SU‐FF‐T‐178: Optimization of Internal Target Margins for Dynamic IMRT and RapidARC

B. Winey, M. Wagar, R. Popple, D. Sher, L. Court

Research output: Contribution to journalArticle

Abstract

Purpose: To determine the optimal Internal Margin (IM) for targets undergoing respiratory motion during treatment with dynamic IMRT and RapidARC. Methods and Materials: Dynamic IMRT and RapidArc plans were created for two targets (3 cm and 5 cm diameter) in the exhale phase with 6 different IM expansions (0,2,4,6,8,10 mm). The plans were delivered to a stationary two‐dimensional ion chamber array (Matrixx, IBA) using a 0.2 second sampling rate. Breathing motions of sin, sin2, sin4, and sin6, with amplitudes of 0 to 4 cm, were simulated by shifting the dose frames by the respiration trace. The resulting simulated motion‐blurred dose planes were randomly sampled from ten starting breathing phases and summed for 30 fractions. The summed dose planes were then compared to the dose delivered to a stationary target with a 0 mm. The optimal IM was calculated as that which resulted in the Equivalent Uniform Dose (EUD) or minimum dose to 95% of the target (D95) closest to that of the stationary case. The optimal margins were fit to the following linear equation: IM = C1*Amp + C2 using a least‐squares fit. Results: The value of C1 ranged from 0.55 to 0.98, depending on the target size, type of target motion, and treatment plan. The optimal IM was ∼2mm larger for sin motion compared with sin6 motion. In all cases the optimal IM calculated using the two different criteria (EUD and D95) agreed within 1mm. Conclusion: Optimal Internal Margins are a function of target size and target motion. In many cases the IM is smaller than the peak‐to‐peak motion. We have developed formulae that correlate motion with the necessary IM.

Original languageEnglish (US)
Number of pages1
JournalMedical Physics
Volume36
Issue number6
DOIs
StatePublished - Jan 1 2009

Fingerprint

Respiration
Ions

ASJC Scopus subject areas

  • Biophysics
  • Radiology Nuclear Medicine and imaging

Cite this

SU‐FF‐T‐178 : Optimization of Internal Target Margins for Dynamic IMRT and RapidARC. / Winey, B.; Wagar, M.; Popple, R.; Sher, D.; Court, L.

In: Medical Physics, Vol. 36, No. 6, 01.01.2009.

Research output: Contribution to journalArticle

Winey, B. ; Wagar, M. ; Popple, R. ; Sher, D. ; Court, L. / SU‐FF‐T‐178 : Optimization of Internal Target Margins for Dynamic IMRT and RapidARC. In: Medical Physics. 2009 ; Vol. 36, No. 6.
@article{e62697e458724a54bf179d7f273c8062,
title = "SU‐FF‐T‐178: Optimization of Internal Target Margins for Dynamic IMRT and RapidARC",
abstract = "Purpose: To determine the optimal Internal Margin (IM) for targets undergoing respiratory motion during treatment with dynamic IMRT and RapidARC. Methods and Materials: Dynamic IMRT and RapidArc plans were created for two targets (3 cm and 5 cm diameter) in the exhale phase with 6 different IM expansions (0,2,4,6,8,10 mm). The plans were delivered to a stationary two‐dimensional ion chamber array (Matrixx, IBA) using a 0.2 second sampling rate. Breathing motions of sin, sin2, sin4, and sin6, with amplitudes of 0 to 4 cm, were simulated by shifting the dose frames by the respiration trace. The resulting simulated motion‐blurred dose planes were randomly sampled from ten starting breathing phases and summed for 30 fractions. The summed dose planes were then compared to the dose delivered to a stationary target with a 0 mm. The optimal IM was calculated as that which resulted in the Equivalent Uniform Dose (EUD) or minimum dose to 95{\%} of the target (D95) closest to that of the stationary case. The optimal margins were fit to the following linear equation: IM = C1*Amp + C2 using a least‐squares fit. Results: The value of C1 ranged from 0.55 to 0.98, depending on the target size, type of target motion, and treatment plan. The optimal IM was ∼2mm larger for sin motion compared with sin6 motion. In all cases the optimal IM calculated using the two different criteria (EUD and D95) agreed within 1mm. Conclusion: Optimal Internal Margins are a function of target size and target motion. In many cases the IM is smaller than the peak‐to‐peak motion. We have developed formulae that correlate motion with the necessary IM.",
author = "B. Winey and M. Wagar and R. Popple and D. Sher and L. Court",
year = "2009",
month = "1",
day = "1",
doi = "10.1118/1.3181653",
language = "English (US)",
volume = "36",
journal = "Medical Physics",
issn = "0094-2405",
publisher = "AAPM - American Association of Physicists in Medicine",
number = "6",

