Comparative Study of Histotripsy Pulse Parameters Used to Inactivate Escherichia coli in Suspension

OBJECTIVE

Bacterial loads can be effectively reduced using cavitation-mediated focused ultrasound, or histotripsy. In this study, gram-negative bacteria (Escherichia coli) in suspension were used as model bacteria to evaluate the effectiveness of two regimens of histotripsy treatments: cavitation histotripsy (CH) and boiling histotripsy (BH).

METHODS

Ten-milliliter volumes of Escherichia coli were treated at different negative focal pressure amplitudes and over time periods up to 40 min. Cavitation activity was characterized with coaxial passive cavitation detection (PCD) and synchronized plane wave B-mode imaging.

RESULTS

CH treatments exhibited a threshold behavior that was consistent with PCD metrics of cavitation. Above the threshold, bacterial inactivation followed a monotonically increasing log-linear relationship that indicated an exponential inactivation rate. BH exhibited no threshold, but instead followed a different monotonically increasing inactivation rate. Inactivation rates were larger for BH at or below the CH threshold, and larger for CH substantially above the threshold. CH studies performed at different pulse lengths at the same duty cycle had similar inactivation rates, suggesting that at any given pressure amplitude, the "on time" was the most important variable for inactivating E. coli. The maximum inactivation was produced by CH at the highest pressure amplitudes used, leading to a log reduction >4.2 for a 40 min treatment.

CONCLUSION

The results of this study suggest that both CH and BH can be used to inactivate E. coli in suspension, with the optimal regimen depending on the attainable peak negative focal pressure at the target.

Enhanced efficacy of direct immunochemotherapy for hepatic cancer with image-guided intratumoral radiofrequency hyperthermia

BACKGROUND

It is still a challenge to prevent tumor recurrence post radiofrequency ablation (RFA) of medium-to-large hepatocellular carcinomas (HCC). Immunochemotherapy, a combination of immunotherapy with chemotherapy, has demonstrated a great potential in augmenting the treatment efficacy for some malignancies. In this study, we validated the feasibility of using radiofrequency hyperthermia (RFH)-enhanced intratumoral immunochemotherapy of LTX-315 with liposomal doxorubicin for rat orthotopic HCC.

METHODS

Different groups of luciferase-labeled rat HCC cells and rat orthotopic HCC models were treated by: (1) phosphate buffered saline; (2) RFH; (3) LTX-315; (4) RFH+LTX-315; (5) liposomal doxorubicin; (6) RFH+liposomal doxorubicin; (7) LTX-315+liposomal doxorubicin; and (8) RFH+LTX-315+liposomal doxorubicin. Cell viabilities and apoptosis of different treatment groups were compared. Changes in tumor sizes were quantified by optical and ultrasound imaging, which were confirmed by subsequent histopathology. The potential underlying biological mechanisms of the triple combination treatment (RFH+LTX-315+liposomal doxorubicin) were explored.

RESULTS

Flow cytometry and MTS assay showed the highest percentage of apoptotic cells and lowest cell viability in the triple combination treatment group compared with other seven groups (p<0.001). Tumors in this group also presented the most profound decrease in bioluminescence signal intensities and the smallest tumor volumes compared with other seven groups (p<0.001). A significant increase of CD8⁺ T cells, CD8⁺/interferon (IFN)-γ⁺ T cells, CD8⁺/tumor necrosis factor (TNF)-α⁺ T cells, and natural killer cells, and a significant decrease of regulatory T cells were observed in the tumors (p<0.001). Meanwhile, a significantly higher level of Th1-type cytokines in both plasma (interleukin (IL)-2, IL-12, IL-18, IFN-γ) and tumors (IL-2, IL-18, IFN-γ, TNF-α), as well as a significantly lower Th2-type cytokines of IL-4 and IL-10 in plasma and tumor were detected.

