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Rapid Fire Abstracts

Rapid Fire 05- Rapid, Efficient Imaging I

How low can we go? The effect of acquisition duration on cardiac volume and function measurements in free-running cardiac and respiratory motion-resolved 5D whole-heart cine MRI at 1.5 T (RF_FR_320)

Friday, January 31, 2025
9:20 AM – 9:30 AM East Coast USA Time
Location: Blue Room PreFunction
Background:


Conventional 2D breath-hold cine cardiac magnetic resonance (CMR) is a well-established technique for assessing cardiac volumes and function. This technique, however, requires an ECG signal, repetitive breath-holding, and the cardiac view planning is time-consuming and proficiency-demanding. Recently, a free-running framework was developed for cardiac and respiratory motion-resolved 5D (x-y-z-cardiac-respiratory) whole-heart imaging.[1] This fully self-gated free-breathing approach extracts both cardiac and respiratory signals from the image data, and thereby no longer requires an ECG signal or repetitive breath-holds (Fig. 1). Due to its high isotropic spatial resolution, this framework allows for reconstruction of cine images in any desired cardiac view. To translate and exploit the efficiency and simplicity of this free-running framework as an automated push-button solution, the goal of this work was to investigate the impact of acquisition time on cardiac volumetric and functional measurements when using free-running imaging, compared to reference standard breath-held 2D cine imaging.
 







Methods:


Sixteen healthy adult volunteers underwent CMR at 1.5 T (Sola, Siemens), including standard 2D breath-held cine imaging (1.4 x 1.4 x 8.0 mm3) and custom free-running imaging (1.4 mm isotropic) with six uninterrupted acquisitions ranging from 1 to 6 min in randomized order. Using the geometries of the 2D cine images, each free-running dataset was reformatted into 2D cine images with the exact same short-axis and long-axis views. All datasets were anonymized, randomised, and analysed by an expert reader for the left-ventricular end-diastolic and end-systolic volumes (EDV & ESV) and ejection function (EF). In addition, both image quality and observer confidence in segmentation were rated using a 4-point Likert scale. Finally, acquisition efficiency was reported for both imaging techniques, which was defined as the time required for data sampling divided by the total scan time.
 








Results:


In all 16 subjects, 2D breath-hold cine images and free-running data with six different scan durations were successfully acquired (Fig. 2). No significant differences in both EDV and ESV were found between 2D breath-hold cine and free-running imaging, except for the EDV derived from 4 minutes of free-running imaging (p=0.026). Biases in EDV ranged from -2.4 to -7.4 mL, while biases in ESV ranged from -3.8 to 2.1 mL (Table 1). No significant differences in EF were found between 2D breath-hold cine and free-running imaging using any acquisition duration. Biases in ejection fraction ranged from -2.8% to 0.94%. Although both image quality and observer confidence improved with increasing acquisition duration for free-running imaging, 2D breath-hold cine imaging scored significantly higher than any free-running acquisition (Fig. 3). The average time required for the entire planning and acquisition of 2D breath-held cine imaging and localizers was 14:29 min, compared to 2 min (1 minute acquisition) to 7 min (6 minute acquisition) for free-running imaging. Acquisition efficiency improved from 13% for standard 2D cine imaging to 50% or higher for free-running imaging.







Conclusion:


Free-running CMR with an acquisition duration as short as 1 minute yields left-ventricular cardiac volumes and ejection fraction comparable to standard 2D breath-held cine imaging with clear benefits in patient comfort, as well as workflow efficiency and flexibility, albeit at the expense of both image quality and observer confidence.