Relative value of thallium-201 and iodine-131 scans in the detection of recurrence or distant metastasis of well differentiated thyroid carcinoma

Radioactive iodine (¹³¹I) has been found to be more sensitive and more specific than thallium-201 for the detection of distant metastases and thyroid remnants in the neck in cases of well-differentiated thyroid carcinoma. ²⁰¹Tl has been deemed particularly useful in localizing metastases or recurrence in patients with a negative ¹³¹I scan and abnormal levels of serum thyroglobulin (Tg). This study aimed to: (1) determine the value of ²⁰¹Tl imaging in localizing metastases or recurrence in patients with well-differentiated thyroid carcinoma, and (2) evaluate the false-positive and false-negative results of ¹³¹I and ²⁰¹Tl scintigraphy. Sixty-two thyroid remnant ablated patients who underwent simultaneous postoperative ²⁰¹Tl and ¹³¹I scans and and serum Tg determinations were evaluated. Fifty patients had papillary thyroid carcinomas and 12 had follicular thyroid carcinomas. ²⁰¹Tl imaging was performed before the ¹³¹I studies. Of the 62 patients who underwent ²⁰¹Tl imaging studies, 24 were found to have positive results, with local recurrence or distant metastases. Patients with positive results in the ²⁰¹Tl imaging studies tended to be older, were mor often male, had higher Tg levels and had a higher recurrence rate. Of these 24 patients, ten had negative diagnostic or therapeutic ¹³¹I scans. Concurrently, serum Tg levels were less than 5 ng/ml in five of these ten patients. Three patients were deemed false positive by ²⁰¹Tl scans; one had a parotid tumour, one a periodontal abscess and one lung metastasis. Among the 38 patients with negative ²⁰¹Tl scans, 11 had positive findings on ¹³¹I scans. Three had distant metastases: two with lung metastases and one with bone metastases. Patients with false-positive results on ¹³¹I scans included those with biliary tract stones, ovarian cysts, and breast secretion. Of the 27 patients with negative ²⁰¹Tl and ¹³¹I scans, 15 had elevated serum Tg levels. Among these, local recurrence followed by lung metastases was manifested in a 49-year-old male with papillary thyroid carcinoma. In conclusion, both ¹³¹I and ²⁰¹Tl scans are useful in the detection of recurrence or distant metastasis of well differentiated thyroid cancers. ²⁰¹Tl scan could in particular be used in patients with a negative ¹³¹I scan in conjunction with an elevated Tg level. Received 16 January and in revised form 8 April 1998     

Radioiodine whole-body scans, thyroglobulin levels, 99mTc-MIBI scans and computed tomography: results in patients with lung metastases from differentiated thyroid cancer

OBJECTIVES: The correlation between a 131I whole-body scan (WBS), a 99mTc sestamibi (99mTc-MIBI) WBS, a computed tomography (CT) scan and the value of routine follow-up for 131I WBS and thyroglobulin (Tg) levels in patients with lung metastases from differentiated thyroid cancer was assessed. METHOD: Pulmonary metastases were detected in 32 patients out of 583 with differentiated thyroid cancer (DTC) who were admitted to our clinic between 1985 and 2004 (age range, 22-79 years; mean, 58 +/- 19 years; 15 women and 17 men). Pulmonary metastases were diagnosed by considering the 131I WBS, increased Tg levels and/or other positive radiological findings. Papillary carcinoma was diagnosed in 15/32 patients and follicular carcinoma in 13/32. A mixed type found in 4/32 patients was classified histopathologically. A total of 3.7-53.65 GBq (100-1450 mCi) 131I was given to each patient. The duration of follow-up ranged from 36 to 240 months. A 131I WBS, the determination of Tg levels and/or a CT scan were carried out in the assessment of a diagnosis and follow-up of patients with lung metastases. A 99mTc-MIBI WBS was performed on 19 patients who were chosen at random from the 583. RESULTS: Nineteen of 32 patients had lung metastases before they received the first 131I treatment. Six of the 32 had distant-organ metastases other than in the lungs. Four of these six patients had only lung and bone metastases. Pulmonary metastases were observed on the 131I WBS patients 31/32 (96.8%) whereas no pulmonary metastases, were detected on the CT scans in 3/32 patients. The last diagnostic whole-body scan (DWBS) was normal in 13/32 patients. At the first examination, the Tg levels in 27/32 (84.4%) patients were below 30 ng . ml(-1). At the final examination, 20/32 (62.5%) patients had Tg levels higher than 30 ng . ml(-1), while Tg levels were lower than 30 ng . ml(-1) in 12/32 patients. Tg levels decreased in 21/32 and increased in 3/32 patients. The 131I WBS continued to be abnormal in 2/3 patients with increased Tg levels but became normal in one patient whose CT scan still showed macro-nodular lesions. Tg levels did not change significantly in 8/32 patients. The 131I WBS became normal in 5/8 patients, while the CT scans for 4/5 showed micro-nodules. Metastases were detected in 12/19 patients who underwent 99mTc-MIBI whole-body scanning: 18/19 showed metastases on the 131I WBSs and 17/19 on the CT scans. Of the seven patients without a sign of metastasis on the 99mTc-MIBI WBS, one was negative in terms of metastasis on the 131I WBS and one on the CT scan. Fibrosis was observed on the CT scans of 2/32 patients. One patient developed dedifferentiation, as determined by the negative 131I WBS and positive CT scan. CONCLUSION: 131I whole-body scanning and the determination of Tg levels are the most important procedures for the evaluation of lung metastases in differentiated thyroid cancer. Computed tomography is a useful addition to 131I whole-body scanning. MIBI imaging alone may not be enough to detect lung metastases from differentiated thyroid cancer.     

