Liver Fibrosis Assessment by Viewing Sinusoidal Capillarization: US Molecular Imaging versus Two-dimensional Shear-Wave Elastography in Rats.

Background US elastography is a first-line assessment of liver fibrosis severity; however, its application is limited by its insufficient sensitivity in early-stage fibrosis detection and its measurements are affected by inflammation. Purpose To assess the sensitivity of US molecular imaging (USMI) in early-stage liver fibrosis detection and to determine whether USMI can specifically distinguish fibrosis regardless of inflammation when compared with two-dimensional (2D) shear-wave elastography (SWE). Materials and methods USMI and 2D SWE were performed prospectively (January to June 2021) in 120 male Sprague-Dawley rats with varying degrees of liver fibrosis and acute hepatitis and control rats. Liver sinusoidal capillarization was viewed at CD34-targeted USMI and quantitatively analyzed by the normalized intensity difference (NID). Data were compared by using a two-sided Student t test or one-way analysis of variance. Linear correlation analyses were used to evaluate the relationships between collagen proportionate area values and NID and liver stiffness measurement (LSM) values. Receiver operating characteristic curves were used to assess the diagnostic performance in detecting liver fibrosis. Results Both NID and LSM values showed good linear correlation with collagen proportionate area values (r = 0.91 and 0.87, respectively). No difference was observed between the areas under the receiver operating characteristic curve in detecting stage F0-F1 between USMI and 2D SWE (0.97 vs 0.91, respectively; P = .20). USMI depicted liver fibrosis at an early stage more accurately than 2D SWE (area under the curve, 0.97 vs 0.82, respectively; P = .01). Rats with hepatitis had higher liver stiffness values than control rats (9.83 kPa ± 0.79 vs 6.55 kPa ± 0.38, respectively; P < .001), with no difference in the NID values between control rats and rats with hepatitis (6.75% ± 1.43 vs 6.74% ± 0.86, respectively; P = .98). Conclusion Sinusoidal capillarization viewed at US molecular imaging helped to detect early-stage liver fibrosis more accurately than two-dimensional shear-wave elastography and helped assess fibrosis regardless of inflammation. © RSNA, 2022 Online supplemental material is available for this article. See also the editorial by Barr in this issue.

Intracolic ultrasound molecular imaging: a novel method for assessing colonic tumor necrosis factor-α expression in inflammatory bowel disease.

BACKGROUND: While anti-tumor necrosis factor alpha (TNF-α) therapy has been proven effective in inflammatory bowel disease (IBD), approximately 40% of patients lose the response. Transmembrane TNF-α (mTNF-α) expression in the intestinal mucosa is correlated with therapeutic efficacy, and quantification of mTNF-α expression is significant for predicting response. However, conventional intravenous application of microbubbles is unable to assess mTNF-α expression in intestinal mucosa. Herein, we proposed intracolic ultrasound molecular imaging with TNF-α-targeted microbubbles (MBTNF-α) to quantitatively detect mTNF-α expression in the intestinal mucosa. METHODS: MBTNF-α was synthesized via a biotin-streptavidin bridging method. TNF-α-targeted ultrasound imaging was performed by intracolic application of MBTNF-α to detect mTNF-α expression in surgical specimens from a murine model and patients with IBD. Linear regression analyses were performed to confirm the accuracy of quantitative targeted ultrasound imaging. RESULTS: On quantitative TNF-α-targeted ultrasound images, a greater signal intensity was observed in the mouse colons with colitis ([1.96 ± 0.45] × 106 a.u.) compared to that of the controls ([0.56 ± 0.21] × 106 a.u., P < 0.001). Targeted US signal intensities and inflammatory lesions were topographically coupled in mouse colons. Linear regression analyses in specimens of mice and patients demonstrated significant correlations between the targeted ultrasound signal intensity and mTNF-α expression (both P < 0.001). Furthermore, TNF-α-targeted ultrasound imaging qualitatively distinguished the varying inflammatory severity in intestinal specimens from IBD patients. CONCLUSION: Intracolic ultrasound molecular imaging with MBTNF-α enables quantitative assessment of mTNF-α expression. It may be a potential tool for facilitating the implementation of personalized medicine in IBD.

Molecular ultrasound imaging of neutrophil membrane-derived biomimetic microbubbles for quantitative evaluation of hepatic ischemia-reperfusion injury.

