Ultrasound Needle Visibility in Contrast Mode Imaging: An in Vitro and Ex Vivo Study

Abstract

Purpose To evaluate needle visibility in ultrasound under contrast mode conditions. Materials and Methods Needle visibility was evaluated for bevel, EchoTip ®and shaft of 18G Chiba biopsy needle with a 9 MHz linear probe (GE Logiq E9). Insertion angles varied between 30°(steep) and 90°(parallel to the probe surface). The acoustic output varied from 5-28%. 2 different contrast mode presets with either 'Amplitude Modulation' (Penetration) or 'Phase Inversion Harmonics' (High Resolution) were assessed. All other imaging parameters were kept constant. The visibility of bevel, EchoTip ®and shaft was assessed for grayscale and color-coded images with a 3-point Likert-like scale (not, poorly, well visible) by 2 independent readers. The echogenicity of the needle bevel, EchoTip ®and shaft was assessed in deciBel (dB) on the color-coded images. Results With the parallel insertion angle, all needle areas were well visible. With steep insertion the EchoTip ®was the only visible area. High Resolution was superior to Penetration (p<0.001). The visibility and echogenicity of the needle bevel (r grayscale=0.109, p grayscale=0.178; r color-coded=0.236, p color-coded=0.266; r dB=0.956, p dB=0.001), EchoTip ®(r grayscale+= 0.477, p grayscale+= 0.018; r color-coded=0.540, p color-coded+= 0.006; r dB=0.911, p dB=0.001) and shaft (r grayscale=0.124, p grayscale=0.563; r color-coded=0.061, p color-coded+= 0.775; r dB+= 0.926, p dB=0.001) increased with increasing acoustic output. Grayscale images were superior to color-coded images for needle visibility (p=0.004). Conclusion Parallel needle insertion, use of an echogenic tip, adequate choice of presets, increased acoustic output, and dual view of grayscale and color-coded images improve needle visibility in ultrasound under contrast mode conditions.