The rational use of201Tl scintigraphy in the evaluation of differentiated thyroid cancer

Fifteen patients with differentiated thyroid cancer were examined following¹³¹I thyroid ablation, of these seven were examined after radio-iodine therapy to disseminated neck cancer. They had no further radio-iodine uptake and were evaluated using a²⁰¹Tl scan. In thirteen patients there was a good correlation between the results and the clinical diagnosis, showing no uptake in seven subjects with negative clinical findings, and positive delineation of tumour tissue in the neck region in six patients. The remaining two patients with lymph node metastases after previous radio-iodine irradiation showed marked clinical regression of the metastases with absent uptake of both¹³¹I and²⁰¹Tl, probably due to radiation-induced changes. The comparison of thallium scans with plasma thyroglobulin levels showed certain differences (high plasma thyroglobulin without any proof of remaining thyroid tissue in one patient and normal/low plasma thyroglobulin in the presence of a tumour in two patients) but both measurements could give additional information. It is believed that while in the differential diagnosis of a thyroid nodule no important information could be expected of scanning (compared with the high value of aspiration biopsy), the evaluation of patients without¹³¹I uptake by²⁰¹Tl scans could provide important information for further therapy.     

The rational use of 201Tl scintigraphy in the evaluation of differentiated thyroid cancer

Fifteen patients with differentiated thyroid cancer were examined following 131I thyroid ablation, of these seven were examined after radio-iodine therapy to disseminated neck cancer. They had no further radio-iodine uptake and were evaluated using a 201Tl scan. In thirteen patients there was a good correlation between the results and the clinical diagnosis, showing no uptake in seven subjects with negative clinical findings, and positive delineation of tumour tissue in the neck region in six patients. The remaining two patients with lymph node metastases after previous radio-iodine irradiation showed marked clinical regression of the metastases with absent uptake of both 131I and 201Tl, probably due to radiation-induced changes. The comparison of thallium scans with plasma thyroglobulin levels showed certain differences (high plasma thyroglobulin without any proof of remaining thyroid tissue in one patient and normal/low plasma thyroglobulin in the presence of a tumour in two patients) but both measurements could give additional information. It is believed that while in the differential diagnosis of a thyroid nodule no important information could be expected of scanning (compared with the high value of aspiration biopsy), the evaluation of patients without 131I uptake by 201Tl scans could provide important information for further therapy.     

201Tl per-rectal scintigraphy in primary hepatocellular carcinoma

The results of 201Tl per-rectal scintigraphy in 10 patients with primary hepatocellular carcinoma (HCC) were presented together with the findings from contrast angiography, computed tomography and ultrasonography. 201Tl accumulation within the tumour was seen in seven of ten patients. This accumulation was thought to be due to 201Tl supply not from the portal vein but from the hepatic artery since significantly high heart to liver uptake (H/L) ratio from 0.71 to 1.21 and clear visualization of the heart and kidneys, indicating the presence of abundant portal-to-systemic shunting, were observed. Another three patients showed negative 201Tl accumulation within the tumour and near-normal H/L ratios from 0.32 to 0.47 which indicates little portal-to-systemic shunting. This finding reveals the evidence of the lack of 201Tl supply to the tumour from the portal vein. It seems that HCC does not receive any significant amount of blood flow from the portal system.     

Characterization of cartilaginous tumors with201Tl scintigraphy

Histological diagnosis and grading of cartilaginous tumors are closely correlated with patient prognosis; consequently, they are essential elements. We attempted to clarify the characteristics of 201Tl uptake in various histological types of cartilaginous tumors and to assess its clinical value. METHODS: Twenty-two cases with histologically proven cartilaginous tumors (3 enchondromas, 15 conventional chondrosarcomas (grade I = 9, II = 5, III = 1), 3 mesenchymal chondrosarcomas, and 1 de-differentiated chondrosarcoma) were examined retrospectively. Planar 201Tl images were recorded 15 min following intravenous injection of 201Tl (111 MBq). 201Tl uptake in the tumor was evaluated visually employing a five-grade scoring system: 0 = no appreciable uptake, 1 = faint uptake above the background level, 2 = moderate uptake, 3 = intense uptake but lower than heart uptake and 4 = uptake higher than heart uptake. RESULTS: 201Tl uptake scores were 0 in 3 of 3 enchondromas, 9 of 9 grade I, and 4 of 5 grade II conventional chondrosarcomas. 201Tl uptake scores were 1 among 1 of 5 grades II and a grade III conventional chondrosarcoma. Mesenchymal chondrosarcoma and de-differentiated chondrosarcoma displayed 201Tl uptake scores of 2 or 3. CONCLUSIONS: Absence of elevated 201Tl uptake in cartilaginous tumors was indicative of enchondroma or low-grade conventional chondrosarcoma. However, in instances in which 201Tl uptake is obvious, high-grade chondrosarcoma or variant types should be considered.     

