| 1. |
- Källén, Kristina, et al.
(author)
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Assessment of glioma viability by estimating 201Tl SPET tumour uptake volume
- 1999
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In: Nuclear Medicine Communications. - 1473-5628. ; 20:9, s. 837-844
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Journal article (peer-reviewed)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.
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| 2. |
- Starck, Sven-Åke, et al.
(author)
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Digital filtering of bone scans : an ROC study
- 1997
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In: Nuclear medicine communications. - : Ovid Technologies (Wolters Kluwer Health). - 0143-3636 .- 1473-5628. ; 18:2, s. 98-104
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Journal article (peer-reviewed)abstract
- The aims of this study were to investigate if digital filtering can increase the sensitivity and specificity of bone scans, and to find the type of filter most suitable for bone images at various count levels. We also wished to examine if filtering allows the administered activity or the examination time to be reduced, and if it is easier to detect low-contrast uptake using a digital filter. Images containing a total of 100, 350 and 1000 kcounts were acquired in a 256 x 256 matrix using a transmission phantom simulating the thoracolumbar region. Receiver operating characteristic (ROC) analysis demonstrated that digital filtering increases the sensitivity and specificity of bone scintigraphy. A low-pass filter for images with low statistics (100 kcounts), which contain 2-5 counts per pixel in the ribs and vertebrae respectively, and a Metz filter for images with normal (5-19 counts per pixel) to good (20-54 counts per pixel) statistics, increase the area under the ROC curve significantly (99% confidence level) compared to unfiltered images. Filtering also increases the detectability of low-contrast objects compared with unfiltered images. Digital filtering might be an alternative to raising the number of counts in the image. An alternative is to reduce the administered activity and hence the effective dose to the patient, or to reduce the examination time-which is an advantage when treating elderly patients or patients with pain.
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| 3. |
- Ärlig, A, et al.
(author)
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Selection of collimator for rCBF studies and evaluation of triple-headed SPET using noise-resolution plots
- 1997
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In: Nuclear Medicine Communications. - 1473-5628. ; 18:7, s. 655-661
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Journal article (peer-reviewed)abstract
- We investigated the effect of collimator selection on image quality in regional cerebral blood flow (rCBF) studies of the brain performed with 99Tc(m)-HMPAO. A triple-headed SPET system (GE/CGR Neurocam) was used, together with three sets of parallel-hole collimators - general-purpose (GP), high-resolution (HR) and ultra-high-resolution (UHR). Two image quality parameters were used to describe the image quality, namely, noise and resolution. Noise was measured in experimental and Monte-Carlo simulated SPET studies of a cylinder phantom of uniform activity as the pixel root mean square error (RMS) and as the coefficient of variation (CV) of quantitative rCBF values. Resolution was measured as full-width at half-maximum in experimental SPET studies of a line-source. Plots of noise versus resolution for the different collimators were obtained by varying the cut-off frequency of the Hanning filter applied in the reconstruction of transaxial slices. From these noise-resolution plots, we were able to determine which collimator gave the best resolution for a specific noise level. A lowest reasonable noise level may be established by comparison with the inter-observer CV of the quantification method.
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