Effective dose during needle interventions: cone-beam CT guidance compared with conventional CT guidance.

PURPOSE

To determine effective radiation dose to patients during needle interventions with cone-beam computed tomography (CT) guidance and compare it with the dose during conventional CT-guided interventions.

MATERIALS AND METHODS

Cone-beam CT guidance is a recently developed technique with image acquisition on a flat-panel detector digital angiography system. It is based on a combination of acquired three-dimensional soft-tissue cone-beam CT, dedicated needle trajectory software, and fluoroscopy, providing stereotactic needle guidance. To analyze effective dose, we prospectively recorded all contributing parameters necessary to calculate it in 92 needle interventions (in 88 patients [60 men]; mean age, 63.9 y) using a Monte Carlo program. For CT guidance, we retrospectively scored the necessary parameters during 137 needle interventions (118 patients [81 men]; mean age, 59.5 y) to calculate effective dose with a CT patient dosimetry calculator. The needle interventions were categorized in four regions.

RESULTS

Total mean effective doses with cone-beam CT guidance were 7.6 mSv in the upper thorax, 12.3 mSv in the lower thorax, 16.1 mSv in the upper abdomen, and 13.4 mSv in the lower abdomen. Effective doses with uncollimated cone-beam CT alone were 2.0, 2.9, 4.2, and 3.5 mSv in the respective regions. Effective doses with CT-guided interventions were 13.0, 15.1, 20.4, and 15.4 mSv in the respective regions. Cone-beam CT guidance results in a reduction of 13%-42% of total effective dose compared with conventional CT guidance. The dose reduction is mainly attributable to cone-beam CT, not to fluoroscopy.

CONCLUSIONS

A new needle intervention technique with cone-beam CT guidance results in a considerable effective dose reduction for patients compared with conventional CT guidance.