Differentiation of soft tissue haemangioma by 201Tl scintigraphy

Radiological diagnosis of deep soft tissue is often difficult. In the present study, thallium-201 ( Tl) uptake into haemangiomas and deep malignant soft tissue tumours was investigated in order to assess its clinical utility. Tl scintigraphy was reviewed in four patients presenting with soft tissue haemangiomas. Early and delayed planar images, obtained at 15 min and 3 h following the intravenous injection of Tl (111 MBq), were examined. The Tl uptake ratio was calculated by dividing the count density of the tumour region of interest (ROI) by that of the background ROI. Results were compared with those of five cases of rhabdomyosarcoma and a single instance of angiosarcoma. All haemangioma lesions demonstrated increased Tl uptake in early images. However, Tl uptake in delayed images was markedly decreased. No significant differences were observed in the early uptake ratio between haemangiomas (1.60-2.72) and reference malignant tumours (1.48-2.45); however, the difference was significant in delayed images (range, 1.01-1.26 vs. 1.43-2.03, respectively) ( P<0.02). Deep soft tissue haemangiomas revealed Tl accumulation in early images; however, a rapid washout was observed in delayed images. This distinctive feature may facilitate the use of Tl scintigraphy in the diagnosis of haemangiomas.     

Multiple myeloma evaluated with 201Tl scintigraphy compared with bone scintigraphy.

The purpose of this study was to investigate the clinical usefulness of 201Tl chloride scintigraphy in the diagnostic evaluation of 20 patients with multiple myeloma (19/20 patients) or extramedullary plasmacytoma (1/20 patients) in comparison with bone scintigraphy. METHODS: Both 201Tl and bone scintigraphy were performed to obtain planar images on the same instrument. RESULTS: 201Tl scintigraphy showed increased uptake in 15 of 20 patients (75%) and was negative in 5 of 20 patients (25%). In addition, 201Tl scintigraphy of multiple myeloma was more useful in detecting the lesions in 11 of 17 patients and less useful in 6 of 17 patients than bone scintigraphy. CONCLUSION: The combination of 201Tl and bone scintigraphy, compared with bone scintigraphy alone, shows promise in more accurately diagnosing multiple myeloma.     

Relationship between cancer cell proliferation, tumour angiogenesis and 201Tl uptake in non-small cell lung cancer

PURPOSE: To investigate whether 201Tl uptake is associated with cell proliferation and angiogenesis in non-small-cell lung carcinoma (NSCLC). METHODS: Eighty-four patients with scheduled NSCLC underwent 201Tl single photon emission computed tomography (SPECT) imaging: 15 min (early scan) and 240 min (delayed scan) after intravenous injection of 111 MBq of 201Tl chloride. 201Tl indices were calculated on early images (early ratio: ER) and delayed images (delayed ratio: DR). The retention index (RI) was also calculated from these two parameters. Using surgically resected cancer specimens (54 adenocarcinoma, 24 squamous cell carcinoma (SCC), six large-cell carcinoma), immunohistochemical stains for both Ki-67 (MIB-1 index) and CD34 were performed to examine the proliferative activity and the micro-vessel density (MVD), respectively. RESULTS: The mean value of 201Tl index was 1.69+/-0.77 (ER) and 2.31+/-1.08 (DR). The average RI was 42.6+/-42.9%, respectively. Both DR and RI positively correlated with MIB-1 index (r = 0.68, P < 0.05 and r = 0.52, P < 0.05). When we analyse adenocarcinoma and SCC separately, there was a significant positive correlation (r = 0.62, P < 0.05) between RI and MIB-1 index in adenocarcinoma but not in SCC (r = 0.20, P = NS). The value of ER positively correlated with MVD (r = 0.75, P < 0.05). It demonstrated strong positive correlation with both histological types (adenocarcinoma: r = 0.80, P < 0.05, SCC: r = 0.66, P < 0.05). CONCLUSION: 201Tl SPECT imaging is effective non-invasive method for assessing both the proliferation and the angiogenesis in NSCLC. Both DR and RI are useful indicators for assessing cancer cell proliferation in lung adenocarcinoma. ER is a useful marker for assessing the tumour angiogenesis in NSCLC.     

