Investigative Radiology最新文献

Objectives: Double-dose contrast-enhanced brain imaging improves tumor delineation and detection of occult metastases but is limited by concerns about gadolinium-based contrast agents' effects on patients and the environment. The purpose of this study was to test the benefit of a deep learning-based contrast signal amplification in true single-dose T1-weighted (T-SD) images creating artificial double-dose (A-DD) images for metastasis detection in brain magnetic resonance imaging.

Materials and methods: In this prospective, multicenter study, a deep learning-based method originally trained on noncontrast, low-dose, and T-SD brain images was applied to T-SD images of 30 participants (mean age ± SD, 58.5 ± 11.8 years; 23 women) acquired externally between November 2022 and June 2023. Four readers with different levels of experience independently reviewed T-SD and A-DD images for metastases with 4 weeks between readings. A reference reader reviewed additionally acquired true double-dose images to determine any metastases present. Performances were compared using Mid-p McNemar tests for sensitivity and Wilcoxon signed rank tests for false-positive findings.

Results: All readers found more metastases using A-DD images. The 2 experienced neuroradiologists achieved the same level of sensitivity using T-SD images (62 of 91 metastases, 68.1%). While the increase in sensitivity using A-DD images was only descriptive for 1 of them (A-DD: 65 of 91 metastases, +3.3%, P = 0.424), the second neuroradiologist benefited significantly with a sensitivity increase of 12.1% (73 of 91 metastases, P = 0.008). The 2 less experienced readers (1 resident and 1 fellow) both found significantly more metastases on A-DD images (resident, T-SD: 61.5%, A-DD: 68.1%, P = 0.039; fellow, T-SD: 58.2%, A-DD: 70.3%, P = 0.008). They were therefore able to use A-DD images to increase their sensitivity to the neuroradiologists' initial level on regular T-SD images. False-positive findings did not differ significantly between sequences. However, readers showed descriptively more false-positive findings on A-DD images. The benefit in sensitivity particularly applied to metastases ≤5 mm (5.7%-17.3% increase in sensitivity).

Conclusions: A-DD images can improve the detectability of brain metastases without a significant loss of precision and could therefore represent a potentially valuable addition to regular single-dose brain imaging.

Purpose: The aim of this study was to determine in a prospective patient study the accuracy of areal bone mineral density (aBMD) measurements with spectral localizer radiographs obtained with a clinical photon-counting detector computed tomography (PCD-CT) scanner in comparison with dual-energy x-ray absorptiometry (DXA).

Methods: In this institutional review board-approved, prospective study, 41 patients (15 females, 26 males; mean age 61.3 years, age range 35-78 years) underwent PCD-CT of the abdomen with a spectral localizer radiograph (tube voltage 140 kVp, tube current 30 mA) and DXA within a median of 45 days. aBMD values were derived for lumbar vertebrae L1-L4 from both methods and were compared with linear regression, Pearson correlation, intraclass correlation coefficients (ICCs), and Bland-Altman plots. T-scores were calculated on a patient level and were compared between methods.

Results: DXA and spectral localizer radiographs showed strong correlation in aBMD measurements ( R = 0.97, P < 0.001) and patient level T-scores ( R = 0.99, P < 0.001). There was a strong agreement between aBMD from both methods (ICC, 0.96; 95% CI, 0.94-0.97). Bland-Altman analysis revealed a very small mean difference in aBMD between methods (mean absolute error 0.019 g/cm 2 ) with narrow limits of agreement (-0.083 g/cm 2 to 0.121 g/cm 2 ). Similarly, there were small differences in regard to the T-score (mean absolute error 0.156) with narrow limits of agreement (-0.422 to 0.734) between methods. ICCs indicated an excellent agreement between T-scores from DXA and spectral localizer radiographs (ICC, 0.98; 95% confidence interval, 0.95-0.99).

Conclusions: Our prospective patient study indicates that spectral localizer radiographs obtained with a clinical PCD-CT system enable accurate quantification of the lumbar bone areal mineral density. This opens up the opportunity for opportunistic screening of osteoporosis in patients who undergo CT for other indications.

