Standardizing CT-Guided Biopsy Procedures: Patient Dose and Image Noise

OBJECTIVE. The objective of this study was to standardize our image acquisition protocol for CT-guided biopsy procedures. MATERIALS AND METHODS. The records of consecutive patients who underwent CT-guided biopsy 3 months before (n = 598 biopsies) and 3 months after (n = 540 biopsies) standardization of our image acquisition protocol were retrospectively reviewed. CT technical parameters were individualized on the basis of the sum of the anteroposterior and transverse dimensions of the patient. Information on patient demographic characteristics, biopsy site, complications associated with the procedure, and diagnostic yield was collected. The radiation dose metrics that were evaluated included the volume CT dose index, dose-length product, and size-specific dose estimate. Image noise was quantified using the SD of the CT number measured in subcutaneous fat. Fisher exact test and one-way ANOVA were used to evaluate statistical significance. RESULTS. The mean dose-length product decreased by 72.3% (from 699.7 to 193.9 mGy x cm; p < 0.0001), and statistically significant decreases in dose-length product were observed when data were stratified according to biopsy site (i.e., lung, solid organ, lymph node, or bone; for all sites, p < 0.0001). The mean size-specific dose estimate decreased by 58.9% (from 125 to 51.4 mGy), which was statistically significant (p < 0.001). Image noise increased during the study period, but this increase was not statistically significantly different among the four biopsy sites (p = 0.46). CONCLUSION. Standardization of the image acquisition protocol used in CT-guided biopsy procedures significantly reduced patient radiation dose and decreased variability in image noise.