CONCLUSIONS

Intratumoral RFA-associated RFH could enhance the efficacy of immunochemotherapy of LTX-315 with liposomal doxorubicin for HCC, which may provide a new strategy to increase the curative efficacy of thermal ablation for medium-to-large HCC.

Interventional Optical Imaging-Monitored Synergistic Effect of Radio-Frequency Hyperthermia and Oncolytic Immunotherapy

Purpose

To develop a new interventional oncology technique using indocyanine green (ICG)-based interventional optical imaging (OI) to monitor the synergistic effect of radiofrequency hyperthermia (RFH)-enhanced oncolytic immunotherapy.

Materials and Methods

This study included (1) optimization of ICG dose and detection time-window for intracellular uptake by VX2 tumor cells; (2) in-vitro confirmation of capability of using ICG-based OI to assess efficacy of RFH-enhanced oncolytic therapy (LTX-401) for VX2 cells; and (3) in-vivo validation of the interventional OI-monitored, intratumoral RFH-enhanced oncolytic immunotherapy using rabbit models with orthotopic liver VX2 tumors. Both in-vitro and in-vivo experiments were divided into four study groups (n=6/group) with different treatments: (1) combination therapy of RFH+LTX-401; (2) RFH alone at 42°C for 30 min; (3) oncolytic therapy with LTX-401; and (4) control with saline. For in-vivo validation, orthotopic hepatic VX2 tumors were treated using a new multi-functional perfusion-thermal radiofrequency ablation electrode, which enabled simultaneous delivery of both LTX-401 and RFH within the tumor and at the tumor margins.

Results

In in-vitro experiments, taking up of ICG by VX2 cells was linearly increased from 0 μg/mL to 100 μg/mL, while ICG-signal intensity (SI) reached the peak at 24 hours. MTS assay and apoptosis analysis demonstrated the lowest cell viability and highest apoptosis in combination therapy, compared to three monotherapies (P<0.005). In in-vivo experiments, ultrasound imaging detected the smallest relative tumor volume for the combination therapy, compared to other monotherapies (P<0.005). In both in-vitro and in-vivo experiments, ICG-based interventional optical imaging detected a significantly decreased SI in combination therapy (P<0.005), which was confirmed by the “gold standard” optical/X-ray imaging (P<0.05). Pathologic/laboratory examinations further confirmed the significantly decreased cell proliferation with Ki-67 staining, significantly increased apoptotic index with TUNEL assay, and significantly increased quantities of CD8 and CD80 positive cells with immunostaining in the combination therapy group, compared to other three control groups (P<0.005).

Conclusions

We present a new interventional oncology technique, interventional optical imaging-monitored RFH-enhanced oncolytic immunotherapy, which may open new avenues to effectively manage those patients with larger, irregular and unresectable malignancies, not only in liver but also the possibility in other organs.

Opportunities and Barriers to Rural Telerobotic Surgical Health Care in 2021: Report and Research Agenda from a Stakeholder Workshop

Background: There are well-recognized challenges to delivering specialty health care in rural settings. These challenges are particularly evident for specialized surgical health care due to the lack of trained operators in rural communities. Telerobotic surgery could have a significant impact on the rural-urban health care gap, but thus far, the promise of this method of health care delivery has gone unrealized. With the increasing adoption of telehealth over the past year, along with the maturation of telecommunication and robotic technologies over the past 2 decades, a reappraisal of the opportunities and barriers to widespread implementation of telerobotic surgery is warranted. Here we report the outcome of a rural telerobotic stakeholder workshop to explore modern-day issues critical to the advancement of telerobotic surgical health care. Materials and Methods: We assembled a multidisciplinary stakeholder panel to participate in a 2-day Rural Telerobotic Surgery Stakeholder Workshop. Participants had diverse expertise, including specialty surgeons, technology experts, and representatives of the broader telerobotic health care ecosystem, including economists, lawyers, regulatory consultants, public health advocates, rural hospital administrators, nurses, and payers. The research team reviewed transcripts from the workshop with themes identified and research questions generated based on stakeholder comments and feedback. Results: Stakeholder discussions fell into four general themes, including (1) operating room team interactions, (2) education and training, (3) network and security, and (4) economic issues. The research team then identified several research questions within each of these themes and provided specific research strategies to address these questions. Conclusions: There are still important unanswered questions regarding the implementation and adoption of rural telerobotic surgery. Based on stakeholder feedback, we have developed a research agenda along with suggested strategies to address outstanding research questions. The successful execution of these research opportunities will fill critical gaps in our understanding of how to advance the widespread adoption of rural telerobotic health care.

