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Xu Z, Khokhlova TD, Cho CS, Khokhlova VA. Histotripsy: A Method for Mechanical Tissue Ablation with Ultrasound. Annu Rev Biomed Eng 2024; 26:141-167. [PMID: 38346277 DOI: 10.1146/annurev-bioeng-073123-022334] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/05/2024]
Abstract
Histotripsy is a relatively new therapeutic ultrasound technology to mechanically liquefy tissue into subcellular debris using high-amplitude focused ultrasound pulses. In contrast to conventional high-intensity focused ultrasound thermal therapy, histotripsy has specific clinical advantages: the capacity for real-time monitoring using ultrasound imaging, diminished heat sink effects resulting in lesions with sharp margins, effective removal of the treated tissue, a tissue-selective feature to preserve crucial structures, and immunostimulation. The technology is being evaluated in small and large animal models for treating cancer, thrombosis, hematomas, abscesses, and biofilms; enhancing tumor-specific immune response; and neurological applications. Histotripsy has been recently approved by the US Food and Drug Administration to treat liver tumors, with clinical trials undertaken for benign prostatic hyperplasia and renal tumors. This review outlines the physical principles of various types of histotripsy; presents major parameters of the technology and corresponding hardware and software, imaging methods, and bioeffects; and discusses the most promising preclinical and clinical applications.
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Affiliation(s)
- Zhen Xu
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, USA;
| | - Tatiana D Khokhlova
- Applied Physics Laboratory, University of Washington, Seattle, Washington, USA
| | - Clifford S Cho
- Department of Surgery, University of Michigan, Ann Arbor, Michigan, USA
| | - Vera A Khokhlova
- Department of Acoustics, Lomonosov Moscow State University, Moscow, Russia
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Maxwell AD, Vlaisavljevich E. Cavitation-induced pressure saturation: a mechanism governing bubble nucleation density in histotripsy. Phys Med Biol 2024; 69:10.1088/1361-6560/ad3721. [PMID: 38518377 PMCID: PMC11212395 DOI: 10.1088/1361-6560/ad3721] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2023] [Accepted: 03/22/2024] [Indexed: 03/24/2024]
Abstract
Objective.Histotripsy is a noninvasive focused ultrasound therapy that mechanically disintegrates tissue by acoustic cavitation clouds. In this study, we investigate a mechanism limiting the density of bubbles that can nucleate during a histotripsy pulse. In this mechanism, the pressure generated by the initial bubble expansion effectively negates the incident pressure in the vicinity of the bubble. From this effect, the immediately adjacent tissue is prevented from experiencing the transient tension to nucleate bubbles. Approach.A Keller-Miksis-type single-bubble model was employed to evaluate the dependency of this effect on ultrasound pressure amplitude and frequency, viscoelastic medium properties, bubble nucleus size, and transducer geometric focusing. This model was further combined with a spatial propagation model to predict the peak negative pressure field as a function of position from a cavitating bubble.Main results. The single-bubble model showed the peak negative pressure near the bubble surface is limited to the inertial cavitation threshold. The predicted bubble density increased with increasing frequency, tissue viscosity, and transducer focusing angle. The simulated results were consistent with the trends observed experimentally in prior studies, including changes in density with ultrasound frequency and transducerF-number.Significance.The efficacy of the therapy is dependent on several factors, including the density of bubbles nucleated within the cavitation cloud formed at the focus. These results provide insight into controlling the density of nucleated bubbles during histotripsy and the therapeutic efficacy.
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Affiliation(s)
- Adam D Maxwell
- Department of Urology, University of Washington School of Medicine, Seattle, WA, 98195, United States of America
- Department of Biomedical Engineering and Mechanics, Virginia Polytechnic Institute and State University, Blacksburg, VA, 24060, United States of America
| | - Eli Vlaisavljevich
- Department of Biomedical Engineering and Mechanics, Virginia Polytechnic Institute and State University, Blacksburg, VA, 24060, United States of America
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Gong L, Wright AR, Hynynen K, Goertz DE. Inducing cavitation within hollow cylindrical radially polarized transducers for intravascular applications. ULTRASONICS 2024; 138:107223. [PMID: 38553135 DOI: 10.1016/j.ultras.2023.107223] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/11/2023] [Revised: 10/31/2023] [Accepted: 12/12/2023] [Indexed: 04/02/2024]
Abstract
Thrombotic occlusions of large blood vessels are increasingly treated with catheter based mechanical approaches, one of the most prominent being to employ aspiration to extract clots through a hollow catheter lumen. A central technical challenge for aspiration catheters is to achieve sufficient suction force to overcome the resistance of clot material entering into the distal tip. In this study, we examine the feasibility of inducing cavitation within hollow cylindrical transducers with a view to ultimately using them to degrade the mechanical integrity of thrombus within the tip of an aspiration catheter. Hollow cylindrical radially polarized PZT transducers with 3.3/2.5 mm outer/inner diameters were assessed. Finite element simulations and hydrophone experiments were used to investigate the pressure field distribution as a function of element length and resonant mode (thickness, length). Operating in thickness mode (∼5 MHz) was found to be associated with the highest internal pressures, estimated to exceed 23 MPa. Cavitation was demonstrated to be achievable within the transducer under degassed water (10 %) conditions using hydrophone detection and high-frequency ultrasound imaging (40 MHz). Cavitation clouds occupied a substantial portion of the transducer lumen, in a manner that was dependent on the pulsing scheme employed (10 and 100 μs pulse lengths; 1.1, 11, and 110 ms pulse intervals). Collectively the results support the feasibility of achieving cavitation within a transducer compatible with mounting in the tip of an aspiration format catheter.
