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Oliver AA, Bilgin C, Vercnocke AJ, Carlson KD, Kadirvel R, Guillory RJ, Griebel AJ, Schaffer JE, Dragomir-Daescu D, Kallmes DF. Benchtop proof of concept and comparison of iron- and magnesium-based bioresorbable flow diverters. J Neurosurg 2023; 139:150-156. [PMID: 36681964 PMCID: PMC10824252 DOI: 10.3171/2022.11.jns222213] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2022] [Accepted: 11/04/2022] [Indexed: 12/24/2022]
Abstract
OBJECTIVE Bioresorbable flow diverters (BRFDs) could significantly improve the performance of next-generation flow diverter technology. In the current work, magnesium and iron alloy BRFDs were prototyped and compared in terms of porosity/pore density, radial strength, flow diversion functionality, and resorption kinetics to offer insights into selecting the best available bioresorbable metal candidate for the BRFD application. METHODS BRFDs were constructed with braided wires made from alloys of magnesium (MgBRFD) or iron (FeBRFD). Pore density and crush resistance force were measured using established methods. BRFDs were deployed in silicone aneurysm models attached to flow loops to investigate flow diversion functionality and resorption kinetics in a simulated physiological environment. RESULTS The FeBRFD exhibited higher pore density (9.9 vs 4.3 pores/mm2) and crush resistance force (0.69 ± 0.05 vs 0.53 ± 0.05 N/cm, p = 0.0765, n = 3 per group) than the MgBRFD, although both crush resistances were within the range previously reported for FDA-approved flow diverters. The FeBRFD demonstrated greater flow diversion functionality than the MgBRFD, with significantly higher values of established flow diversion metrics (mean transit time 159.6 ± 11.9 vs 110.9 ± 1.6, p = 0.015; inverse washout slope 192.5 ± 9.0 vs 116.5 ± 1.5, p = 0.001; n = 3 per group; both metrics expressed as a percentage of the control condition). Last, the FeBRFD was able to maintain its braided structure for > 12 weeks, whereas the MgBRFD was almost completely resorbed after 5 weeks. CONCLUSIONS The results of this study demonstrated the ability to manufacture BRFDs with magnesium and iron alloys. The data suggest that the iron alloy is the superior material candidate for the BRFD application due to its higher mechanical strength and lower resorption rate relative to the magnesium alloy.
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Affiliation(s)
- Alexander A. Oliver
- Biomedical Engineering and Physiology, Mayo Clinic Graduate School of Biomedical Sciences, Rochester, Minnesota, USA
- Radiology, Mayo Clinic, Rochester, Minnesota, USA
- Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, USA
| | - Cem Bilgin
- Radiology, Mayo Clinic, Rochester, Minnesota, USA
| | | | - Kent D. Carlson
- Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, USA
| | - Ramanathan Kadirvel
- Radiology, Mayo Clinic, Rochester, Minnesota, USA
- Neurosurgery, Rochester, Minnesota, USA
| | - Roger J Guillory
- Biomedical Engineering, Michigan Technological University, Houghton, Michigan, USA
| | | | | | - Dan Dragomir-Daescu
- Biomedical Engineering and Physiology, Mayo Clinic Graduate School of Biomedical Sciences, Rochester, Minnesota, USA
- Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, USA
| | - David F. Kallmes
- Biomedical Engineering and Physiology, Mayo Clinic Graduate School of Biomedical Sciences, Rochester, Minnesota, USA
- Radiology, Mayo Clinic, Rochester, Minnesota, USA
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Oliver AA, Koons EK, Trester PS, Kleinow JE, Jonsgaard RS, Vercnocke AJ, Bilgin C, Kadirvel R, Leng S, Lu A, Dragomir-Daescu D, Kallmes DF. Medical Imaging Compatibility of Magnesium- and Iron-Based Bioresorbable Flow Diverters. AJNR Am J Neuroradiol 2023; 44:668-674. [PMID: 37169543 PMCID: PMC10249688 DOI: 10.3174/ajnr.a7873] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2023] [Accepted: 04/16/2023] [Indexed: 05/13/2023]
Abstract
BACKGROUND AND PURPOSE Bioresorbable flow diverters are under development to mitigate complications associated with conventional flow-diverter technology. One proposed advantage is the ability to reduce metal-induced artifacts in follow-up medical imaging. In the current work, the medical imaging compatibility of magnesium- and iron-based bioresorbable flow diverters is assessed relative to an FDA-approved control in phantom models. MATERIALS AND METHODS Bioresorbable flow diverters, primarily composed of braided magnesium or antiferromagnetic iron alloy wires, were compared with an FDA-approved control flow diverter. The devices were assessed for MR imaging safety in terms of magnetically induced force and radiofrequency heating using 1.5T, 3T, and 7T field strength clinical scanners. The devices were deployed in phantom models, and metal-induced image artifacts were assessed in the 3 MR imaging scanners and a clinical CT scanner following clinical scan protocols; device visibility was assessed under fluoroscopy. RESULTS The magnesium-based bioresorbable flow diverter, iron-based bioresorbable flow diverter, and the control device all demonstrated MR imaging safety in terms of magnetically induced force and radiofrequency heating at all 3 field strengths. The bioresorbable flow diverters did not elicit excessive MR imaging artifacts at any field strength relative to the control. Furthermore, the bioresorbable flow diverters appeared to reduce blooming artifacts in CT relative to the control. The iron-based bioresorbable flow diverter and control device were visible under standard fluoroscopy. CONCLUSIONS We have demonstrated the baseline medical imaging compatibility of magnesium and antiferromagnetic iron alloy bioresorbable flow diverters. Future work will evaluate the medical imaging characteristics of the bioresorbable flow diverters in large-animal models.