Sonographic Features of Abscess Maturation in a Porcine Model

Abscesses are walled-off collections of infected fluids that often develop as complications in the setting of surgery and trauma. Treatment is usually limited to percutaneous catheterization with a course of antibiotics. As an alternative to current treatment strategies, a histotripsy approach was developed and tested in a novel porcine animal model. The goal of this article is to use advanced ultrasound imaging modes to extract sonographic features associated with the progression of abscess development in a porcine model. Intramuscular or subcutaneous injections of a bi-microbial bacteria mixture plus dextran particles as an irritant led to identifiable abscesses over a 2 to 3 wk period. Selected abscesses were imaged at least weekly with B-mode, 3-D B-mode, shear-wave elastography and plane-wave Doppler imaging. Mature abscesses were characterized by a well-defined core of varying echogenicity surrounded by a hypoechoic capsule that was highly vascularized on Doppler imaging. 3-D imaging demonstrated the natural history of abscess morphology, with the abscess becoming less complex in shape and increasing in volume. Furthermore, shear-wave elastography demonstrated variations in stiffness as phlegmon becomes abscess and then liquefies, over time. These ultrasound features potentially provide biomarkers to aid in selection of treatment strategies for abscesses.

Treating Porcine Abscesses with Histotripsy: A Pilot Study

Infected abscesses are walled-off collections of pus and bacteria. They are a common sequela of complications in the setting of surgery, trauma, systemic infections and other disease states. Current treatment is typically limited to antibiotics with long-term catheter drainage, or surgical washout when inaccessible to percutaneous drainage or unresponsive to initial care efforts. Antibiotic resistance is also a growing concern. Although bacteria can develop drug resistance, they remain susceptible to thermal and mechanical damage. In particular, short pulses of focused ultrasound (i.e., histotripsy) generate mechanical damage through localized cavitation, representing a potential new paradigm for treating abscesses non-invasively, without the need for long-term catheterization and antibiotics. In this pilot study, boiling and cavitation histotripsy treatments were applied to subcutaneous and intramuscular abscesses developed in a novel porcine model. Ultrasound imaging was used to evaluate abscess maturity for treatment monitoring and assessment of post-treatment outcomes. Disinfection was quantified by counting bacteria colonies from samples aspirated before and after treatment. Histopathological evaluation of the abscesses was performed to identify changes resulting from histotripsy treatment and potential collateral damage. Cavitation histotripsy was more successful in reducing the bacterial load while having a smaller treatment volume compared with boiling histotripsy. The results of this pilot study suggest focused ultrasound may lead to a technology for in situ treatment of acoustically accessible abscesses.

Effect of Stiffness of Large Extravascular Hematomas on Their Susceptibility to Boiling Histotripsy Liquefaction in Vitro

