The optimum time for tumour imaging with thallium-201

Following the intravenous injection of 75 MBq ²⁰¹Tl-chloride we have assessed the uptake kinetics in the myocardium and in the primary tumour in 56 patients with lung cancer, 26 with breast cancer and 13 with mediastinal lymphoma. The time of maximal tumour uptake ranged from 8–20 min post-injection and did not differ significantly between lung cancer (mean±SD=11.9±3.34 min), breast cancer (11.21±1.88 min) and lymphoma (11.76±3.25 min). The time of maximum cardiac uptake of ²⁰¹Tl was 11.61±3.25 min. There was no significant washout of ²⁰¹Tl from the tumours in the first hour after injection in the various malignant lesions studied. The time of maximal tumour to background activity was 18.3±0.59 min for lung cancer, 13.0±1.16 min for breast cancer and 16.7±1.04 min for lymphoma.The time course of ²⁰¹Tl uptake in the tumours suggests that the mechanism of uptake is similar to that in the myocardium. The optimal time of ²⁰¹Tl tumour imaging is from 20–60 min following injection and did not differ in various tumours studied.     

Mechanism of 201Tl uptake in tumours

We have studied the mechanism of tumour uptake of 201Tl by in vivo and in vitro studies. In a series of patients with breast cancer (n = 26), lung cancer (n = 56) and lymphoma (n = 15), the time course of tumour uptake of 201Tl paralleled that in the myocardium with almost identical times of peak uptake being obtained in tumours and myocardium. In a patient with hepatic metastases from colonic cancer undergoing laparotomy, 99mTc labelled microspheres and 201Tl were injected into the hepatic artery and biopsies of metastatic and normal liver tissue obtained. The tumour to normal liver activity ratios for 201Tl were one tenth of those for 99mTc microspheres. In the final part of the study, cells from a lung cancer tissue culture line were incubated for 30 min with 201Tl with and without the addition of cardiac glycoside, which acts a sodium potassium pump blocker. The cells exposed to the cardiac glycoside showed markedly decreased uptake of 201Tl compared to the cells not so exposed (0.6% +/- 0.1% vs 11.8 +/- 0.7.2% of the administered dose). The mechanism of 201Tl uptake of tumours is similar to that in the myocardium. Sodium potassium pump activity appears to be more important than tumour blood flow. 201Tl uptake may provide a useful means of studying tumour viability.     

Mechanism of 201Tl uptake in tumours

We have studied the mechanism of tumour uptake of ²⁰¹Tl by in vivo and in vitro studies. In a series of patients with breast cancer (n=26), lung cancer (n=56) and lymphoma (n=15), the time course of tumour uptake of ²⁰¹Tl paralleled that in the myocardium with almost identical times of peak uptake being obtained in tumours and myocardium. In a patient with hepatic metastases from colonic cancer undergoing laparotomy, ^99mTc labelled microspheres and ²⁰¹Tl were injected into the hepatic artery and biopsies of metastatic and normal liver tissue obtained. The tumour to normal liver activity ratios for ²⁰¹Tl were one tenth of those for ^99mTc microspheres. In the final part of the study, cells from a lung cancer tissue culture line were incubated for 30 min with ²⁰¹Tl with and without the addition of cardiac glycoside, which acts a sodium potassium pump blocker. The cells exposed to the cardiac glycoside showed markedly decreased uptake of ²⁰¹Tl compared to the cells not so exposed (0.6%±0.1% vs 11.8±0.7.2% of the administered dose). The mechanism of ²⁰¹Tl uptake of tumours is similar to that in the myocardium. Sodium potassium pump activity appears to be more important than tumour blood flow. ²⁰¹Tl uptake may provide a useful means of studying tumour viability.     

