1
|
Rokni E, Kitur EC, Simon JC. Dynamics of crevice microbubbles that cause the twinkling artifact. ULTRASONICS SONOCHEMISTRY 2024; 108:106971. [PMID: 38941704 PMCID: PMC11260575 DOI: 10.1016/j.ultsonch.2024.106971] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/27/2024] [Revised: 06/21/2024] [Accepted: 06/24/2024] [Indexed: 06/30/2024]
Abstract
The Doppler ultrasound twinkling artifact, a rapid color shift, appears on pathological mineralizations and is theorized to arise from scattering off micron-sized crevice microbubbles. However, the influence of crevice number and size as well as the bubble dynamics on twinkling is not well-understood. Cylinders with diameters of 0.8-1.2 µm and depths of 1 µm were etched into a silicon wafer and crevice bubbles were driven at 0.75, 2.5, and 5.0 MHz while monitoring with high-speed photography. Experimental results were compared to a derived crevice bubble model. On three separate wafers, cylindrical crevices (10 or 100) with diameters of 1, 10, or 100 µm and depths of 10 µm were etched and imaged with a research ultrasound system in Doppler mode at 5, 7.8, and 18.5 MHz. Within the pressure ranges studied here (∼1MPa), no bubble oscillation was observed for the 0.8-1.2 µm crevice bubbles which matched computational results. Crevices with 1 and 10 µm diameters produced more twinkling than 100 µm crevices at 5 and 7.8 MHz. In contrast, 100 µm crevices produced more twinkling than 1 or 10 µm crevices at 18.5 MHz (p < 0.001 in all cases). These results provide better insight into how crevice bubbles cause twinkling on pathological mineralizations.
Collapse
Affiliation(s)
- Eric Rokni
- Graduate Program in Acoustics, The Pennsylvania State University, University Park, PA 16802, USA.
| | - Eusila C Kitur
- Graduate Program in Acoustics, The Pennsylvania State University, University Park, PA 16802, USA
| | - Julianna C Simon
- Graduate Program in Acoustics, The Pennsylvania State University, University Park, PA 16802, USA
| |
Collapse
|
2
|
Dupere JM, Brost EE, Uthamaraj S, Lee CU, Urban MW, Stish BJ, Deufel CL. A new way to visualize prostate brachytherapy needles using ultrasound color Doppler and needle surface modifications. Brachytherapy 2023; 22:761-768. [PMID: 37652777 DOI: 10.1016/j.brachy.2023.07.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2023] [Revised: 06/30/2023] [Accepted: 07/04/2023] [Indexed: 09/02/2023]
Abstract
PURPOSE Suboptimal ultrasound conspicuity of the brachytherapy applicator can lead to inaccurate image reconstructions of the applicator resulting in decreased tumor control or increased normal tissue dose. This feasibility study aims to improve ultrasound conspicuity of high-dose rate (HDR) brachytherapy needles by modifying the surface of the needles to produce a color Doppler twinkling signature. MATERIALS AND METHODS Surface modifications of standard 17-gauge titanium HDR brachytherapy needles included laser-scribing, application of polymethyl methacrylate (PMMA), and coating with a commercially available echogenic coating. Laser-scribing was performed with variable widths (0.1-1 mm) and depths (10-100 μm). The echogenic coating was applied with 3 different thicknesses (27, 40, and 64 μm). Unmodified and modified needles were imaged under B-mode and color Doppler ultrasound in phantom and cadaver, and the signal strength was recorded. RESULTS Laser-scribed, PMMA-coated, and echogenic-coated brachytherapy needles produced a twinkling signature along the needle shaft on color Doppler ultrasound. Twinkling was observed with laser-scribe depths >20 μm and widths >0.1 mm and from echogenic coatings 40 μm and 64 μm thick. Twinkling was not observed with unmodified needles. The twinkling signature had a spectral composition with a uniform magnitude between the velocities of 2 to 16 cm/s. CONCLUSIONS Color Doppler ultrasound of surface-modified brachytherapy applicators may improve applicator conspicuity aiding applicator placement and digitization. HDR brachytherapy needles may be modified to produce the twinkling signature via laser-scribing, PMMA rings, or applying an echogenic coating.
Collapse
Affiliation(s)
| | - Eric E Brost
- Department of Radiation Oncology, Mayo Clinic, Rochester, MN
| | | | | | | | - Bradley J Stish
- Department of Radiation Oncology, Mayo Clinic, Rochester, MN
| | | |
Collapse
|
3
|
Rokni E, Simon JC. The effect of crystal composition and environment on the color Doppler ultrasound twinkling artifact. Phys Med Biol 2023; 68. [PMID: 36634375 DOI: 10.1088/1361-6560/acb2ad] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2022] [Accepted: 01/12/2023] [Indexed: 01/14/2023]
Abstract
Objective.Pathological mineralizations form throughout the body and can be difficult to detect using conventional imaging methods. Color Doppler ultrasound twinkling highlights ∼60% of kidney stones with a rapid color shift and is theorized to arise from crevice microbubbles as twinkling disappears on kidney stones at elevated pressures and scratched acrylic balls in ethanol. Twinkling also sometimes appears on other pathological mineralizations; however, it is unclear whether the etiology of twinkling is the same as for kidney stones.Approach.In this study, five cholesterol, calcium phosphate, and uric acid crystals were grownin vitroand imaged in Doppler mode with a research ultrasound system and L7-4 transducer in water. To evaluate the influence of pressure on twinkling, the same crystals were imaged in a high-pressure chamber. Then, the effect of surface tension on twinkling was evaluated by imaging crystals in different concentrations of surfactant (1%, 2%, 3%, 4%) and ethanol (10%, 30%, 50%, 70%), artificial urine, bovine blood, and a tissue-mimicking phantom.Main results. Results showed that all crystals twinkled in water, with cholesterol twinkling significantly more than calcium phosphate and uric acid. When the ambient pressure was increased, twinkling disappeared for all tested crystals when pressures reached 7 MPa (absolute) and reappeared when returned to ambient pressure (0.1 MPa). Similarly, twinkling across all crystals decreased with surface tension when imaged in the surfactant and ethanol (statistically significant when surface tension <22 mN m-1) and decreased in blood (surface tension = 52.7 mN m-1) but was unaffected by artificial urine (similar surface tension to water). In the tissue-mimicking phantom, twinkling increased for cholesterol and calcium phosphate crystals with no change observed in uric acid crystals.Significance.Overall, these results support the theory that bubbles are present on crystals and cause twinkling, which could be leveraged to improve twinkling for the detection of other pathological mineralizations.