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Affiliation(s)
- A A Oliver
- From the Department of Biomedical Engineering and Physiology (A.A.O., E.K.K., S.L., D.D.-D, D.F.K.), Mayo Clinic Graduate School of Biomedical Sciences, Rochester, Minnesota
- Departments of Radiology (A.A.O., E.K.K., P.S.T., J.E.K., R.S.J., A.J.V., C.B., R.K. S.L., A.L., D.F.K.)
- Physiology and Biomedical Engineering (A.A.O., D.D.-D.)
| | - E K Koons
- From the Department of Biomedical Engineering and Physiology (A.A.O., E.K.K., S.L., D.D.-D, D.F.K.), Mayo Clinic Graduate School of Biomedical Sciences, Rochester, Minnesota
- Departments of Radiology (A.A.O., E.K.K., P.S.T., J.E.K., R.S.J., A.J.V., C.B., R.K. S.L., A.L., D.F.K.)
| | - P S Trester
- Departments of Radiology (A.A.O., E.K.K., P.S.T., J.E.K., R.S.J., A.J.V., C.B., R.K. S.L., A.L., D.F.K.)
| | - J E Kleinow
- Departments of Radiology (A.A.O., E.K.K., P.S.T., J.E.K., R.S.J., A.J.V., C.B., R.K. S.L., A.L., D.F.K.)
| | - R S Jonsgaard
- Departments of Radiology (A.A.O., E.K.K., P.S.T., J.E.K., R.S.J., A.J.V., C.B., R.K. S.L., A.L., D.F.K.)
| | - A J Vercnocke
- Departments of Radiology (A.A.O., E.K.K., P.S.T., J.E.K., R.S.J., A.J.V., C.B., R.K. S.L., A.L., D.F.K.)
| | - C Bilgin
- Departments of Radiology (A.A.O., E.K.K., P.S.T., J.E.K., R.S.J., A.J.V., C.B., R.K. S.L., A.L., D.F.K.)
| | - R Kadirvel
- Departments of Radiology (A.A.O., E.K.K., P.S.T., J.E.K., R.S.J., A.J.V., C.B., R.K. S.L., A.L., D.F.K.)
- Neurosurgery (R.K.), Mayo Clinic, Rochester, Minnesota
| | - S Leng
- From the Department of Biomedical Engineering and Physiology (A.A.O., E.K.K., S.L., D.D.-D, D.F.K.), Mayo Clinic Graduate School of Biomedical Sciences, Rochester, Minnesota
- Departments of Radiology (A.A.O., E.K.K., P.S.T., J.E.K., R.S.J., A.J.V., C.B., R.K. S.L., A.L., D.F.K.)
| | - A Lu
- Departments of Radiology (A.A.O., E.K.K., P.S.T., J.E.K., R.S.J., A.J.V., C.B., R.K. S.L., A.L., D.F.K.)
| | - D Dragomir-Daescu
- From the Department of Biomedical Engineering and Physiology (A.A.O., E.K.K., S.L., D.D.-D, D.F.K.), Mayo Clinic Graduate School of Biomedical Sciences, Rochester, Minnesota
- Physiology and Biomedical Engineering (A.A.O., D.D.-D.)
| | - D F Kallmes
- From the Department of Biomedical Engineering and Physiology (A.A.O., E.K.K., S.L., D.D.-D, D.F.K.), Mayo Clinic Graduate School of Biomedical Sciences, Rochester, Minnesota
- Departments of Radiology (A.A.O., E.K.K., P.S.T., J.E.K., R.S.J., A.J.V., C.B., R.K. S.L., A.L., D.F.K.)
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Hsieh SS, Inoue A, Yalon M, Cook DA, Fidler JL, Gong H, Pillai PS, Vercnocke AJ, Johnson MP, Leng S, Yu L, Holmes DR, Carter RE, McCollough CH, Fletcher JG. A training program to reduce reader search errors for liver metastasis detection in CT. Medical Imaging 2023: Image Perception, Observer Performance, and Technology Assessment 2023; 12467. [PMID: 37064083 PMCID: PMC10099580 DOI: 10.1117/12.2654007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/05/2023]
Abstract
Detection of low contrast liver metastases varies between radiologists. Training may improve performance for lower-performing readers and reduce inter-radiologist variability. We recruited 31 radiologists (15 trainees, 8 non-abdominal staff, and 8 abdominal staff) to participate in four separate reading sessions: pre-test, search training, classification training, and post-test. In the pre-test, each radiologist interpreted 40 liver CT exams containing 91 metastases, circumscribed suspected hepatic metastases while under eye tracker observation, and rated confidence. In search training, radiologists interpreted a separate set of 30 liver CT exams while receiving eye tracker feedback and after coaching to increase use of coronal reformations, interpretation time, and use of liver windows. In classification training, radiologists interpreted up to 100 liver CT image patches, most with benign or malignant lesions, and compared their annotations to ground truth. Post-test was identical to pre-test. Between pre- and post-test, sensitivity increased by 2.8% (p = 0.01) but AUC did not change significantly. Missed metastases were classified as search errors (<2 seconds gaze time) or classification errors (>2 seconds gaze time) using the eye tracker. Out of 2775 possible detections, search errors decreased (10.8% to 8.1%; p < 0.01) but classification errors were unchanged (5.7% vs 5.7%). When stratified by difficulty, easier metastases showed larger reductions in search errors: for metastases with average sensitivity of 0-50%, 50-90%, and 90-100%, reductions in search errors were 16%, 35%, and 58%, respectively. The training program studied here may be able to improve radiologist performance by reducing errors but not classification errors.