201Tl scintigraphy in the staging of lung cancer, breast cancer and lymphoma

To evaluate 201Tl in the detection of the primary tumour, lymph node involvement and mediastinal spread we have studied a total of 188 patients with histologically proven lung cancer, breast cancer or malignant lymphoma. Ten patients with benign lung disease were also examined. Static images were performed 20 min after intravenous injection of 75 MBq of thallous (201Tl) chloride. The results were compared with those of standard staging procedures including CT scanning and mediastinal exploration. Thallium-201 imaging was highly sensitive in detecting the primary tumour (lung cancer 86%, breast carcinoma 100%, lymphoma 85%), but showed low sensitivity in detecting mediastinal spread or lymph node involvement. Thallium-201 uptake was also observed in active sarcoidosis (one case) and active TB (two cases). We conclude that 201Tl imaging is unlikely to have a clinically useful role in the diagnosis or staging of lung cancer, breast cancer or lymphoma.     

Initial application of respiratory-gated 201Tl SPECT in pulmonary malignant tumours

AIM: Respiratory-gated thallium-201 chloride (201Tl) single photon emission computed tomography (SPECT) was used in preliminary investigations to reduce the adverse respiratory motion effects observed on standard ungated SPECT images and to obtain reliable fusion images with computed tomography (CT) in patients with malignant lung tumours. METHODS: Fifteen patients with primary lung cancer (n=10) or metastatic lung tumours (n=5) underwent gated SPECT 20 min after intravenous injection of 148 MBq 201Tl, using triple-headed SPECT and laser light respiratory tracking units. Projection data were acquired by a step and shoot mode, with 20 stops over 120 degrees for each detector and a preset time of 30 s for each 6 degrees stop. Gated end-inspiratory and ungated images were obtained from 1/8 data centred at peak inspiration for each regular respiratory cycle and for the full respiratory cycle data, respectively. The degree and size of tumour 201Tl uptake were compared between these images by regions of interest (ROI) analysis. Gated SPECT images were registered with rest inspiratory CT images using an automated three-dimensional (3D) image registration tool. Registration mismatch was assessed by measuring the 3D distance of the centroid of 14 201Tl-avid peripheral tumours. Attenuation correction of gated SPECT images was performed using CT attenuation values of these fusion images. RESULTS: Gated SPECT images improved image clarity and contrast of tumour 201Tl uptakes compared with ungated images, regardless of the decreased count density due to the use of gated images. The lesion-to-normal (L/N) lung count ratios and ROI size in 18 well-circumscribed 201Tl-avid tumours were significantly higher and smaller on gated images (both P<0.0001). Gated images showed positive 201Tl uptakes in two small peripheral tumours, although negative on ungated images, and demarcated 201Tl-avid tumours from adjacent 201Tl-avid lymph node or surrounding focal 201Tl uptakes caused by other pathology, although these were not clearly demarcated on ungated images. On fusion images, gated images yielded a significantly better SPECT-CT matching compared with ungated images (P<0.0001). Fusion images accurately localized 201Tl uptakes of tumour/lymph node and other focal pathological/physiological conditions. Attenuation-corrected gated SPECT images further facilitated the detection of 201Tl uptake in small or deeply located lesions, with significantly increased L/N ratios. CONCLUSION: Gated SPECT images facilitate the detection of tumour 201Tl uptake and provide reliable SPECT-CT fusion images, which contribute to accurate interpretation and attenuation correction of Tl SPECT images.     

Evaluation of radiotherapeutic response in non-small cell lung cancer patients by technetium-99m MIBT and thallium-201 chloride SPET