Collapse
Affiliation(s)
- Eric Rokni
- Graduate Program in Acoustics, The Pennsylvania State University, 201E Applied Science Building, University Park, PA 16802, United States of America
| | - Julianna C Simon
- Graduate Program in Acoustics, The Pennsylvania State University, 201E Applied Science Building, University Park, PA 16802, United States of America
| |
Collapse
|
4
|
Rokni E, Zinck S, Simon JC. Evaluation of Stone Features That Cause the Color Doppler Ultrasound Twinkling Artifact. ULTRASOUND IN MEDICINE & BIOLOGY 2021; 47:1310-1318. [PMID: 33602553 DOI: 10.1016/j.ultrasmedbio.2021.01.016] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2020] [Revised: 01/13/2021] [Accepted: 01/13/2021] [Indexed: 06/12/2023]
Abstract
The color Doppler ultrasound twinkling artifact is a rapid color shift that appears on 43%-96% of kidney stones. Surface microbubbles on kidney stones are theorized to cause twinkling as exposure to elevated static pressures of 0.41-1.13 MPa (approximately 0.5-1 times diagnostic ultrasound pressure and 5-10 times ambient pressure) reduced twinkling. However, it is unclear what external and internal stone features support bubbles. Thirteen ex vivo kidney stones were scanned with color Doppler ultrasound at 2.5, 5 and 18.5 MHz. Select stones were imaged with environmental scanning electron microscopy or underwater micro-computed tomography to evaluate features that may cause twinkling. Results revealed that the lower frequencies produced larger volumes of twinkling. Condensation first occurred in the smallest (∼1 µm diameter) surface pores and may be indicative of where bubbles form. Gas pockets were seen inside two of three tested stones that may contribute to twinkling. Overall, these results provide evidence of cavity structures both externally and internally and their correlation to the twinkling artifact. This indicates that microbubbles may be present on and within kidney stones and may contribute to the twinkling artifact.
Collapse
Affiliation(s)
- Eric Rokni
- Graduate Program in Acoustics, The Pennsylvania State University, University Park, Pennsylvania, USA.
| | - Scott Zinck
- Graduate Program in Acoustics, The Pennsylvania State University, University Park, Pennsylvania, USA
| | - Julianna C Simon
- Graduate Program in Acoustics, The Pennsylvania State University, University Park, Pennsylvania, USA
| |
Collapse
|
5
|
Detection of Microcalcifications using the Ultrasound Doppler Twinkling Artifact. BIOMEDICAL ENGINEERING 2020. [DOI: 10.1007/s10527-020-09998-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
|
6
|
Simon JC, Holm JR, Thiel J, Dunmire B, Cunitz BW, Bailey MR. Evidence of Microbubbles on Kidney Stones in Humans. ULTRASOUND IN MEDICINE & BIOLOGY 2020; 46:1802-1807. [PMID: 32245546 PMCID: PMC7293935 DOI: 10.1016/j.ultrasmedbio.2020.02.010] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2019] [Revised: 01/17/2020] [Accepted: 02/16/2020] [Indexed: 06/11/2023]
Abstract
The color Doppler ultrasound twinkling artifact has been found to improve detection of kidney stones with ultrasound; however, it appears on only ∼60% of stones. Evidence from ex vivo kidney stones suggests twinkling arises from microbubbles stabilized in crevices on the stone surface. Yet it is unknown whether these bubbles are present on stones in humans. Here, we used a research ultrasound system to quantify twinkling in humans with kidney stones in a hyperbaric chamber. Eight human patients with non-obstructive kidney stones previously observed to twinkle were exposed to a maximum pressure of 4 atmospheres absolute (ATA) while breathing air, except during the 10-min pause at 1.6 ATA and while the pressure decreased to 1 ATA, during which patients breathed oxygen to minimize the risk of decompression sickness. A paired one-way t-test was used to compare the mean twinkle power at each pressure pause with baseline twinkling, with p < 0.05 considered to indicate significance. Results revealed that exposure to 3 and 4 ATA of pressure significantly reduced twinkle power by averages of 35% and 39%, respectively, in 7 patients (p = 0.04); data from the eighth patient were excluded because of corruption. This study supports the theory that microbubbles are present on kidney stones in humans.
