Limits...
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

Schematic geometry of the simulations for the liver-lung interface with uniform activity in the slab representing either the liver (a) or lung (b). Arbitrary LS were achieved through superposition of individual VBDM for both liver and lung. Finite spatial resolution was modeled through Gaussian blurring. Data was averaged in the orange region to generate 1D absorbed dose profiles along the dashed line
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Fig2: Schematic geometry of the simulations for the liver-lung interface with uniform activity in the slab representing either the liver (a) or lung (b). Arbitrary LS were achieved through superposition of individual VBDM for both liver and lung. Finite spatial resolution was modeled through Gaussian blurring. Data was averaged in the orange region to generate 1D absorbed dose profiles along the dashed line

Mentions: Simulations were performed to estimate errors in the absorbed dose calculations around the liver-lung interface for the different VBDM as a function of spatial resolution and LS. We used a slab geometry with multiple spatial resolutions and LS; this simple simulation had two compartments (liver and lung) shown in Fig. 2 and does not use patient data. We placed a uniform amount of activity in the liver compartment representing a true activity distribution. To simulate limited spatial resolution, the activity in the liver was convolved with a Gaussian FWHM of 10 or 20 mm causing spill-out of the liver and spill-in to the lung. MC, SK, SKD, and LD voxel-level absorbed doses were then calculated on the three activity distributions (0, 10, 20 mm FWHM) and were normalized to the input activity. A similar process was carried out for the lung.Fig. 2


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)

Schematic geometry of the simulations for the liver-lung interface with uniform activity in the slab representing either the liver (a) or lung (b). Arbitrary LS were achieved through superposition of individual VBDM for both liver and lung. Finite spatial resolution was modeled through Gaussian blurring. Data was averaged in the orange region to generate 1D absorbed dose profiles along the dashed line
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Fig2: Schematic geometry of the simulations for the liver-lung interface with uniform activity in the slab representing either the liver (a) or lung (b). Arbitrary LS were achieved through superposition of individual VBDM for both liver and lung. Finite spatial resolution was modeled through Gaussian blurring. Data was averaged in the orange region to generate 1D absorbed dose profiles along the dashed line
Mentions: Simulations were performed to estimate errors in the absorbed dose calculations around the liver-lung interface for the different VBDM as a function of spatial resolution and LS. We used a slab geometry with multiple spatial resolutions and LS; this simple simulation had two compartments (liver and lung) shown in Fig. 2 and does not use patient data. We placed a uniform amount of activity in the liver compartment representing a true activity distribution. To simulate limited spatial resolution, the activity in the liver was convolved with a Gaussian FWHM of 10 or 20 mm causing spill-out of the liver and spill-in to the lung. MC, SK, SKD, and LD voxel-level absorbed doses were then calculated on the three activity distributions (0, 10, 20 mm FWHM) and were normalized to the input activity. A similar process was carried out for the lung.Fig. 2

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