A fast 512-element ring array photoacoustic imaging system for small animals

A 512-element photoacoustic tomography system for small animal imaging using a ring ultrasound array has been developed. The system features a 5 MHz piezocomposite transducer array formed into a complete circular aperture. Custom receiver electronics consisting of dedicated preamplifiers, 8:1 multiplexed post-amplifiers, and a 64-channel data acquisition module provide full tomographic imaging at up to 8 frames/second. We present details of the system design along with characterization results of the resolution, imaging volume, and sensitivity. Small animal imaging performance is demonstrated through images of mice brain vasculature at different depths and real-time spectroscopic scans. This system enables real-time tomographic imaging for functional photoacoustic studies for the first time

A real-time photoacoustic tomography system for small animals

A real-time 512-element photoacoustic tomography system for small animal imaging using a ring ultrasound array has been developed. The system, based upon a 5 MHz transducer array formed along a 50 mm circular aperture, achieves sub-200 micron lateral resolution over a 2 cm disk-shaped region. Corresponding elevation resolutions of 0.6 to 2.5 mm over the central volume enable depth-resolved 3D tomographic imaging with linear translation. Using 8:1 electronic multiplexing, imaging at up to 8 frame/sec is demonstrated for both dynamic phantoms and in vivo mouse and brain samples. The real-time, full 2D tomographic capability of the system paves the way for functional photoacoustic tomographic imaging studies in small animals with sub-second time frame

Sub-millimeter nuclear medical imaging with high sensitivity in positron emission tomography using beta-gamma coincidences

We present a nuclear medical imaging technique, employing triple-gamma trajectory intersections from beta^+ - gamma coincidences, able to reach sub-millimeter spatial resolution in 3 dimensions with a reduced requirement of reconstructed intersections per voxel compared to a conventional PET reconstruction analysis. This '$\gamma$-PET' technique draws on specific beta^+ - decaying isotopes, simultaneously emitting an additional photon. Exploiting the triple coincidence between the positron annihilation and the third photon, it is possible to separate the reconstructed 'true' events from background. In order to characterize this technique, Monte-Carlo simulations and image reconstructions have been performed. The achievable spatial resolution has been found to reach ca. 0.4 mm (FWHM) in each direction for the visualization of a 22Na point source. Only 40 intersections are sufficient for a reliable sub-millimeter image reconstruction of a point source embedded in a scattering volume of water inside a voxel volume of about 1 mm^3 ('high-resolution mode'). Moreover, starting with an injected activity of 400 MBq for ^76Br, the same number of only about 40 reconstructed intersections are needed in case of a larger voxel volume of 2 x 2 x 3~mm^3 ('high-sensitivity mode'). Requiring such a low number of reconstructed events significantly reduces the required acquisition time for image reconstruction (in the above case to about 140 s) and thus may open up the perspective for a quasi real-time imaging.Comment: 17 pages, 5 figutes, 3 table

Arms down cone beam CT hepatic angiography: are we focusing on the wrong target?