The purpose of this study was to investigate the relationship between technetium-99m hexakis-2-methoxyisobutylisonitrile (99mTc-MIBI) accumulation in tumours and response to radiotherapy in non-small cell lung cancer patients in comparison with the findings obtained using thallium-201 chloride (201Tl). Simultaneous dual single-photon emission tomography (SPET) imaging with 600 MBq 99mTc-MIBI and 111 MBq 201Tl was performed in 31 patients with biopsy- or sputum cytology-proven lung cancer. SPET images were acquired 15 min (early) and 2 h (delayed) after injection, and the early ratio, delayed ratio and retention index were measured. The tumours were classified into two groups on the basis of follow-up computed tomography (CT): responders (at least 50% reduction in tumour size) and non-responders (little or no change in tumour size). The mean (+/-SD) values of early ratio, delayed ratio and retention index using 99mTc-MIBI SPET were 3.0+/-1.1, 2.7+/-1.0 and -9.5+/-12.7, respectively, in responders and 2.4+/-0.7, 2.0+/-0.5 and -18.4+/-9.0, respectively, in non-responders. The corresponding values using 201Tl chloride SPET were 3.7+/-1.0, 4.7+/-1.5 and 24.2+/-22.1 in responders and 3.3+/-1.2, 4.0+/-1.3 and 20.4+/-20.5 in nonresponders. Using 99mTc-MIBI, the delayed ratio and retention index in responders were significantly higher than those in non-responders (P<0.01 and P<0.05, respectively). The results of this study indicate that patients with higher delayed ratio and retention index values using 99mTc-MIBI SPET are likely to respond better to radiotherapy than those with lower values. 99mTc-MIBI SPET may give an indication of the short-term response to radiotherapy in patients with non-small cell lung cancer.     

Early dynamic 201Tl SPECT in the evaluation of brain tumours

OBJECTIVE: To estimate the usefulness of early dynamic 201Tl single photon emission computed tomography (SPECT) studies in distinguishing the histological malignancy of brain tumours. METHODS: Dynamic 201Tl SPECT was performed for 3 min per scan for 15 min immediately after the administration of 201TlCl in 110 patients with brain tumours (111 lesions). The data obtained each 3 min were used for dynamic SPECT, and the five sets of data obtained were added to acquire static SPECT data. For static SPECT, the static thallium index (STI) was calculated as the ratio of 201Tl uptake in the tumour to that of the contralateral normal brain. The ratio of the 201Tl uptake for each 3 min was defined as the dynamic thallium index (DTI). The dynamic thallium rate (DTR), as a per cent, was calculated as DTR=(DTI for every 3 min)/STI H 100. The five values were approximated as a linear function and the slope (%/min) was calculated. RESULTS: In static SPECT, there was no significant difference between the STI of malignant tumours (glioblastoma and anaplastic astrocytoma) and that of benign tumours (low-grade glioma, meningioma, pituitary adenoma, neurinoma and haemangioblastoma) (3.7+/-1.5, 5.0+/-3.5, respectively). On dynamic SPECT, DTI increased markedly over 15 min for malignant tumours. In contrast, the DTI of benign tumours increased slightly, steadily or decreased. The slope of the linear functions calculated from the DTRs was much higher in the malignant tumour group than in the benign tumour group (P<0.001). CONCLUSIONS: We suggest that the performance of 201Tl dynamic SPECT for 15 min is useful for distinguishing malignant brain tumours from benign brain tumours and reduces the examination stress of patients.     

Comparison of 99Tcm-MIBI with 201Tl chloride SPET in patients with malignant brain tumours