Comparison of 99Tcm-tetrofosmin with 201Tl and 131I in the detection of differentiated thyroid cancer metastases

The purpose of this study was to assess the detectability of metastatic lesions by 99Tcm-tetrofosmin in differentiated thyroid cancer, and to compare the results with those obtained using 201Tl-chloride and tracer doses of 131I. Twenty-four thyroidectomized patients with metastases were studied. There were 34 metastases, including 16 lung, nine lymph node and nine bone. Radiological studies (chest X-ray, computed tomography and magnetic resonance imaging), serum thyroglobulin assays and histopathological examinations were performed to verify the presence of metastases with positive uptake of the three radionuclides. Increased accumulation of 99Tcm-tetrofosmin was observed in 11 of 16 (68.8%) lung metastases, eight of nine (88.9%) lymph node metastases and eight of nine (88.9%) bone metastases. Increased accumulation of 201Tl and 131I was observed in 11 of 16 (both) (68.8%) lung metastases, eight (88.9%) and three (33.3%), respectively, of lymph node metastases and eight (88.9%) and nine (100%), respectively, of bone metastases. The detectability of thyroid cancer metastases using 99Tcm-tetrofosmin, 201Tl and 131I was 79.4%, 79.4% and 67.6%, respectively. The combined detectabilities of 99Tcm-tetrofosmin and 131I and of 201Tl and 131I were both 88.2%. 99Tcm-tetrofosmin and 201Tl imaging were found to be more sensitive than 131I for the detection of differentiated thyroid cancer metastases, particularly for regional lymph node. The combination of 99Tcm-tetrofosmin and 131I imaging may be a more sensitive and effective method for detecting metastases in differentiated thyroid cancer.     

Comparison of 99mTc-methoxyisobutyl isonitrile and 201Tl scintigraphy for detection of residual thyroid cancer after 131I ablative therapy.

In this study, we compared 99mTc-methoxyisobutyl isonitrile (MIBI) with 201Tl scintigraphy for the detection of residual thyroid cancer not found by 131I scans in patients with increased risk of recurrence after 131I therapy. METHODS: 201Tl and MIBI scans were obtained in 54 patients with negative 131I scans 3-25 y (median 7.9 y) after the first postsurgical 131I therapy. Serum thyroglobulin (Tg) levels were measured while patients were receiving thyroid hormone and again 6 wk after withdrawal of hormone therapy. RESULTS: The overall results were the same for both 201Tl and MIBI imaging, with a sensitivity of 19 of 36 (53%), specificity of 17 of 17 (100%) and accuracy of 36 of 54 (69%). Planar images missed residual cancer in high cervical lymph nodes adjacent to salivary gland activity, in small nodes (<1 cm) deep in the neck or chest and with diffuse pulmonary micrometastases. Serum Tg was elevated in 24 of 36 (67%) patients with residual cancer; 201Tl detected tumor sites in 13 of 24 (54%) of these patients, and MIBI detected tumor sites in 14 of 24 (58%) of these patients. Of the 12 patients who had residual cancer and false-negative serum Tg levels, 6 had true-positive 201Tl and 5 had true-positive MIBI scans. CONCLUSION: 201Tl and MIBI planar imaging yield the same high specificity and positive predictive value for residual thyroid cancer in patients with high-risk profiles and negative radioiodide scans. Both imaging agents detected residual cancer in more than half of the patients in whom conventional staging techniques did not reliably detect either the presence or the extent of residual thyroid cancer and changed the management in patients with surgically resectable cancer.     

