Caren van Roekel

271 Discussion intrahepatic microsphere distribution throughout the treated portion of the liver, and an assumed yield of 50 Gy per GBq 90 Y per kilogram of liver tissue. This method also does not take into account the degree of tumor uptake, nor does it account for fractional or total tumor burden. The formula for the IA is: ( ) = ( ) ∗ ([ ∗ ( )] + ( )) 49,670 ∗ (1 − ℎ ) ( ) = ℎ ( ) ∗ 3780 ( ) ( ) = ℎ ( ) ∗ 3780 ( ) ( ) = ( ( ) ∗ ( )) 50 ( ) ( ) = ( ( ) ∗ ( )) 16 ( ) ( ) = ( ) ∗ ([ ∗ ( )] + ℎ ℎ ( )) 49.67 ∗ (1 − ℎ ) where M Target is the mass of the target volume. For 166 Ho, a method comparable to the MIRD method for 90 Y is currently used. Based on findings of the HEPAR I trial, a maximum tolerable absorbed dose for the whole liver was set at 60 Gy (80). The absorbed dose in Gy delivered by 1 GBq in 1 kg tissue is 15.87 Gy for 166 Ho, under the assumption of homogenous distribution in the target volume and absorption of all energy within that volume. The formula for the IA is: = ( ) ( ) ( ) ( ) ⁄ ( ) = ( ) ∗ ([ ∗ ( )] + ( )) 49,670 ∗ (1 − ℎ ) ( ) = ℎ ( ) ∗ 3780 ( ) ( ) = ℎ ( ) ∗ 3780 ( ) ( ) = ( ( ) ∗ ( )) 50 ( ) ( ) = ( ( ) ∗ ( )) 16 ( ) ( ) = ( ) ∗ ([ ∗ ( )] + ℎ ℎ ( )) 49.67 ∗ (1 − ℎ ) Another method that can be used for personalized dosimetry is the partition model. In general, the tumor and healthy liver tissue are delineated on anatomical imaging modalities. The anticipated activity in these delineated compartments is calculated on pre-treatment 99m Tc-MAA SPECT/CT (or 166 Ho- SPECT/CT). The tumor to non-tumor (T/N) ratio based on 99m Tc-MAA or 166 Ho- scout is calculated as: = √ ∗ √ ∗ ) + √ ∗ = 0.2024 ∗ ℎ ℎ ( ) 0,725 ∗ ℎ ( ) 0,425 ( ) = ( − 0,2) + ( + ) ( ) = ( ( ) ∗ ( )) 50 ( ) = ( ) ( ) ( ) ( ) ⁄ ( ) = ( ) ∗ ([ ∗ ( )] + ( )) 49,670 ∗ (1 − ℎ ) ( ) = ℎ ( ) ∗ 3780 ( ) The formula for the injected activity (IA) is: = 0.2024 ∗ ℎ ℎ ( ) 0,725 ∗ ℎ ( ) 0,425 ( ) = ( − 0,2) + ( + ) ( ) = ( ( ) ∗ ( )) 50 ( ) = ( ) ( ) ( ) ( ) ⁄ ( ) = ( ) ∗ ([ ∗ ( )] + ( )) 49,670 ∗ ( ) = ℎ ( ) ∗ 3780 ( ) ( ) = ℎ ( ) ∗ 3780 ( ) ( ) = ( ( ) ∗ ( )) 50 ( ) ( ) = ( ( ) ∗ ( )) 16 ( ) ( ) = ( ) ∗ ([ ∗ ( )] + ℎ ℎ ( )) 49.67 10