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- Högberg, Jonas, 1976, et al.
(author)
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Bremsstrahlung imaging of 90Y microspheres shows poor resemblance with distributions of 99mTc-MAA in liver
- 2010
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In: Journal of the European Society of Therapeutic Radiology and Oncology. - 0167-8140. ; 94:1, s. 25-26
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Conference paper (other academic/artistic)abstract
- PURPOSE To study the resemblance between the distributions of pre- therapeutic 99mTc-MAA and therapeutic 90Y-microspheres, used for ra- dioembolization of liver tumours, making use of gamma- and bremsstrahlung imaging. Furthermore, to establish the accuracy of this method by compar- isons of spatial resolution and radioactivity, performed on line source in water phantom and on resected tumour and normal liver from patients previously treated with 90Y-microspheres. MATERIALS 3 patients diagnosed with liver tumours and planned for surgery; 1 with hepatocellular carcinoma and 2 with cholangiocarcinoma, were treated with SIRTEX R © 90Y-microspheres after standard diagnostic SPECT/CT imag- ing with 99mTc-MAA. The images acquired with gamma camera were com- pared regarding distributions of radioactivity; gamma radiation from the 99mTc-MAA distributions and bremsstrahlung from the distributions of 90Y- microspheres (the latter with a wide bremsstrahlung energy window). Resec- tions of tumour- and some normal liver tissues were performed on all three patients; the resected tissues were sliced, smaller samples were punched out and the radioactivity was measured with a NaI-detector. Furthermore, autoradiography was performed on some slices. A line source with the in- ner diameter 1 mm was positioned in a cylindrical water phantom with the diameter 20 cm; first the line source was filled with 99mTc, then emptied and filled with 90Y. SPECT/CT imaging was performed on both line source se- tups. The spatial resolutions for both radionuclides were then compared. The results from the imaging comparisons performed on the patients were then evaluated with the complementary radiological methods described above. RESULTS The comparison of images from 99mTc-MAA and 90Y showed a considerable deviance in activity distribution for two of the patients. One ex- ample is shown in the figure, the upper image showing 99mTc-MAA and the lower showing 90Y-microspheres. The moderate difference in spatial resolu- tions for 99mTc and 90Y, (15 vs 18 mm FWHM) confirmed the accuracy of these findings. The other radiological methods did also confirm the macro- scopic activity distribution as shown with bremsstrahlung imaging. CONCLUSIONS Bremsstrahlung imaging is a satisfying and reliable method in showing the actual macroscopic distribution of therapeutic 90Y-microspheres used for radioembolization of liver tumours. The results further demonstrate the need for a better diagnostic method than the one currently used, with 99mTc-MAA, thereby providing a better pre-dosimetry; hopefully with a better selection of patients, regarding tumour regression and a lower risk of liver failure.
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| 2. |
- Högberg, Jonas, 1976, et al.
(author)
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Heterogeneity of microsphere distribution in resected liver and tumour tissue following selective intrahepatic radiotherapy
- 2014
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In: EJNMMI Research. - : Springer Science and Business Media LLC. - 2191-219X. ; 4:48
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Journal article (peer-reviewed)abstract
- BACKGROUND Selective arterial radioembolisation of liver tumours has increased, because of encouraging efficacy reports; however, therapeutic parameters used in external beam therapy are not applicable for understanding and predicting potential toxicity and efficacy, necessitating further studies of the physical and biological characteristics of radioembolisation. The aim was to characterise heterogeneity in the distribution of microspheres on a therapeutically relevant geometric scale considering the range of yttrium-90 (90Y) β-particles. METHODS Two patients with intrahepatic cholangiocarcinoma, marginally resectable, were treated by selective arterial embolisation with 90Y resin microspheres (SIRTEX®), followed 9 days post-infusion by resection, including macroscopic tumour tissue and surrounding normal liver parenchyma. Formalin-fixed, sectioned resected tissues were exposed to autoradiographic films, or tissue biopsies of various dimensions were punched out for activity measurements and microscopy. RESULTS Autoradiography and activity measurements revealed a higher activity in tumour tissue compared to normal liver parenchyma. Heterogeneity in activity distribution was evident in both normal liver and tumour tissue. Activity measurements were analysed in relation to the sample mass (5 to 422 mg), and heterogeneities were detected by statistical means; the larger the tissue biopsies, the smaller was the coefficient of variation. The skewness of the activity distributions increased with decreasing biopsy mass. CONCLUSIONS The tissue activity distributions in normal tissue were heterogeneous on a relevant geometric scale considering the range of the ionising electrons. Given the similar and repetitive structure of the liver parenchyma, this finding could partly explain the tolerance of a relatively high mean absorbed dose to the liver parenchyma from β-particles. Keywords: Radioembolisation; Y-90; SIR; Surgery; Activity heterogeneity
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| 3. |
- Högberg, Jonas, 1976, et al.
