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High‐contrast osteochondral junction imaging using a 3D dual adiabatic inversion recovery‐prepared ultrashort echo time cones sequence

While conventional MRI sequences cannot visualize tissues from the osteochondral junction (OCJ) due to these tissues' short transverse T2/T2* relaxations, ultrashort echo time (UTE) sequences can overcome this limitation. A 2D UTE sequence with a dual adiabatic inversion recovery preparation (DIR‐UTE) for selective imaging of short T2 tissues with high contrast has previously been developed, but high sensitivity to eddy currents and aliased out‐of‐slice excitation make it difficult to image the thin layer of the OCJ in vivo. Here, we combine the DIR scheme with a 3D UTE cones sequence for volumetric imaging of OCJ tissues in vivo, aiming to generate higher OCJ contrast compared with a recently developed single IR‐prepared UTE sequence with a fat saturation module (IR‐FS‐UTE). All sequences were implemented on a 3‐T clinical scanner. The DIR‐UTE cones sequence combined a 3D UTE cones sequence with two narrow‐band adiabatic IR preparation pulses centered on water and fat spectrum frequencies, respectively. The 3D DIR‐UTE cones sequence was first applied to a phantom, then to the knees of four healthy volunteers and four patients diagnosed with osteoarthritis and compared with the IR‐FS‐UTE sequence. In both phantom and volunteer studies, the proposed DIR‐UTE cones sequence showed much higher contrast for OCJ imaging than the IR‐FS‐UTE sequence did. The 3D DIR‐UTE cones sequence showed a significantly higher contrast‐to‐noise ratio between the OCJ and subchondral bone fat (mean, standard deviation [SD]: 25.7 ± 2.3) and between the OCJ and superficial layers of cartilage (mean, SD: 22.2 ± 3.5) compared with the IR‐FS‐UTE sequence (mean, SD: 10.8 ± 2.5 and 16.3 ± 2.6, respectively). The 3D DIR‐UTE cones sequence is feasible for imaging of the OCJ region of the knee in vivo and produces both high resolution and high contrast.