Photon-Counting Detector CT: Potential for 75% Reduction in Contrast Medium Amount: A Phantom Study.

This study aimed to evaluate the potential reduction in contrast medium utilization using photon-counting detector computed tomography (PCD-CT). One PCD-CT scan (CT1) and three conventional (non-PCD-CT) CT scans (CT2-CT4) were performed using a multi-energy CT phantom that contained eight rods with different iodine concentrations (0.2, 0.5, 1, 2, 5, 10, 15, and 20 mg/ml). The CT values of the seven groups (CT1 for 40, 50, 60, and 70 keV; and CT2-4) were measured. Noise and contrast-to-noise ratio (CNR) were assessed for the eight rods at various iodine concentrations. CT2 and CT1 (40 keV) respectively required 20 mg/ml and 5 mg/ml of iodine, indicating that a comparable contrast effect could be obtained with approximately one-fourth of the contrast medium amount. The standard deviation values increased at lower energy levels irrespective of the iodine concentration. The CNR exhibited a decreasing trend with lower iodine concentrations, while it remained relatively stable across all iodine levels (40-70 keV). This study demonstrated that virtual monochromatic 40 keV images offer a similar contrast effect with a reduced contrast medium amount when compared to conventional CT systems at 120 kV.

Depiction rate of feeding arteries of renal cell carcinoma on four-dimensional computed tomography angiography.

PURPOSE: To retrospectively evaluate the depiction rate of feeding arteries in biopsy-proven clear cell renal cell carcinoma (CCRCC) on four-dimensional computed tomography angiography (4D-CTA) images. MATERIALS AND METHODS: This study included 22 patients with 22 CCRCC and 30 feeding arteries treated with transcatheter renal artery embolization. The depiction rate of the feeding arteries on preprocedural 4D-CTA was evaluated. Images were acquired by 320-row multi-detector computed tomography (CT) 15‒36 s after starting to inject a contrast agent (600 mg/kg iodine) intravenously into patients at 2.1 s intervals (11 phases). Two board-certified radiologists retrospectively assessed the feeder depiction rate in all 11 phases with reference to the procedural images as the gold standard. Discrepancies were resolved by consultation with a third radiologist. RESULTS: Among the feeders, 11 (36.7%) were segmental or lobar, and 19 (63.3%) were interlobar or arcuate arteries. The feeder depiction rate was the highest (25 [83.3%] of 30) in the 5th phase (delay, 23.4 s) where the gap in contrast enhancement between the renal artery and cortex was the largest. This was followed by the 6th (23 [76.7%] of 30), 4th (22 [73.3%] of 30]), and 7th (21 [70.0%] of 30) phases. The overall rate of depicting feeding arteries in the 11 phases of 4D-CTA was 28 (93.3%) of 30. CONCLUSIONS: The depiction rate of CCRCC feeding arteries including lobar or smaller artery branches by 4D-CTA was favorable. The feeding arteries were optimally visualized during the phase with the largest contrast gap between the renal artery and cortex.

Diagnostic improvements of calcium-removal image reconstruction algorithm using photon-counting detector CT for calcified coronary lesions.

OBJECTIVE: To investigate the diagnostic performance of a calcium-removal image reconstruction algorithm with photon-counting detector-computed tomography (PCD-CT), a technology that hides only the calcified plaque from the spectral data in coronary calcified lesions. METHODS: This retrospective study included 17 patients who underwent PCD-coronary CT angiography (CCTA) with at least one significant coronary stenosis (≥50 %) with calcified plaque by CCTA and invasive coronary angiography (ICA) performed within 60 days of CCTA. A total of 162 segments with calcified plaque were evaluated for subjective image quality using a 4-point scale. Their calcium-removal images were reconstructed from conventional images, and both images were compared with ICA images as the reference standard. The contrast-to noise ratios for both images were calculated. RESULTS: Conventional and calcium-removal images had a subjective image quality of 2.7 ± 0.5 and 3.2 ± 0.9, respectively (p < 0.001). The percentage of segments with a non-diagnostic image quality was 32.7 % for conventional images and 28.3 % for calcium-removal images (p < 0.001). The segment-based diagnostic accuracy revealed an area under the receiver operating characteristic curve of 0.87 for calcium-removal images and 0.79 for conventional images (p = 0.006). Regarding accuracy, the specificity and positive predictive value of calcium-removal images were significantly improved compared with those of conventional images (80.5 % vs. 69.5 %, p = 0.002 and 64.1 % vs. 52.0 %, p < 0.001, respectively). The objective image quality of the mean contrast-to-noise ratio did not differ between the images (13.9 ± 3.6 vs 13.3 ± 3.4, p = 0.356) CONCLUSIONS: Calcium-removal images with PCD-CT can potentially be used to evaluate diagnostic performance for calcified coronary artery lesions.

