Simultaneous imaging of hard and soft biological tissues in a low-field dental MRI scanner

Abstract

Magnetic Resonance Imaging (MRI) of hard biological tissues is challenging due to the fleeting lifetime and low strength of their response to resonant stimuli, especially at low magnetic fields. Consequently, the impact of MRI on some medical applications, such as dentistry, continues to be limited. Here, we present three-dimensional reconstructions of ex-vivo human teeth, as well as a rabbit head and part of a cow femur, all obtained at a field strength of 260 mT. These images are the first featuring soft and hard tissues simultaneously at sub-Tesla fields, and they have been acquired in a home-made, special-purpose, pre-medical MRI scanner designed with the goal of demonstrating dental imaging at low field settings. We encode spatial information with two pulse sequences: Pointwise-Encoding Time reduction with Radial Acquisition and a new sequence we have called Double Radial Non-Stop Spin Echo, which we find to perform better than the former. For image reconstruction we employ Algebraic Reconstruction Techniques (ART) as well as standard Fourier methods. An analysis of the resulting images shows that ART reconstructions exhibit a higher signal-to-noise ratio with a more homogeneous noise distribution.

The Chairside Periodontal Diagnostic Toolkit: Past, Present, and Future

“…As an alternative to radiography, other imaging technologies without ionizing radiation (e.g., ultrasonography or MRI) are being actively studied. It was recently found that a method using MRI can be used for both soft tissue and hard tissue observation, and based on this, it started to gain considerable interest from the periodontal disease research community [137,160]. Lastly, with the integration of state-of-the-art image processing algorithms and artificial intelligence technology, higher accuracy in diagnosis and better prediction in prognosis are expected [98,99,[161][162][163].…”

“…However, a recent study suggested overcoming the limitation of hard tissue imaging using MRI and demonstrating that using MRI can be effective for both soft tissue and hard tissue observation. Algarin et al designed a special-purpose MRI scanner (DentMRI-Gen I) capable of producing high-quality combined images of soft and hard biological tissues at sub-Tesla fields (260 mT) [ 137 ]. However, simultaneous imaging of soft and hard tissues using MRI requires more clinical validation, so there are remains opportunities for technology development.…”

A Fast 0.5 T Prepolarizer Module for Preclinical Magnetic Resonance Imaging

“…The main constraints we considered for the design of the prepolarizer were: i) it must be a module that can be easily installed into and removed from the "DentMRI -Gen I" system [17]; ii) it must produce a prepolarization field significantly higher than the evolution field 𝐵 0 ≈ 0.26 T; and iii) it must be possible to ramp the field up and down in less than 10 ms to enable PMRI of hard biological tissues.…”

“…III-B). The control system is based on a RadioProcessor-G console from SpinCore Technologies Inc. and is described elsewhere [17]. To control the prepolarizer via the console, we use a TTL line which triggers the IPM-16P switches after optical decoupling in the FT1 module (Eagle Harbor Technologies Inc.).…”

“…In this paper, we present the design and performance of a 0.5 T prepolarization module which can be integrated into our "DentMRI -Gen I" scanner [17]. The latter is a preclinical dental system with a field of view of only 10 mm in diameter when the prepolarizer is installed, so strong prepolarization fields are possible even with a low inductance (≈ 600 μH) coil.…”