Investigative Radiology最新文献

Abstract: Congenital lymphatic flow disorders collectively refer to a heterogeneous group of diseases that manifest as chylothorax, chylous ascites, intestinal lymphangiectasia, protein-losing enteropathy, and peripheral extremity or genital lymphedema, all in the absence of identifiable injury to the lymphatic system. We have only recently begun to understand congenital lymphatic flow disorders through the ability to image lymph flow dynamically. Intranodal dynamic contrast-enhanced magnetic resonance lymphangiography (DCMRL) is a crucial technique for imaging lymphatic flow in pediatric patients with congenital lymphatic flow disorders. However, as lymphatic imaging is still a nascent discipline with many uncertainties regarding optimal imaging and treatment, effective patient management requires a comprehensive understanding of imaging techniques, disease pathophysiology, and multidisciplinary treatment approaches. Above all, a fundamental understanding of the physiological lymphatic flow of the central conducting lymphatics is essential for the correct interpretation of DCMRL images. This knowledge helps to avoid unnecessary examinations, erroneous diagnoses, and potentially harmful treatment approaches. This review provides an overview of the methods, advantages, and precautions for interpreting the DCMRL examination, a state-of-the-art lymphatic system imaging technique, and shares various case studies.

Objectives: Detecting premalignant lesions for pancreatic ductal adenocarcinoma, mainly pancreatic intraepithelial neoplasia (PanIN), is critical for early diagnosis and for understanding PanIN biology. Based on PanIN's histology, we hypothesized that diffusion tensor imaging (DTI) and T2* could detect PanIN.

Materials and methods: DTI was explored for the detection and characterization of PanIN in genetically engineered mice (KC, KPC). Following in vivo DTI, ex vivo ultrahigh-field (16.4 T) MR microscopy using DTI, T2* was performed with histological validation. Sources of MR contrasts and histological features were investigated, including histological scoring for disease burden (lesion span) and severity (adjusted score). To test if findings in mice can be translated to humans, human pancreas specimens were imaged.

Results: DTI detected PanIN and pancreatic ductal adenocarcinoma in vivo (6 KPC, 4 KC, 6 controls) with high discriminative ability: fractional anisotropy (FA) and radial diffusivity with area under the curve = 0.983 (95% confidence interval: 0.932-1.000); mean diffusivity and axial diffusivity (AD) with area under the curve = 1 (95% confidence interval: 1.000-1.000). MR microscopy with histological correlation (20 KC/KPC; 5 controls) revealed that sources of MR contrasts likely arise from microarchitectural signatures: high FA, AD in fibrotic areas surrounding lesions, high diffusivities within cysts, and high T2* within lesions' stroma. The strongest histological correlations for lesion span and adjusted score were obtained with AD (R = 0.708, P < 0.001; R = 0.789, P < 0.001, respectively). Ex vivo observations in 5 human pancreases matched our findings in mice, revealing substantial contrast between PanIN and normal pancreas.

Conclusions: DTI and T2* are useful for detecting and characterizing PanIN in genetically engineered mice and in the human pancreas, especially with AD and FA. These are encouraging findings for future clinical applications of pancreatic imaging.

Purpose: This study documents the gadolinium (Gd) content in urine over time after the administration of a single dose of Gd-based contrast agent (GBCA) in patients diagnosed with Gd deposition disease.

Materials and methods: In this retrospective observational study, 45 subjects with normal renal function who had performed 1 contrast-enhanced magnetic resonance imaging and had a nonprovoked (native) 24-hour urine test for Gd quantification after the examination were evaluated. The GBCA brand and the time interval in days between the GBCA administration and 24-hour urine Gd measurements were recorded. Log-log plot visualization of time points for urine Gd content was obtained.

Results: Time points collected for urine Gd content showed that Gd was above the reference levels for 3 months postinjection. The urinary concentration of Gd was similar for all agents, including linear and macrocyclic. The urinary content decreased in a dog-leg fashion. Gd urine content was substantially elevated at 1 month and decreased to remain above the accepted normal range by 3 months.