The purpose of this study was to evaluate the usefulness of 99Tcm-MIBI accumulation for the differentiation of histological diagnosis of malignant brain tumours in comparison with the findings obtained using 201Tl chloride. A total of 25 patients with malignant brain tumours were investigated. The histological categories of tumours included glioblastoma multiforme (n = 5), anaplastic astrocytoma (n = 4), malignant lymphoma (n = 5), and metastatic tumour (n = 11). Simultaneous dual single photon emission tomography (SPET) images with 99Tcm-MIBI and 201Tl were acquired 15 min (early) and 2 h (delayed) after injection, and the early ratio, delayed ratio and retention index were measured. The new indices 201Tl/99Tcm-MIBI ratios and 201Tl/99Tcm-MIBI retention index were also calculated. With respect to the histological type, a higher retention index using 99Tcm-MIBI was noted in glioblastoma multiforme compared with metastatic tumour. Higher values of both ratios using 201Tl were noted in glioblastoma multiforme compared to metastatic tumour. The value of the delayed ratio obtained using 201Tl was higher in glioblastoma multiforme than in anaplastic astrocytoma, and the value was also higher in malignant lymphoma than in metastatic tumour. The 201Tl/99Tcm-MIBI early ratio of glioblastoma multiforme was significantly higher than that of metastatic brain tumour. The 201Tl/99Tcm-MIBI retention index of malignant lymphoma was significantly higher than that of glioblastoma multiforme. In the histological type of tumour, 99Tcm-MIBI is not superior to 201Tl, but the combined indices using 201Tl/99Tcm-MIBI may add new information about differential diagnosis.     

Correlation of thallium-201 uptake with proliferating cell nuclear antigen in brain tumours

The aim of this study was to assess the correlation between thallium-201 (201Tl) uptake and proliferative activity measured using the proliferating cell nuclear antigen labelling index (PCNA-LI) in brain tumours. Twenty-nine patients with brain tumours were included in this study. Of these, seven were diagnosed with meningioma, 13 had high grade glioma (HGG) and nine had low grade glioma (LGG). A 210Tl single photon emission computed tomography study was performed on all patients before operation, and 201Tl uptake index (UI) and retention index (RI) values were calculated. Cell proliferation was determined by PCNA. While all of the HGGs and meningiomas showed intense 201Tl accumulation on visual interpretation, eight of the nine LGGs did not show accumulation of 210Tl at the tumour site. 201Tl UI values were 3.23+/-0.89 and 2.67+/-0.66 in HGG, 1.27+/-0.18 and 1.23+/-0.09 in LGG, and 4.35+/-1.60 and 2.52+/-0.78 in meningioma on early and delay images, respectively. There was a statistical difference between the 201Tl UI in HGG and LGG. PCNA-LI values were 16.72+/-6.15%, 1.63+/-0.81% and 2.00+/-1.88% in HGG, LGG and meningioma, respectively. The PCNA-LI in HGG was significantly higher than in LGG and meningioma. While the correlation coefficient between the 201Tl UI and the PCNA-LI was 0.94 in gliomas (n=22), there was no correlation in meningiomas. No statistically significant correlation was found between the RI and the PCNA-LI in gliomas. The presence of a strong positive correlation between 201Tl uptake and PCNA-LI indicates that 201Tl uptake can predict the proliferative activity of the glioma.     

Technetium-99m-tetrofosmin uptake in malignant lung tumours

Technetium-99m-tetrofosmin is a new myocardial imaging agent which has yielded promising results compared to thallium-201. The tumour-seeking properties of the routinely used cardiac radiopharmaceuticals²⁰¹Tl and^99mTc-methoxyisobutylisonitrile are well known. Here we report the results of a pilot study demonstrating^99mTc-tetrofosmin uptake in malignant lung tumours. Five patients with bronchial carcinoma, each in different stages of chemo- or radiotherapy, were imaged. Dynamic and static acquisitions were performed to evaluate the uptake and kinetics of^99mTc-tetrofosmin in the lesions. In four of the five patients localized tumour uptake of^99mTc-tetrofosmin was observed. Time to peak tumour activity and tracer washout in the tumour, myocardium and contralateral normal lung at 30 min post injection (p.i.) were determined. Tumour/normal lung, heart/tumour and heart/contralateral normal lung ratios were calculated for 5–10, 25–30 and 85–90 min p.i. The peak concentration in all tumours was reached at the end of the first minute. The mean tumour and contralateral normal lung washout rates of^99mTc-tetrofosmin at 30 min p.i. were 18.3%±9.2% and 19.5%±5.85% respectively. The tumour/contralateral normal lung ratio remained higher than 1.25 until 90 min p.i. in all four patients. It is concluded that^99mTc-tetrofosmin seems to be of value in lung tumour imaging, although larger studies are necessary to ascertain its sensitivity, specificity and usefulness in clinical practice.     

