Objective measurement of CBV lesion volume.

<p>The six smaller images depict low-CBV lesions that were delineated automatically, in a single slice of one patient’s CBV maps, by rendering in white all brain pixels in which CBV was below each of six different thresholds. Each threshold is listed below its corresponding image, along with the total volume of tissue with CBV below that threshold in all slices. For clarity, the lesions identified by only three of the six absolute thresholds are shown in the top row, and lesions identified by only three of the six relative thresholds are shown in the bottom row. The larger image on the right is a DWI image obtained from the same patient, at approximately the same level. The gold standard core volume, measured over all DWI slices, was 117 mL.</p

Objective measurement of CBV lesion volume in a second patient.

<p>The six smaller images depict low-CBV lesions that were delineated automatically, in a single slice of a second patient’s CBV maps, by rendering in white all brain pixels in which CBV was below each of six different thresholds. Each threshold is listed below its corresponding image, along with the total volume of tissue with CBV below that threshold in all slices. For clarity, the lesions identified by only three of the six absolute thresholds are shown in the top row, and lesions identified by only three of the six relative thresholds are shown in the bottom row. No lesions were seen in a DWI image acquired at approximately the same level (upper right), although DWI images acquired more superiorly showed several small lesions whose total volume was 6 mL (bottom right, arrows).</p

Subjective measurement of CBV lesion volume.

<p>Two radiologists (R1 and R2) subjectively outlined regions of abnormally low CBV. In doing so, the radiologists had access to all available CTP images, and to clinical history (in this case, “left face, arm, and leg weakness and left hemianopia”). The patient and slice location are the same as those in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0133566#pone.0133566.g001" target="_blank">Fig 1</a>. R1 did not detect a lesion, i.e. he measured the core lesion volume to be 0 mL. R2 outlined several lesions (yellow outlines and small arrows) with a total volume of 18 mL. R2 failed to identify the presence of infarction in the left cerebral hemisphere (large yellow arrow in the DWI image), which suggested an embolus of central origin rather than one arising from the right internal carotid artery.</p

Subjective measurement of CBV lesion volume in a second patient.

<p>Two radiologists (R1 and R2) subjectively outlined regions of abnormally low CBV. In doing so, the radiologists had access to all available CTP images, and to clinical history (in this case, “aphasia and right face, arm, and leg weakness”). The patient and CT slice location are the same as those in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0133566#pone.0133566.g003" target="_blank">Fig 3</a>. R1 did not detect a lesion, i.e. he measured the core lesion volume to be 0 mL. R2 outlined several lesions (yellow outlines and large arrows) whose total volume was 3 mL. Although R2’s subjective lesion volume was very close to the actual DWI lesion volume of 6 mL, none of the CBV lesions that R2 outlined corresponded to actual DWI lesions. No lesions were present in a DWI image obtained at approximately the same level as these CTP maps (upper right), and all of the DWI lesions that were present were located more superiorly (lower right, small arrows).</p

Comparison of core lesion measurement methods.

<p>Notes: (1) Sensitivity and specificity refer to CBV maps’ ability to identify patients with true DWI lesions, irrespective of lesion volumes. (2) “Core overestimation” refers to the quantity by which CBV lesion volume exceeded true DWI lesion volume.</p><p>Comparison of core lesion measurement methods.</p