Evaluation of the ear ossicles with photon-counting detector CT.

Recently, computed tomography with photon-counting detector (PCD-CT) has been developed to enable high-resolution imaging at a lower radiation dose. PCD-CT employs a photon-counting detector that can measure the number of incident X-ray photons and their energy. The newly released PCD-CT (NAEOTOM Alpha, Siemens Healthineers, Forchheim, Germany) has been in clinical use at our institution since December 2022. The PCD-CT offers several advantages over current state-of-the-art energy-integrating detector CT (EID-CT). The PCD-CT does not require septa to create a detector channel, while EID-CT does. Therefore, downsizing the anode to achieve higher resolution does not affect the dose efficiency of the PCD-CT. CT is an indispensable modality for evaluating ear ossicles. The ear ossicles and joints are clearly depicted by PCD-CT. In particular, the anterior and posterior legs of the stapes, which are sometimes unclear on conventional CT scans, can be clearly visualized. We present cases of congenital anomalies of the ossicular chain, ossicular chain dislocation, tympanosclerosis, and cholesteatoma in which PCD-CT was useful. This short article reports the usefulness of PCD-CT in the 3D visualization of the ear ossicles.

Association between higher pericoronary adipose tissue attenuation measured by coronary computed tomography angiography and nonalcoholic fatty liver disease: A matched case-control study.

ABSTRACT: Non-alcoholic fatty liver disease (NAFLD) is a risk factor for cardiac mortality. Pericoronary adipose tissue (PCAT) attenuation, expressed by the fat attenuation index on coronary computed tomography angiography, reflects pericoronary inflammation. We aimed to investigate the association between PCAT attenuation and NAFLD.This is a single-center cohort study comprising of patients who underwent coronary computed tomography angiography for suspected stable coronary artery disease between January and December 2020. Patient characteristics and coronary computed tomography angiography findings were analyzed between patients with NAFLD (n = 78) and a propensity score-matched cohort of patients without NAFLD (n = 78). PCAT attenuation was assessed in Hounsfield units (HU) of proximal 40-mm segments of the left anterior descending artery (LAD) and right coronary artery.The mean PCAT attenuation in LAD and right coronary artery were significantly higher in patients with NAFLD than those without NAFLD. When patients were divided into 2 groups using the median LAD-PCAT attenuation of -72.5 HU, the high PCAT attenuation group had more males (82% vs 67%, P = .028) and NAFLD patients (63% vs 37%, P = .001) compared to the low PCAT attenuation group. No differences in age, body mass index, conventional cardiovascular risk factors, or the presence of high-risk plaque were observed between the 2 groups. In the multivariate logistic analysis, NAFLD was independently associated with high PCAT attenuation (odds ratio 2.912, 95% confidence interval 1.386 to 6.118, P = .005).NAFLD is associated with high PCAT attenuation on coronary computed tomography angiography. This finding suggests that pericoronary inflammation is involved in the increased cardiac mortality in NAFLD patients.

Bone microarchitectural analysis using ultra-high-resolution CT in tiger vertebra and human tibia.

