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  • 1
    Online Resource
    Online Resource
    American Thoracic Society ; 2000
    In:  American Journal of Respiratory and Critical Care Medicine Vol. 161, No. 5 ( 2000-05-01), p. 1567-1571
    In: American Journal of Respiratory and Critical Care Medicine, American Thoracic Society, Vol. 161, No. 5 ( 2000-05-01), p. 1567-1571
    Type of Medium: Online Resource
    ISSN: 1073-449X , 1535-4970
    RVK:
    Language: English
    Publisher: American Thoracic Society
    Publication Date: 2000
    detail.hit.zdb_id: 1468352-0
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  • 2
    In: Pediatric Pulmonology, Wiley, Vol. 37, No. 4 ( 2004-04), p. 318-323
    Type of Medium: Online Resource
    ISSN: 8755-6863
    Language: English
    Publisher: Wiley
    Publication Date: 2004
    detail.hit.zdb_id: 1491904-7
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  • 3
    Online Resource
    Online Resource
    Ovid Technologies (Wolters Kluwer Health) ; 2019
    In:  Circulation: Cardiovascular Imaging Vol. 12, No. 12 ( 2019-12)
    In: Circulation: Cardiovascular Imaging, Ovid Technologies (Wolters Kluwer Health), Vol. 12, No. 12 ( 2019-12)
    Abstract: Modern computed tomographic scanning can produce 4-dimensional images of the left atrial appendage (LAA). LAA function and morphology can then be measured, to plan interventions such as occlusion and to evaluate LAA flow for thrombogenic risk analysis. A current problem here is defining a reproducible boundary between the LAA and the left atrium. Methods: This study used retrospectively gated 4-dimensional computed tomographic data from 25 implantation and coronary artery imaging patients. In each patient, the LAA ostium was defined at multiple time points during the RR interval. To examine the reproducibility of the definition of the LAA ostium, 3 observers analyzed all time frames in each patient 3 times. Five nonconsecutive time frames from each patient were then compared using intraclass correlation coefficients to quantify the precision of the method across patients. The correlation of LAA volumes for each time frame of each patient was determined across the different observers (interobserver) and within each observer’s own data sets (intraobserver). Results: The method was successful in 92% of patients. Two-way random-effect, absolute-agreement, single-measurement intraclass correlation coefficients for interobserver measurements were 0.984, 0.990, and 0.988, with intraobserver intraclass correlation coefficients of 0.989, 0.989, and 0.995. The intraclass correlation coefficient of all observations was 0.988. Conclusions: Classification of the LAA ostium using a stepwise procedure identifying the coumadin ridge and 2 vascular landmarks in ECG-gated computed tomography provides a viable method of establishing a highly reproducible boundary between the atrium and LAA needed to obtain LAA metrics useful for procedure planning and measuring LAA function.
    Type of Medium: Online Resource
    ISSN: 1941-9651 , 1942-0080
    Language: English
    Publisher: Ovid Technologies (Wolters Kluwer Health)
    Publication Date: 2019
    detail.hit.zdb_id: 2440475-5
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  • 4
    In: Medical Physics, Wiley, Vol. 46, No. 12 ( 2019-12), p. 5514-5527
    Abstract: Coronary x‐ray computed tomography angiography (CCTA) continues to develop as a noninvasive method for the assessment of coronary vessel geometry and the identification of physiologically significant lesions. The uncertainty of quantitative lesion diameter measurement due to limited spatial resolution and vessel motion reduces the accuracy of CCTA diagnoses. In this paper, we introduce a new technique called computed tomography (CT)‐number‐Calibrated Diameter to improve the accuracy of the vessel and stenosis diameter measurements with CCTA. Methods A calibration phantom containing cylindrical holes (diameters spanning from 0.8 mm through 4.0 mm) capturing the range of diameters found in human coronary vessels was three‐dimensional printed. We also printed a human stenosis phantom with 17 tubular channels having the geometry of lesions derived from patient data. We acquired CT scans of the two phantoms with seven different imaging