Parenchymal hypodensity

Evidence of intracranial hemorrhage, subarachnoid hemorrhage, or a large area of cerebral edema, parenchymal hypodensities, or sulcal effacement on pretreatment CT scan... 

Fig. 3.4 Thirty-two-year-old right-handed male found with left hemiparesis, dysarthria, and left hemianopsia, (a) NCCT performed 12 h postictus shows extensive cortical and subcortical parenchymal hypodensity, with sulcal effacement and compression of the right lateral ventricle, covering an area greater than one...

Of the features listed above, early parenchymal hypodensity is the most important, with a high positive predictive value (87%) for stroke as seen on follow-up neuroimaging exams [13, 32]. Cortical sweUing and sulcal effacement have not been shown to be clinically useful indicators of acute infarction - one series found no... 

PROACTII <6h 4< <30 but not comatose (except for isolated aphasia or hemianopia) No intracranial tumors, hemorrhage, significant mass effect with midline shift, or acute hypodense parenchymal lesion or effacement of cerebral sulci in >1/3 of the middle cerebral artery (MCA) territory UMI grade 1 of either the Ml segment or an M2 division of MCA... 

Fig. 30.1a-c. Pancreatic adenocarcinoma superior tumor delineation in the pancreatic parenchymal phase, a MRCP reveals stenosis of the distal CBD (arrow) with massive biliary dilatation, suggestive of tumor, b Contrast-enhanced in the CT in the pancreatic phase revels a low-density mass in the uncinate process (arrows), acljacent to the biliary plastic stent in situ, indicative of pancreatic cancer. A hypodense mass is a direct sign of tumor at CT. c In the venous-phase CT image, the lesion is not discernible... 

Since parenchymal perfusion to these liver areas does not depend on portal venous blood, they will show lack of enhancement on CT arterial portography, thus mimicking hypodense focal tumors. On intravenous dynamic CT/MR these areas show early enhancement due earlier venous return of less diluted contrast agent when compared with the portal... 

Fig. 4.2.19a,b. Axial MIP (a) and coronal VR (b) CT angiographic images show a stenosis (arrows) of the hepatic artery, with periportal edema and parenchymal infarcts in the left lohe (diffuse and inhomogeneously hypodense regions)... 

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