Article Figures & Data
Figures
- Fig 1.
Dual-echo DWI pulse sequence showing the section-select module (blue); diffusion preparation period (yellow); and the first and second imaging echoes (echoes 1 and 2 acquired at 2 different TEs, TE1 and TE2) separated by a 180° refocusing pulse.
- Fig 2.
Assessment of readers A, B, and C of image quality, lesion conspicuity, and diagnostic confidence. Nominal values of 3–7 represent reader grading compared with the product DW-EPI (assigned as 4), represented by the percentage of total assigned values. Note that values of 1–2 (corresponding to “nondiagnostic” and “poor”) are not shown because these values were not assigned in this study.
- Fig 3.
Comparison of the vendor-supplied (product) DWI, echo 1, and echo 2 DWI acquired from the dual-echo sequence on 3 patients (from left to right). The ADC (calculated from echo 1) shows the presence of reduced diffusivity in each lesion (far right column). A, A 62-year-old female patient with stroke. B, A 49-year-old male patient with vasospasm and infarction post-aneurysm clipping. C, An 88-year-old woman presenting with strokelike symptoms. Note that the small infarct in the splenium of the corpus callosum present on the dual-echo DWIs was initially missed on the product DWI.
- Fig 4.
Examples of improved lesion detection of echo 2. A, A 56-year-old man status post posterior fossa tumor resection. Right cerebellar injury is more conspicuous on echo 2 and was confirmed to have reduced diffusion based on ADC. B, A 39-year-old man with known Moyamoya disease status post right superficial temporal artery to middle cerebral artery anastomosis presented with acute strokelike symptoms. Superficial temporal cortical lesion (closed arrow) and a punctate putaminal lesion (arrowhead) are confirmed with reduced diffusivity based on the ADC map. Also note improved delineation of a small subdural hematoma on echo 2 (open arrow).
- Fig 5.
Examples in which additional lesions identified by echo 2 suggested a potential underlying mechanism of stroke and potentially altered diagnostic impression and clinical management. A, A 60-year-old woman with vasospasm after subarachnoid hemorrhage. B, A 65-year-old woman with embolic infarcts who also had lesions in the right cerebral hemisphere more inferiorly (not shown). On both patients, echo 2 showed missed sites of reduced diffusivity on the contralateral hemisphere (arrows), suggesting multiple vascular distribution involvement (vasospasm in multiple vascular territories or embolic source). Note that the lesions were retrospectively observed on echo 1 (but not on the product DWI).
- Fig 6.
Examples in which the heightened sensitivity of echo 2 prompted further assessment by using ADC. A, A 61-year-old woman with hemorrhage from a cavernous malformation. Bright signal around the lesion was seen on echo 2 (and product) DWI and was confirmed as edema around a hemorrhage site (open arrows). B, A 69-year-old man with strokelike symptoms. Example of acute and subacute (closed arrows)/chronic stroke (open arrows) on echo 2 DWI, also present on the product DWI. Also note the arrowhead on echo 1 showing unwanted heightened coil sensitivity in the posterior brain region.
- Fig 7.
Case illustrating why echo 1 is more useful than echo 2 for calculating ADC maps used for the validation of acute infarct. Select images of a 66-year-old woman with embolic infarcts. DWI and ADC maps for echo 1 (A) and echo 2 (B) are shown. The DWI of echo 2 was found to have much higher sensitivity to acute lesions (confirmed on the ADC of echo 1) than echo 1. However, because the ADC of echo 2 is plagued by noise, echo 1 is considerably more useful for calculating ADC maps used for the validation of acute stroke (closed white arrows). The open white arrows represent areas where it can be difficult to rule out stroke from heightened coil sensitivity in (particularly posterior) regions of the brain.
- Fig 8.
A sample case showing the potential contribution of the R2 map. A 69-year-old female patient with vasospasm after subarachnoid hemorrhage. The low-R2 lesion is more conspicuous than the corresponding T2 hyperintensity on the FLAIR image. On the basis of DWI/ADC, this area represents acute right MCA territory infarction. The potential contribution of the R2 map with regard to timing of stroke and its evolution is unknown but prompts future investigation. The R2 map also shows more conspicuous mineralization in the basal ganglia than the gradient-recalled echo image (arrowhead).
Tables
- Table 1:
Clinical history of the 50 patients who were suspected of stroke and scanned for this studya
Clinical History No. of Patients No. of Patients with Lesions with Reduced Diffusivity Moyamoya disease 5 5 Transient ischemic attack 16 5 Stroke 14 14 Cavernous malformation 3 2 Hemorrhage 5 5 Vasospasm post-subarachnoid hemorrhage 3 3 Metabolic disease 1 0 Brain tumor 2 1 Headache 1 1 Total No. of patients 50 36 ↵a The number of patients with lesions with reduced diffusivity present on ≥1 of the scanned DWI sequences is also shown.
- Table 2:
Agreement among readers on specific ratings using a weighted κ statistic (N = 50)a
Echo 1 Echo 2 Diag Conf Conspicuity Quality Diag Conf Conspicuity Quality A vs B −0.05 0.10 0.00 0.07 −0.00 −0.09 A vs C 0.10 0.13 0.31 0.16 0.13 −0.09 B vs C 0.02 −0.02 0.00 0.09 0.14 0.31 Note:—Diag Conf indicates diagnostic confidence.
↵a All ratings are with P > .14.
Reader Fraction Percentage 95% CI P Value (1-tailed) Reader A 35/50 70% (55%–82%) .003 Reader B 38/50 76% (62%–87%) <.001 Reader C 34/50 68% (53%–80%) .008 Echo 1 Echo 2 Diag Conf Conspicuity Quality Diag Conf Conspicuity Quality A vs B 92% 84% 100% 96% 98% 100% A vs C 78% 66% 100% 96% 98% 92% B vs C 96% 92% 100% 96% 94% 94% Note:—Diag Conf indicates diagnostic confidence.
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