Efficacy of Dynamic Chest Radiography for Chronic Thromboembolic Pulmonary Hypertension.

Background While current guidelines require lung ventilation-perfusion (V/Q) scanning as the first step to diagnose chronic pulmonary embolism in pulmonary hypertension (PH), its use may be limited by low availability and/or exposure to ionizing radiation. Purpose To compare the performance of dynamic chest radiography (DCR) and lung V/Q scanning for detection of chronic thromboembolic PH (CTEPH). Materials and Methods Patients with PH who underwent DCR and V/Q scanning in the supine position from December 2019 to July 2021 were retrospectively screened. The diagnosis of CTEPH was confirmed with right heart catheterization and invasive pulmonary angiography. Observer tests were conducted to evaluate the diagnostic accuracy of DCR and V/Q scanning. The lungs were divided into six areas (upper, middle, and lower for both) in the anteroposterior image, and the number of lung areas with thromboembolic perfusion defects was scored. Diagnostic performance was compared between DCR and V/Q scanning using the area under the receiver operating characteristic curve. Agreement between the interpretation of DCR and that of V/Q scanning was assessed using the Cohen kappa coefficient and percent agreement. Results A total of 50 patients with PH were analyzed: 29 with CTEPH (mean age, 64 years ± 15 [SD]; 19 women) and 21 without CTEPH (mean age, 61 years ± 22; 14 women). The sensitivity, specificity, and accuracy of DCR were 97%, 86%, and 92%, respectively, and those of V/Q scanning were 100%, 86%, and 94%, respectively. Areas under the receiver operating characteristic curve for DCR and V/Q scanning were 0.92 (95% CI: 0.79, 0.97) and 0.93 (95% CI: 0.78, 0.98). Agreement between the consensus interpretation of DCR and that of V/Q scanning was substantial (κ = 0.79 [95% CI: 0.61, 0.96], percent agreement = 0.9 [95% CI: 0.79, 0.95]). Conclusion Dynamic chest radiography had similar efficacy to ventilation-perfusion scanning in the detection of chronic thromboembolic pulmonary hypertension. © RSNA, 2022 Online supplemental material is available for this article. See also the editorial by Wandtke and Koproth-Joslin in this issue.

Projected lung area using dynamic X-ray (DXR) with a flat-panel detector system and automated tracking in patients with chronic obstructive pulmonary disease (COPD).

OBJECTIVES: To assess the association of projected lung area (PLA) measured by DXR with demographic data, pulmonary function, and COPD severity, and to generate PLA over time curves using automated tracking. METHODS: This retrospective study recruited healthy volunteers and COPD patients. Participants were classified into three groups: normal, COPD mild and COPD severe. PLA was calculated from the manually traced bilateral lung contours. PLA over time curves were produced using automated tracking, which was used to calculate slope and intercept by approximate line during forced expiration. The correlation of PLA, difference of PLA between end-inspiration and end-expiration (ΔPLA), slope, and intercept with demographic data and pulmonary function tests were investigated. The difference of PLA, ΔPLA, intercept, and slope among three groups were also evaluated. RESULTS: This study enrolled 45 healthy volunteers and 32 COPD patients. COPD severe group had larger PLA in both lungs at tidal/forced end-inspiration/expiration, smaller slope, and larger intercept than normal group (p < 0.001). PLA was correlated with % forced expiratory volume in one second (%FEV1) (rs from -0.42 to -0.31, p ≤ 0.01). ΔPLA in forced breathing showed moderate correlation with vital capacity (VC) (rs = 0.58, p < 0.001), while ΔPLA in tidal breathing showed moderate correlation with %FEV1 (rs = -0.52, p < 0.001) as well as mild correlation with tidal volume (rs = 0.24, p = 0.032). Intercept was slightly underestimated compared with manually contoured PLA (p < 0.001). CONCLUSION: COPD patients had larger PLA than healthy volunteers. PLA and ΔPLA in tidal breathing showed mild to moderate correlation with %FEV1.

Vector-field dynamic x-ray (VF-DXR) using optical flow method in patients with chronic obstructive pulmonary disease.