Collapse
Affiliation(s)
- Julianna C Simon
- Center for Industrial and Medical Ultrasound, Applied Physics Laboratory, University of Washington, Seattle, Washington, USA; Graduate Program in Acoustics, Pennsylvania State University, University Park, Pennsylvania, USA.
| | - James R Holm
- Center for Hyperbaric Medicine, Virginia Mason Medical Center, Seattle, Washington, USA
| | - Jeffrey Thiel
- Center for Industrial and Medical Ultrasound, Applied Physics Laboratory, University of Washington, Seattle, Washington, USA
| | - Barbrina Dunmire
- Center for Industrial and Medical Ultrasound, Applied Physics Laboratory, University of Washington, Seattle, Washington, USA
| | - Bryan W Cunitz
- Center for Industrial and Medical Ultrasound, Applied Physics Laboratory, University of Washington, Seattle, Washington, USA
| | - Michael R Bailey
- Center for Industrial and Medical Ultrasound, Applied Physics Laboratory, University of Washington, Seattle, Washington, USA
| |
Collapse
|
7
|
Kang J, Han K, Kim KS, Jang WS, Kim MJ, Yoo Y. 3D microcalcification detection using a color Doppler twinkling artifact with optimized transmit conditions: Preliminary results. Med Phys 2020; 47:6171-6178. [PMID: 32563207 DOI: 10.1002/mp.14342] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2019] [Revised: 06/08/2020] [Accepted: 06/08/2020] [Indexed: 11/09/2022] Open
Abstract
PURPOSE Mammography is the only method that has been proven to detect breast microcalcifications (MCs), but the sensitivity of mammography varies according to breast density. This paper proposes an ultrasound (US) color Doppler twinkling artifact (CDTA) method with optimized transmit conditions to identify breast MCs without ionizing radiation. METHODS The transmit conditions for US color Doppler imaging (CDI) were optimized to enhance the sensitivity of the twinkling artifact (TA) that arises from random scattering on rough surfaces of breast MCs. To validate the proposed breast MC detection method, a chicken breast phantom with MC particles (groups of particles <400 μ m and <240 μ m ) was fabricated and scanned by a digital mammography system and an US research platform by an L11-5v linear array probe with a three-dimensional (3D) motion tracking system. RESULTS From the phantom experiment, the proposed 3D CDTA imaging method with optimized transmit conditions (i.e., a center frequency of 5.0 MHz, an f-number of 1.3, and a peak negative pressure of 1.83 MPa) successfully detected all 16 MC particles, comparable to detection with mammography. For a human breast surgical specimen in the ex vivo study, all 10 MC clusters, marked by a radiologist on the mammogram, were identified with the proposed 3D CDTA imaging method. CONCLUSIONS In the phantom and ex vivo breast specimen studies, the proposed 3D CDTA imaging method successfully detected MCs, and the spatial localization was highly correlated with the mammogram results. These results indicate that the proposed 3D CDTA imaging method has great potential for the detection of MCs without ionizing radiation.
Collapse
Affiliation(s)
- Jinbum Kang
- Department of Electronic Engineering, Sogang University, Seoul, 04107, Korea
| | - Kanghee Han
- Department of Electronic Engineering, Sogang University, Seoul, 04107, Korea
| | - Kang-Sik Kim
- Department of Health & Medical Equipment, Samsung Electronics Co. Ltd., Suwon, 16678, Korea
| | - Won Seuk Jang
- Department of Medical Engineering, Yonsei University College of Medicine, Seoul, 03722, Korea
| | - Min Jung Kim
- Department of Radiology, Yonsei University College of Medicine, Seoul, 03722, Korea
| | - Yangmo Yoo
- Department of Electronic Engineering, Sogang University, Seoul, 04107, Korea.,Department of Biomedical Engineering, Sogang University, Seoul, 04107, Korea
| |
Collapse
|
8
|
Bacha R, Gilani SA, Manzoor I. Relation of Color Doppler Twinkling Artifact and Scale or Pulse Repetition Frequency. J Med Ultrasound 2019; 27:13-18. [PMID: 31031530 PMCID: PMC6445033 DOI: 10.4103/jmu.jmu_129_18] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2017] [Accepted: 03/02/2018] [Indexed: 11/25/2022] Open
Abstract
OBJECTIVE The aim of this study is to determine the effect of scale/pulse repetition frequency (PRF) on the appearance of color Doppler twinkling artifact. MATERIALS AND METHODS We commenced this cross-sectional study for 20 months from November 2014 to July 2016. During routine ultrasound examination, we observed multiple case of twinkling artifact produced by renal stones, calcifications in the thyroid nodules, bony fragments and intestinal gases, etc., We observed twinkling artifact with low- and high-PRF settings in 500 different structures. A total of 500 other structures were included wherein there was no Doppler twinkling artifact produced by them, with usual optimum PRF settings. These structures were also evaluated with low- and high-PRF to determine the effect of PRF on twinkling artifact effectively. All the patients were examined according to the AIUM guideline for appropriate examination protocol. Data were collected from the observation of twinkling artifact with low- and high-PRF/scale and evaluated with the help of IBM SPSS 24 package, the results were summarized as follow. RESULTS Change in scale/PRF could not affect the twinkling artifact. The twinkling artifact observed with low-PRF was the same as seen with high-PRF. There was a significant agreement between low- and high-PRF in the production of color twinkling artifact. The kappa value of agreement was estimated as 0.96, whereas the Pearson's correlation was significant with the value of 0.001. Same twinkling artifact was created with low- and high-PRF, with no significant variation. CONCLUSION Twinkling artifact is independent of PRF/Scale.