A quantitative assessment of scintigraphy of the legs using 201Tl

²⁰¹Tl perfusion scintigraphy of the legs was evaluated to define intermittent claudication quantitatively, based on Sapirstein's indicator fractionation principle. After intravenous injection of ²⁰¹Tl with or without exercise, the distribution of the radiotracer throughout the body was obtained using the whole body scanner. Regional blood flow of cardiac output for three segments of the leg was estimated as a regional fractional uptake (rFU) distributed in these segments compared with the whole body distribution. The validity of the principle was confirmed by a comparative study with ^99mTc-MAA (r=0.979). Normal rFUs (%) for each section at rest and after stress, respectively, were 5.49±0.69 and 19.40±2.04 (whole leg); 3.57±0.49 and 12.26±1.91 (thigh); 1.59±0.34 and 6.58±0.61 (calf). The rates of rFU change from the state of rest to stress (rFU) in normals were 3.41±0.45 (whole leg), 3.44±0.61 (thigh), and 4.30±1.03 (calf). Although rFU was within normal limits in patients with arteriosclerosis obliterans (ASO) and thromboangitis obliterans (TAO), rFU of the whole leg was significantly decreased from the normal value of 3.41±0.45 to 1.95±0.40 for ASO (P(0.001) and 1.82±0.47 for TAO (P(0.001). A defect or decreased activity on the stress scintigraph was well correlated with the angiographic findings.     

A quantitative assessment of scintigraphy of the legs using 201Tl

201Tl perfusion scintigraphy of the legs was evaluated to define intermittent claudication quantitatively, based on Sapirstein's indicator fractionation principle. After intravenous injection of 201Tl with or without exercise, the distribution of the radiotracer throughout the body was obtained using the whole blood scanner. Regional blood flow of cardiac output for three segments of the leg was estimated as a regional fractional uptake (rFU) distributed in these segments compared with the whole body distribution. The validity of the principle was confirmed by a comparative study with 99mTc-MAA (r = 0.979). Normal rFUs (%) for each section at rest and after stress, respectively, were 5.49 +/- 0.69 and 19.40 +/- 2.04 (whole leg); 3.57 +/- 0.49 and 12.26 +/- 1.91 (thigh); 1.59 +/- 0.34 and 6.58 +/- 0.61 (calf). The rates of rFU change from the state of rest to stress (delta rFU) in normals were 3.41 +/- 0.45 (whole leg), 3.44 +/- 0.61 (thigh), and 4.30 +/- 1.03 (calf). Although rFU was within normal limits in patients with arteriosclerosis obliterans (ASO) and thromboangitis obliterans (TAO), delta rFU of the whole leg was significantly decreased from the normal value of 3.41 +/- 0.45 to 1.95 +/- 0.40 for ASO (P less than 0.001) and 1.82 +/- 0.47 for TAO (P less than 0.001). A defect or decreased activity on the stress scintigraph was well correlated with the angiographic findings.     

201Tl SPECT in the detection of mediastinal lymph node metastases from lung cancer

201Tl SPECT was performed to detect mediastinal involvement in 80 patients with lung cancer who underwent surgery within a week after the SPECT study. Out of 29 patients with mediastinal involvement 16 (55%) were positive on the 201Tl early scan at 15 min postinjection and 22 (76%) were positive on the delayed scan at 3 h. These metastatic lymph nodes tended to be visualized much better on the delayed scan. In all patients with true positive results on the delayed scan, the mediastinal lymph nodes were plural, with a lesion of more than 14 mm in size. Seven false negative cases were found to have metastatic lesions less than 12 mm in size. Both the early and delayed scans showed false positive accumulation in six of 51 patients without mediastinal involvement (specificity 88%). Thus the overall accuracy for the delayed scan was 84%. The 201Tl delayed SPECT is thought to be a good noninvasive method for assessing mediastinal lymph node metastases from lung cancer.     

