Characterisation of Children's Head Motion for Magnetic Resonance Imaging With and Without General Anaesthesia

Abstract

Head motion is one of the major reasons for artefacts in Magnetic Resonance Imaging (MRI), which is especially challenging for children who are often intimidated by the dimensions of the MR scanner. In order to optimise the MRI acquisition for children in the clinical setting, insights into children's motion patterns are essential. In this work, we analyse motion data from 61 paediatric patients. We compare structural MRI data of children imaged with and without general anaesthesia (GA), all scanned using the same hybrid PET/MR scanner. We analyse several metrics of motion based on the displacement relative to a reference, decompose the transformation matrix into translation and rotation, as well as investigate whether different regions in the brain are affected differently by the children's motion. Head motion for children without GA was significantly higher, with a median of the mean displacements of 2.19 ± 0.93 mm (median ± standard deviation) during 41.7±7.5 min scans; however, even anaesthetised children showed residual head motion (mean displacement of 1.12±0.35 mm). For both patient groups translation along the z-axis (along the scanner bore) was significantly larger in absolute terms (GA / no GA: 0.87±0.29/0.92 ± 0.49 mm) compared to the other directions. Considering directionality, both patient groups were moving in negative z-direction and thus, out of the scanner. The awake children additionally showed significantly more nodding rotation (0.33±0.20°). In future studies as well as in the clinical setting, these predominant types of motion need to be taken into consideration to limit artefacts and reduce re-scans due to poor image quality.

A numerical human brain phantom for dynamic glucose‐enhanced (DGE) MRI: On the influence of head motion at 3T

“…Even though the number of participants was small, the LSP and MSP motion patterns (Figure 2) are likely to represent rigid motion occurring during a DGE experiment with a slow infusion duration of approximately 240 s. We interpret that the slowly varying characteristics originate from the involuntary relaxation of the subject's neck muscles, leading to a translation in Z‐direction and a pitch rotation similar to nodding 53–55 . Ventricular volume variations are caused by cardiac pulsation and loading of D‐glucose 20,25,26 These effects were simulated together in Figures 4 and 5 for cases with and without glucose infusion, leading to signal variations similar to those reported in vivo at 3 T (0.25%–1.5% in tumors) 20,28,29,32 .…”

“…The '+' denotes outliers, defined as values that are more than 1.5 times the interquartile range away from the bottom or top of the box originate from the involuntary relaxation of the subject's neck muscles, leading to a translation in Z-direction and a pitch rotation similar to nodding. [53][54][55] Ventricular volume variations are caused by cardiac pulsation and loading of D-glucose 20,25,26 These effects were simulated together in Figures 4 and 5 for cases with and without glucose infusion, leading to signal variations similar to those reported in vivo at 3 T (0.25%-1.5% in tumors). 20,28,29,32 Note that development of new pulse sequences 56 or use of other sugars such as 3-ortho-methylglucose (3OMG) 57,58 or D-glucosamine (D-GlcN) 59 is expected to increase these effects.…”

A radiofrequency coil for infants and toddlers

“…Even under the influence of anaesthesia, patient motion may persist, with the dominant direction of movement being toward the foot end of the bed 10 ; awake children also demonstrate a significant nodding movement 10 . Tailoring the coil housing to the shape of the participant's head, as well as employing an aforementioned adaptable coil design, can aid in mitigating this motion.…”

“…Even under the influence of anaesthesia, patient motion may persist, with the dominant direction of movement being toward the foot end of the bed 10 ; awake children also demonstrate a significant nodding movement. 10 Tailoring the coil housing to the shape of the participant's head, as well as employing an aforementioned adaptable coil design, can aid in mitigating this motion. These strategies become even more effective when combined with pulse-sequence optimizations that reduce scan times, 11 such as parallel imaging 12,13 and compressed sensing 14,15 : these techniques benefit substantially from the increased SNR afforded by dedicated paediatric coils.…”

Evaluating the performance of markerless prospective motion correction and selective reacquisition in a general clinical protocol for brain MRI

“…Motion during MRI acquisition causes ghosting, ringing or blurring artifacts that may hinder accurate diagnosis. The most prevalent motion patterns for awake children during MRI were found to be translation along the axis pointing into the scanner bore, as well as rotation around the Right-Left axiscorresponding to nodding motion [2]. If motion artifacts are present, sequences are often repeated leading to longer examination time, reduced imaging capacity and higher radiology costs [3].…”