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Optimal planning strategy among various arc arrangements for prostate stereotactic body radiotherapy with volumetric modulated arc therapy technique


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An arrangement of (A) one full arc (1FA), (B) one partial arc (1PA), (C) two full arcs (2FA), and (D) two partial arcs (2PA) in prostate SBRT-VMAT for the same patient.
An arrangement of (A) one full arc (1FA), (B) one partial arc (1PA), (C) two full arcs (2FA), and (D) two partial arcs (2PA) in prostate SBRT-VMAT for the same patient.

An example of the dose distributions achieved with (A) one full arc (1FA), (B) one partial arc (1PA), (C) two full arcs (2FA), and (D) two partial arcs (2PA) arrangement in prostate SBRT-VMAT for the same patient.
An example of the dose distributions achieved with (A) one full arc (1FA), (B) one partial arc (1PA), (C) two full arcs (2FA), and (D) two partial arcs (2PA) arrangement in prostate SBRT-VMAT for the same patient.

Average dose-volume histograms of the (A) PTV, (B) bladder, (C) rectum, (D) left femoral head, and (E) right femoral head from prostate SBRT-VMAT plans for four arc arrangements (1FA, 1PA, 2FA, and 2PA).
Average dose-volume histograms of the (A) PTV, (B) bladder, (C) rectum, (D) left femoral head, and (E) right femoral head from prostate SBRT-VMAT plans for four arc arrangements (1FA, 1PA, 2FA, and 2PA).

Dosimetric results for target volumes in prostate SABR-VMAT plans using four arc arrangements.

Avg ±SD (range)
1FA1PA2FA2PA
CTV coverage
 D50% (Gy)44.9±0.444.6±0.544.5±0.544.4±0.3
(44.4-45.4)(44.1-45.1)(44.0-45.3)(44.0-44.7)
 D5% (Gy)46.0±0.145.9±0.145.9±0.145.8±0.2
(45.9-46.1)(45.7-46.0)(45.8-46.0)(45.7-45.9)
 D95% (Gy)43.5±0.543.1±0.443.1±0.642.8±0.2
(43.0-44.2)(42.8-43.5)(42.6-43.9)(42.7-43.1)
 V100% (%)98.4±1.897.9±0.097.8±3.897.6±2.0
(95.5-100.0)(95.0-99.8)(95.2-100.0)(94.2-99.9)
PTV coverage
 Dmean44.3±0.244.2±0.144.1±0.344.3±0.1
(44.2-44.6)(44.0-44.4)(44.0-44.6)(44.2-44.5)
 Dmax48.8±0.849.5±0.948.5±1.149.0±1.4
(47.8-49.8)(48.4-50.5)(47.2-50.0)(47.4-50.5)
 Dmin33.0±0.432.3±0.032.8±0.833.7±0.3
(32.4-33.2)(31.9-33.7)(32.1-33.9)(33.4-34.1)
 D50% (Gy)44.6±0.344.5±0.244.4±0.444.5±0.2
(44.2-45.0)(44.3-44.8)(44.1-45.0)(44.3-44.8)
 D5% (Gy)46.1±0.246.1±0.146.1±0.246.0±0.1
(45.9-46.3)(45.9-46.2)(45.9-46.3)(45.9-46.2)
 D95% (Gy)41.5±0.341.4±0.241.3±0.341.7±0.1
(41.1-41.8)(41.2-41.8)(41.0-41.7)(41.6-41.9)
 V100% (%)87.5±1.986.6±1.287.7±1.588.1±1.0
(85.1-90.2)(85.0-87.8)(85.8-89.3)(87.1-89.9)
 Conformity1.05±0.001.04±0.011.03±0.011.05±0.01
 index(1.02-1.03)(1.02-1.04)(1.02-1.04)(1.02-1.03)
 Conformation0.91±0.010.91±0.010.91±0.010.91±0.01
 number(0.90-0.92)(0.09-0.92)(0.91-0.92)(0.90-0.93)
 Homogeneity0.10±0.010.11±0.000.11±0.010.10±0.00
 index(0.09-0.12)(0.10-0.11)(0.10-0.12)(0.09-0.10)

Dose volume constraints adopted for planning study.

VolumeRectumBladderFemoral heads
V42.7Gy (100%) < 5%V42.7Gy(100%) < 10%V29.9Gy (70%) < 50%
V38.4Gy (90%) < 15%V34.7Gy (81%) < 25%Dmax <29.9 Gy
ConstraintsV32.0Gy (75%) < 35%V29.9 Gy(70%) < 50%
V28.0Gy (65%) < 45%
V24.8Gy (58%) < 70%
V20.0Gy (47%) < 80%

Average monitor unit and delivery time for prostate SBRT-VMAT plans using four arc arrangements.