Rationale: Early diagnosis of hepatic ischemia-reperfusion injury (HIRI), the major cause of early allograft dysfunction or primary non-function, is critical in orthotopic liver transplantation. However, liver biopsy is still the primary method for HIRI evaluation in clinical practice despite its numerous complications and shortcomings such as hemorrhage and inaccuracy. Herein, we aimed to develop a non-invasive, highly accurate, and specific method for detecting HIRI. Methods: We developed a top-down and bottom-up strategy to fabricate neutrophil biomimetic microbubbles (MBneu). Neutrophil membrane was mixed with liposomes at a defined mass ratio by sonication. The air in the vial was exchanged with perfluoropropane, and then the solution was mechanically vibrated to form MBneu. Results: MBneu retained the neutrophil proteins, preferentially targeted inflamed hepatic tissue in a rat model of HIRI, and demonstrated physicochemical properties typical of liposome-based MBs because of its artificial phospholipid content. With MBneu we can quantitively evaluate the severity of HIRI, which is helpful for early diagnosis and the prediction of outcome. In addition, MBneu was shown to be safe and showed no immunogenicity. Conclusion: We demonstrated molecular ultrasound imaging of HIRI with MBneu. This new synthesis strategy may be applied to different clinical scenarios using other cell types in the future.

Improving Ablation Safety for Hepatocellular Carcinoma Proximal to the Hilar Bile Ducts by Ultrasound-MR Fusion Imaging: A Preliminary Comparative Study.

AIM: To explore whether ablation safety could be improved by ultrasound (US)-magnetic resonance (MR) fusion imaging for hepatocellular carcinoma (HCC) proximal to the hilar bile ducts (HBDs) through a preliminary comparative study. METHODS: Between January 2014 and June 2019, 18 HCC nodules proximal to the HBDs were included in a US-MR fusion imaging-assisted radiofrequency ablation (RFA) group (study group), while 13 HCC nodules in a similar location were included as a control group. For the study group, the tumor and adjacent bile ducts were outlined on preprocedural MR images. Procedural ablation planning was conducted to assess the feasibility of ablating the tumors while avoiding biliary injury. Such tumors were then ablated under US-MR fusion imaging guidance. The control group nodules were ablated under conventional ultrasound guidance. Baseline characteristics and outcomes were compared between the groups. RESULTS: After preprocedural assessment, 14 of 18 patients with tumors that were feasible to ablate underwent US-MR fusion imaging-assisted RFA. No biliary complications were observed in these 14 patients; the complication rate was significantly lower in the study group than in the control group (30.8%, 4/13) (P = 0.041). There was no significant difference in the technique efficacy rates [92.9% (13/14) versus 100% (13/13), P = 1] or local progression rates [7.1% (1/14) versus 7.7% (1/13), P = 1] between the study and control groups. CONCLUSIONS: US-MR fusion imaging may be a non-invasive means for assisting RFA of HCC nodules proximal to the HBDs and ensuring ablation safety.

Feasibility of 3D US/CEUS-US/CEUS fusion imaging-based ablation planning in liver tumors: a retrospective study.

PURPOSE: To assess the feasibility of ablation planning based on fusion imaging of three-dimensional ultrasound/contrast-enhanced ultrasound (3D US/CEUS) with real-time US/CEUS for liver tumor thermal ablation. MATERIALS AND METHODS: Between January 2017 and December 2018, 85 hepatic tumors from 82 patients who underwent percutaneous ablation were included. First, intraprocedural 3D US/CEUS imaging was performed for ablation planning. Then, fusion imaging of 3D US/CEUS with real-time US/CEUS was used to guide the implementation of the plan, immediately evaluate the technical success and indicate the need for supplemental ablation. In addition, contrast-enhanced CT/MR imaging was performed 1 month after the procedure to evaluate the presence of residual tumors, and follow-up scans were repeated every 3 months. RESULTS: The average liver tumor diameter was 28 ± 9 mm (range, 10-55 mm). 3D US/CEUS-based planning was successfully conducted in all 85 tumors with a 100% technical success rate of planning. The immediate evaluation by 3D CEUS/US-CEUS fusion imaging showed a 100% technical success rate of ablation. The 1-month CT/MR scans found a residual tumor in one intrahepatic cholangiocarcinoma patient; the technique efficacy rate was 98.8%. The median follow-up period was 21.5 months (IQR: 4-36 months). During the follow-up period, the local tumor progression rate was 5.9% (5/84), and no major procedure-related complications occurred. CONCLUSIONS: Ablation planning based on 3D US/CEUS-US/CEUS fusion imaging is feasible for liver tumors.

Transcholecystic Contrast-Enhanced Ultrasound-Guided Percutaneous Transhepatic Biliary Drainage for Central Bile Duct Protection During Thermal Tumor Ablation.

Intraductal cooling via a percutaneous transhepatic biliary drainage tube holds great promise in facilitating thermal ablation of liver tumors adjacent to the central bile ducts. However, the difficulties and complications associated with puncturing nondilated bile ducts are greater than those associated with puncturing dilated bile ducts. As reported here, percutaneous transcholecystic contrast-enhanced ultrasound was performed in 7 patients to visualize the nondilated bile ducts and guide percutaneous transhepatic biliary drainage, thus facilitating the intraductal cooling-assisted thermal ablation process. The procedures were technically successful in all 7 patients, and no major complications were recorded during the follow-up period.