The use of thallium-201 in the preoperative detection of breast cancer: an adjunct to mammography and ultrasonography

Thallium-201 breast scans were performed preoperatively in 72 female patients with breast abnormalities detected by mammography and/or ultrasonography (7.5–13 MHz), in order to differentiate benign from malignant breast disease. Informed consent was obtained from each patient. Scintigraphy consisted of anterior and oblique planar images of the affected breast and axilla at 10 min and 3 h following the injection of²⁰¹Tl chloride (110 MBq). All²⁰¹Tl scans were interpreted without prior knowledge of surgery data. Pathological features of breast malignancies, such as tumour size, axillary lymph node metastases, tumour grading, lymphatic vascular channel invasion and receptor status, were analysed for their association with²⁰¹Tl uptake by tumour cells. A total of 76 breast lesions were assessed in the study. On final histological diagnosis, there were 56 malignant tumours, 14 benign nodules (9 fibroadenomas, two cases of adenosis, two cases of focal fibrosis and one case of epitheliosis) and six atypical lesions (atypical ductal or lobular hyperplasia). Thallium scintigraphy was shown to have high accuracy (92%) in detecting breast cancer, better than mammography (74%) and ultrasonography (84%). Almost all (51/56) breast cancers showed greater²⁰¹Tl activity than surrounding normal breast tissue while there was no significant increase in²⁰¹Tl activity above background in all but one (19/20) case of non-malignant disease.²⁰¹Tl activity within breast tumours, calculated as tumour/background (T/B) ratio, ranged between 1.2 and 2.5 with a mean value of 1.45. In our experience the concentration of thallium in the breast cancer seems to be primarily dependent on vascularity and tumour size rather than tumour grading, lymphatic/vascular invasion or receptor status.²⁰¹Tl scan sensitivity was 97% for malignant lesions larger than 1.5 cm (n=35) and 80% for lesions of 1.5 cm or less (n=21); however, five of the eight breast cancers smaller than 1.0 cm were also detectable by²⁰¹Tl scintigraphy, compared with five out of seven by mammography. Thallium scintigraphy would not be useful in evaluating the axilla for lymph node metastases (sensitivity 27%, specificity 77%).     

The effect of nitroglycerin on myocardial blood flow in various segments characterized by rest-redistribution thallium SPECT.

The use of nitrates is reported to be effective in viability detection in scintigraphic perfusion imaging. The purpose of the study was to evaluate the effect of nitroglycerin (NTG) on myocardial blood flow (MBF) and coronary vascular resistance (CVR) in various segments characterized by rest-redistribution (201)Tl SPECT. METHODS: Twenty-three patients with coronary artery disease underwent rest-redistribution (201)Tl SPECT and (15)O-labeled water PET at rest and after NTG spray (0.3 mg). In addition, 11 healthy volunteers were also studied using PET. RESULTS: NTG did not change global MBF in the volunteers or in the patients. In segments with normal (201)Tl uptake and in those with a severe irreversible (201)Tl defect, NTG significantly reduced MBF without changing CVR. NTG reduced CVR in segments with a reversible (201)Tl defect (141 +/- 50 to 114 +/- 29 mm Hg/[mL/min/g], P = 0.004) and in those with a mild-to-moderate irreversible (201)Tl defect (165 +/- 64 to 149 +/- 60 mm Hg/[mL/min/g], P = 0.003), while maintaining MBF. CONCLUSION: NTG preferentially reduces CVR in the viable myocardium with ischemia. After NTG, tracer uptake in the ischemic myocardium will be relatively increased compared with that in the nonviable and nonischemic myocardium, leading to improvements in viability detection.     