Characteristics of the myocardial SPECT images of 99mTc-MIBI and 99mTc-teboroxime]

Characteristics of the myocardial distribution of 99mTc-MIBI and 99mTc-Teboroxime was compared with the myocardial distribution of 201Tl. We made summed myocardial images, in which central three short-axis SPECT slices were added. Rectangular region of interest (ROI) was set on each myocardial segment, and mean counts of each myocardial region was obtained using summed short-axis images. The ratio of inferior-to-anterior mean counts (I/A) was 0.69 +/- 0.20 in 99mTc-MIBI and 0.62 +/- 0.16 in 201Tl. The ratio of inferior-to-lateral mean counts was 0.70 +/- 0.18 and 0.65 +/- 0.13, respectively. Both ratios in 99mTc-MIBI were significantly higher than those in 201Tl (p less than 0.05). 201Tl to 99mTc-MIBI ratios of these two values were 1.11 +/- 0.17 (I/A) and 1.08 +/- 0.16 (I/L). The ratios of I/A and I/L of 99mTc-MIBI were about 10 percent higher than those of 201Tl. 99mTc-Teboroxime dynamic short-axis SPECT images of every three-minute were obtained. The ratios of counts in each wall were calculated similarly. After about 8 minutes, gradual increase in hepatic activity can be a cause of quantitative error in the assessment of SPECT images. We obtained the data with a human cardiac phantom. The myocardial phantom filled with 99mTc or 201Tl was placed in the mediastinal portion that is surrounded by the lung (saw dust) and vertebra (plastic bar). The ratio of I/A was 0.79 and I/L was 0.85 in 201Tl. The I/A ratio was 0.93 and I/L was 0.97 in 99mTc. Both ratios in 99mTc were about 15 percent higher than those in 201Tl.(ABSTRACT TRUNCATED AT 250 WORDS)     

Limited performance of quantitative assessment of myocardial function by thallium-201 gated myocardial single-photon emission tomography

We investigated the reproducibility between thallium-201 and technetium-99m methoxyisobutylisonitrile (MIBI) gated single-photon emission tomography (SPET) for the assessment of indices of myocardial function such as end-diastolic and end-systolic volume (EDV, ESV), ejection fraction (EF) and wall motion. Rest 201Tl (111 MBq) gated SPET was sequentially performed twice in 20 patients. Rest 201Tl gated SPET and rest 99mTc-MIBI (370 MBq) gated SPET were performed 24 h apart in 40 patients. Wall motion was graded using the surface display of the Cedars quantitative gated SPET (QGS) software. EDV, ESV and EF were also measured using the QGS software. The reproducibility of functional assessment on rest 201Tl gated SPET was compared with that on 99mTc-MIBI gated SPET, and also with that between 201Tl gated SPET and 99mTc-MIBI gated SPET performed on the next day. The two standard deviation (2 SD) values for EDV, ESV and EF on the Bland-Altman plot were 29 ml, 19 ml and 12%, respectively, on repeated 201Tl gated SPET, compared with 14 ml, 11 ml and 5.3% on repeated 99mTc-MIBI gated SPET. The correlations were good (r=0.96, 0.97 and 0.87) between the two measurements of EDV, ESV and EF on repeated rest studies with 201Tl and 99mTc-MIBI gated SPET. However, Bland-Altman analysis revealed that the 2 SD values between the two measurements were 31 ml, 23 ml and 12%. We were able to score the wall motion in all cases using the 3D surface display of the QGS on 201Tl gated SPET. The kappa value of the wall motion grade on the repeated 201Tl study was 0.35, while that of the wall motion grade on the repeated 99mTc-MIBI study was 0.76. The kappa value was 0.49 for grading of wall motion on repeated rest studies with 201Tl and 99mTc-MIBI. In conclusion, QGS helped determine EDV, ESV, EF and wall motion on 201Tl gated SPET. Because the EDV, ESV and EF were less reproducible on repeated 201Tl gated SPET or on 201Tl gated SPET and 99mTc-MIBI gated SPET on the next day than on repeated 99mTc-MIBI gated SPET, functional measurement on 201Tl gated SPET did not seem to be interchangeable with that on 99mTc-MIBI gated SPET.     

