Beyond Average: α-Particle Distribution and Dose Heterogeneity in Bone Metastatic Prostate Cancer.

α-particle emitters are emerging as a potent modality for disseminated cancer therapy because of their high linear energy transfer and localized absorbed dose profile. Despite great interest and pharmaceutical development, there is scant information on the distribution of these agents at the scale of the α-particle pathlength. We sought to determine the distribution of clinically approved [Ra]RaCl in bone metastatic castration-resistant prostate cancer at this resolution, for the first time to our knowledge, to inform activity distribution and dose at the near-cell scale.

High-resolution Imaging Using Virtual-Pinhole PET Concept.

Organ-specific PET scanners continues to draw interest for their high-resolution imaging capability that is unmatched by whole-body PET/computed tomography (CT) scanners. The virtual-pinhole PET concept offers new opportunities in PET system design, allowing one to mix and match detectors of different characteristics to achieve the highest performance such as high image resolution, high system sensitivity, and large imaging field-of-view. This novel approach delivers high-resolution PET images previously available only through organ-specific PET scanner while maintaining the imaging field-of-view of a clinical PET/CT scanner to see the entire body.

A virtual-pinhole PET device for improving contrast recovery and enhancing lesion detectability of a one-meter-long PET scanner: a simulation study.

This paper presents a simulation study to demonstrate that the contrast recovery coefficients (CRC) and detectability of small lesions of a one-meter-long positron emission tomography (PET) scanner can be further enhanced by the integration of high resolution virtual-pinhole (VP) PET devices. The scanner under investigation is a Siemens Biograph Vision Quadra which has an axial field-of-view (FOV) of 106 cm. The VP-PET devices contain two high-resolution flat panel detectors, each composed of 2 × 8 detector modules each of which consists of 32 × 64 lutetium-oxyorthosilicate crystals (1.

Positron Emission Tomography (PET) for Molecular Plant Imaging.

Positron emission tomography (PET) is an imaging technology that measures 3D spatial distribution and kinetics of radio-tagged biomolecules in a living subject quantitatively and nondestructively. Commonly used positron-emitting radionuclides include C, N, and O, which are essential elements for plant growth. Combining radiotracer techniques with PET, this in vivo molecular imaging capability offers plant biologists a powerful tool for molecular phenotyping research.

Magnetic Resonance Imaging-Guided Focused Ultrasound-Based Delivery of Radiolabeled Copper Nanoclusters to Diffuse Intrinsic Pontine Glioma.

Diffuse intrinsic pontine glioma (DIPG) is an invasive pediatric brainstem malignancy exclusively in children without effective treatment due to the often-intact blood-brain tumor barrier (BBTB), an impediment to the delivery of therapeutics. Herein, we used focused ultrasound (FUS) to transiently open BBTB and delivered radiolabeled nanoclusters (Cu-CuNCs) to tumors for positron emission tomography (PET) imaging and quantification in a mouse DIPG model. First, we optimized FUS acoustic pressure to open the blood-brain barrier (BBB) for effective delivery of Cu-CuNCs to pons in wildtype mice.

Performance comparison of a dedicated total breast PET system with a clinical whole-body PET system: a simulation study.

This paper presents a novel PET geometry for breast cancer imaging. The scanner consists of a 'stadium' (a rectangle with two semi-circles on opposite sides) shaped ring, along with anterior and posterior panels to provide high sensitivity and high spatial resolution for an imaging field-of-view (FOV) that include both breasts, mediastinum and axilla. We simulated this total-breast PET system using GATE and reconstructed the coincidence events using a GPU-based list-mode image reconstruction implementing maximum likelihood expectation-maximization (ML-EM) algorithm.

Seasonal nitrogen remobilization and the role of auxin transport in poplar trees.

Seasonal nitrogen (N) cycling in Populus, involves bark storage proteins (BSPs) that accumulate in bark phloem parenchyma in the autumn and decline when shoot growth resumes in the spring. Little is known about the contribution of BSPs to growth or the signals regulating N remobilization from BSPs. Knockdown of BSP accumulation via RNAi and N sink manipulations were used to understand how BSP storage influences shoot growth.

Augmented Whole-Body Scanning via Magnifying PET.