Collapse
Affiliation(s)
- Raham Bacha
- Department of University Institute of Radiological Sciences and Medical Imaging Technologies (UIRSMIT), Faculty of Allied Health Sciences (FAHS), University of Lahore, Pakistan
- Gilani Ultrasound Center, Afro-Asian Institute, Lahore, Pakistan
| | - Syed Amir Gilani
- Department of University Institute of Radiological Sciences and Medical Imaging Technologies (UIRSMIT), Faculty of Allied Health Sciences (FAHS), University of Lahore, Pakistan
- Gilani Ultrasound Center, Afro-Asian Institute, Lahore, Pakistan
| | - Iqra Manzoor
- Department of University Institute of Radiological Sciences and Medical Imaging Technologies (UIRSMIT), Faculty of Allied Health Sciences (FAHS), University of Lahore, Pakistan
| |
Collapse
|
9
|
Jamzad A, Setarehdan SK. Noninvasive Prediction of Renal Stone Surface Irregularities by Numerical Analysis of the Color Doppler Twinkling Artifact: An Ex Vivo Study. JOURNAL OF ULTRASOUND IN MEDICINE : OFFICIAL JOURNAL OF THE AMERICAN INSTITUTE OF ULTRASOUND IN MEDICINE 2018; 37:1211-1224. [PMID: 29086450 DOI: 10.1002/jum.14465] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/16/2017] [Revised: 07/16/2017] [Accepted: 08/07/2017] [Indexed: 06/07/2023]
Abstract
OBJECTIVES The physical structures of renal stones are highly correlated with their breakability. Noninvasive estimation of stone roughness will be beneficial for management. The intensity of the twinkling artifact appearing at the site of renal stones on Doppler ultrasound imaging is also influenced by the stone's roughness level. This article proposes a quantitative method for roughness prediction of ex vivo renal stones based on a twinkling analysis of their color Doppler images. METHODS Twenty surgically removed renal stones were first spatially modeled by an optical method, and 12 standard roughness measures were extracted from them. Stones were then embedded in an agar-based phantom and Doppler imaged with a calibrated ultrasound system. The images were preprocessed, and 11 twinkling intensities were measured numerically. The twinkling data along with the roughness labels were then analyzed by multiple linear regressions, and finally, a linear roughness predictor was trained for renal stones. RESULTS The core height measure of roughness had the best linear fit to the twinkling data among other roughness parameters. The results of the multiple linear regression analysis indicated a strong linear relationship between twinkling data and stones' roughness, with an R2 value of 83.29% and high statistical significance of F(11,868) = 393.36 and P < .001. CONCLUSIONS It was possible to predict the core roughness of renal stones using the proposed method and the twinkling artifact data acquired from the color Doppler images ex vivo.
Collapse
Affiliation(s)
- Amoon Jamzad
- Control and Intelligent Processing Center of Excellence, School of Electrical and Computer Engineering, College of Engineering, University of Tehran, Tehran, Iran
| | - Seyed Kamaledin Setarehdan
- Control and Intelligent Processing Center of Excellence, School of Electrical and Computer Engineering, College of Engineering, University of Tehran, Tehran, Iran
| |
Collapse
|
10
|
Simon JC, Sapozhnikov OA, Kreider W, Breshock M, Williams JC, Bailey MR. The role of trapped bubbles in kidney stone detection with the color Doppler ultrasound twinkling artifact. Phys Med Biol 2018; 63:025011. [PMID: 29131810 DOI: 10.1088/1361-6560/aa9a2f] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The color Doppler ultrasound twinkling artifact, which highlights kidney stones with rapidly changing color, has the potential to improve stone detection; however, its inconsistent appearance has limited its clinical utility. Recently, it was proposed stable crevice bubbles on the kidney stone surface cause twinkling; however, the hypothesis is not fully accepted because the bubbles have not been directly observed. In this paper, the micron or submicron-sized bubbles predicted by the crevice bubble hypothesis are enlarged in kidney stones of five primary compositions by exposure to acoustic rarefaction pulses or hypobaric static pressures in order to simultaneously capture their appearance by high-speed photography and ultrasound imaging. On filming stones that twinkle, consecutive rarefaction pulses from a lithotripter caused some bubbles to reproducibly grow from specific locations on the stone surface, suggesting the presence of pre-existing crevice bubbles. Hyperbaric and hypobaric static pressures were found to modify the twinkling artifact; however, the simple expectation that hyperbaric exposures reduce and hypobaric pressures increase twinkling by shrinking and enlarging bubbles, respectively, largely held for rough-surfaced stones but was inadequate for smoother stones. Twinkling was found to increase or decrease in response to elevated static pressure on smooth stones, perhaps because of the compression of internal voids. These results support the crevice bubble hypothesis of twinkling and suggest the kidney stone crevices that give rise to the twinkling phenomenon may be internal as well as external.
Collapse
Affiliation(s)
- Julianna C Simon
- Center for Industrial and Medical Ultrasound, Applied Physics Laboratory, University of Washington, 1013 NE 40th St., Seattle, WA 98105, United States of America. Department of Mechanical Engineering, University of Washington, Stevens Way, Box 352600, Seattle, WA 98195, United States of America. Current address: Graduate Program in Acoustics, The Pennsylvania State University, 201E Applied Science Building, University Park, PA 16802, United States of America. Author to whom any correspondence should be addressed
| | | | | | | | | | | |
Collapse
|
11
|
The value of the twinkling artefact for the diagnosis of sialolithiasis of the large salivary glands. The Journal of Laryngology & Otology 2017; 132:162-167. [DOI: 10.1017/s002221511700250x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
AbstractObjective:The imaging of stones in the salivary glands and ducts poses a challenge, even to experienced ultrasound examiners. This study investigated whether the ‘twinkling artefact’, which occurs at internal calcific foci during Doppler ultrasound examinations, is useful for detecting salivary gland stones.Methods:In a model test, 20 salivary stones were analysedin vitro, via Doppler ultrasound, with regard to their representability and the triggering of the twinkling artefact. In a follow-up study, 28 patients with sialolithiasis and food-related large salivary gland swellings were examined, using both power and colour Doppler modes, with regard to the twinkling artefact. All ultrasound examinations were performed by an experienced examiner and retrospectively graded by two experienced sonographers.Results:All stones could reliably be detected using the twinkling artefact in the model test. Twenty-seven of 28 salivary stones (96 per cent) also showed twinklingin vivo, during patient assessment. The power Doppler mode showed a significantly higher intensity level of twinkling than the colour Doppler mode (p< 0.0001).Conclusion:The twinkling artefact is a very reliable sign for the diagnosis of sialolithiasis. Power Doppler is superior to colour Doppler for detection of the twinkling artefact.