Comparison of 99mTc-hexakis 2-methoxy-2-isobutyl isonitrile and 201Tl SPECT imaging for evaluation of coronary artery disease

To evaluate clinical value of 99mTc-hexakis 2-methoxy-2-isobutyl isonitrile (MIBI) imaging for assessing coronary artery disease (CAD), 99mTc-MIBI SPECT imaging at post-exercise and at rest was compared with 201Tl SPECT imaging at post-exercise and 3 hours redistribution in 27 patients suspected with CAD. The sensitivities for detecting CAD patients were 94% (17/18) by both studies. The specificities were 71% (5/7) by 99mTc-MIBI and 57% (4/7) by 201Tl (p = NS). The sensitivities for detecting stenosed coronary arteries (greater than or equal to 75% stenosis) were also similar between 99mTc-MIBI (78%) and 201Tl (74%) (p = NS). The similar specificity values were obtained by 99mTc-MIBI (84%) and by 201Tl (82%) (p = NS). The patterns of abnormality (normal, ischemia and scar) were similar between 99mTc-MIBI and 201Tl images in 22 of the 25 cases (88%) and 117 of the 125 segments (94%). However, these patterns were occasionally different particularly in patients who received PTCA or CABG. Thus, 99mTc-MIBI SPECT imaging seems to be as accurate as 201Tl SPECT imaging for the detecting and evaluating CAD.     

Segmental analysis of SPECT 99mTc-methoxy isobutyl isonitrile and 201Tl myocardial imaging in ischaemic heart disease

To study the potential usefulness of 99mTc-methoxy isobutyl isonitrile (99mTc-MIBI) as a substitute for 201Tl in assessing patients with ischaemic heart disease, 24 patients underwent 1 day rest and exercise 99mTc-MIBI single photon emission computerised tomography (SPECT) 1 week after SPECT exercise 201Tl. All patients were catheterized within 1 month after myocardial imaging. In 17 patients, resting first pass radionuclide angiography (FPRNA) was performed with 99mTc-MIBI. The heart to lung ratio for 99mTc-MIBI and 201Tl was calculated both at rest and exercise. The segmental analysis for myocardial perfusion reveals that 87/96 segments (91%) were correctly classified by SPECT 201Tl and 84/96 segments (88%) were correctly classified by 99mTc-MIBI. A significant correlation was present between LVEF measured by 99mTc-MIBI FPRNA and contrast ventriculography (r = 0.85, P less than 0.0001). The heart to lung ratio both at rest and exercise for 99mTc-MIBI is significantly higher than 201Tl (P less than 0.01 and less than 0.001 respectively). We conclude that 99mTc-MIBI is a promising agent for simultaneous evaluation of myocardial perfusion and cardiac function.     

99mTc-MIBI (RP-30) to define the extent of myocardial ischemia and evaluate ventricular function

99mTc-MIBI, a new myocardial perfusion agent, is a technetium labeled isonitrile derivative. We have taken advantage of the physical characteristics of 99mTc to combine at rest, post infarction, ventricular function studies with analysis of perfusion. We have studied at rest and at stress, 22 patients with coronary artery disease selected on the basis of an abnormal coronary angiogram or on the basis of a positive exercise ECG stress test for symptomatic angina. We have also studied, at rest only, 20 patients with a previous myocardial infarction. A comparative thallium planar scintigraphy was obtained for all patients. The sensitivity of 99mTc-MIBI scintigraphy for detecting individual vessel lesions at stress was 88% as compared with 83% for 201Tl. Sensitivity was higher in patients with previous myocardial infarction (93% for the 2 isotopes) than in patients without (85% for 99mTc-MIBI versus 81% for 201Tl). Segmental myocardial correspondence between 99mTc-MIBI and 201Tl was very close (92%). The overall sensitivity for the detection of acute myocardial infarction reached respectively 91% for 99mTc MIBI and 87% for 201Tl. The specificity in the regions corresponding to arteries not involved was excellent for both tracers as we did not observe any false positive result. This is important information but it does not correspond to the specificity to detect coronary artery disease in the overall patient population. The correlation between first pass left ventricular ejection fraction obtained with 99mTc-MIBI and equilibrium left ventricular ejection fraction obtained with 99mTc red cells was excellent (r = 0.96). It was not as good but was still satisfactory for the right ventricle (r = 0.75).(ABSTRACT TRUNCATED AT 250 WORDS)     

