Tc-99m MIBI uptake secondary to pulmonary interstitial fibrosis in progressive systemic sclerosis

Tc-99m sestamibi before and during treatment in a patient with sarcoidosis and persistent hyperparathyroidism

PURPOSE

Tc-99m sestamibi (MIBI) uptake in pulmonary sarcoidosis has been reported, but it has never been studied before and during treatment with glucocorticoids.

METHODS

The authors performed MIBI scintigraphy and somatostatin receptor scintigraphy in a patient with sarcoidosis of the mediastinum, lungs, and liver and who had persistent hyperparathyroidism after unsuccessful neck exploration.

RESULTS

Somatostatin receptor scintigraphy showed high mediastinal and pulmonary uptake in a pattern characteristic of sarcoidosis. Sustained MIBI uptake occurred in the same, although smaller, region. After the diagnosis was confirmed by liver biopsy, the patient was treated with glucocorticoids. Repeated MIBI scintigraphy showed that the uptake in the mediastinum had clearly decreased.

CONCLUSIONS

This decrease of MIBI uptake in the mediastinal lymph nodes with therapy may imply that MIBI can be used to assess the response to treatment in sarcoidosis. Perhaps a relation exists between MIBI uptake at the moment of diagnosis and prognosis. Further studies in more patients are needed to evaluate the role of MIBI in the management of sarcoidosis.

Abnormal uptake of Tc-99m MIBI, a novel myocardial imaging agent, in the lungs of patients with systemic sclerosis

OBJECTIVE

Fibrosing alveolitis is a prominent feature of systemic sclerosis (SSc), and accounts for much of the morbidity and mortality of this disease. Sensitive techniques for the detection and monitoring of fibrosing alveolitis could target patients for early therapeutic intervention. The objective of this small pilot study was to assess the frequency and clinical significance of abnormal lung uptake of Tc-99m MIBI, a novel radionuclide imaging agent that selectively accumulates in cells rich in mitochondria.

METHODS

Sixteen patients with SSc and evidence of pulmonary involvement were studied. The uptake of radionuclide in the lungs, and the ratio of pulmonary to cardiac uptake were evaluated after intravenous injection of Tc-99m MIBI. Results were correlated with clinical and laboratory parameters.

RESULTS

Lung uptake of Tc-99m MIBI was increased in all 16 SSc patients compared to control patients with coronary heart disease but no evidence of pulmonary abnormality. The degree of isotope uptake in the lungs was correlated with the extent of maximal skin induration and with radiologic evidence of interstitial lung disease, but not with other clinical or laboratory parameters of disease activity or extent of pulmonary involvement. The ratio of pulmonary to cardiac uptake of isotope was also increased in patients with SSc compared to controls.

CONCLUSION

Accumulation of Tc-99m MIBI is abnormally elevated in the lungs of SSc patients with pulmonary involvement. Isotope accumulation in the lungs may be related to activation of fibroblasts or endothelial cells. The specificity and sensitivity of Tc-99m MIBI scanning in the detection and monitoring of pulmonary involvement, and its potential role in the management of SSc, deserve further investigation.

Effectiveness of Tc-99m sestamibi compared to Ga-67 in patients with pulmonary sarcoidosis

The authors evaluated the suitability of Tc-99m MIBI to be used as an alternative to Ga-67 in pulmonary sarcoidosis imaging. Studies were performed on 21 patients. Eleven patients (group I) had been on corticosteroid treatment before the study, while 10 patients (group II) had received no treatment. Activity of sarcoidosis was assessed from clinical manifestations of the disease, pulmonary function tests, bronchoalveolar lavage, high-resolution computed tomography, and serum biochemistry. Ga-67 imaging results were abnormal in 73% of patients of group I (n = 8) and 90% of patients of group II (n = 9). Tc-99m MIBI imaging results were abnormal in 0% of patients of group I (n = 0) and 40% of patients of group II (n = 4). The lymph nodes were better demonstrated with Ga-67. Abnormal results of Ga-67 imaging were 100% sensitive to clinically active sarcoidosis, but had a relatively low specificity (33%). In contrast, abnormal MIBI imaging had very low sensitivity (11%). The authors conclude that planar Tc-99m MIBI scintigraphic images are not sensitive for the diagnosis of pulmonary sarcoidosis.

Effectiveness of Tc-99m MIBI scintigraphy in diagnosing lung cancer

The use of Tc-99m hexakis 2-methoxy isobutyl isonitrile (MIBI) scintigraphy for qualitative diagnosis was examined. A total of 37 lesions from 31 patients with respiratory disease (19 lesions from 19 primary lung cancer patients, 8 lesions from 3 metastatic lung cancer patients and 10 lesions from benign lung disease patients) were examined. Positive results were seen in 89.4% of the primary lung cancer lesions, 50.0% of the metastatic lung cancer lesions, and 20.0% of the benign lung disease lesions. The positive rate of 77.7% for malignant lung cancer was significantly higher (P < 0.01) than that for benign lung cancer. In particular, for lesions with a tumor diameter of 1.0 cm or more, the positive rate for malignant lung cancer lesions (95.2%) was significantly higher (P < 0.001) than that for benign lung disease lesions (25.0%). These results thus indicate Tc-99m MIBI scintigraphy to be useful for qualitative diagnosis of lung peripheral coin lesions with a diameter of 1.0 cm or more.