Technetium-99m-hexamethylpropylene amine oxime lung scintigraphy findings in patients with Behçet's disease

Behçet's disease (BD) is a multisystem disorder that is characterized by vasculitis, and consists of a triad of recurrent ulcers of the oral and genital mucosa with relapsing uveitis. The prevalence of pulmonary involvement varies in the range of 1-10% in various studies, and its complications are severe and life threatening. To objectively assess the degree of pulmonary vascular endothelial damage in BD, the lung uptake, and the clearance rate of technetium-99m-hexamethylpropylene amine oxime (Tc-99m-HMPAO) were determined.

Twenty-three nonsmoking patients with BD (10 female, 13 male) and 11 (six female, five male) healthy nonsmoking controls underwent Tc-99m-HMPAO lung scanning, pulmonary function tests (PFT), chest radiograph examination, contrast-enhanced spiral chest computed tomography scanning, and high-resolution computed tomography examinations. Immediately after the bolus injection of 740 MBq of Tc-99m-HMPAO posterior sequential images were obtained at 1-s intervals for 150 s and subsequent images were obtained at one frame per minute (min) over a 10-min period, using a double-headed gamma camera equipped with a low-energy all-purpose parallel hole collimator. Dynamic images were used to calculate the Tc-99m-HMPAO lung clearance rate (T1/2). Simultaneously, a static anterior image, including a large part of the liver, was obtained of 5-min duration at 10 min after the injection. Regular regions of interests were drawn over the midportion of the right lung and the highest activity area of the liver parenchyma was selected and lung/liver (L/Li) uptake ratios were calculated to represent the degree of pulmonary vascular endothelial damage.

Chest radiograph, high-resolution computed tomography, and computed tomography findings in patients with BD were nonspecific for BD. There was also a statistically significant difference between patients with BD (30.26 ± 10.55 s) and normal controls (19.53 ± 6.24 s) on their T1/2 values (P = 0.0004). The results show that the L/Li ratios on the Tc-99m-HMPAO lung scan were significantly higher in patients with BD (0.60 ± 0.19) than those in normal controls (0.39 ± 0.07) (P = 0.0021). Using a cutoff value of 0.50, 15 of 23 (65%) patients with BD had increased L/Li ratios. No correlation was found between the mean T1/2 values of Tc-99m-HMPAO clearance and the PFT in patients with BD. The L/Li ratios were not correlated with PFT in patients with BD.

The degree of pulmonary vascular endothelial damage was represented as increased L/Li ratios and decreased lung clearance rate measured on the Tc-99m-HMPAO lung scan in patients with BD. Our results indicated that determining the T1/2 values and the L/Li ratios on Tc-99m-HMPAO lung imaging should be an objective method to assess subclinical pulmonary damage even in the early stages of BD in the patients.