BACKGROUND: To reveal trends in bone microarchitectural parameters with increasing spatial resolution on ultra-high-resolution computed tomography (UHRCT) in vivo and to compare its performance with that of conventional-resolution CT (CRCT) and micro-CT ex vivo. METHODS: We retrospectively assessed 5 tiger vertebrae ex vivo and 16 human tibiae in vivo. Seven-pattern and four-pattern resolution imaging were performed on tiger vertebra using CRCT, UHRCT, and micro-CT, and on human tibiae using UHRCT. We measured six microarchitectural parameters: volumetric bone mineral density (vBMD), trabecular bone volume fraction (bone volume/total volume, BV/TV), trabecular thickness (Tb.Th), trabecular number (Tb.N), trabecular separation (Tb.Sp), and connectivity density (ConnD). Comparisons between different imaging resolutions were performed using Tukey or Dunnett T3 test. RESULTS: The vBMD, BV/TV, Tb.N, and ConnD parameters showed an increasing trend, while Tb.Sp showed a decreasing trend both ex vivo and in vivo. Ex vivo, UHRCT at the two highest resolutions (1024- and 2048-matrix imaging with 0.25-mm slice thickness) and CRCT showed significant differences (p ≤ 0.047) in vBMD (51.4 mg/cm3 and 63.5 mg/cm3 versus 20.8 mg/cm3), BV/TV (26.5% and 29.5% versus 13.8 %), Tb.N (1.3 l/mm and 1.48 l/mm versus 0.47 l/mm), and ConnD (0.52 l/mm3 and 0.74 l/mm3 versus 0.02 l/mm3, respectively). In vivo, the 512- and 1024-matrix imaging with 0.25-mm slice thickness showed significant differences in Tb.N (0.38 l/mm versus 0.67 l/mm, respectively) and ConnD (0.06 l/mm3 versus 0.22 l/mm3, respectively). CONCLUSIONS: We observed characteristic trends in microarchitectural parameters and demonstrated the potential utility of applying UHRCT for microarchitectural analysis.

Image Quality of Coronary Computed Tomography Angiography with 320-Row Area Detector Computed Tomography in Children with Congenital Heart Disease.

The objective of this study was to assess factors affecting image quality of 320-row computed tomography angiography (CTA) of coronary arteries in children with congenital heart disease (CHD). We retrospectively reviewed 28 children up to 3 years of age with CHD who underwent prospective electrocardiography (ECG)-gated 320-row CTA with iterative reconstruction. We assessed image quality of proximal coronary artery segments using a five-point scale. Age, body weight, average heart rate, and heart rate variability were recorded and compared between two groups: patients with good diagnostic image quality in all four coronary artery segments and patients with at least one coronary artery segment with nondiagnostic image quality. Altogether, 96 of 112 segments (85.7 %) had diagnostic-quality images. Patients with nondiagnostic segments were significantly younger (10.0 ± 11.6 months) and had lower body weight (5.9 ± 2.9 kg) (each p < 0.05) than patients with diagnostic image quality of all four segments (20.6 ± 13.8 months and 8.4 ± 2.5 kg, respectively; each p < 0.05). Differences in heart rate and heart rate variability between the two imaging groups were not significant. Receiver operating characteristic analyses for predicting patients with nondiagnostic image quality revealed an optimal body weight cutoff of ≤5.6 kg and an optimal age cutoff of ≤12.5 months. Prospective ECG-gated 320-row CTA with iterative reconstruction provided feasible image quality of coronary arteries in children with CHD. Younger age and lower body weight were factors that led to poorer image quality of coronary arteries.

Comprehensive assessment of morphology and severity of atrial septal defects in adults by CT.

