SignificanceX-ray imaging is frequently used for gastrointestinal imaging. Photoacoustic imaging (PAI) of the gastrointestinal tract is an emerging approach that has been demonstrated for preclinical imaging of small animals. A contrast agent active in both modalities could be useful for imaging applications.AimWe aimed to develop a dual-modality contrast agent comprising an admixture of barium sulfate with pigments that absorb light in the second near-infrared region (NIR-II), for preclinical imaging with both x-ray and PAI modalities.ApproachEleven different NIR-II dyes were evaluated after admixture with a 40% w/v barium sulfate mixture. The resulting NIR-II absorption in the soluble fraction and in the total mixture was characterized. Proof-of-principle imaging studies in mice were carried out.ResultsPigments that produced more uniform suspensions were assessed further for photoacoustic contrast signal at a wavelength of 1064 nm that corresponds to the output of the Nd:YAG laser used. Phantom imaging studies demonstrated that the pigment-barium sulfate mixture generated imaging contrast in both x-ray and PAI modalities. The optimal pigment selected for further study was a cyanine tetrafluoroborate salt. Ex-vivo and whole-body mouse imaging demonstrated that photoacoustic and x-ray contrast signals co-localized in the intestines for both imaging modalities.ConclusionThese data demonstrate that commercially-available NIR-II pigments can simply be admixed with barium sulfate to generate a dual-modality contrast agent appropriate for small animal gastrointestinal imaging.
A unique deep learning network, Deep-E, is proposed, which utilizes 2D training data to solve a 3D problem. The novelty of this simulation method is to generate a 2D matrix in the axial-elevational plane using an arc-shaped transducer element, instead of generating a 3D matrix using the linear transducer arrays. Deep-E exhibited significant resolution improvement on the in vivo human breast data. In addition, we were able to restore deeper vascular structures and remove the noise artifact. We envision that Deep-E will have a significant impact in linear-array-based photoacoustic imaging studies by providing high-speed and high-resolution image enhancement.
We developed the second-generation photoacoustic dual scan mammoscope (DSM) as a safe and effective modality for the breast imaging of patients with high breast density. Besides being a portable system with high resolution, DSM-2 has several improvements compared to the previous version: a larger field of view, better system stability, higher ultrasound imaging quality, and additional quasi-static elastography capability. The performance of the new system was demonstrated through clinical studies. The experiment result confirmed the capability of the second-generation DSM system as a powerful tool for breast imaging.
In this presentation, we introduce the initial patient imaging results of our dual-scan mammoscope system. The goal is to verify whether the system can differentiate malignant and healthy cases. We have imaged 38 patients with various cancer types and compared results of tumor breast with healthy breast for each patient. At 95% confidence level, we found that tumor breasts exhibit higher average photoacoustic signal amplitude, higher vessel signal amplitude, and stronger variation in background signals. We could also visualize different vascular features in and around the tumor region for different subtypes of tumors. Our preliminary results indicate that photoacoustic technology has a high potential for breast imaging.
We have developed a photoacoustics-based imaging system that combines optical contrasts with acoustic detection, to obtain a snapshot of the angiographic features in human breast. The system uses near-infrared (NIR) light at 1064 nm wavelength for excitation and hemoglobin in blood as endogenous contrast agent. The light source is a 10 ns Nd:YAG laser with 10-Hz pulse repetition rate. Tumor-angiogenesis, the increase in neovasculature in rapidly growing tumors, is a known biomarker for malignancy. By mapping total hemoglobin levels, we are able to pinpoint the tumor location based on vessel density. For acoustic detection, two 128-element linear-array transducers with 2.25 MHz central frequency are employed. Photoacoustic data is acquired by scanning the breast mildly compressed in the craniocaudal plane, similar to a mammogram, with a scan time of less than 1 minute. The system simultaneously acquires ultrasound (US) data, which can be correlated easily with the photoacoustic data obtained as well as clinical ultrasound images. The photoacoustic images can also be correlated with maximum intensity projection (MIP) subtraction images of contrast MRI (magnetic resonance imaging) 6 minutes post-injection of Gadolinium, and the same vessels could be identified. With our dual transducer geometry, we are able to visualize through 7 cm of breast tissue, a first in this field. The resolution was measured to be 0.97 mm in lateral and 1.05 mm in elevational directions. Our system offers high spatial resolution, fast imaging capability, and convenient correlation with all existing imaging modalities, along with better sensitivity towards dense breast tissue.
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