Table 2.

Characteristics of single-frequency mechanical IVUS transducers.

Categories	Center Frequency	−6-dB Bandwidth	$\mathbf{Acoustic} \mathbf{Impedance} \mathbf{of} {\mathit{Z}}_{\mathit{p}}$	Volume Fraction	kt	Focal Length	Aperture Size	Axial Resolution	Lateral Resolution
Using high-performance piezoelectric material	82 MHz [139]	65%	-	-	55	-	0.4 × 0.4 mm2	35 μm	176 μm
	30.5 MHz [140]	53%	26.7 MRayls	-	41	-	0.8 × 0.8 mm2	-	-
	42 MHz [141]	79%	30.2 MRayls	-	60	-	0.33 × 0.33 mm2	36 μm	141 μm
Using 1-3 composite structure	41 MHz [142]	77%	17.8~21.5 MRayl	65 ± 5%	71 ± 4	-	-	-	-
	60 MHz [154]	77%	<20 MRayls	~40%	70	-	< 0.6 $\varnothing$ mm	-	-
	41 MHz [153]	86%	20~22	70~80%	75~78%	-	0.5 × 0.4 mm2	43 μm	226 μm
Using geometrical focusing technique	47 MHz [104]	72%	-	-	-	2.5 mm	0.57 × 0.57 mm2	25 μm	120 μm
	52 MHz [116]	41%	36.7 MRayls	-	-	3 mm	0.5 × 1.0 mm2	-	180 μm
	37 MHz [159]	62%	36.7 MRayls	-	-	3 mm	0.5 × 0.5 mm2	58 μm	211 μm
	52 MHz [157]	107%	-	36%	50%	3 mm	0.6 × 0.6 mm2	80 μm	100 μm