}

TY - JOUR

T1 - SU‐FF‐T‐178

T2 - Optimization of Internal Target Margins for Dynamic IMRT and RapidARC

AU - Winey, B.

AU - Wagar, M.

AU - Popple, R.

AU - Sher, D.

AU - Court, L.

PY - 2009/1/1

Y1 - 2009/1/1

N2 - Purpose: To determine the optimal Internal Margin (IM) for targets undergoing respiratory motion during treatment with dynamic IMRT and RapidARC. Methods and Materials: Dynamic IMRT and RapidArc plans were created for two targets (3 cm and 5 cm diameter) in the exhale phase with 6 different IM expansions (0,2,4,6,8,10 mm). The plans were delivered to a stationary two‐dimensional ion chamber array (Matrixx, IBA) using a 0.2 second sampling rate. Breathing motions of sin, sin2, sin4, and sin6, with amplitudes of 0 to 4 cm, were simulated by shifting the dose frames by the respiration trace. The resulting simulated motion‐blurred dose planes were randomly sampled from ten starting breathing phases and summed for 30 fractions. The summed dose planes were then compared to the dose delivered to a stationary target with a 0 mm. The optimal IM was calculated as that which resulted in the Equivalent Uniform Dose (EUD) or minimum dose to 95% of the target (D95) closest to that of the stationary case. The optimal margins were fit to the following linear equation: IM = C1*Amp + C2 using a least‐squares fit. Results: The value of C1 ranged from 0.55 to 0.98, depending on the target size, type of target motion, and treatment plan. The optimal IM was ∼2mm larger for sin motion compared with sin6 motion. In all cases the optimal IM calculated using the two different criteria (EUD and D95) agreed within 1mm. Conclusion: Optimal Internal Margins are a function of target size and target motion. In many cases the IM is smaller than the peak‐to‐peak motion. We have developed formulae that correlate motion with the necessary IM.

AB - Purpose: To determine the optimal Internal Margin (IM) for targets undergoing respiratory motion during treatment with dynamic IMRT and RapidARC. Methods and Materials: Dynamic IMRT and RapidArc plans were created for two targets (3 cm and 5 cm diameter) in the exhale phase with 6 different IM expansions (0,2,4,6,8,10 mm). The plans were delivered to a stationary two‐dimensional ion chamber array (Matrixx, IBA) using a 0.2 second sampling rate. Breathing motions of sin, sin2, sin4, and sin6, with amplitudes of 0 to 4 cm, were simulated by shifting the dose frames by the respiration trace. The resulting simulated motion‐blurred dose planes were randomly sampled from ten starting breathing phases and summed for 30 fractions. The summed dose planes were then compared to the dose delivered to a stationary target with a 0 mm. The optimal IM was calculated as that which resulted in the Equivalent Uniform Dose (EUD) or minimum dose to 95% of the target (D95) closest to that of the stationary case. The optimal margins were fit to the following linear equation: IM = C1*Amp + C2 using a least‐squares fit. Results: The value of C1 ranged from 0.55 to 0.98, depending on the target size, type of target motion, and treatment plan. The optimal IM was ∼2mm larger for sin motion compared with sin6 motion. In all cases the optimal IM calculated using the two different criteria (EUD and D95) agreed within 1mm. Conclusion: Optimal Internal Margins are a function of target size and target motion. In many cases the IM is smaller than the peak‐to‐peak motion. We have developed formulae that correlate motion with the necessary IM.

UR - http://www.scopus.com/inward/record.url?scp=85024807832&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85024807832&partnerID=8YFLogxK

U2 - 10.1118/1.3181653

DO - 10.1118/1.3181653

M3 - Article

AN - SCOPUS:85024807832

VL - 36

JO - Medical Physics

JF - Medical Physics

SN - 0094-2405

IS - 6

ER -