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Improvement of I'mRT MatriXX in terms of spatial resolution and large area acquisition for patient-specific intensity-modulated radiotherapy verification.

Oinam AS, Singh L, Sharma SC, Goswami P - J Med Phys (2009)

Bottom Line: After an analysis of the dose linearity and spatial resolution of this 2D array (I'mRT MatriXX), the signal sampling time of 200 ms was selected for data acquisition.Multiple-sequence acquisitions at the nearest 4 positions with the shift of half of the distance between the centers of two adjacent ion chambers increase the spatial resolution up to four times when used with this I'mRT MatriXX.It is found that the convolution method can also be used to improve the IMRT dose verification with the same parameters of the passing criteria significantly, viz., up to 99.87% agreement, by smoothening the treatment planning system profile.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiotherapy, PGIMER, Chandigarh, India.

ABSTRACT
2D array of ionization chambers can be used for both absolute and relative dose verification of patient-specific intensity-modulated radiotherapy (IMRT) quality assurance. After an analysis of the dose linearity and spatial resolution of this 2D array (I'mRT MatriXX), the signal sampling time of 200 ms was selected for data acquisition. Multiple-sequence acquisitions at the nearest 4 positions with the shift of half of the distance between the centers of two adjacent ion chambers increase the spatial resolution up to four times when used with this I'mRT MatriXX. IMRT verification of head-and-neck case, which requires a large area for dosimetric verification, can be done with limited size of 24x24 cm(2), depending on the user requirements. It is found that the convolution method can also be used to improve the IMRT dose verification with the same parameters of the passing criteria significantly, viz., up to 99.87% agreement, by smoothening the treatment planning system profile.

No MeSH data available.


2D dose profile comparison between convolved TPS profile and I'mRT MatriXX profile. (a) 1D profile comparison between I'mRT MatriXX and convolved TPS along x-axis and (b) 1D profile comparison between I'mRT MatriXX and convolved TPS along y-axis. Gamma histogram (c) of gamma values (d) depicted with color spectrum within the region of interest of 2D plane using delta dose 3% and delta distance 3 mm
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Figure 0008: 2D dose profile comparison between convolved TPS profile and I'mRT MatriXX profile. (a) 1D profile comparison between I'mRT MatriXX and convolved TPS along x-axis and (b) 1D profile comparison between I'mRT MatriXX and convolved TPS along y-axis. Gamma histogram (c) of gamma values (d) depicted with color spectrum within the region of interest of 2D plane using delta dose 3% and delta distance 3 mm

Mentions: Figure 8 shows the results of IMRT verification using convolution technique. Here the TPS 2D plane dose profile T(x,y) was convolved with a point spread function, also called Gaussian function, G(x,y), rather than using the rectangular lateral response function of Poppe et al.[45] This scattering kernel is generated to conform to the shape of lateral response profile of a single ion chamber. Then, this convolved profile was compared with I'mRT MatriXX–measured data after interpolating to a higher resolution of 1×1 mm2 grid size. Figure 8A shows 1D profile comparison between convolved TPS 2D profile and interpolated 2D profile of I'mRT MatriXX along x-axis. Similarly Figure 8B shows 1D profiles comparison along y-axis. It is clearly observed that convolved TPS profile is very close to I'mRT MatriXX-measured data. Figure 8C shows the gamma histogram calculated using ΔD of 3% and Δd of 3 mm. In the region of interest as shown in Figure 8D, the population of pixel of the gamma values, which is depicted by color spectrum within the signal range from 0 to 1, was 99.86%. This shows drastic improvement in dosimetric verification of IMRT for routine patient-specific quality assurance using convolution technique.


Improvement of I'mRT MatriXX in terms of spatial resolution and large area acquisition for patient-specific intensity-modulated radiotherapy verification.

Oinam AS, Singh L, Sharma SC, Goswami P - J Med Phys (2009)

2D dose profile comparison between convolved TPS profile and I'mRT MatriXX profile. (a) 1D profile comparison between I'mRT MatriXX and convolved TPS along x-axis and (b) 1D profile comparison between I'mRT MatriXX and convolved TPS along y-axis. Gamma histogram (c) of gamma values (d) depicted with color spectrum within the region of interest of 2D plane using delta dose 3% and delta distance 3 mm
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2807681&req=5

Figure 0008: 2D dose profile comparison between convolved TPS profile and I'mRT MatriXX profile. (a) 1D profile comparison between I'mRT MatriXX and convolved TPS along x-axis and (b) 1D profile comparison between I'mRT MatriXX and convolved TPS along y-axis. Gamma histogram (c) of gamma values (d) depicted with color spectrum within the region of interest of 2D plane using delta dose 3% and delta distance 3 mm
Mentions: Figure 8 shows the results of IMRT verification using convolution technique. Here the TPS 2D plane dose profile T(x,y) was convolved with a point spread function, also called Gaussian function, G(x,y), rather than using the rectangular lateral response function of Poppe et al.[45] This scattering kernel is generated to conform to the shape of lateral response profile of a single ion chamber. Then, this convolved profile was compared with I'mRT MatriXX–measured data after interpolating to a higher resolution of 1×1 mm2 grid size. Figure 8A shows 1D profile comparison between convolved TPS 2D profile and interpolated 2D profile of I'mRT MatriXX along x-axis. Similarly Figure 8B shows 1D profiles comparison along y-axis. It is clearly observed that convolved TPS profile is very close to I'mRT MatriXX-measured data. Figure 8C shows the gamma histogram calculated using ΔD of 3% and Δd of 3 mm. In the region of interest as shown in Figure 8D, the population of pixel of the gamma values, which is depicted by color spectrum within the signal range from 0 to 1, was 99.86%. This shows drastic improvement in dosimetric verification of IMRT for routine patient-specific quality assurance using convolution technique.

Bottom Line: After an analysis of the dose linearity and spatial resolution of this 2D array (I'mRT MatriXX), the signal sampling time of 200 ms was selected for data acquisition.Multiple-sequence acquisitions at the nearest 4 positions with the shift of half of the distance between the centers of two adjacent ion chambers increase the spatial resolution up to four times when used with this I'mRT MatriXX.It is found that the convolution method can also be used to improve the IMRT dose verification with the same parameters of the passing criteria significantly, viz., up to 99.87% agreement, by smoothening the treatment planning system profile.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiotherapy, PGIMER, Chandigarh, India.

ABSTRACT
2D array of ionization chambers can be used for both absolute and relative dose verification of patient-specific intensity-modulated radiotherapy (IMRT) quality assurance. After an analysis of the dose linearity and spatial resolution of this 2D array (I'mRT MatriXX), the signal sampling time of 200 ms was selected for data acquisition. Multiple-sequence acquisitions at the nearest 4 positions with the shift of half of the distance between the centers of two adjacent ion chambers increase the spatial resolution up to four times when used with this I'mRT MatriXX. IMRT verification of head-and-neck case, which requires a large area for dosimetric verification, can be done with limited size of 24x24 cm(2), depending on the user requirements. It is found that the convolution method can also be used to improve the IMRT dose verification with the same parameters of the passing criteria significantly, viz., up to 99.87% agreement, by smoothening the treatment planning system profile.

No MeSH data available.