Investigative Radiology最新文献

Objectives: Intramyocardial hemorrhage (IMH) is the most severe form of injury associated with reperfusion therapy during acute myocardial infarction (AMI). Although T2*-weighted cardiac MRI is regarded as the reference standard for IMH detection, its application is limited in the hyperacute phase. Ferumoxytol, an iron-based contrast agent characterized by potent T1-shortening and a long intravascular half-life, may enable earlier detection. This study assessed a T1-weighted approach using ferumoxytol-enhanced MRI (FE-MRI) for early detection of IMH after ischemia-reperfusion injury in a swine model.

Materials and methods: IMH was induced in 22 Yorkshire swine using a closed-chest ischemia-reperfusion model with intracoronary collagenase administration. FE-MRI was performed immediately after reperfusion using T1-weighted cine imaging and serial T1 mapping with a modified Look-Locker inversion recovery (MOLLI) pulse sequence. Imaging findings were compared among IMH-positive (IMH+), IMH-negative (IMH-), and control animals. Results were validated through gross pathology, histology, and electron microscopy.

Results: Nine animals completed imaging, of which 5 were IMH+ and 4 IMH- based on histopathology and FE-MRI. In IMH+ animals, the T1 within hemorrhagic reperfused myocardium was significantly lower than remote myocardium [420.8 ms (380.5, 656.3) vs. 806.0 ms (781.0, 818.8); P <0.001], and lower than healthy myocardium in the control animal [808.2 ms (796.3, 811.0)]. IMH- animals exhibited significantly higher myocardial T1 than IMH+ animals in both non-hemorrhagic reperfused [807.8 ms (786.1, 830.3); P <0.001] and remote myocardium [805.6 ms (786.1, 825.5); P <0.001]. A mixed-effects model confirmed significant cohort-specific T1 decrease within hemorrhagic reperfused tissue of IMH+ animals (estimate= -0.49±0.15; P =0.001), with a significant time-dependent effect (β= -0.125±0.03; P <0.001). Remote myocardial and left ventricular blood pool T1 did not differ between groups (both P >0.05). Gross and microscopic findings confirmed extravasated erythrocytes and disrupted myocardial architecture, consistent with hemorrhagic injury.

Conclusions: This proof-of-concept study demonstrates the feasibility and potential of T1-weighted FE-MRI as a unique approach for detecting IMH immediately after ischemia-reperfusion injury. Early identification of IMH by FE-MRI may facilitate translational efforts to develop and evaluate targeted therapies that reduce IMH burden and improve post-AMI outcomes.

Background: Despite the growing number of artificial intelligence (AI)-based applications used in radiology, no structured framework exists to assess their case-level reliability or to document overridden outputs in reports.

Purpose: To develop and evaluate the Artificial Intelligence Reporting and Data System (AI-RADS), a structured framework for an objective, case-level assessment of AI output reliability, clinical utility, and recommended actions in radiology.

Materials and methods: The AI-RADS framework was tested in a retrospective, multireader study. Here, 5 board-certified radiologists independently evaluated 350 cases processed by 7 representative AI applications for image-based and generative tasks. Each case was assigned one of 5 AI-RADS categories, applicable modifiers, and an independent correctness rating as a reference. Interreader agreement was quantified using Krippendorff's α with 95% CIs.

Results: Substantial interreader agreement was observed for the core AI-RADS categories in both image-based (Krippendorff's α=0.87; 95% CI: 0.83-0.91) and generative AI tasks (Krippendorff's α=0.93; 95% CI: 0.91-0.95). Reader-assigned correctness aligned well with AI-RADS categories 1 to 2, which indicate outputs suitable for integration into clinical workflows. Outputs rated as "incorrect" were predominantly assigned to categories 4 to 5, warranting override or removal from display.

Conclusion: AI-RADS provides a structured framework for the case-level evaluation of AI output reliability, clinical utility, and consequences for report communication. This multireader study demonstrated substantial interreader agreement and applicability across various AI applications.