protocols. Calibration curves relating vessel intraluminal maximum voxel value (maximum CT number of a voxel, described in Hounsfield Units, HU) to true diameter, and full‐width‐at‐half maximum (FWHM) to true diameter were constructed for each CCTA protocol. In addition, we acquired scans with a small constant motion (15 mm/s) and used a motion correction reconstruction (Snapshot Freeze) algorithm to correct motion artifacts. We applied our technique to measure the lesion diameter in the 17 lesions in the stenosis phantom and compared the performance of CT‐number‐Calibrated Diameter to the ground truth diameter and a FWHM estimate. Results In all cases, vessel intraluminal maximum voxel value vs diameter was found to have a simple functional form based on the two‐dimensional point spread function yielding a constant maximum voxel value region above a cutoff diameter, and a decreasing maximum voxel value vs decreasing diameter below a cutoff diameter. After normalization, focal spot size and reconstruction kernel were the principal determinants of cutoff diameter and the rate of maximum voxel value reduction vs decreasing diameter. The small constant motion had a significant effect on the CT number calibration; however, the motion‐correction algorithm returned the maximum voxel value vs diameter curve to that of stationary vessels. The CT number Calibration technique showed better performance than FWHM estimation of diameter, yielding a high accuracy in the tested range (0.8 mm through 2.5 mm). We found a strong linear correlation between the smallest diameter in each of 17 lesions measured by CT‐number‐Calibrated Diameter (D C ) and ground truth diameter (D gt ), (D C  = 0.951 × D gt  + 0.023 mm, r = 0.998 with a slope very close to 1.0 and intercept very close to 0 mm. Conclusions Computed tomography‐number‐Calibrated Diameter is an effective method to enhance the accuracy of the estimate of small vessel diameters and degree of coronary stenosis in CCTA.
    Type of Medium: Online Resource
    ISSN: 0094-2405 , 2473-4209
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2019
    detail.hit.zdb_id: 1466421-5
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  • 5
    In: Circulation, Ovid Technologies (Wolters Kluwer Health), Vol. 142, No. Suppl_3 ( 2020-11-17)
    Abstract: Introduction: The formation of thrombus in the left atrial appendage (LAA) and risk for systemic embolization may result in part from stasis and poor blood volume emptying during atrial fibrillation (AF). Functional 4-dimensional computed tomography (4DCT) is a promising technique to measure LAA ejection fraction and blood volume emptying. Hypothesis: We hypothesize that the LAA ejection fraction measured by 4DCT is decreased during AF compared to sinus rhythm. Methods: 256-slice 4DCT scans obtained in patients for coronary artery imaging or pre-procedurally for AF, VT or SVT ablation procedures were analyzed retrospectively. In each patient, LAA volumes were measured at multiple phases during one cardiac cycle using segmentation software (ITK-SNAP and Osirix MD). LAA ejection fraction was calculated as the difference between minimum and maximum volumes and was analyzed using Wilcoxon rank sum. Results: Out of 54 patients, 37 patients were in sinus rhythm and 17 patients were in AF. Between NSR vs. AF, mean age was 69.1±12.8 vs 73.2±11.5 years (p=0.13), 28% vs 36% female (p=0.54), LVEF was 58±11% vs 60±9% (p=0.95), and echo-derived left atrial volume index was 29.5±6.1 ml/m2 vs 41.7±12.8 ml/m2 (p=0.06). Patients who were in sinus rhythm during their CT scan had a higher LAA ejection fraction than those who were in AF (58±13% vs. 29±9%, p 〈 0.0001). For patients who were in AF during their CT scan, there was no difference in LAA ejection fraction between patients with a history of paroxysmal AF compared to patients with a history of persistent AF (30±10% vs. 28±10%, p=0.75). Conclusions: Analysis of the LAA volumes using functional cardiac CT is a feasible method to quantify blood volume emptying from the LAA. Patients in AF were observed to have significantly decreased LAA ejection fraction and blood volume emptying compared to patients in sinus rhythm. Further studies are needed to determine whether this technique may improve personalized risk stratification for stroke.