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Affiliation(s)
- Scott S Hsieh
- Dept. of Radiology, Mayo Clinic, Rochester, MN, USA 55902
| | - Akitoshi Inoue
- Dept. of Radiology, Mayo Clinic, Rochester, MN, USA 55902
| | - Mariana Yalon
- Dept. of Radiology, Mayo Clinic, Rochester, MN, USA 55902
| | - David A Cook
- Dept. of Internal Medicine, Mayo Clinic, Rochester, MN, USA 55902
| | - Jeff L Fidler
- Dept. of Radiology, Mayo Clinic, Rochester, MN, USA 55902
| | - Hao Gong
- Dept. of Radiology, Mayo Clinic, Rochester, MN, USA 55902
| | | | | | - Matthew P Johnson
- Dept. of Quantitative Health Sciences, Mayo Clinic, Rochester, MN, USA 55902
| | - Shuai Leng
- Dept. of Radiology, Mayo Clinic, Rochester, MN, USA 55902
| | - Lifeng Yu
- Dept. of Radiology, Mayo Clinic, Rochester, MN, USA 55902
| | - David R Holmes
- Dept. of Radiology, Mayo Clinic, Rochester, MN, USA 55902
| | - Rickey E Carter
- Dept. of Quantitative Health Sciences, Mayo Clinic, Rochester, MN, USA 55902
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Sudhir Pillai P, Hsieh SS, Vercnocke AJ, Potretzke AM, Koo K, McCollough CH, Ferrero A. In Vivo Prediction of Kidney Stone Fragility Using Radiomics-Based Regression Models. J Endourol 2023; 37:443-452. [PMID: 36205579 PMCID: PMC10066766 DOI: 10.1089/end.2022.0483] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Introduction: The surgical technique for urinary stone removal is partly influenced by its fragility, as prognosticated by the clinician. This feasibility study aims to develop a linear regression model from CT-based radiomic markers to predict kidney stone comminution time in vivo with two ultrasonic lithotrites. Materials and Methods: Patients identified by urologists at our institution as eligible candidates for percutaneous nephrolithotomy were prospectively enrolled. The active engagement time of the lithotrite in breaking the stone during surgery denoted the comminution time of each stone. The comminution rate was computed as the stone volume disintegrated per minute. Stones were grouped into three fragility classes (fragile, moderate, hard), based on inverse of the comminution rates with respect to the mean. Multivariable linear regression models were trained with radiomic features extracted from clinical CT images to predict comminution times in vivo. The model with the least root mean squared error (RMSE) on comminution times and the fewest misclassification of fragility was finally selected. Results: Twenty-eight patients with 31 stones in total were included in this study. Stones in the cohort averaged 1557 (±2472) mm3 in volume and 5.3 (±7.4) minutes in comminution time. Ten stones had nonmoderate fragility. Linear regression of stone volume alone predicted comminution time with an RMSE of 6.8 minutes and missed all 10 stones with nonmoderate fragility. A fragility model that included stone volume, internal morphology, shape-based radiomics, and device type improved RMSE to below 3.3 minutes and correctly classified 20/21 moderate and 6/10 nonmoderate stones. Conclusions: CT metrics-based fragility models may provide information to surgeons regarding kidney stone fragility and facilitate the selection of stone removal procedures.
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Affiliation(s)
| | - Scott S. Hsieh
- Department of Radiology and Mayo Clinic, Rochester, Minnesota, USA
| | | | | | - Kevin Koo
- Department of Urology, Mayo Clinic, Rochester, Minnesota, USA
| | | | - Andrea Ferrero
- Department of Radiology and Mayo Clinic, Rochester, Minnesota, USA
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Marsh JF, Vercnocke AJ, Rajendran K, Tao S, Anderson JL, Ritman EL, Leng S, McCollough CH. Measurement of enhanced vasa vasorum density in a porcine carotid model using photon counting detector CT. J Med Imaging (Bellingham) 2023; 10:016001. [PMID: 36778671 PMCID: PMC9900679 DOI: 10.1117/1.jmi.10.1.016001] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2022] [Accepted: 01/16/2023] [Indexed: 02/08/2023] Open
Abstract
Purpose The onset of atherosclerosis is preceded by changes in blood perfusion within the arterial wall due to localized proliferation of the vasa vasorum. The purpose of this study was to quantify these changes in spatial density of the vasa vasorum using a research whole-body photon-counting detector CT (PCD-CT) scanner and a porcine model. Approach Vasa vasorum angiogenesis was stimulated in the left carotid artery wall of anesthetized pigs ( n = 5 ) while the right carotid served as a control. After a 6-week recovery period, the animals were scanned on the PCD-CT prior to and after injection of iodinated contrast. Annular regions of interest were used to measure wall enhancement in the injured and control arteries. The exact Wilcoxon-signed rank test was used to determine whether a significant difference in contrast enhancement existed between the injured and control arterial walls. Results The greatest arterial wall enhancement was observed following contrast recirculation. The wall enhancement measurements made over these time points revealed that the enhancement was greater in the injured artery for 13/16 scanned arterial regions. Using an exact Wilcoxon-signed rank test, a significantly increased enhancement ratio was found in injured arteries compared with control arteries ( p = 0.013 ). Vasa vasorum angiogenesis was confirmed in micro-CT scans of excised arteries. Conclusions Whole-body PCD-CT scanners can be used to detect and quantify the increased perfusion occurring within the porcine carotid arterial wall resulting from an increased density of vasa vasorum.