We read with great interest the recent article by Dr. Gonzalez-Aguirre and colleagues entitled ‘‘Arms Down Cone Beam CT Hepatic Angiography Performance Assessment: Vascular Imaging Quality and Imaging Artefacts’’ [1]. One of the most important advantages of cone beam CT (CBCT) is the possibility to evaluate the lesion’s feeders assisting their identification and catheterization [2]. In this set, the patient’s arms positioning is crucial in order not to impair CBCT imaging. Dr. Gonzalez-Aguirre et al. had elegantly demonstrated that vessels’ visualization is independent from the patient’s arms position, allowing to perform the entire procedure without patient’s movements. This minimizes the risk of contamination and reduces procedural time. However, literature shows that the major pivotal strength of CBCT, either mono-phasic or possibly bi-phasic, is the ability to depict in intra-procedurally ‘‘occult lesions’’, not visible at pre-procedural second-line non-invasive imaging (MRI, MDCT) [3]. This ability is not just for show, but yield to some major clinical implications: the visualization of an occult nodule identifies a subset of population experiencing fast tumour growth, having consequences on the number of adjunctive treatments controlling tumour growth (adjunctive RFA, or TACE procedures) and prioritization for transplantation [4]. Moreover, bi-phasic CBCT, with its unique ability to intra-procedural permit nodule characterization, could help in patients’ reclassification and real-time TACE strategy modification [5]. In this light would be a crucial interest for the audience to know whether the CBCT acquisition with arms down does not alter the diagnostic performance of the modality and ability of lesion’s characterization, especially for those lesion localized peripherally, where the beam hardening artefacts have been shown to be significant. Finally, patient’s positioning is fundamental for CBCT imaging. By acquiring the scan with patient’s arm down, liver volume would not be located within the rotation isocentre. This could be a substantial limitation for lesion located within the left liver lobe, eventually hypertrophied, and for high BMI patients

A fast 512-element ring array photoacoustic imaging system for small animals

A 512-element photoacoustic tomography system for small animal imaging using a ring ultrasound array has been developed. The system features a 5 MHz piezocomposite transducer array formed into a complete circular aperture. Custom receiver electronics consisting of dedicated preamplifiers, 8:1 multiplexed post-amplifiers, and a 64-channel data acquisition module provide full tomographic imaging at up to 8 frames/second. We present details of the system design along with characterization results of the resolution, imaging volume, and sensitivity. Small animal imaging performance is demonstrated through images of mice brain vasculature at different depths and real-time spectroscopic scans. This system enables real-time tomographic imaging for functional photoacoustic studies for the first time

A real-time photoacoustic tomography system for small animals

A real-time 512-element photoacoustic tomography system for small animal imaging using a ring ultrasound array has been developed. The system, based upon a 5 MHz transducer array formed along a 50 mm circular aperture, achieves sub-200 micron lateral resolution over a 2 cm disk-shaped region. Corresponding elevation resolutions of 0.6 to 2.5 mm over the central volume enable depth-resolved 3D tomographic imaging with linear translation. Using 8:1 electronic multiplexing, imaging at up to 8 frame/sec is demonstrated for both dynamic phantoms and in vivo mouse and brain samples. The real-time, full 2D tomographic capability of the system paves the way for functional photoacoustic tomographic imaging studies in small animals with sub-second time frame

Real-time intraoperative 4D full-range FD-OCT based on the dual graphics processing units architecture for microsurgery guidance

Real-time 4D full-range complex-conjugate-free Fourier-domain optical coherence tomography (FD-OCT) is implemented using a dual graphics processing units (dual-GPUs) architecture. One GPU is dedicated to the FD-OCT data processing while the second one is used for the volume rendering and display. GPU accelerated non-uniform fast Fourier transform (NUFFT) is also implemented to suppress the side lobes of the point spread function to improve the image quality. Using a 128,000 A-scan/second OCT spectrometer, we obtained 5 volumes/second real-time full-range 3D OCT imaging. A complete micro-manipulation of a phantom using a microsurgical tool is monitored by multiple volume renderings of the same 3D date set with different view angles. Compared to the conventional surgical microscope, this technology would provide the surgeons a more comprehensive spatial view of the microsurgical site and could serve as an effective intraoperative guidance tool

Potentials and limitations of real-time elastography for prostate cancer detection: a whole-mount step section analysis.

