Development of a compact laser-diode based frequency domain photoacoustic sensing system: Application of human breast cancer diagnosis.

We present the development of a laser diode based photoacoustic spectral response (PASR) setup capable of diagnosing human breast cancer tissues through the use of mechanobiological properties of the tissue. A detailed description of the laser driver is provided, highlighting the important characteristics of the developed driver. Furthermore, the amplifier development is described. The developed laser diode based PASR system has been characterized using standard samples. Subsequently, the developed experiment has been applied onto diagnosis of human breast tumors. Energy has been used as a parameter to differentiate between normal and malignant tissues. The results were statistically consistent and then compared with standard histopathology for correlation.

Application of continuous-wave photoacoustic sensing to red blood cell morphology.

The feasibility of continuous wave laser-based photoacoustic (CWPA) response technique in detecting the morphological changes in cells during the biological studies, through the features extracted from CWPA signal (i.e., amplitude) is demonstrated here. Various hematological disorders (e.g., sickle cell anemia, thalesemia) produce distinct changes at the cellular level morphologically. In order to explore the photoacoustic response technique to detect these morphological changes, we have applied CWPA technique onto the blood samples. Results of our preliminary study show a distinct change in the signal amplitude of photoacoustic (PA) signal due to a change in the concentration of blood, which signifies the sensitivity of the technique towards red blood cell (RBC) count (related to hematological disease like anemia). Further hypotonic and hypertonic solutions were induced in blood to produce morphological changes in RBCs (i.e., swollen and shrink, respectively) as compared to the normal RBCs. Experiments were performed using continuous wave laser-based photoacoustic response technique to verify the morphological changes in these RBCs. A distinct change in the PA signal amplitude was found for the distinct nature of RBCs (swollen, shrink, and normal). Thus, this can serve as a diagnostic signature for different biological studies based on morphological changes at cellular level. The experiments were also performed using conventional pulsed laser photoacoustic response technique which uses nano-second pulsed laser and the results obtained from both PA techniques were validated to produce identical changes. This demonstrates the utility of continuous wave laser-based photoacoustic technique for different biological studies related to morphological cellular disorders.