Are dilution, slow injection and care bolus technique the causal solution to mitigating arterial-phase artifacts on gadoxetic acid–enhanced MRI? A large-cohort study

Objective Arterial-phase artifacts are gadoxetic acid (GA)–enhanced MRI’s major drawback, ranging from 5 to 39%. We evaluate the effect of dilution and slow injection of GA using automated fluoroscopic triggering on liver MRI arterial-phase (AP) acquisition timing, artifact frequency, and lesion visibility. Methods and materials Saline-diluted 1:1 GA was injected at 1 ml/s into 1413 patients for 3 T liver MRI. Initially, one senior abdominal radiologist, i.e., principal investigator (PI), assessed all MR exams and compared them to previous and follow-up images, as well as the radiology report on record, determining the standard of reference for lesion detection and characterization. Then, three other readers independently evaluated the AP images for artifact type (truncation (TA), transient severe motion (TSM) or mixed), artifact severity (on a 5-point scale), acquisition timing (on a 4-point scale) and visibility (on a 5-point scale) of hypervascular lesions ≥ 5 mm, selected by the PI. Artifact score ≥ 4 and artifact score ≤ 3 were considered significant and non-significant artifacts, respectively. Results Of the 1413 exams, diagnostic-quality arterial-phase images included 1100 (77.8%) without artifacts, 220 (15.6%) with minimal, and 77 (5.4%) with moderate artifacts. Only 16 exams (1.1%) had significant artifacts, 13 (0.9%) with severe artifacts (score 4), and three (0.2%) non-diagnostic artifacts (score 5). AP acquisition timing was optimal in 1369 (96.8%) exams. Of the 449 AP hypervascular lesions, 432 (96.2%) were detected. Conclusion Combined dilution and slow injection of GA with MR results in well-timed arterial-phase images in 96.8% and a reduction of exams with significant artifacts to 1.1%. Clinical relevance statement Hypervascular lesions, in particular HCC detection, hinge on arterial-phase hyperenhancement, making well-timed, artifact-free arterial-phase images a prerequisite for accurate diagnosis. Saline dilution 1:1, slow injection (1 ml/s), and automated bolus triggering reduce artifacts and optimize acquisition timing. Key Points • There was substantial agreement among the three readers regarding the presence and type of arterial-phase (AP) artifacts, acquisition timing, and lesion visibility. • Impaired AP hypervascular lesion visibility occurred in 17 (3.8%) cases; in eight lesions due to mistiming and in nine lesions due to significant artifacts. • When AP timing was suboptimal, it was too late in 40 exams (3%) and too early in 4 exams (0.2%) of exams. Supplementary Information The online version contains supplementary material available at 10.1007/s00330-024-10590-1.

an intravenous bolus [a 10 ml fixed-dose in patients ≥ 50 kg or, if < 50 kg, at a dosage of 0.025 mmol/kg body weight (0.1 ml/ kg body weight)] through a 20-to 22gauge antebrachial venous catheter, at an injection rate of 1ml/s followed by a 20-mL saline flush at the same rate.All injections were performed using a commercially available power injector.
During the injection a sagittal MR fluoroscopic-like image of the aorta was acquired using a rapid 2D gradient-echo technique.The technologists placed a region-of interest (ROI) over the aorta at the level of the celiac trunk, but when it was not clearly identified, they placed the ROI at the level of the diaphragm, the scanner identified the contrast bolus arrival.Once the specified signal threshold (e.g., 20% above baseline) was exceeded, the machine automatically triggered the breath hold command and started the acquisition.This automatic fluoroscopic bolus tracking and triggering software, offered by Siemens, is known as CARE Bolus.It allowed the timing of arterial-phase image acquisition to be tailored to each individual.Patient breathing instructions were given using an automated voice recording.The mean time to arterial-phase imaging was 30.3 s (range, 26-38 s).Given an approximate 6-8 seconds delay for providing breath hold instructions, the 3D GRE was commenced an average of 25.2 ± 6 4.1 seconds from the beginning of contrast administration.

Qualitative Image Analysis
An abdominal radiologist with >10 years of experience, the principal investigator, (PI), who did not participate in the analysis, assessed the whole, multi-sequence MRI for all study patients, comparing them to previous and follow-up images, including CTs, if available, as well as the radiology report on record.To avoid mismatch on images that had multiple lesions, the PI selected the images to be presented to each reader.Furthermore, the PI intentionally chose the most difficult-to-see AP lesions.
When available, histologic diagnosis was recorded.Otherwise, radiologic diagnoses were based upon characteristic imaging features, underlying diseases, and interim change.All this data served as the standard of reference for lesion detection and characterization, allowing the PI to determine, if present, the location, number and size of focal liver lesions.This was particularly useful to confirm that a lesion was hypervascular or showing arterial phase hyperenhancement (APHE) when the AP images were nondiagnostic, as all these exams were correlated with previous contrast enhanced CT or MRI other than the index exam to confirm these lesions had APHE.
While APHE is frequently used within the LI-RADS framework to characterize specific features of liver lesions, the term itself isn't exclusive to LI-RADS.Here, we use it in the broader sense, i.e., to describe the observation of hyperenhancement during the arterial phase of contrast imaging in either cirrhotic or non-cirrhotic patients.Therefore, we have applied the term to other lesions, e.g.., FNH, adenoma, hemangioma etc.
There were 830 lesions in non-cirrhotic patients and 191 lesions in cirrhotic patients.