Comparison of three dose calculation methodologies for 90-Y microspheres radioembolization

• Published in: Physica medica Vol. 32; pp. 294 - 295
• Main Authors: Antunes, V, Santos, J.A.M
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.09.2016
• Subjects: Radiology
• ISSN: 1120-1797; 1724-191X
• DOI: 10.1016/j.ejmp.2016.07.127

Introduction According to 2013/59/Euratom BSS, for all medical exposure of patients for radiotherapeutic purposes, including Nuclear Medicine, doses in target volumes shall be individually planned. Furthermore, doses to non-target volumes (e.g organs-at-risk) shall be as-low-as-reasonably-achievable and consistent with the intended radiotherapeutic purposes. For Y-90 microspheres radioembolization, three methods of activity calculation to be administered are usually used: empirical, body-surface-area (BSA) and partition methods. Purpose Accuracy and effectiveness of dose distribution calculation in the liver was compared using these three methods. Materials and methods A Tc-99m:MAA SPECT/CT image is used to predict microspheres distribution, possible gastro-intestinal implication and to estimate dose distribution after radioembolization. A 90-Y SPECT/CT image is acquired after the radioembolization and compared with the previous Tc-99m:MAA images. Dose calculation using the three methods and based in the 99m-Tc and 90-Y SPECT/CT images were systematically evaluated for 15 patients. Results Administered activities based on the three methods can show large variations for the same patient, leading to very different dose distributions (e.g. 70% in the tumor and healthy liver parenchyma). Different Tc-99m:MAA and Y-90 microspheres distribution also occur and is a major problem which can imply healthy liver parenchyma irradiation higher than the maximum dose recommendation (70 Gy). Conclusion Empirical and BSA methods are not suitable for a minimal acceptable accuracy of dose distribution calculation (10–20%). Although the partition model is the most accurate, different Tc-99m:MAA and Y-90 microspheres distribution leads also to large errors in the final dosimetry calculation. New approaches, such as the use of 99m-Tc labeled microspheres instead of Tc-99m:MAA, should be pursued. Disclosure The authors have no relevant financial or non-financial relationships to disclose.