CT and Diffusion-Weighted MR Imaging in Randomized Order

Abstract

Background and Purpose-Diffusion-weighted MRI (DWI) has become a commonly used imaging modality in stroke centers. The value of this method as a routine procedure is still being discussed. In previous studies, CT was always performed before DWI. Therefore, infarct progression could be a reason for the better result in DWI. Methods-All hyperacute (Ͻ6 hours) stroke patients admitted to our emergency department with a National Institutes of Health Stroke Scale (NIHSS) score Ͼ3 were prospectively randomized for the order in which CT and MRI were performed. Five stroke experts and 4 residents blinded to clinical data judged stroke signs and lesion size on the images. To determine the interrater variability, we calculated values for both rating groups. Results-A total of 50 patients with ischemic stroke and 4 patients with transient symptoms of acute stroke (median NIHSS score, 11; range, 3 to 27) were analyzed. Of the 50 patients, 55% were examined with DWI first. The mean delay from symptom onset until CT was 180 minutes; that from symptom onset until DWI was 189 minutes. The mean delay between DWI and CT was 30 minutes. The sensitivity of infarct detection by the experts was significantly better when based on DWI (CT/DWI, 61/91%). Accuracy was 91% when based on DWI (CT, 61%). Interrater variability of lesion detection was also significantly better for DWI (CT/DWI, ϭ0.51/0.84). The assessment of lesion extent was less homogeneous on CT (CT/DWI, ϭ0.38/0.62). The differences between the 2 modalities were stronger in the residents' ratings (CT/DWI: sensitivity, 46/81%; ϭ0.38/0.76). Conclusions-CT and DWI performed with the same delay after onset of ischemic stroke resulted in significant differences in diagnostic accuracy. DWI gives good interrater homogeneity and has a substantially better sensitivity and accuracy than CT even if the raters have limited experience.

Risk for symptomatic intracerebral hemorrhage after thrombolysis assessed by diffusion‐weighted magnetic resonance imaging

“…2 Although the low interrater reliability of EIC detection on CT limits its use in clinical practice, improvements have been made by standardized CT scoring. 7,8,31 In contrast, DWI is more sensitive to EICs, 9,32,33 and interrater agreement of DWI lesion volumetry is excellent (intraclass correlation coefficient ϭ 0.968 in this study). 34 Smaller studies have investigated the prognostic value of the severity of the diffusion restriction within the DWI lesion using ADC measurements.…”

Multimodal Imaging Does Not Delay Intravenous Thrombolytic Therapy in Acute Stroke

“…20 MR imaging has also been suggested as an alternative to CT to avoid the risk associated with radiation dose. 21 Although MR imaging may be diagnostically superior to CT, [22][23][24] recent studies reported delays to imaging or IV tPA for MR imaging versus CT. In a study of 195 patients with acute stroke in Korea, the median delay to imaging was 34 minutes with CT versus 69 minutes for MR imaging.…”

Inverse mismatch and lesion growth in small subcortical ischaemic stroke

“…In stroke MRI an operational definition of the penumbra is derived from perfusion and diffusion imaging: In the acute phase of ischaemic stroke, increased signal on diffusion-weighted imaging (DWI) with an initially normal appearance on T2 images indicates areas in which anoxic depolarisation of brain cells has occurred due to severe metabolic damage, i.e. the "core zone" [1][2][3][4]. The surrounding hypoperfused but still viable cerebral tissue is characterised by a prolonged capillary mean transit time (MTT) in dynamic susceptibility perfusion MRI (PI).…”