Caren van Roekel

33 Radioembolization ( ) = ( − 0,2) + ( + ) ( ) = ( ( ) ∗ ( )) 50 ( ) = ( ) ( ) ( ) ( ) ⁄ ( ) = ( ) ∗ ([ ∗ ( )] + ( )) 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. The MIRD method is especially useful for radiation segmentectomy, where a large absorbed dose (e.g. 200 Gy) is administered to a limited target volume in order to ablate both the tumorous and non-tumorous liver tissue within that target volume, while sparing the untreated part of the liver (52). 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 phase I dose escalation study, a maximum tolerable absorbed dose for the whole liver is set at 60 Gy (62). 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: ( ) = ( − 0,2) + ( + ) ( ) = ( ( ) ∗ ( )) 50 ( ) = ( ) ( ) ( ) ( ) ( ) = ( ) ∗ ([ ∗ ( )] + ( )) 49,670 ∗ (1 − ℎ ) ( ) = ℎ ( ) ∗ 3780 ( ) ( ) = ℎ ( ) ∗ 3780 ( ) ( ) = ( ( ) ∗ ( )) 50 ( ) ( ) = ( ( ) ∗ ( )) 16 ( ) ( ) = ( ) ∗ ([ ∗ ( )] + ℎ ℎ ( )) 49.67 ∗ (1 − ℎ ) Another method, that can be used for pretreatment dosimetry for both resin and glass spheres, 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 99m Tc-MAA SPECT/ CT. The tumor to nontumor (T/N) ratio on MAA is calculated as: = √ ∗ √ ∗ ) + √ ∗ = 0.2024 ∗ ℎ ℎ ( ) 0,725 ∗ ℎ ( ) 0,425 ( ) = ( − 0,2) + ( + ) ( ) = ( ( ) ∗ ( )) 50 ( ) = ( ) ( ) ( ) ( ) ⁄ ( ) = ( ) ∗ ([ ∗ ( )] + ( )) 49,670 ∗ (1 − ℎ ) ( ) = ℎ ( ) ∗ 3780 ( ) ( ) = ℎ ( ) ∗ 3780 ( ) The formula for the IA is: ∗ . , ℎ , , ) ( ∗ ( ( ( ) ∗ ( 4 , ∗ 1 ( ) The partition method does correct for the difference in tumor and nontumor dose. Limitations of this model are that it is more time-consuming and that it 2