    Type of Medium: Online Resource
    ISSN: 0009-7322 , 1524-4539
    Language: English
    Publisher: Ovid Technologies (Wolters Kluwer Health)
    Publication Date: 2020
    detail.hit.zdb_id: 1466401-X
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  • 6
    In: Journal of Medical Imaging, SPIE-Intl Soc Optical Eng, Vol. 6, No. 04 ( 2019-12-10), p. 1-
    Type of Medium: Online Resource
    ISSN: 2329-4302
    Language: Unknown
    Publisher: SPIE-Intl Soc Optical Eng
    Publication Date: 2019
    detail.hit.zdb_id: 2768118-X
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  • 7
    In: Medical Physics, Wiley, Vol. 49, No. 4 ( 2022-04), p. 2309-2323
    Abstract: We demonstrate the viability of a four‐dimensional X‐ray computed tomography (4DCT) imaging system to accurately and precisely estimate mechanical activation times of left ventricular (LV) wall motion. Accurate and reproducible timing estimates of LV wall motion may be beneficial in the successful planning and management of cardiac resynchronization therapy (CRT). Methods We developed an anthropomorphically accurate in silico LV phantom based on human CT images with programmed septal‐lateral wall dyssynchrony. Twenty‐six temporal phases of the in silico phantom were used to sample the cardiac cycle of 1 s. For each of the 26 phases, 1 cm thick axial slabs emulating axial CT image volumes were extracted, 3D printed, and imaged using a commercially available CT scanner. A continuous dynamic sinogram was synthesized by blending sinograms from these static phases; the synthesized sinogram emulated the sinogram that would be acquired under true continuous phantom motion. Using the synthesized dynamic sinogram, images were reconstructed at 70 ms intervals spanning the full cardiac cycle; these images exhibited expected motion artifact characteristics seen in images reconstructed from real dynamic data. The motion corrupted images were then processed with a novel motion correction algorithm (ResyncCT) to yield motion corrected images. Five pairs of motion uncorrected and motion corrected images were generated, each corresponding to a different starting gantry angle (0 to 180 degrees in 45 degree increments). Two line profiles perpendicular to the endocardial surface were used to sample local myocardial motion trajectories at the septum and the lateral wall. The mechanical activation time of wall motion was defined as the time at which the endocardial boundary crossed a fixed position defined on either of the two line profiles while moving toward the center of the LV during systolic contraction. The mechanical activation times of these myocardial trajectories estimated from the motion uncorrected and the motion corrected images were then compared with those derived from the static images of the 3D printed phantoms (ground truth). The precision of the timing estimates was obtained from the five different starting gantry angle simulations. Results The range of estimated mechanical activation times observed across all starting gantry angles was significantly larger for the motion uncorrected images than for the motion corrected images (lateral wall: 58 ± 15 ms vs 12 ± 4 ms, p   〈  0.005; septal wall: 61 ± 13 ms vs 13 ± 9 ms, p   〈  0.005). Conclusions 4DCT images processed with the ResyncCT motion correction algorithm yield estimates of mechanical activation times of LV wall motion with significantly improved accuracy and precision. The promising results reported in this study highlight the potential utility of 4DCT in estimating the timing of mechanical events of interest for CRT guidance.
    Type of Medium: Online Resource
    ISSN: 0094-2405 , 2473-4209
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2022
    detail.hit.zdb_id: 1466421-5
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  • 8
    In: Medical Physics, Wiley, Vol. 49, No. 7 ( 2022-07), p. 4404-4418
    Abstract: Standard four‐dimensional computed tomography (4DCT) cardiac reconstructions typically include spiraling artifacts that depend not only on the motion of the heart but also on the gantry angle range over which the data was acquired. We seek to reduce these motion artifacts and, thereby, improve the accuracy of left ventricular wall positions in 4DCT image series. Methods We use a motion artifact reduction approach (ResyncCT) that is based largely on conjugate pairs of partial angle reconstruction (PAR) images. After identifying the key locations where motion artifacts exist in the uncorrected images, paired subvolumes within the PAR images are analyzed with a modified cross‐correlation function in order to estimate 3D velocity and acceleration vectors at these locations. A subsequent motion compensation process (also based on PAR images) includes the creation of a dense motion field, followed by a backproject‐and‐warp style compensation. The algorithm was tested on a 3D printed phantom, which represents the left ventricle (LV) and on challenging clinical cases corrupted by severe artifacts. Results The results from our preliminary phantom test as well as from clinical cardiac scans show crisp endocardial edges and resolved double‐wall artifacts. When viewed as a temporal series, the corrected images exhibit a much smoother motion of the LV endocardial boundary as compared to the uncorrected images. In addition, quantitative results from our phantom studies show that ResyncCT processing reduces endocardial surface distance errors from 0.9 ± 0.8 to 0.2 ± 0.1 mm. Conclusions The ResyncCT algorithm was shown to be effective in reducing motion artifacts and restoring accurate wall positions. Some perspectives on the use of conjugate‐PAR images and on techniques for CT motion artifact reduction more generally are also given.
