Time sequential single photon emission computed tomography studies in brain tumour using thallium-201

Time sequential single photon emission computed tomography (SPECT) studies using thallium-201 were performed in 25 patients with brain tumours to evaluate the kinetics of thallium in the tumour and the biological malignancy grade preoperatively. After acquisition and reconstruction of SPECT data from 1 min post injection to 48 h (1, 2, 3, 4, 5, 6, 7, 8, 9, 10 and 15–20 min, followed by 4–6, 24 and 48 h), the thallium uptake ratio in the tumour versus the homologous contralateral area of the brain was calculated and compared with findings of X-ray CT, magnetic resonance imaging, cerebral angiography and histological investigations. Early uptake of thallium in tumours was related to tumour vascularity and the disruption of the blood-brain barrier. High and rapid uptake and slow reduction of thallium indicated a hypervascular malignant tumour; however, high and rapid uptake but rapid reduction of thallium indicated a hypervascular benign tumour, such as meningioma. Hypovascular and benign tumours tended to show low uptake and slow reduction of thallium. Long-lasting retention or uptake of thallium indicates tumour malignancy. Correspondence to: T. Ueda     

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.     

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.     

Relationship between thallium-201 kinetics and proliferative activity assessed by monoclonal antibody MIB-1 in brain tumours

To clarify the relationship between thallium-201 chloride kinetics and proliferative activity in brain tumours, a single-photon emission tomographic (SPET) study was performed and the results correlated with monoclonal antibody MIB-1 staining of the tumour tissue. ²⁰¹Tl SPET was performed 10 min (early scan) and 2 h (delayed scan) after intravenous administration of ²⁰¹Tl (111 MBq) in 34 intra-axial tumours including 24 malignant tumours, and in 27 extra-axial tumours including one malignant tumour. Tumour ²⁰¹Tl kinetic parameters [early and delayed uptake ratios (ER and DR, respectively), retention index (RI), and the ratio of tumour delayed activity to early activity (Td/Te)] were compared with tumour tissue MIB-1 labelling indices (MIB-1 LI) representative of tumour cell proliferative activity. In the intra-axial tumours, ER and DR and MIB-1 LI were significantly higher in the malignant tumours than in the benign tumours. ER and DR were significantly correlated with MIB-1 LI (P<0.01 and P<0.05, respectively), but RI and Td/Te were not. In the extra-axial benign tumours, ER was as high as that in the intra-axial malignant tumours, while MIB-1 LI was equal to that in the intra-axial benign tumours. There were no significant correlations between any ²⁰¹Tl kinetic parameters and MIB-1 LI. This study indicates that ²⁰¹Tl ER may be the most reliable parameter for predicting the proliferative activity of intra-axial tumours.     

The role of thallium-201 single photon emission tomography in the investigation and characterisation of brain tumours in man and their response to treatment

The aim of this study was to characterise brain tumour type and treatment response in relation to the uptake of thallium-201.²⁰¹Tl single photon emission tomography (SPET) was performed in 58 patients with brain tumours. Fifty-six patients were utilised for the statistical comparison of the early and delayed²⁰¹Tl indices expressed as the ratio of tumour to contralateral cerebral hemisphere uptake. The retention index of²⁰¹Tl in the tumour tissue calculated from the early and delayed scans was also analysed. Furthermore, in 56 patients with 58 brain tumours, a comparison was made of the diagnostic value of high²⁰¹Tl uptake and gadolinium diethylene triamine penta-acetic acid (Gd-DTPA) enhancement on MRI scans. Although high²⁰¹Tl uptake was observed in viable malignant gliomas, brain metastases, meningiomas and malignant teratoma, the viable malignant gliomas could not be differentiated from brain metastases and extracerebral tumours by means of²⁰¹Tl indices.²⁰¹Tl SPET failed to diagnose a viable ring-enhanced tumour with a thin rim and small tumours of less than 1.5 cm in diameter visualised by Gd-DTPA-enhanced MRI. In spite of this,²⁰¹Tl SPET appears to be effective for determination of the malignant viability of tumours     

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.     