Role of thallium-201 total-body scintigraphy in follow-up of thyroid carcinoma

To evaluate the reliability of total-body scintigraphy using [201Tl]chloride in postoperative follow-up of thyroid carcinoma, this procedure was performed in 326 patients after total thyroidectomy for thyroid carcinoma. The results were compared with those of 131I scintigraphy and thyroglobulin assays. 201Tl total-body scintigraphy was found to have the greatest sensitivity (94%), whereas 131I scintigraphy had the highest specificity (99%). It is shown that 201Tl total-body scintigraphy is a useful procedure in follow-up of thyroid cancer, however, the combination of parameters provides the greatest reliability. In medullary thyroid carcinoma, which is usually 131I negative, 201Tl total-body scintigraphy can be of great value for the localization of metastases which are indicated by elevated serum levels of calcitonin and carcinoembryonic antigen.     

99mTc-sestamibi and 131I whole-body scintigraphy and initial serum thyroglobulin in the management of differentiated thyroid carcinoma.

99mTc-sestamibi whole-body scanning has been used in the postoperative assessment of differentiated thyroid carcinoma together with 131I whole-body scanning and serum thyroglobulin (Tg) estimation. This study compared 99mTc-sestamibi whole-body scanning with 131I whole-body scanning in the context of initial serum Tg levels of patients after total or near-total thyroidectomy who were taken off thyroxine suppression therapy and who had no 131I ablation before surgery. METHODS: A prospective study of 360 patients was undertaken. 99mTc-sestamibi whole-body scintigraphy was performed at least 5 wk after thyroidectomy and was followed by 131I whole-body scanning. The patients had no thyroxine suppression for 5 wk, and Tg was measured thereafter. Radiologic studies (chest radiography, CT, MRI, sonography, and bone scanning) and histopathologic examinations were performed to clarify the presence of metastases with positive uptake on either 99mTc-sestamibi scans or 131I whole-body scans. Positive scans were defined as those with the presence of thyroid remnants, lymph node disease, or metastases. RESULTS: Two hundred fifty-nine (71.9%) of the 360 patients had initial serum Tg levels < 30 ng/mL (group 1), whereas 101 (28.1%) had initial serum Tg levels > or = 30 ng/mL (group 2). Of the 259 group 1 patients, 82 had positive 99mTc-sestamibi scans and 113 had positive 131I scans; 71.7% of patients with positive 1311 scans also had positive 99mTc-sestamibi scans, and 98.8% of patients with positive 99mTc-sestamibi scans also had positive 131I scans. Of the 101 group 2 patients, 81 had positive 99mTc-sestamibi scans and 97 had positive 131I scans; 83.5% of patients with positive 131I scans also had positive 99mTc-sestamibi scans, and all patients with positive 99mTc-sestamibi scans also had positive 131I scans. Of those with initial serum Tg levels > or = 30 ng/mL (group 2), 27.2% had thyroid remnants and 68.8% had lymph node disease or metastases. 131I scanning detects more thyroid remnants and lung metastases than does 99mTc-sestamibi scanning. CONCLUSION: Our findings suggest that, compared with 131I scanning, 99mTc-sestamibi scanning is less sensitive in detecting thyroid remnants and lung metastases but appears to be more useful in the detection of lymph node disease before initial 131I treatment.     

