What does exponential apparent diffusion coefficient mean?

The exponential apparent diffusion coefficient (eADC) is another DWI parameter calculated by the following equation: eADC = Sb/S0 = e− b×ADC, where Sb and S0 were signal intensities of DWI when the diffusion sensitization is present or absent, respectively; b was the maximal b value of DWI sequence; and e was the …

What does ADC value mean?

Apparent Diffusion Coefficient (ADC) Value: A Potential Imaging Biomarker That Reflects the Biological Features of Rectal Cancer.

What is the difference between ADC and DWI?

ADC imaging does so by acquiring multiple conventional DWI images with different amounts of DWI weighting, and the change in signal is proportional to the rate of diffusion. Contrary to DWI images, the standard grayscale of ADC images is to represent a smaller magnitude of diffusion as darker.

What is dark on ADC MRI?

By convention, higher ADC values are displayed as white while lower ADC values are displayed as dark. Hence the infarcted area of brain with low ADC values will appear dark on the ADC map (while appearing white on the conventional DW image.

How is apparent diffusion coefficient calculated?

The equation used to calculate the ADC value was as follows: ADC = −ln (S / S0) / b, where S0 is the signal intensity of no diffusion gradients and b is the b value. After data acquisition, all images were transferred to the workstation for analysis with manufacturer-supplied software.

What is T1 and T2 in MRI?

The most common MRI sequences are T1-weighted and T2-weighted scans. T1-weighted images are produced by using short TE and TR times. The contrast and brightness of the image are predominately determined by T1 properties of tissue. Conversely, T2-weighted images are produced by using longer TE and TR times.

What does an ADC do?

An analog-to-digital converter (ADC) is used to convert an analog signal such as voltage to a digital form so that it can be read and processed by a microcontroller. Most microcontrollers nowadays have built-in ADC converters. It is also possible to connect an external ADC converter to any type of microcontroller.

What does flair mean in MRI?

Fluid-attenuated inversion recovery (FLAIR) is an MRI technique that shows areas of tissue T2 prolongation as bright while suppressing (darkening) cerebrospinal fluid (CSF) signal, thus clearly revealing lesions in proximity to CSF, such as cerebral cortical lesions.

What is Swan sequence in MRI?

T2 star-weighted angiography (SWAN), or susceptibility-weighted angiography is a new, high-resolution 3D multi-echo gradient echo sequence that produces weighted averaging across images with different echo times (TEs) to achieve higher susceptibility weighting.

How is ADC value calculated?

ADC has a resolution of one part in 4,096, where 212 = 4,096. Thus, a 12-bit ADC with a maximum input of 10 VDC can resolve the measurement into 10 VDC/4096 = 0.00244 VDC = 2.44 mV. Similarly, for the same 0 to 10 VDC range, a 16-bit ADC resolution is 10/216 = 10/65,536 = 0.153 mV.

What is DWI radiology?

Diffusion-weighted imaging (DWI) is a form of MR imaging based upon measuring the random Brownian motion of water molecules within a voxel of tissue. In general simplified terms, highly cellular tissues or those with cellular swelling exhibit lower diffusion coefficients.

Is MRI a NMR?

MRI is based on nuclear magnetic resonance (NMR), whose name comes from the interaction of certain atomic nuclei in the presence of an external magnetic field when exposed to radiofrequency (RF) electromagnetic waves of a specific resonance frequency.

What is apparent diffusion coefficient on an MRI?

Apparent diffusion coefficient (ADC) is a measure of the magnitude of diffusion (of water molecules) within tissue, and is commonly clinically calculated using MRI with diffusion-weighted imaging (DWI) 1.

What is ADC in prostate MRI?

Apparent diffusion coefficient (ADC) value is a quantitative measurement of DW-MRI which has shown a promising role in the detection and localization of cancer prostate [3], [10], [11], [12], [13], [14], [15], [16].

Is a cerebral infarction the same as a stroke?

A cerebral infarction (also known as a stroke) refers to damage to tissues in the brain due to a loss of oxygen to the area.

What is ADC map?

ADC map of stroke. The ADC map is a pure display of consolidated ADC values. Because it is mathematically calculated it appears pixel-ly with spots scattered in the air around the subject. The signal intensities are opposite to those of the Trace-DW image, which can be a source of confusion.

When is gadolinium used in MRI?

Gadolinium contrast medium is used in about 1 in 3 of MRI scans to improve the clarity of the images or pictures of your body’s internal structures. This improves the diagnostic accuracy of the MRI scan. For example, it improves the visibility of inflammation, tumours, blood vessels and, for some organs, blood supply.

What is a high T2 signal on MRI?

An increase in T2 signal intensity is often associated with chronic compression of the spinal cord, and it is well established that chronic compression results in structural changes to the spinal cord.

How does Diffusion MRI work?

In diffusion MRI, magnetic field gradients are employed to sensitize the image to diffusion in a particular direction. The direction is different for each image, resulting in a different pattern of signal loss (dark areas) due to anisotropic diffusion.

What is DAC and ADC?

In electronics, a digital-to-analog converter (DAC, D/A, D2A, or D-to-A) is a system that converts a digital signal into an analog signal. An analog-to-digital converter (ADC) performs the reverse function.

What is the output of ADC?

An ADC carries out two processes, sampling and quantization. The ADC represents an analog signal, which has infinite resolution, as a digital code that has finite resolution. The ADC produces 2N digital values where N represents the number of binary output bits.

Why do we need ADC?

An analog to digital converter (ADC), converts any analog signal into quantifiable data, which makes it easier to process and store, as well as more accurate and reliable by minimizing errors.

What is T2 and FLAIR in brain?

T2/FLAIR. T2/FLAIR images show the total amount of scar from MS from its onset. The pictures show both old and new inflammation. T2/FLAIR lesions can directly account for some symptoms. For example, a brainstem lesion can cause room spinning sensations and balance problems.

Is FLAIR T1 or T2?

FLAIR MRI is a heavily T2-weighted technique that dampens ventricular CSF signal. This causes the highest signals on the sequence are from certain brain parenchymal abnormalities, such as MS lesions, while the CSF appears black.

What is a brain flare?

The periods when new symptoms appear or old ones reappear or get worse are called MS flares, or, alternatively, relapses, attacks, or exacerbations. Flares occur because of inflammation in the central nervous system — the brain and spinal cord — causing damage to the myelin or underlying nerve fibers.

What color is blood on Swi?

In early iterations of SWI in the 1980’s and 1990’s, phase information was largely discarded in favor of magnitude data to produce black-blood MR venograms and BOLD (Blood Oxygen Level Dependent) functional MRI maps.

Is a SWI a GRE?

Susceptibility-weighted imaging (SWI) is a relatively novel high-spatial resolution, three-dimensional, GRE MR sequence that exploits the magnetic susceptibility differences of various tissues or substances such as blood products, iron content and calcification.

What is a swan in a brain?

SWAN helps clearly delineate small blood vessels, microbleeds, and large vascular structures in the brain. SWAN is also designed to visualize iron and calcium deposits by providing both phase and magnitude images to aid in an easier diagnosis.