A prospective double-blind comparison of 99mTc-hydroxymethane diphosphonate (HMDP) and 99mTc-methylene diphosphonate (MDP) as bone-seeking agents was performed with 102 patients. Densitometry showed that both cancellous/compact bone and cancellous bone/soft-tissue ratios were greater with HMDP (p less than 0.05); compact bone/soft-tissue and bone lesion/normal bone ratios were the same with both agents. Bone delineation, soft-tissue uptake, and overall image quality were the same with both agents. The HMDP formulation contained 78% fewer stannous ions and had a longer useful life after technetium labeling than MDP.

Tc-99m MIBI is used as a tumor imaging agent and has been proposed to measure p-glycoprotein function, which plays an important role in tumor multidrug resistance to chemotherapy. It has been reported that lung cancer and breast cancer with a high retention of Tc-99m MIBI have been more responsive to chemotherapy than tumors with low retention. Thus Tc-99m MIBI SPECT could be used as a measure of p glycoprotein function and consequently may serve as a predictor of the tumor's responsiveness to chemotherapeutic agents. Described here are two patients with lymphomas, one with non-Hodgkin's lymphoma and the other with Hodgkin's disease, who underwent Tc-99m MIBI thoracic SPECT before and after chemotherapy. The sequential studies demonstrated a reduction in tumor size and diminished tumor uptake in one patient and disappearance of tumor uptake after a course of chemotherapy in the other patient. The data suggest that elevated Tc-99m MIBI uptake in a tumor as a result of retention by p glycoprotein not only demonstrates mediastinal involvement of lymphomas but also may be used to forecast responsiveness to chemotherapy.

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.