1. Phantom design

A custom-designed phantom was created to simulate an implant in the human body. A titanium pin(15 mm × 135 mm × 5 mm), commonly used in surgeries, was fixed centrally between two plastic blocks and stabilized in a plastic container(125 mm × 185 mm × 50 mm) filled with lard oil to mimic human body fat(Fig 1).

2. Equipment & Protocol

The study used a MAGNETOM Vida 3.0T(Siemens Healthineers) with a 64-channel head/neck coil and included T1-weighted imaging(WI), T2WI, and fat-suppressed T2WI Short Tau Inversion Recovery(STIR) sequences acquired with Turbo Spin Echo(TSE), TSE+VAT, and TSE+VAT+DRB&DRS. GRAPPA factors of 2, 3, and 4 were applied with three acquisitions per sequence. From 31 slices per scan, the first 10 slices with minimal air bubbles were selected for evaluation. Imaging parameters are detailed in Table 1.

3. Evaluation of scan Time

The scan time was measured for varying GRAPPA factors (2, 3, and 4). At each GRAPPA factor, the scan times for TSE, TSE+VAT, and TSE+VAT+DRB&DRS sequences were identical.

4. Quantitative evaluation

 4.1 Distance from phantom bottom to susceptibility artifact

The distance was measured in TSE and TSE+VAT images using Philips IntelliSpace Portal(ISP) along the vertical frequency encoding direction, excluding the top section of the phantom due to air-induced distortion. The distance from the phantom bottom to the distortion point was used to assess artifact size, with greater distances indicating reduced artifacts and improved visibility(Fig 2). Statistical analysis was conducted using an independent samples t-test in SPSS(version 20), with p < 0.05 considered significant.

 4.2 Susceptibility artifacts distortion

The susceptibility artifacts distortion was evaluated using TSE, TSE+VAT, and TSE+VAT+DRB&DRS sequences. Using TeraRecon's Aquarius iNtuition workstation, bright regions in the phantom images with prominent artifacts were analyzed. Measurements were conducted on the left and right sides in the phase direction, where distortion changes were minimal in the bright regions of the signal. Additionally, under the assumption that the signal intensity causing distortion is symmetric on both sides, only the left side was measured. The distortion was measured by placing a cursor over selected regions and using the yellow width in the graphical signal representation as the standard (Fig 3, red box). Statistical analysis was performed with one-way ANOVA in SPSS (version 20) and post-hoc scheffe's method, considering p-values < 0.05 as significant.

 4.3 SNR

Images acquired with TSE+VAT and TSE+VAT+DRB&DRS were analyzed. SNR was calculated(Fig 4) based on average value at 30 mm from the left and right edges and 3 mm from the top of the phantom, with SD measured at 10 mm from the bottom(Fig 5). Statistical analysis was performed using an independent samples t-test in SPSS(version 20), with p < 0.05 considered significant.

5. Qualitative evaluation

Image quality was evaluated on images acquired with TSE, TSE+VAT, and TSE+VAT+DRB&DRS. Regions around susceptibility artifacts were assessed using a 5-point Likert scale(1: poor, 2: fair, 3: moderate, 4: good, and 5: excellent). Five MRI technologists with over 5 years of experience performed blinded evaluations, and average scores were calculated.