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Potentials of on-line repositioning based on implanted fiducial markers and electronic portal imaging in prostate cancer radiotherapy.

Graf R, Wust P, Budach V, Boehmer D - Radiat Oncol (2009)

Bottom Line: The resulting total error suggests margins of 7.0 mm (LR), 9.5 mm (SI) and 9.5 mm (AP) between clinical target volume (CTV) and planning target volume (PTV).After correction once a week the margins were lowered to 6.7, 8.2 and 8.7 mm and furthermore down to 4.9, 5.1 and 4.8 mm after correcting every treatment day.Performing on-line setup correction using implanted radioopaque markers and megavoltage radiography results in reduced treatment margins depending on the online imaging protocol (once a week or more frequently).

View Article: PubMed Central - HTML - PubMed

Affiliation: Charité Universitätsmedizin Berlin, Department of Radiotherapy, Germany. reinhold.graf@charite.de

ABSTRACT

Background: To evaluate the benefit of an on-line correction protocol based on implanted markers and weekly portal imaging in external beam radiotherapy of prostate cancer. To compare the use of bony anatomy versus implanted markers for calculation of setup-error plus/minus prostate movement. To estimate the error reduction (and the corresponding margin reduction) by reducing the total error to 3 mm once a week, three times per week or every treatment day.

Methods: 23 patients had three to five, 2.5 mm Ø spherical gold markers transrectally inserted into the prostate before radiotherapy. Verification and correction of treatment position by analysis of orthogonal portal images was performed on a weekly basis. We registered with respect to the bony contours (setup error) and to the marker position (prostate motion) and determined the total error. The systematic and random errors are specified. Positioning correction was applied with a threshold of 5 mm displacement.

Results: The systematic error (1 standard deviation [SD]) in left-right (LR), superior-inferior (SI) and anterior-posterior (AP) direction contributes for the setup 1.6 mm, 2.1 mm and 2.4 mm and for prostate motion 1.1 mm, 1.9 mm and 2.3 mm. The random error (1 SD) in LR, SI and AP direction amounts for the setup 2.3 mm, 2.7 mm and 2.7 mm and for motion 1.4 mm, 2.3 mm and 2.7 mm. The resulting total error suggests margins of 7.0 mm (LR), 9.5 mm (SI) and 9.5 mm (AP) between clinical target volume (CTV) and planning target volume (PTV). After correction once a week the margins were lowered to 6.7, 8.2 and 8.7 mm and furthermore down to 4.9, 5.1 and 4.8 mm after correcting every treatment day.

Conclusion: Prostate movement relative to adjacent bony anatomy is significant and contributes substantially to the target position variability. Performing on-line setup correction using implanted radioopaque markers and megavoltage radiography results in reduced treatment margins depending on the online imaging protocol (once a week or more frequently).

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Related in: MedlinePlus

Measured deviations in LR, SI and AP directions in a box plot format, showing the mean values (black squares), the median values (lines in the box) and the 10% (lower horizontal line), 25% (bottom of box), 75% (top of box) and 90% (upper horizontal line) percentile split in setup variability, prostate position variability and total error.
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Figure 3: Measured deviations in LR, SI and AP directions in a box plot format, showing the mean values (black squares), the median values (lines in the box) and the 10% (lower horizontal line), 25% (bottom of box), 75% (top of box) and 90% (upper horizontal line) percentile split in setup variability, prostate position variability and total error.

Mentions: As summarised in Table 1 we analysed all 184 fractions together and determined the displacements of the isocenter relative the bony anatomy (setup error), the displacement of the markers relative to the bony structures (prostate motion) and the displacement of the isocenter relative to the markers (combined or total targeting error). Figure 3 shows the measured deviations in a box plot format, indicating mean values, median values and selected percentiles from 10 to 90% (10%, 25%, 75%, 90%) in LR, SI and AP directions. The observed errors were greatest in the AP direction, where a range of 13 mm is found for the total deviation of the target (-7 to +6 mm) for 80% of the controls. The extremes observed in internal target motion were 8 mm in AP and 7 mm in SI direction.


