End-Systolic Eccentricity Index Obtained by Enhanced Computed Tomography Is a Predictor of Pulmonary Vascular Resistance in Patients with Chronic Thromboembolic Pulmonary Hypertension.

The usefulness of the parameters of biventricular function simultaneously measured using enhanced multi-detector computed tomography (MDCT) pulmonary angiography in patients with chronic thromboembolic pulmonary hypertension (CTEPH) has not been clarified. This study aimed to verify the correlation between left and right ventricular (RV) parameters and pulmonary vascular resistance (PVR). Patients who underwent enhanced MDCT before diagnostic right heart catheterization at Nagoya University Hospital between October 2014 and April 2021 were enrolled. The correlation of biventricular function and volume parameters with PVR was assessed. Eighty patients were retrospectively analyzed. Patients' mean age was 65 ± 13 years, mean PVR was 9.1 (range, 6.1−11.3) Wood units, and mean end-systolic eccentricity index (esEI) was 1.76 ± 0.50. RV end-systolic volume (ESV) (p = 0.007), RV cardiac output (CO) (p < 0.001), RV ejection fraction (p < 0.001), LV end-diastolic volume (EDV) (p < 0.001), left ventricular (LV) ESV (p = 0.006), LVCO (p < 0.001), end-diastolic EI (p < 0.001), and esEI (p < 0.001) were significantly correlated with PVR. The LVEDV (p = 0.001) and esEI (p < 0.009) were independent predictors of PVR. Systolic pulmonary arterial pressure (PAP) (p < 0.001), diastolic PAP (p < 0.001), mean PAP (p < 0.001), right atrial pressure (p < 0.023), and PVR (p < 0.001) were significantly higher in the high esEI group than in the low esEI group. The esEI was a simple predictor of CTEPH severity.

Computed tomography imaging using split-bolus contrast injection with volume scan of aortic root and heart for preoperative evaluation of transcatheter aortic valve implantation.

The purpose of this study was to investigate using split-bolus contrast injection (SPBI) with volume scanning of the heart and aortic root with helical scanning of the access route, compared to single bolus contrast injection (SI) with variable helical pitch scanning (VHP) of the heart and aortic root and access route in a preoperative evaluation before transcatheter aortic valve implantation (TAVI). Thirty-five patients who underwent preoperative CT before TAVI using SPBI (contrast media: 24.5 mgI /kg/s, injected for 12 s for heart scan and then injected for 8 s for access route) were examined. Electrocardiogram (ECG) gated scans of the heart were performed by volume scan, after a period of time, non-gated helical scans of the aorto-iliac were performed (SPBI method). For comparison, 40 patients who had a single bolus injection (26.5 mg I/kg/s, injected for period of the scan time plus 3 s) and a VHP scan (SI method) before the SPBI method was performed were included in the study. The image qualities of the coronary arteries, aortic root, and access route (aorta-iliac), as well as radiation and iodine doses, were assessed. In visual assessment, image quality of coronary artery was significantly better with the SPBI method (grade; excellent: 57.1% in SPBI vs. 24.3% in SI, p = 0.03). There was no significant difference in image quality of the aortic root by visual assessment. The signal-to-noise (SNR) and contrast-to-noise ratio (CNR) of coronary and aortic root were not significantly different between the two methods. The access route showed significantly higher SNR (45.7 ± 11.5 vs. 34.3 ± 9.8, p < 0.001) and CNR (36.0 ± 9.7 vs. 28.0 ± 8.8, p < 0.001) for the SPBI method. The SPBI method compared to SI method reduced iodine dose by 10% and radiation dose by 45%. Preoperative CT imaging before TAVI using SPBI with volume scan is useful and can reduce iodine and radiation doses.

A comparison of automatic and manual compensation methods for the calculation of tube currents during off-centered patient positioning with a noise-based automatic exposure control system in computed tomography.

Automatic exposure control (AEC) is used to optimize the X-ray tube output during computed tomography (CT) scans. However, calculation of the tube current by AEC can be affected when a patient is not aligned with the rotational center of the X-ray tube. An automatic couch height-positioning compensation mechanism provides a corrective function when the patient is off-center. In this study, we aimed to (a) evaluate the performance characteristics of the positioning compensation mechanism and (b) confirm whether our proposed compensation method can be properly applied to a noise-based AEC system even if the CT device is not equipped with a positioning compensation mechanism. An elliptical phantom was scanned at various table heights on systems without/with the positioning compensation mechanism. Expressions describing the offset from the gantry's isocenter and adjusted standard deviation settings were derived and used in our proposed compensation method. A phantom was scanned at various table heights with our proposed compensation method, and volume CT dose index (CTDIvol) and image noise levels were obtained. An anthropomorphic chest phantom was also scanned using the proposed compensation method to verify its accuracy. When the positioning compensation mechanism was used, it yielded a constant CTDIvol and image noise levels at various table heights tested. A comparison between our proposed method and the positioning compensation mechanism for both the elliptical and chest phantoms yielded similar CTDIvol. Therefore, both automatic and manual positioning compensation methods are useful for avoiding AEC miscalculations in off-centered patient positioning cases.