Dynamic 99Tcm-ECD SPET correlates well with 201Tl indices in brain tumours

The dynamic 99Tcm-ethyl cysteinate dimer (99Tcm-ECD) single photon emission tomographic (SPET) characteristics of brain tumours were investigated and compared with 201Tl-chloride SPET indices. Thirty-five patients with histologically confirmed benign and malignant tumours were evaluated using dynamic and standard 99Tcm-ECD. Twenty-eight patients were also examined using standard 201Tl SPET. The following 201Tl indices were calculated: early uptake ratio, delayed uptake ratio, washout rate and retention index. The relationship between uptake of 99Tcm-ECD on dynamic SPET and 201Tl indices was analysed. Nine patients showed positive uptake on dynamic 99Tcm-ECD SPET, all of whom had benign tumours, including five meningothelial meningiomas, three pituitary adenomas of the chromophobe type and one chemodectoma without malignancy. The mean early uptake ratio of the tumours with positive uptake was significantly higher than that of the tumours with negative uptake (17.1 +/- 5.5 vs 9.0 +/- 5.7, P = 0.004). The mean washout rate of the tumours with positive uptake was significantly higher than that of the tumours with negative uptake (61.0 +/- 27.7 vs 0.35 +/- 30.9, P = 0.0004). The mean retention index of the tumours with positive uptake was significantly lower than that of the tumours with negative uptake (0.27 +/- 0.12 vs 0.88 +/- 0.48, P = 0.000006). Only benign tumours showed positive uptake on dynamic 99Tcm-ECD SPET. The 201Tl indices correlated well with the uptake of 99Tcm-ECD on dynamic SPET. The results suggest that dynamic 99Tcm-ECD SPET can identify the benign character of tumours of the brain.     

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%).     

Sequential scintigraphic strategy for the differentiation of brain tumours

Both thallium-201 and iodine-123 alpha-methyltyrosine (123I-IMT) have been shown to be useful in the diagnostic evaluation of brain tumours. The aim of this study was to investigate the respective contributions of 201Tl and 123I-IMT single-photon emission tomography (SPET) in the non-invasive evaluation of intracerebral tumours. We analysed 65 patients with the following brain tumours: 8 non-neoplastic lesions, 4 meningiomas, 12 low-grade gliomas, 28 high-grade gliomas, 11 metastases and 2 high-grade lymphomas. 201Tl SPET and 123I-IMT SPET were performed [start of 201Tl SPET: 15 min p.i. (early) and 180 min p.i. (delayed); start of 123I-IMT SPET: 15 min p.i.]. The intensity of uptake was quantified as the ratio between tracer accumulation in the tumour and in the contralateral hemisphere. None of the non-neoplastic lesions or low-grade gliomas expressed marked 201Tl uptake. All malignant tumours except one small metastasis and all meningiomas except one small, cystic and degenerated lesion showed significant 201Tl accumulation [Tl(15')>2.0]; 123I-IMT uptake was either absent or intermediate in non-malignant lesions except in two low-grade gliomas; the highest levels were observed in high-grade gliomas followed by metastases and lymphomas (mean IMT: 2.7 vs. 2.1 vs. 1.8), with metastases showing a high variability in 123I-IMT uptake (range: 0.8-3.6). Using 201Tl to distinguish non-neoplastic lesions from malignant tumours and meningiomas, 63 of 65 patients were characterised correctly. In the latter group, high-grade gliomas were correctly identified in 27 of 28 cases by their amino acid uptake. It is concluded that the combination of 201Tl and 123I-IMT surpasses the accuracy of each single test in the differentiation of space-occupying lesions of the brain. Based on these preliminary results, a sequential strategy is proposed involving an initial 201Tl SPET study and an additional 123I-IMT SPET study in the event of positive 201Tl uptake.     

