Case Of the Week (COW) 26 Oct 2014
Answer:
eADC image showing acute left thalamic infarct.
Findings:
Acute infarct noted in the left thalamus, measuring ~ 1.2 cm. No evidence of micro / macro hemorrhage.
Discussion:
The given image is EXPONENTIAL DIFFUSION WEIGHTED IMAGING or eADC. This removes T2 SHINE THROUGH EFFECTS and reflects true restricted diffusion. The hyperintense appearance of acute infarcts on diffusion-weighted images results from a combination of abnormal diffusion and the intrinsic T2 properties which is difficult to determine on diffusion-weighted images alone. To remove the T2-weighted contrast, the DW image IS divided by the echo-planar spin-echo T2-weighted (or b = 0 s/mm2) image to give an “exponential image” that combines the advantages of DW images and ADC maps . Whereas on an ADC map, an acute infarct is seen as a hypointense region against an intermediate signal intensity background with relatively poor lesion conspicuity, on exponential images, an acute infarct is seen as a hyperintense lesion against a background of intermediate signal intensity normal brain tissue with high lesion conspicuity . An exponential image can detect area with restricted diffusion more accurately as it combines the advantages of both DWI and ADC,by removing the“ T2 shine-through effect” in DWI, and higher lesion conspicuity without CSF contamination seen on ADC.
Contributed By:
Prof.S. Babu Peter, Dr. Srinivasaraman, Dr. Suriyakumar
Barnard Institute of Radiology, Anderson Diagnostics
Answer:
eADC image showing acute left thalamic infarct.
Findings:
Acute infarct noted in the left thalamus, measuring ~ 1.2 cm. No evidence of micro / macro hemorrhage.
Discussion:
The given image is EXPONENTIAL DIFFUSION WEIGHTED IMAGING or eADC. This removes T2 SHINE THROUGH EFFECTS and reflects true restricted diffusion. The hyperintense appearance of acute infarcts on diffusion-weighted images results from a combination of abnormal diffusion and the intrinsic T2 properties which is difficult to determine on diffusion-weighted images alone. To remove the T2-weighted contrast, the DW image IS divided by the echo-planar spin-echo T2-weighted (or b = 0 s/mm2) image to give an “exponential image” that combines the advantages of DW images and ADC maps . Whereas on an ADC map, an acute infarct is seen as a hypointense region against an intermediate signal intensity background with relatively poor lesion conspicuity, on exponential images, an acute infarct is seen as a hyperintense lesion against a background of intermediate signal intensity normal brain tissue with high lesion conspicuity . An exponential image can detect area with restricted diffusion more accurately as it combines the advantages of both DWI and ADC,by removing the“ T2 shine-through effect” in DWI, and higher lesion conspicuity without CSF contamination seen on ADC.
Contributed By:
Prof.S. Babu Peter, Dr. Srinivasaraman, Dr. Suriyakumar
Barnard Institute of Radiology, Anderson Diagnostics