201Tl in the scintigraphic evaluation of the "cold" thyroid areas

201Tl-chloride, which has a metabolic behaviour similar to that of potassium and cesium, has been used in 68 patients for the evaluation of thyroid nodules previously recognized as "cold" on 131I or 99mTc scans. All patients were re-examined with gamma-camera and/or sequential scintigraphic recordings during 60 min after i.v. administration of thallium. In some cases, simultaneous imaging and integral digital plot with 131I or 99mTc and 201Tl were performed. In all 12 malignant nodules, 201 Tl has showed a high uptake, while it did not concentrate in 47 benign nodules (cystic or macrofollicular adenomas); thallium uptake was nevertheless found in 10 solid neoformations in which histological pictures were negative for malignancy or atypical lesions. The computerized study of the 201Tl intranodular concentration, with the analysis of its dynamic function curves, seems to offer further possibility in differentiating and in a more objective evaluation of the "cold" areas on the thyroid scan.     

201Tl, 99mTc-MIBI, 99mTc-tetrofosmin and 99mTc-furifosmin: relative retention and clearance kinetics in retrogradely perfused guinea pig hearts

Myocellular kinetics of 201Tl, 99mTc-MIBI, 99mTc-tetrofosmin and 99mTc-furifosmin were investigated using retrogradely-perfused guinea-pig hearts. Relative retention decreased in the order 99mTc-MIBI ==> 99mTc-tetrofosmin ==> 99mTc-furifosmin. 201Tl and 99mTc-MIBI exhibited bi- (t1,t2), 99mTc-tetrofosmin and 99mTc-furifosmin triexponential (t1,t2,t3) time-activity-curves. Latest-phase elimination-half-life increased from 201Tl (t2) ==> 99mTc-MIBI (t2) ==> 99mTc-tetrofosmin (t3) ==> 99mTc-furifosmin (t3), showing a significant increase in deteriorating myocardium for all tracers but 99mTc-furifosmin. Delayed elimination in deteriorating myocardium explains at least partly the redistribution phenomenon of 201Tl, and suggests a similar phenomenon for 99mTc-MIBI and 99mTc-tetrofosmin.     

European multi-centre comparison of thallium 201 and technetium 99m methoxyisobutylisonitrile in ischaemic heart disease

Fifty-six patients in Europe were entered into a multi-centre study to compare the accuracy of technetium 99m methoxyisobutylisonitrile (99mTc-MIBI) for the detection of coronary artery disease (CAD) with thallium 201 (201Tl) chloride perfusion scanning. The results showed a high degree of concordance between the two radiopharmaceuticals. Some 81% (678/840) of myocardial segments showed the same result (normal, infarct or ischaemia), and 80% (45/56) of patients had the same diagnosis. Overall detection of CAD in patients was 98% for 201T1 and 96% for 99mTc-MIBI. Detection of CAD in total arteries was 68% for both agents. In this study 99mTc-MIBI was as accurate as 201Tl for the detection of coronary artery stenoses.     

Comparison of (18)F-FDG, (131)I-Na, and (201)Tl in diagnosis of recurrent or metastatic thyroid carcinoma.

There are several reports about the usefulness of (18)F-FDG PET in thyroid cancer. However, few studies have compared FDG PET with (131)I and (201)Tl scintigraphy. The aim of this study was to evaluate the clinical significance of whole-body FDG PET in differentiated thyroid cancer and to compare the results with those obtained from (131)I and (201)Tl scintigraphy. METHODS: Whole-body FDG PET was performed on 32 patients (10 men, 22 women; age range, 30-77 y; mean age, 54 y) with differentiated thyroid cancer (5 cases of follicular cancer and 27 of papillary cancer) after total thyroidectomy. An overall clinical evaluation was performed, including cytology, thyroglobulin level, sonography, MRI, and CT, to allow a comparison with functional imaging results for each patient. Metastatic regions were divided into five areas: neck, lung, mediastinum, bone, and other. Multiple lesions in one area were defined as one lesion. The tumor-to-background ratio (TBR) was measured for the lesions that were positive for both (201)Tl uptake and FDG PET uptake. RESULTS: The number of lesions totaled 47. Forty-one (87%) were detected by all scintigraphic methods. FDG uptake was concordant with (131)I uptake in only 18 lesions (38%). FDG uptake was concordant with (201)Tl uptake in 44 lesions (94%). Only one lesion was negative for FDG uptake and positive for (201)Tl uptake, and two lesions were positive for FDG uptake and negative for (201)Tl uptake. A significant correlation was seen between the TBR of (201)Tl and that of FDG (r = 0.69; P<0.05). CONCLUSION: These data indicate that for detecting metastatic lesions, FDG PET and (131)I scintigraphy may provide complementary information, whereas FDG PET may provide results similar to those of (201)Tl scintigraphy. Thus, the combination of (131)I scintigraphy and FDG PET (or (201)Tl scintigraphy) is the method of choice for detecting metastatic thyroid cancer after total thyroidectomy.     