The effect of flow on technetium-99m-teboroxime (SQ30217) and thallium-201 extraction and retention in rabbit heart

In order to evaluate the accuracy of blood flow measurement, the single-pass extraction, retention/wash-out and relative net uptake of 99mTc-teboroxime (SQ30217) and 201Tl were evaluated and compared in 20 isolated blood-perfused rabbit hearts at coronary flow rates ranging from 0.49 to 2.85 ml/g wet wt min-1. The average peak extraction of 201Tl (+/- s.d.) (0.67 +/- 0.11) marginally exceeded that of SQ30217 (0.62 +/- 0.12) (p = 0.06). Flow significantly affected the maximum net extraction of 201Tl and the 40-min net extractions of both 201Tl and SQ30217. Unexpectedly, the rate of 201Tl myocardial washout was significantly faster (p less than 0.05) than SQ30217 washout at all flow rates evaluated. Increasing coronary blood flow rate was associated with a more rapid clearance of both tracers from the myocardium (p less than 0.05 for both comparisons). The slope of the linear correlations between relative net SQ30217 uptake versus flow and relative net 201Tl uptake versus flow were found to be similar for up to 10 min after isotope injection. These data were interpreted to indicate that: 1. Thallium-201 might be slightly better extracted than SQ30217. 2. SQ30217 is cleared more slowly from the myocardium. 3. Thallium-201 and SQ30217 appear to be comparable tracers of myocardial perfusion for up to 10 min after injection under the single-pass conditions currently employed. 4. Additional studies are needed to clarify myocardial SQ30217 kinetics.     

201Tl SPET in the differential diagnosis of brain tumours.

The aims of this study were to assess the utility of 201Tl single photon emission tomography (SPET) in the differential diagnosis of brain tumours and to elucidate the relationship between 201Tl tumour uptake and degree of contrast-enhancement on magnetic resonance imaging (MRI). Early (15 min) and delayed (3 h) 201Tl SPET imaging and T1-weighted MRI were performed before and after Gd-DTPA enhancement in 101 (41 malignant and 60 benign) untreated brain tumours. The 201Tl uptake ratio (tumour-to-normal brain count ratio) for both the early and delayed SPET studies and the retention index (the ratio of delayed to early 201Tl uptake) were calculated. Malignant tumours were separated from benign tumours with 87% accuracy based on the assumption that tumours with a 201Tl retention index < 0.7 or no abnormal uptake are benign. Meningiomas and pituitary adenomas were differentiated from other benign tumours by their characteristic pattern on SPET. The degree of contrast-enhancement of the tumour on MRI was concordant with the early 201Tl uptake ratio for most histological types. However, schwannomas and cavernous haemangiomas showed a low 201Tl uptake ratio in spite of a high degree of contrast-enhancement on MRI. In conclusion, 201Tl SPET provides additional information that helps in the differential diagnosis of brain tumours.     

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.     

In vivo inaccessibility of somatostatin receptors to 111In-pentreotide in primary renal cell carcinoma

The presence of somatostatin receptors on human renal cell carcinomas in surgically removed kidneys has been demonstrated by autoradiography. The aim of this study was to detect to in vivo presence of somatostatin receptors in primary renal tumours and their possible metastases before surgery, using 111In-pentreotide scintigraphy. 201Tl was used as a sensitive tumour-seeking agent with blood flow-dependent uptake. Fifteen patients were imaged before surgical removal of the renal tumour. Thirteen tumours were malignant. The large tumours (more than 4 cm in diameter) did not accumulate 111In-pentreotide or 201Tl. In contrast, the single small tumour accumulated both tracers. A scalp skin metastasis was demonstrated in one patient by 201Tl and 111In-pentreotide uptake. In one case, known lung metastases were visualized with both 201Tl and 111In-pentreotide, but the lung metastases of another three patients as well as one case of epidural metastasis were not identified. In one patient with a photopaenic lesion, positive labelling of the surgically removed tumour was demonstrated by in vitro autoradiography. Somatostatin receptor scintigraphy with 111In-pentreotide appears to have little value for the detection of metastases in patients with renal cell carcinoma, as some metastases (especially those of the lungs) were missed. The absence of 111In-pentreotide uptake by large primary tumours is an interesting finding, suggesting inaccessibility of these very large tumours to drugs.     