BACKGROUND: We assessed the difference in lung motion during inspiration/expiration between chronic obstructive pulmonary disease (COPD) patients and healthy volunteers using vector-field dynamic x-ray (VF-DXR) with optical flow method (OFM). METHODS: We enrolled 36 COPD patients and 47 healthy volunteers, classified according to pulmonary function into: normal, COPD mild, and COPD severe. Contrast gradient was obtained from sequential dynamic x-ray (DXR) and converted to motion vector using OFM. VF-DXR images were created by projection of the vertical component of lung motion vectors onto DXR images. The maximum magnitude of lung motion vectors in tidal inspiration/expiration, forced inspiration/expiration were selected and defined as lung motion velocity (LMV). Correlations between LMV with demographics and pulmonary function and differences in LMV between COPD patients and healthy volunteers were investigated. RESULTS: Negative correlations were confirmed between LMV and % forced expiratory volume in one second (%FEV1) in the tidal inspiration in the right lung (Spearman's rank correlation coefficient, rs = -0.47, p < 0.001) and the left lung (rs = -0.32, p = 0.033). A positive correlation between LMV and %FEV1 in the tidal expiration was observed only in the right lung (rs = 0.25, p = 0.024). LMVs among normal, COPD mild and COPD severe groups were different in the tidal respiration. COPD mild group showed a significantly larger magnitude of LMV compared with the normal group. CONCLUSIONS: In the tidal inspiration, the lung parenchyma moved faster in COPD patients compared with healthy volunteers. VF-DXR was feasible for the assessment of lung parenchyma using LMV.

Vector-Field dynamic X-ray (VF-DXR) using Optical Flow Method.

OBJECTIVES: To explore the feasibility of Vector-Field DXR (VF-DXR) using optical flow method (OFM). METHODS: Five healthy volunteers and five COPD patients were studied. DXR was performed in the standing position using a prototype X-ray system (Konica Minolta Inc., Tokyo, Japan). During the examination, participants took several tidal breaths and one forced breath. DXR image file was converted to the videos with different frames per second (fps): 15 fps, 7.5 fps, five fps, three fps, and 1.5 fps. Pixel-value gradient was calculated by the serial change of pixel value, which was subsequently converted mathematically to motion vector using OFM. Color-coding map and vector projection into horizontal and vertical components were also tested. RESULTS: Dynamic motion of lung and thorax was clearly visualized using VF-DXR with an optimal frame rate of 5 fps. Color-coding map and vector projection into horizontal and vertical components were also presented. VF-DXR technique was also applied in COPD patients. CONCLUSION: The feasibility of VF-DXR was demonstrated with small number of healthy subjects and COPD patients. ADVANCES IN KNOWLEDGE: A new Vector-Field Dynamic X-ray (VF-DXR) technique is feasible for dynamic visualization of lung, diaphragms, thoracic cage, and cardiac contour.

Detection of subclinical atherosclerosis in peripheral arterial beds with B-mode ultrasound: a proposal for guiding the decision for medical intervention and an artifact-corrected volumetric scoring index.

OBJECTIVES: To assess subclinical atherosclerotic cardiovascular disease (ASCVD) using B-mode ultrasound, with special emphasis on the incremental value of performing imaging in multiple peripheral arteries, and to compare imaging findings with traditional risk factors for medical intervention eligibility. METHODS: Data from 2 asymptomatic cohorts from India with unknown ASCVD risk factors were compared to 2 cohorts from North America with known ASCVD risk factors. Carotid and iliofemoral arteries of the Indian cohorts were examined with automated ultrasound in a high-pace environment by non-experts. A simplified metric of atherosclerotic disease burden (FUster-Narula or FUN Score) was developed from 3D imaging data by summing intima-media volume (IMV) over 5-cm arterial segments. Effectiveness of ASCVD prevention guidelines to direct therapy was compared to results from direct imaging. RESULTS: Of the 941 (mean age 44.27 ± 13.76 years, 34% female) enrollees from India, 224 (24%) demonstrated plaques in at least 1 of the 4 arterial sites examined; 107 (11%) had plaques in only the carotids, 70 (7%) in both the carotids and iliofemoral arteries, and 47 (5%) had plaques in only the iliofemoral arteries. Older age and male sex were associated with the presence of plaque, but association with systolic blood pressure was not observed. Data from 2 North American clinics (n = 481, mean age 59.68 ± 11.95 years, 39% female) showed that 203 subjects (42%) had carotid plaque; 82% of whom would not have qualified for lipid-lowering therapy under the Adult Treatment Panel (ATP) III Guidelines. Using the recently published ATP IV Guidelines, 33% of the individuals with carotid plaque would also have failed to qualify for treatment. CONCLUSIONS: B-mode ultrasound examination of bilateral iliofemoral arteries provided an incremental yield in identifying subclinical atherosclerotic disease compared to carotid evaluation alone. Ultrasound examination allowed improved identification of individuals who could be targeted for prophylactic medical intervention compared to ATP III and ATP IV Guidelines.