Simple structural indocyanine green-loaded microbubbles for dual-modality imaging and multi-synergistic photothermal therapy in prostate cancer.

As problems with the overuse of radical prostate cancer (PCa) treatment are increasingly exposed, focal therapy represents the direction of low- or intermediate-risk PCa management in the future. However, inaccurate diagnosis and low controllability of focal therapy hinder its clinical translation. In this study, we develop simple structural cyclic arginine-glycine-aspartic (cRGD) peptide-modified and indocyanine green (ICG)-loaded microbubbles (cRGD-ICG-MBs) for ultrasound-photoacoustic imaging and multi-synergistic photothermal therapy (PTT) to address the above problems. Precise PCa diagnosis is achieved by molecular ultrasound imaging. cRGD-targeting and low-frequency ultrasound with an amplitude of 500kPa convert MBs into nanoparticles for enhanced ICG delivery. Alow frequency2500 kPa amplitude ultrasound enables temporary vasculature destruction, which minimizes heat loss during PTT. Specifically, ICG in the tumor region is 14-fold higher than the control, resulting in satisfactory PTT. Our study highlights that this theranostic strategy possesses considerable clinical translational potential, especially in mini-invasive and individualized PCa therapy.

Porphyrin-grafted Lipid Microbubbles for the Enhanced Efficacy of Photodynamic Therapy in Prostate Cancer through Ultrasound-controlled In Situ Accumulation.

Photodynamic therapy (PDT) holds promise for focal therapy of prostate cancer (PCa). However, the therapeutic efficacy needs improvement, and further development of PDT for PCa has challenges, including uncertainty of photosensitizers (PSs) accumulation at the tumor site and difficulty in visualizing lesions using conventional ultrasound (US) imaging. We have developed novel porphyrin-grafted lipid (PGL) microbubbles (MBs; PGL-MBs) and propose a strategy to integrate PGL-MBs with US imaging to address these limitations and enhance PDT efficacy. METHODS: PGL-MBs have two functions: imaging guidance by contrast-enhanced ultrasound (CEUS) and targeted delivery of PSs by ultrasound targeted microbubble destruction (UTMD). PGL-MBs were prepared and characterized before and after low-frequency US (LFUS) exposure. Then, in vitro studies validated the efficacy of PDT with PGL-MBs in human prostate cancer PC3 cells. PC3-xenografted nude mice were used to validate CEUS imaging, accumulation at the tumor site, and in vivo PDT efficacy. RESULTS: PGL-MBs showed good contrast enhancement for US imaging and were converted into nanoparticles upon LFUS exposure. The resulting uniquely structured nanoparticles avoided porphyrin fluorescence quenching and efficiently accumulated at the tumor site through the sonoporation effect created with the assistance of US to achieve excellent PDT efficacy. CONCLUSIONS: This is the first preclinical investigation of MBs applied in PDT for PCa. PGL-MBs possess favorable CEUS imaging effects to enhance the localization of tumors. PGL-MBs with LFUS control PS accumulation at the tumor site to achieve highly effective PDT of PCa. This strategy carries enormous clinical potential for PCa management.

Indocyanine Green Loaded Reduced Graphene Oxide for In Vivo Photoacoustic/Fluorescence Dual-Modality Tumor Imaging.

Multimodality imaging based on multifunctional nanocomposites holds great promise to fundamentally augment the capability of biomedical imaging. Specifically, photoacoustic and fluorescence dual-modality imaging is gaining much interest because of their non-invasiveness and the complementary nature of the two modalities in terms of imaging resolution, depth, sensitivity, and speed. Herein, using a green and facile method, we synthesize indocyanine green (ICG) loaded, polyethylene glycol (PEG)ylated, reduced nano-graphene oxide nanocomposite (rNGO-PEG/ICG) as a new type of fluorescence and photoacoustic dual-modality imaging contrast. The nanocomposite is shown to have minimal toxicity and excellent photoacoustic/fluorescence signals both in vitro and in vivo. Compared with free ICG, the nanocomposite is demonstrated to possess greater stability, longer blood circulation time, and superior passive tumor targeting capability. In vivo study shows that the circulation time of rNGO-PEG/ICG in the mouse body can sustain up to 6 h upon intravenous injection; while after 1 day, no obvious accumulation of rNGO-PEG/ICG is found in any major organs except the tumor regions. The demonstrated high fluorescence/photoacoustic dual contrasts, together with its low toxicity and excellent circulation life time, suggest that the synthesized rNGO-PEG/ICG can be a promising candidate for further translational studies on both the early diagnosis and image-guided therapy/surgery of cancer.