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Affiliation(s)
- Li Gong
- Department of Medical Biophysics, University of Toronto, Canada; Physical Sciences Platform, Sunnybrook Research Institute, Sunnybrook Health Sciences Centre, Toronto, Canada.
| | - Alex R Wright
- Physical Sciences Platform, Sunnybrook Research Institute, Sunnybrook Health Sciences Centre, Toronto, Canada
| | - Kullervo Hynynen
- Department of Medical Biophysics, University of Toronto, Canada; Physical Sciences Platform, Sunnybrook Research Institute, Sunnybrook Health Sciences Centre, Toronto, Canada; Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Canada
| | - David E Goertz
- Department of Medical Biophysics, University of Toronto, Canada; Physical Sciences Platform, Sunnybrook Research Institute, Sunnybrook Health Sciences Centre, Toronto, Canada
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Suarez Escudero D, Haworth KJ, Genstler C, Holland CK. Quantifying the Effect of Acoustic Parameters on Temporal and Spatial Cavitation Activity: Gauging Cavitation Dose. ULTRASOUND IN MEDICINE & BIOLOGY 2023; 49:2388-2397. [PMID: 37648590 PMCID: PMC10581030 DOI: 10.1016/j.ultrasmedbio.2023.08.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/2023] [Revised: 07/28/2023] [Accepted: 08/01/2023] [Indexed: 09/01/2023]
Abstract
OBJECTIVE Cavitation-enhanced delivery of therapeutic agents is under development for the treatment of cancer and neurodegenerative and cardiovascular diseases, including sonothrombolysis for deep vein thrombosis. The objective of this study was to quantify the spatial and temporal distribution of cavitation activity nucleated by Definity infused through the EKOS catheter over a range of acoustic parameters controlled by the EKOS endovascular system. METHODS Three insonation protocols were compared in an in vitro phantom mimicking venous flow to measure the effect of peak rarefactional pressure, pulse duration and pulse repetition frequency on cavitation activity energy, location and duration. Inertial and stable cavitation activity was quantified using passive cavitation imaging, and a metric of cavitation dose based on energy density was defined. RESULTS For all three insonation protocols, cavitation was sustained for the entire 30 min Definity infusion. The evolution of cavitation energy during each pulse duration was similar for all three protocols. For insonation protocols with higher peak rarefactional acoustic pressures, inertial and stable cavitation doses also increased. A complex relationship between the temporal behavior of cavitation energy within each pulse and the pulse repetition frequency affected the cavitation dose for the three insonation protocols. The relative predominance of stable or inertial cavitation dose varied according to insonation schemes. Passive cavitation images revealed the spatial distribution of cavitation activity. CONCLUSION Our cavitation dose metric based on energy density enabled the impact of different acoustic parameters on cavitation activity to be measured. Depending on the type of cavitation to be promoted or suppressed, particular pulsing schemes could be employed in future studies, for example, to correlate cavitation dose with sonothrombolytic efficacy.
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Affiliation(s)
- Daniel Suarez Escudero
- Department of Internal Medicine, Division of Cardiovascular Health and Disease, University of Cincinnati, Cincinnati, OH, USA
| | - Kevin J Haworth
- Department of Internal Medicine, Division of Cardiovascular Health and Disease, University of Cincinnati, Cincinnati, OH, USA; Department of Biomedical Engineering, University of Cincinnati, Cincinnati, OH, USA
| | | | - Christy K Holland
- Department of Internal Medicine, Division of Cardiovascular Health and Disease, University of Cincinnati, Cincinnati, OH, USA; Department of Biomedical Engineering, University of Cincinnati, Cincinnati, OH, USA.
