Added value in stroke imaging: accuracy and utility of additional coronal diffusion-weighted imaging

To evaluate the value of adding additional coronal diffusion-weighted imaging with the same section thickness as standard axial images to improve detection of small infarcts.

Axial and coronal diffusion-weighted images (4 or 5 mm section thickness, 1 mm gap) were studied retrospectively in two rounds of data collection. During the first round, two radiologists identified sub-centimetre infarcts on only axial images during one sitting, and only coronal images during a second sitting. During the second round, the two radiologists were asked to identify infarcts on only axial images during one sitting, and on both axial and coronal images simultaneously during the second sitting. An expert reviewer determined true infarcts and artefacts. Relative contrast-to-noise ratios (rCNR) and relative mean region of interest (rROI) within each lesion were calculated.

During the first round, sensitivity for infarct detection for the two radiologists was 92.7% and 100% on axial and 95.1% and 92.7% on coronal, respectively. During the second round, sensitivity improved from 88.9% to 98.1% for both radiologists (p=0.03). Specificity improved but did not reach statistical significance (p=0.06 and 0.12). False-negative and false-positive lesions had lower rCNR and rROI values.

Including both axial and coronal DWI images with the same section thickness in the stroke protocol improves detection of small infarcts, which can be misdiagnosed on a single imaging plane. A second imaging plane is particularly useful for subtle infarcts, even without acquiring thin-section images.