Tc-99m sestamibi uptake by malignant lymphoma and slow washout

99mTc-MIBI Embolus in the Late Phase of a Parathyroid Scan

We report a case of a transient focal MIBI uptake in the late, 90 minutes postinjection phase of a parathyroid scintigraphy in which SPECT/CT imaging proved valuable in delineating the nature of this incidental finding.

(99m)Tc-MIBI emboli in the lungs detected on SPECT/CT: a pitfall in parathyroid scan

Although we are familiar with artifactual, focal pulmonary F-FDG accumulations without an apparent underlying pathologic finding, similar artifact for Tc-MIBI has not been described yet. Herein, we reported incidental detection of Tc-MIBI emboli in the lungs on parathyroid SPECT/CT.

HIV-associated lymphocytic interstitial pneumonitis causes diffuse sestamibi lung uptake in myocardial perfusion imaging

Technetium-99m (^99mTc) sestamibi myocardial perfusion scintigraphy (MPI) is widely used for the diagnosis and assessment of prognosis in patients with suspected coronary artery disease. During these investigations, inspection of raw projected data for the purpose of quality control may occasionally yield incidental noncardiac findings that suggest the presence of another primary noncardiac disease. We present a 66-year-old HIV patient with a tissue diagnosis of lymphoid interstitial pneumonitis (LIP), who demonstrated a diffuse increase of ^99mTc sestamibi in bilateral lung fields both in rest and stress MPI.

Localization of abnormal parathyroid tissue with use of technetium-99m-sestamibi

OBJECTIVE

To evaluate the efficacy of "double-phase" technetium-99m-sestamibi scanning in the localization of abnormal parathyroid tissue in patients with hyperparathyroidism.

METHODS

We present a prospective review of patients with hyperparathyroidism seen at a university teaching hospital between June 1994 and May 1997. Twenty-four patients entered into the study underwent preoperative localization with double-phase technetium-99m-sestamibi. The nuclear medicine results were compared with the operative findings.

RESULTS

The Tc-99m-sestamibi scan correctly identified the location of single parathyroid adenomas in 22 patients (100%). Of the other two patients, both with diffuse parathyroid hyperplasia, one had a negative sestamibi scan and one had only the two inferior parathyroid glands localized on the sestamibi scan. One patient with recurrent hypercalcemia, who previously underwent total parathyroidectomy and parathyroid autotransplantation into the left forearm, had activity localized to that forearm but not to the neck. Subsequently, hyperplastic parathyroid tissue was successfully removed from the transplantation site. Another patient, who had previously undergone two unsuccessful surgical explorations prompted by hyperparathyroidism, had sestamibi localization of an adenoma inferior and medial to the right submandibular gland. The third surgical exploration disclosed a large adenoma medial to the carotid artery, just below the angle of the jaw. In two elderly, debilitated women with positive scans, adenomas were removed with use of local anesthesia. Of 22 patients in whom long-term follow-up was available, 21 remained normocalcemic for a mean period of 11.4 +/- 1.7 months postoperatively. One patient in whom hyperplastic parathyroid tissue had been removed from the left forearm had recurrence of hypercalcemia 1 year after operation.

CONCLUSION

Technetium-99m-sestamibi scanning is a reliable method for identifying parathyroid adenomas but not as helpful in localizing hyperplastic parathyroid glands. The precise localization of an adenoma simplifies surgical exploration and in selected patients may allow excision of the adenoma under local anesthesia. Tc-99msestamibi scanning has become the preferred method for noninvasive localization of abnormal parathyroid glands.

Technetium-99m MIBI single photon emission computed tomography as an indicator of prognosis for patients with lung cancer-preliminaly report

PURPOSE

We performed technetium-99m hexakis-2-methoxyisobutylisonitrile (Tc-99m MIBI) single photon emission computed tomography (SPECT) in 23 patients with primary lung cancer between July 1993 and March 1996. We evaluated the relationships among the uptake ratio, retention index and the prognosis after radiation therapy and/or chemotherapy.

MATERIALS AND METHODS

Tc-99m MIBI SPECT was performed at 30 minutes and at 3 hours after intravenous injection of 600 MBq of Tc-99m MIBI with three gamma camera detectors (GCA-9300A/HG) on transverse SPECT images. Regions of interest were set in the area of abnormal uptake of Tc-99m MIBI and in the contralateral normal lung. The ratio of uptake in the lesion to that in the contralateral normal lung was obtained on early images (early ratio; ER) as well as delayed images (delayed ratio: DR). The retention index (RI) was calculated as follows: RI = (DR - ER)/ER x 100. The ratio was compared with survival time and prognostic factors.

RESULTS

There was no correlation between ER and DR. The patients with high RI survived longer than those with low RI (median survival, 19.4 months vs. 9.4 months; p = 0.0104 by the Mantel-Cox test).

CONCLUSION

These results suggest that RI is the most useful among Tc-99m MIBI indices of primary lung cancer in predicting prognosis.

Visualisation of a paraganglioma by technetium-99m-sestamibi scintigraphy

A 68-yr-old woman presented to our observation with multinodular goiter and a contiguous right laterocervical mass. In spite of ultrasound, technetium and iodine scan, CT and fine-needle biopsy, the precise origin of the mass remained uncertain. On additional multi-phase sestamibi scan, the neck region showed an early high uptake rapidly decreasing over time in the laterocervical mass, and a persistent inhomogeneous distribution in the thyroid gland. This behavior suggested that the laterocervical mass could derive from an anatomical structure other than the thyroid. Surgical exploration established the extrathyroid nature of the laterocervical mass and the histological examination confirmed that it was a typical paraganglioma. This finding is in keeping with a recent report of positive sestamibi uptake in a cervical paraganglioma, although our case showed a more rapid kinetic. This tumor should be therefore taken into consideration in the differential interpretation of focal sestamibi uptake.