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Trivedi VV, Wallach EL, Bader KB, Shekhar H. Contrast-Enhanced Imaging of Histotripsy Bubble Clouds Using Chirp-Coded Excitation and Volterra Filtering. IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL 2023; 70:989-998. [PMID: 37379172 DOI: 10.1109/tuffc.2023.3289918] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/30/2023]
Abstract
Histotripsy is a focused ultrasound therapy that ablates tissue via bubble cloud activity. Real-time ultrasound image guidance is used to ensure safe and effective treatment. Plane-wave imaging enables tracking of histotripsy bubble clouds at a high frame rate but lacks adequate contrast. Furthermore, bubble cloud hyperechogenicity is reduced in abdominal targets, making the development of contrast-specific sequences for deep-seated targets an active area of research. Chirp-coded subharmonic imaging was reported previously to enhance histotripsy bubble cloud detection by a modest 4-6 dB compared to the conventional sequence. Incorporating additional steps into the signal processing pipeline could enhance bubble cloud detection and tracking. In this study, we evaluated the feasibility of combining chirp-coded subharmonic imaging with Volterra filtering for enhancing bubble cloud detection in vitro. Chirped imaging pulses were used to track bubble clouds generated in scattering phantoms at a 1-kHz frame rate. Fundamental and subharmonic matched filters were applied to the received radio frequency signals, followed by a tuned Volterra filter to extract bubble-specific signatures. For subharmonic imaging, the application of the quadratic Volterra filter improved the contrast-to-tissue ratio from 5.18 ± 1.29 to 10.90 ± 3.76 dB, relative to the application of the subharmonic matched filter. These findings demonstrate the utility of the Volterra filter for histotripsy image guidance.
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Bhargava A, Huang S, McPherson DD, Bader KB. Assessment of bubble activity generated by histotripsy combined with echogenic liposomes. Phys Med Biol 2022; 67:215015. [PMID: 36220055 DOI: 10.1088/1361-6560/ac994f] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2022] [Accepted: 10/11/2022] [Indexed: 11/05/2022]
Abstract
Objective.Histotripsy is a form of focused ultrasound therapy that uses the mechanical activity of bubbles to ablate tissue. While histotripsy alone degrades the cellular content of tissue, recent studies have demonstrated it effectively disrupts the extracellular structure of pathologic conditions such as venous thrombosis when combined with a thrombolytic drug. Rather than relying on standard administration methods, associating thrombolytic drugs with an ultrasound-triggered echogenic liposome vesicle will enable targeted, systemic drug delivery. To date, histotripsy has primarily relied on nano-nuclei inherent to the medium for bubble cloud generation, and microbubbles associated with echogenic liposomes may alter the histotripsy bubble dynamics. The objective of this work was to investigate the interaction of histotripsy pulse with echogenic liposomes.Approach.Bubble clouds were generated using a focused source in anin vitromodel of venous flow. Acoustic emissions generated during the insonation were passively acquired to assess the mechanical activity of the bubble cloud. High frame rate, pulse inversion imaging was used to track the change in echogenicity of the liposomes following histotripsy exposure.Main results.For peak negative pressures less than 20 MPa, acoustic emissions indicative of stable and inertial bubble activity were observed. As the peak negative pressure of the histotripsy excitation increased, harmonics of the excitation were observed in OFP t-ELIP solutions and plasma alone. Additional observations with high frame rate imaging indicated a transition of bubble behavior as the pulse pressure transitioned to shock wave formation.Significance.These observations suggest that a complex interaction between histotripsy pulses and echogenic liposomes that may be exploited for combination treatment approaches.