OBJECTIVES: To evaluate prostate cancer (PCa) detection rates of real-time elastography (RTE) in dependence of tumor size, tumor volume, localization and histological type. MATERIALS AND METHODS: Thirdy-nine patients with biopsy proven PCa underwent RTE before radical prostatectomy (RPE) to assess prostate tissue elasticity, and hard lesions were considered suspicious for PCa. After RPE, the prostates were prepared as whole-mount step sections and were compared with imaging findings for analyzing PCa detection rates. RESULTS: RTE detected 6/62 cancer lesions with a maximum diameter of 0-5 mm (9.7%), 10/37 with a maximum diameter of 6-10 mm (27%), 24/34 with a maximum diameter of 11-20 20 mm (70.6%), 14/14 with a maximum diameter of \u3e20 mm (100%) and 40/48 with a volume ≥0.2 cm(3) (83.3%). Regarding cancer lesions with a volume ≥ 0.2 cm³ there was a significant difference in PCa detection rates between Gleason scores with predominant Gleason pattern 3 compared to those with predominant Gleason pattern 4 or 5 (75% versus 100%; P = 0.028). CONCLUSIONS: RTE is able to detect PCa of significant tumor volume and of predominant Gleason pattern 4 or 5 with high confidence, but is of limited value in the detection of small cancer lesions

Free Breathing Real-Time Cardiac Cine Imaging With Improved Spatial Resolution at 3 T

Objectives: The aim of this study was to evaluate free-breathing single-shot real-time cine imaging for functional cardiac imaging at 3 +/- with increased spatial resolution. Special emphasis of this study was placed on the influence of parallel imaging techniques. Materials and Methods: Gradient echo phantom images were acquired with GRAPPA and modified SENSE reconstruction using both integrated and separate reference scans as well as TGRAPPA and TSENSE. In vivo measurements were performed for GRAPPA reconstruction with an integrated and a separate reference scan, as well as TGRAPPA using balanced steady-state free precession protocols. Three clinical protocols, rtLRInt (T-res = 51.3 milliseconds; voxel, 2.5 x 5.0 x 10 mm(3)), rtMRSep (T-res = 48.8 milliseconds; voxel, 1.9 x 3.1 x 10 mm(3)), and rtHRSep ((Tres) = 48.3 milliseconds; voxel, 1.6 x 2.6 x 10 mm(3)), were investigated on 20 volunteers using GRAPPA reconstruction with internal as well as separate reference scans. End-diastolic volume, end-systolic volume, ejection fraction, peak ejection rate, peak filling rate, and myocardial mass were evaluated for the left ventricle and compared with an electrocardiogram-triggered segmented readout cine protocol used as standard of reference. All studies were performed at 3 T. Results: Phantom and in vivo data demonstrate that the combination of GRAPPA reconstruction with a separate reference scan provides an optimal compromise of image quality as well as spatial and temporal resolution. Functional values (P values) for the standard of reference, rtLRInt, rtMRSep, and rtHRSep end-diastolic volume were 141 +/- 24 mL, 138 +/- 21 mL, 138 +/- 19 mL, and 128 +/- 33 mL, respectively (P = 0.7, 0.7, 0.4); end-systolic volume, 55 +/- 15 mL, 61 +/- 14 mL, 58 +/- 12 mL, and 55 +/- 20 mL, respectively (P = 0.23, 0.43, 0.62); ejection fraction, 61% +/- 5%, 57% +/- 5%, 58% +/- 4%, and 56% +/- 8%, respectively (P = 0.01, 0.11, 0.06); peak ejection rate, 481 +/- 73 mL/s, 425 +/- 62 mL/s, 434 +/- 67 mL/s, and 381 +/- 86 mL/s, respectively (P = 0.03, 0.04, 0.01); peak filling rate, 555 +/- 80 mL/s, 480 +/- 70 mL/s, 500 +/- 70 mL/s, and 438 +/- 108 mL/s, respectively (P = 0.007, 0.05, 0.004); and myocardial mass, 137 +/- 26 g, 141 T 25 g, 141 +/- 23 g, and 130 +/- 31 g, respectively (P = 0.62, 0.54, 0.99). Conclusions: Using a separate reference scan and high acceleration factors up to R = 6, single-shot real-time cardiac imaging offers adequate temporal and spatial resolution for accurate assessment of global left ventricular function in free breathing with short examination times