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On the dose heterogeneity in normal liver tissue due to treatment of liver tumors with yttrium-90 microspheres

Konferensbidrag (offentliggjort, men ej förlagsutgivet)
Författare Jonas Högberg
Magnus Rizell
Ragnar Hultborn
Johanna Svensson
Olof Henrikson
Peter Gjertsson
Peter Bernhardt
Publicerad i 25th Annual Congress on European Association of Nuclear Medicine, Milano, Italy, October 27-31, 2012. European Journal of Nuclear Medicine and Molecular Imaging
Volym 39
Nummer/häfte suppl 2
Sidor S281-S281
ISSN 1619-7070
Publiceringsår 2012
Publicerad vid Institutionen för kliniska vetenskaper, Avdelningen för radiofysik
Institutionen för kliniska vetenskaper, Avdelningen för kirurgi
Institutionen för kliniska vetenskaper, Avdelningen för onkologi
Institutionen för kliniska vetenskaper, Avdelningen för radiologi
Institutionen för medicin, avdelningen för molekylär och klinisk medicin
Sidor S281-S281
Språk en
Länkar dx.doi.org/10.1007/s00259-012-2221-...
Ämneskategorier Radiofysik

Sammanfattning

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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