Whole-body scintigraphy in melanoma patients: comparison of 99Tcm-tetrofosmin and 201Tl

The aim of this study was to determine the diagnostic value of 99Tcm-tetrofosmin whole-body imaging in comparison to 201Tl scintigraphy in patients with metastatic melanoma. In 27 patients with known or suspected melanoma metastases we performed 201Tl scintigraphy and 99Tcm-tetrofosmin scintigraphy using a 1-day protocol. In five patients with known locoregional metastasis the in vivo uptake kinetics of both radiotracers were compared. The final diagnosis was confirmed by surgical histology in 39 lesions (group I) and computed tomography (CT) and clinical course in 14 lesions (group II). In group I, containing mainly locoregional metastases, 201Tl scintigraphy correctly identified 36 of 39 metastases and 99Tcm-tetrofosmin 35 of 39 resulting in a sensitivity of 92% and 90% respectively. The T/B ratios of 201Tl (1.4-4.0, mean 2.15) were statistically significantly higher in comparison to tetrofosmin (1.3-3.0, mean 1.88). However, both radiotracers showed similar uptake and washout kinetics with a maximum of tracer uptake between 1 and 5 min p.i. In group II, containing mainly cerebral and pulmonary metastases, both methods correctly identified six of 14 metastases resulting in a sensitivity of only 43%. We conclude that the uptake of 99Tcm-tetrofosmin and 201Tl in melanoma metastases is very similar. The T/B ratios with 99Tcm-tetrofosmin are significantly lower than with 201Tl. In locoregional melanoma metastases the sensitivity of tetrofosmin scintigraphy is identical with 201Tl imaging and amounts to 90%. In cerebral and lung metastases the sensitivity of both methods is limited when using whole-body scintigraphy.     

Examination of retention index in brain tumor 201Tl scintigraphy using iNRT

The retention index (R.I.) in Thalliun-201-chloride (201Tl-Cl) brain tumor single photon emission computed tomography (SPECT) imaging analysis is useful in assessing grades of malignancy. When the T/N ratio that influences the R.I. is calculated, it is ideal to draw an ROI on the same slices and coordinates of both early and delayed transaxial images. However, in many institutions, the image slice and ROI are determined manually by operators (i.e., by the conventional method). The Co-registration function within iNRT software enables an ROI to be automatically drawn. In this study, we obtained the R.I. from six brain tumor patients employing two different methods (i.e., Co-registration and the conventional method). Each R.I. was obtained from the same personal computer that was used to transfer the transaxial images. We then compared and evaluated the six R.I. values of seven operators. (2 radiologists and 5 radiological technologists). The results showed that the R.I. values did not differ significantly between the two methods, except in two cases. Furthermore, the coefficient of variation (CV) of the R.I. obtained from the Co-registration method was lower than the conventional method in all cases. The variations among operators were also smaller in the Co-registration method. These outcomes may have been due to the fact that in the conventional method it is difficult to identify the same slices of early and delayed images. Therefore, there were differences among operators in their ways of specifying positions of the ROI. This may have resulted in differences in the number of counts/pixel of the ROI. In conclusion, the R.I. obtained by using the Co-registration method would be more useful for improving diagnostic accuracy in (201)Tl-Cl brain tumor SPECT imaging than the conventional method.     

Evaluation of bedside myocardial scintigraphy with 201Tl in acute myocardial infarction

Bedside myocardial scintigraphy was performed on 149 patients admitted to the Coronary Care Unit (CCU), after IV injection of 74 MBq ²⁰¹Tl, using a mobile gamma camera (Dynamo). The study was displayed on Polaroïd pictures, without any image treatment, and read by two independent readers. Clinical history, findings, and final diagnosis were assessed by an independent clinician. The following conclusions were reached:

1. The sensitivity of the study for the detection of a recent myocardial infarction (MI) was 0.84 with a specificity of 0.87.
2. There was a good correlation between scintigraphic and ECG localization.
3. No firm correlation was found between scintigraphic and enzymatic estimates of infarct size.
4. Abnormal visualization of the right ventricle was probably associated with more extensive infarction.

     

The role of201Tl scintigraphy in evaluating proliferative activity in thyroid neoplasms

To identify the relationship between the uptake of²⁰¹Tl and the proliferative activity in thyroid neoplasms,²⁰¹Tl scintigraphy was performed in 57 patients with thyroid neoplasms.²⁰¹Tl uptake ratio was calculated in both the early and the delayed images and then compared with factors representing cellular or practical proliferative activity of the lesions. The labeling index (LI) for proliferating cell nuclear antigen (PCNA) was determined quantitatively by flow cytometry. There was a significant correlation between the uptake ratio and LI for PCNA. The correlation coefficient for the delayed ratio (DR) vs. LI was better than that for the early ratio (ER) vs. LI. As parameters for practical proliferation, the surgical stage in primary thyroid carcinoma or¹³¹I uptake in recurrent thyroid carcinoma was focused on. DR was strongly related to these parameters, regardless of the histopathological features or size of the lesions. Our results suggest that²⁰¹Tl uptake in delayed thyroid scan is useful in assessing proliferative activity in thyroid neoplasms.