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Affiliation(s)
- Aarushi Bhargava
- Department of Radiology, University of Chicago, Chicago, IL, United States of America
| | - Shaoling Huang
- Department of Internal Medicine, Division of Cardiovascular Medicine, University of Texas Health Sciences Center-Houston, Houston, TX, United States of America
| | - David D McPherson
- Department of Internal Medicine, Division of Cardiovascular Medicine, University of Texas Health Sciences Center-Houston, Houston, TX, United States of America
| | - Kenneth B Bader
- Department of Radiology, University of Chicago, Chicago, IL, United States of America
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Mansur A, Garg T, Shrigiriwar A, Etezadi V, Georgiades C, Habibollahi P, Huber TC, Camacho JC, Nour SG, Sag AA, Prologo JD, Nezami N. Image-Guided Percutaneous Ablation for Primary and Metastatic Tumors. Diagnostics (Basel) 2022; 12:diagnostics12061300. [PMID: 35741109 PMCID: PMC9221861 DOI: 10.3390/diagnostics12061300] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2022] [Revised: 05/20/2022] [Accepted: 05/22/2022] [Indexed: 02/06/2023] Open
Abstract
Image-guided percutaneous ablation methods have been further developed during the recent two decades and have transformed the minimally invasive and precision features of treatment options targeting primary and metastatic tumors. They work by percutaneously introducing applicators to precisely destroy a tumor and offer much lower risks than conventional methods. There are usually shorter recovery periods, less bleeding, and more preservation of organ parenchyma, expanding the treatment options of patients with cancer who may not be eligible for resection. Image-guided ablation techniques are currently utilized for the treatment of primary and metastatic tumors in various organs including the liver, pancreas, kidneys, thyroid and parathyroid, prostate, lung, bone, and soft tissue. This article provides a brief review of the various imaging modalities and available ablation techniques and discusses their applications and associated complications in various organs.
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Affiliation(s)
| | - Tushar Garg
- Division of Vascular and Interventional Radiology, Russell H Morgan Department of Radiology and Radiological Science, The Johns Hopkins Hospital, Baltimore, MD 21287, USA; (T.G.); (C.G.)
| | - Apurva Shrigiriwar
- Division of Gastroenterology and Hepatology, The Johns Hopkins Hospital, Baltimore, MD 21287, USA;
| | - Vahid Etezadi
- Division of Vascular and Interventional Radiology, Department of Diagnostic Radiology and Nuclear Medicine, University of Maryland School of Medicine, Baltimore, MD 21201, USA;
| | - Christos Georgiades
- Division of Vascular and Interventional Radiology, Russell H Morgan Department of Radiology and Radiological Science, The Johns Hopkins Hospital, Baltimore, MD 21287, USA; (T.G.); (C.G.)
| | - Peiman Habibollahi
- Department of Interventional Radiology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA;
| | - Timothy C. Huber
- Vascular and Interventional Radiology, Dotter Department of Interventional Radiology, Oregon Health and Science University, Portland, OR 97239, USA;
| | - Juan C. Camacho
- Department of Clinical Sciences, College of Medicine, Florida State University, Tallahassee, FL 32306, USA;
- Vascular and Interventional Radiology, Radiology Associates of Florida, Sarasota, FL 34239, USA
| | - Sherif G. Nour
- Department of Radiology and Medical Imaging, Florida State University College of Medicine, Gainesville, FL 32610, USA;
| | - Alan Alper Sag
- Division of Vascular and Interventional Radiology, Department of Radiology, Duke University Medical Center, Durham, NC 27710, USA;
| | - John David Prologo
- Division of Vascular and Interventional Radiology, Department of Radiology and Imaging Sciences, Emory University School of Medicine, Atlanta, GA 30322, USA;
| | - Nariman Nezami
- Division of Vascular and Interventional Radiology, Department of Diagnostic Radiology and Nuclear Medicine, University of Maryland School of Medicine, Baltimore, MD 21201, USA;
- Experimental Therapeutics Program, University of Maryland Marlene and Stewart Greenebaum Comprehensive Cancer Center, Baltimore, MD 21201, USA
- Correspondence: or
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Wallach EL, Shekhar H, Flores-Guzman F, Hernandez SL, Bader KB. Histotripsy Bubble Cloud Contrast With Chirp-Coded Excitation in Preclinical Models. IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL 2022; 69:787-794. [PMID: 34748487 DOI: 10.1109/tuffc.2021.3125922] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Histotripsy is a focused ultrasound therapy for tissue ablation via the generation of bubble clouds. These effects can be achieved noninvasively, making sensitive and specific bubble imaging essential for histotripsy guidance. Plane-wave ultrasound imaging can track bubble clouds with an excellent temporal resolution, but there is a significant reduction in echoes when deep-seated organs are targeted. Chirp-coded excitation uses wideband, long-duration imaging pulses to increase signals at depth and promote nonlinear bubble oscillations. In this study, we evaluated histotripsy bubble contrast with chirp-coded excitation in scattering gel phantoms and a subcutaneous mouse tumor model. A range of imaging pulse durations were tested, and compared to a standard plane-wave pulse sequence. Received chirped signals were processed with matched filters to highlight components associated with either fundamental or subharmonic (bubble-specific) frequency bands. The contrast-to-tissue ratio (CTR) was improved in scattering media for subharmonic contrast relative to fundamental contrast (both chirped and standard imaging pulses) with the longest-duration chirped-pulse tested (7.4 [Formula: see text] pulse duration). The CTR was improved for subharmonic contrast relative to fundamental contrast (both chirped and standard imaging pulses) by 4.25 dB ± 1.36 dB in phantoms and 3.84 dB ± 6.42 dB in vivo. No systematic changes were observed in the bubble cloud size or dissolution rate between sequences, indicating image resolution was maintained with the long-duration imaging pulses. Overall, this study demonstrates the feasibility of specific histotripsy bubble cloud visualization with chirp-coded excitation.
