Effect of Vibration Caused by Time-varying Magnetic Fields on Diffusion-weighted MRI

Abstract

Diffusion-weighted images (DWIs) with high b-factor in the body are often used to detect and diagnose cancer at MRI. The echo planar imaging (EPI) sequence and high motion probing gradient pulse are used at diffusion weighted imaging, causing high table vibration. The purpose of this study was to assess whether the diffusion signal and apparent diffusion coefficient (ADC) values are influenced by this vibration because of time-varying magnetic fields. Two DWIs were compared. In one, phantoms were fixed on the MRI unit's table transmitting the vibration. In the other, phantoms were supported in air, in the absence of vibration. The phantoms called "solution phantoms" were made from agarose of a particular density. The phantoms called "jelly phantoms" were made from agarose that was heated. The diffusion signal and ADC value of each image were compared. The results showed that the signal of DWI units using the solution phantom was not affected by vibration. However, the signal of DWI and ADC were increased in the low-density jelly phantom as a result of vibration, causing the jelly phantom to vibrate. The DWIs of vibrating regions such as the breast maybe be subject to error. A countermeasure seems to be to support the region adequately.

Addressing a systematic vibration artifact in diffusion‐weighted MRI

“…Vibrations could be expected to have a considerable effect, however, as previous work has demonstrated the strong sensitivity of diffusion-weighted imaging to bulk motion [Anderson and Gore, 1994;Ordidge et al, 1994;Wedeen et al, 1994]. It has been demonstrated in a gel phantom that mechanical separation of the sample from the patient table can lead to substantial changes in the measured apparent diffusion coefficient [Ogura et al, 2006], but the authors appear not to have considered a mechanism for this discrepancy or whether human brain studies are likely to be affected in the same way. In this article, we identify in vivo a pronounced artifact, which we attribute to result directly from the vibrations of the patient table which have been induced by the low-frequency switching of the gradient coils to achieve the diffusion contrast.…”

“…This was Ogura et al [2006] on a phantom by suspending the phantom within the coil attached to an apparatus not in direct contact with the MR system. Such an extreme approach is likely to be impractical for in vivo scanning, but manufacturers may wish to consider these low-frequency resonances when designing new hardware and new systems.…”

Addressing spontaneous signal voids in repetitive single‐shot DWI of musculature: spatial and temporal patterns in the calves of healthy volunteers and consideration of unintended muscle activities as underlying mechanism

“…It should be mentioned here that problems with local signal voids in diffusion sensitive images have been addressed in earlier work using the term 'systematic vibration artifact', as described by Ogura et al . for gel phantoms, by Gallichan et al . for brain, and by Lemberskiy et al .…”

A case of pseudomyxoma peritonei: visualization of septa using diffusion-weighted images with low b values

“…One hypothesis is that this phenomenon is a kind of motion artifact along the septa, induced by MRI scanner table vibration. Reportedly, the table vibration caused by motion probing gradient of DWI increased ADC values of the gelatinous phantom [9]. Because of the secondary increase of ADC values along the septa of mucinous ascites, DWI might visualize thick septa with a very low signal intensity.…”