Beams1FA (Mean ± SD)1PA (Mean ± SD)2FA (Mean ± SD)2PA (Mean ± SD)
MU1575±631627±561646±971660±98
Delivery time (min)1.01±0.020.69±0.012.00±0.011.36±0.02

TCP of prostate tumor and NTCP of OARs for four arc arrangement plans.

Beams1FA (Mean±SD)1PA (Mean±SD)2FA (Mean±SD)2PA (Mean±SD)
TCP (%)
 Prostate93.35±0.0899.28±0.0693.32±0.0893.36±0.08
NTCP (%)
 Rectum0.44±0.230.61±0.210.40±0.230.56±0.22
 Bladder0.01±0.020.01±0.030.00±0.010.00±0.02
 LT Femur0.00±0.000.00±0.000.00±0.000.00±0.00
 RT Femur0.00±0.000.00±0.000.00±0.000.00±0.00

Parameters used to calculated Niemierko’s EUD-based TCP and NTCP.

Tissue100%dpf (Gy)Fraction (#)αγ50TD50 (Gy)TCD50 (Gy)dpf (Gy)α/β (Gy)
Prostate6.17-101.028.3421.20
Rectum6.178.3348023.90
Bladder6.17248028.00
Femur6.17446520.85

Dosimetric results for organs at risk in prostate SABR-VMAT plans using four arc arrangements.

Avg SD (range)
IFA1PA2FA2PA
Organs at risk
Rectum Dmean (Gy)25.2±1.723.3±2.023.6±1.823.4±1.9
(23.1-27.2)(21.4-25.8)(21.3-26.0)(21.3-26.4)
Rectum D2% (Gy)44.2±0.344.6±0.444.1±0.444.5±0.2
(43.7-44.5)(44.0-45.1)(43.8-44.7)(44.3-44.9)
Rectum V95% (%)9.0±1.410.1±1.38.3±1.39.8±1.5
(6.6-10.3)(8.1-11.5)(7.0-10.2)(7.6-11.6)
Rectum V80% (%)19.1±3.019.7±3.218.0±2.819.4±3.4
(15.1-23.2)(15.2-23.8)(15.2-21.9)(14.8-24.3)
Rectum V50% (%)71.0±8.853.9±9.460.0±11.154.1±9.0
(61.1-80.1)(41.9-63.7)(46.9-77.4)(42.5-66.7)
Rectum V20% (%)90.2±2.590.0±2.789.6±3.090.0±2.8
(87.7-93.4)(87.1-94.1)(85.6-93.5)(87.3-94.0)
Bladder Dmean (Gy)19.0±6.918.7±7.118.5±6.118.3±6.9
(13.4-31.1)(13.2-31.0)(15.7-29.0)(12.9-30.4)
Bladder D2% (Gy)45.6±0.245.6±0.245.5±0.345.6±0.4
(45.5-45.8)(45.3-45.9)(45.0-45.8)(45.3-46.4)
Bladder V95% (%)21.2±11.121.4±11.120.9±10.521.4±11.3
(10.5-39.3)(10.6-39.4)(10.3-37.7)(10.7-39.9)
Bladder V80% (%)25.6±11.926.2±11.925.7±11.126.0±12.0
(16.6-46.4)(16.5-46.3)(16.6-44.6)(16.3-46.2)
Bladder V50% (%)40.4±13.638.6±12.639.5±12.438.2±12.9
(29.4-64.1)(28.5-60.5)(29.2-60.7)(27.5-60.6)
Bladder V20% (%)54.4±17.052.5±16.154.1±17.452.1±16.1
(37.2-79.1)(36.4-76.5)(37.0-79.4)(36.2-76.1)
Left femoral head12.8±1.818.7±2.312.7±2.413.9±1.4
Dmean (Gy)(10.5-15.1)(16.9-22.7)(9.3-14.9)(11.7-15.3)
Left femoral head19.7±2.223.5±4.418.3±3.020.1±2.0
D2% (Gy)(16.9-21.8)(15.6-26.1)(13.4-20.7)(16.7-21.8)
Right femoral10.8±0.913.3±2.512.4±1.713.7±2.1
head Dmean (Gy)(9.2-11.3)(9.2-15.5)(10.5-14.2)(10.7-16.5)
Right femoral16.4±1.320.6±3.718.1±1.919.7±2.3
head D2% (Gy)(14.3-18.0)(14.3-23.6)(15.8-20.1)(16.2-22.5)
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Medizin, Klinische Medizin, Radiologie, Allgemeinmedizin, Innere Medizin, Hämatologie, Onkologie