tumor ablation releases a unique repertoire of antigens from a heterogeneous population of tumor cells. High-intensity focused ultrasound (HIFU) is a completely noninvasive ablation therapy that can ...be used to ablate tumors either by heating (thermal (T)-HIFU) or by mechanical disruption (mechanical (M)-HIFU). How different HIFU ablation techniques compare with respect to their antigen release profile, their activation of responder T cells, and their ability to synergize with immune stimuli remains to be elucidated.
Here, we compare the immunomodulatory effects of T-HIFU and M-HIFU ablation with or without the TLR9 agonist CpG in the ovalbumin-expressing lymphoma model EG7. M-HIFU ablation alone, but much less so T-HIFU, significantly increased dendritic cell (DC) activation in draining lymph nodes (LNs). Administration of CpG following T- or M-HIFU ablation increased DC activation in draining LNs to a similar extend. Interestingly,
co-cultures of draining LN suspensions from HIFU plus CpG treated mice with CD8
OT-I T cells demonstrate that LN cells from M-HIFU treated mice most potently induced OT-I proliferation. To delineate the mechanism for the enhanced anti-tumor immune response induced by M-HIFU, we characterized the RNA, DNA and protein content of tumor debris generated by both HIFU methods. M-HIFU induced a uniquely altered RNA, DNA and protein profile, all showing clear signs of fragmentation, whereas T-HIFU did not. Moreover, western blot analysis showed decreased levels of the immunosuppressive cytokines IL-10 and TGF-β in M-HIFU generated tumor debris compared to untreated tumor tissue or T-HIFU.
Collectively, these results imply that M-HIFU induces a unique context of the ablated tumor material, enhancing DC-mediated T cell responses when combined with CpG.
Purpose
Isoflurane (ISO) is the most commonly used preclinical inhalation anesthetic. This is a problem in
19
F MRI of fluorine contrast agents, as ISO signals cause artifacts that interfere with ...unambiguous image interpretation and quantification; the two most attractive properties of heteronuclear MRI. We aimed to avoid these artifacts using MRI strategies that can be applied by any pre-clinical researcher.
Procedures
Three strategies to avoid ISO chemical shift displacement artifacts (CSDA) in
19
F MRI are described and demonstrated with measurements of
19
F-containing agents in phantoms and
in vivo
(
n
= 3 for all strategies). The success of these strategies is compared to a standard Rapid Acquisition with Relaxation Enhancement (RARE) sequence, with phantom and
in vivo
validation. ISO artifacts can successfully be avoided by (1) shifting them outside the region of interest using a narrow signal acquisition bandwidth, (2) suppression of ISO by planning a frequency-selective suppression pulse before signal acquisition or by (3) preventing ISO excitation with a 3D sequence with a narrow excitation bandwidth.
Results
All three strategies result in complete ISO signal avoidance (
p
< 0.0001 for all methods). Using a narrow acquisition bandwidth can result in loss of signal to noise ratio and distortion of the image, and a frequency-selective suppression pulse can be incomplete when B
1
-inhomogeneities are present. Preventing ISO excitation with a narrow excitation pulse in a 3D sequence yields the most robust results (relative SNR 151 ± 28% compared to 2D multislice methods,
p
= 0.006).
Conclusion
We optimized three easily implementable methods to avoid ISO signal artifacts and validated their performance in phantoms and
in vivo
. We make recommendation on the parameters that pre-clinical studies should report in their method section to make the used approach insightful.