Objectives: To evaluate the contrast enhancement of the breast parenchyma in MRI using gadopiclenol (GP) at half the standard dose of gadolinium compared with gadobutrol (GB) at the standard dose of gadolinium.

Materials and methods: This retrospective, single-center study considered 319 consecutive female patients who underwent breast MRI with a half-standard dose of gadopiclenol (0.05 mmol/kg) between January and March of 2025. Complete data sets of patients who had received a prior cycle-appropriate MRI using a standard dose of gadobutrol (0.1 mmol/kg) within 2 years, without interim therapy, were evaluated. Absolute signal enhancement of the aorta, axillary lymph nodes, and breast parenchyma was measured to provide an objective assessment. Two independent radiologists evaluated subjective image quality and diagnostic confidence using a 5-point Likert Scale in a side-by-side comparison. Statistical analyses were performed using Wilcoxon signed-rank tests and weighted Cohen kappa.

Results: A total of 145 patients (mostly with hereditary breast and ovarian cancer syndrome) met the inclusion criteria. GP revealed significantly higher absolute enhancement values for all regions (eg, breast parenchyma: GP: 41.8, IQR: 27.1 to 65.4 vs GB: 33.4, IQR: 21.6 to 56.3; P < 0.001). Both contrast agents achieved excellent overall diagnostic confidence ratings (5; IQR: 4 to 5) and demonstrated moderate agreement (GP: κ = 0.59/ GB: κ = 0.48). GP received more excellent ratings (71.9% vs 56.8%; P = 0.002). Most pairs were considered equal on terms of image quality (R1: 90/145; R2: 92/145; P = 0.845) with fair agreement (κ = 0.366). Agreement was achieved in 97 of the 145 cases (67 "equal," 21 "pro GP", and 9 "pro GB"). The combination "equal & pro GP" accounted for most of the remaining comparisons (37/48).

Conclusion: Breast MRI using gadopiclenol with half standard gadolinium dose offers equivalent to superior objective contrast enhancement and subjective diagnostic confidence compared with a gadobutrol-enhanced MRI with full standard gadolinium dose.

Since the discovery of gadolinium (Gd) in the brain following the administration of gadolinium-based contrast agents (GBCAs), considerable progress has been made in understanding their pharmacokinetics and neurotoxicology. This review summarizes animal studies assessing the presence of Gd after GBCA administration, with a specific focus on functional and behavioral outcomes, rather than providing a comprehensive overview of all aspects of Gd presence in the brain. These findings indicate that Gd accumulation in the brain depends on the chemical structure of GBCAs, with linear agents exhibiting greater retention and slower clearance than macrocyclic agents. Gd distribution is nonhomogeneous, primarily localized in deep gray matter structures, and is influenced by cerebrospinal fluid-mediated transport and perivascular deposition. Although motor and cognitive functions are generally unaffected under normal conditions, prolonged exposure to linear GBCAs or preexisting conditions such as inflammation or metabolic disorders may increase neurotoxic risks, resulting in motor and cognitive deficits. Pain and sensory hypersensitivity are frequently and reproducibly observed, particularly when linear agents are used. We will also discuss the potential mechanisms of neurotoxicity caused by free Gd3+ ion. However, these mechanistic findings are limited because the studies cannot be extrapolated to clinical practice. Future studies should investigate the potential associations between GBCA exposure and neurodegenerative diseases. These insights are essential for enhancing GBCA safety and informing clinical guidelines.

Objectives: Photon-counting CT (PCCT) represents a newer CT technology with reduced electronic noise and potentially better dose efficiency than conventional CT. However, it remains unclear how vertical off-center positioning affects dose and image quality across a spectrum of patient sizes. The aim was to quantify the effects of vertical off-centering on radiation dose and image noise in PCCT using anthropomorphic phantoms representing both adult and pediatric body sizes.

Materials and methods: Three anthropomorphic phantoms (adult male, 10-year-old, and 5-year-old) were scanned on a commercially available PCCT system at multiple vertical offsets using a posteroanterior localizer with the x-ray tube positioned below the phantom. Chest and abdomen protocols were used, with radiation doses, Monte Carlo-simulated organ doses, and image noise recorded at each offset.