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Affiliation(s)
- Jeffrey F. Marsh
- Mayo Clinic, Department of Radiology, Rochester, Minnesota, United States
| | | | - Kishore Rajendran
- Mayo Clinic, Department of Radiology, Rochester, Minnesota, United States
| | - Shengzhen Tao
- Mayo Clinic, Department of Radiology, Rochester, Minnesota, United States
| | - Jill L. Anderson
- Mayo Clinic, Department of Radiology, Rochester, Minnesota, United States
| | - Erik L. Ritman
- Mayo Clinic, Department of Physiology and Biomedical Engineering, Rochester, Minnesota, United States
| | - Shuai Leng
- Mayo Clinic, Department of Radiology, Rochester, Minnesota, United States
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Koo CW, Kline TL, Yoon JH, Vercnocke AJ, Johnson MP, Suman G, Lu A, Larson NB. Magnetic resonance radiomic feature performance in pulmonary nodule classification and impact of segmentation variability on radiomics. Br J Radiol 2022; 95:20220230. [PMID: 36367095 PMCID: PMC9733623 DOI: 10.1259/bjr.20220230] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2022] [Revised: 10/05/2022] [Accepted: 10/13/2022] [Indexed: 11/13/2022] Open
Abstract
OBJECTIVE Investigate the performance of multiparametric MRI radiomic features, alone or combined with current standard-of-care methods, for pulmonary nodule classification. Assess the impact of segmentation variability on feature reproducibility and reliability. METHODS Radiomic features were extracted from 74 pulmonary nodules of 68 patients who underwent nodule resection or biopsy after MRI exam. The MRI features were compared with histopathology and conventional quantitative imaging values (maximum standardized uptake value [SUVmax] and mean Hounsfield unit [HU]) to determine whether MRI radiomic features can differentiate types of nodules and associate with SUVmax and HU using Wilcoxon rank sum test and linear regression. Diagnostic performance of features and four machine learning (ML) models were evaluated with area under the receiver operating characteristic curve (AUC) and 95% confidence intervals (CIs). Concordance correlation coefficient (CCC) assessed the segmentation variation impact on feature reproducibility and reliability. RESULTS Elevn diffusion-weighted features distinguished malignant from benign nodules (adjusted p < 0.05, AUC: 0.73-0.81). No features differentiated cancer types. Sixty-seven multiparametric features associated with mean CT HU and 14 correlated with SUVmax. All significant MRI features outperformed traditional imaging parameters (SUVmax, mean HU, apparent diffusion coefficient [ADC], T1, T2, dynamic contrast-enhanced imaging values) in distinguishing malignant from benign nodules with some achieving statistical significance (p < 0.05). Adding ADC and smoking history improved feature performance. Machine learning models demonstrated strong performance in nodule classification, with extreme gradient boosting (XGBoost) having the highest discrimination (AUC = 0.83, CI=[0.727, 0.932]). We found good to excellent inter- and intrareader feature reproducibility and reliability (CCC≥0.80). CONCLUSION Eleven MRI radiomic features differentiated malignant from benign lung nodules, outperforming traditional quantitative methods. MRI radiomic ML models demonstrated good nodule classification performances with XGBoost superior to three others. There was good to excellent inter- and intrareader feature reproducibility and reliability. ADVANCES IN KNOWLEDGE Our study identified MRI radiomic features that successfully differentiated malignant from benign lung nodules and demonstrated high performance of our MR radiomic feature-based ML models for nodule classification. These new findings could help further establish thoracic MRI as a non-invasive and radiation-free alternative to standard practice for pulmonary nodule assessment.
