*2.1.4 Diffusion-weighted magnetic resonance imaging (DW MRI) and apparent diffusion coefficient (ADC)*

Diffusion-weighted imaging (DWI) provides unique information about the observed tissue because the image contrast between different structures

#### **Figure 9.**

*(A) T2 blade transverse mbh and (B) T1 vibe transverse mbhpostcontrast: Significant lymph node along the Bauchini valve region.*

#### **Figure 10.**

*T1 vibe coronal mbh postcontrast: Indicated blood vessels (vasa recta) as an indirect sign of inflammation.*

in this technique depends on water molecules' local diffusion properties (**Figure 14**).

Diffusion-weighted imaging is a method by which we can accurately and noninvasively monitor proton diffusion of water molecules.

Diffusion is a physical term that describes the random movement of molecules without specific transport mechanisms [46].

Diffusion imaging of water is based on the natural sensitivity of MR signals to movement. In the presence of a magnetic field gradient, protons carried by water molecules' movement receive a phase shift of transverse magnetization.

Since other types of intravoxel incoherent movements, such as capillary perfusion, can produce effects similar to those of real diffusion, it has been proposed that the term ADC (Apparent Diffusion Coefficient) be used to quantify the results of in vivo diffusion imaging experiments.

**17**

Images in which the shade of the grayscale of an individual image element (pixel) is proportional to the apparent diffusion coefficient value are ADC maps. Its high sensitivity limits clinical use of diffusion MR imaging to motion artifacts

*(A) T2 blade coronal mbh and (B) T1 vibe fs coronal mbhpostcontrast: Enterovesical fistula.*

*(A) DWI and (B) T1 vibe fs coronal mbhpostcontrast sequence: Stenosis of the ileal segment with consequent* 

*(A) T1 vibe fs coronal mbh after and (B) pre-application of paramagnetic contrast agent (B): Perianal fistulas.*

*distension of the proximal part of the small intestine - an indirect sign of affection.*

The single-shot technique directly improves diffusion recording because it significantly reduces motion artifacts and increases the measured diffusion coefficient reliability by allowing many diffusion images to be obtained in a brief time interval.

and limited hardware on conventional MR scanners.

Thus, this technique is compatible with the clinical protocol [47].

*Role of Imaging in Small Bowel Crohn's Disease DOI: http://dx.doi.org/10.5772/intechopen.96098*

**Figure 11.**

**Figure 12.**

**Figure 13.**

The apparent diffusion coefficient (ADC) is calculated by comparing images with two or more different b-factor values allowing the diffusion to be quantified.

#### **Figure 11.**

*Endoscopy in Small Bowel Diseases*

in this technique depends on water molecules' local diffusion properties

*T1 vibe coronal mbh postcontrast: Indicated blood vessels (vasa recta) as an indirect sign of inflammation.*

molecules' movement receive a phase shift of transverse magnetization.

invasively monitor proton diffusion of water molecules.

without specific transport mechanisms [46].

vivo diffusion imaging experiments.

Diffusion-weighted imaging is a method by which we can accurately and non-

*(A) T2 blade transverse mbh and (B) T1 vibe transverse mbhpostcontrast: Significant lymph node along the* 

Diffusion is a physical term that describes the random movement of molecules

Diffusion imaging of water is based on the natural sensitivity of MR signals to movement. In the presence of a magnetic field gradient, protons carried by water

Since other types of intravoxel incoherent movements, such as capillary perfusion, can produce effects similar to those of real diffusion, it has been proposed that the term ADC (Apparent Diffusion Coefficient) be used to quantify the results of in

The apparent diffusion coefficient (ADC) is calculated by comparing images with two or more different b-factor values allowing the diffusion to be

**16**

quantified.

(**Figure 14**).

**Figure 10.**

**Figure 9.**

*Bauchini valve region.*

*(A) DWI and (B) T1 vibe fs coronal mbhpostcontrast sequence: Stenosis of the ileal segment with consequent distension of the proximal part of the small intestine - an indirect sign of affection.*

**Figure 12.** *(A) T1 vibe fs coronal mbh after and (B) pre-application of paramagnetic contrast agent (B): Perianal fistulas.*

**Figure 13.** *(A) T2 blade coronal mbh and (B) T1 vibe fs coronal mbhpostcontrast: Enterovesical fistula.*

Images in which the shade of the grayscale of an individual image element (pixel) is proportional to the apparent diffusion coefficient value are ADC maps.

Its high sensitivity limits clinical use of diffusion MR imaging to motion artifacts and limited hardware on conventional MR scanners.

The single-shot technique directly improves diffusion recording because it significantly reduces motion artifacts and increases the measured diffusion coefficient reliability by allowing many diffusion images to be obtained in a brief time interval. Thus, this technique is compatible with the clinical protocol [47].

#### **Figure 14.**

*(A) T2 blade transverse mbh, (B) T1 vibe fs transverse mbh, (C) DWI and (D) ADC map: Thickening of the ileal wall with visible free water diffusion restriction.*

With this imaging technique, the whole signal from the tissue is canceled, so that only the signal of the molecules moving due to diffusion is displayed. The method is very demanding for the device, and only devices with good, strong, and fast gradients can cancel the signal enough not to see the "illumination of the T2 image", which can be sensed even with robust devices. These images are used daily to show the brain tissue that has experienced ischemia or stroke. Although the information obtained by diffusion measurements requires new studies, several reports have shown that diffusion imaging could become a powerful principle for the diagnosis of abdominal diseases [48–54].