Results: Off-centering markedly affected radiation dose, whereas image noise differed primarily between the predefined image quality levels. A strong linear relationship was observed between vertical offset and CTDIvol [median R2 (IQL) = 0.85 (0.78-0.98)]. Downward off-centering (-4 cm) increased radiation dose by up to 16% in adults and 17% in pediatric phantoms for both chest and abdominal scans, with the largest effects in chest scans without tin filtration. Upward off-centering (+4 cm) reduced dose by up to 11% in adults and 8% in pediatric phantoms. Larger phantoms showed steeper regression slopes, indicating stronger dose dependence on positioning. In contrast, no consistent dependence of image noise on vertical off-centering was observed within a given image quality level [median R2 = 0.23 (0.03-0.52)]. Across all offsets, the overall variation reached +72%/-47% in chest PCCT and +66%/-13% in abdominal PCCT.

Conclusions: Vertical off-center positioning substantially affects radiation dose in PCCT, whereas image noise appears largely independent of vertical positioning within a given image quality level. Meticulous isocenter alignment remains crucial for both adult and pediatric imaging to avoid unnecessary radiation and sustain diagnostic image quality.

Background: Photon-counting CT (PCD-CT) provides spectral imaging in every clinical scan through virtual monoenergetic image (VMI) reconstruction. However, because conventional iodine-based contrast medium has a low k-edge, image contrast in the VMIs decreases at high energies. Contrast media with higher k-edges may improve contrast in high-energy VMIs. Therefore, this study investigates BAY3685750, a novel iodine-gadolinium hybrid contrast medium.

Materials and methods: In vitro experiments compared BAY3685750 with conventional iodine-based and gadolinium-based contrast agents in an anthropomorphic abdominal phantom. Relaxivity (r1) of BAY3685750 was measured at 1.41 T in water and human plasma to assess its potential for both MRI and CT applications. Next, 3 Göttingen minipigs underwent multiphasic contrast-enhanced upper abdominal CT on a first-generation PCD-CT. In 2 animals, BAY3685750 was administered for the first scan, followed by a 60-minute washout and a second multiphasic scan with a standard iodine-based contrast medium. In the third animal, the order was reversed. VMIs were reconstructed for all scans, enabling intraindividual comparison of the 2 contrast agents.

Results: In the phantom study, BAY3685750 produced higher attenuation than the iodine-based contrast medium and lower attenuation than the gadolinium-based medium. Relative to the iodine medium, BAY3685750 attenuation increased continuously with energy, reaching ~20% (70 keV), 36% (100 keV), and 78% (140 keV) higher values. In vivo, all measured structures (aorta, inferior vena cava, portal vein, liver) had higher attenuation with BAY3685750 than with iodine at all phases and VMIs. The r1 relaxivity of BAY3685750 in human plasma (1.41 T) was 8.95 L mmol-1s-1 compared with 5.93 L mmol-1s-1 for gadobutrol.

Conclusion: The hybrid iodine-gadolinium contrast medium BAY3685750 provides higher attenuation than conventional iodine-based CT contrast, suggesting improved image quality in high-energy VMIs.

Objectives: MR neurography (MRN) is a modern technique for visualizing peripheral nerves and quantifying microstructural pathology, yet its use in pediatric populations remains largely unexplored. This study evaluates the applicability and diagnostic performance of MRN in children and adolescents with genetically confirmed long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency (LCHADD) and mitochondrial trifunctional protein deficiency (MTPD), in which peripheral neuropathy is a known long-term complication.

Materials and methods: In a prospective cross-sectional study, 15 patients (LCHADD n = 6; MTPD n = 9) and 14 age-matched controls underwent high-resolution mid-thigh MRN of the sciatic nerve to assess (1) T2-based lesion burden for tibial (SNTib) and peroneal (SNPer) fascicles, (2) functional nerve integrity of the tibial fascicles using diffusion tensor metrics, including fractional anisotropy (FA) and radial diffusivity (RD), and (3) tibial fascicle-based T2 relaxometry parameters. In addition, clinical and electrophysiological data were obtained. Age-adjusted linear regression, ROC analyses, and linear discriminant analyses (LDA) quantified group effects and classification performance.

