Clinical utility of technetium-99m methoxisobutylisonitrile imaging in differentiated thyroid carcinoma: comparison with thallium-201 and iodine-131 Na scintigraphy, and serum thyroglobulin quantitation.

Recently, technetium-99m methoxyisobutylisonitrile (99mTc-MIBI) has been used to image thyroid carcinoma. A prospective study was performed to compare the efficacy of 99mTc-MIBI to thallium-201 (201Tl) scintigraphy in patients with differentiated thyroid carcinoma. The clinical utility of all radionuclide imaging modalities, i.e., 99mTc-MIBI, 201Tl, and iodine-131 Na (131I-Na), as well as serum thyroglobulin estimation, was evaluated. Thirty-four post-thyroidectomy patients (age range: 26-76 years) underwent 45 studies. Histopathologies studied included fourteen papillary, eight papillary-follicular, ten follicular, one Hürthle cell, and one medullary carcinoma of the thyroid. Following optimal stimulation of endogenous thyroid stimulating hormone (i.e, TSH 50 mU/ml), the patients underwent 201Tl and 99mTc-MIBI scintigraphy. Concomitant 131I-Na scintigraphy was performed and serum thyroglobulin levels were measured. Sixteen scan sets were performed prior to 131I-Na ablation therapy. Twenty-nine scan sets were performed following 131I-Na ablation therapy. The presence or absence of thyroid cancer was established by clinical, biochemical, radiologic, and/or biopsy findings. There was no significant difference in sensitivity and specificity of 201Tl scintigraphy versus 99mTc-MIBI scintigraphy in pre- and postablation studies. 131I-Na scintigraphy with determination of thyroglobulin level was sufficient in preablation studies. Among postablation patients, the addition of 99mTc-MIBI or 201Tl offered a higher diagnostic yield. Between the 201Tl and 99mTc-MIBI studies, there was a concordance of 69% in preablation and 97% among postablation patients (P=0.027). It is concluded that 99mTc-MIBI is a suitable alternative to 201Tl scintigraphy in thyroid carcinoma, especially following thyroidectomy and 131I-Na therapy. 131I-Na scintigraphy with serum thyroglobulin is adequate in both pre- and postablation patients. Among the post-131I-Na ablation patients, 99mTc-MIBI or 201Tl is extremely valuable for tumor localization, especially when the 131I-Na whole-body scan is negative. The combination of 99mTc-MIBI or 201Tl scintigraphy with 131I-Na and serum thyroglobulin offers the highest diagnostic yield.

Thallium imaging for brain tumors with results measured by a semiquantitative index and correlated with histopathology.

BACKGROUND: The optimal management of patients with brain tumors requires knowledge of the tumor characteristics upon presentation and the discovery of recurrence after therapy. Thallium-201 (Tl-201) chloride has shown varying uptake in tumors, depending on their viability and the type and degree of malignancy. This study explores the diagnostic potential of thallium imaging in patients with brain tumors. METHODS: Forty-three Tl-201 single photon emission computed tomographic scintigrams were performed on 40 patients with intracranial neoplasms, nearly equally divided between patients with no prior treatment and patients who had prior treatment and were suspected to have recurrent tumor and/or radiation necrosis. A thallium tumor index was calculated as the ratio of counts for a region of interest drawn in the lesion area and its mirror image in normal brain tissue. A two-tailed Student's t test was performed to compare the thallium index and histopathologic findings. RESULTS: A value of 1.5 for the thallium tumor index allowed for the best correlation between the prediction of malignancy and the histopathologic results. In the pretreatment group, a thallium tumor index greater than 1.5 correlated with high grade malignancy, and less than 1.5 correlated with either a well differentiated astrocytoma or benign cyst. In the posttreatment group, a thallium tumor index greater than 1.5 correlated with recurrent and/or residual malignant tumor. CONCLUSIONS: For those patients undergoing initial evaluation, the thallium study can help in the differential diagnosis of an intracranial mass lesion and offers confirmation of results of biopsy. For those patients who already have received treatment, the study can be used to detect recurrent or residual tumor.

Indium-111-labeled anti-EGFr-425 scintigraphy in the detection of malignant gliomas.

