Halo sign

Wenzel, J.S., Donohoe, A., Ford, K.L., Glastad, K., Watkins, D., Mol-menti, 15. Primary biliary cirrhosis MR imaging findings and description of MR imaging periportal halo sign. Amer. J. Roentgenol. 2001 176 885-889... 

Ulcerative colitis is a mucosal disease that primarily affects the rectum. It is typically left-sided or diffuse, and only rarely involves the right colon exclusively [64]. The mean wall thickness in Crohn disease is usually greater than in ulcerative colitis [65]. The halo sign, a low-attenuation ring in the bowel wall caused by deposition of submucosal fat, is seen more commonly in ulcerative colitis than in Crohn disease. Proliferation of mesenteric fat is almost exclusively seen in Crohn disease, whereas proliferation of perirectal fat is nonspecific and can result from Crohn disease, ulcerative colitis,pseudomembranous colitis, or radiation colitis [64]. Abscesses are almost exclusively found in Crohn disease and not in ulcerative colitis [62]. 

Fig. 19.4. Amplitude-coded color Doppler sonography in glomerulonephritis ( halo -sign ). Amplitude-coded color Doppler sonography demonstrates a small cortical peripheral rim- or halo-like layer with no color signals, indicating peripherally reduced flow (in spite of normal R1 values) in a patient with glomerulonephritis...

On chest radiographs and CT, IPA appears as one or more nodular opacities. On CT, the CT halo sign may be seen a zone of ground glass opacity surrounding the nodule (Fig. 2.2.6). The nodular... 

Fig. 6.2.3. Halo sign due to angioinvasive aspergillosis in a 47-year-old woman after allogeneic hematopoietic stem cell transplantation. Close-up view of a HRCT scan at the right lower lohe shows a peripheral nodular opacity with a surrounding halo of ground-glass attenuation. These findings correspond to a nodular area of infarction surrounded by hemorrhage...

Primack SL, Hartman TE, Lee KS, Muller NL (1994) Pulmonary nodules and the CT halo sign. Radiology 190 513-515... 

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