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Affiliation(s)
- Chi Wan Koo
- Department of Radiology, Mayo Clinic, Rochester, MN, USA
| | | | - Joo Hee Yoon
- Mayo Clinic Alix School of Medicine, Mayo Clinic, Rochester, MN, USA
| | | | - Mathew P Johnson
- Department of Health Sciences Research, Division of Biomedical Statistics and Informatics, Mayo Clinic, Rochester, MN, USA
| | - Garima Suman
- Department of Radiology, Mayo Clinic, Rochester, MN, USA
| | - Aiming Lu
- Department of Radiology, Mayo Clinic, Rochester, MN, USA
| | - Nicholas B Larson
- Department of Health Sciences Research, Division of Biomedical Statistics and Informatics, Mayo Clinic, Rochester, MN, USA
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Sheikhzadeh M, Vercnocke AJ, Tao S, Rajendran K, Leng S, Ritman EL, McCollough CH. Erratum to "Impact of Effective Detector Pixel and CT Voxel Size on Accurate Estimation of Blood Volume in Opacified Microvasculature" [Acad Radiol 2019; 26:1410-1416]. Acad Radiol 2020; 27:602. [PMID: 32035761 DOI: 10.1016/j.acra.2020.01.017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Sheikhzadeh M, Vercnocke AJ, Tao S, Rajendran K, Leng S, Ritman EL, McCollough CH. Impact of Effective Detector Pixel and CT Voxel Size on Accurate Estimation of Blood Volume in Opacified Microvasculature. Acad Radiol 2019; 26:1410-1416. [PMID: 30528631 DOI: 10.1016/j.acra.2018.11.013] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2018] [Revised: 11/20/2018] [Accepted: 11/22/2018] [Indexed: 11/19/2022]
Abstract
RATIONALE AND OBJECTIVES The purpose of this study was to determine the impact of effective detector-pixel-size and image voxel size on the accurate estimation of microvessel density (ratio of microvascular lumen volume/tissue volume) in an excised porcine myocardium specimen using microcomputed tomography (CT), and the ability of whole-body energy-integrating-detector (EID) CT and photon-counting-detector (PCD) CT to measure microvessel density in the same ex vivo specimen. MATERIALS AND METHODS Porcine myocardial tissue in which the microvessels contained radio-opaque material was scanned using a micro-CT scanner and data were generated with a range of detector pixel sizes and image voxel sizes from 20 to 260 microns, to determine the impact of these parameters on the accuracy of microvessel density estimates. The same specimen was scanned in a whole-body EID CT and PCD CT system and images reconstructed with 600 and 250 micron slice thicknesses, respectively. Fraction of tissue volume that is filled with opacified microvessels was determined by first subtracting the mean background attenuation value from all voxels, and then by summing the remaining attenuation. RESULTS Microvessel density data were normalized to the value measured at 20 µm voxel size, which was considered reference truth for this study. For emulated micro-CT voxels up to 260 µm, the microvessel density was underestimated by at most 11%. For whole-body EID CT and PCD CT, microvessel density was underestimated by 9.5% and overestimated by 0.1%, respectively. CONCLUSION Our data indicate that microvessel density can be accurately calculated from the larger detector pixels used in clinical CT scanners by measuring the increase of CT attenuation caused by these opacified microvessels.
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Affiliation(s)
| | | | - Shengzhen Tao
- Department of Radiology, Mayo Clinic, Rochester, MN 55905
| | | | - Shuai Leng
- Department of Radiology, Mayo Clinic, Rochester, MN 55905
| | - Erik L Ritman
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN 55905
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Marsh JF, Jorgensen SM, Rundle DS, Vercnocke AJ, Leng S, Butler PH, McCollough CH, Ritman EL. Evaluation of a photon counting Medipix3RX cadmium zinc telluride spectral x-ray detector. J Med Imaging (Bellingham) 2018; 5:043503. [PMID: 30840738 DOI: 10.1117/1.jmi.5.4.043503] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2018] [Accepted: 11/13/2018] [Indexed: 11/14/2022] Open
Abstract
We assess the performance of a cadmium zinc telluride (CZT)-based Medipix3RX energy-resolving and photon-counting x-ray detector as a candidate for spectral microcomputed tomography (micro-CT) imaging. It features an array of 128 × 128 , 110 - μ m 2 pixels, each with four simultaneous threshold counters that utilize real-time charge summing. Each pixel's response is assessed by imaging with a range of incident x-ray intensities and detector integration times. Energy-related assessments are made by exposing the detector to the emission from an I-125 radioisotope brachytherapy seed. Long-term stability is assessed by repeating identical exposures over the course of 1 h. The high yield of properly functioning pixels (98.8%), long-term stability (linear regression of whole-chip response over 1 h of acquisitions: y = - 0.0038 x + 2284 ; standard deviation: 3.7 counts), and energy resolution [2.5 keV full-width half-maximum (FWHM) (single pixel), 3.7 keV FWHM (across the full image)] make this device suitable for spectral micro-CT.