Conclusions: Gd is retained in the body and shows demonstrable continued spontaneous elimination in urine for at least several months after administration, including the most stable macrocyclic agents. The Gd elimination pattern shows a logarithmic decrease pattern between 1 and 3 months for all agents, regardless of their structure.

Objectives: Concern about contrast-induced acute kidney injury (CI-AKI) may delay the timely administration of contrast media for computed tomography (CT). The precise causative effect of iodinated contrast media on CI-AKI and its relevant risk factors remains an area of ongoing investigation. Therefore, this study aimed to determine the risk of CI-AKI following contrast-enhanced CT and its predisposing risk factors.

Materials and methods: This study employed a 1:1 propensity score matching analysis using electronic medical records gathered between January 2006 and December 2022 from 16 institutions in South Korea. Contrast-enhanced and nonenhanced CT scans in patients aged 18 years and above were matched for baseline estimated glomerular filtration rate (eGFR), demographic characteristics, and clinical variables to assess the risk of CI-AKI. Subgroup analyses were conducted to evaluate any significant risk factors for CI-AKI.

Results: A total of 182,170 CT scans with contrast were matched to 182,170 CT scans without contrast. The risk of CI-AKI in the entire study cohort was not statistically significant (odds ratio [OR], 1.036; 95% confidence interval [CI], 0.968-1.109; P = 0.34). Subgroup analyses revealed a significantly higher risk of CI-AKI in patients with eGFR <30 mL/min/1.73m 2 (OR, 1.176; 95% CI, 1.080-1.281; P = 0.011) or eGFR 30-45 mL/min/1.73m 2 (OR, 1.139; 95% CI, 1.043-1.244; P = 0.019), patients diagnosed with chronic kidney disease (OR, 1.215; 95% CI, 1.084-1.361; P = 0.011), and those administered with iso-osmolar contrast media (OR, 1.392; 95% CI, 1.196-1.622; P = 0.011).

Conclusions: The risk of CI-AKI following CT was minimal in the general population. However, caution is warranted for patients with chronic kidney disease and eGFR lower than 45 mL/min/1.73m 2 , or those administered with iso-osmolar contrast media.

Objectives: The aim of this study was to evaluate the impact of a prototype grid with a 29:1 ratio (r29) and a 15:1 (r15) grid on the image quality (IQ) and radiation dose in abdominal angiography.

Materials and methods: Six typical abdominal angiographic image scenarios were created in 4 pigs. Polymethylmethacrylate and aluminum plates were used to add 10 cm of patient equivalent thickness to simulate different body types. Fluoroscopic images were acquired with a source-to-image receptor distance of 120 cm. Tantalum- and iron-specific acquisition protocols at different IQ levels were acquired. IQ of radiation dose equivalent image pairs, created with the r29 and r15 grids, respectively, was quantitatively evaluated using contrast-to-noise ratio (CNR) measurements. Differences in radiation dose were estimated using the dose-weighted CNR. Two blinded readers compared IQ of these images using a Likert scale. In a second step, the readers selected pairs of the r29 and r15 images with subjectively equivalent IQ. Radiation doses were then compared.

Results: Compared with the r15 grid, the r29 grid images achieved similar CNR at an average of 26% (±12%) lower radiation dose at a mean patient equivalent thickness of 26 cm and 36 cm. Both readers noted a significant increase in IQ (P < 0.001) for dose equivalent images, whereas the interobserver agreement was 0.59. For the selected IQ equivalent images, a radiation dose reduction of 38% (±17%; P < 0.001, interobserver agreement 0.92) was noted when using the r29 grid.

Conclusions: The use of an r29 grid at a large source-to-image receptor distance can significantly improve the IQ compared with the r15 grid at the same radiation dose in abdominal angiography or can reduce radiation dose while preserving IQ.

Objectives: Diffusion-weighted imaging (DWI) is pivotal for prostate magnetic resonance imaging. This is rooted in the generally reduced apparent diffusion coefficient (ADC) observed in prostate cancer in comparison to healthy prostate tissue. This difference originates from microstructural tissue composition changes, including a potentially decreased fluid-containing lumen volume. This study explored the nature of the observed ADC contrast in prostate tissue through inversion recovery-prepared DWI examinations that generated varying levels of fluid suppression.