Results: Overall, patients showed higher T2 lesion burden compared with controls (SNTib: +2.75%, P = 0.001; SNPer: +1.94%, P = 0.001), reduced tibial fascicle FA (Δ: -0.098, P = 0.001), and increased tibial fascicle RD (Δ: +147.4×10-6 mm2/s, P = 0.011). Subgroup comparisons between LCHADD and MTPD revealed no significant differences. Of the 15 patients, 7 exhibited signs of clinical neuropathy. Neuropathic individuals showed pronounced abnormalities (SNTib: +4.22%, P < 0.001; SNPer: +2.29%, P = 0.002; ΔFA: -0.138, P < 0.001), while even those without clinical neuropathy exhibited elevated SNPer lesion burden (+1.64%; P = 0.018) and reduced tibial fascicle FA (Δ: -0.062, P = 0.03), compared with controls, indicating subclinical involvement. SNTib lesion burden showed excellent discrimination (AUC: 95.2%), and FA performed well (AUC: 81.2%). Multiparametric LDA achieved 93% apparent in-sample accuracy for patients versus controls, 86% for LCHADD versus MTPD, and 90% for classifying neuropathic, non-neuropathic, and control groups.

Conclusions: MRN can be readily applied in children and adolescents and sensitively detects both clinically manifest and subclinical peripheral nerve involvement in long-chain fatty acid oxidation disorders. Extending this capability, exploratory LDA suggests that combining multiple MRN metrics may provide complementary diagnostic and phenotypic information beyond individual parameters.

Background and objectives: Following endovascular repair of an aortic aneurysm, patients need regular surveillance using CT to exclude endoleaks. The optimal technical parameters for photon-counting detector CT (PCD-CT) have not yet been established in this clinical context. This study examines the impact of the ultra-high resolution (UHR) mode and monoenergetic reconstructions at various keV on the detection of small endoleaks in experimental settings.

Materials and methods: An aneurysm phantom model mimicking medium- and large-sized patients was scanned using PCD-CT. Monoenergetic images (MEIs) were reconstructed with standard resolution at 40, 45, 50, 55, and 60 keV and with UHR at 45, 50, and 55 keV. Three independent blinded radiologists assessed 80 CT series containing 2880 simulated endoleaks with diameters of 2, 4, and 6 mm. The observers' ratings were analyzed and compared with the jackknife alternative free-response operational characteristics (JAFROC1) method by calculating a figure-of-merit for the performance ( A1 ). The Spearman R was calculated for the correlation between A1 and objective image quality.

Results: The best readers' performance was achieved with the 50 keV UHR, 55 keV standard, 55 keV UHR, and 60 keV standard series ( A1 =0.66 to 0.72) in the medium and with the 55 keV standard, 55 keV UHR, and 60 keV standard reconstructions ( A1 = 0.40 to 0.49) in the large phantom. UHR provided higher A1 than the standard reconstruction at 50 keV for 4 to 6 mm endoleaks ( A1 , 0.82 vs. 0.72; P =0.015 in medium and 0.42 vs. 0.30; P =0.028 in large phantom) and for 6 mm endoleaks ( A1 , 0.93 vs. 0.83; P =0.002 in medium and 0.53 vs. 0.36; P =0.013 in large phantom). In both phantoms, readers' performance correlated negatively with image noise (Spearman R =-0.83; P =0.01 in the medium and Spearman R =-0.98; P <0.001 in the large phantom) and showed no correlation with the contrast-to-noise ratio of endoleaks ( P =0.91 and 0.73).

Conclusions: The 55 keV standard or UHR and 60 keV standard reconstructions yielded the best performance for detecting small endoleaks with PCD-CT. The UHR mode improved performance at 50 keV for 4 to 6 mm and 6 mm endoleaks.