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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.


Comparison of 2D plane dose profiles of peak test between unprocessed profile of I'mRT MatriXX (A), processed profile of I'mRT MatriXX (B) and TPS (C). D represents the 1D profile comparison between TPS and unprocessed matrix data. E represents the 1D profile comparison between TPS and processed matrix data of I'mRT MatriXX with 4 adjacent shifts, showing the improvement of spatial resolution by detecting the 2.5 mm MLC gap, which cannot be resolved by unprocessed matrix data (D). Uninterpolated matrix data of processed profile (F) shows the increase of spatial resolution to up to 4 times as compared with that of unprocessed profile (G).
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Figure 0006: Comparison of 2D plane dose profiles of peak test between unprocessed profile of I'mRT MatriXX (A), processed profile of I'mRT MatriXX (B) and TPS (C). D represents the 1D profile comparison between TPS and unprocessed matrix data. E represents the 1D profile comparison between TPS and processed matrix data of I'mRT MatriXX with 4 adjacent shifts, showing the improvement of spatial resolution by detecting the 2.5 mm MLC gap, which cannot be resolved by unprocessed matrix data (D). Uninterpolated matrix data of processed profile (F) shows the increase of spatial resolution to up to 4 times as compared with that of unprocessed profile (G).

Mentions: Figure 5A shows the comparison of a single-field IMRT verification using multiple-sequence acquisition technique with the conventional method of IMRT verification. The multiple IMRT data was acquired at four different positions by shifting the 2D array by half the distance between the two adjacent chambers. The matrix elements of these four matrices were merged and suffled to obtain the processed profiles. Figure 5A shows the comparison of 1D profiles amongst the 2D plane dose profiles of TPS [Figure 5B], processed profile [Figure 5C] using multiple-acquisition technique and unprocessed profile [Figure 5D] with the conventional IMRT verification method. This showed the improvement of processed profile, which is closer to TPS profile. The same improvement was also observed with gamma evaluation histograms [Figures 5D, 5E]. The gamma evaluation of TPS profile versus processed 2D profile using 3% dose tolerance (ΔD) and 3 mm distance-to-dose agreement (Δd) within a region of interest reveals that the pixel population within the signal range from 0 to 1.0 was 97.85% as compared with 92.98% for TPS profile versus unprocessed 2D plane dose profile within the same region of interest. Figure 6 shows the comparison between 2D plane profiles of TPS versus processed profile and TPS profile versus unprocessed profile for benchmark IMRT field (peak test; dynamic MLC dose delivery file which is generated with different MLC gaps, ranging from 2.5 to 15 mm in steps of 2.5 mm). This figure shows improvement in resolution up to 4 times of conventional IMRT verification with I'mRT MatriXX. The improvement in dosimetry verification can be clearly observed in Figures 6D and 6E, which show that processed 1D profile is closer to TPS profile [Figure 6D] as compared to unprocessed 1D profile [Figure 6E]. The gamma evaluation of TPS profile against processed 2D profile using ΔD of 5% and Δd of 3 mm within a region of interest calculates the pixel population within the signal range from 0 to 1.0 as 94.32% as compared with 58.29% for TPS profile versus unprocessed 2D plane dose profile. So the multiple-sequence acquisition technique improves the spatial resolution of IMRT dose verification, as reported by Emialano et al.[3]


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)

Comparison of 2D plane dose profiles of peak test between unprocessed profile of I'mRT MatriXX (A), processed profile of I'mRT MatriXX (B) and TPS (C). D represents the 1D profile comparison between TPS and unprocessed matrix data. E represents the 1D profile comparison between TPS and processed matrix data of I'mRT MatriXX with 4 adjacent shifts, showing the improvement of spatial resolution by detecting the 2.5 mm MLC gap, which cannot be resolved by unprocessed matrix data (D). Uninterpolated matrix data of processed profile (F) shows the increase of spatial resolution to up to 4 times as compared with that of unprocessed profile (G).
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 0006: Comparison of 2D plane dose profiles of peak test between unprocessed profile of I'mRT MatriXX (A), processed profile of I'mRT MatriXX (B) and TPS (C). D represents the 1D profile comparison between TPS and unprocessed matrix data. E represents the 1D profile comparison between TPS and processed matrix data of I'mRT MatriXX with 4 adjacent shifts, showing the improvement of spatial resolution by detecting the 2.5 mm MLC gap, which cannot be resolved by unprocessed matrix data (D). Uninterpolated matrix data of processed profile (F) shows the increase of spatial resolution to up to 4 times as compared with that of unprocessed profile (G).
Mentions: Figure 5A shows the comparison of a single-field IMRT verification using multiple-sequence acquisition technique with the conventional method of IMRT verification. The multiple IMRT data was acquired at four different positions by shifting the 2D array by half the distance between the two adjacent chambers. The matrix elements of these four matrices were merged and suffled to obtain the processed profiles. Figure 5A shows the comparison of 1D profiles amongst the 2D plane dose profiles of TPS [Figure 5B], processed profile [Figure 5C] using multiple-acquisition technique and unprocessed profile [Figure 5D] with the conventional IMRT verification method. This showed the improvement of processed profile, which is closer to TPS profile. The same improvement was also observed with gamma evaluation histograms [Figures 5D, 5E]. The gamma evaluation of TPS profile versus processed 2D profile using 3% dose tolerance (ΔD) and 3 mm distance-to-dose agreement (Δd) within a region of interest reveals that the pixel population within the signal range from 0 to 1.0 was 97.85% as compared with 92.98% for TPS profile versus unprocessed 2D plane dose profile within the same region of interest. Figure 6 shows the comparison between 2D plane profiles of TPS versus processed profile and TPS profile versus unprocessed profile for benchmark IMRT field (peak test; dynamic MLC dose delivery file which is generated with different MLC gaps, ranging from 2.5 to 15 mm in steps of 2.5 mm). This figure shows improvement in resolution up to 4 times of conventional IMRT verification with I'mRT MatriXX. The improvement in dosimetry verification can be clearly observed in Figures 6D and 6E, which show that processed 1D profile is closer to TPS profile [Figure 6D] as compared to unprocessed 1D profile [Figure 6E]. The gamma evaluation of TPS profile against processed 2D profile using ΔD of 5% and Δd of 3 mm within a region of interest calculates the pixel population within the signal range from 0 to 1.0 as 94.32% as compared with 58.29% for TPS profile versus unprocessed 2D plane dose profile. So the multiple-sequence acquisition technique improves the spatial resolution of IMRT dose verification, as reported by Emialano et al.[3]

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.