Increased glucose and choline uptake are hallmarks of cancer. We investigated whether the uptake and conversion of 2H9choline alone and together with that of 6,6′-2H2glucose can be assessed in tumors ...via deuterium metabolic imaging (DMI) after administering these compounds. Therefore, tumors with human renal carcinoma cells were grown subcutaneously in mice. Isoflurane anesthetized mice were IV infused in the MR magnet for ~20 s with ~0.2 mL solutions containing either 2H9choline (0.05 g/kg) alone or together with 6,6′-2H2glucose (1.3 g/kg). 2H MR was performed on a 11.7T MR system with a home-built 2H/1H coil using a 90° excitation pulse and 400 ms repetition time. 3D DMI was recorded at high resolution (2 × 2 × 2 mm) in 37 min or at low resolution (3.7 × 3.7 × 3.7 mm) in 2:24 min. Absolute tissue concentrations were calculated assuming natural deuterated water HOD = 13.7 mM. Within 5 min after 2H9choline infusion, its signal appeared in tumor spectra representing a concentration increase to 0.3–1.2 mM, which then slowly decreased or remained constant over 100 min. In plasma, 2H9choline disappeared within 15 min post-infusion, implying that its signal arises from tumor tissue and not from blood. After infusing a mixture of 2H9choline and 6,6′-2H2glucose, their signals were observed separately in tumor 2H spectra. Over time, the 2H9choline signal broadened, possibly due to conversion to other choline compounds, 6,6′-2H2glucose declined, HOD increased and a lactate signal appeared, reflecting glycolysis. Metabolic maps of 2H compounds, reconstructed from high resolution DMIs, showed their spatial tumor accumulation. As choline infusion and glucose DMI is feasible in patients, their simultaneous detection has clinical potential for tumor characterization.
Abstract In patients with Alzheimer's disease (AD) the severity of white matter degeneration correlates with the clinical symptoms of the disease. In this study, we performed diffusion-tensor ...magnetic resonance imaging at ultra-high field in a mouse model for AD (APPswe /PS1dE9 ) in combination with a voxel-based approach and tractography to detect changes in water diffusivity in white and gray matter, because these reflect structural alterations in neural tissue. We found substantial changes in water diffusion parallel and perpendicular to axonal tracts in several white matter regions like corpus callosum and fimbria of the hippocampus, that match with previous findings of axonal disconnection and myelin degradation in AD patients. Moreover, we found a significant increase in diffusivity in specific hippocampal subregions, which is supported by neuronal loss as visualized with Klüver-Barrera staining. This work demonstrates the potential of ultra-high field diffusion-tensor magnetic resonance imaging as a noninvasive modality to describe white and gray matter structural changes in mouse models for neurodegenerative disorders, and provides valuable knowledge to assess future AD prevention strategies in translational research.
Animals need to respond to threats to avoid danger and approach rewards. In nature, these responses did not evolve alone but are always accompanied by motivational conflict. A semi-naturalistic ...threat imminence continuum model models the approach-avoidance conflict and is able to integrate multiple behaviors into a single paradigm. However, its comprehensive application is hampered by the lack of a detailed protocol and data about some fundamental factors including sex, age, and motivational level. Here, we modified a previously established paradigm measuring threat imminence continuum dynamics, involving modifications of training and testing protocols, and utilization of commercial materials combined with open science codes, making it easier to replicate. We demonstrate that foraging behavior is modulated by age, hunger level, and sex. This paradigm can be used to study foraging behaviors in animals in a more naturalistic manner with relevance to human approach-avoid conflicts and associated psychopathologies.
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•We provide detailed guidance for setting up a modified paradigm for the threat imminence continuum model with commercial materials and open-source codes.•We propose a modified paradigm for the threat imminence continuum model to quantify foraging behaviors.•Our method enables comparison between groups as a function of multiple factors including age and food restriction.
Purpose
To evaluate the feasibility of ex vivo 7T MRI to assess surgical margins (SMs) and pseudocapsule (PC) features after partial nephrectomy (PN).
Materials and methods
In this prospective, ...IRB-approved study, seven patients undergoing a PN for nine tumours between November 2014 and July 2015 were included for analysis after obtaining informed consent. MRI of the specimen was acquired using a 7T small bore scanner. The imaging protocol consisted of anatomical T1-, T2- and diffusion-weighted imaging. After formalin fixation, specimens were cut for pathology work-up in the same orientation as the MR images were obtained. The entire specimen was processed into H&E slides that were digitally scanned, annotated and correlated with radiological findings for negative SMs, PC presence, PC continuity and extra-PC-extension (EPCE). Sensitivity and specificity of MRI for assessment of these endpoints were calculated.