Large intra-abdominal, retroperitoneal and intramuscular hematomas are common consequences of sharp and blunt trauma and post-surgical bleeds, and often threaten organ failure, compartment syndrome or spontaneous infection. Current therapy options include surgical evacuation and placement of indwelling drains that are not effective because of the viscosity of the organized hematoma. We have previously reported the feasibility of using boiling histotripsy (BH)-a pulsed high-intensity focused ultrasound method-for liquefaction of large volumes of freshly coagulated blood and subsequent fine-needle aspiration. The goal of this work was to evaluate the changes in stiffness of large coagulated blood volumes with aging and retraction in vitro, and to correlate these changes with the size of the BH void and, therefore, the susceptibility of the material to BH liquefaction. Large-volume (55-200 mL) whole-blood clots were fabricated in plastic molds from human and bovine blood, either by natural clotting or by recalcification of anticoagulated blood, with or without addition of thrombin. Retraction of the clots was achieved by incubation for 3 h, 3 d or 8 d. The shear modulus of the samples was measured with a custom-built indentometer and shear wave elasticity (SWE) imaging. Sizes of single liquefied lesions produced with a 1.5-MHz high-intensity focused ultrasound transducer within a 30-s standard BH exposure served as the metric for susceptibility of clot material to this treatment. Neither the shear moduli of naturally clotted human samples (0.52 ± 0.08 kPa), nor their degree of retraction (ratio of expelled fluid to original volume 50%-58%) depended on the length of incubation within 0-8 d, and were significantly lower than those of bovine samples (2.85 ± 0.17 kPa, retraction 5%-38%). In clots made from anticoagulated bovine blood, the variation of calcium chloride concentration within 5-40 mmol/L did not change the stiffness, whereas lower concentrations and the addition of thrombin resulted in significantly softer clots, similar to naturally clotted human samples. Within the achievable shear modulus range (0.4-1.6 kPa), the width of the BH-liquefied lesion was more affected by the changes in stiffness than the length of the lesion. In all cases, however, the lesions were larger compared with any soft tissue liquefied with the same BH parameters, indicating higher susceptibility of hematomas to BH damage. These results suggest that clotted bovine blood with added thrombin is an acceptable in vitro model of both acute and chronic human hematomas for assessing the efficiency of BH liquefaction strategies.

Contrast-enhanced ultrasound to ultrasound fusion during microwave ablation: feasibility study in a perfused porcine liver model

PURPOSE

To obtain a complete response with thermal ablation, the margin and entire tumor volume must be treated. Real-time ultrasound visualization is limited during ablation due to gas production. This study assesses the feasibility of fusing volumetric contrast-enhanced ultrasound (CEUS), obtained immediately prior to microwave ablation, with real-time CEUS during and following ablation in a machine-perfused porcine liver.

METHODS

Ten, 3-4 cm microwave ablations were performed in five explanted perfused livers. Prior to ablation, microbubbles were injected into the vasculature while an ultrasound sweep across the liver captured a volumetric image during maximum enhancement. This volumetric image was then fused to overlay the real-time ultrasound imaging. Since the perfused livers did not have tumors, a spherical marker circumscribing a target volume was placed on the images. Approximatively, 75% of the total intended circumscribed spherical volume was ablated. Following ablation, a second bolus injection of ultrasound contrast was administered demonstrating continued enhancement of the intentionally non-ablated 25%. A second volumetric image of the post-ablation CEUS was then fused to overlay the real-time ultrasound images for guidance during ablation of the remaining enhancing volume.

RESULTS

Technical success was achieved in 100% of the cases. The pre- and then the post-ablation CEUS volume was fused with real-time imaging during antenna placement for initial and subsequent ablation.

CONCLUSION

CEUS-CEUS fusion during thermal ablation is feasible and greatly improves the workflow. The approach may augment the use of dynamic CEUS for guidance, improving antenna placement, and aiding in the identification and ablation of initial and residual enhancing tissue.

Hepatotoxic Dose Thresholds by Positron-Emission Tomography After Yttrium-90 Radioembolization of Liver Tumors: A Prospective Single-Arm Observational Study

PURPOSE

To define a threshold radiation dose to non-tumoral liver from ⁹⁰Y radioembolization that results in hepatic toxicity using pair-production PET.

