ICG enhanced co-registered diffuse optical tomography and photoacoustic tomography

Abstract

Chen Xu, Patrick D. Kumavor, Yan Xu, and Quing Zhu Electrical and Computer Engineering Department, Uni versity of Connecticut, 371 Fairfield Road, Unit 2157, Storrs, CT 06269-215 7 Tel: (860) 486-3344; Fax: (860) 486-2447; E-mail: cxu@engr.uconn.edu Abstract: To overcome the intensive light scattering in the b iological tissue, diffuse optical tomography (DOT) in the near infrared range for breast lesion detection usually is combined with other imaging modalities such as ultrasound, X-ray, and M RI, to provide guidance. However, the guided imaging modalities may depend on different c ontrast mechanics compared to the optical contrast in the DOT. As a result, they can’t provid e reliable guidance for diffuse optical tomography because some lesions may not be detectab le by a non-optical modality but yet have high optical contrast. An imaging modality which ca n provide the guidance from optical contrast is desirable for DOT. In this paper, we pr esent a system that combines diffuse optical tomography and photoacoustic tomography (PAT), to d etect and characterize the deeply-seated targets embedded in a turbid medium. Photoacoustic tomography utilizes a short-pulsed laser beam to penetrate into tissue diffusively. Upon absorption of the light by the target, photoacoustic waves are generated and used to recon struct, at ultrasound resolution, the optical absorption distribution that reveals optical contra st. The combined system used in the experiment combines a 64-channel photoacoustic syst em with a frequency-domain diffused optical system. To further improve the contrast, th e exogenous contrast agent, indocyanine green (ICG) is used. Our experiment results show th at the combined system can detect a tumor-mimicking phantom up to 2.5 cm in depth and 10 µM i n concentration. Mice experiments also confirmed that the combined system can detect the t umor region and monitor the ICG uptake and washout in the tumor region. This method can po tentially improve the accuracy to detect the small breast lesions or any lesions which are s ensitive to the reference change, such as the lesions located on the chest wall. Keywords: Diffuse optical tomography , Photoacoustic tomography, absorption coefficient, exogenous contrast agent 1. Introduction Diffuse optical tomography (DOT) in the near infrar ed spectrum (NIR) provides a unique approach for functional diagnostic imaging, which can detect endogenous absorbers, such as the tumor hemoglobin concentration and oxygen saturatio n.