A novel technique, called augmented whole-body scanning via magnifying PET (AWSM-PET), that improves the sensitivity and lesion detectability of a PET scanner for whole-body imaging is proposed and evaluated. A Siemens Biograph Vision PET/CT scanner equipped with one or two high-resolution panel-detectors was simulated to study the effectiveness of AWSM-PET technology. The detector panels are located immediately outside the scanner's axial field-of-view (FOV).

A second-generation virtual-pinhole PET device for enhancing contrast recovery and improving lesion detectability of a whole-body PET/CT scanner.

Purpose: We have developed a second-generation virtual-pinhole (VP) positron emission tomography (PET) device that can position a flat-panel PET detector around a patient's body using a robotic arm to enhance the contrast recovery coefficient (CRC) and detectability of lesions in any region-of-interest using a whole-body PET/computed tomography (CT) scanner.

Methods: We constructed a flat-panel VP-PET device using 32 high-resolution detectors, each containing a 4   4 MPPC array and 16   16 LYSO crystals of 1.0   1.

Cherenkov luminescence imaging of shallow sources in semitransparent media.

We experimentally investigated the Cherenkov luminescence imaging (CLI) of the isotopes with different beta particles energies (Cu64, F18, Au198, P32, and Br76) in semitransparent biological equivalent media. The main focus of this work is to characterize the CLI when the sources are at the depth comparable with the range of beta particles. The experimental results were compared with Monte Carlo (MC) simulation results to fine tune the simulation parameters to better model the phantom materials.

Feasibility study of a point-of-care positron emission tomography system with interactive imaging capability.

Purpose: We investigated the feasibility of a novel positron emission tomography (PET) system that provides near real-time feedback to an operator who can interactively scan a patient to optimize image quality. The system should be compact and mobile to support point-of-care (POC) molecular imaging applications. In this study, we present the key technologies required and discuss the potential benefits of such new capability.

Focused ultrasound combined with microbubble-mediated intranasal delivery of gold nanoclusters to the brain.

Focused ultrasound combined with microbubble-mediated intranasal delivery (FUSIN) is a new brain drug delivery technique. FUSIN utilizes the nasal route for direct nose-to-brain drug administration, thereby bypassing the blood-brain barrier (BBB) and minimizing systemic exposure. It also uses FUS-induced microbubble cavitation to enhance transport of intranasally (IN) administered agents to the FUS-targeted brain location.

Focused Ultrasound Enabled Trans-Blood Brain Barrier Delivery of Gold Nanoclusters: Effect of Surface Charges and Quantification Using Positron Emission Tomography.

Focused ultrasound (FUS) technology is reported to enhance the delivery of Cu-integrated ultrasmall gold nanoclusters ( Cu-AuNCs) across the blood-brain barrier (BBB) as measured by positron emission tomography (PET). To better define the optimal physical properties for brain delivery, Cu-AuNCs with different surface charges are synthesized and characterized. In vivo biodistribution studies are performed to compare the individual organ uptake of each type of Cu-AuNCs.

Focused ultrasound-enabled delivery of radiolabeled nanoclusters to the pons.

The goal of this study was to establish the feasibility of integrating focused ultrasound (FUS)-mediated delivery of Cu-integrated gold nanoclusters (Cu-AuNCs) to the pons for in vivo quantification of the nanocluster brain uptake using positron emission tomography (PET) imaging. FUS was targeted at the pons for the blood-brain barrier (BBB) disruption in the presence of systemically injected microbubbles, followed by the intravenous injection of Cu-AuNCs. The spatiotemporal distribution of the Cu-AuNCs in the brain was quantified using in vivo microPET/CT imaging at different time points post injection.

Penetration depth of photons in biological tissues from hyperspectral imaging in shortwave infrared in transmission and reflection geometries.

Measurement of photon penetration in biological tissues is a central theme in optical imaging. A great number of endogenous tissue factors such as absorption, scattering, and anisotropy affect the path of photons in tissue, making it difficult to predict the penetration depth at different wavelengths. Traditional studies evaluating photon penetration at different wavelengths are focused on tissue spectroscopy that does not take into account the heterogeneity within the sample.

A simultaneous beta and coincidence-gamma imaging system for plant leaves.