Materials and methods: This institutional review board-approved, single-center, prospective study was conducted from 2023 to 2024; all participants underwent magnetic resonance imaging including DWI with b-values of 50 and 800 s/mm2 at 16 inversion times (TI; 60-4000 milliseconds). The measured ADC was interpreted with a 2-compartment model (compartments: tissue and fluid). Descriptive statistics were computed for all analyzed parameters.

Results: Twelve healthy male volunteers (45 ± 17 years) and 1 patient with prostate adenocarcinoma (66 years) were evaluated. The ADC map appearance depended heavily on the TI, and we observed a feature-rich ADC(TI) curve. The ADC in the transition zone (TZ) of healthy volunteers increased between TI = 60 milliseconds and approximately 1100 milliseconds, then dropped drastically before increasing again, stabilizing at a very high TI. This effect was greatly reduced in the patient's prostate cancer lesion. The 2-compartment model described this behavior well. After the inversion, tissue magnetization recovers faster, decreasing its signal contribution in absolute terms and resulting in an increase in the ADC. At the tipping point, the total magnetization is zero at b = 0, when the positive tissue magnetization and still-inverted fluid magnetization cancel out. A small diffusion encoding leads to a positive signal, thus generating an infinite ADC. After the tipping point, the fluid magnetization remains negative and thereby reduces the ADC.

Conclusions: Prostate fluid appears to contribute significantly to prostate ADCs. Its contribution could be adjusted by choosing an appropriate inversion recovery preparation, potentially enhancing contrast for prostate cancer lesions.

Objectives: Contrast-enhanced mammography (CEM) is an accurate competitor for contrast-enhanced breast magnetic resonance imaging (CE-MRI), but the examination is limited by the lack of 3D information. Digital breast tomosynthesis (DBT) allows better lesion detection and characterization compared with mammography. The availability of quasi-3D contrast imaging could further improve the performance of CEM. The aim of our analysis was to compare the diagnostic performance of a contrast-enhanced digital breast tomosynthesis prototype (CE-DBTp) to CEM and to CE-MRI.

Materials and methods: This prospective study was approved by the ethics committee, and all patients gave written informed consent. Women who presented with suspicious findings on mammography, DBT, or ultrasound were invited to participate in the study. Participants underwent CEM and CE-DBTp of the breast with the suspicious findings as well as bilateral CE-MRI. Histology was used as the standard of reference. Four readers (R1 and R2 non-experienced; R3 and R4 experienced) evaluated the images, blinded to patients' history, previous imaging, and histology. The readers evaluated CEM, CE-DBTp, and CE-MRI in separate sessions and gave a BI-RADS score for each finding. Sensitivity, specificity, lesion conspicuity, and readers' confidence were calculated and compared.

Results: We included 84 patients (mean age, 56 years; range, 39-70) with 91 histologically verified breast lesions (27 benign, 64 malignant). The accuracy of the CE-DBTp was high, but significant differences were seen between experienced (both 86.8%) and non-experienced readers (76.9% and 78%, P = 0.021). No differences were found between CEM and CE-DBTp, whereas the accuracy of CE-MRI was higher (P = 0.002). Sensitivity with CE-DBTp varied (89.1% to 100%) between experienced and non-experienced readers (P = 0.074), and it was comparable to CEM but lower than CE-MRI (P = 0.003). Specificity was variable between readers with all modalities. Lesion conspicuity was higher for the CE-DBTp and CE-MRI than for CEM, and confidence was significantly higher with the CE-DBTp than with CEM for one of the readers (P < 0.001).

Conclusions: A high sensitivity and good accuracy were achieved with the CE-DBTp. Lesion conspicuity and readers' confidence were higher with the CE-DBTp compared with CEM. However, CE-MRI had the highest sensitivity and accuracy.

