Provide a brief overview of system features designed for dose reduction.
Outline the practical methods of CT dose reduction:
"...25% - 35% of pediatric [CT] examinations may not be indicated."
Slovis TL. The ALARA Concept in Pediatric CT: Myth or Reality. Radiology 2002; 223:5-6
One institution: 2008 to 2010, CT usage rates in children up to 18 years old were relatively unchanged or slightly decreased.
Bahman BS, et.al. CT Use in Hospitalized Pediatric Trauma Patients: 15-year Trends in a Level I Pediatric and Adult Trauma Center. Radiology 2013; 267:479-486
Children are at greater risk:
Greater organ radiosensitivity
Longer post-radiation life span
NCRP Report 160
Single-phase imaging for pediatric CT studies!
Once is enough!
Noise can be problematic in thinner and younger patients.
Fixed mA for Pediatric CT
Establishing good communication with radiologist(s) is vital!
A technologist can play an active role in the justification process...
Fixed mAs - How low can you go?
240 vs. 80 mAs
2 Methods for Determination:
Image Gently: adaptation of adult head/body techniques.
Broselow-Luten color-coded pediatric system: based upon patient weight.
Consult with Radiologists - Be Aggressive!
Low kVp techniques...
100 kVp for children & teens
80 kVp for infants
Determine an acceptable noise level based upon the specific patient & exam indication.
Adjust mAs & kVp accordingly
"Cheat" with kVp - lower it when possible (high contrast)
Radiation Protection 101 - shorten time & SHIELD!
10 y.o. female - 90+ lbs
100 kVp & 80 mAs
14.1 noise index
sub-1 mSv effective dose
Aim for >1
Keep an eye on the mAs!
Reduces dose, but increases noise!
*Also decreases z-axis resolution...
Decrease that gantry rotation time!
Use the CTDIvol and noise index as a guide
Limit z-axis coverage:
Abd/pel - top of diaphragm to inferior pubic symphysis
Kidney Stone Protocol - start at top of kidneys
CTPA - don't include adrenals
The key metric of absorbed dose to the patient
DLP = CTDIvol x scan length
Minimize that scan length!
Don't overscan just to "be sure."
Arms should be raised whenever possible!
Decreases streak artifact
Can substantially reduce dose with AEC
Goals of the presentation:
*Levin DC, et.al. The Recent Downturn in Utilization of CT: The Start of a New Trend? JACR 2012; 9:795-798