Objectives: Anti-amyloid-beta immunotherapy requires frequent MRI screening for amyloid-related imaging abnormalities-hemorrhage subtype (ARIA-H), consisting of cerebral microbleeds (CMB) and/or superficial siderosis (SS), using gradient-recalled echo (GRE) or susceptibility-weighted imaging (SWI). Screening MRI sequences for ARIA-H may benefit from acceleration to maximize patient enrollment by increased throughput and reduced motion degradation. This study assessed the diagnostic performance of standard GRE and SWI to echo-planar imaging (EPI) accelerated substitutions for detecting CMB and SS.

Materials and methods: This retrospective single-center rater study included 50 patients, 25 with CMB and 25 patients without CMB (median age 77 y, IQR: 70 to 82 y; 30 of 50 female) who were imaged with FDG PET-3T MRI from April to July 2023. Standard GRE (90 s) and SWI (192 s) were compared with an EPI-accelerated GRE (aGRE; 13 s, 86% time reduction) and an EPI-accelerated SWI substitution (aSWI; 33 s, 83% time reduction). Three board-certified neuroradiologists independently reported CMB and SS (per ARIA-H monitoring guidelines), perceived image quality and motion for each sequence. There were 240 total assessments per rater (the 4 different sequences for the 50 patients plus 10 duplicated patients). Sensitivity, specificity, positive and negative predictive values, area under the curve (AUC), inter-rater and intrarater agreement were determined for each sequence and rater.

Results: The aggregate AUCs for the 4 individual sequences were excellent for detecting CMB (0.84 to 0.94) and SS (0.89 to 1.00) without statistical differences observed between standard and EPI-accelerated substitutions. Both aGRE and aSWI had high negative predictive values (96.5% to 100%). There were modest quantitative correlations between standard and accelerated sequences (0.606 and 0.391 for GRE and SWI, respectively), no differences in CMB count for aGRE (bias 0.01, P=0.895), but reduced CMB count with aSWI (bias -1.12, P=0.014). Inter-rater agreements were mildly reduced for both GRE versus aGRE (eg, 0.757 to 0.622 for CMB detection) and SWI versus aSWI (eg, 0.834 to 0.649 for SS detection). Perceived image quality for accelerated sequences was reduced, but with less motion observed with aSWI.

Conclusions: The aGRE and aSWI sequences shorten scan times 86% and 83%, respectively, with similar diagnostic performance for ARIA-H screening, but reduced rater agreement and perceived image quality.

Objectives: This study aimed to compare biventricular cine measurements and quantitative maps of myocardial T1 and T2 relaxation times at field strengths ranging from 0.55T to 1.5T in patients with a clinical indication for cardiac magnetic resonance imaging (CMR). Establishing the feasibility of low-field CMR may improve accessibility due to easier siting and lower cost of the low-field systems.

Materials and methods: Thirteen patients underwent same-day comparative CMR at 0.55T and on a commercial scanner at 1.5T. We examined all individuals with breath-held segmented bSSFP cine sequences for volumetric assessment of the left ventricle (LV), right ventricle (RV), and visual assessment of wall motion abnormalities (WMA) and valve pathologies. The quantitative T1 and T2 maps were acquired in 3 short-axis views for tissue characterization. Blinded readers scored the image quality on a 3-point Likert scale. Ten healthy volunteers were additionally examined at 0.55T to obtain reference values for the parametric maps.

Results: Functional analysis of both ventricles at low-field CMR has a reasonable correlation (r=0.94 to 0.99) with conventional 1.5T measurements. LV ejection fraction (EF) (P=0.62) and RV measurements (all P>0.05) were highly reproducible, but LV absolute volumetric measurements were slightly lower at the low-field strength (all P<0.05). T1 and T2 relaxation times correlated strongly between field strengths (r=0.79; P<0.01 and r=0.63; P=0.02). Reference values from the volunteers were 678.6±13.5 ms (T1) and 66.5±4.1 ms (T2). Overall, good image quality was achieved, and visual assessment showed excellent agreement with 1.5T. Trigger artifacts occurred more frequently during 0.55T scans compared with 1.5T. Correct clinical stratification of volumetric parameters, WMA, valve pathologies, and parametric maps was possible in 94% of all cases.

Conclusions: CMR at 0.55T provides a comprehensive assessment of function, structure, and tissue characterization comparable to that of 1.5T. The diagnostic accuracy in this clinical cohort is high. Identification of the specific trigger problems and optimization of the trigger technique could help to overcome the slight inaccuracies in the LV absolute volumetric measurements. Low-field CMR holds promise for expanding access to this valuable diagnostic tool, benefiting patients worldwide and on an individual level.