Objectives: The T1-weighted GRE (gradient recalled echo) sequence with the Dixon technique for water/fat separation is an essential component of abdominal MRI (magnetic resonance imaging), useful in detecting tumors and characterizing hemorrhage/fat content. Unfortunately, the current implementation of this sequence suffers from several problems: (1) low resolution to maintain high pixel bandwidth and minimize chemical shift; (2) image blurring due to respiratory motion; (3) water/fat swapping due to the natural ambiguity between fat and water peaks; and (4) off-resonance fat blurring due to the multipeak nature of the fat spectrum. The goal of this study was to evaluate the image quality of water/fat separation using a high-resolution 3-point Dixon golden angle radial acquisition with retrospective motion compensation and multipeak fat modeling in children undergoing abdominal MRI.

Materials and methods: Twenty-two pediatric patients (4.2 ± 2.3 years) underwent abdominal MRI on a 3 T scanner with routine abdominal protocol and with a 3-point Dixon radial-VIBE (volumetric interpolated breath-hold examination) sequence. Field maps were calculated using 3D graph-cut optimization followed by fat and water calculation from k-space data by iteratively solving an optimization problem. A 6-peak fat model was used to model chemical shifts in k-space. Residual respiratory motion was corrected through soft-gating by weighting each projection based on the estimated respiratory motion from the center of the k-space. Reconstructed images were reviewed by 3 pediatric radiologists on a PACS (picture archiving and communication systems) workstation. Subjective image quality and water/fat swapping artifact were scored by each pediatric radiologist using a 5-point Likert scale. The VoL (variance of Laplacian) of the reconstructed images was used to objectively quantify image sharpness.

Results: Based on the overall Likert scores, the images generated using the described method were significantly superior to those reconstructed by the conventional 2-point Dixon technique ( P < 0.05). Water/fat swapping artifact was observed in 14 of 22 patients using 2-point Dixon, and this artifact was not present when using the proposed method. Image sharpness was significantly improved using the proposed framework.

Conclusions: In smaller patients, a high-quality water/fat separation with sharp visualization of fine details is critical for diagnostic accuracy. High-resolution golden angle radial-VIBE 3-point Dixon acquisition with 6-peak fat model and soft-gated motion correction offers improved image quality at the expense of an additional ~1-minute acquisition time. Thus, this technique offers the potential to replace the conventional 2-point Dixon technique.

Objectives: The aim of this study was to compare deep learning reconstructed (DLR) 0.55 T magnetic resonance imaging (MRI) quality, identification, and grading of structural anomalies and reader confidence levels with conventional 3 T knee MRI in patients with knee pain following trauma.

Materials and methods: This prospective study of 26 symptomatic patients (5 women) includes 52 paired DLR 0.55 T and conventional 3 T MRI examinations obtained in 1 setting. A novel, commercially available DLR algorithm was employed for 0.55 T image reconstruction. Four board-certified radiologists reviewed all images independently and graded image quality, noted structural anomalies and their respective reporting confidence levels for the presence or absence, as well as grading of bone, cartilage, meniscus, ligament, and tendon lesions. Image quality and reader confidence levels were compared ( P < 0.05, significant), and MRI findings were correlated between 0.55 T and 3 T MRI using Cohen kappa (κ).

Results: In reader's consensus, good image quality was found for DLR 0.55 T MRI and 3 T MRI (3.8 vs 4.1/5 points, P = 0.06). There was near-perfect agreement between 0.55 T DLR and 3 T MRI regarding the identification of structural anomalies for all readers (each κ ≥ 0.80). Substantial to near-perfection agreement between 0.55 T and 3 T MRI was reported for grading of cartilage (κ = 0.65-0.86) and meniscus lesions (κ = 0.71-1.0). High confidence levels were found for all readers for DLR 0.55 T and 3 T MRI, with 3 readers showing higher confidence levels for reporting cartilage lesions on 3 T MRI.

Conclusions: In conclusion, new-generation 0.55 T DLR MRI provides good image quality, comparable to conventional 3 T MRI, and allows for reliable identification of internal derangement of the knee with high reader confidence.