BACKGROUND: The monoclonal antibody anti-epidermal growth factor receptor (EGFr) antibody-425, against the epidermal growth factor receptor, has the potential to bind specifically to gliomas and not normal brain tissue. A prospective study was conducted (1986-1988) to evaluate the use of Indium-111 (111In)-labeled anti-EGFr-425 in the localization of gliomas before radioimmunotherapy with Iodine-125 (125I)-labeled anti-EGFr-425. METHODS: Twenty-eight patients with intracranial neoplasms were injected intravenously with an average dose of 2.2 mCi 111In-labeled anti-EGFr-425. Planar and single-photon emission computed tomography scans were performed after 48 and 72 hours. Control studies also were performed in two cases with 111In-labeled Co 17-1A (an antibody to colorectal cancer) and in one case with unlabeled 111In chloride. RESULTS: The immunoscintigraphic findings were generally in good agreement with computerized tomographic findings. The definitive diagnosis was established by biopsy findings: 23 gliomas (1 Grade I, 5 Grade II, 6 Grade III, and 11 Grade IV), 1 meningioma, and 4 metastatic lesions. The localization of gliomas with 111In-labeled anti-EGF-425 had a sensitivity of 0.96, a specificity of 0.60 and an accuracy of 0.90. CONCLUSION: Immunoscintigraphy with 111-In labeled anti-EGFr-425 can be useful in the management of malignant gliomas, especially before radioimmunotherapy with 125I-labeled anti-EGFr-425.

Paradoxical changes in iodine-131 scintigraphic findings in advanced follicular thyroid cancer.

We present the findings on iodine-131 (131I) scintigraphy, thallium-201 (201Tl) scintigraphy and quantitative thyroglobulin (QTG) estimation in two patients with follicular carcinoma of the thyroid with extensive metastases. The lesions were initially seen on 131I scintigraphs, but were not subsequently visualized with scanning doses of 131I (5 mCi), while retaining their ability to produce increasing amounts of thyroglobulin and take up 201Tl. Implications in choosing the appropriate diagnostic tests in the management of differentiated thyroid cancer are discussed.

The role of iodine-131 and thallium-201 imaging and serum thyroglobulin in the management of differentiated thyroid carcinoma.

BACKGROUND: A prospective study was conducted to evaluate the use of iodine-131 sodium scintigraphy, thallium-201 chloride scintigraphy, and quantitative serum thyroglobulin estimation in the detection of differentiated thyroid carcinoma after thyroidectomy and iodine-131 sodium ablative therapy. METHODS: Thirty-one patients with a median age of 45.6 years (range, 20-73 years) were included in the study. After optimal endogenous thyroid-stimulating hormone stimulation (> 50 mU/ml), 53 pairs of iodine-131 and thallium-201 scans were performed. Concomitant serum thyroglobulin levels were available for 32 pairs of scans. The presence or absence of thyroid cancer was established by clinical, radiologic, and/or biopsy findings. RESULTS: The concordance between iodine-131 and thallium-201 scan findings in the presence of disease (25 scan sets) was 36%. The concordance in the absence of disease (28 scan sets) was 82%. Iodine-131 scanning was found to be significantly better (P < 0.05) than thallium-201 scanning, in terms of sensitivity (0.8 versus 0.6), specificity (0.96 versus 0.82), accuracy (0.89 versus 0.72), and the predictive value of a positive test (0.95 versus 0.75). The measurement of serum thyroglobulin had a low sensitivity (0.3) in the study but had a specificity of 1.0. CONCLUSION: It was concluded that iodine-131 sodium scintigraphy is superior to thallium-201 scintigraphy and serum thyroglobulin estimation for the detection of residual or metastatic differentiated thyroid carcinoma. However, the use of combined modalities provides a higher diagnostic yield. Thallium-201 scintigraphy was especially useful in cases in which iodine-131 scintigraphy was negative and quantitative thyroglobulin levels were elevated.

Abnormal intracerebral thallium localization in a bacterial brain abscess.

A 56-yr-old man with a prior history of renal cell carcinoma had moderately intense abnormal localization of 201Tl-chloride in a solitary brain lesion which was discovered to be a bacterial abscess. The organisms isolated by culture included Actinomycosis odontolyticus, Peptostreptococcus and Hemophilus aphrophilus. Because of the clinical presentation, MRI characteristics and thallium scintigraphic findings, the lesion had been felt to represent either a primary or a metastatic neoplasm. This case illustrates the need for caution in the interpretation of thallium brain scintigram.