    Type of Medium: Online Resource
    ISSN: 0094-2405 , 2473-4209
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2022
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  • 9
    In: Pediatric Pulmonology, Wiley, Vol. 31, No. 4 ( 2001-4), p. 267-276
    Type of Medium: Online Resource
    ISSN: 8755-6863 , 1099-0496
    Language: Unknown
    Publisher: Wiley
    Publication Date: 2001
    detail.hit.zdb_id: 1491904-7
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  • 10
    In: Pediatrics, American Academy of Pediatrics (AAP), Vol. 104, No. 1 ( 1999-07-01), p. e6-e6
    Abstract: A high incidence of sudden, unexplained deaths in infants born to HIV-infected mothers has been noted in several epidemiologic studies. During the course of a prospective study of heart and lung disease in children born to HIV-infected mothers, we noted that of 5 unexpected non-HIV-related deaths, 4 were attributed to traumatic events. Methods. The Pediatric Pulmonary and Cardiac Complications of Vertically Transmitted HIV Infection (P2C2) study is a multicenter, prospective investigation of the incidence of heart and lung disease in HIV-infected children. A total of 805 children were enrolled and followed for 5 to 7 years with serial immunologic, pulmonary and cardiac function studies. During the study, a multidisciplinary committee was formed to review the cause of death for those patients who died. The committee used results of pulmonary, cardiac, and laboratory tests, hospital summaries, as well as autopsy and coroners' reports. The committee formed a consensus about the underlying and contributing causes of death for each subject using the definitions from the 1989 US Standard Certificate of Death. Results. A total of 121 deaths occurred during the course of the P2C2 study. Of the 121 deaths, 5 were traumatic or sudden and unexpected and judged by the Mortality Review Committee to be unrelated to HIV infection. The median age at the time of death was 1.3 months and ranged from 1.2 to 37.8 months. Two infants died of trauma: a skull fracture and subdural hematoma in 1 infant and multiple skeletal fractures consistent with battered child syndrome in the other infant. The third infant died of accidental suffocation at home at 1.2 months of age. The fourth infant died suddenly and unexpectedly at home at 1.3 months of age. The autopsy showed no sign of HIV or other infection and was consistent with sudden unexpected death or SIDS. One non-HIV-related death occurred when a 38-month-old child died together with the mother in an unwitnessed drowning. The cumulative mortality rate attributable to trauma and sudden death at 4 months of age was 0.95% (95% CI: 0.02–1.87%) and the infant mortality rate was 9.5/1000 live births. Three children were born prematurely at 30, 33, and 36 weeks' gestational age, respectively, and 3 mothers admitted using recreational drugs before or during pregnancy. Discussion. These traumatic and sudden non-HIV-related deaths accounted for 4.1% (5/121) of the deaths during the entire P2C2 study period and for 20% (4/20) of the deaths in the first year of life. Four deaths were attributable to accidental and nonaccidental trauma rather than to other common causes of infant death. One death was a sudden unexpected death, similar to SIDS, a leading cause of infant death in the United States. The majority of previously reported non-HIV-related deaths in infants born to HIV-infected mothers have been attributed to SIDS or to unexplained sudden death. In contrast with other reports, 4 of the 5 children in our series died of accidental or nonaccidental trauma and only 1 was a sudden unexplained death. It is unlikely that HIV exposure is related directly to the deaths described in this report; however, maternal HIV infection may be a marker for factors that place the child at risk for sudden or traumatic death. Summary. This report suggests that children born to HIV-infected mothers may be at increased risk for traumatic or sudden, unexplained, non-HIV-related death. These children seem to be at risk regardless of their own HIV infection status. Furthermore, 4 of the deaths in our study occurred within the first few months of life, suggesting that this is a period of increased vulnerability. Studies to identify associated risk factors for non-HIV-related deaths are needed to identify these high-risk infants. Children born to HIV-infected mothers may be more vulnerable than was recognized previously and may be in need of increased social services, especially in early infancy.
    Type of Medium: Online Resource
    ISSN: 1098-4275 , 0031-4005
    Language: English
    Publisher: American Academy of Pediatrics (AAP)
    Publication Date: 1999
    detail.hit.zdb_id: 1477004-0
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