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 (²⁰¹T1) 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 papillaryfollicular, 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 underwent²⁰¹Tl and^99mTc-MIBI scintigraphy. Concomitant¹³¹I-Na scintigraphy was performed and serum thyroglobulin levels were measured. Sixteen scan sets were performed prior to¹³¹I-Na ablation therapy. Twenty-nine scan sets were performed following¹³¹I-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 of²⁰¹Tl 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 or²⁰¹Tl offered a higher diagnostic yield. Between the²⁰¹Tl 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 to²⁰¹Tl scintigraphy in thyroid carcinoma, especially following thyroidectomy and¹³¹I-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 or²⁰¹Tl is extremely valuable for tumor localization, especially when the¹³¹I-Na whole-body scan is negative. The combination of^99mTc-MIBI or²⁰¹Tl scintigraphy with¹³¹I-Na and serum thyroglobulin offers the highest diagnostic yield.This paper is based on a presentation at the 76th Annual Meeting of the American Radium Society, South Hampton, Bermuda, 22–26 April 1994.     

Routine 201Tl scintigraphy in the follow-up of patients with differentiated thyroid carcinoma: diagnostic accuracy and clinical impact

OBJECTIVE: The use of 201Tl scintigraphy as a routine imaging modality in the follow-up of patients with differentiated thyroid carcinoma (DTC) is controversial. The purpose of this retrospective study was to evaluate the diagnostic accuracy and clinical impact of routine 201Tl scintigraphy in the follow-up of patients with DTC. MATERIALS AND METHODS: Three hundred and twenty-one patients (261 women, 60 men) with DTC (243 papillary thyroid carcinomas, 78 follicular thyroid carcinomas) were enrolled in this study. Two hundred and seventy-six patients underwent total or near total thyroidectomy (group 1) and 45 patients underwent subtotal thyroidectomy or unilateral lobectomy (group 2). A total of 1523 201Tl scintigraphy examinations were performed between 1987 and 2003. The duration of follow-up ranged from 13 to 204 months. 201Tl scintigraphy was performed 10 and 60 min after intravenous administration of 74 MBq 201Tl chloride. RESULTS: In group 1, 55 recurrent lesions were confirmed in 39 patients. In a patient-based analysis, the sensitivity, specificity, positive and negative predictive values, and accuracy of 201Tl scintigraphy for detecting recurrent DTC were 71.8%, 98.3%, 87.5%, 95.5% and 94.6%, respectively. In a lesion-based analysis, the sensitivity, specificity, positive and negative predictive values, and accuracy of 201Tl scintigraphy were 63.6%, 99.7%, 89.7%, 98.5% and 98.3%, respectively. Of the 35 thallium-positive recurrent lesions, 21 (60%) were removed by surgery and seven (20%) were treated with external-beam radiation therapy. All the thallium-negative recurrent lesions were treated with 131I therapy. The difference between the management of thallium-positive and thallium-negative recurrences was statistically significant (P<0.001). In group 2, 10 recurrent lesions were confirmed in seven patients. In a patient-based analysis, the sensitivity, specificity, positive and negative predictive values, and accuracy of 201Tl scintigraphy for detecting recurrent DTC were 85.7%, 94.7%, 75%, 97.3% and 93.3%, respectively. In a lesion-based analysis, the sensitivity, specificity, positive and negative predictive values, and accuracy of 201Tl scintigraphy was 80%, 97.5%, 80%, 97.5% and 95.6%, respectively. All of the seven patients were treated with completion of total thyroidectomy and subsequent 131I ablation therapy. CONCLUSIONS: 201Tl scintigraphy was not a highly sensitive imaging modality in routine follow-up of patients with DTC after total thyroidectomy. However, it had a clinical impact on the choice of optimal therapeutic approaches. In the follow-up of patients who underwent partial thyroidectomy, 201Tl scintigraphy was useful in the detection of recurrent DTC.     