Rapid Screening for Subclinical Atherosclerosis by Carotid Ultrasound Examination: The HAPPY (Heart Attack Prevention Program for You) Substudy.

BACKGROUND: Cardiovascular disease (CVD)-related death rates have been escalating in emerging economies such as India. A strategy to initiate prophylactic medical intervention by direct identification of subclinical atherosclerotic burden may be appropriate in rural populations where assessment based on traditional risk factors is not available. OBJECTIVES: This study sought to investigate the feasibility of performing rapid automated carotid ultrasound studies in a rural setting and to measure the prevalence of carotid plaques and age-specific distribution of carotid intima-media thickness (IMT) as an index of subclinical atherosclerosis. METHODS: Screening of the extracranial carotid system with automated B-mode ultrasound was performed along with health questionnaire assessments in 771 asymptomatic volunteers (ages 40 ± 14 years; 626 men and 145 women) with no known CVD. Measurements of IMT were recorded as the mean of 24 spatial measurements performed over a 1-cm region in the far wall of the common carotid artery at end diastole; the prevalence of the plaque (focal IMT >1.5 mm) was determined. RESULTS: A total of 69 (8.9%) subjects had atherosclerotic plaques. Of these, 16 (2.1%) exhibited bilateral plaques, 28 (3.6%) left carotid plaque only, and 25 (3.2%) had right carotid plaques. Patients even under 50 years showed a high prevalence of carotid plaques (7%), which increased with age (25% and 35% for 51 to 70 and >70 years, respectively). Only 3 (4.3%) participants with plaques were former smokers. Global mean IMT was 0.55 ± 0.13 mm and correlated with age for both left and right carotid arteries (r = 0.61 and 0.60, p < 0.001 for both) in male as well as female subjects (r = 0.70 and 0.67, p < 0.001 for both), respectively. CONCLUSIONS: Rapid community screening for subclinical atherosclerosis is feasible with automated carotid ultrasound examination and may be beneficial in rural communities of industrializing nations where traditional CVD risk factor data are not yet readily available.

Temporal resolution of the skin impedance measurement in frequency-domain method.

The temporal-resolution of the frequency-domain method for the identification of the impedance locus depends on the basis frequency used in the current waveform construction, i.e., the higher basis frequency provides the better temporal resolution. The impedance locus can be characterized by the impedance parameters Z0, beta, and taum. The frequency distribution of limited number of data in the impedance locus would affect the accuracy of the estimated impedance parameters. Therefore, we investigated the relationship between the estimation accuracy of the impedance parameters and the frequency coverage of the impedance locus in relatively low to high impedance conditions (dc impedance Z0= 51 k ohms - 45 M ohms). As the basis frequency, 100 Hz was enough for the usual impedance with Z0 less than 203 k ohms. On the other hand, 10 Hz and 1 Hz were required for the medium-level (Z0 = 517 k ohms), and high-level (Z0 = 45 M ohms) impedance, respectively. The required basis frequency, accordingly the temporal resolution, depended much on the central relaxation time taum which affects the frequency distribution on the impedance locus. The results of this study are expected to serve as the reference of the frequency selection in the frequency-domain analysis of the skin impedance.