Disclosure: UC Davis has a research agreement and a sales-based revenue sharing agreement with United Imaging Healthcare. No other potential conflicts of interest relevant to this article exist including employment, royalties, stock options, or patents.

This article and updated information are available at: http://jnm.snmjournals.org/site/subscriptions/online.xhtml Information about subscriptions to JNM can be found at: http://jnm.snmjournals.org/site/misc/permission.xhtml

To improve the lateral resolution of the blood vessels along arbitrary direction out of focus in photoacoustic microscopy (PAM), we propose an adaptive synthetic-aperture focusing technique (ASAFT) for microvasculature imaging which can be automatically applied to each branch of blood vessels, based on our previous two-dimensional (2D) SAFT. The ASAFT is validated both in the phantom study and in vivo imaging. The results demonstrate that ASAFT can provide images of blood vessels with better lateral resolution both at different depths and along various directions compared with one-dimensional and 2D SAFT.

Purpose: The aim of the study was to explore a fast PET scan protocol of the total-body uEXPLORER scanner by assessing the image quality consistent to that of a conventional digital PET/CT scanner both from the phantom and clinical perspectives.Methods: The phantom study using a NEMA/IEC NU-2 body phantom was performed both on a totalbody PET/CT (uEXPLORER) and a digital routine PET/CT (uMI 780), with hot sphere to background activity concentration ratio of 4:1. The contrast recovery coe cient (CRC), background variability (BV), recovery coe cient RCmax and RCmean were assessed and compared between that in uEXPLORER with the different scanning duration and reconstruction protocols and that in uMI 780 with clinical settings.The coe cient of variation (COV) of the uMI 780 with clinical settings were calculated and used as a threshold to determine the optimized scanning duration and reconstruction protocols were, which can provide a consistent image quality for the two scanners. And subsequently, the proposed protocol was validated by 30 oncological patients. Images acquired in uMI 780 with a 2-3 minute for each bed position were referred as G780. All PET raw data were reconstructed using data-cutting technique to simulate a 30s, 45s or 60s acquisition duration on uEXPLORER. The iterations were 2 and 3 for uEXPLORER, referred as G30s_3i, G45s_2i, G45s_3i, G60s_2i, and G60s_3i. A 5-point Likert scale was used in the qualitative analysis to assess the image quality. The image quality was also compared with the liver COV, the lesion target-to-background ratio (TBR), and the lesion signal-to-noise ratio (SNR).Results: In the phantom study, CRC, BV, RCmax and RCmean in uEXPLORER with different scanning duration and reconstruction iterations were compared with that in uMI 780 with clinical settings and a minor uctuation was found among different scanning durations. COV of the uMI 780 with clinical settings was 11.6% and determined protocol with a 30-45s scanning duration and 2 or 3 iterations to provide a similar image quality.In the quantitative analysis on the clinical images, there was no signi cant difference between G780 and G45s_3i. All the other groups in uEXPLORER with a 45s-and above acquisition showed a signi cantly improved image quality than that in uMI 780 with clinical settings. Comparing the liver COV, there was no signi cantly difference between G780 and G30s_3i. And no signi cant difference in lesion TBR was identi ed between G780 and G45s_2i, while uEXPLORER had a better performance in lesion SNR compared to that in uMI 780 with clinical settings.Conclusions: This study demonstrated a fast PET protocol with a 30-45s acquisition in uEXPLORER with consistent image quality to that in uMI 780 with clinical settings.

Angiogenesis plays an important role in tumor growth and expansion, which makes it one of the most critical subjects in oncologic research. Angiogenesis can be imaged with photoacoustic microscopy (PAM), however the lateral resolution deteriorates significantly out of focus. Virtual-point-detector-based synthetic aperture focusing technique (SAFT) combined with the coherence weighting factor (CF) can alleviate the blurring, at a cost of anisotropy of resolution. In this study, a two-dimensional SAFT with CF was investigated to improve resolution and yield lateral resolution isotropy simultaneously. In a phantom study, two carbon fibers with a diameter of 6 μm fixed perpendicularly to each other were imaged with PAM developed in our laboratory. In the depth range of 0.6 mm near the focal spot, the best resolution processed with one-dimensional (1D) SAFT is 40 μm better than that processed with two-dimensional (2D) SAFT. However, the maximum difference in lateral resolution between the z-x and z-y planes is about 15 μm processed with 2D SAFT, while it is 145 μm processed with 1D SAFT. Furthermore, the 2D SAFT increased the signal-to-noise ratio (SNR) by up to 8 dB higher than 1D SAFT at an imaging depth of 700 μm below the focal spot. Finally, in vivo imaging of the dorsal subcutaneous microvasculature of a mouse was used to validate the improved performance of 2D SAFT.