Incidental findings on computed tomography for preoperative assessment before transcatheter aortic valve implantation in Japanese patients.

Extra-cardiovascular incidental findings (IFs) on preoperative computed tomography (CT) are frequently observed in transcatheter aortic valve implantation (TAVI) candidates. However, the backgrounds of TAVI candidates and comorbidities differ based on the race and/or country, and data on IFs in a specific population are not always applicable to another. The aim of this study was to assess the prevalence, type, and clinical impact of IFs in Japanese TAVI candidates. This was a retrospective, single-center, observational study. CT reports of 257 TAVI candidates were reviewed, and IFs were classified as (a) insignificant: findings that did not require further investigation, treatment, or follow-up; (b) intermediate: findings that needed to be followed up or were considered for further investigation but did not affect the planning of TAVI; and (c) significant: findings that required further investigation immediately or affected the planning of TAVI. At least one IF was found in 254 patients (98.8%). Insignificant, intermediate, and significant IFs were found in 253 (98.4%), 153 (59.5%), and 34 (13.2%) patients, respectively. Newly indicated significant IFs were found in 19 patients (7.4%). In 2 patients (0.8%), TAVI was canceled because of significant IFs. In patients who consequently underwent TAVI, the presence of significant IFs was not associated with the duration from CT performance to TAVI [28 (19-40) days vs. 27 (19-43) days, p = 0.74] and all-cause mortality during the median follow-up period of 413 (223-805) days (p = 0.44). Almost all Japanese TAVI candidates had at least one IF, and the prevalence of significant IFs was not negligible. Although the presence of significant IFs was not associated with mid-term mortality, appropriate management of IFs was considered important.

Assessment of Severity in Chronic Thromboembolic Pulmonary Hypertension by Quantitative Parameters of Dual-Energy Computed Tomography.

OBJECTIVE: The objective of this study was to assess the correlation between dual-energy computed tomography quantitative parameters and hemodynamics in patients with chronic thromboembolic pulmonary hypertension. METHODS: Dual-energy computed tomography of 52 chronic thromboembolic pulmonary hypertension patients were evaluated retrospectively. The mean lung perfused blood volume (lung PBV) and the mean pulmonary artery (PA) enhancement measured at pulmonary parenchymal phase were compared with the hemodynamics by Spearman rank correlation coefficient (rs) and receiver operating characteristic analysis. RESULTS: Lung PBV was correlated with mean pulmonary arterial pressure (rs = 0.47, P < 0.001). Pulmonary artery enhancement was correlated with cardiac index (rs = -0.49, P < 0.001) and pulmonary vascular resistance (rs = 0.48, P < 0.001). The areas under the curves were 0.86 for lung PBV to predict mean pulmonary arterial pressure of >50 mm Hg and 0.86 for PA enhancement to predict pulmonary vascular resistance of >1000 dyne·s/cm. CONCLUSIONS: Lung PBV and PA enhancement could be indicators of hemodynamics.

Pin-photodiode array for the measurement of fan-beam energy and air kerma distributions of X-ray CT scanners.

PURPOSE: Patient dose estimation in X-ray computed tomography (CT) is generally performed by Monte Carlo simulation of photon interactions within anthropomorphic or cylindrical phantoms. An accurate Monte Carlo simulation requires an understanding of the effects of the bow-tie filter equipped in a CT scanner, i.e. the change of X-ray energy and air kerma along the fan-beam arc of the CT scanner. To measure the effective energy and air kerma distributions, we devised a pin-photodiode array utilizing eight channels of X-ray sensors arranged at regular intervals along the fan-beam arc of the CT scanner. METHODS: Each X-ray sensor consisted of two plate type of pin silicon photodiodes in tandem - front and rear photodiodes - and of a lead collimator, which only allowed X-rays to impinge vertically to the silicon surface of the photodiodes. The effective energy of the X-rays was calculated from the ratio of the output voltages of the photodiodes and the dose was calculated from the output voltage of the front photodiode using the energy and dose calibration curves respectively. RESULTS: The pin-photodiode array allowed the calculation of X-ray effective energies and relative doses, at eight points simultaneously along the fan-beam arc of a CT scanner during a single rotation of the scanner. CONCLUSIONS: The fan-beam energy and air kerma distributions of CT scanners can be effectively measured using this pin-photodiode array.