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Spot Weight Adaptation for Moving Target in Spot Scanning Proton Therapy.

Morel P, Wu X, Blin G, Vialette S, Flynn R, Hyer D, Wang D - Front Oncol (2015)

Bottom Line: The impact of the real-time patient/target position tracking or prediction was also investigated.Larger errors in patient/target position tracking or prediction led to worse final target coverage; an error of 3 mm or smaller in patient/target position tracking is preferred.The successful implementation of this method would rely on accurate monitoring or prediction of patient/target motion.

View Article: PubMed Central - PubMed

Affiliation: Laboratoire Informatique Gaspard Monge (LIGM), UMR CNRS 8049, Université Paris-Est , Paris , France.

ABSTRACT

Purpose: This study describes a real-time spot weight adaptation method in spot-scanning proton therapy for moving target or moving patient, so that the resultant dose distribution closely matches the planned dose distribution.

Materials and methods: The method proposed in this study adapts the weight (MU) of the delivering pencil beam to that of the target spot; it will actually hit during patient/target motion. The target spot that a certain delivering pencil beam may hit relies on patient monitoring and/or motion modeling using four-dimensional (4D) CT. After the adapted delivery, the required total weight [Monitor Unit (MU)] for this target spot is then subtracted from the planned value. With continuous patient motion and continuous spot scanning, the planned doses to all target spots will eventually be all fulfilled. In a proof-of-principle test, a lung case was presented with realistic temporal and motion parameters; the resultant dose distribution using spot weight adaptation was compared to that without using this method. The impact of the real-time patient/target position tracking or prediction was also investigated.

Results: For moderate motion (i.e., mean amplitude 0.5 cm), D95% to the planning target volume (PTV) was only 81.5% of the prescription (RX) dose; with spot weight adaptation PTV D95% achieves 97.7% RX. For large motion amplitude (i.e., 1.5 cm), without spot weight adaptation PTV D95% is only 42.9% of RX; with spot weight adaptation, PTV D95% achieves 97.7% RX. Larger errors in patient/target position tracking or prediction led to worse final target coverage; an error of 3 mm or smaller in patient/target position tracking is preferred.

Conclusion: The proposed spot weight adaptation method was able to deliver the planned dose distribution and maintain target coverage when patient motion was involved. The successful implementation of this method would rely on accurate monitoring or prediction of patient/target motion.

No MeSH data available.


Related in: MedlinePlus

The SBRT lung testing case with the delineation of the tumor and the organ-at-risk.
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Figure 5: The SBRT lung testing case with the delineation of the tumor and the organ-at-risk.

Mentions: To evaluate the compensation method, we perform motion simulation and dose computation on a SBRT lung case shown in Figure 5. Motions of moderate amplitude (0.5 cm in any dimension) and large amplitude (1.5 cm in any dimension) are simulated respectively. Different levels of error for motion monitoring are also introduced. The simulation settings are summarized in Table 1.


Spot Weight Adaptation for Moving Target in Spot Scanning Proton Therapy.

Morel P, Wu X, Blin G, Vialette S, Flynn R, Hyer D, Wang D - Front Oncol (2015)

The SBRT lung testing case with the delineation of the tumor and the organ-at-risk.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4447005&req=5

Figure 5: The SBRT lung testing case with the delineation of the tumor and the organ-at-risk.
Mentions: To evaluate the compensation method, we perform motion simulation and dose computation on a SBRT lung case shown in Figure 5. Motions of moderate amplitude (0.5 cm in any dimension) and large amplitude (1.5 cm in any dimension) are simulated respectively. Different levels of error for motion monitoring are also introduced. The simulation settings are summarized in Table 1.

Bottom Line: The impact of the real-time patient/target position tracking or prediction was also investigated.Larger errors in patient/target position tracking or prediction led to worse final target coverage; an error of 3 mm or smaller in patient/target position tracking is preferred.The successful implementation of this method would rely on accurate monitoring or prediction of patient/target motion.

View Article: PubMed Central - PubMed

Affiliation: Laboratoire Informatique Gaspard Monge (LIGM), UMR CNRS 8049, Université Paris-Est , Paris , France.

ABSTRACT

Purpose: This study describes a real-time spot weight adaptation method in spot-scanning proton therapy for moving target or moving patient, so that the resultant dose distribution closely matches the planned dose distribution.

Materials and methods: The method proposed in this study adapts the weight (MU) of the delivering pencil beam to that of the target spot; it will actually hit during patient/target motion. The target spot that a certain delivering pencil beam may hit relies on patient monitoring and/or motion modeling using four-dimensional (4D) CT. After the adapted delivery, the required total weight [Monitor Unit (MU)] for this target spot is then subtracted from the planned value. With continuous patient motion and continuous spot scanning, the planned doses to all target spots will eventually be all fulfilled. In a proof-of-principle test, a lung case was presented with realistic temporal and motion parameters; the resultant dose distribution using spot weight adaptation was compared to that without using this method. The impact of the real-time patient/target position tracking or prediction was also investigated.

Results: For moderate motion (i.e., mean amplitude 0.5 cm), D95% to the planning target volume (PTV) was only 81.5% of the prescription (RX) dose; with spot weight adaptation PTV D95% achieves 97.7% RX. For large motion amplitude (i.e., 1.5 cm), without spot weight adaptation PTV D95% is only 42.9% of RX; with spot weight adaptation, PTV D95% achieves 97.7% RX. Larger errors in patient/target position tracking or prediction led to worse final target coverage; an error of 3 mm or smaller in patient/target position tracking is preferred.

Conclusion: The proposed spot weight adaptation method was able to deliver the planned dose distribution and maintain target coverage when patient motion was involved. The successful implementation of this method would rely on accurate monitoring or prediction of patient/target motion.

No MeSH data available.


Related in: MedlinePlus