Collapse
|
12
|
Cunitz BW, Dunmire B, Bailey MR. Characterizing the Acoustic Output of an Ultrasonic Propulsion Device for Urinary Stones. IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL 2017; 64:1818-1827. [PMID: 28981413 PMCID: PMC5733808 DOI: 10.1109/tuffc.2017.2758647] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
A noninvasive ultrasound (US) system to facilitate the passage of small kidney stones has been developed. The device incorporates a software-based US platform programmed with brightness mode and Doppler for visualizing stones, plus long duration focused pulses for repositioning stones using the same transducer. This paper characterizes the acoustic outputs of the ultrasonic propulsion device. Though the application and outputs are unique, measurements were performed based on the regulatory standards for both diagnostic US and extracorporeal lithotripters. The extended length of the pulse, time varying pressure output over the pulse, the use of focused targeting, and the need to regulate the output at shallow depths, however, required modifications to the traditional acoustic measurement methods. Output parameters included spatial-peak intensities, mechanical index (MI), thermal index, pulse energy, focal geometry, and target accuracy. The imaging and Doppler operating modes of the system meet the Food and Drug Administration acoustic power and intensity limits for diagnostic US device. Push mode operates at a maximum MI of 2.2, which is above the limit of 1.9 for diagnostic US, but well below any lithotripsy device and an ISPTA of 548 mW/cm2, which is below the 720-mW/cm2 limit for diagnostic US.
Collapse
|
13
|
Cunitz BW, Harper JD, Sorensen MD, Haider YA, Thiel J, May PC, Liu Z, Bailey MR, Dunmire B, Bruce M. Quantification of Renal Stone Contrast with Ultrasound in Human Subjects. J Endourol 2017; 31:1123-1130. [PMID: 28847171 DOI: 10.1089/end.2017.0404] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
PURPOSE Greater visual contrast between calculi and tissue would improve ultrasound (US) imaging of urolithiasis and potentially expand clinical use. The color Doppler twinkling artifact has been suggested to provide enhanced contrast of stones compared with brightness mode (B-mode) imaging, but results are variable. This work provides the first quantitative measure of stone contrast in humans for B-mode and color Doppler mode, forming the basis to improve US for the detection of stones. MATERIALS AND METHODS Using a research ultrasound system, B-mode imaging was tuned for detecting stones by applying a single transmit angle and reduced signal compression. Stone twinkling with color Doppler was tuned by using low-frequency transmit pulses, longer pulse durations, and a high-pulse repetition frequency. Data were captured from 32 subjects, with 297 B-mode and Doppler images analyzed from 21 subjects exhibiting twinkling signals. The signal to clutter ratio (i.e., stone to background tissue) (SCR) was used to compare the contrast of a stone on B-mode with color Doppler, and the contrast between stone twinkling and blood-flow signals within the kidney. RESULTS The stone was the brightest object in only 54% of B-mode images and 100% of Doppler images containing stone twinkling. On average, stones were isoechoic with the tissue clutter on B-mode (SCR = 0 dB). Stone twinkling averaged 37 times greater contrast than B-mode (16 dB, p < 0.0001) and 3.5 times greater contrast than blood-flow signals (5.5 dB, p = 0.088). CONCLUSIONS This study provides the first quantitative measure of US stone to tissue contrast in humans. Stone twinkling contrast is significantly greater than the contrast of a stone on B-mode. There was also a trend of stone twinkling signals having greater contrast than blood-flow signals in the kidney. Dedicated optimization of B-mode and color Doppler stone imaging could improve US detection of stones.
Collapse
Affiliation(s)
- Bryan W Cunitz
- 1 Center for Industrial and Medical Ultrasound, Applied Physics Laboratory, University of Washington , Seattle, Washington
| | - Jonathan D Harper
- 2 Department of Urology, University of Washington School of Medicine , Seattle, Washington
| | - Mathew D Sorensen
- 2 Department of Urology, University of Washington School of Medicine , Seattle, Washington.,3 Division of Urology, Department of Veteran Affairs Medical Center , Seattle, Washington
| | - Yasser A Haider
- 1 Center for Industrial and Medical Ultrasound, Applied Physics Laboratory, University of Washington , Seattle, Washington
| | - Jeff Thiel
- 4 Department of Radiology, University of Washington School of Medicine , Seattle, Washington
| | - Philip C May
- 2 Department of Urology, University of Washington School of Medicine , Seattle, Washington
| | - Ziyue Liu
- 5 Department of Biostatistics, Indiana University-Purdue University Indianapolis , Indianapolis, Indiana
| | - Michael R Bailey
- 1 Center for Industrial and Medical Ultrasound, Applied Physics Laboratory, University of Washington , Seattle, Washington
| | - Barbrina Dunmire
- 1 Center for Industrial and Medical Ultrasound, Applied Physics Laboratory, University of Washington , Seattle, Washington
| | - Matthew Bruce
- 1 Center for Industrial and Medical Ultrasound, Applied Physics Laboratory, University of Washington , Seattle, Washington
| |
Collapse
|
14
|
Shang M, Sun X, Liu Q, Li J, Shi D, Ning S, Cheng L. Quantitative Evaluation of the Effects of Urinary Stone Composition and Size on Color Doppler Twinkling Artifact: A Phantom Study. JOURNAL OF ULTRASOUND IN MEDICINE : OFFICIAL JOURNAL OF THE AMERICAN INSTITUTE OF ULTRASOUND IN MEDICINE 2017; 36:733-740. [PMID: 28039937 DOI: 10.7863/ultra.16.01039] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/14/2016] [Accepted: 07/01/2016] [Indexed: 06/06/2023]
Abstract
OBJECTIVES The present study was conducted to quantitatively evaluate the influence of urinary stone composition and size on color Doppler twinkling artifact. METHODS Calcium oxalate monohydrate (COM), apatite, L-cystine, and uric acid (UA) stone phantoms with 10 different sizes were prepared artificially and embedded in the renal sinus of porcine kidneys in vitro. Color Doppler ultrasound scanning was performed on the phantoms and TA pictures were recorded. The length of the twinkling artifact (TAL) and width of twinkling artifact (TAW) were measured. The color pixels representing twinkling artifact intensity (TAI) were calculated. RESULTS There were significant differences in the appearance of TA among the four types of stone phantoms (P < .05). The mean value of TAI of UA stones was the strongest, followed by L-cystine, apatite, and COM. A significantly positive correlation was found between TA and stone size (rTAI = 0.801, rTAL = 0.838, rTAW = 0.584, respectively; P <.05). CONCLUSIONS The appearance of TA in association with urinary stones is highly dependent on stone composition and size.
