Table 2.
Representative photoacoustic endoscopy systems. FV, forward-viewing; SV, side-viewing; fps, frames per second; λ, wavelength; f-3 dB, -3 dB frequency bandwidth; OR, optical-resolution; AR, acoustic-resolution; L, lateral; A, axial; PA, photoacoustic; US, ultrasound; OCT, optical coherence tomography.
| Reference | View | Modality | Resolution mode | Light source | Ultrasound sensor | Probe diameter (mm) | Resolution (μm) | Imaging speed (fps) | Validation |
|---|---|---|---|---|---|---|---|---|---|
| Shao et al. (2012) [87] | FV | PA + Fluorescence | OR | 532 nm, 160 kHz (GLP-10, IPG Photonics Corporation) | Piezoelectric, Focused, 3.5 MHz | 0.85 | L: ∼7 | 2 | Mouse ear in vivo |
| Papadopoulos et al. (2013) [67] | FV | PA | OR | 532 nm, (NL-201, EKSPLA) | Piezoelectric, Focused,20 MHz |
0.22 | L: 1.5 | – | Nylon wire phantom |
| Stasio et al. (2015) [90] | FV | PA + fluorescence | OR | 532 nm, 200 Hz (NL-201, EKSPLA, Lithuania) | Piezoelectric, Focused,20 MHz |
0.33 | L: 8 | – | Nylon thread phantom |
| Ansari et al. (2018) [66] | FV | PA | AR | 410 - 2100 nm, 30 Hz (Innolas Spitlight 600) | Fabry-Perot resonator, f-3dB = 34 MHz, λ/4 resonance at 21 MHz, λ/2 minimum at 67 MHz |
3.2 | L: 31, A: 45-170 |
– | Duck embryo + Mouse skin ex vivo |
| Caravaca-Aguirre et al. (2018) [92] | FV | PA + fluorescence | OR | 532 nm, 7 kHz (Cobolt TorTM series) | Fabry-Perot resonator, 250 kHz - 50 MHz | 0.25 | – | – | Red blood cells + Absorbing micro-structure |
| Jansen et al. (2011) [56] | SV | PA + US | AR | 715 - 1800 nm, 10 Hz (OPOTEK Vibrant B/ 355-II) | Piezoelectric, Unfocused, 30 MHz |
1.25 | – | – | Human coronary ex vivo |
| Karpiouk et al. (2012) [127] | SV | PA + US | AR | 1064 nm, 20 Hz (Polaris II, New Wave, Inc.) | Piezoelectric, Unfocused, 40 MHz |
2.2 | – | – | Rabit artery + Stent in vivo |
| Yang et al. (2012) [57] | SV | PA + US | AR | 562 nm + 584 nm/523 nm + 640 nm, (Cobra HRR, Sirah, INNOSLAB IS811-E, EdgeWave) | Piezoelectric, Focused,36 MHz |
3.8 | – | 4 | Rabbit esophagus + Rat colon in vivo |
| Dong et al. (2014) [109] | SV | PA | OR | 532 nm (TLB-6712, New Focus) | Micro-ring resonator, 5 MHz − 1 GHz |
4.5 | L: 4.5 A: 16 |
– | Plastic tube phantom |
| Abran et al. (2014) [117] | SV | PA + US + Fluorescence | AR | 710 nm, 20 Hz (Quanta-Ray INDI series, Newport Corporation) | Piezoelectric, Unfocused, 45 MHz |
1.4 | – | – | Blood-mimicking phantom |
| Li et al. (2015) [101] | SV | PA + US | AR | 1185-1235 nm, 1 kHz (EKSPLA, NT242) | Piezoelectric (Lead zirconate titanate composite), Unfocused, 40 MHz |
0.9 | L: ∼ 180 A: ∼ 100 |
5 | Stent + Porcine aorta ex vivo |
| VanderLaan et al. (2016) [128] | SV | PA + US | AR | 1064 nm, 10 kHz (SOL40W-1064, RPMC Lasers, Inc.) | Piezoelectric, Unfocused, 40 MHz |
1 | – | 33 | Stent phantom |
| He et al. (2016) [105] | SV | PA | OR + AR | 532 nm, 2 kHz (Wedge HB532, BrightSolutions SRL) | Piezoelectric, Unfocused, 20 MHz |
3.6 | L: 13 (OR) ∼250 (AR) |
– | Mouse ear ex vivo |
| Dai et al. (2017) [116] | SV | PA + US + OCT | OR | 710 - 1210 nm, 20 Hz | Piezoelectric, Unfocused, 40 MHz |
1 | – | – | Mouse ear + Human hand in vivo + human arteries ex vivo |
| Wu et al. (2017) [126] | SV | PA + US | AR | 1700 - 1750 nm, 5 kHz (FQ-OPO, Elforlight Ltd) | Piezoelectric, Unfocused, 40 MHz |
1.3 | – | 20 | Swine coronary arteries in vivo + Human coronary artery ex vivo |
| Hui et al. (2017) [104] | SV | PA + US | AR | 1700 nm, 2 kHz | Piezoelectric, Unfocused, 40 MHz |
1 | L: 305 | 16 | Human coronary artery ex vivo |
| Mathews et al. (2018) [111] | SV | PA + OCT | OR | 560 - 610 nm, 2.8 kHz (Elforlight) | Fabry-Perot resonator, −6 dB bandwidth: 3–30 MHz |
1.25 | L: 18 - 40 A: ∼45 |
– | Stent + Vascular phantom |
| Liu et al. (2018) [118] | SV | PA + Hyperspectral | OR | 532 nm, 10 kHz (Model DTL-314QT) | Piezoelectric, Focused,10 MHz |
12 | L: 40 A: 60 |
– | Rabbit rectum in vivo |
| Li et al. (2019) [131] | SV | PA + US | AR | 532 nm, 300 kHz (DCH-532-10, Photonics Industries International Inc.) | Piezoelectric, Unfocused, 45 MHz |
1 | L :250 A: 50 | 50 | Rat rectum in vivo |