Different kinetics of lung clearance of technetium-99m labelled diethylene triamine penta-acetic acid in patients with sarcoidosis and smokers

Abstract

The rate of clearance from the lungs of inhaled technetium-99m labelled diethylene triamine penta-acetic acid (99mTc-DTPA) is often increased in interstitial lung disease as well as in smoking. In smokers a bi-exponential clearance course of 99mTc-DTPA when measured over 3 h has previously been shown. This study was performed to compare the kinetics of clearance of 99mTc-DTPA, measured for 3 h, in sarcoid patients and healthy smokers. Forty-one never-smoking patients with sarcoidosis and radiological signs of intrathoracic disease were studied. The results were compared with those of 16 healthy current smokers and of 14 healthy never-smokers reported previously. A mono-exponential clearance equation described the clearance in 22 of the sarcoid patients and all normal never-smokers, but with a shorter average tracer half-life in the patients (P < 0.05). In 19 patients and all smokers a bi-exponential equation gave a significantly better curve fit. The rate of clearance of the slow component was higher in patients with sarcoidosis than in smokers (P < 0.05). The fraction of the tracer cleared by the fast clearance component was smaller in patients with sarcoidosis than in smokers (P < 0.01). Differences in kinetics of clearance of 99mTc-DTPA in sarcoidosis and smoking could thus be demonstrated, suggesting that the abnormal clearance is caused by diverging pathophysiological mechanisms.

Imaging in Sarcoidosis

“…The lung clearance of inhaled technetium-99m labeled diethylene triamine penta-acetic acid ( 99m Tc-DTPA) has been studied in pulmonary sarcoidosis. [113][114][115][116][117][118][119][120] An increased rate of lung clearance has been associated with disease activity in some studies 113,114 but not in others, 115,118 and with functional deterioration. 116 DTPA clearance sometimes returns to normal with corticosteroid therapy.…”

Aerosolised radionuclides for functional imaging in COPD/asthma

“…One is that 99m Tc-DTPA is absorbed from the lungs. The half-life of the tracer in the lungs is approximately 60 min in healthy nonsmokers, but considerably shorter in smokers and in subjects with interstitial lung diseases [20,21]. In these categories of subjects, the activity in the lungs will therefore change during image acquisition.…”