Collapse
Affiliation(s)
- Mengmeng Shang
- Department of Ultrasound, Qilu Hospital, Shandong University, Jinan, China
| | - Xiao Sun
- Department of Ultrasound, Qilu Hospital, Shandong University, Jinan, China
| | - Qing Liu
- Department of Ultrasound, Qilu Hospital, Shandong University, Jinan, China
| | - Jie Li
- Department of Ultrasound, Qilu Hospital, Shandong University, Jinan, China
| | - Dandan Shi
- Department of Ultrasound, Qilu Hospital, Shandong University, Jinan, China
| | - Song Ning
- Department of Ultrasound, Qilu Hospital, Shandong University, Jinan, China
| | - Lin Cheng
- Department of Ultrasound, Qilu Hospital, Shandong University, Jinan, China
| |
Collapse
|
15
|
Mi J, Li J, Zhang Q, Wang X, Liu H, Cao Y, Liu X, Sun X, Shang M, Liu Q. Combining ultrasonography and noncontrast helical computerized tomography to evaluate Holmium laser lithotripsy. Medicine (Baltimore) 2016; 95:e5564. [PMID: 27930563 PMCID: PMC5266035 DOI: 10.1097/md.0000000000005564] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
The purpose of the study was to establish a mathematical model for correlating the combination of ultrasonography and noncontrast helical computerized tomography (NCHCT) with the total energy of Holmium laser lithotripsy.In this study, from March 2013 to February 2014, 180 patients with single urinary calculus were examined using ultrasonography and NCHCT before Holmium laser lithotripsy. The calculus location and size, acoustic shadowing (AS) level, twinkling artifact intensity (TAI), and CT value were all documented. The total energy of lithotripsy (TEL) and the calculus composition were also recorded postoperatively. Data were analyzed using Spearman's rank correlation coefficient, with the SPSS 17.0 software package. Multiple linear regression was also used for further statistical analysis.A significant difference in the TEL was observed between renal calculi and ureteral calculi (r = -0.565, P < 0.001), and there was a strong correlation between the calculus size and the TEL (r = 0.675, P < 0.001). The difference in the TEL between the calculi with and without AS was highly significant (r = 0.325, P < 0.001). The CT value of the calculi was significantly correlated with the TEL (r = 0.386, P < 0.001). A correlation between the TAI and TEL was also observed (r = 0.391, P < 0.001). Multiple linear regression analysis revealed that the location, size, and TAI of the calculi were related to the TEL, and the location and size were statistically significant predictors (adjusted r = 0.498, P < 0.001).A mathematical model correlating the combination of ultrasonography and NCHCT with TEL was established; this model may provide a foundation to guide the use of energy in Holmium laser lithotripsy. The TEL can be estimated by the location, size, and TAI of the calculus.
Collapse
Affiliation(s)
- Jia Mi
- Qilu Hospital of Shandong University
- Department of Ultrasound, Shandong Traffic Hospital
| | - Jie Li
- Department of Ultrasound, Qilu Hospital of Shandong University, Jinan, Shandong, China
| | - Qinglu Zhang
- Department of Ultrasound, Shandong Traffic Hospital
| | - Xing Wang
- Department of Ultrasound, Shandong Traffic Hospital
| | - Hongyu Liu
- Department of Ultrasound, Shandong Traffic Hospital
| | - Yanlu Cao
- Department of Microbiology and Immunology, East Carolina University Brody School of Medicine, Greenville, NC
| | - Xiaoyan Liu
- Department of Pulmonology, Peking Union Medical College Hospital, Peking Union Medical College, Chinese Academy of Medical Sciences, Beijing, China
| | - Xiao Sun
- Department of Ultrasound, Qilu Hospital of Shandong University, Jinan, Shandong, China
| | - Mengmeng Shang
- Department of Ultrasound, Qilu Hospital of Shandong University, Jinan, Shandong, China
| | - Qing Liu
- Department of Ultrasound, Qilu Hospital of Shandong University, Jinan, Shandong, China
| |
Collapse
|
16
|
Sen V, Imamoglu C, Kucukturkmen I, Degirmenci T, Bozkurt IH, Yonguc T, Aydogdu O, Gunlusoy B. Can Doppler ultrasonography twinkling artifact be used as an alternative imaging modality to non-contrast-enhanced computed tomography in patients with ureteral stones? A prospective clinical study. Urolithiasis 2016; 45:215-219. [DOI: 10.1007/s00240-016-0891-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2016] [Accepted: 05/05/2016] [Indexed: 11/25/2022]
|
17
|
Ozan E, Atac GK, Gundogdu S. Twinkling artifact on color Doppler ultrasound: an advantage or a pitfall? J Med Ultrason (2001) 2016; 43:361-71. [PMID: 27126510 DOI: 10.1007/s10396-016-0715-z] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2015] [Accepted: 04/04/2016] [Indexed: 12/19/2022]
Abstract
The twinkling artifact (TA) or color comet-tail artifact is characterized by a rapidly changing mixture of red and blue color Doppler signals. Even though many diseases and clinical conditions have been shown to produce this artifact, its source is not clearly understood yet. The TA may provide additional information to gray-scale ultrasound findings in several clinical situations. However, there may be pitfalls to keep in mind. We must first be aware of the TA to benefit from the advantages and avoid the pitfalls. In this review, we aim to give practicing radiologists an overview of the mechanisms and clinical applications of the TA by illustrating sample cases we have encountered.
