Selection and application of coils in temporomandibular joint MRI

To compare and evaluate the signal-to-noise ratio (SNR) and the contrast-to-noise ratio (CNR) values between a 15-channel phased array head coil and 6-channel dS Flex M surface coil in the MRI of temporomandibular joint.

300 patients were randomly assigned to two groups: 150 patients were examined by using a 15-channel phased array head coil and the other 150 patients were scanned by using a 6-channel dS Flex M surface coil. All of the data were set in the same 6 regions of interest including the temporal lobe, condyle neck, lateral pterygoid muscle, parotid gland, the adipose area and an area of the background noise）. SNR and CNR values were measured respectively.

The numerical variation law of SNR and CNR values measured in regionsof interest of each group was similar, although different coils were used. There were statistically significant differences of SNR values in all of the oblique sagittal (OSag) proton density-weighted imaging, the part of OSag T ₂ weighted image (T ₂WI) except for SNR₄ and SNR₅. and oblique coronal (OCor) T ₂WI sequence except for SNR₂. On the contrary, SNR₄ and SNR₅ values in the OCor T ₂WI and SNR₅ values in OSag T ₂WI sequences by using the surface coil were higher than those by using the head coil. There were no statistically significant intergroup differences of CNR values in OSag proton density-weighted imaging sequence except CNR₁ and in OSag T ₂WI sequence except CNR₅. But, statistically significant differences of all the values in the OCor T ₂WI sequence except for CNR₁ were observed.

Both the phased array head coil and dS Flex M surface coil can be used for temporomandibular joint MRI.