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Comparing voxel-based absorbed dosimetry methods in tumors, liver, lung, and at the liver-lung interface for (90)Y microsphere selective internal radiation therapy.

Mikell JK, Mahvash A, Siman W, Mourtada F, Kappadath SC - EJNMMI Phys (2015)

Bottom Line: Excluding 1, 2, and 3 cm of RL near the interface changed the resulting RL [Formula: see text] by -22, -38, and -48 %, respectively, for all VBDM.SK underestimates RL [Formula: see text] relative to MC whereas LD and SKD overestimate.RL [Formula: see text] is strongly influenced by the liver-lung interface.

View Article: PubMed Central - PubMed

Affiliation: Department of Imaging Physics, The University of Texas MD Anderson Cancer Center, 1155 Pressler St, Unit 1352, Houston, TX, 77030, USA.

ABSTRACT

Background: To assess differences between four different voxel-based dosimetry methods (VBDM) for tumor, liver, and lung absorbed doses following (90)Y microsphere selective internal radiation therapy (SIRT) based on (90)Y bremsstrahlung SPECT/CT, a secondary objective was to estimate the sensitivity of liver and lung absorbed doses due to differences in organ segmentation near the liver-lung interface.

Methods: Investigated VBDM were Monte Carlo (MC), soft-tissue kernel with density correction (SKD), soft-tissue kernel (SK), and local deposition (LD). Seventeen SIRT cases were analyzed. Mean absorbed doses ([Formula: see text]) were calculated for tumor, non-tumoral liver (NL), and right lung (RL). Simulations with various SPECT spatial resolutions (FHWMs) and multiple lung shunt fractions (LSs) estimated the accuracy of VBDM at the liver-lung interface. Sensitivity of patient RL and NL [Formula: see text] on segmentation near the interface was assessed by excluding portions near the interface.

Results: SKD, SK, and LD were within 5 % of MC for tumor and NL [Formula: see text]. LD and SKD overestimated RL [Formula: see text] compared to MC on average by 17 and 20 %, respectively; SK underestimated RL [Formula: see text] on average by -60 %. Simulations (20 mm FWHM, 20 % LS) showed that SKD, LD, and MC were within 10 % of the truth deep (>39 mm) in the lung; SK significantly underestimated the absorbed dose deep in the lung by approximately -70 %. All VBDM were within 10 % of truth deep (>12 mm) in the liver. Excluding 1, 2, and 3 cm of RL near the interface changed the resulting RL [Formula: see text] by -22, -38, and -48 %, respectively, for all VBDM. An average change of -7 % in the NL [Formula: see text] was realized when excluding 3 cm of NL from the interface. [Formula: see text] was realized when excluding 3 cm of NL from the interface.

Conclusions: SKD, SK, and LD are equivalent to MC for tumor and NL [Formula: see text]. SK underestimates RL [Formula: see text] relative to MC whereas LD and SKD overestimate. RL [Formula: see text] is strongly influenced by the liver-lung interface.

No MeSH data available.


Related in: MedlinePlus

A coronal plane through the RL and liver illustrating salient differences between the four different VBDM: MC (a), LD (b), SK (c), SKD (d). The tumor (shaded in cyan) is 5.2 cm in length in the cranial-caudal direction
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Fig3: A coronal plane through the RL and liver illustrating salient differences between the four different VBDM: MC (a), LD (b), SK (c), SKD (d). The tumor (shaded in cyan) is 5.2 cm in length in the cranial-caudal direction

Mentions: Figure 3 illustrates the salient differences in the apparent absorbed dose distribution stemming from the four VBDM; it shows the different absorbed dose calculations throughout the RL and liver on a coronal CT slice for a patient. The isodose curves deep within the liver were nearly identical for all four methods. The 20 Gy line extended furthest in the lung for SKD and LD followed by MC and then SK (least penetration into lung). The LD isodose distribution was very similar to the SKD distribution. There was an unequivocal qualitative difference in the lung absorbed dose distribution when SK was compared with MC, LD, or SKD, owing to the fact that SK assumes soft-tissue density of 1.04 g/cc regardless of the true density and material composition.Fig. 3


Comparing voxel-based absorbed dosimetry methods in tumors, liver, lung, and at the liver-lung interface for (90)Y microsphere selective internal radiation therapy.

