Feasibility and optimization of19F MRI on a clinical 3T with a large field-of-view torso coil.

Objective.The objective of this work is to: (1) demonstrate fluorine-19 (19F) MRI on a 3T clinical system with a large field of view (FOV) multi-channel torso coil (2) demonstrate an example parameter selection optimization for a19F agent to maximize the signal-to-noise ratio (SNR)-efficiency for spoiled gradient echo (SPGR), balanced steady-state free precession (bSSFP), and phase-cycled bSSFP (bSSFP-C), and (3) validate detection feasibility inex vivotissues.Approach.Measurements were conducted on a 3.0T Discovery MR750w MRI (GE Healthcare, USA) with an 8-channel1H/19F torso coil (MRI Tools, Germany). Numerical simulations were conducted for perfluoropolyether to determine the theoretical parameters to maximize SNR-efficiency for the sequences. Theoretical parameters were experimentally verified, and the sensitivity of the sequences was compared with a 10 min acquisition time with a 3.125 × 3.125 × 3 mm3in-plane resolution. Feasibility of a bSSFP-C was also demonstrated in phantom andex vivotissues.Main Results. Flip angles (FAs) of 12 and 64° maximized the signal for SPGR and bSSFP, and validation of optimal FA and receiver bandwidth showed close agreement with numerical simulations. Sensitivities of 2.47, 5.81, and 4.44ms-0.5mM-1 and empirical detection limits of 20.3, 1.5, and 6.2 mM were achieved for SPGR, bSSFP, and bSSFP-C, respectively. bSSFP and bSSFP-C achieved 1.8-fold greater sensitivity over SPGR (p< 0.01).Significance.bSSFP-C was able to improve sensitivity relative to simple SPGR and reduce both bSSFP banding effects and imaging time. The sequence was used to demonstrate the feasibility of19F MRI at clinical FOVs and field strengths withinex-vivotissues.

A stable, highly concentrated fluorous nanoemulsion formulation for in vivo cancer imaging via 19F-MRI.

Magnetic resonance imaging (MRI) is a routine diagnostic modality in oncology that produces excellent imaging resolution and tumor contrast without the use of ionizing radiation. However, improved contrast agents are still needed to further increase detection sensitivity and avoid toxicity/allergic reactions associated with paramagnetic metal contrast agents, which may be seen in a small percentage of the human population. Fluorine-19 (19F)-MRI is at the forefront of the developing MRI methodologies due to near-zero background signal, high natural abundance of 100%, and unambiguous signal specificity. In this study, we have developed a colloidal nanoemulsion (NE) formulation that can encapsulate high volumes of the fluorous MRI tracer, perfluoro-[15-crown-5]-ether (PFCE) (35% v/v). These nanoparticles exhibit long-term (at least 100 days) stability and high PFCE loading capacity in formulation with our semifluorinated triblock copolymer, M2F8H18. With sizes of approximately 200 nm, these NEs enable in vivo delivery and passive targeting to tumors. Our diagnostic formulation, M2F8H18/PFCE NE, yielded in vivo 19F-MR images with a high signal-to-noise ratio up to 100 in a tumor-bearing mouse model at clinically relevant scan times. M2F8H18/PFCE NE circulated stably in the vasculature, accumulated in high concentration of an estimated 4-9 × 1017 19F spins/voxel at the tumor site, and cleared from most organs over the span of 2 weeks. Uptake by the mononuclear phagocyte system to the liver and spleen was also observed, most likely due to particle size. These promising results suggest that M2F8H18/PFCE NE is a favorable 19F-MR diagnostic tracer for further development in oncological studies and potential clinical translation.

Detection and viability of murine NK cells in vivo in a lymphoma model using fluorine-19 MRI.

Natural killer (NK) cell therapies are being increasingly used as an adoptive cell therapy for cancer because they can recognize tumor cells in an antigen-independent manner. While promising, the understanding of NK cell persistence, particularly within a harsh tumor microenvironment, is limited. Fluorine-19 (19 F) MRI is a noninvasive imaging modality that has shown promise in longitudinally tracking cell populations in vivo; however, it has not been studied on murine NK cells. In this study, the impact of 19 F labeling on murine NK cell viability and function was assessed in vitro and then used to quantify NK cell persistence in vivo. While there was no noticeable impact on viability, labeling NK cells with 19 F did attenuate cytotoxicity against lymphoma cells in vitro. Fluorescent microscopy verified 19 F labeling in both the cytoplasm and nucleus of NK cells. Lymphoma-bearing mice were given intratumoral injections of 19 F-labeled NK cells in which signal was detectable across the 6 day observation period via 19 F MRI. Quantification from the composite images detected 78-94% of the initially injected NK cells across 6 days, with a significant decrease between Days 3 and 6. Postmortem flow cytometry demonstrated retention of 19 F intracellularly within adoptively transferred NK cells with less than 1% of 19 F-containing cells identified as tumor-associated macrophages that presumably ingested nonviable NK cells. This work demonstrates that 19 F MRI offers a specific imaging platform to track and quantify murine NK cells within tumors noninvasively.

Concept for a Fan-beam Computed Tomography Image-guided Radiotherapy Device.

Many advancements taking place in the field of radiation therapy come in the form of increasingly powerful devices and specialized treatments that aim to increase precision, visualization, and facility throughput. Although these devices are very effective at their respective roles within radiotherapy, they are expensive and require specialized vaults to shield the public and the radiation worker from the ionizing radiation. A proposed device, known as the Simple XRT, is designed to circumvent the inherent drawbacks of the current devices. The Simple XRT uses a 6 MV linear accelerator that utilizes diagnostic quality computed tomography (CT) image guidance. Simple XRT will serve as a cost-effective device for treating most cancer indications.

Cone Beam CT vs. Fan Beam CT: A Comparison of Image Quality and Dose Delivered Between Two Differing CT Imaging Modalities.

A comparison of image quality and dose delivered between two differing computed tomography (CT) imaging modalities-fan beam and cone beam-was performed. A literature review of quantitative analyses for various image quality aspects such as uniformity, signal-to-noise ratio, artifact presence, spatial resolution, modulation transfer function (MTF), and low contrast resolution was generated. With these aspects quantified, cone beam computed tomography (CBCT) shows a superior spatial resolution to that of fan beam, while fan beam shows a greater ability to produce clear and anatomically correct images with better soft tissue differentiation. The results indicate that fan beam CT produces superior images to that of on-board imaging (OBI) cone beam CT systems, while providing a considerably less dose to the patient.