Objectives: Quantitative chemical exchange saturation transfer (CEST) breast imaging is limited by pronounced fat-induced artifacts. The strongest fat artifact, appearing between [-2, -4] ppm in the Z-spectrum, directly overlaps the signal of the exchange-relayed nuclear Overhauser effect (rNOE) at around -3.5 ppm, a key biomarker for protein content and cellularity, making accurate rNOE-CEST evaluation extremely challenging. The aim of this study is to evaluate rNOE-CEST contrast corrected for fat-related artifacts using a novel, fully software-based fat correction method in breast cancer patients.

Materials and methods: FATLESS (Fat Attenuation Technique using Lipid signal Estimation and Simulated Saturations in postprocessing) was developed for correcting fat-related artifacts across the entire Z-spectrum in CEST MRI. The FATLESS method estimates fat signals from residual signals at the direct water saturation offset (0 ppm) while accounting for partial saturation of fat resonances. FATLESS was retrospectively applied to 7T CEST data from breast cancer patients (acquired September 2018 to May 2019). Resulting fat-corrected rNOE, amide, and guanidino MTRRex contrast values were quantified from 2D snapshot GRE CEST with low saturation power (B1=0.6, 0.9 μT). Kruskal-Wallis tests and Pearson correlation analyses were used to compare MTRRex values between tumor and normal-appearing fibroglandular tissue and assess correlations with Ki-67, a tumor proliferation marker.

Results: Nine biopsy-confirmed breast cancer patients [mean age, 50 y ± 10 (SD)] and 7 healthy controls [mean age, 25 y ± 4 (SD)] were included. Fat-corrected MTRRex rNOE maps were validated in phantom and in vivo data, confirming independence from fat artifacts using the FATLESS method. Tumor regions showed significantly higher fat-corrected MTRRex rNOE values than healthy tissue (+140% mean increase, P<0.001). A strong positive correlation was found between fat-corrected MTRRex rNOE values and Ki-67 (R² = 0.71).

Conclusions: The developed FATLESS fat correction method enables full utilization of all CEST MRI contrasts in the human breast. The observed significant rNOE contrast elevation and strong correlation with tumor proliferation highlight its potential as a non-invasive imaging biomarker for breast cancer characterization.

Rationale and objectives: Dual-source photon-counting CT (DS-PCCT) facilitates an unprecedented combination of spectral information and ultra-high resolution in whole-body imaging of multiple myeloma. This study explored the distinct characteristics of soft tissue, fat, and calcium in virtual monoenergetic images (VMI) with low photon energy, aiming to identify criteria of lesion vitality.

Materials and methods: This retrospective study included 51 patients with multiple myeloma (67.1±10.1 y, 36 men) who underwent unenhanced whole-body DS-PCCT between October 2024 and February 2025. Three board-certified radiologists measured CT numbers within 169 osteolytic lesions (85 active) and their surrounding tissues. Differences between 40 and 70 keV were compared among active and inactive lesions. In addition, the presence of intralesional fat, calcifications, hypodense rims, homogeneity, and highlighting in color-coded virtual non-calcium maps was assessed subjectively.

Results: The attenuation difference between 40 and 70 keV VMI was markedly larger in active than inactive lesions [median 19.3 (interquartile range: 12.7-27.0) vs. -3.8 (-26.1 to 17.0) HU; P <0.001]. Homogenous density (86.3% vs. 2.4%) and conspicuous color-coding (94.9 vs. 68.7%) were more common in active myeloma, whereas intralesional fat (10.6 vs. 72.2%), calcifications (1.6% vs. 40.1%), and hypodense rims (0 vs. 37.3%) were more frequent in inactive lesions (all P <0.001). Interrater measurement reliability was excellent (intraclass correlation coefficient ≥0.95), and agreement for all qualitative criteria was high (Krippendorff α ≥0.85).

Conclusions: This investigation on whole-body DS-PCCT demonstrated a significant difference in attenuation changes from 70 to 40 keV VMI across multiple myeloma patients with a therapy response versus initial diagnosis and disease progression. Qualitative characteristics of medullary lesions, such as heterogeneity, partial recalcification, or a hypodense rim ("halo sign"), can serve as additional indicators of therapy response.

