What causes T2 blackout?

When the intrinsic T2 of a lesion is long, T2 effects may spill over into the DW image, making it appear bright and thus mimicking restricted diffusion (“T2-shine-through”). When the T2 (or T2*) is very short, the opposite occurs, with resulting decrease in signal intensity on the DW image (“T2-blackout”).

What is diffusion restriction MRI?

Restricted diffusion is seen as high-signal intensity on DWI with corresponding reduced apparent diffusion coefficient (ADC) values. ADC is a measurement of the diffusion of water molecules in a given tissue.

What is ADC mapping in MRI?

An apparent diffusion coefficient (ADC) image, or an ADC map, is an MRI image that more specifically shows diffusion than conventional DWI, by eliminating the T2 weighting that is otherwise inherent to conventional DWI.

What is dark on T2 MRI?

On a T2-weighted scan compartments filled with water (such as CSF compartments) appear bright and tissues with high fat content (such as white matter) appear dark.

What does T2 hyperintense mean?

A hyperintensity or T2 hyperintensity is an area of high intensity on types of magnetic resonance imaging (MRI) scans of the brain of a human or of another mammal that reflect lesions produced largely by demyelination and axonal loss.

What is DWI good for?

DWI can be used for distinguishing malignant from benign and inflammatory lung lesions and helps in differentiation of small cell cancers (SCLC) from non-small cell cancers (NSCLC)[35,36].

What causes restricted diffusion on MRI?

The pathophysiologic basis of restricted diffusion in the vast majority of cases results from failure of energy-dependent adenosine triphosphate production in cell membranes resulting in intracellular cytotoxic edema, usually implying cell death.

What is dark on T2?

How to determine the effect of T2 shine through?

To confirm true restricted diffusion one should always compare the DWI image to the ADC. In cases of true restricted diffusion, the region of increased DWI signal will demonstrate low signal on ADC. ADC is a value that measures the effect of diffusion independent of the influence of T2 shine-through.

Why does T2 shine through on a DWI image?

T2 shine-through refers to high signal on DWI images that is not due to restricted diffusion, but rather to high T2 signal which ‘shines through’ to the DWI image. T2 shine through occurs because of long T2 decay time in some normal tissue.

How is the ADC related to the T2 shine-through effect?

ADC is a value that measures the diffusion independently from the T2 shine-through effect. High DWI signal and low ADC signal in the lesion confirm restricted diffusion (ex. ischemic brain injury). High DWI signal and normal to high ADC in the lesion is related to T2 shine-through effect.

When does T2 shine through in a cyst?

T2 shine through. This is most often seen with subacute infarctions due to vasogenic oedema but can be seen in other pathologic abnormalities such as an epidermoid cyst. To confirm true restricted diffusion one should always compare the DWI image to the ADC. In cases of true restricted diffusion, the region of increased DWI signal will…