(author)
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On the dose heterogeneity in normal liver tissue due to treatment of liver tumors with yttrium-90 microspheres
- 2012
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In: 25th Annual Congress on European Association of Nuclear Medicine, Milano, Italy, October 27-31, 2012. European Journal of Nuclear Medicine and Molecular Imaging. - : Springer Science and Business Media LLC. - 1619-7070 .- 1619-7089. ; 39:suppl 2
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Conference paper (other academic/artistic)abstract
- Aim: When treating patients with primary or metastatic liver cancer, applying external radiotherapy, an absorbed dose of 30 - 35 Gy to the whole normal liver tissue volume is associated with a 5 % risk of radiation-induced hepatitis. If less than half of the normal liver volume is being exposed, the threshold for a 5 % risk of hepatitis is increased to above 60 Gy for both primary and metastatic liver cancer. Experience with patients treated with SIR-Spheres® (Sirtex Medical Ltd.), resin microspheres aggregated with yttrium-90, has shown that most patients tolerate an average absorbed dose to normal liver tissue higher than 60 Gy. The high tolerance for this treatment procedure can probably be explained by the resulting heterogenic distribution of radioactivity. It is of interest to study the degree of heterogeneity in the distribution of radioactivity in normal liver tissue, in order to explain or even predict the tolerance to radiation. The aim of this study was to describe the degree of heterogeneity by comparing the relative standard deviations of the radioactivity concentration for different sample mass categories. Materials and Methods: Two patients with cholangiocarcinoma were planned for a combined treatment with yttrium-90-aggregated SIR-Spheres followed by surgery 9 days after radiotherapy. According to standard protocol for treatments with SIR-Spheres, the therapies were preceded by Tc-99m-labled Macro aggregated albumin (Tc-99m-MAA) distribution studies for pre-therapeutic dosimetry and lung shunting evaluations. After surgery the resected tissue, containing both tumour and normal tissue, was studied regarding the distribution of radioactivity. Several small circular samples of normal liver tissue were punched out from 2 mm thick slices of resected tissue, deliberately varying the sizes, and thus the masses of the tissue samples (from 6 to 102 mg). The samples were weighed and categorized in two (first patient) and three (second patient) groups, depending on sample mass. After this the radioactivity was measured with a NaI(Tl) detector. The relative standard deviations (SD/Median) for the radioactivity concentration for each sample mass group were determined and compared. Results: The relative standard deviation for the radioactivity concentration was decreasing rapidly with increasing sample mass. Conclusion: The results indicate a considerable degree of heterogeneity in the distribution of microspheres. One probable explanation for this heterogeneity is clustering of microspheres in the blood vessels.
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| 4. |
- Högberg, Jonas, 1976, et al.
(author)
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Radiation exposure during liver surgery after treatment with (90)Y microspheres, evaluated with computer simulations and dosimeter measurements.
- 2012
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In: Journal of radiological protection : official journal of the Society for Radiological Protection. - : IOP Publishing. - 1361-6498. ; 32:4, s. 439-46
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Journal article (peer-reviewed)abstract
- Purpose. Two patients with liver tumours were planned for a combined treatment, including surgery with preceding injections of β(-) radiation emitting (90)Y microspheres (SIRTEX(®)). The aim of this paper is to present a method of pre-surgical computer simulations of the absorbed dose rate on the surface of tumour tissue, combined with measurements of the actual absorbed dose rate on resected tissue, in order to estimate the absorbed dose to a surgeon's fingers during such surgery procedures. Methods and Materials. The dose rates from β(-) radiation on the surface of tumour tissue were simulated with the software VARSKIN(®)Mod2. The activity concentrations in tumours were estimated, based on SPECT/CT distribution studies of (99m)Tc-MAA and confirmed by SPECT/CT bremsstrahlung studies of (90)Y microspheres. The activity distributions were considered as homogeneous within the tumour regions. The absorbed dose rates at different tumour tissue spots were calculated based on measurements with thermo-luminescent dosimeters (TLD) fastened on resected tissue. Results. The simulations showed a good agreement with the averaged absorbed dose rates based on TLD measurements performed on resected tissue, differing by 13% and 4% respectively. The absorbed dose rates at the measured maximum hotspots were twice as high as the average dose rates for both patients. Conclusion. The data is not sufficient in order to draw any general conclusions about dose rates on tumour tissue during similar surgeries, neither about the influence of dose rate heterogeneities nor about average dose rates. However, the agreement between simulations and measurements on these limited data indicate that this approach is a promising method for estimations of the radiation exposure to the surgeons' fingers during this kind of surgery procedure. More data from similar surgeries are necessary in order to validate the method.
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