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 2 nd 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 ( ) vs 10.3 ( ) –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 PlanningLow Dose Guidance

Lung Nodule Biopsy Planning ScanGuidance 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