This allows for initial attenuation measurement of the mass. If diagnostic benign imaging characteristics are not present, a contrast-enhanced series can be performed between 60 and 90 seconds after the administration of intravenous (IV) contrast followed by a 15-minute delayed-phase imaging for evaluation of washout characteristics [15,16]. A study that substituted a 10-minute delayed-phase scan was found to have diminished sensitivity to adenomas compared with a 15-minute delay and is not generally utilized [15]. MRI MR chemical shift imaging (CSI) relies on differences in fat and water molecule precession frequencies and consists of T1-weighted in-phase and opposed-phase dual-echo gradient-recalled echo sequences when both echoes are obtained in the same breath hold. The opposed-phase echo is obtained before the in-phase echo, and lesions with intracytoplasmic fat will be detected by signal intensity loss when opposed-phase images are compared with in- phase images [17]. If MR-CSI is indeterminate, the addition of dynamic postcontrast imaging without or with the addition of T2-weighted imaging has been shown to aid in the diagnosis of adenoma [18-20]. Molecular Imaging PET can be utilized for evaluation of different adrenal abnormalities. Fluorine-18-2-fluoro-2-deoxy-D-glucose (FDG)-PET can detect hypermetabolic metastatic lesions. Patients are required to fast for 4 to 6 hours prior to injection of FDG, and data are acquired approximately 60 to 120 minutes after injection. A CT or MRI, respectively, is obtained and a PET scan that covers the same field of view. Co-registered images are then displayed on a workstation for analysis [21]. FDG, 18-F-dihydroxylphenylaalanine (DOPA), Ga-68-DOTATATE, or I-123 metaiodobenzylguanidine (MIBG) can be utilized to identify hyperfunctioning tumors, such as pheochromocytoma.
Adrenal Mass Evaluation. This allows for initial attenuation measurement of the mass. If diagnostic benign imaging characteristics are not present, a contrast-enhanced series can be performed between 60 and 90 seconds after the administration of intravenous (IV) contrast followed by a 15-minute delayed-phase imaging for evaluation of washout characteristics [15,16]. A study that substituted a 10-minute delayed-phase scan was found to have diminished sensitivity to adenomas compared with a 15-minute delay and is not generally utilized [15]. MRI MR chemical shift imaging (CSI) relies on differences in fat and water molecule precession frequencies and consists of T1-weighted in-phase and opposed-phase dual-echo gradient-recalled echo sequences when both echoes are obtained in the same breath hold. The opposed-phase echo is obtained before the in-phase echo, and lesions with intracytoplasmic fat will be detected by signal intensity loss when opposed-phase images are compared with in- phase images [17]. If MR-CSI is indeterminate, the addition of dynamic postcontrast imaging without or with the addition of T2-weighted imaging has been shown to aid in the diagnosis of adenoma [18-20]. Molecular Imaging PET can be utilized for evaluation of different adrenal abnormalities. Fluorine-18-2-fluoro-2-deoxy-D-glucose (FDG)-PET can detect hypermetabolic metastatic lesions. Patients are required to fast for 4 to 6 hours prior to injection of FDG, and data are acquired approximately 60 to 120 minutes after injection. A CT or MRI, respectively, is obtained and a PET scan that covers the same field of view. Co-registered images are then displayed on a workstation for analysis [21]. FDG, 18-F-dihydroxylphenylaalanine (DOPA), Ga-68-DOTATATE, or I-123 metaiodobenzylguanidine (MIBG) can be utilized to identify hyperfunctioning tumors, such as pheochromocytoma.