Protocol makes low-dose lung biopsies a reality

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 - Lung Cancer Biopsy
A suspicious lung nodule targeted for biopsy on CT.
Source: David F. Yankelevitz, MD

Utilizing two dose-reduction strategies during lung biopsies has a long-term effect on lowering patient dose, according to a University of California San Fransisco (UCSF) study

The last decade in radiology has seen a shift away from high-power imaging to strategies attempting to curb patient dose such as the Image Gently campaign. CT biopsies in particular can result in high doses by virtue of repeated imaging during their three-step process, presenting a clear opportunity for dose reduction.

“Previous work with low-dose CT-guided lung biopsies was limited by small sample sizes and relatively short follow-up periods to evaluate dose reductions,” wrote Associate Professor David Naegar, MD, associate professor at UCSF, et al. “This study examines the effect of a section-wide implementation of a low-dose CT-guided lung biopsy protocol in a high-volume referral center, including evaluation of the radiation doses over 18 months.”

Researchers achieved the majority of dose reduction by modifying the kilovoltage peak (kP) and milliamperes (mA) in the original protocol. mA can be reduced by adapting the dose based on body parts rather than patient weight, because thinner parts need less radiation.

In addition, the air-filled lungs offer a high-contrast background to guide the biopsy, allowing clinicians to reduce mA by three to four times. Lowering the dose of kV works best in children and small-sized adults, but the increase in image noise across the board is acceptable for biopsies.

After following the patients for 18 months, researchers found a sustained decrease in overall dose, regardless of which radiologist performed the procedure. The greatest decrease in dose happened in the planning stage of the biopsies, and the rate of complications and non-diagnostic biopsies was similar to studies conducted with a standard CT dose.

“This confirms that a low-dose CT-guided biopsy protocol can be successfully implemented with a sustained reduction in the doses used,” wrote Naegar et al. “In addition, our study is the first to perform analysis of CT-guided lung biopsy dose reduction at the individual attending radiologist level. In our section, all radiologists had a reduction in their radiation doses following the protocol change, three of which were statistically significant.”