Influence of increased 201Tl lung uptake on the myocardial viability of the patients with dilated cardiomyopathy under congestive heart failure]

Influence of increased 201Tl lung uptake on the myocardial viability was studied in 15 patients with dilated cardiomyopathy under congestive heart failure. Rest and 4 hours delayed 201Tl SPECT were obtained. At the same time anterior planar images were collected. In 10 patients of 15 patients 201Tl lung heart ratio in SPECT (LHR) was larger than that in planar images. Maximal 201Tl lung uptake was noted at the lower left lung adjacent to the heart. In the delayed images 201Tl lung uptake diminished. In 10 patients the value of LHR in the delayed images was less than 0.5. By comparing initial images with delayed images it was proved to be difficult to determine the myocardial margin adjacent to the increased 201Tl lung uptake. In 2 patients lateral defects were concealed by the increased 201Tl lung uptake. In the remaining patients lateral wall was similar to the hypertrophic myocardium. The effect of scatter due to the increased 201Tl lung uptake was noted in the neighboring myocardium. In most cases %201Tl uptake in the septum was relatively depressed by increased %201Tl uptake in the lateral wall. In the delayed images pseudo-redistribution was noted in the septum. Mean value of differences in %201Tl uptake between initial and delayed images was 8 (2-15)%. It was concluded that in case of increased 201Tl lung uptake SPECT could not accurately estimate myocardial viability by initial images and delayed images were necessary for precise estimation.     

Separate evaluation of beta-methyl fatty acid uptake and perfusion in rat myocardium

The kinetics and distribution of I-125 beta-methyl iodophenyl pentadecanoic acid (BMIPP) in rat's heart were studied for separate evaluation of perfusion and metabolism. Tl-201 and BMIPP were simultaneously injected. The experimental groups consisted of control (C), glucose (G) and sodium lactate loaded group (L). In C, myocardial uptake at 5 minutes after BMIPP injection was 3.60% ID/g and remained constant up to 60 minutes. The myocardium/lung ratio (2.44) and the myocardium/muscle ratio (4.55) of BMIPP were almost equal to those of Tl-201. But myocardium/liver ratio was low (1.31). In G, myocardial uptake of BMIPP (1.94 +/- 0.36% ID/g) and g-BMIPP/Tl (0.31 +/- 0.03) at 15 minutes after injection were significantly decreased (p less than 0.001) than those of C (3.16 +/- 0.18% ID/g and 0.48 +/- 0.05). In L. myocardial perfusion was decreased and g-BMIPP/Tl (0.73 +/- 0.14) was significantly higher (p less than 0.01) than those of C. Coefficient of variance of the density within a myocardium, and the ratio of inner to outer layer of myocardium (I/O ratio) were calculated from autoradiogram by videodensitometry. The myocardial distribution of BMIPP was more inhomogeneous, and the I/O ratio was lower than that of Tl-201, although these were not specific for metabolic interventions. In conclusion BMIPP is suitable for SPECT imaging and dual nuclide imaging by BMIPP and Tl-201 will provide informations about myocardial fatty acid metabolism and perfusion.     

Comparison of [(18)F]FDG PET and (201)Tl SPECT in evaluation of pulmonary nodules.

