SignificanceTissue phantoms that mimic the optical and radiologic properties of human or animal tissue play an important role in the development, characterization, and evaluation of imaging systems. Phantoms that are easily produced and stable for longitudinal studies are highly desirable.AimA new type of long-lasting phantom was developed with commercially available materials and was assessed for fabrication ease, stability, and optical property control. Magnetic resonance imaging (MRI) and x-ray computed tomography (CT) contrast properties were also evaluated.ApproachA systematic investigation of relationships between concentrations of skin-like pigments and composite optical properties was conducted to realize optical property phantoms in the red and near-infrared (NIR) wavelength range that also offered contrast for CT and MRI.ResultsPhantom fabrication time was <1 h and did not involve any heating or cooling processes. Changes in optical properties were <2 % over a 12-month period. Phantom optical and spectral features were similar to human soft tissue over the red to NIR wavelength ranges. Pigments used in the study also had CT and MRI contrasts for multimodality imaging studies.ConclusionsThe phantoms described here mimic optical properties of soft tissue and are suitable for multimodality imaging studies involving CT or MRI without adding secondary contrast agents.
KEYWORDS: Magnetic resonance imaging, Imaging systems, Interfaces, Signal detection, Data acquisition, Breast cancer, Tomography, Imaging spectroscopy, Multimodal imaging, Near infrared spectroscopy
A novel MRI-guided near-infrared spectroscopic tomographic imaging system (NIRST) has been developed for breast cancer detection. NIRST imaging for an entire breast can be simultaneously carried out during MRI scanning in less than 4 minutes. Reconstructed phantom images showed clear contrast of a 20 mm inclusion to the background, and the total hemoglobin (HbT) and water concentration values estimated from the reconstructed images of a normal subject were in the same range as those obtained in our previous imaging studies.
KEYWORDS: Breast cancer, Multimodal imaging, Tomography, Magnetic resonance imaging, Optical fibers, Data acquisition, Imaging systems, Interfaces, Near infrared spectroscopy
A novel wearable MRg-NIRST system for breast cancer detection has been designed and developed. In this prototype, eight (8) flex circuit strips, each with six (6) photo-detectors (PDs) and six (6) source fibers, are attached to the breast to collect diffused light. A 6x48 fiber switch and 48 side-firing fibers deliver intensity modulated laser light at six (6) near-infrared wavelengths. Light intensity at each of 2304 source-detector positionsis obtained for T2-MRI guided 3D NIRST image reconstruction. In phantom testing, reconstructed images showed the contrast between tumor/inclusion and normal/background.
KEYWORDS: Breast, Magnetic resonance imaging, Tomography, Spectroscopy, Near infrared spectroscopy, Near infrared, Interfaces, Imaging spectroscopy, Light, Imaging systems
A new photo-detector (PD) and source fiber based wearable MRI-guide near infrared spectroscopic tomographic imaging (MRg-NIRST) system has been designed and is underdevelopment. In this new system, eight flex circuit strips, each with 6 PDs and 6 side-firing fibers will be applied to the breast, prior to coil/biopsy positioning. The intensity of the diffused light will be acquired at 48x68 source-detector positions at 12 wavelengths. The 3D optical image reconstruction will be guided through the structural information obtained from T2 MRI and the scattering properties associated with MRI defined breast density.
A new low-cost imaging system has been developed for MRI-guided Near-Infrared Spectral Tomography (MRI-NIRST) for breast cancer detection. In this new system, 8 flexible sensing strips with 4 source fibers and 4 photodetectors will be applied directly to the breast, from nipple towards chest-wall, to cover the entire breast. For each source illumination, data will be collected at 32 detector locations. The feasibility of this new imaging system was demonstrated using 3D simulation breast phantoms that created from real breast MR images. Our results indicated that total hemoglobin in a tumor smaller than 1 mm could be recovered with this system.
A portable, 12-wavelength hybrid frequency domain (FD) and continuous wave (CW) near-infrared spectral tomography (NIRST) system was developed for efficient characterization of breast cancer in a clinical oncology setting. Two sets of three FD and three CW measurements were acquired simultaneously. The imaging time was reduced from 90 to 55 seconds with a new gain adjustment scheme of the optical detector. The study of integrating this system into the workflow of clinical oncology practice is ongoing.
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