MATERIALS AND METHODS

This prospective single-arm study enrolled 35 patients undergoing radioembolization. A total of 34 patients (27 with HCC and 7 with liver metastases) were included in the final analysis. Of 27 patients with underlying cirrhosis, 22 and 5 patients were Child-Pugh A and B, respectively. Glass and resin microspheres were used in 32 (94%) and 2 (6%) patients, respectively. Lobar and segmental treatment was done in 26 (76%) and 8 (24%) patients, respectively. Volumetric analysis was performed on post-radioembolization time-of-flight PET imaging to determine non-tumoral parenchymal dose. Hepatic toxicity was evaluated up to 120 days post-treatment, with CTCAE grade ≤ 1 compared to grade ≥ 2.

RESULTS

The median dose delivered to the non-tumoral liver in the treated lobe was 49 Gy (range 0-133). A total of 15 patients had grade ≤ 1 hepatic toxicity, and 19 patients had grade ≥ 2 toxicity. Patients with a grade ≥ 2 change in composite toxicity (70.7 vs. 43.8 Gy), bilirubin (74.1 vs. 43.3 Gy), albumin (84.2 vs. 43.8 Gy), and AST (94.5 vs. 47.1 Gy) have significantly higher non-tumoral parenchymal doses than those with grade ≤ 1. Liver parenchymal dose and Child-Pugh status predicted grade ≥ 2 toxicity, observed above a dose threshold of 54 Gy.

CONCLUSION

Increasing delivered ⁹⁰Y dose to non-tumoral liver measured by internal pair-production PET correlates with post-treatment hepatic toxicity. The likelihood of toxicity exceeds 50% at a dose threshold of 54 Gy. ClinicalTrials.gov identifier: NCT02848638.

Abstract P4-08-01: Assessing the safety and feasibility of efficient hypothesis testing in patients with metastatic triple negative breast cancer

We hypothesize that new insights into how cancers progress and respond to treatment will come from clinical trials that i) extensively characterize the molecular features of a patient’s cancer; ii) use results to predict drug susceptibilities; iii) treat in accordance with these predictions; and iv) learn from individual patient outcomes to iterate and improve over time. To investigate the feasibility of this type of clinical study, we launched the "Intensive Trial of OMics in Cancer" (ITOMIC) for patients with metastatic triple negative breast cancer (TNBC) (Clinicaltrials.gov ID: NCT01957514). Eligible patients have metastatic TNBC, are platinum-naive, and are scheduled to receive Cisplatin. Biopsies are performed under carefully controlled conditions prior to Cisplatin – starting all subjects on a common treatment path, and uncoupling the time needed for specimen analysis from immediate therapy. Biopsies are repeated upon completion of Cisplatin and following subsequent therapies. A subset of specimens is chosen for whole Exome Sequencing, deep sequencing of a panel of cancer associated genes, and RNA-sequencing. De-identified results are placed on a web-based server for analysis and discussed at a meeting of the ITOMIC tumor board. A report describing results and potential therapies is provided to the subject’s oncologist. Treatment decisions are left to the discretion of the oncologist. If a decision is taken to pursue treatments identified in our report we offer assistance in accessing those treatments.

Ten patients have been screened and seven have enrolled. Subjects range in age from 40 to 77 years and all but one has received extensive prior treatment for metastatic TNBC. All seven underwent an initial set of biopsies, targeting between two and five metastatic sites. For most metastatic sites, multiple core needle passes are performed. All subjects tolerated the biopsies well without significant adverse events, and all started treatment with Cisplatin. Three subjects completed Cisplatin and underwent a second round of biopsies.

Potential targets for therapy were identified in 5 of the first 6 subjects, and three subjects have received four predicted therapies: 1) a patient with somatic loss of BRCA1 and two linked FGFR2 activating mutations, who was treated first with Veliparib through a single-patient IND and then switched to Ponatinib which produced a partial response; 2) a patient with a novel missense ROS1 mutation treated with crizotinib; and 3) a patient with CYP3A4 copy gain treated with cyclophosphamide.

Conclusion: Our early experience indicates that this approach is feasible and may increase the efficiency of learning from patients with advanced cancer.

