Traditional diagnostic techniques including visual examination, ultrasound (US), and magnetic resonance imaging (MRI) have limitations of in-depth information for the detection of nail disorders, resolution, and practicality. This pilot study, for the first time, evaluates a dual-modality imaging system that combines photoacoustic tomography (PAT) with the US for the multiparametric quantitative assessment of human nail. The study involved a small cohort of five healthy volunteers who underwent PAT/US imaging for acquiring the nail unit data. The PAT/US dual-modality imaging successfully revealed the fine anatomical structures and microvascular distribution within the nail and nail bed. Moreover, this system utilized multispectral PAT to analyze functional tissue parameters, including oxygenated hemoglobin, deoxyhemoglobin, oxygen saturation, and collagen under tourniquet and cold stimulus tests to evaluate changes in the microcirculation of the nail bed. The quantitative analysis of multispectral PAT reconstructed images demonstrated heightened sensitivity in detecting alterations in blood oxygenation levels and collagen content within the nail bed, under simulated different physiological conditions. This pilot study highlights the potential of PAT/US dual-modality imaging as a real-time, noninvasive diagnostic modality for evaluating human nail health and for early detection of nail bed pathologies.

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This study aims to explore the feasibility of fine-needle aspiration biopsy (FNAB) under dual modal photoacoustic tomography(PAT)/ultrasound (US) imaging. A total of 25 patients who have thyroid nodules with thyroid imaging reporting and data system (TIRADS) 3 and 4 (malignant risk <85%) were recruited. The specimens obtained from the PAT/US-guided FNAB were collected for cytology analysis. Cytological diagnoses for the 25 patients were classified in perspective of the Bethesda system for reporting thyroid cytopathology diagnostic category (DC) I: 4%(1/25); DC II: 12% (3/25); DC III: 20% (5/25); DC IV: 8% (2/25); DC V: 32% (8/25); and DC VI: 24% (6/25). The DC I nodule exhibited inadequate cytology and had structural characteristic of predominant calcifications in PAT/US mapping. The DC V-VI nodules showed lower photoacoustic (PA) signals compared to the DC I-IV nodules. Regions with a high PA signal demonstrated a significant number of erythrocytes in FNAB cytology. Moreover, nodules with microcalcifications did not show a significant difference compared to their surroundings in the PA signal, while nodules with macrocalcifications gave higher PA signals compared to their surroundings. The conclusions are as follows: combining US with PAT can evaluate the structure and function of thyroid nodules in vivo. This study demonstrates that dual modal PAT/US imaging has the potential to be an effective clinical tool to guide FNAB of thyroid nodules.

While medical imaging is playing an increasingly important role in understanding and clarifying acupuncture theory in general, it is still challenging to systematically understand the operational mechanisms of acupuncture on the central and peripheral nerve systems using the existing acupuncture imaging tools. Here, we report an application of photoacoustic tomography (PAT) to mapping cerebral hemodynamics response to acupuncture in mice. Huantiao acupoint (GB 30) is selected as the stimulating points in this study. In vivo photoacoustic images of cerebral hemodynamics response to acupuncture are obtained in ten functional regions of a mouse brain. Real-time photoacoustic signal changes in brain cortex and dynamic changes in total hemoglobin (HbT) concentration are tracked at 532 nm. Our results suggest that PAT provides imaging basis on cerebral hemodynamic response to acupuncture, and may have great potential for understanding the operational mechanisms of acupuncture on the central nerve systems.