Two-dimensional UTE overview imaging for dental application

Abstract

Purpose: To investigate the applicability of a 2D-UTE half-pulse sequence for dental overview imaging and the detection of signal from mineralized dental tissue and caries lesions with ultra-short $T_2^{\ast }$ as an efficient alternative to 3D sequences.

Methods: A modified 2D-UTE sequence using 240-µs half-pulses for excitation and a reduction of the coil tune delay from the manufacturer preset value allowed for the acquisition of in vivo dental images with a TE of 35 µs at 1.5T. The common occurrence of out-of-slice signal for half-pulse sequences was avoided by applying a quadratic-phase saturation pulse before each half-RF excitation. A conventional 2D-UTE sequence with a TE of 750 µs, using slice selection rephasing, was used for comparison.

Results: Quadratic phase saturation pulses adequately improve the slice profile of half-pulse excitations for dental imaging with a surface coil. In vivo images and SNR measurements show a distinct increase in signal in ultrashort $T_2^{\ast }$ tissues for the proposed 2D-UTE half-pulse sequence compared with a 2D-UTE sequence using conventional slice selection, leading to an improved detection of caries lesions.

Conclusion: The proposed pulse sequence enables the acquisition of in vivo images of a comprehensive overview of bone structures and teeth of a single side of the upper and lower jaw and signal detection from mineralized dental tissues in clinically acceptable scan times.

Keywords: 2D UTE; caries; dental imaging; half-pulse; tune delay.