Recent reports have indicated the value of [(18)F]FDG PET and (201)Tl SPECT in diagnosing lung cancer. In this study, we compared the diagnostic value of FDG PET and (201)Tl SPECT in the evaluation of pulmonary nodules. METHODS: Sixty-three patients with 66 pulmonary nodules suspected to be lung cancer on the basis of chest CT were examined by FDG PET and (201)Tl SPECT (early and delayed scans) within a week of each study. For semiquantitative analysis, the standardized uptake value (SUV) or the tumor-to-nontumor activity ratio (T/N) (or both) was calculated. All of these lesions were completely removed thoracoscopically or by thoracotomy and were examined histologically. RESULTS: Fifty-four nodules were histologically confirmed to be malignant tumors, and 12 were benign. Both techniques delineated focal lesions with an increase in tracer accumulation in 41 of 54 lung cancers. (201)Tl SPECT on early or delayed scans (or both) identified 4 additional lung cancers that FDG PET images did not reveal: 3 bronchioloalveolar carcinomas and a well-differentiated adenocarcinoma. FDG PET identified 3 additional lung cancers that (201)Tl SPECT images did not reveal; 2 of these lung cancers were <2 cm in diameter. The mean FDG SUV and T/N of bronchioloalveolar carcinomas (2.06 +/- 0.76 and 3.49 +/- 1.03, respectively) were significantly lower than those of poorly differentiated adenocarcinomas (5.55 +/- 2.01 [P = 0.026] and 8.23 +/- 2.16 [P = 0.01], respectively). However, no significant difference was found in (201)Tl T/N on early and delayed scans between bronchioloalveolar carcinomas (1.64 +/- 0.29 and 1.87 +/- 0.42, respectively) and poorly differentiated adenocarcinomas (1.58 +/- 0.32 and 2.76 +/- 1.36, respectively). Of the 12 benign nodules, FDG PET and (201)Tl SPECT showed false-positive results for the same 7 benign nodules (58.3%) (4 granulomas, 1 sarcoidosis, 1 inflammatory pseudotumor, and 1 aspergilloma). Negative FDG PET findings and positive (201)Tl SPECT findings were obtained only for bronchioloalveolar carcinomas or a well-differentiated adenocarcinoma but not for other histologic types of lung cancers or benign pulmonary nodules. CONCLUSION: No significant difference was found between FDG PET and (201)Tl SPECT in specificity for the differentiation of malignant and benign pulmonary nodules. The degree of differentiation of lung adenocarcinoma correlated with FDG uptake but not with (201)Tl uptake. Bronchioloalveolar carcinoma (a well-differentiated, slow-growing tumor) findings typically were positive with (201)Tl but were negative with FDG. The combination of FDG PET and (201)Tl SPECT may provide additional information regarding the tissue characterization of pulmonary nodules.     

Assessment of glioma viability by estimating 201Tl SPET tumour uptake volume.

The aim of this study was to develop a quantitative method to assess viable tumour based on post-operative 201Tl single photon emission tomography (SPET). We studied 15 patients with histologically defined highly malignant gliomas in the post-operative phase before initiation of adjuvant treatment. A 201Tl index was calculated in two ways: maximal counts versus mean counts within a region of interest (ROI). The tumour uptake volume (TUV) within the lesion was calculated from the number of voxels that had 201Tl uptake above a threshold calculated from the uptake on the contralateral side. The threshold was set at three levels: A = 1.4 times the mean 201Tl uptake in a three-dimensional reference ROI + 96.7% confidence interval (the TUV was corrected by subtraction of the volume in the reference ROI that had uptake above the threshold with compensation for unequal ROI sizes); B = 1.4 times the mean reference ROI + 99% confidence interval; and C = maximum 201Tl uptake in the reference ROI. The SPET results were compared with the tumour volumes calculated from CT scans. Thirteen tumours showed high post-operative 201Tl uptake. The 201Tl index was not significantly correlated with histological grade within the group of highly malignant gliomas. 201Tl SPET tumour uptake volume method B was highly significantly correlated with CT estimated tumour volume. In conclusion, the measurement of post-operative 201Tl SPET tumour uptake volume demonstrates metabolically active glioma tissue and is an alternative method for the monitoring of glioma treatment response.