Usefulness of Wave-CAIPI for Postcontrast 3D T1-SPACE in the Evaluation of Brain Metastases

High-resolution postcontrast 3D T1WI is a widely used sequence for evaluating brain metastasis, despite the long scan time. This study aimed to compare highly accelerated postcontrast 3D T1-weighted sampling perfection with application-optimized contrasts by using different flip angle evolution by using wave-controlled aliasing in parallel imaging (wave-T1-SPACE) with the commonly used standard high-resolution postcontrast 3D T1-SPACE for the evaluation of brain metastases.

Among the 387 patients who underwent postcontrast wave-T1-SPACE and standard SPACE, 56 patients with suspected brain metastases were retrospectively included. Two neuroradiologists assessed the number of enhancing lesions according to lesion size, contrast-to-noise ratio_{lesion/parenchyma}, contrast-to-noise ratio_{white matter/gray matter}, contrast ratio_{lesion/parenchyma}, and overall image quality for the 2 different sequences.

Although there was no significant difference in the evaluation of larger enhancing lesions (>5 mm) between the 2 different sequences (P = .66 for observer 1, P = .26 for observer 2), wave-T1-SPACE showed a significantly lower number of smaller enhancing lesions (<5 mm) than standard SPACE (1.61 [SD, 0.29] versus 2.84 [SD, 0.47] for observer 1; 1.41 [SD, 0.19] versus 2.68 [SD, 0.43] for observer 2). Furthermore, mean contrast-to-noise ratio_{lesion/parenchyma} and overall image quality of wave-T1-SPACE were significantly lower than those in standard SPACE.

Postcontrast wave-T1-SPACE showed comparable diagnostic performance for larger enhancing lesions (>5 mm) and marked scan time reduction compared with standard SPACE. However, postcontrast wave-T1-SPACE showed underestimation of smaller enhancing lesions (<5 mm) and lower image quality than standard SPACE. Therefore, postcontrast wave-T1-SPACE should be interpreted carefully in the evaluation of brain metastasis.