Investigative Radiology最新文献

Objectives: The objective of the study was to investigate the dose-response (signal enhancement) relationship and signal-enhancement kinetics of gadoquatrane in different anatomic regions employing different MRI pulse sequences. Gadoquatrane is a novel high-relaxivity, extracellular macrocyclic gadolinium-based contrast agent with tetrameric structure that has the potential to be used at lower Gd doses than long-established contrast agents.

Materials and methods: In this exploratory, prospective crossover study, 7 healthy pigs underwent contrast-enhanced MRI examinations with gadoquatrane (0.01, 0.03, and 0.06 mmol Gd/kg body weight) and standard doses (0.1 mmol Gd/kg) of 2 comparators, gadobutrol and gadoterate meglumine. MRI was performed on a 1.5T scanner under conditions typically used in clinical routine. Immediately after contrast-agent injection, multiphase liver MRI was done (VIBE sequence). Steady-state head-and-neck MRI followed (spin-echo and FLASH sequences alternating from 2 to 32 min after injection). Image evaluation was based on changes in signal intensity from baseline [relative signal enhancement (RSE)]. Simple linear regression analysis was used to investigate the relationship between RSE and gadoquatrane dose. The regression equations were used to estimate the comparator-equivalent doses of gadoquatrane.

Results: The RSE achieved with gadoquatrane in steady-state head-and-neck MRI and multiphase liver MRI increased with dose in all anatomic structures examined, independent of the contrast-agent distribution phase and the pulse sequence employed. Linear regression analysis showed that generally a linear model fitted the dose-response data well ( r2 ≥ 0.84). However, in spin-echo images of the cavernous sinus and VIBE images of the hepatic vein, the areas with the strongest RSE, a disproportionately low RSE was seen with the highest gadoquatrane dose ( r2 of 0.78 and 0.48, respectively).RSE equivalent to the RSE achieved with gadoterate meglumine and gadobutrol at standard dose was achieved with gadoquatrane at doses between 0.031 to 0.039 mmol Gd/kg and 0.040 to 0.049 mmol Gd/kg, respectively. Largely parallel RSE-versus-time curves suggest similar signal-enhancement kinetics for gadoquatrane and the comparators.

Conclusions: The study suggests that gadoquatrane, which demonstrated signal-enhancement kinetics similar to those of gadobutrol and gadoterate meglumine, might be utilized effectively at a dose below 0.05 mmol Gd/kg body weight, independent of the anatomic structure investigated and the pulse sequence employed. Overall, the study supports and complements the results of the clinical dose-response study of gadoquatrane.

Objectives: Diffusion weighted imaging (DWI) is a key component of multiparametric (mp) prostate MRI. DWI using echo-planar techniques is susceptible to distortion at the recto-prostatic air-tissue interface. This study was to determine whether prone patient positioning reduces adjacent rectal air and DW image distortion when compared with standard-of-care supine positioning.

Materials and methods: This prospective study included consecutive patients undergoing mpMRI for suspected PCa between 2023 and 2024. Prostate segmentation was performed on DW and contrast-enhanced images. DWI distortion was measured quantitatively. Qualitative image quality of DWI and T2-weighted imaging (T2WI) was evaluated using PI-QUAL version 2; a separate 5-point clinically based Likert scale was employed to evaluate the volume of rectal air adjacent to the prostate.

Results: Fifty-two patients were enrolled. In total, 58% of patients expressed a preference for supine imaging versus 20% for prone imaging. Qualitative DWI image quality improved significantly in the prone position [median: 4 (3 to 4)] versus supine [3 (1 to 4)]; P < 0.001. In contrast, prone T2WI quality [1 (1 to 1)] was significantly inferior than supine T2WI [3 (3-4)]; P < 0.001. Quantitative measures of rectal air were significantly lower for prone [1.13 cm 3 (0.34-2.43)] compared with supine imaging [1.96 cm 3 (0.47 to 5.81); P = 0.005]. There was no significant difference in distortion between prone [3.21 mm (2.42 to 3.82) and supine [2.95 mm (2.25 to 4.21)] positioning across all patients ( P = 0.80); however, in patients with >4 cm 3 of supine rectal air (n = 19), distortion was significantly reduced by prone imaging [3.49 mm (2.84 to 4.03)] compared with supine [4.60 mm (3.17 to 5.95)]; P = 0.02. The mean additional scanning time for the necessary prone imaging was 8 minutes 18 seconds.