Mikell JK, Mahvash A, Siman W, Mourtada F, Kappadath SC - EJNMMI Phys (2015)

A coronal plane through the RL and liver illustrating salient differences between the four different VBDM: MC (a), LD (b), SK (c), SKD (d). The tumor (shaded in cyan) is 5.2 cm in length in the cranial-caudal direction
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4538912&req=5

Fig3: A coronal plane through the RL and liver illustrating salient differences between the four different VBDM: MC (a), LD (b), SK (c), SKD (d). The tumor (shaded in cyan) is 5.2 cm in length in the cranial-caudal direction
Mentions: Figure 3 illustrates the salient differences in the apparent absorbed dose distribution stemming from the four VBDM; it shows the different absorbed dose calculations throughout the RL and liver on a coronal CT slice for a patient. The isodose curves deep within the liver were nearly identical for all four methods. The 20 Gy line extended furthest in the lung for SKD and LD followed by MC and then SK (least penetration into lung). The LD isodose distribution was very similar to the SKD distribution. There was an unequivocal qualitative difference in the lung absorbed dose distribution when SK was compared with MC, LD, or SKD, owing to the fact that SK assumes soft-tissue density of 1.04 g/cc regardless of the true density and material composition.Fig. 3

Bottom Line: Excluding 1, 2, and 3 cm of RL near the interface changed the resulting RL [Formula: see text] by -22, -38, and -48 %, respectively, for all VBDM.SK underestimates RL [Formula: see text] relative to MC whereas LD and SKD overestimate.RL [Formula: see text] is strongly influenced by the liver-lung interface.

View Article: PubMed Central - PubMed

Affiliation: Department of Imaging Physics, The University of Texas MD Anderson Cancer Center, 1155 Pressler St, Unit 1352, Houston, TX, 77030, USA.

ABSTRACT

Background: To assess differences between four different voxel-based dosimetry methods (VBDM) for tumor, liver, and lung absorbed doses following (90)Y microsphere selective internal radiation therapy (SIRT) based on (90)Y bremsstrahlung SPECT/CT, a secondary objective was to estimate the sensitivity of liver and lung absorbed doses due to differences in organ segmentation near the liver-lung interface.

Methods: Investigated VBDM were Monte Carlo (MC), soft-tissue kernel with density correction (SKD), soft-tissue kernel (SK), and local deposition (LD). Seventeen SIRT cases were analyzed. Mean absorbed doses ([Formula: see text]) were calculated for tumor, non-tumoral liver (NL), and right lung (RL). Simulations with various SPECT spatial resolutions (FHWMs) and multiple lung shunt fractions (LSs) estimated the accuracy of VBDM at the liver-lung interface. Sensitivity of patient RL and NL [Formula: see text] on segmentation near the interface was assessed by excluding portions near the interface.

Results: SKD, SK, and LD were within 5 % of MC for tumor and NL [Formula: see text]. LD and SKD overestimated RL [Formula: see text] compared to MC on average by 17 and 20 %, respectively; SK underestimated RL [Formula: see text] on average by -60 %. Simulations (20 mm FWHM, 20 % LS) showed that SKD, LD, and MC were within 10 % of the truth deep (>39 mm) in the lung; SK significantly underestimated the absorbed dose deep in the lung by approximately -70 %. All VBDM were within 10 % of truth deep (>12 mm) in the liver. Excluding 1, 2, and 3 cm of RL near the interface changed the resulting RL [Formula: see text] by -22, -38, and -48 %, respectively, for all VBDM. An average change of -7 % in the NL [Formula: see text] was realized when excluding 3 cm of NL from the interface. [Formula: see text] was realized when excluding 3 cm of NL from the interface.

Conclusions: SKD, SK, and LD are equivalent to MC for tumor and NL [Formula: see text]. SK underestimates RL [Formula: see text] relative to MC whereas LD and SKD overestimate. RL [Formula: see text] is strongly influenced by the liver-lung interface.

No MeSH data available.


Related in: MedlinePlus