Diagnostic value of high-resolution MR imaging in giant cell arteritis

Abstract

Background and purpose: Clinical indications of giant cell arteritis may be unspecific, and noninvasive diagnosis is often difficult. This study investigated the hypothesis that high-resolution MR imaging of the superficial cranial arteries is a noninvasive imaging technique that can detect the occurrence of giant cell arteritis.

Materials and methods: Contrast-enhanced, high-resolution MR imaging was performed on 64 consecutive patients with suspected giant cell arteritis. Mural thickness, lumen diameter, and a mural contrast enhancement score were assessed with T1-weighted spin-echo images with submillimeter in-plane spatial resolution. The final rheumatologist's diagnosis according to the clinical criteria of the American College of Rheumatology including laboratory tests and results of temporal artery biopsies from 32 patients was used as a "gold standard" for the evaluation of the MR imaging findings.

Results: All of the examinations provided diagnostic image quality. Evaluation of the mural inflammatory MR imaging signs for diagnosing vasculitis resulted in a sensitivity of 80.6% and a specificity of 97.0%. In comparison, histology results alone showed a sensitivity of 77.8% and specificity of 100%. The mean wall thickness increased significantly from 0.39 mm (+/-0.18 mm) to 0.74 mm (+/-0.32 mm; P < .001), and the lumen diameter decreased significantly from 0.84 mm (+/-0.29 mm) to 0.65 mm (+/-0.38 mm; P < .05) for patients with giant cell arteritis.

Conclusion: Contrast-enhanced, high-resolution MR imaging allows noninvasive assessment of mural inflammation in giant cell arteritis with good diagnostic certainty. Measures of mural thickening and contrast enhancement can be obtained in these small vessels and provide valuable vasculitic MR imaging findings.

Fig 1.

Enlargements of 3T transversal postcontrast fat-suppressed T1-weighted SE image of the superficial temporal arteries of 4 different patients representing typical images of each grade of the 4-point ranking scale. Temporal artery biopsy is negative in cases A and B, and suspected diagnosis of giant cell arteritis is validated by histology in cases C and D. The concomitant veins (arrowheads in A and C) display homogeneous signal intensity increase because of low venous flow. A, Mural thickness <0.5 mm and no mural enhancement; rating “0.” Note the intraluminal signal intensity void (light arrow) because of arterial flow. B, Mural thickness <0.5 mm with only slight contrast enhancement (light arrow), probably because of enhancing vasa vasorum; rating “1.” C, Mural thickening >0.6 mm and prominent mural enhancement (arrow); rating “2.” D, Strong mural thickening >0.7 mm and strong mural enhancement (arrow); rating “3.” The arterial lumen is still patent, as signal intensity void consistent with flow can be seen.

Fig 2.

Feature plot MR score of mural inflammation versus ESR. Patients with an elevated ESR and a high MR score are all diagnosed GCA positive according to the ACR criteria. Patients with a low ESR and a low MR score are mostly diagnosed GCA negative. Please note that 2 of the false-negative MR findings with a very low MR score are imaged after long treatment with corticosteroids. Single points in the plot may represent >1 patient in case of identical values.

Fig 3.

3T transversal contrast fat-suppressed T1-weighted SE image acquired with the large FOV that covers the entire cranial circumference. Enlargements of the temporal branch of the superficial temporal arteries (A and B) and of the superficial occipital arteries (C and D) demonstrate the cranial involvement pattern. Mural thickening and inflammatory changes are depicted in the left temporal artery (enlargement B, 0.7-mm mural thickness, rated as “3”) and occipital artery (enlargement D, 0.7-mm mural thickness, rated as “3”), whereas the right-sided arteries display no signs of mural inflammation (enlargements A and C, 0.2-mm mural thickness, both rated as “0”). Temporal artery biopsy validates GCA in this patient.