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Affiliation(s)
- Jeffrey F Marsh
- Mayo Clinic, Department of Radiology, Rochester, Minnesota, United States
| | - Steven M Jorgensen
- Mayo Clinic, Department of Radiology, Rochester, Minnesota, United States
| | - David S Rundle
- JairiNovus Technologies Ltd., Butler, Pennsylvania, United States
| | - Andrew J Vercnocke
- Mayo Clinic, Department of Radiology, Rochester, Minnesota, United States
| | - Shuai Leng
- Mayo Clinic, Department of Radiology, Rochester, Minnesota, United States
| | | | | | - Erik L Ritman
- Mayo Clinic, Department of Physiology and Biomedical Engineering, Rochester, Minnesota, United States
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Jorgensen SM, Korinek MJ, Vercnocke AJ, Anderson JL, Halaweish A, Leng S, McCollough CH, Ritman EL. Arterial Wall Perfusion Measured with Photon Counting Spectral X-ray CT. Proc SPIE Int Soc Opt Eng 2016; 9967. [PMID: 27807391 DOI: 10.1117/12.2238817] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Early atherosclerosis changes perfusion of the arterial wall due to localized proliferation of the vasa vasorum. When contrast agent passes through the artery, some enters the vasa vasorum and increases radiopacity of the arterial wall. Technical challenges to detecting changes in vasa vasorum density include the thin arterial wall, partial volume averaging at the arterial lumen/wall interface and calcification within the wall. We used a photon-counting spectral CT scanner to study carotid arteries of anesthetized pigs and micro-CT of these arteries to quantify vasa vasorum density. The left carotid artery wall was injected with autologous blood to stimulate vasa vasorum angiogenesis. The scans were performed at 25-120 keV; the tube-current-time product was 550 mAs. A 60 mL bolus of iodine contrast agent was injected into the femoral vein at 5mL/s. Two seconds post injection, an axial scan was acquired at every 3 s over 60 s (i.e., 20 time points). Each time point acquired 28 contiguous transaxial slices with reconstructed voxels 0.16 × 0.16 × 1 mm3. Regions-of-interest in the outer 2/3 of the arterial wall and in the middle 2/3 of the lumen were drawn and their enhancements plotted versus time. Lumenal CT values peaked several seconds after injection and then returned towards baseline. Arterial wall CT values peaked concurrent to the lumen. The peak arterial wall enhancement in the left carotid arterial wall correlated with increased vasa vasorum density observed in micro-CT images of the isolated arteries.
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Affiliation(s)
- Steven M Jorgensen
- Dept. of Physiology and Biomedical Engineering, Mayo Clinic, 200 First Street SW, Rochester, MN USA 55905
| | - Mark J Korinek
- Dept. of Physiology and Biomedical Engineering, Biomedical Imaging Resource, Mayo Clinic, 200 First Street SW, Rochester, MN USA 55905
| | - Andrew J Vercnocke
- Dept. of Physiology and Biomedical Engineering, Mayo Clinic, 200 First Street SW, Rochester, MN USA 55905
| | - Jill L Anderson
- Dept. of Physiology and Biomedical Engineering, Mayo Clinic, 200 First Street SW, Rochester, MN USA 55905
| | | | - Shuai Leng
- Dept. Radiology, Mayo Clinic, 200 First Street SW, Rochester, MN USA 55905
| | | | - Erik L Ritman
- Dept. of Physiology and Biomedical Engineering, Mayo Clinic, 200 First Street SW, Rochester, MN USA 55905
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Jorgensen SM, Vercnocke AJ, Rundle DS, Butler PH, McCollough CH, Ritman EL. Evaluation of a photon counting Medipix3RX CZT spectral x-ray detector. Proc SPIE Int Soc Opt Eng 2016; 9969. [PMID: 27795606 DOI: 10.1117/12.2236501] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
We assessed the performance of a cadmium zinc telluride (CZT)-based Medipix3RX x-ray detector as a candidate for micro-computed tomography (micro-CT) imaging. This technology was developed at CERN for the Large Hadron Collider. It features an array of 128 by 128, 110 micrometer square pixels, each with eight simultaneous threshold counters, five of which utilize real-time charge summing, significantly reducing the charge sharing between contiguous pixels. Pixel response curves were created by imaging a range of x-ray intensities by varying x-ray tube current and by varying the exposure time with fixed x-ray current. Photon energy-related assessments were made by flooding the detector with the tin foil filtered emission of an I-125 radioisotope brachytherapy seed and sweeping the energy threshold of each of the four charge-summed counters of each pixel in 1 keV steps. Long term stability assessments were made by repeating exposures over the course of one hour. The high properly-functioning pixel yield (99%), long term stability (linear regression of whole-chip response over one hour of acquisitions: y = -0.0038x + 2284; standard deviation: 3.7 counts) and energy resolution (2.5 keV FWHM (single pixel), 3.7 keV FWHM across the full image) make this device suitable for spectral micro-CT. The charge summing performance effectively reduced the measurement corruption caused by charge sharing which, when unaccounted for, shifts the photon energy assignment to lower energies, degrading both count and energy accuracy. Effective charge summing greatly improves the potential for calibrated, energy-specific material decomposition and K edge difference imaging approaches.