Tc-99m sestamibi imaging in the diagnostic assessment of patients with lymphomas: comparison with clinical and radiological evaluation

Tc-99m MIBI imaging has been used in nuclear oncology, but its role in detecting lymphomas has not been widely investigated. In this study, 31 patients with lymphomas (20 non-Hodgkin's and 11 Hodgkin's) underwent Tc-99m MIBI whole-body imaging. A total of 74 tumor lesions were detected in 25 patients, while the remaining 6 patients were disease-free. The diagnostic accuracy of MIBI imaging for lesion detection was 85%. A total of 11 unknown tumor lesions in 3 patients were discovered on MIBI scans. Tumor size was significantly (p = 0.01) higher in lesions with increased MIBI uptake (3.5 +/- 2.0 cm) compared with those with no uptake (1.8 +/- 1.0 cm). No false positive MIBI findings were observed. The accuracy of MIBI scintigraphy in patients with Hodgkin's disease was lower (72%) compared to that of patients with non-Hodgkin's lymphomas (94%). However, this difference was not related to tumor type, but to lesion size. In fact, tumor size was significantly (p = 0.02) lower in lesions of patients with Hodgkin's disease (2.5 +/- 1.3 cm) compared to those of patients with non-Hodgkin's lymphomas (3.7 +/- 2.2 cm). MIBI imaging may be useful in patients with lymphomas for detecting tumor lesions and, hence, may be considered an alternative to gallium scanning, providing better imaging quality. However, the intense Sestamibi activity in the lower chest and abdomen as well as tumor size may limit the diagnostic sensitivity of this radionuclide technique in patients with lymphomas.

Evaluation of uptake and release of technetium-99m MIBI SPECT of pulmonary and mediastinal lesions

We evaluated the uptake and release of Tc-99m MIBI in 7 benign and 30 malignant pulmonary and mediastinal lesions. Of the 37 patients, 13 underwent surgery; malignant involvement was examined in 21 mediastinal lymph nodes. Tl-201 SPECT was also performed in 10 patients. Tc-99m MIBI SPECT studies were performed on transverse SPECT images acquired 30 minutes and 3 hours after intravenous injection of 600 MBq of Tc-99m MIBI with three gamma camera detectors (GCA-9300A). Regions of interest were set in the area of abnormal uptake of Tc-99m MIBI and in an area of normal tissue in the contralateral lung. The uptake ratio of the lesion in the contralateral normal lung was obtained on the early image (early ratio; ER) as well as the delayed image (delayed ratio; DR). The benign lesions showed significantly lower ER (1.6 +/- 0.3) and DR (1.4 +/- 0.4) than the malignant lesions (1.9 +/- 0.5 and 1.8 +/- 0.5, respectively; both p < 0.05). There was no significant difference in the retention index (RI), calculated as RI = (DR-ER)/ER x 100. The DR obtained with Tl-201 SPECT images was significantly higher than that obtained with Tc-99m MIBI SPECT (p < 0.05). For the detection of mediastinal lymph node metastases, the early images showed sensitivity, specificity, and accuracy of 85.7%, 100%, and 95.2%, respectively, for the delayed images these values were 85.7%, 92.9%, and 90.5%, respectively. These results suggest that the uptake ratio of Tc-99m MIBI is a useful index in assessing benign or malignant pulmonary and mediastinal lesions.

Accumulation of 99mTc-MIBI in bone marrow

99mTc-MIBI (Sestamibi) was originally developed for myocardial perfusion studies. The agent also may be used for the depiction and characterization of tumors. Performing such examinations has shown uptake in skeletal structures in several patients suggesting bone engagement of the disease which later was excluded. Retrospective evaluation of 44 examinations with 99mTc-MIBI performed in order to localize diseased parathyroid in patients with suspected hyperparathyroidism showed skeletal activity in 21 (48%) patients. Although these patients represent a selected group, the observation indicates a mechanism for skeletal accumulation of this radiopharmaceutical. Evaluation of another 13 normocalcemic patients undergoing whole-body registration for malignancy staging or to assess lower extremity ischemia with 99mTc-MIBI showed skeletal activity in 6 (46%) patients. Complementary mouse experiments confirmed skeletal uptake of 99mTc-MIBI, where most of the activity is taken up by the red bone marrow. It is concluded that homogeneous, diffuse weak skeletal activity at examination with 99mTc-MIBI is a normal finding and does not indicate malignancy.

Sweat glands accumulate Tc-99m MIBI

Tc-99m MIBI, which was originally developed for myocardial perfusion studies, may also be used for depiction and characterization of tumors. Forty-one patients with suspected hyperparathyroidism were examined with Tc-99m MIBI to localize a parathyroid adenoma or hyperplasia. In 19 of these patients (46%), bilateral symmetrical activity corresponding to the large deep apocrine sweat glands of the axillae was present. Sweat gland activity was not correlated with serum calcium levels. Although these patients may represent a selected group, the observation is clinically relevant regardless of its reason or mechanism. It is important also to be aware of this cause for activity in the axilla when assessing lymph node involvement in breast cancer patients using Tc-99m MIBI.