Lower Dosage CT-guided Lung Biopsy Lower Dosage CT-guided Lung Biopsy Protocol Maintains Quality, Minimizes Protocol Maintains Quality, Minimizes

ExposureExposure

Jeremy Collins, MD

Pegah E, Lewandowski RJ, Yaghmai V, Nemcek jr AA, & Carr JC

Northwestern University, Chicago, IL

OutlineOutline

• Lung Cancer Epidemiology

• Lung Nodule Evaluation

• Low Dose CT Guidance Protocol Study

• Newer Techniques to Lower CT Dose

• Conclusion

Lung Cancer EpidemiologyLung 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

BackgroundBackground

• 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 TrialNational 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 TrialNational 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 NodulesLung 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 TechniquesBiopsy 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 DoseCT 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 StudyLow 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 StudyLow 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 StudyLow 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 BiopsyLung Nodule Biopsy

Spiral Planning Low Dose Guidance

Lung Nodule BiopsyLung Nodule Biopsy

Planning Scan Guidance Scan

Additional CT Dose Reduction TechniquesAdditional 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

ConclusionConclusion

• 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