However, it is known that FDG-PET/CT can also demonstrate PMR as FDG uptake in the periarticular and extra-articular structures [65]. Interestingly, a recent study has reported that many patients without cranial symptoms (ie, isolated PMR) often demonstrated LVV on FDG-PET/CT [66]. In addition to PMR, FDG-PET/CT can detect other extravascular findings (such as malignancy or infection) in patients who present with constitutional symptoms similar to vasculitis [13]. In a recent prospective cohort study of patients with suspected LVV, particularly GCA, patients underwent head, neck, and chest FDG-PET/CT. The sensitivity and specificity for the diagnosis of superficial cranial artery vasculitis were reported to be 92% and 91%, respectively, when the temporal artery biopsy was used as a reference test [14]. A similar study was performed by Nielsen et al [15], who demonstrated FDG uptake in the head and neck vessels with a high sensitivity and specificity and concluded that temporal artery biopsy could be omitted. There is also a prognostic value of head and neck FDG-PET/CT, particularly in the vertebral arteries, associated with the risk of ischemic complications [67]. A study by Michailidou et al [68] demonstrated that a pattern of FDG uptake along the head and neck vasculature can help differentiate TAK from GCA involvement without any angiographic abnormalities on MRA images. Patients with TAK present predominantly with carotid artery involvement, whereas more involvement is noted in the posterior cervical circulation (vertebral arteries) in patients with GCA. However, the authors assessed only for arterial damage on MRA, such as aneurysm, stenosis, and occlusion. The main concern with FDG-PET/CT is that its sensitivity is affected by immunosuppression [42,69,70]. In addition, patients receiving glucocorticoid treatment demonstrate an increase in FDG uptake in the liver, which can lower the diagnostic accuracy when the vessel wall and liver ratio are used [42].
Noncerebral Vasculitis. However, it is known that FDG-PET/CT can also demonstrate PMR as FDG uptake in the periarticular and extra-articular structures [65]. Interestingly, a recent study has reported that many patients without cranial symptoms (ie, isolated PMR) often demonstrated LVV on FDG-PET/CT [66]. In addition to PMR, FDG-PET/CT can detect other extravascular findings (such as malignancy or infection) in patients who present with constitutional symptoms similar to vasculitis [13]. In a recent prospective cohort study of patients with suspected LVV, particularly GCA, patients underwent head, neck, and chest FDG-PET/CT. The sensitivity and specificity for the diagnosis of superficial cranial artery vasculitis were reported to be 92% and 91%, respectively, when the temporal artery biopsy was used as a reference test [14]. A similar study was performed by Nielsen et al [15], who demonstrated FDG uptake in the head and neck vessels with a high sensitivity and specificity and concluded that temporal artery biopsy could be omitted. There is also a prognostic value of head and neck FDG-PET/CT, particularly in the vertebral arteries, associated with the risk of ischemic complications [67]. A study by Michailidou et al [68] demonstrated that a pattern of FDG uptake along the head and neck vasculature can help differentiate TAK from GCA involvement without any angiographic abnormalities on MRA images. Patients with TAK present predominantly with carotid artery involvement, whereas more involvement is noted in the posterior cervical circulation (vertebral arteries) in patients with GCA. However, the authors assessed only for arterial damage on MRA, such as aneurysm, stenosis, and occlusion. The main concern with FDG-PET/CT is that its sensitivity is affected by immunosuppression [42,69,70]. In addition, patients receiving glucocorticoid treatment demonstrate an increase in FDG uptake in the liver, which can lower the diagnostic accuracy when the vessel wall and liver ratio are used [42].