Collapse
Affiliation(s)
- Ebru Ozan
- Department of Radiology, Ufuk University School of Medicine, Dr. Ridvan Ege Training and Research Hospital, Mevlana Bulvarı (Konya Yolu) No: 86-88, 06520, Balgat, Ankara, Turkey.
| | - Gokce Kaan Atac
- Department of Radiology, Ufuk University School of Medicine, Dr. Ridvan Ege Training and Research Hospital, Mevlana Bulvarı (Konya Yolu) No: 86-88, 06520, Balgat, Ankara, Turkey
| | - Sadi Gundogdu
- Department of Radiology, Ufuk University School of Medicine, Dr. Ridvan Ege Training and Research Hospital, Mevlana Bulvarı (Konya Yolu) No: 86-88, 06520, Balgat, Ankara, Turkey
| |
Collapse
|
18
|
|
19
|
Bailey M, Cunitz B, Dunmire B, Paun M, Lee F, Ross S, Lingeman J, Coburn M, Wessells H, Sorensen M, Harper J. Ultrasonic propulsion of kidney stones: preliminary results of human feasibility study. IEEE INTERNATIONAL ULTRASONICS SYMPOSIUM : [PROCEEDINGS]. IEEE INTERNATIONAL ULTRASONICS SYMPOSIUM 2014. [PMID: 26203347 DOI: 10.1109/ultsym.2014.0126] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
One in 11 Americans has experienced kidney stones, with a 50% average recurrence rate within 5-10 years. Ultrasonic propulsion (UP) offers a potential method to expel small stones or residual fragments before they become a recurrent problem. Reported here are preliminary findings from the first investigational use of UP in humans. The device uses a Verasonics ultrasound engine and Philips HDI C5-2 probe to generate real-time B-mode imaging and targeted "push" pulses on demand. There are three arms of the study: de novo stones, post-lithotripsy fragments, and the preoperative setting. A pain questionnaire is completed prior to and following the study. Movement is classified based on extent. Patients are followed for 90 days. Ten subjects have been treated to date: three de novo, five post-lithotripsy, and two preoperative. None of the subjects reported pain associated with the treatment or a treatment related adverse event, beyond the normal discomfort of passing a stone. At least one stone was moved in all subjects. Three of five post-lithotripsy subjects passed a single or multiple stones within 1-2 weeks following treatment; one subject passed two (1-2 mm) fragments before leaving clinic. In the pre-operative studies we successfully moved 7 - 8 mm stones. In four subjects, UP revealed multiple stone fragments where the clinical image and initial ultrasound examination indicated a single large stone.
Collapse
Affiliation(s)
- Michael Bailey
- Center for Industrial and Medical Ultrasound, Applied Physics Laboratory, University of Washington, Seattle, USA
| | - Bryan Cunitz
- Center for Industrial and Medical Ultrasound, Applied Physics Laboratory, University of Washington, Seattle, USA
| | - Barbrina Dunmire
- Center for Industrial and Medical Ultrasound, Applied Physics Laboratory, University of Washington, Seattle, USA
| | - Marla Paun
- Center for Industrial and Medical Ultrasound, Applied Physics Laboratory, University of Washington, Seattle, USA
| | - Franklin Lee
- Department of Urology, University of Washington, Seattle, USA
| | - Susan Ross
- Department of Urology, University of Washington, Seattle, USA
| | - James Lingeman
- Department of Urology, Indiana University School of Medicine, Indianapolis, USA
| | - Michael Coburn
- Department of Urology, Baylor College of Medicine, Houston, USA
| | - Hunter Wessells
- Department of Urology, University of Washington, Seattle, USA
| | - Mathew Sorensen
- Department of Urology, University of Washington, Seattle, USA ; Division of Urology, Puget Sound Veteran Affairs Medical Center, Seattle, USA
| | - Jonathan Harper
- Department of Urology, University of Washington, Seattle, USA
| |
Collapse
|
20
|
Choi MJ, Cho CH, Kang G, Yang J. Color Doppler twinkling artifact: Possible mechanisms and clinical potential. Biomed Eng Lett 2014. [DOI: 10.1007/s13534-014-0124-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
|
21
|
Jamzad A, Setarehdan SK. A novel approach for quantification and analysis of the color Doppler twinkling artifact with application in noninvasive surface roughness characterization: an in vitro phantom study. JOURNAL OF ULTRASOUND IN MEDICINE : OFFICIAL JOURNAL OF THE AMERICAN INSTITUTE OF ULTRASOUND IN MEDICINE 2014; 33:597-610. [PMID: 24658939 DOI: 10.7863/ultra.33.4.597] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
OBJECTIVES The twinkling artifact is an undesired phenomenon within color Doppler sonograms that usually appears at the site of internal calcifications. Since the appearance of the twinkling artifact is correlated with the roughness of the calculi, noninvasive roughness estimation of the internal stones may be considered as a potential twinkling artifact application. This article proposes a novel quantitative approach for measurement and analysis of twinkling artifact data for roughness estimation. METHODS A phantom was developed with 7 quantified levels of roughness. The Doppler system was initially calibrated by the proposed procedure to facilitate the analysis. A total of 1050 twinkling artifact images were acquired from the phantom, and 32 novel numerical measures were introduced and computed for each image. The measures were then ranked on the basis of roughness quantification ability using different methods. The performance of the proposed twinkling artifact-based surface roughness quantification method was finally investigated for different combinations of features and classifiers. RESULTS Eleven features were shown to be the most efficient numerical twinkling artifact measures in roughness characterization. The linear classifier outperformed other methods for twinkling artifact classification. The pixel count measures produced better results among the other categories. The sequential selection method showed higher accuracy than other individual rankings. The best roughness recognition average accuracy of 98.33% was obtained by the first 5 principle components and the linear classifier. CONCLUSIONS The proposed twinkling artifact analysis method could recognize the phantom surface roughness with average accuracy of 98.33%. This method may also be applicable for noninvasive calculi characterization in treatment management.