Various imaging modalities for the detection of salivary gland lesions: the advantages of 201Tl SPET

The aim of this study was to compare dual-isotope (99Tc(m) and 201Tl) SPET imaging with computed tomography (CT) and magnetic resonance imaging (MRI) in the differentiation of various lesions of the major salivary glands. Twenty-two patients underwent dual-isotope SPET imaging, of whom 12 also had CT and 15 also had an MRI study. The uptake ratio and retention index for 99Tc(m) and 201Tl were calculated by drawing regions of interest on the involved and normal glands. Both CT and MRI were interpreted by two radiologists. All malignant tumours were detected by all three modalities. Warthin's tumours were detected by dual-isotope SPET imaging; however, MRI failed to differentiate Warthin's tumour from pleomorphic adenoma. Of 13 other benign tumours, dual-isotope SPET correctly diagnosed 12. Of 16 tumours showing a cold defect on the 99Tc(m) images, parametric analysis with 201Tl gave an accuracy of 94%, whereas CT gave an accuracy of 70-90%. MRI was 73-91% accurate in differentiating between benign (Warthin's) and malignant tumours. We believe that dual-isotope SPET imaging (99Tc(m) and 201Tl), together with semi-quantitative analysis, is the method of choice for differentiating between various lesions of the major salivary glands.     

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.     

Differentiation of prostate cancer and benign prostatic hyperplasia: the clinical value of<Superscript>201</Superscript>Tl SPECT—A pilot study

PURPOSE: Thallium-201 (201Tl) is a recognized tumor-imaging agent; however, the usefulness of 201Tl in prostate cancer has not been studied. The purpose of this preliminary study was to evaluate the efficacy of 201Tl single-photon emission computed tomography (SPECT) imaging for differentiating prostate cancer from benign prostatic hyperplasia (BPH). METHODS: 201Tl pelvic SPECT was performed in 10 patients (aged 64-78 years) with biopsy-proven BPH before transurethral resection of the prostate and 15 patients (aged 65-81 years) with biopsy-proven prostate cancer prior to any therapeutic modality or invasive surgical procedures for treatment of their prostate cancer. RESULTS: From the 15 patients with prostate cancer, 201Tl pelvic SPECT detected prostate cancer in 13 (86.7%) but not in 2 (13.3%) patients with Gleason scores of 5 (2 + 3). In contrast, all 10 patients with BPH (100.0%) had negative results of 201Tl pelvic SPECT. CONCLUSION: Our study showed that 201Tl pelvic SPECT scan is very helpful in distinguishing between prostate cancer and BPH.     

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.     

Thallium-201 brain SPECT to diagnose aggressiveness of meningiomas

This investigation was conducted to determine the ability of 201Tl brain SPECT with respect to preoperative prediction of lesional aggressiveness of meningioma. Fifty-nine lesions in 42 patients were examined. Early (15 min) and late (3 h) SPECT were obtained. Early uptake ratio (ER; lesion to normal brain average count ratio), late uptake ratio (LR) and the ratio of LR to ER (L/E ratio) were calculated. Twenty-three lesions exhibited malignant features based on histologic or clinical course such as recurrence or skull invasion. Both ER and LR of malignant meningiomas were significantly higher than those in thirty-six benign lesions. Benign lesions were classified into two groups for further analysis: meningotheliomatous type, which is the most common histology, and benign lesions other than the meningotheliomatous (other benign) type. ER in other benign type was lower than the meningotheliomatous and the malignant type. LR afforded differentiation of the malignant type from the two benign types. These two benign types could be distinguished on the basis of the L/E ratio. These results indicate that high pre-operative ER and LR values in patients with meningioma are indicators of the aggressiveness of lesions, i.e., malignant meningioma, recurrence or skull invasion.     

The retention indices of 201Tl-SPECT in brain tumors

OBJECTIVE: The aim of this study was to assess the utility of 201Tl SPECT in the differential diagnosis of intracranial tumors and to determine the relationship between 201Tl uptake and histological types. METHODS: Thirty-eight patients (19 males and 19 females) with thirty-eight brain tumors were evaluated with 201Tl-SPECT. The early and delayed 201Tl uptake ratio was calculated, and the retention index (RI) was applied as follows; RI = delayed uptake ratio/early uptake ratio. RESULTS: The RI of malignant tumors was higher (0.72 +/- 0.18) than that of benign tumors (0.50 +/- 0.16) and the difference was statistically significant (p = 0.00045). The difference between high-grade glioma (0.80 +/- 0.15) and metastatic tumors (0.64 +/- 0.19) was statistically significant (p = 0.039). CONCLUSION: 201Tl-SPECT may add useful biochemical information and could differentiate malignant brain tumors from benign lesions, but the RI of metastatic tumors varied depending on the organs with the primary lesion and histological types.     