BACKGROUND: Cardiac CT is an excellent tool for evaluating the anatomy of a secundum atrial septal defect (ASD). However, a comprehensive assessment of its usefulness, including measurement of the pulmonary to systemic blood flow ratio in secundum ASD patients, has not been performed. OBJECTIVE: Therefore, this study was designed to evaluate the usefulness of CT for assessing the hemodynamics of secundum ASD in adults compared with transesophageal echocardiography (TEE), transthoracic echocardiography, and invasive catheterization. METHODS: Fifty adult patients with secundum ASD were enrolled. Cardiac CT scans (128-slice multidetector CT instrument) were acquired. These were followed by 2-dimensional reconstruction of the secundum ASDs to determine the defect size, the rim length between the outer edge of the defect, and the pulmonary to systemic blood flow (Qp/Qs) ratio. RESULTS: The maximum sizes of the secundum ASDs derived from CT and TEE studies were comparable (21.2 ± 8.0 vs. 20.0 ± 7.3 mm; P = .41; r = 0.960; P < .001). The rim lengths for the aortic, mitral, and tricuspid valves; the inferior vena cava; and posterior atrium were also comparable between CT and TEE measurements. The mean Qp/Qs ratio that was derived from CT measurements was comparable with that found by invasive catheterization (2.3 ± 0.7 vs. 2.3 ± 0.8; P = .73; r = 0.786; P < .001). CONCLUSION: Cardiac CT is feasible for assessing pathology and the severity of secundum ASD in adults.

Differential association of visceral adipose tissue with coronary plaque characteristics in patients with and without diabetes mellitus.

BACKGROUND: Excess visceral adipose tissue (VAT) is closely associated with the presence of coronary artery plaques that are vulnerable to rupture. Patients with diabetes mellitus (DM) have more VAT than patients without DM, but the extent to which VAT contributes to the characteristics of coronary plaques before and after the development of DM is not fully understood. METHODS: We retrospectively evaluated 456 patients (60% male, age 64 ± 16 years) who were suspected to have cardiovascular disease and underwent 64-slice computed tomography angiography (CTA). Seventy-one (16%) patients had vulnerable plaques (CT density < 50 Hounsfield Units, positive remodeling index > 1.05, and adjacent spotty areas of calcification). RESULTS: Patients were divided into tertiles according to the VAT area. There were stepwise increases in noncalcified and vulnerable plaques with increasing tertiles of VAT area in patients without DM, but not in patients with DM. Multivariate analysis showed that a larger VAT area was significantly associated with a higher risk of vulnerable plaque in patients without DM (odds ratio 3.17, 95% confidence interval 1.08-9.31, p = 0.04), but not in patients with DM. CONCLUSIONS: The VAT area is associated with the characteristics of coronary plaques on CTA in patients without DM, but not in patients with DM. VAT may be a significant cardiometabolic risk factor that is associated with plaque vulnerability before the development of DM. CTA findings may help to improve risk stratification in such patients.

Safety and efficacy of a bolus injection of landiolol hydrochloride as a premedication for multidetector-row computed tomography coronary angiography.

BACKGROUND: We evaluated the safety and efficacy of a bolus injection of landiolol hydrochloride, an ultrashort-acting ß1-selective antagonist, as an additional treatment after premedication with an oral ß-blocker to reduce heart rate prior to multidetector-row computed tomography (MDCT) coronary angiography (CAG). METHODS AND RESULTS: A total of 458 patients who underwent MDCT CAG were retrospectively enrolled. Image quality and hemodynamic parameters were compared in patients before and after approval of landiolol hydrochloride. If heart rate reduction was insufficient after premedication with an oral ß-blocker, a bolus injection of landiolol hydrochloride (n=66) or other drugs (n=30) was used. The percentage of evaluable images per segment in patients after approval of landiolol (99.3%) was greater than that in patients before approval of landiolol (97.4%, P<0.01). Heart rates before scanning in patients receiving landiolol hydrochloride were similar to those receiving other drugs. Heart rate was significantly reduced approximately 5 min after injection of landiolol hydrochloride and increased shortly. No decrease in systolic blood pressure or other adverse effects was observed. CONCLUSIONS: Bolus injection of landiolol hydrochloride sufficiently reduced heart rate without significantly reducing systolic blood pressure and produced a high percentage of evaluable images, suggesting that bolus injection of landiolol hydrochloride as an additional pretreatment is feasible in MDCT CAG.