Phase-Sensitive T1 Inversion Recovery Imaging: A Time-Efficient Interleaved Technique for Improved Tissue Contrast in Neuroimaging

Timing diagram of the T1IR sequence. In this diagram, the number of sections packed in one TI is 3, and the maximum number of sections covered in one TR is 7. The upper part shows the interleaved scheme, and the lower part shows how the IR and FSE integrate tightly in timing. T_min is the time of IR, crusher gradient (in the phase encoding direction) and the FSE acquisition time. If the number of sections packed in the TI is less than the maximum sections allowed, there is a delay time added between crusher gradient and the FSE, and T_min stays the same.

Axial images at two different locations of a normal volunteer acquired with three different sequences. The acquisition parameters for all the three sequences are: number of sections, 42; section thickness, 3.0 mm; gap, 0.0 mm; FOV, 24 cm × 24 cm; acquisition matrix, 256 × 192; receiver bandwidth, 15.63 kHz; NEX, 1.

A and D, PS-T1IR: TE, 11.5 milliseconds; TR, 2250 milliseconds; TI, 430 milliseconds; scan time = 2 min 33 s.

B and E, T1FLAIR: TE, 11.5 milliseconds; TR, 2250 milliseconds; TI, 977 milliseconds; scan time, 2 min 38 s.

C and F, T1SE: TE, 14 milliseconds; TR, 500 milliseconds; scan time, 3 min 28 s. The PS-T1IR demonstrates excellent GM-WM contrast and CSF is totally black, as predicted from theoretical simulation in Figure 1. The superior GM-WM contrast observed with the PS-T1IR sequence relative to the T1FLAIR and T1SE sequences can easily be appreciated on these figures.

Images from an 8-year-old patient with inflammatory demyelination. PS-T1IR (A) displays much better GM-WM contrast than does regular T1SE (B) and better contrast between diseased areas of WM and normal-appearing ones (sparing of U-fibers is easily seen) with shorter scan time.

A, PS-T1IR: 256 × 192; 21 sections; FOV, 24 cm; TE, 11.5 milliseconds; TR, 2250 milliseconds; TI, 430 milliseconds; NEX, 1; receiver bandwidth, 15.63 kHz; section thickness, 5.0 mm; gap, 2.5 mm; scan time, 1:25 minutes.

B, T1SE: 256 × 192; 21 sections; FOV, 24 cm; TE, 14 milliseconds; TR, 500 milliseconds; NEX, 2; receiver bandwidth, 15.63 kHz; section thickness, 5.0 mm; gap, 2.5 mm; scan time, 2:28 minutes.

C, T2 FLAIR: FOV, 24 cm; 256 × 160; 21 sections; TE, 147 milliseconds; TR, 8800 milliseconds; TI, 2200 milliseconds; NEX, 1; receiver bandwidth, 15.63 kHz; section thickness, 5.0 mm; gap, 2.5 mm; scan time, 3:32 minutes. Note that the section location does not match perfectly, because of patient movement between scans.

Axial images obtained in a patient with multiple cerebral abscesses.

A, Several well-circumscribed mass lesions with perilesional edema are seen on the T2 FLAIR images (FOV, 24 cm; 256 × 160; 20 sections; TE, 147 milliseconds; TR, 8800 milliseconds; TI, 2200 milliseconds; NEX, 1; receiver bandwidth, 15.63 kHz; section thickness, 5.0 mm; gap, 2.5 mm). The total scan time is 3:32 minutes.

B, Pre-Gd T1SE images. The acquisition parameters are acquisition matrix, 256 × 192; total number of sections, 20; section thickness, 5.0 mm; section gap, 2.5 mm; FOV, 24 cm × 18 cm; TE, 14 milliseconds; TR, 500 milliseconds; NEX, 2; receiver bandwidth, 15.63 kHz. The total scan time is 2:28 minutes.

C, Post-Gd PS-T1IR images. The acquisition parameters are acquisition matrix, 256 × 192; total number of sections, 19; section thickness, 5.0 mm; gap, 2.5 mm; FOV, 24 cm × 24 cm; TE, 11.5 milliseconds; TR, 2250 milliseconds; TI, 430 milliseconds; NEX, 1; receiver bandwidth, 15.63 kHz. The scan time is 1:25 minutes.

D, Post-Gd T1SE images acquired with identical parameters as the precontrast images in B. Notice the motion-induced degradation of the images acquired with the T2 FLAIR and T1SE sequences.