Positron emitting isotopes, such as (11)C, (13)N, and (18)F, can be used to label molecules. The tracers, such as (11)CO2, are delivered to plants to study their biological processes, particularly metabolism and photosynthesis, which may contribute to the development of plants that have a higher yield of crops and biomass. Measurements and resulting images from PET scanners are not quantitative in young plant structures or in plant leaves due to poor positron annihilation in thin objects.

Biodistribution and Radiation Dosimetry of the Enterobacteriaceae-Specific Imaging Probe [(18)F]Fluorodeoxysorbitol Determined by PET/CT in Healthy Human Volunteers.

Purpose: [(18)F]fluorodeoxysorbitol ([(18)F]FDS) is the first radiopharmaceutical specific for a category of bacteria and has the potential to specifically detect Enterobacteriaceae infections. The purpose of this study was to testify the safety and investigate the biodistribution and radiation dosimetry of [(18)F]FDS in healthy human bodies.

Procedures: Six healthy subjects were intravenously injected with 320-520 MBq [(18)F]FDS.

A generalized reconstruction framework for unconventional PET systems.

Purpose: Quantitative estimation of the radionuclide activity concentration in positron emission tomography (PET) requires precise modeling of PET physics. The authors are focused on designing unconventional PET geometries for specific applications. This work reports the creation of a generalized reconstruction framework, capable of reconstructing tomographic PET data for systems that use right cuboidal detector elements positioned at arbitrary geometry using a regular Cartesian grid of image voxels.

A compact high resolution flat panel PET detector based on the new 4-side buttable MPPC for biomedical applications.

Compact high-resolution panel detectors using virtual pinhole (VP) PET geometry can be inserted into existing clinical or pre-clinical PET systems to improve regional spatial resolution and sensitivity. Here we describe a compact panel PET detector built using the new Though Silicon Via (TSV) multi-pixel photon counters (MPPC) detector. This insert provides high spatial resolution and good timing performance for multiple bio-medical applications.

Cherenkov luminescence imaging in transparent media and the imaging of thin or shallow sources.

In this work, we demonstrated the possibility of high spatial resolution Cherenkov luminescence imaging (CLI) for objects in transparent media. We also demonstrated the possibility of the CLI of thin opaque objects using optical transducers. Results demonstrate that submillimeter resolution CLI is achievable for beta-emitting radionuclides, including ⁷⁶Br that emits positrons of very high energy.

A dedicated high-resolution PET imager for plant sciences.

PET provides an in vivo molecular and functional imaging capability that could be valuable for studying the interaction of plants in changing environments at the whole-plant level. We have developed a dedicated plant PET imager housed in a plant growth chamber (PGC), which provides a fully controlled environment. The system currently contains two types of scintillation detector modules from commercial small animal PET scanners: 84 microPET® detectors, which are made with scintillation crystal arrays of 2.

Improving PET imaging for breast cancer using virtual pinhole PET half-ring insert.

A PET insert with detector having smaller crystals and placed near a region of interest in a conventional PET scanner can improve image resolution locally due to the virtual-pinhole PET (VP-PET) effect. This improvement is from the higher spatial sampling of the imaging area near the detector. We have built a prototype half-ring PET insert for head-and-neck cancer imaging applications.

Multimodal fluorescence-mediated tomography and SPECT/CT for small-animal imaging.

Unlabelled: Spatial and temporal coregistration of nuclear and optical images can enable the fusion of the information from these complementary molecular imaging modalities. A critical challenge is in integrating the optical and nuclear imaging hardware. Flexible fiber-based fluorescence-mediated tomography (FMT) systems provide a viable solution.

3-D Spatial Resolution of 350 m Pitch Pixelated CdZnTe Detectors for Imaging Applications.

We are currently investigating the feasibility of using highly pixelated Cadmium Zinc Telluride (CdZnTe) detectors for sub-500 m resolution PET imaging applications. A 20 mm × 20 mm × 5 mm CdZnTe substrate was fabricated with 350 m pitch pixels (250 m anode pixels with 100 m gap) and coplanar cathode. Charge sharing among the pixels of a 350 m pitch detector was studied using collimated 122 keV and 511 keV gamma ray sources.