Tc-99m MIBI Thoracic SPECT for the Detection of Intrathoracic Tumor Masses

Abstract

Thirty-one men (age range, 46-76 years; mean age, 64.8 years) with intrathoracic masses suggesting possible malignancy on the basis of chest radiography or CT underwent preoperative Tc-99m MIBI SPECT examinations. Diagnosis was confirmed on pathologic examinations of samples obtained either at thoracotomy, esophagectomy, or by biopsy. Twenty-five patients had primary lung cancer, including squamous cell carcinoma, large cell carcinoma, adenocarcinoma, and small cell carcinoma. Two patients had lymphomas with spread to the mediastinum, and three patients had extrathoracic primary cancers (one squamous cell carcinoma of esophagus, one squamous cell carcinoma originating from a head and neck tumor, and one metastatic mediastinal leiomyosarcoma). One patient with a tuberculoma had negative results of the Tc-99m MIBI examination. Tc-99m MIBI had a 86.7% sensitivity rate, a 0% false-positive rate, and a 100% positive predictive value to detect malignant intrathoracic masses. There was a 13% false-negative rate, however, suggesting that MIBI-SPECT may underdiagnose malignant lesions. SPECT findings of these 31 patients can be classified as 1) mass with increased uptake, n = 23; 2) ring-like appearance of increased uptake, n = 3; 3) mass with absent uptake, n = 4; and 4) photon-deficient mass, n = 1. Absent uptake in patients with mass lesions could be explained by necrosis of the lesion (caseation necrosis or massive tumor necrosis with or without bleeding). Most malignant intrathoracic masses are Tc-99m MIBI avid and may be detected with a high degree of sensitivity and with an excellent positive predictive value. A positive MIBI scan may help in the clinical diagnosis of malignancy. The use of Tc-99m MIBI could serve not only as a tumor imaging agent, but also may be used to determine the extent of spread and potentially the chemotherapeutic responsiveness of a tumor.

The role of Tc-99m-2-Methoxy-Isobutyl-Isonitrile Single Photon Emission Computed Tomography in visualizing anterior mediastinal tumor and differentiating histologic type of thymoma

“…Its uptake mechanism involves passive diffusion across plasma and mitochondrial membranes. At equilibrium, strong negative transmembrane potentials propagate a concentration of the agent within the inner matrix of mitochondria [13]. Recently, 99m Tc-MIBI has been used as a tumor-imaging agent to detect various kind of tumors.…”

“…Many reports describe the accumulation of 99m Tc-MIBI in breast, thyroid, bone, brain, and lung cancer [10], while only sporadic cases described 99m Tc-MIBI uptake in patients with anterior mediastinal mass. Shih et al [13] valuated the role of 99m Tc-MIBI uptake as an indicator of malignancy in 31 patients with intrathoracic masses; 2/31 patients were affected by anterior mediastinal lymphoma and both showed an increased uptake of tracer on SPECT images. The role of 99m Tc-MIBI-SPECT in identifying lymphoma has been also confirmed by Maura et al [15], who reported a diagnostic accuracy of 85% for the detection of this lesion in 31 patients, of whom five patients was affected by lymphoma localized within the anterior mediastinum.…”

“…Similar to most malignancies, parathyroid tissue has a high level of mitochondrial activity and of vascularity; hence, there is an increased MIBI uptake in this pathology [14]. On the other hand, tumors with massive necrosis or those with a necrotic core did not demonstrate MIBI uptake or showed a ring-like mass to SPECT images just as MIBI does not accumulate in necrotic or irreversibly infarcted myocardial tissue [13].…”

Solitary pulmonary nodule evaluation with99mTc-methoxy isobutyl isonitrile in a tuberculosis-endemic area

“…Radiopharmaceuticals containing either technetium-99m ( 99m Tc) or thallium-201 ( 201 Tl) are more affordable than FDG since they can be produced on site and do not need a cyclotron facility. These markers accumulate in lung carcinoma and, therefore, pulmonary lesions can be evaluated with widely available gamma cameras [7][8][9][10][11]. Methoxy isobutyl isonitrile (MIBI) is taken up primarily by mitochondria and studies have shown favourable characteristics in the evaluation of SPN, albeit only in settings with low incidence of benign lesions [10][11][12].…”

“…These markers accumulate in lung carcinoma and, therefore, pulmonary lesions can be evaluated with widely available gamma cameras [7][8][9][10][11]. Methoxy isobutyl isonitrile (MIBI) is taken up primarily by mitochondria and studies have shown favourable characteristics in the evaluation of SPN, albeit only in settings with low incidence of benign lesions [10][11][12]. The present study was conducted to evaluate MIBI for the differentiation of benign from malignant pulmonary nodules in a population with high prevalence of TB and no access to a PET facility.…”