Medical Imaging Systems, Photoacoustic and Thermoacoustic Imaging, Image Reconstruction, Machine Learning, Medical Image Processing, Contrast Agents, Molecular Imaging, Monte-Carlo Simulation for light-tissue interaction, Biomedical Optics, Biomedical Device Design, Clinical Application areas such as Breast Cancer Imaging, Brain Imaging, Pancreatic Cancer, Diabetes, Treatment Monitoring etc.

In spite of having various medical imaging modalities, such as, X-ray, computed tomography (CT), magnetic resonance imaging (MRI), single-photon emission computed tomography (SPECT), positron emission tomography (PET), ultrasound imaging (US), there is a need for new imaging technologies. Every imaging modality has their advantages and disadvantages. Therefore, scientists are always looking for new imaging modality. Optical imaging is a strong contender. We work on several new hybrid imaging modalities using light and sound.

Photoacoustic and Thermoacoustic Imaging

Acronyms: Photoacoustic (PA), Photoacoustic Imaging (PAI), Photoacoustic Tomography (PAT), Photoacoustic Computed Tomography (PACT), Photoacoustic Microscopy (PAM), Thermoacoustic (TA), Thermoacoustic Tomography (TAT), Thermoacoustic Imaging (TAI), Thermoacoustic Computed Tomography (TACT).

A. G. Bell first reported the observation of sound generated by light in 1880. When a short-pulsed laser irradiates biological tissues, wideband ultrasonic waves (PA waves) are induced as a result of transient thermoelastic expansion. In PAT, a short-pulsed laser irradiates the tissue, and the PA waves are measured by wide-band ultrasound transducers around the tissue. We can use a focused ultrasound transducer to localize the photoacoustic sources and then construct the images directly from the data. Alternatively, we can use an unfocused ultrasound transducer to acquire the data and then reconstruct the optical absorption distribution. Since optical absorption is sensitive to physiological parameters such as the total concentration and oxygenation of hemoglobin, PAT can provide functional imaging. PAT overcomes the limitations of other optical modalities and combines optical contrast with ultrasound resolution. In PAT, the contrast is related to the optical properties of the tissue, but the resolution is not limited by optical diffusion caused by multiple photon scattering. PAT does not depend on ballistic or backscattered light as optical coherence tomography (OCT) does. Any light, including both singly and multiply scattered photons, contributes to the imaging signal. As a result, the imaging depth in PAT is relatively large. Furthermore, PAT is free of speckle artifacts, which plague OCT and ultrasonography. Photoacoustic waves propagate one way to the ultrasonic transducers in PAT, whereas ultrasound propagates two ways in conventional ultrasonography.

In microwave induced thermoacoustic imaging, a short-pulsed microwave source irradiates the tissue instead of a laser pulse. The dominant effect of microwaves on biological tissues is thermal. When electro-magnetic energy is transformed in to kinetic energy in absorbing molecules, heating and subsequent thermoacoustic emission occurs in the medium. Thus the absorbed microwave energy causes emission of thermoacoustic waves from within the irradiated tissue. The dielectric properties of the tissues determine their patterns of energy deposition upon irradiation. The microwave heating must be rapid to produce thermoacoustic waves of sufficiently high frequencies; in other words, a static temperature distribution or slow heating does not produce thermoacoustic waves. A wide-band ultrasonic transducer acquires the thermoacoustic waves, which carry the microwave absorption properties of the tissue. TAT combines the advantages of pure-ultrasound and pure-RF imaging. Traditional imaging technology with pure ultrasound (ultrasonography) offers satisfactory spatial resolution but poor soft-tissue contrast, while pure-RF imaging provides good imaging contrast but poor spatial resolution. TAT bridges the gap between them by physically integrating ultrasound and RF. It provides both satisfactory spatial resolution (0.5 mm) and high soft-tissue contrast.

Research Highlight

[8] April 2023 SPIE News: The first-of-its-kind mobile application developed on Python for photoacoustic image reconstruction...More>>

[7] May 2019 Highlights in Biophotonics World...More>>

[6] February 2019 Highlights in Biophotonics World...More>>

[5] January 2019 Highlights in Biophotonics World...More>>

[4] 2010 Highlights in Science to Practice in Radiology...More>>

[3] November 22, 2010 Physorg.com - See it for yourself: a new breakthrough in imaging technology using a combination of light and sound will allow health care providers to see microscopic details inside the body........More>>

[2] June 11, 2009 MedicalphysicsWeb - Nanotubes reveal breast cancer spread: Sentinel lymph-node biopsy is certainly less drastic than no-questions-asked underarm lymph-node dissection, but it is not without its disadvantages. Node identification typically involves injection of a gamma ray-emitting radiotracer and/or blue dye into the breast........ More>>

[1] June 24, 2008 MedicalPhysicsWeb - TAT/PAT: a new screening option? Information obtained from a new application of photoacoustic tomography (PAT) is worth its weight in gold to breast cancer patients...... More>>

Funding Agencies and Collaborators

We acknowledge the financial support of the following agencies for various current/past projects in BILab.

6. Start Up Grant (2023-2025) [by Iowa State University]

5. NTUitive GAP Fund (2021-2022)

4. Open Fund Individual Research Grant - ORIFG (2016-2019) [by National Medical Research Council (NMRC), Ministry of Health (MOH), Singapore]

3. Academic Research Fund Tier 2 (2015-2019) [by Ministry of Education (MOE), Singapore]

2. Academic Research Fund Tier 1 (2014-2022) [by Ministry of Education (MOE), Singapore]

1. Start Up Grant (2014-2017) [by Nanyang Technological University]

Present and Past Collaborators

22. Yuanjin Zheng, Nanyang Technological University (NTU), Singapore

21. Wolfgang Drexler, Medical University of Vienna, Vienna, Austria

20. Jaya Prakash, Indian Institute of Science, Bangalore, India

19. Soheil Hakakzadeh and Zahra Kavehvash, Sharif University of Technology, Tehran, Iran

18. Junjie Yao, Duke University, USA

17. James J. Kwan, University of Oxford, UK

16. Babak Mohammadzadeh Asl, Tarbiat Modares University, Tehran, Iran

15. Moein Mozaffarzadeh, Delft University of Technology, Netherlands

14. Pu Kanyi, School of Chemical and Biomedical Engineering, Nanyang Technological University, Singapore

13. Phaneendra K. Yalavarthy, Department of Computational and Data Sciences, Indian Institute of Science (IISc), Bangalore, India

12. Leopold Schmetterer, Singapore Eye Research Institute, Singapore

11. Ratan K. Saha, Indian Institute of Information Technology, Allahabad, India

10. Bengang Xing, School of Physical & Mathematical Sciences, Nanyang Technological University, Singapore

9. Nagaiyan Sekar, Institute of Chemical Technology, Mumbai, India

8. Hongwei Duan, School of Chemical and Biomedical Engineering, Nanyang Technological University, Singapore

7. Teoh Swee-Hin, School of Chemical and Biomedical Engineering, Nanyang Technological University, Singapore

6. Wang Mingfeng, School of Chemical and Biomedical Engineering, Nanyang Technological University, Singapore

5. Xu Chenjie, School of Chemical and Biomedical Engineering, Nanyang Technological University, Singapore

4. M. P. Kothiyal, Indian Institute of Technology Madras, Chennai, India

3. K. M. Nandigana, Indian Institute of Technology Madras, Chennai, India

2. Zhe Wu, University of Electronic Science and Technology of China, Chengdu, China

1. Siva Umapathy, Inorganic and Physical Chemistry, Indian Institute of Science (IISc), Bangalore, India