Collapse
Affiliation(s)
- Amoon Jamzad
- Control and Intelligent Processing Center of Excellence, School of Electrical and Computer Engineering, College of Engineering, University of Tehran, North Kargar Street, Tehran 14395-515, Iran.
| | | |
Collapse
|
22
|
Tsujimoto F. Microcalcifications in the breast detected by a color Doppler method using twinkling artifacts: some important discussions based on clinical cases and experiments with a new ultrasound modality called multidetector-ultrasonography (MD-US). J Med Ultrason (2001) 2013; 41:99-108. [PMID: 27277641 DOI: 10.1007/s10396-013-0476-x] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2012] [Accepted: 05/31/2013] [Indexed: 11/25/2022]
Abstract
The twinkling artifact is well known as a color Doppler artifact but it is still an unresolved phenomenon [Rahmouni et al., Radiology 1996;199:269-271 ; Atan et al., Astas Urol Esp 2001;35:396-402; Kamaya et al., AJR 2003;80:215-222]. Many factors affect the appearance of the twinkling artifact, such as the surface roughness of stones creating multiple reflections and a form of intrinsic noise known as clock jitter within the Doppler circuitry of the ultrasound equipment. However, no studies have reported on the twinkling artifact of breast microcalcifications. While considering these premises, I detected microcalcifications in the breast using twinkling artifacts that could not be detected on B-mode imaging. The twinkling artifact is a well-defined but not well-understood phenomenon that may assist in the detection of calcified foci. The phenomenon of the twinkling artifact is discussed here with regard to prospectively and retrospectively studied cases including experiments with a new ultrasound modality called multidetector-ultrasonography (MD-US). MD-US using detectability of the twinkling artifact in microcalcifications of the breast may play an important role in breast screening.
Collapse
Affiliation(s)
- Fumio Tsujimoto
- Department of Laboratory Medicine, St. Marianna University School of Medicine, Ultrasound Center, 2-16-1 Sugao, Miyamae-ku, Kawasaki, Kanagawa, 216-8511, Japan.
| |
Collapse
|
23
|
Lu W, Sapozhnikov OA, Bailey MR, Kaczkowski PJ, Crum LA. Evidence for trapped surface bubbles as the cause for the twinkling artifact in ultrasound imaging. ULTRASOUND IN MEDICINE & BIOLOGY 2013; 39:1026-38. [PMID: 23562014 PMCID: PMC3646957 DOI: 10.1016/j.ultrasmedbio.2013.01.011] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/24/2012] [Revised: 01/15/2013] [Accepted: 01/16/2013] [Indexed: 05/05/2023]
Abstract
The mechanism of the twinkling artifact (TA) that occurs during Doppler ultrasound imaging of kidney stones was investigated. The TA expresses itself in Doppler images as time-varying color. To define the TA quantitatively, beam-forming and Doppler processing were performed on raw per channel radio-frequency data collected when imaging human kidney stones in vitro. Suppression of twinkling by an ensemble of computer-generated replicas of a single radio frequency signal demonstrated that the TA arises from variability among the acoustic signals and not from electronic signal capture or processing. This variability was found to be random, and its suppression by elevated static pressure and return when the pressure was released suggest that the presence of bubbles on the stone surface is the mechanism that gives rise to the TA.
Collapse
Affiliation(s)
- Wei Lu
- Center for Industrial and Medical Ultrasound, Applied Physics Laboratory, University of Washington, 1013 NE 40St., Seattle WA 98105
| | - Oleg A. Sapozhnikov
- Center for Industrial and Medical Ultrasound, Applied Physics Laboratory, University of Washington, 1013 NE 40St., Seattle WA 98105
- Department of Acoustics, Physics Faculty, Moscow State University, Leninskie Gory, Moscow 119992, Russia
| | - Michael R. Bailey
- Center for Industrial and Medical Ultrasound, Applied Physics Laboratory, University of Washington, 1013 NE 40St., Seattle WA 98105
| | - Peter J. Kaczkowski
- Center for Industrial and Medical Ultrasound, Applied Physics Laboratory, University of Washington, 1013 NE 40St., Seattle WA 98105
| | - Lawrence A. Crum
- Center for Industrial and Medical Ultrasound, Applied Physics Laboratory, University of Washington, 1013 NE 40St., Seattle WA 98105
| |
Collapse
|
24
|
Clinical Implications and Applications of the Twinkling Sign in Ureteral Calculus: A Preliminary Study. J Urol 2013; 189:2132-5. [DOI: 10.1016/j.juro.2012.11.176] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/29/2012] [Indexed: 11/22/2022]
|