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Bader KB, Wallach EL, Shekhar H, Flores-Guzman F, Halpern HJ, Hernandez SL. Estimating the mechanical energy of histotripsy bubble clouds with high frame rate imaging. Phys Med Biol 2021; 66:10.1088/1361-6560/ac155d. [PMID: 34271560 PMCID: PMC10680990 DOI: 10.1088/1361-6560/ac155d] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2021] [Accepted: 07/16/2021] [Indexed: 11/11/2022]
Abstract
Mechanical ablation with the focused ultrasound therapy histotripsy relies on the generation and action of bubble clouds. Despite its critical role for ablation, quantitative metrics of bubble activity to gauge treatment outcomes are still lacking. Here, plane wave imaging was used to track the dissolution of bubble clouds following initiation with the histotripsy pulse. Information about the rate of change in pixel intensity was coupled with an analytic diffusion model to estimate bubble size. Accuracy of the hybrid measurement/model was assessed by comparing the predicted and measured dissolution time of the bubble cloud. Good agreement was found between predictions and measurements of bubble cloud dissolution times in agarose phantoms and murine subcutaneous SCC VII tumors. The analytic diffusion model was extended to compute the maximum bubble size as well as energy imparted to the tissue due to bubble expansion. Regions within tumors predicted to have undergone strong bubble expansion were collocated with ablation. Further, the dissolution time was found to correlate with acoustic emissions generated by the bubble cloud during histotripsy insonation. Overall, these results indicate a combination of modeling and high frame rate imaging may provide means to quantify mechanical energy imparted to the tissue due to bubble expansion for histotripsy.
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Affiliation(s)
- Kenneth B Bader
- Department of Radiology, University of Chicago, Chicago, IL, United States of America
| | - Emily L Wallach
- Department of Radiology, University of Chicago, Chicago, IL, United States of America
| | - Himanshu Shekhar
- Discipline of Electrical Engineering, Indian Institute of Technology Gandhinagar, Gandhinagar, Gujarat, India
| | | | - Howard J Halpern
- Department of Radiation and Cellular Oncology, University of Chicago, Chicago, IL United States of America
| | - Sonia L Hernandez
- Department of Surgery, University of Chicago, Chicago, IL, United States of America
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Hendley SA, Bollen V, Anthony GJ, Paul JD, Bader KB. In vitro assessment of stiffness-dependent histotripsy bubble cloud activity in gel phantoms and blood clots. Phys Med Biol 2019; 64:145019. [PMID: 31146275 DOI: 10.1088/1361-6560/ab25a6] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
As a bubble-based ablative therapy, the efficacy of histotripsy has been demonstrated in healthy or acutely diseased models. Chronic conditions associated with stiff tissues may require additional bubble activity prior to histotripsy liquefaction. In this study, histotripsy pulses were generated in agarose phantoms of Young's moduli ranging from 12.3 to 142 kPa, and in vitro clot models with mild and strong platelet-activated retraction. Bubble cloud emissions were tracked with passive cavitation imaging, and the threshold acoustic power associated with phantom liquefaction was extracted with receiver operator characteristic analysis. The power of histotripsy-generated emissions and the degree of liquefaction were tabulated for both clot models. For the agarose phantoms, the acoustic power associated with liquefaction increased with Young's modulus. When grouped based on agarose concentration, only two arms displayed a significant difference in the liquefaction threshold acoustic power (22.1 kPa versus 142 kPa Young's modulus). The bubble cloud dynamics tracked with passive cavitation imaging indicated no strong changes in the bubble dynamics based on the phantom stiffness. For identical histotripsy exposure, the power of acoustic emissions and degree of clot lysis did not vary based on the clot model. Overall, these results indicate that a fixed threshold acoustic power mapped with passive cavitation imaging can be utilized for predicting histotripsy liquefaction over a wide range of tissue stiffness.
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Affiliation(s)
- Samuel A Hendley
- The University of Chicago, Chicago, IL, United States of America. 5812 S Ellis Ave, IB-016, Chicago, IL 60637, United States of America. Author to whom any correspondence should be addressed
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