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Affiliation(s)
- Steven M Jorgensen
- Dept. of Physiology and Biomedical Engineering, Mayo Clinic, 200 First Street SW, Rochester, MN USA 55905
| | - Andrew J Vercnocke
- Dept. of Physiology and Biomedical Engineering, Mayo Clinic, 200 First Street SW, Rochester, MN USA 55905
| | - David S Rundle
- JairiNovus Technologies Ltd., 119 Heartland Drive, Butler, PA USA 16001
| | | | | | - Erik L Ritman
- Dept. of Physiology and Biomedical Engineering, Mayo Clinic, 200 First Street SW, Rochester, MN USA 55905
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12
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Zamir M, Vercnocke AJ, Edwards PK, Anderson JL, Jorgensen SM, Ritman EL. Myocardial Perfusion: Characteristics of Distal Intramyocardial Arteriolar Trees. Ann Biomed Eng 2015; 43:2771-9. [PMID: 25952363 PMCID: PMC4618034 DOI: 10.1007/s10439-015-1325-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2014] [Accepted: 04/16/2015] [Indexed: 11/30/2022]
Abstract
A combination of experimental, theoretical, and imaging methodologies is used to examine the hierarchical structure and function of intramyocardial arteriolar trees in porcine hearts to provide a window onto a region of myocardial microvasculature which has been difficult to fully explore so far. A total of 66 microvascular trees from 6 isolated myocardial specimens were analyzed, with a cumulative number of 2438 arteriolar branches greater than or equal to 40 μm lumen diameter. The distribution of flow rates within each tree was derived from an assumed power law relationship for that tree between the diameter of vessel segments and flow rates that are consistent with that power law and subject to conservation of mass along hierarchical structure of the tree. The results indicate that the power law index increases at levels of arteriolar vasculature closer to the capillary level, consistent with a concomitant decrease in shear stress acting on endothelial tissue. These results resolve a long standing predicament which could not be resolved previously because of lack of data about the 3D, interconnected, arterioles. In the context of myocardial perfusion, the results indicate that the coefficient of variation of flow rate in pre-capillary distal arterioles is high, suggesting that heterogeneity of flow rate in these arterioles is not entirely random but may be due at least in part to active control.
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Affiliation(s)
- Mair Zamir
- Departments of Applied Mathematics and of Medical Biophysics, Western University, 1151 Richmond Street, London, ON, N6A 5B7, Canada
| | - Andrew J Vercnocke
- Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, 200 First Street S.W., Rochester, MN, 55905, USA
| | - Phillip K Edwards
- Biomedical Imaging Resource, Mayo Clinic College of Medicine, 200 First Street S.W., Rochester, MN, 55905, USA
| | - Jill L Anderson
- Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, 200 First Street S.W., Rochester, MN, 55905, USA
| | - Steven M Jorgensen
- Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, 200 First Street S.W., Rochester, MN, 55905, USA
| | - Erik L Ritman
- Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, 200 First Street S.W., Rochester, MN, 55905, USA.
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13
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Hann CR, Vercnocke AJ, Bentley MD, Jorgensen SM, Fautsch MP. Anatomic changes in Schlemm's canal and collector channels in normal and primary open-angle glaucoma eyes using low and high perfusion pressures. Invest Ophthalmol Vis Sci 2014; 55:5834-41. [PMID: 25139736 DOI: 10.1167/iovs.14-14128] [Citation(s) in RCA: 82] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
PURPOSE To examine the anatomy of Schlemm's canal (SC) and collector channels (CCs) in normal human and primary open-angle glaucoma (POAG) eyes under low and high perfusion pressure. METHODS In normal (n = 3) and POAG (n = 3) eye pairs, one eye was perfused at 10 mm Hg while the fellow eye was perfused at 20 mm Hg for 2 hours. Eyes were perfusion fixed at like pressures, dissected into quadrants, embedded in Epon Araldite, and scanned by three-dimensional micro-computed tomography (3D micro-CT). Schlemm's canal volume, CC orifice area, diameter, and number were measured using ANALYZE software. RESULTS Normal eyes showed a larger SC volume (3.3-fold) and CC orifice area (9962.8 vs. 8825.2 μm(2)) and a similar CC diameter (34.3 ± 17.8 vs. 32.7 ± 13.0 μm) at 10 mm Hg compared to 20 mm Hg. In POAG eyes, SC volume (2.0-fold), CC orifice area (8049.2 μm(2)-6468.4 μm(2)), and CC diameter (36.2 ± 19.1 vs. 29.0 ± 13.8 μm) were increased in 10 mm Hg compared to 20 mm Hg perfusion pressures. Partial and total CC occlusions were present in normal and POAG eyes, with a 3.7-fold increase in total occlusions in POAG eyes compared to normal eyes at 20 mm Hg. Visualization of CCs increased by 24% in normal and by 21% in POAG eyes at 20 mm Hg compared to 10 mm Hg. Schlemm's canal volume, CC area, and CC diameter were decreased in POAG eyes compared to normal eyes at like pressures. CONCLUSIONS Compensatory mechanisms for transient and short periods of increased pressure appear to be diminished in POAG eyes. Variable response to pressure change in SC and CCs may be a contributing factor to outflow facility change in POAG eyes.
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Affiliation(s)
- Cheryl R Hann
- Department of Ophthalmology, Mayo Clinic, Rochester, Minnesota, United States
| | - Andrew J Vercnocke
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, United States
| | - Michael D Bentley
- Department of Biological Sciences, Minnesota State University, Mankato, Minnesota, United States
| | - Steven M Jorgensen
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, United States
| | - Michael P Fautsch
- Department of Ophthalmology, Mayo Clinic, Rochester, Minnesota, United States
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Kline TL, Knudsen BE, Anderson JL, Vercnocke AJ, Jorgensen SM, Ritman EL. Anatomy of hepatic arteriolo-portal venular shunts evaluated by 3D micro-CT imaging. J Anat 2014; 224:724-31. [PMID: 24684343 DOI: 10.1111/joa.12178] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/25/2014] [Indexed: 12/25/2022] Open
Abstract
The liver differs from other organs in that two vascular systems deliver its blood - the hepatic artery and the portal vein. However, how the two systems interact is not fully understood. We therefore studied the microvascular geometry of rat liver hepatic artery and portal vein injected with the contrast polymer Microfil(®). Intact isolated rat livers were imaged by micro-CT and anatomic evidence for hepatic arteriolo-portal venular shunts occurring between hepatic artery and portal vein branches was found. Simulations were performed to rule out the possibility of the observed shunts being artifacts resulting from image blurring. In addition, in the case of specimens where only the portal vein was injected, only the portal vein was opacified, whereas in hepatic artery injections, both the hepatic artery and portal vein were opacified. We conclude that mixing of the hepatic artery and portal vein blood can occur proximal to the sinusoidal level, and that the hepatic arteriolo-portal venular shunts may function as a one-way valve-like mechanism, allowing flow only from the hepatic artery to the portal vein (and not the other way around).
