**6. Giant cell arteriti's case studies**

In this chapter, two case studies were conducted to assess the connected threshold and region growing segmentation algorithms as a semi-automatic detection and quantification of temporal arteritis on US and MRA images. The histogram threshold analysis was performed to analyze and study the pixel distribution in both mages. Otsu's method was used to divide the images into two parts, namely; foreground and background regions. To segment the temporal artery, we performed the threshold segmentation algorithm on the foreground region by comparing two different statistical distributions. The semi-automatically segmented regions were compared with manually segmented regions. The segmentations were validated by experts and the different similarity metrics were used to identify the variations in segmentation.

#### **6.1 US case study**

In the clinical application, the temporal artery characteristics can be found and detected using US images. GCA detection compared to the normal artery is

#### **Figure 3.**

*Color doppler ultrasound showing longitudinal (a) and transverse (b) views of normal temporal artery and acute temporal arteritis. (c, d) The arrows indicate the vasculitis wall swelling [27].*

shown in **Figure 3** [27]. The data in **Figure 3(a)** and **(b)** show the longitudinal and transverse views of normal temporal artery and acute temporal arteritis in **Figure 2(c)** and **(d)** of an adult women aged 45 years old. As seen in **Figure 2**, the arrows indicate the vasculitis wall swelling. The ultrasonography features showed a hypoechogenic halo of the temporal artery in longitudinal (left) and transverse (right) view. The data show that the normal artery diameter is 0.3-1 mm and the temporal artery diameter is 1-2 mm.

In our proposed method, the US image data of a 40 years old female patient with a visible thickening of the left temporal artery that causes a chronic left temporal headache was used to test our segmentation method. [Radiopaedia. org/GCA case studies] The data is validated by comparing the artery wall segmentation results with the manual ones from experts. The typical US image used in this chapter is shown in **Figure 4(a)** and **(b)**. **Figure 4(a)** shows a longitudinal view of GCA with wall thickness on the lower side of the temporal artery. **Figure 4(b)** shows the results of segmented regions using the threshold segmentation. The area in yellow represents the wall segment, the red indicates the blood segment while the green area represents the GCA region of interest. The temporal artery has been well-segmented and the clinical characteristics have been identified and documented. The results show the diameters of the lumen, wall, and the blood flows velocity at the region of interest along with the superficial temporal artery. The diameter of the artery wall was significantly thicker than the normal artery. The GCA region of interest diameter was 1.6 mm with an area of 19.9 cm<sup>2</sup> .

#### **6.2 MRI case study**

The MRI case study represents a patient of a 50-year-old female with clinical suspicion of temporal arteritis, the left temporal artery and its frontal and parietal branches show significant wall thickening [12].

*Medical Image Processing and Analysis Techniques for Detecting Giant Cell Arteritis DOI: http://dx.doi.org/10.5772/intechopen.97161*

#### **Figure 4.**

*The left temporal artery of 40 years female patient, (a) shows the temporal artery before segmentation, (b) the threshold segmentation of GCA region of interest [12].*

#### **Figure 5.**

*The left temporal artery of 50 years female patient, (a) shows the temporal artery before segmentation, (b) the threshold segmentation of GCA region of interest [12].*

Prominent mural enhancement is identified in these arteries when compared to the contralateral side. The contralateral temporal artery and its branches show a normal appearance.

The high-resolution MRI imaging of the superficial temporal artery is shown in **Figure 5(a)** and **(b)**. The arrow in **Figure 5(a)** shows the position of the abnormal temporal arteries. The images in **Figure 5(b)** show the frontal branch and the parietal branch after image pre-processing and enhancement. The region growing segmentation of the region of interest in both images shows the GCA regions. The average superficial temporal artery wall thickness was 0.71 mm. According to the literature mural thickening >0.5 mm was considered as a sign of mural inflammation [28].
