Quantitative photoacoustic elastography of Young’s modulus in humans

Abstract

Elastography can noninvasively map the elasticity distribution of biological tissue, which is often altered in pathological states. In this work, we report quantitative photoacoustic elastography (QPAE), capable of measuring Young's modulus of human tissue in vivo. By combining photoacoustic elastography with a stress sensor having known stress-strain behavior, QPAE can simultaneously measure strain and stress, from which Young's modulus is calculated. We first applied QPAE to quantify the Young's modulus of tissue-mimicking agar phantoms with different concentrations. The measured values fitted well with both the empirical expectations based on the agar concentrations and those measured in independent standard compression tests. We then demonstrated the feasibility of QPAE by measuring the Young's modulus of human skeletal muscle in vivo. The data showed a linear relationship between muscle stiffness and loading. The results proved that QPAE can noninvasively quantify the absolute elasticity of biological tissue, thus enabling longitudinal imaging of tissue elasticity. QPAE can be exploited for both preclinical biomechanics studies and clinical applications.

Photoacoustic elastography imaging: a review

“…[76][77][78][79][80][81][82][83] Recently, research studies were reported for possible recovery of the elastic property of soft biological tissue with PA imaging technology. [84][85][86][87][88][89][90][91][92] This innovative study enhances the horizon of potential applications of PA imaging extending to diagnosis and therapeutic treatment of life-threatening diseases (such as breast and prostate cancer, 4 brain tumor, 93 and Alzheimer's diseases 94 ) that induce contrast in elasticity relative to normal tissues. Currently, PA elastography (PAE) imaging is limited only to qualitative study, and it is in the nurture stage of development.…”

“…Shear wave-based PA imaging modality was reported for quantitative recovery of mechanical properties of soft tissues both elasticity and viscosity-measuring rise-time of thermoelastic displacement and biomedical application of the approach-were validated in ex-vivo studies for liver cirrhosis detection. 90 Pengfei et al 91 developed PA tomography system for imaging elasticity (Young's modulus) through the study of dynamics of microparticle embedded in sample material while the same group reported their study on characterization of blood vessel elasticity for end application targeted to acute myocardial infarction and stroke, and human skeleton muscle. 92…”

“…Pengfei et al 62,91,92 developed a PAT imaging system-that they called quantitative photoacoustic elastography (QPAE) imaging system-for recovery of tissue elastic property noninvasively and nondestructively. Validation studies were carried out both in tissue-mimicking phantom (gelatin) and animal model (mouse).…”

Young’s moduli of subcutaneous tissues and muscles under different loads at the gluteal region calculated using ultrasonography

“…More recent attempts have focused on tomographic imaging technologies as a means to measure hardness separately in different body tissues [17][18][19][20][21][22][23][24][25][26][27][28][29][30] . For example, Uffmann et al used magnetic resonance elastography to measure the shear moduli of the biceps brachii, flexor digitorum profundus, soleus, and gastrocnemius 21) , while Chino et al tested the reliability and validity of ultrasound elastography in quantifying the hardness of the human medial gastrocnemius 24) .…”

Dynamic X-ray elastography using a pulsed photocathode source

“…Both magnetic resonance (MR) and ultrasound (US) elastography have rapidly expanded into clinical practice and have been used for liver and breast diseases, respectively 11 – 13 . In recent years, elastography studies have also been reported in optical coherence tomography 14 , 15 and photoacoustic imaging 16 , 17 .…”