Lower Dosage CT-guided Lung Biopsy
Protocol Maintains Quality, Minimizes
Exposure
Jeremy Collins, MD
Pegah E, Lewandowski RJ, Yaghmai
V, Nemcek jr AA, & Carr JC
Northwestern University, Chicago, IL
Outline
• Lung Cancer Epidemiology
• Lung Nodule Evaluation
• Low Dose CT Guidance Protocol Study
• Newer Techniques to Lower CT Dose
• Conclusion
Lung Cancer Epidemiology
• Lung cancer is the 2nd most common cancer
type in both genders
– Leading cause of cancer mortality
– Lung nodule, mass
– Extrapulmonary disease
• Clinical models for lung cancer risk limited
– Tobacco use
– Accurate screening test necessary
Background
• Chest x-rays initial test for lung evaluation
– Inexpensive
– Low radiation dose
– Limited sensitivity for early disease
– Screening programs provided little benefit
• Chest Computed Tomography superior for lung
evaluation
– More expensive
– Extremely sensitive for lung disease
National Lung Cancer Screening Trial
• National Lung Cancer Screening Trial evaluated
utility of CT screening for lung cancer
– Preliminary results reported August 4, 2011
– Studied asymptomatic, high-risk patients
• 55 to 74 years of age
• > 30 pack-year tobacco use history
– Subjects randomized to annual screening with
either Chest x-rays or CT
– Annual screening for three years
National Lung Cancer Screening Trial
• 53,454 patients, enrolled at 33 centers in U.S.
• Abnormal findings
– 24.2% CTs vs 6.9% of Chest x-rays
• Further evaluation excluded cancer
– 96.4% CTs vs 94.6% of Chest x-rays
• CT screening resulted in 20% reduction in lung
cancer specific mortality
Lung Nodules
• Most common finding at CT concerning for
cancer
• Diagnostic imaging characteristics not definitive
– Nodule size
– Growth
– Metabolism
• Biopsy is necessary to determine etiology
Biopsy Techniques
• CT is commonly
utilized for biopsy
• Skin entry site
identified
• Needle advanced
through lung tissue
• Lesion sampled
• Risks: Air leak,
bleeding, radiation
exposure
CT Radiation Dose
• CT imaging and guidance procedures
associated with finite radiation exposure
– Limited data to evaluate impact of small dose
– Theoretical risks extrapolated from atomic
bomb survivor data
– Cancer risk is incremental, linear
– Interventional Radiologists strive to minimize
patient dose for all procedures
Low Dose CT Guidance Protocol Study
• Lung nodules are surrounded by air-filled lung
– Readily identified at CT
– Lower dose acquisitions enable safe biopsy
guidance
• Low dose CT guidance protocol instituted at
Northwestern in August 2011
– Modifications to manufacturer provided CT
guidance protocol
– Applicable to any multidetector scanner
Low Dose CT Guidance Protocol Study
• Retrospective Analysis, single institution
– 50 consecutive biopsy procedures before &
after protocol change
– Procedures performed by interventional
radiologists
– Dose metrics
– Protocol adherence
– Image quality
– Complications evaluated
Low Dose CT Guidance Protocol Study
• 66% average dose reduction
– 3.5 mSv (1.0 - 8.0) vs 10.3 (1.7 - 52.4)
– Comparator: CxR 0.06 mSv, Chest CT 8 mSv
• No difference in nodule size, biopsy difficulty
• 100% adherence to new protocol
• Complications were minor, similar between
groups
Lung Nodule Biopsy
Spiral Planning
Low Dose Guidance
Lung Nodule Biopsy
Planning Scan
Guidance Scan
Additional CT Dose Reduction Techniques
• Automated Exposure Control
– Optimization of tube current to patient size,
attenuation
• Iterative Reconstruction
– Newer technique to improve noise
characteristics
– Improves image quality at lower doses
• Body Mass Index Adjusted Parameters
– Smaller patients
Conclusion
• Lung cancer leading cause of mortality, CT
screening of high risk patients will likely become
routine
• Low-dose CT biopsy techniques are necessary
to minimize risk to screening cohort
• Interventional Radiologists are experts in image
guided procedures & well-positioned to
champion low-dose CT guided techniques for
lung nodule biopsy