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

To evaluate needle visibility in ultrasound under contrast mode conditions.

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.

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).

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.