Objectives: Synthetic magnetic resonance imaging (MRI) is a quantitative imaging technique that has shown promise in brain imaging but has not yet been evaluated for assessing the optic nerves. Our study aimed to investigate its diagnostic performance in this context.

Materials and methods: We retrospectively evaluated synthetic MRI's performance in detecting optic nerve hypersignals in 65 patients who underwent synthetic MRI covering the optic nerves from March 2023 to February 2025 in a single tertiary center. Diagnostic performance for optic nerve hypersignals was assessed using conventional T2 and/or FLAIR-weighted images with fat saturation as the reference standard. Quantitative T2 and proton density (PD) values were compared between optic nerves exhibiting hypersignals on synthetic MRI and those without any hypersignals. The detection rate of optic nerve hypersignals in patients with a diagnosis of acute optic neuritis was evaluated using synthetic MRI, both overall and for each individual synthetic contrast. For the qualitative analysis, sensitivity, specificity, and accuracy were each calculated with a 95% CI using the exact binomial (Clopper-Pearson) method. Quantitative differences in T2 and PD values were assessed using the Cohen d to evaluate effect size, and statistical significance was determined by the Wilcoxon rank-sum test.

Results: Synthetic MRI showed good overall diagnostic performance for optic nerve hypersignals, with sensitivity, specificity, and accuracy of 71.4% [0.513-0.868], 97.1% [0.916-0.994], and 91.5% [0.854-0.957], respectively. Quantitative analysis revealed significantly higher median T2 (66.29 vs. 72.4 ms) and proton density (72.22 vs. 86.51) values in optic nerves exhibiting hypersignals compared with those without (P<0.001 for both). For acute optic neuritis specifically, 6 out of 7 (85.7%) were correctly identified in synthetic MRI. Confidence scores did not significantly differ between patients with optic nerve hypersignals and those without.

Conclusions: Synthetic MRI showed promising results in detecting abnormal signals in the optic nerves, suggesting its potential role in their clinical evaluation.

Objective: To comprehensively analyze worldwide safety data of gadoxetate disodium after 20 years of use and to review its reclassification from group III to group II on the American College of Radiology (ACR) nephrogenic systemic fibrosis (NSF)-risk classification scheme.

Materials and methods: Two safety data sets were analyzed: 23 clinical phase I to IV studies and Bayer pharmacovigilance database (PV) from 2004 to 2024. In addition, a literature review on NSF reports with special focus on patients with different degrees of renal impairment was performed. Patients' exposure was based on the assumption that one vial or prefilled syringe was given to each patient for each procedure, with an estimated total of over 12 million administrations. The primary target variable was the number, frequency and characteristics of unrelated/related adverse events (AEs) in clinical studies and adverse drug reactions (ADRs) reported to PV. Incidence and reporting rates were analyzed by descriptive statistical methods.

Results: A total of 10,282 patients were included in clinical phase I to IV studies. Drug-related AEs were reported in 6% and 1.7% in phase III and IV studies, respectively. Nine (0.11%) related serious adverse events (SAEs) were recorded in phase IV, none in phase III. The most frequently recorded AEs (related or unrelated to drug) in phases I to III were nausea (1.4%) and headache (1.2%). All other AEs were reported ≤ 1.0%. In phase IV, dyspnea (0.34%) and nausea (0.28%) (related or unrelated) were most frequently reported. More than 12 million doses of gadoxetate were administered according to sales data. Most frequently reported ADRs from the PV were hypersensitivity reactions (reporting rate 0.0147%), nausea (0.0029%) and pain (0.0019%). Exposure increased steadily from 16,578 administrations in 2006 to 1,289,979 per year by December 31, 2024. Conversely, the ADR rate decreased from 0.21% in 2006 to ≤0.05% in 2011 through 2024. No report diagnostic of or consistent with NSF was documented, even in patients with renal impairment.

Conclusion: Liver-specific gadoxetate disodium demonstrated a favorable safety profile in patients independent of their renal function. No report diagnostic of or consistent with NSF has been reported with over 20 years of use. The well-established benefit/risk profile of gadoxetate disodium prompted the ACR to reclassify it from group III to group II as of April 2024.