Conclusions: Prone positioning significantly reduces DWI distortion artefact when rectal air is present, but consistently results in degraded T2WI quality.

Objectives: The objective of this study is to derive a contrast agent-specific theoretical framework to optimize acquisition parameters for contrast-enhanced magnetic resonance imaging (MRI) based on the physiochemical properties of gadolinium-based contrast agents, focusing on fast spoiled gradient recalled echo sequences. The goal is to enhance the lesion-to-background contrast for improved diagnostic sensitivity in clinical applications.

Materials and methods: Signal equations for fast spoiled gradient recalled echo sequences were derived for nonenhancing and enhancing tissues using gadoterate meglumine and gadobutrol, characterized by distinct longitudinal (r 1 ) and transverse (r 2 /r* 2 ) relaxivities. Simulations were conducted at 2 field strengths, 1.5T and 3.0T, and various scenarios were considered, including hypothetical lesions with T 1 ratios ranging from 1.1 to 1.8. The signal behavior was analyzed across a range of initial conditions, including different spin densities and field-strength dependent variations in tissue relaxation times. The optimal flip angle and repetition time combinations were determined to maximize contrast. In vivo validation was performed on 2 patients undergoing contrast-enhanced MRI of the brain, using the proposed acquisition parameters.

Results: The modeling and simulations revealed that the flip angle that maximizes signal intensity for a contrast-enhancing lesion (Ernst angle) differs from the flip angle that maximizes T 1 -dependent contrast between lesion and healthy tissue in unenhanced MRI (Pelc angle) and also differs from the flip angle that maximizes the same in contrast-enhanced MRI. The theoretical simulations indicated possible contrast gains of 24%-28% using optimized parameters. The in vivo acquisitions demonstrated contrast gains of 19%-44% for a diffuse enhancing lesion and 91% for a weakly enhancing focal lesion, when comparing the optimized acquisition parameters to manufacturer's default settings.

Conclusions: Adjusted repetition time and flip angle values, derived using the proposed framework, improved the image contrast between healthy and diseased tissues, enhancing the visualization of abnormalities. This approach can be used to optimize routine clinical MRI protocols and balance scan time with contrast enhancement. This may translate to more precise lesion detection, potentially leading to earlier and more accurate diagnosis or treatment monitoring in clinical practice.

Objectives: The primary objective of this study was to evaluate the visualization capability of orally administered manganese chloride tetrahydrate (ACE-MBCA [Ascelia Pharma-manganese-based contrast agent, also referred to as Orviglance or CMC-001]), a novel liver-specific contrast agent developed by Ascelia Pharma, as a liver-specific MRI contrast agent compared with that of the unenhanced MRI for focal liver lesions in a properly blinded study design. The secondary objective was to compare the performance of ACE-MBCA with gadobenate dimeglumine.

Materials and methods: Three independent readers analyzed MRI examinations from a previously completed randomized crossover clinical trial in a blinded manner in a centralized setting. The study included 20 consecutive adult patients with known or suspected liver metastases, who received both ACE-MBCA and gadobenate dimeglumine. The readers evaluated 6 types of MRI scans (unenhanced, enhanced, and combined MRI for both contrast agents) with lesion visualization [lesion border delineation (LBD) and lesion contrast (LC)] as primary outcome. To maintain the blinded nature of the study, all statistical analyses were performed by an independent statistician who was not involved in the image reading process. Differences in primary outcomes were performed using 1-sided paired t tests at a significance level of 0.025 for both parameters. For secondary outcomes (ACE-MBCA enhanced MRI visualization, lesion detection, size measurements, reader confidence, quantitative parameters, and image quality were compared with that of the other scans), descriptive statistics and 95% confidence intervals were used to evaluate differences between categories in comparative analyses, without formal hypothesis testing for most secondary endpoints.

