Diffusion / perfusion study for human
The overall goal of this project is to accuratelydetect and diagnose superacute cerebral ischemia, and to examinemicroenvironment of tissue characteristics in human brain usingdiffusion- and perfusion-weighted echo planar imaging.
(1) Hemorrhagic and nonhemorrhagic stroke
There are few reports of DWI studies relatedto acute intracerebral hemorrhage, which may show sudden neurologicdeficits similar to ischemic infarction. Discrimination betweenacute infarction and acute cerebral hemorrhage is important becausethese diseases require quite different therapies even with similarclinical symptoms. In addition, although temporal evolution ofan ADC in infarction was previously reported, there are no reportsabout an ADC change in hemorrhagic infarction, observed in someinfarction cases. We tested the hypothesis that diffusion- andT2-weighted EPI can detect acute hemorrhagic and nonhemorrhagicstroke, and distinguish between them. We also compared these typesof stroke regarding temporal evolution of the ADC and EPI intensities.
Acute hemorrhagic stroke, showing decreasedADC, as well as nonhemorrhagic stroke was easily detected usingDWEPI. In addition, acute hemorrhagic stroke including hypointensityarea on T2WEPI was discriminated from acute nonhemorrhagic strokeshowing normal to increased signal intensity. Decreased ADC inhemorrhagic stroke tended to persist longer than those in nonhemorrhagicstroke. The combination of DWEPI and T2WEPI may be an excellentdiagnostic tool for hyperacute and acute cerebrovascular diseasesincluding both nonhemorrhagic and hemorrhagic stroke. Knowledgeof DWEPI hyperintensity in acute hemorrhagic stroke may be importantin avoiding erroneous diagnoses of acute DWI hyperintensity.
(Ebisu T, et al. Radiology 203: 823-828, 1997)
(2) Discrimination of brain abscess from cysticor necrotic brain tumors
Diagnostic difficulties in discriminating brainabscess from necrotic or cystic tumors using conventional CT andMRI have been reported. In conventional MRI, the patterns in thebrain abscess resemble cystic or necrotic neoplasms such as metastaticbrain tumors, because the abscess fluid has the same T1 and T2characteristics as these tumors, making differentiation of thepathology difficult. We examined the diagnostic ability of diffusion-weightedimaging to discriminate brain abscess from necrotic or cystictumors. In previous reports, necrotic or cystic tumors show lowsignal intensity in diffusion-weighted imaging, indicating a highapparent diffusion coefficient (ADC). In contrast, in our studyhigh signal intensity was observed in the abscess fluid, associatedwith low ADC.
(Ebisu T, et al. Magn Reson Imaging14: 1113-1116, 1996)
(3) Perfusion MRI
In our routine clinical practice, perfusionimaging such as Gd-contrast imaging and FAIR are examined in patientswith cerebral ischemia and brain tumor. The goal of this projectis to compare perfusion parameters in perfusion MRI with thosein PET and SPECT, which were previously golden standards of perfusionimaging. Another goal is to identify the correlation of apparentdiffusion coefficients with perfusion MRI parameters in lesionsof ischemic core and penumbra. (Work in progress)
(4) Can DWI provide any information of thereversibility in human cerebral ischemia?
The DWI is now a promising technique for earlydetection of cerebral infarction in routine clinical practice.However, in clinical study, the correlation of the apparent diffusioncoefficient (ADC) and reversibility in the ischemic lesion isstill unknown. In previous reports in animals, DWI signal intensityremained unchanged until the regional cerebral blood flow wasreduced to 15-20 ml/100g/min and below, which is similar to thecritical flow threshold for maintenance of tissue high-energymetabolites and ion homeostasis. This finding might support thateven presence of severe neurologic abnormalities with DWI normointensityis potentially reversible. On the other hand, in another animalstudy, DWI hyperintensity with reduced ADC during middle cerebralartery occlusion is rapidly reversible after reperfusion. Thisdata might support neurologic function even with DWI hyperintensityis also potentially reversible. The goal of this study was todetermine if clinical information of reversibility in acute ischemiacould be available using DWI. (Work in progress)
Last Updated by T.Ebisuon 5/01/98