Citation Format: C Anthony Blau, Colin Pritchard, Michael O Dorschner, Sibel Blau, Brigham Mecham, Elisabeth Mahen, VK Gadi, Wayne Monsky, Kimberly Burton, Arturo Ramirez, Jackie Stilwell, Eric Kladjian, Carol Collins, Jeannine S McCune, William S Noble, Julie Gralow, Frank Senecal, Linda Dhaene, Nicole Kuderer, Jennifer Specht, Chaozhong Song, Carla Grandori, Nathan Price, Mary Goldman, Aime Radenbaugh, David Haussler, Jingchun Zhu. Assessing the safety and feasibility of efficient hypothesis testing in patients with metastatic triple negative breast cancer [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P4-08-01.

Increased microvascular density and enhanced leukocyte rolling and adhesion in the skin of VEGF transgenic mice

Vascular endothelial growth factor (VEGF) has been implicated in the pathologic angiogenesis observed in psoriasis and other chronic inflammatory skin diseases that are characterized by enhanced expression of VEGF by epidermal keratinocytes and of VEGF receptors by tortuous microvessels in the upper dermis. To investigate the functional importance of chronic VEGF overexpression in vivo, we used a keratin 14 promoter expression cassette containing the gene for murine VEGF164 to selectively target VEGF expression to basal epidermal keratinocytes in transgenic mice. These mice demonstrated an increased density of tortuous cutaneous blood capillaries with elevated expression levels of the high affinity VEGF receptors, VEGFR-1 and VEGFR-2, most prominently during the neonatal period. In contrast, no abnormalities of lymphatic vessels were detected. In addition, the number of mast cells in the upper dermis was significantly increased in transgenic skin. Intravital fluorescence microscopy revealed highly increased leukocyte rolling and adhesion in postcapillary skin venules that were both inhibited after injection of blocking antibodies against E- and P-selectin. Combined blocking antibodies against intercellular adhesion molecule-1 and lymphocyte function-associated antigen-1 were without effect, whereas an anti-vascular cell adhesion molecule-1/VLA-4 antibody combination almost completely normalized the enhanced leukocyte adhesion in transgenic mice. This study reveals VEGF as a growth factor specific for blood vessels, but not lymphatic vessels, and demonstrates that chronic orthotopic overexpression of VEGF in the epidermis is sufficient to induce cardinal features of chronic skin inflammation, providing a molecular link between angiogenesis, mast cell accumulation, and leukocyte recruitment to sites of inflammation.

Enhanced displays of medical images: evaluation of the effectiveness of color, motion, and contour for detecting and localizing liver lesions

RATIONALE AND OBJECTIVES

Many perceptual studies have shown that the detection of large, low-contrast targets is better either in color or in contrast-reversing presentations than in standard gray scale. We determined the value of several new display techniques for viewing liver computed tomography (CT) scans.

METHODS

Eight observers (four radiologists and four nonradiologists) viewed sets of 100 liver CT images (50 with lesions and 50 without) under five display conditions on a Macintosh computer: (1) color (equiluminant color contrast); (2) color-luminance (combined luminance and chromatic contrast); (3) flicker (luminance contrast that reversed polarity at 2 Hz); (4) contour (shaded intensity mapping); and (5) control (conventional gray scale). Receiver operating characteristics (ROC) techniques were used for analysis.

RESULTS

The measured ROC curve areas for the different viewing conditions were as follows: control = 0.77 +/- 0.01 (mean +/- standard error of the mean); color = 0.78 +/- 0.01; color-luminance = 0.82 +/- 0.01; flicker = 0.78 +/- 0.01; and contour = 0.76 +/- 0.01. The percentage of lesions correctly located ranged from 0.82 (color-luminance) to 0.75 (flicker). Performance under the color-luminance condition was significantly better than in the control condition (p = .01), whereas the other experimental conditions were not significantly different from the control condition (p > .21).

CONCLUSION

The use of mixed color and luminance displays may have perceptual advantages for radiologists and can improve performance over that of gray-scale viewing.