Potentials of on-line repositioning based on implanted fiducial markers and electronic portal imaging in prostate cancer radiotherapy.

Graf R, Wust P, Budach V, Boehmer D - Radiat Oncol (2009)

Measured deviations in LR, SI and AP directions in a box plot format, showing the mean values (black squares), the median values (lines in the box) and the 10% (lower horizontal line), 25% (bottom of box), 75% (top of box) and 90% (upper horizontal line) percentile split in setup variability, prostate position variability and total error.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2683853&req=5

Figure 3: Measured deviations in LR, SI and AP directions in a box plot format, showing the mean values (black squares), the median values (lines in the box) and the 10% (lower horizontal line), 25% (bottom of box), 75% (top of box) and 90% (upper horizontal line) percentile split in setup variability, prostate position variability and total error.
Mentions: As summarised in Table 1 we analysed all 184 fractions together and determined the displacements of the isocenter relative the bony anatomy (setup error), the displacement of the markers relative to the bony structures (prostate motion) and the displacement of the isocenter relative to the markers (combined or total targeting error). Figure 3 shows the measured deviations in a box plot format, indicating mean values, median values and selected percentiles from 10 to 90% (10%, 25%, 75%, 90%) in LR, SI and AP directions. The observed errors were greatest in the AP direction, where a range of 13 mm is found for the total deviation of the target (-7 to +6 mm) for 80% of the controls. The extremes observed in internal target motion were 8 mm in AP and 7 mm in SI direction.

Bottom Line: The resulting total error suggests margins of 7.0 mm (LR), 9.5 mm (SI) and 9.5 mm (AP) between clinical target volume (CTV) and planning target volume (PTV).After correction once a week the margins were lowered to 6.7, 8.2 and 8.7 mm and furthermore down to 4.9, 5.1 and 4.8 mm after correcting every treatment day.Performing on-line setup correction using implanted radioopaque markers and megavoltage radiography results in reduced treatment margins depending on the online imaging protocol (once a week or more frequently).

View Article: PubMed Central - HTML - PubMed

Affiliation: Charité Universitätsmedizin Berlin, Department of Radiotherapy, Germany. reinhold.graf@charite.de

ABSTRACT

Background: To evaluate the benefit of an on-line correction protocol based on implanted markers and weekly portal imaging in external beam radiotherapy of prostate cancer. To compare the use of bony anatomy versus implanted markers for calculation of setup-error plus/minus prostate movement. To estimate the error reduction (and the corresponding margin reduction) by reducing the total error to 3 mm once a week, three times per week or every treatment day.

Methods: 23 patients had three to five, 2.5 mm Ø spherical gold markers transrectally inserted into the prostate before radiotherapy. Verification and correction of treatment position by analysis of orthogonal portal images was performed on a weekly basis. We registered with respect to the bony contours (setup error) and to the marker position (prostate motion) and determined the total error. The systematic and random errors are specified. Positioning correction was applied with a threshold of 5 mm displacement.

Results: The systematic error (1 standard deviation [SD]) in left-right (LR), superior-inferior (SI) and anterior-posterior (AP) direction contributes for the setup 1.6 mm, 2.1 mm and 2.4 mm and for prostate motion 1.1 mm, 1.9 mm and 2.3 mm. The random error (1 SD) in LR, SI and AP direction amounts for the setup 2.3 mm, 2.7 mm and 2.7 mm and for motion 1.4 mm, 2.3 mm and 2.7 mm. The resulting total error suggests margins of 7.0 mm (LR), 9.5 mm (SI) and 9.5 mm (AP) between clinical target volume (CTV) and planning target volume (PTV). After correction once a week the margins were lowered to 6.7, 8.2 and 8.7 mm and furthermore down to 4.9, 5.1 and 4.8 mm after correcting every treatment day.

Conclusion: Prostate movement relative to adjacent bony anatomy is significant and contributes substantially to the target position variability. Performing on-line setup correction using implanted radioopaque markers and megavoltage radiography results in reduced treatment margins depending on the online imaging protocol (once a week or more frequently).

Show MeSH
Related in: MedlinePlus