Results
The sensitivity and specificity for assessment of the SM were 100% and 75%, respectively. Two false-positive outcomes were reported, both in case of EPCE and a SM ≤0.5 mm. For the presence of a PC, sensitivity and specificity were 100% and 33%, respectively. Two false-positive scans with anatomical structures mimicking the presence of a PC occurred. If a PC was present, continuity and EPCE were assessed with a sensitivity and specificity of 75% and 100% and 67% and 100%, respectively.
Conclusion
Ex vivo 7T MRI is a feasible tool for perioperative evaluation of SMs, and if present, PC features after PN. This may facilitate maximal sparing of renal parenchyma without compromising oncological outcomes.
Key Points
• Ex vivo MRI may contribute to improvement of negative surgical margins during partial nephrectomy.
• Due to the assessment of surgical margins within a limited time span from obtaining the partial nephrectomy specimen, surgery for more complex tumours is possible with maximum sparing of healthy renal parenchyma without compromising oncological outcomes.
• The intra operative assessment of pseudocapsule continuity along the resection margin enables maximal sparing of healthy renal parenchyma without delayed diagnosis of incomplete resection.
Polymeric nanoparticles (NPs) find many uses in nanomedicine, from drug delivery to imaging. In this regard, poly (lactic-co-glycolic acid) (PLGA) and polyethylene glycol (PEG) particles are the most ...widely applied types of nano-systems due to their biocompatibility and biodegradability. Here we developed novel fluorinated polymeric NPs as vectors for multi-modal nanoprobes. This approach involved modifying polymeric NPs with trifluoroacetamide (TFA) and loading them with a near-infrared (NIR) dye for different imaging modalities, such as magnetic resonance imaging (MRI) and optical imaging. The PLGA-PEG-TFA NPs generated were characterized in vitro using the C28/I2 human chondrocyte cell line and in vivo in a mouse model of osteoarthritis (OA). The NPs were well absorbed, as confirmed by confocal microscopy, and were non-toxic to cells. To test the NPs as a drug delivery system for contrast agents of OA, the nanomaterial was administered via the intra-articular (IA) administration method. The dye-loaded NPs were injected in the knee joint and then visualized and tracked in vivo by fluorine-19 nuclear magnetic resonance and fluorescence imaging. Here, we describe the development of novel intrinsically fluorinated polymeric NPs modality that can be used in various molecular imaging techniques to visualize and track OA treatments and their potential use in clinical trials.
Purpose
To investigate the ability of high field ex vivo magnetic resonance imaging (MRI) to localize prostate cancer (PCa) and to predict the margin status in fresh radical prostatectomy (RP) ...specimens using histology as the reference standard.
Materials and Methods
This Institutional Review Board (IRB)‐approved study had written informed consent. Patients with biopsy‐proved PCa and a diagnostic multiparametric 3T MRI examination of the prostate prior to undergoing RP were prospectively included. A custom‐made container provided reference between the 7T ex vivo MRI obtained from fresh RP specimens and histological slicing. On ex vivo MRI, PCa was localized and the presence of positive surgical margins was determined in a double‐reading session. These findings were compared with histological findings obtained from completely cut, whole‐mount embedded, prostate specimens.
Results
In 12 RP specimens, histopathology revealed 36 PCa lesions, of which 17 (47%) and 20 (56%) were correlated with the ex vivo MRI in the first and second reading session, respectively. Nine of 12 (75%) index lesions were localized in the first session, in the second 10 of 12 (83%). Seven and 8 lesions of 11 lesions with Gleason score >6 and >0.5 cc were localized in the first and second session, respectively. In the first session none of the four histologically positive surgical margins (sensitivity 0%) and 9 of 13 negative margins (specificity 69%) were detected. In second session the sensitivity and specificity were 25% and 88%, respectively.
Conclusion
Ex vivo MRI enabled accurate localization of PCa in fresh RP specimens, and the technique provided information on the margin status with high specificity.
Level of Evidence: 1
Technical Efficacy: Stage 1
J. Magn. Reson. Imaging 2018;47:439–448.
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