Implementation of a new scanning method for high-resolution fluorescence tomography using thermo-sensitive fluorescent agents

Abstract

Conventional fluorescence tomography provides images of the distribution of fluorescent agents within highly scattering media, but suffers from poor spatial resolution. Previously, we introduced a new method termed “temperature-modulated fluorescence tomography” (TM-FT) that generates fluorescence images with high spatial resolution. TM-FT first uses focused ultrasound to locate the distribution of temperature-sensitive fluorescence probes. Afterward, this a priori information is utilized to improve the performance of the inverse solver for conventional fluorescence tomography and reveal quantitatively accurate fluorophore concentration maps. However, the disadvantage of this novel method is the long data acquisition time as the ultrasound beam was scanned in a step-and-shoot mode. In this Letter, we present a new, fast scanning method that reduces the imaging time 40 fold. By continuously scanning the ultrasound beam over a 50 mm by 25 mm field-of-view, high-resolution fluorescence images are obtained in less than 29 min, which is critical for in vivo small animal imaging.

Experimental evaluation of the resolution and quantitative accuracy of temperature-modulated fluorescence tomography

“…This binary map is used as functional a priori to constrain the reconstruction algorithm. A more detailed explanation of the focused ultrasound continuous scanning method is described in Nouizi et al [10].…”

“…Accordingly, structural a priori information obtained by an anatomical imaging modality is used to guide and constrain the optical image reconstruction algorithm and has been shown to significantly improve the quantitative accuracy of FT [5–7,9]. Nevertheless, errors can still occur when the structural boundaries provided by the anatomical imaging modality do not exactly coincide with the true fluorescent distribution [10].…”

“…Previously, we evaluated the resolution and quantitative accuracy of TM-FT with simulation studies [16]. Recently, we have also presented a faster and improved scanning method that reduces the data acquisition time drastically [10]. In this approach, the focused ultrasound transducer is moved continuously while the fluorescence signal is monitored as opposed to the slow step- and-shoot approach we had initially employed [12].…”

Newly-Engineered Materials for Bio-Imaging Technology: A Focus on the Hybrid System of Ultrasound and Fluorescence

“…Since the HIFU focus is required to scan the tissue phantom point by point, it takes more than 1 hour for the imaging system to acquire an image of 8 × 8 mm 2 . In 2015, they used the HIFU continuous scanning method to increase the system imaging speed by 40 times without reducing the imaging resolution, see Figure 9 (Nouizi et al, 2015). In the numerical simulation in 2015 and the experimental work in 2017, the same group reconstructed the image of the fluorophore concentration distribution using the fluorescence tomographic image reconstruction algorithm and introduced the USF signal as the constraint condition equation (Lin et al, 2015; Kwong et al, 2017a,b).…”

“…Experiment results for the 100 mm ( x ) × 40 mm ( y ) × 100 mm (z) agarose phantom with a single 3 mm diameter target (Nouizi et al, 2015). (a) True ThermoDot distribution in the optical fiber plane.…”