Development of a cost-effective compact diode-laser-based photoacoustic sensing instrument for breast tissue diagnosis

Abstract

Significance: The photoacoustic (PA) technique, a noninvasive pump-probe technique, has found interesting applications in biomedical tissue diagnosis over the last decade. To take it a step further to clinical applications, the PA technique needs to be designed as an instrument focusing on a compact design, reducing the cost, and quickly providing a quantitative diagnosis.

Aim: This work presents a design and characterization of a cost-effective, compact PA sensing instrument for biomedical tissue diagnosis.

Approach: A compact laser diode case design is developed to house several laser diodes for PA excitation, and a pulsed current supply unit is also developed in-house to power the laser diodes to generate a 25 ns current pulse at a frequency of 20 kHz. After PA experimental data acquisition, the signal's frequency spectra were calculated to characterize the tissue quantitatively and correlated with their mechanobiological properties.

Results: The corresponding dominant frequency peak in the PA spectral response (PASR) study was low in the fibrofatty normal breast tissue $0.26\pm 0.03\mathrm{MHz}$, compared to the dominant frequency peak of $1.60\pm 0.016\mathrm{MHz}$ in the fibrocystic disease tissue, which had increased glandular and stromal elements, thereby increased tissue density. The histopathological findings correlated with the PASR results, and the fibrocystic breast disease tissue exhibited a higher dominant frequency peak and energy compared to the normal breast tissue.

Conclusions: We experimented with an in vitro PASR study of fibrocystic human breast tissues and successfully differentiated different tissue types using quantitative spectral parameters peak frequency, mean frequency, and spectral energy. This gives the potential to take this technique further for cost-effective and quick clinical applications.

Keywords: breast tissue diagnosis; diode laser; optical casing; photoacoustic sensing; quantitative information; spectral response.

Fig. 1

Proposed PLD-PASR-based sensing instrument and schematic design of a novel optical casing for multiple laser diodes: (a) side view, (b) transparent side view with internal assembly, (c) laser diode holder with lens assembly, (d) bottom view of the optical casing, and (e) detailed side view of laser propagation. LD, laser diode.

Fig. 2

(a) Schematic design of the pulsed current supply for laser diodes. (b) Pulsed current output from the driver circuit.

Fig. 3

(a) Intensity measurement of the diode laser system using: (i) one, (ii) three, and (iii) five laser diodes. (b) Pulsed laser intensity measurement. (c) Peak amplitude of laser intensity of laser diodes output.

Fig. 4

(a) Experimental setup with the casing-based PA sensing instrument. (b) Time-domain PA signal with multiple numbers of laser diodes, correlation between developed pulsed diode laser and conventional Nd:YAG laser. (c) Time-domain PA signal of a black rubber sample and (d) its spectral response.

Fig. 5

(a) Concentration of agarose gel versus the PF obtained from PASR. (b) Characterization of the agarose sample concentration using spectral parameters.

Fig. 6

PASR response of (a) fibrocystic breast disease tissue and (b) normal breast tissue sample.

Fig. 7

PASR spectral parameters for fibrocystic breast disease tissue and normal breast tissue (a) PF and (b) MF.

Fig. 8

(a) Fibrocystic change in breast showing extensive stromal fibrosis (block arrow). (b) Cystic dilatation of ducts and acini (notched arrow). (c) Adenosis showing enlarged lobule with increased number of glands. (d) Mild epitheliosis of the acini showing increased cellularity (chevron). (e) Normal breast tissue with abundant fatty stroma (arrow), and terminal ductal lobular units (elbow connector arrow). (f) Normal terminal ductal lobular unit in breast parenchyma (encircled).