Table of Contents
What does apparent diffusion coefficient mm2 s mean?
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.
How is ADC calculated?
Apparent diffusion coefficient (ADC) can also be calculated from multiple diffusion-weighted images easily by fitting the diffusion tensor to the signals. Traditionally, you would use one b=0 image and at least six diffusion-weighted images with the same b-value but different gradient directions.
What is the difference between DWI and ADC in MRI?
The image contrast on ADC maps is opposite to that of DWI or AC maps, in that lesions with reduced diffusion appear dark and those with elevated diffusion appear bright. In the normal adult brain, the ADC of gray and white matter are very similar, such that DWI has very little intrinsic contrast.
What does ADC mean on a prostate MRI?
To determine the utility of apparent diffusion coefficient (ADC) values in differentiation of prostate cancer from normal prostate parenchyma and prostatitis we obtained ADC values of 50 patients at b 100, 600 and 1,000 s/mm2 diffusion gradients.
What is flair in brain 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.
How long is DWI positive after stroke?
Inversely, the sensitivity of DWI for detecting recent ischemic damage starts to diminish, and may even fail to pinpoint such lesions, especially around 1 week after stroke, as seen in some of our patients.
How do you convert raw voltage to ADC?
The ADC reports a ratiometric value. This means that the ADC assumes 5V is 1023 and anything less than 5V will be a ratio between 5V and 1023. If your system is 3.3V, you simply change 5V out with 3.3V in the equation.
Is DWI T1 or T2?
When we say “DWI” we usually are referring to what is in better terms an isotropic T2 weighted map as it represents the combination of actual diffusion values and T2 signal. It is a relatively low resolution image with the following appearance: grey matter: intermediate signal intensity (grey)
What is a low ADC value?
The mean ADC value of low grade (Gleason score, ≤ 6) was 0.919 mm2/s, of intermediate grade (Gleason score 7) was 0.799 and of high grade (Gleason score, ≥ 8) tumors was 0.716 (p value < 0.001). In a larger study by Nowak et al.
What is T2 and FLAIR hyperintensities?
Focal hyperintensities in the subcortical white matter demonstrated by T2-weighted or FLAIR images are a common incidental finding in patients undergoing brain MRI for indications other than stroke. They are indicative of chronic microvascular disease.
What is high T2 FLAIR?
FLAIR MRI is a heavily T2-weighted technique that dampens the ventricular (ie, free-water) CSF signal. Thus, the highest signals on the sequence are from certain brain parenchymal abnormalities, such as MS lesions, while the CSF appears black.
Why is stroke bright on DWI?
Diffusion-weighted imaging (DWI) has been shown to contribute significantly to the early detection of acute ischemic infarction and is recognized as a bright lesion because of a drop in diffusivity (1–7). This phenomenon of restricted diffusion associated with ischemic damage persists for at least 4 to 6 days.
What is DWI stroke?
Diffusion weighted imaging (DWI) is a commonly performed MRI sequence for evaluation of acute ischemic stroke, and is sensitive in the detection of small and early infarcts.
How do you calculate ADC from voltage?
The ADC output is the ratio between the analog-signal voltage and the reference voltage. Any noise on the analog reference causes a change in the converted digital value. For example, with an analog reference of 3.3 V (VAREF = VDDA) and a 1 V signal input, the converted result is (1/3.3) × 4095 = 4D9h.
How do you convert mV to volts?
To convert a millivolt measurement to a volt measurement, divide the voltage by the conversion ratio. The voltage in volts is equal to the millivolts divided by 1,000.
What resolution is 32 bit?
Like 24-bit color, 32-bit color supports 16,777,215 colors but has an alpha channel it can create more convincing gradients, shadows, and transparencies. With the alpha channel 32-bit color supports 4,294,967,296 color combinations. As you increase the support for more colors, more memory is required.
What is T2 flair?
The T2-FLAIR mismatch sign is an imaging finding highly suggestive of isocitrate dehydrogenase mutated (IDH-mut) 1p19q non-codeleted (non-codel) gliomas (astrocytomas). In previous studies, it has shown excellent specificity but limited sensitivity for IDH-mut astrocytomas.