| 1. |
- Källén, Kristina
(författare)
-
201Thallium SPECT; accuracy in astrocytoma diagnosis and treatment evaluation
- 1999
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The aims of the studies included in this thesis were:• to investigate the reliability of 201thallium single photon emission computed tomography (201Tl SPECT) for preoperative diagnosis and histological staging of malignant astrocytomas in comparison with CT; • to develop a method for quantification of cerebral thallium uptake, and to evaluate the quantitative measurement in comparison with CT, for astrocytoma treatment follow-up purposes; • to compare quantitative 201Tl SPECT and proton magnetic resonance spectroscopy (1H-MRS) with conventional MR imaging for astrocytoma monitoring, and to evaluate associations between change of morphological tumour characteristics during treatment and changes of cerebral thallium uptake and metabolic ratios. Results and conclusions:• High 201Tl-index, calculated as a ratio comparing tumour uptake to uptake in the contralateral hemisphere, is an indicator of highly malignant astrocytoma. Differentiation between the high-grade astrocytomas, the low-grade astrocytomas, and infectious lesions is only partial, with an overlap of 201Tl-indexes between these groups. High-grade astrocytomas that do not show contrast enhancement on CT, and astrocytomas with central necrosis and moderate ring-enhancement, tend to be underestimated when evaluated by 201Tl-index calculation. 201Tl SPECT is not a reliable method for non-invasive tumour staging among the group of highly malignant astrocytomas. • Quantification of cerebral 201Tl-uptake, defining the volume of viable tumour tissue, is a new method for astrocytoma chemotherapy monitoring. Results suggest that the method provides prognostic information, and information of treatment efficacy, at an earlier stage than CT. • We did not find a higher accuracy of quantitative 201Tl SPECT than of MR for monitoring purposes and our results indicated that treatment induced MR changes were interrelated with 201Tl-uptake variations. • Multi-voxel 1H-MRS was difficult to apply for astrocytoma treatment monitoring, due to the anatomical and histological heterogeneity of astrocytomas.
|
|
| 2. |
- Källén, Kristina, et al.
(författare)
-
Assessment of glioma viability by estimating 201Tl SPET tumour uptake volume
- 1999
-
Ingår i: Nuclear Medicine Communications. - 1473-5628. ; 20:9, s. 837-844
-
Tidskriftsartikel (refereegranskat)abstract
- 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.
|
|
| 3. |
- Källén, Kristina, et al.
(författare)
-
Evaluation of malignancy in ring enhancing brain lesions on CT by thallium-201 SPECT
- 1997
-
Ingår i: Journal of Neurology, Neurosurgery and Psychiatry. - 1468-330X. ; 63:5, s. 569-574
-
Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: To investigate patients with cystic enhancing lesions on CT and to determine whether thallium-201 (201Tl) SPECT adds to further preoperative information in differential diagnosis between gliomas and abscesses. METHODS: Twenty one patients with cystic ring enhancing CT findings were studied and uptake indices were compared with CT enhancement volumes, histopathology, and survival times. RESULTS: Fourteen high grade gliomas, three low grade gliomas, and four abscesses were found. Uptake was higher in the highly malignant glioma group (median thallium index (TI)=2.1), than in the low grade glioma group (median TI=1.4) or among the abscesses (median TI=1.6). Overlapping indices were found between high and low malignant cystic gliomas as well as between either one of the glioma groups and the infectious lesions, and there were no significant differences between groups. There was a level at the value 2, where TI > or = 2 correlated with tumour diagnosis. One low grade tumour had an extremely high index and a very high enhancement volume. Indices correlated significantly with CT enhancement volumes (P=0.005). There was no significant correlation between Tl indices and patient survival times among the high grade gliomas. One patient with a highly malignant tumour but low Tl uptake < 2, had a survival > five years. CONCLUSIONS: It is concluded that high 201Tl uptake in enhancing cystic lesions is an indicator of highly malignant glioma. However, the differentiation between the high malignant gliomas and abscesses or low malignant gliomas by 201TL SPECT is only partial with an overlap between these groups.
|
|
| 4. |
- Källén, Kristina, et al.
(författare)
-
Preoperative grading of glioma malignancy with thallium-201 single-photon emission CT: comparison with conventional CT
- 1996
-
Ingår i: AJNR. - 1936-959X. ; 17:5, s. 925-932
-
Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: To compare thallium-201 single-photon emission CT with conventional CT in grading the malignancy of gliomas and to determine the reliability of each in tumor assessment. METHODS: We studied 37 patients who had gliomas (31 high grade and 6 low grade) and compared the CT findings with the thallium-201 index, which we defined as tumor uptake relative to the uptake in the contralateral hemisphere. RESULTS: Among the high-grade gliomas, we observed a significant correlation between breakdown volume of the blood-brain barrier and thallium-201 uptake. However, 8 of the high-grade gliomas had low thallium-201 uptake, in the same range as the low-grade gliomas. Of these, 2 were nonenhancing and the other 6 showed ring enhancement on CT scans. Analysis of variance showed no significant difference in thallium-201 indexes between low-grade gliomas and highly malignant (grade II-III) gliomas. Accuracy of thallium-201 imaging was lower (78%) than that of CT (84%) in identifying high-grade gliomas. CONCLUSIONS: Damage to the blood-brain barrier is a prerequisite for uptake of thallium-201 in gliomas. Tumors with central necrotic areas and moderate ring enhancement tend to be underestimated when evaluated by means of thallium-201 scintigraphy. The results indicate a need for caution when interpreting findings on images obtained with thallium-201 single-photon emission CT in preoperative evaluation of brain tumors.
|
|