Uptake of myocardial imaging agents by rejecting and nonrejecting cardiac transplants. A comparative clinical study of thallium-201, technetium-99m, and gallium-67

To study the scintigraphic detectability of cardiac rejection, we performed 135 planar myocardial scans ([99mTc]pyrophosphate, 85; 201Tl, 36; 67Ga, 14) together with endomyocardial biopsies in ten patients for a (mean) 17-mo postoperative period. Specificity of each agent exceeded 89%. Technetium-99m pyrophosphate showed results that significantly correlated with the severity of rejection (p = 0.03), as shown by biopsy, but neither 201Tl nor 67Ga did so (p = 0.63 and 0.81, respectively). Technetium-99m pyrophosphate showed better diagnostic accuracy (85%) than 201Tl (69%) and 67Ga (64%). Technetium-99m pyrophosphate also showed higher negative predictive value (91%) than thallium (76%) and gallium (69%). Thus, a normal 99mTc pyrophosphate scan was usually associated with absence of cardiac rejection. However, all three agents showed unacceptably poor sensitivity (0% to 30%) and thus were not useful as a screening test for cardiac rejection, even when the same agent was used serially in imaging a given patient.     

The clinical impact of18F-FDG PET in papillary thyroid carcinoma with a negative131I whole body scan: A single-center study of 108 patients

OBJECTIVE: To assess whether FDG PET could localize the recurrent or metastatic lesions in papillary thyroid cancer patients with negative radioiodine scan. METHODS: Whole body PET was performed after injecting 370-555 MBq of 18F-FDG in 108 patients, who were suspected of having recurrence or metastasis and whose 131I whole body scans were negative. Recurrence or metastasis occurred in 63 patients by pathology or clinical assessment, whereas 45 patients remained in remission. RESULTS: FDG PET revealed recurrence or metastases in 59 patients (sensitivity 93.7%), whereas thyroglobulin (Tg) levels were elevated in 41 (sensitivity 65.1%). In 35 of 45 patients in remission, FDG PET was negative (specificity 77.8%). When patients positive for antithyroglobulin antibody were excluded, the sensitivity and specificity of serum Tg became 84.8% and 46.9%, respectively. Compared to Tg measurement, FDG PET detected more metastatic lesions in cervical lymph nodes. Of 40 patients with a negative radioiodine scan showing diffuse hepatic uptake, metastases occurred in 23 patients and remission in 17. FDG PET showed 100% sensitivity and 76.5% specificity in the detection of recurrence in these 40 patients. CONCLUSION: FDG PET is useful for localizing recurrent or metastatic lesions in 131I scan-negative thyroid cancer patients. In particular, it is superior to serum Tg measurement for identifying metastases to cervical lymph nodes. We recommend its use in cases of negative radioiodine scan with diffuse hepatic uptake.     

Influence of the thyroid remnant in the elevation of the serum thyroglobulin after thyroidectomy in differentiated thyroid carcinoma. Importance of the diagnostic iodine total-body scanning

PURPOSE: Stimulated thyroglobulin (Tg) and (131)I total-body scan (TBS) have been the mainstays of differentiated thyroid carcinoma (DTC), but now diagnostic TBS has been eliminated from some follow-up protocols. Nevertheless, Tg can be negative in the presence of thyroid tissue, and moderately elevated Tg poses management problems. The purpose of this study was to check how many patients have Tg negative but visible thyroid tissue and if diagnostic TBS could be clinically useful. MATERIAL AND METHODS: Retrospective review of 317 exams (stimulated Tg and TBS) of 128 patients with DTC. Patients with high-grade criteria and/or positive autoantibodies are excluded. Tg is considered positive if higher than the sensitivity level of the technique. TBS is positive if thyroid remnant, lymphatic node or metastases are detected. Results are classified in Tg and TBS concordant or discordant. RESULTS: Discordant (131)I TBS and Tg were found in 74/317 studies (23.3%), 48 (65%) being TBS positive and Tg negative. None of 128 patients had a first post-surgery negative scan, but 13 (10%) were Tg negative, even two patients with lymph node uptake. One year after radioiodine treatment, 26 out of 115 patients (initially Tg and TBS concordant positive) showed Tg negative and TBS still positive due to cervical remnants (20 patients), lymph node uptake (one) and metastasis (five); 20 patients remained Tg and TBS positive, but 14 of them only showed thyroid remnants. CONCLUSIONS: We propose to perform periodic diagnostic TBS to improve Tg specificity, at least while neck thyroid activity is detected, even if Tg is negative.