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Developing a MLC modifier program to improve fiducial detection for MV/kV imaging during hypofractionated prostate volumetric modulated arc therapy.
J Appl Clin Med Phys 2019; 20(6):120-124JA

Abstract

PURPOSE

To develop an Eclipse plug-in (MLC_MODIFIER) that automatically modifies control points to expose fiducials obscured by MLC during VMAT, thereby facilitating tracking using periodic MV/kV imaging.

METHOD

Three-dimensional fiducial tracking was performed during VMAT by pairing short-arc (3°) MV digital tomosynthesis (DTS) images to triggered kV images. To evaluate MLC_MODIFIER efficacy, two cohorts of patients were considered. For first 12 patients, plans were manually edited to expose one fiducial marker. Next for 15 patients, plans were modified using MLC_MODIFIER script. MLC_MODIFIER evaluated MLC apertures at appropriate angles for marker visibility. Angles subtended by control points were compressed and low-dose "imaging" control points were inserted and exposed one marker with 1 cm margin. Patient's images were retrospectively reviewed to determine rate of MV registration failures. Failure categories were poor DTS image quality, MLC blockage of fiducials, or unknown reasons. Dosimetric differences in rectum, bladder, and urethra D1 cc, PTV maximum dose, and PTV dose homogeneity (PTV HI) were evaluated. Statistical significance was evaluated using Fisher's exact and Student's t test.

RESULT

Overall MV registration failures, failures due to poor image quality, MLC blockage, and unknown reasons were 33% versus 8.9% (P < 0.0001), 8% versus 6.4% (P < 0.05), 13.6% versus 0.1% (P < 0.0001), and 7.6% versus 2.4% (P < 0.0001) for manually edited and MLC_MODIFIER plans, respectively. PTV maximum and HI increased on average from unmodified plans by 2.1% and 0.3% (P < 0.004) and 22.0% and 3.3% (P < 0.004) for manually edited and MLC_MODIFIED plans, respectively. Changes in bladder, rectum, and urethra D1CC were similar for each method and less than 0.7%.

CONCLUSION

Increasing fiducial visibility via an automated process comprised of angular compression of control points and insertion of additional "imaging" control points is feasible. Degradation of plan quality is minimal. Fiducial detection and registration success rates are significantly improved compared to manually edited apertures.

Authors+Show Affiliations

Memorial Sloan Kettering Cancer Center, New York, NY, USA.Memorial Sloan Kettering Cancer Center, New York, NY, USA.Memorial Sloan Kettering Cancer Center, New York, NY, USA.Memorial Sloan Kettering Cancer Center, New York, NY, USA.Memorial Sloan Kettering Cancer Center, New York, NY, USA.Memorial Sloan Kettering Cancer Center, New York, NY, USA.Memorial Sloan Kettering Cancer Center, New York, NY, USA.Memorial Sloan Kettering Cancer Center, New York, NY, USA.Memorial Sloan Kettering Cancer Center, New York, NY, USA.Memorial Sloan Kettering Cancer Center, New York, NY, USA.

Pub Type(s)

Journal Article

Language

eng

PubMed ID

31116478

Citation

Happersett, Laura, et al. "Developing a MLC Modifier Program to Improve Fiducial Detection for MV/kV Imaging During Hypofractionated Prostate Volumetric Modulated Arc Therapy." Journal of Applied Clinical Medical Physics, vol. 20, no. 6, 2019, pp. 120-124.
Happersett L, Wang P, Zhang P, et al. Developing a MLC modifier program to improve fiducial detection for MV/kV imaging during hypofractionated prostate volumetric modulated arc therapy. J Appl Clin Med Phys. 2019;20(6):120-124.
Happersett, L., Wang, P., Zhang, P., Mechalakos, J., Li, G., Eley, E., ... Hunt, M. (2019). Developing a MLC modifier program to improve fiducial detection for MV/kV imaging during hypofractionated prostate volumetric modulated arc therapy. Journal of Applied Clinical Medical Physics, 20(6), pp. 120-124. doi:10.1002/acm2.12614.
Happersett L, et al. Developing a MLC Modifier Program to Improve Fiducial Detection for MV/kV Imaging During Hypofractionated Prostate Volumetric Modulated Arc Therapy. J Appl Clin Med Phys. 2019;20(6):120-124. PubMed PMID: 31116478.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Developing a MLC modifier program to improve fiducial detection for MV/kV imaging during hypofractionated prostate volumetric modulated arc therapy. AU - Happersett,Laura, AU - Wang,Ping, AU - Zhang,Pengpeng, AU - Mechalakos,James, AU - Li,Guang, AU - Eley,Eleanor, AU - Zelefsky,Michael, AU - Mageras,Gig, AU - Damato,Antonio L, AU - Hunt,Margie, Y1 - 2019/05/22/ PY - 2019/01/24/received PY - 2019/04/03/revised PY - 2019/04/22/accepted PY - 2019/5/23/pubmed PY - 2019/5/23/medline PY - 2019/5/23/entrez KW - MV/kV imaging KW - fiducial tracking KW - image-guided radiotherapy KW - motion management KW - prostate SP - 120 EP - 124 JF - Journal of applied clinical medical physics JO - J Appl Clin Med Phys VL - 20 IS - 6 N2 - PURPOSE: To develop an Eclipse plug-in (MLC_MODIFIER) that automatically modifies control points to expose fiducials obscured by MLC during VMAT, thereby facilitating tracking using periodic MV/kV imaging. METHOD: Three-dimensional fiducial tracking was performed during VMAT by pairing short-arc (3°) MV digital tomosynthesis (DTS) images to triggered kV images. To evaluate MLC_MODIFIER efficacy, two cohorts of patients were considered. For first 12 patients, plans were manually edited to expose one fiducial marker. Next for 15 patients, plans were modified using MLC_MODIFIER script. MLC_MODIFIER evaluated MLC apertures at appropriate angles for marker visibility. Angles subtended by control points were compressed and low-dose "imaging" control points were inserted and exposed one marker with 1 cm margin. Patient's images were retrospectively reviewed to determine rate of MV registration failures. Failure categories were poor DTS image quality, MLC blockage of fiducials, or unknown reasons. Dosimetric differences in rectum, bladder, and urethra D1 cc, PTV maximum dose, and PTV dose homogeneity (PTV HI) were evaluated. Statistical significance was evaluated using Fisher's exact and Student's t test. RESULT: Overall MV registration failures, failures due to poor image quality, MLC blockage, and unknown reasons were 33% versus 8.9% (P < 0.0001), 8% versus 6.4% (P < 0.05), 13.6% versus 0.1% (P < 0.0001), and 7.6% versus 2.4% (P < 0.0001) for manually edited and MLC_MODIFIER plans, respectively. PTV maximum and HI increased on average from unmodified plans by 2.1% and 0.3% (P < 0.004) and 22.0% and 3.3% (P < 0.004) for manually edited and MLC_MODIFIED plans, respectively. Changes in bladder, rectum, and urethra D1CC were similar for each method and less than 0.7%. CONCLUSION: Increasing fiducial visibility via an automated process comprised of angular compression of control points and insertion of additional "imaging" control points is feasible. Degradation of plan quality is minimal. Fiducial detection and registration success rates are significantly improved compared to manually edited apertures. SN - 1526-9914 UR - https://www.unboundmedicine.com/medline/citation/31116478/Developing_a_MLC_modifier_program_to_improve_fiducial_detection_for_MV/kV_imaging_during_hypofractionated_prostate_volumetric_modulated_arc_therapy L2 - https://doi.org/10.1002/acm2.12614 DB - PRIME DP - Unbound Medicine ER -