Results: ACE-MBCA-enhanced MRI demonstrated statistically significant superior scoring over unenhanced MRI for visualizing focal liver lesions, with mean LBD scores improving from 1.8-2.3 to 2.4-2.9 and LC scores ranging from 1.8-2.3 to 2.8-3.3 across all 3 readers ( P  < 0.001). Compared with unenhanced MRI, ACE-MBCA detected significantly more lesions across all readers (mean differences 0.4-0.8 lesions, 95% CI: 0.04-1.52), particularly for small lesions (<1 cm), where detection improved from 2-6 to 3-12 lesions. Liver-to-lesion contrast and contrast-to-noise ratios were also significantly higher after ACE-MBCA enhancement. All visualization parameters of ACE-MBCA were comparable to those of gadobenate dimeglumine, with no significant differences.

Conclusions: Compared with unenhanced MRI, ACE-MBCA MRI resulted in superior visualization and a greater number of detected liver lesions. ACE-MBCA and gadobenate dimeglumine performed similarly in the visualization and detection of colorectal liver metastases.

Aim: The aim of this review was to evaluate the safety profile of gadoterate meglumine from published literature and pharmacovigilance reports of adverse drug reactions (ADRs) encompassing 35 years of clinical use and more than 170 million administered doses.

Materials and methods: A review of published literature up to December 31, 2024 was performed through a search in Embase and PubMed databases. The analysis focused on current safety concerns associated with gadolinium-based contrast agents, the hypersensitivity reactions (HSRs), nephrogenic systemic fibrosis (NSF), gadolinium accumulation, and symptoms associated with gadolinium exposure.

Results: A total of 62 publications reporting safety results for gadoterate meglumine were included. Age ranged from a few weeks to 103 years, including patients with all stages of renal impairment. The incidence of HSRs was reported in 17 studies and ranged from <0.01% to 0.58%. Occurrence of NSF was analyzed in 9 studies; to date, no confirmed unconfounded case of NSF diagnosis has been associated with gadoterate meglumine use. Regarding gadolinium presence in the body, 17 studies did not show any significant signal intensity increase in the deep brain in patients after up to 53 exposures, while 4 showed some signal intensity increase in specific subgroups after repeated exposure, but without any clinical symptoms. Symptoms associated with gadolinium exposure have been described in 8 studies, although no causal relationship with gadolinium deposition was established. Safety data obtained from pharmacovigilance monitoring showed an incidence of adverse reactions in 8 cases per 100,000 patients exposed. The most frequently reported adverse reactions were urticaria, nausea, and vomiting (0.001% each), while the incidence of HSRs was less than 0.00035%. No unconfounded NSF reports were received.

Conclusions: Clinical evidence from the published data and pharmacovigilance monitoring demonstrated that gadoterate meglumine is a safe magnetic resonance imaging contrast agent for all age groups in a variety of approved indications throughout the whole body, including in patients with renal impairment.

Over the past 15 years, significant advancements have been made in understanding the pharmacology and toxicology of gadolinium-based contrast agents (GBCAs), widely used in magnetic resonance imaging (MRI). This review focuses on the fate of gadolinium cation (Gd 3+ ) in bone tissues. The evidence indicates that Gd 3+ can persist in bone for extended periods, with higher retention observed for GBCAs with linear ligand structures as opposed to macrocyclic ones. The prolonged presence of Gd, with a significant proportion in species other than the initial intact injected GBCA form, raises concerns about potential toxicological effects, although no direct clinical consequences on bone physiology have been reported so far. This review discusses the complex interactions between Gd 3+ and bone matrix components, such as hydroxyapatite, collagen, and proteoglycans, which might contribute to the mechanisms of Gd retention. It also explores the potential for Gd to interfere with bone remodelling processes and cellular functions, as suggested by in vitro studies, and in comparison with that known for other rare earth elements (REE).