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Affiliation(s)
- Timothy L Kline
- Departments of Radiology, Mayo Clinic College of Medicine, Rochester, MN, USA
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15
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Moritz R, Anderson JL, Vercnocke AJ, Wentz RJ, Ritman EL. Changes in CT angiographic opacification of porcine coronary artery wall with patchy altered flow in vasa vasorum. Int J Cardiovasc Imaging 2013; 29:1325-33. [PMID: 23443339 DOI: 10.1007/s10554-013-0198-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/20/2012] [Accepted: 02/16/2013] [Indexed: 11/28/2022]
Abstract
To evaluate the potential of whole-body CT to detect localized areas of decreased or increased vascularity in coronary arterial walls. We used both microsphere embolization of coronary artery vasa vasorum to generate small areas of hypoperfusion and surrounding hyperperfusion of the arterial wall and diet-induced hypercholesterolemia. As a stimulus for localized angiogenesis, such as occurs in early plaque formation in the coronary arterial wall, microspheres were injected selectively into the LAD coronary artery lumens of anesthetized pigs. Fourteen pigs (acute) then had a segment of their LAD harvested during injection of contrast medium and snap-frozen for subsequent cryo-static micro-CT. An additional thirteen pigs (chronic) were allowed to recover, fed a high cholesterol diet and 3 months later were again anesthetized and a segment of the LAD artery harvested and scanned. The spatial distribution of the contrast agent within the arterial wall was measured in contiguous micro-CT images at right angles to the lumen axis with the area of wall in each cross-sectional image being approximately (0.1 mm)(3) in size. In the acute animals there were no localized areas of increased contrast around the hypoperfused embolized perfusion territories in the arterial wall, but in the chronic animals the hypoperfused areas were surrounded by increased contrast. These results suggest that CT might be able to detect localized regions of increased vascularity in the arterial wall as an indicator of early atherosclerotic stimulation of vasa vasorum proliferation.
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Affiliation(s)
- Regina Moritz
- Department of Physiology and Biomedical Engineering, Rochester, MN 55905, USA
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16
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Zamir M, Twynstra J, Vercnocke AJ, Welch I, Jorgensen SM, Ritman EL, Holdsworth DW, Shoemaker JK. Intrinsic microvasculature of the sciatic nerve in the rat. J Peripher Nerv Syst 2012; 17:377-84. [DOI: 10.1111/j.1529-8027.2012.00435.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Affiliation(s)
| | | | - Andrew J. Vercnocke
- Physiological Imaging Research Laboratory, Mayo Clinic; College of Medicine; Rochester; MN; USA
| | | | - Steve M. Jorgensen
- Physiological Imaging Research Laboratory, Mayo Clinic; College of Medicine; Rochester; MN; USA
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Jorgensen SM, Eaker DR, Vercnocke AJ, Ritman EL. Reproducibility of global and local reconstruction of three-dimensional micro-computed tomography of iliac crest biopsies. IEEE Trans Med Imaging 2008; 27:569-575. [PMID: 18390353 DOI: 10.1109/tmi.2007.912821] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Variation in computed tomography (CT) image gray-scale and spatial geometry due to specimen orientation, magnification, voxel size, differences in X-ray photon energy and limited field-of-view during the scan, were evaluated in repeated micro-CT scans of iliac crest biopsies and test phantoms. Using the micro-CT scanner on beamline X2B at the Brookhaven National Laboratory's National Synchrotron Light Source, 3-D micro-CT images were generated. They consisted of up to 1024 x 2400(2), 4-microm cubic voxels, each with 16-bit gray-scale. We also reconstructed the images at 16-, 32-, and 48-microm voxel resolution. Scan data were reconstructed from the complete profiles using filtered back-projection and from truncated profiles using profile-extension and with a Local reconstruction algorithm. Three biopsies and one bone-like test phantom were each rescanned at three different times at annual intervals. For the full-data-set reconstructions, the reproducibility of the estimates of mineral content of bone at mean bone opacity value, was +/-28.8, i.e., 2.56%, in a 4-microm cubic voxel at the 95% confidence level. The reproducibility decreased with increased voxel size. The interscan difference in imaged bone volume ranged from 0.86 4-microm 0.64% at 4-microm voxel resolution, and 2.64 4-microm 2.48% at 48 microm.
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Affiliation(s)
- S M Jorgensen
- Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, MN 55905 USA
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