Role of thallium-201 in the diagnosis of solitary bone lesions

Thallium-201 is known to accumulate in malignant tumours. In this work we are evaluating the role of thallium in differentiating benign from malignant solitary bone lesions in 28 patients with solitary bone lesions on 99Tcm-MDP bone scans. Lesions' uptake of 201Tl was evaluated using visual assessment and lesion to background ratio. We found significant uptake with a mean lesion to background ratio of 4.27 in malignant lesions and no or faint uptake with a mean lesion to background ratio of 1.37 in benign lesions.     

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.     

Relationship between thallium-201 kinetics and proliferative activity assessed by monoclonal antibody MIB-1 in brain tumours.

To clarify the relationship between thallium-201 chloride kinetics and proliferative activity in brain tumours. a single-photon emission tomographic (SPET) study was performed and the results correlated with monoclonal antibody MIB-1 staining of the tumour tissue. 201T1 SPET was performed 10 min (early scan) and 2 h (delayed scan) after intravenous administration of 201TI (111 MBq) in 34 intra-axial tumours including 24 malignant tumours, and in 27 extra-axial tumours including one malignant tumour. Tumour 201T1 kinetic parameters [early and delayed uptake ratios (ER and DR, respectively), retention index (RI), and the ratio of tumour delayed activity to early activity (Td/Te)] were compared with tumour tissue MIB-1 labelling indices (MIB-1 LI) representative of tumour cell proliferative activity. In the intra-axial tumours, ER and DR and MIB-1 LI were significantly higher in the malignant tumours than in the benign tumours. ER and DR were significantly correlated with MIB-1 LI (P<0.01 and P<0.05, respectively), but RI and Td/Te were not. In the extra-axial benign tumours, ER was as high as that in the intra-axial malignant tumours, while MIB-1 LI was equal to that in the intra-axial benign tumours. There were no significant correlations between any 201T1 kinetic parameters and MIB-1 LI. This study indicates that 201T1 ER may be the most reliable parameter for predicting the proliferative activity of intra-axial tumours.     

The effect of steroid on thallium-201 uptake by malignant gliomas

In order to assess the effect of steroid on thallium-201 uptake by glioma,²⁰¹TI single-photon emission tomography was performed before and after steroid administration in four patients with recurrent malignant glioma. After steroid administration the²⁰¹Tl index, expressed as the ratio of²⁰¹Tl uptake in the tumour to that in the contralateral cerebral hemisphere, was 0.77±0.11 of the value before steroid (mean±SD:P<0.05 by pairedt test). The²⁰¹Tl index has been used as a possible indicator for the differentiation of malignant gliomas from relatively benign tumours or radiation necrosis. The present results indicate that the effect of steroid has to be taken into account when semi-quantitative analysis, e.g. by means of the²⁰¹Tl index, is used in patients with brain tumours.     

Use of 201Tl SPECT for evaluation of biologic behavior in pituitary adenomas.

Although pituitary adenomas are regarded as benign tumors, some of them behave aggressively with malignant behavior of invasion and metastasis. Prediction of such biologic behavior in a tumor is important for therapeutic planning. The purpose of this study was to assess the usefulness of 201Tl chloride SPECT (201Tl SPECT) for evaluation of biologic behavior in pituitary adenomas. METHODS: 201Tl SPECT was performed on 22 patients with pituitary adenomas. 201Tl uptake indices were calculated, and the results were compared between invasive pituitary adenomas and noninvasive pituitary adenomas. Correlation of the 201Tl uptake index and the MIB1 monoclonal antibody labeling index (MIB1 labeling index) of the tumors was also estimated. RESULTS: In comparison with noninvasive pituitary adenomas, invasive pituitary adenomas exhibited significantly higher 201Tl uptake indices on both the early and the delayed images (P = 0.0010 and 0.0019, respectively). A significant correlation was found between the 201Tl uptake index on the delayed image and the MIB1 labeling index (P = 0.0107). CONCLUSION: 201Tl SPECT can be useful for detecting biologic aggressiveness in pituitary adenomas.