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

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 ( rgrayscale =0.109, p grayscale =0.178; rcolor-coded =0.236, p color-coded =0.266; rdB =0.956, p dB =0.001), EchoTip ® ( rgrayscale += 0.477, p grayscale += 0.018; rcolor-coded =0.540, p color-coded += 0.006; rdB =0.911, p dB =0.001) and shaft ( rgrayscale =0.124, p grayscale =0.563; rcolor-coded =0.061, p color-coded += 0.775; rdB += 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.