A comparison of A comparison of heterogeneity correction - - PowerPoint PPT Presentation

A comparison of A comparison of heterogeneity correction heterogeneity correction algorithms within a lung PTV algorithms within a lung PTV

Paola Alvarez, Andrea Paola Alvarez, Andrea Molineu Molineu, Nadia , Nadia Hernandez Hernandez, , David David Followill Followill, Geoffrey , Geoffrey Ibbott Ibbott Radiological Physics Center Radiological Physics Center

July 2007 July 2007

RPC Lung Phantom RPC Lung Phantom

• Plastic shell water

Plastic shell water fillable fillable

• Designed based on

Designed based on patient anatomy patient anatomy

• Imaging and

Imaging and dosimetric insert dosimetric insert

Target dimension Ovoid shape 3 cm diameter 5 cm long Densities Lung = 0.33g/cm3 Heart= 1.1 g/cm3 Cord = 1.31 g/cm3 Tumor = 1.04 g/cm3

RPC Phantom RPC Phantom

Film Slits Tumor (TLD)

Dosimeters TLD and Gafchromic film

Phantom Process Phantom Process

• Phantom is imaged

Phantom is imaged

• Treatment plan developed by institution

Treatment plan developed by institution

• Treatment is delivered to the phantom

Treatment is delivered to the phantom

• Phantom is returned to the RPC for data analysis

Phantom is returned to the RPC for data analysis

• Treatment plan is submitted electronically to the ITC

Treatment plan is submitted electronically to the ITC

• The phantom is to be treated as if it were a patient

The phantom is to be treated as if it were a patient

Prescription Prescription

• Energies: 4

Energies: 4 – – 10 MV 10 MV

• SBRT technique:

SBRT technique: ≥ ≥ 7 non 7 non-

• opposing static fields
• pposing static fields

≥ ≥ 340 340° ° arc rotation technique arc rotation technique

• Prescribed dose must cover 95% of the PTV

Prescribed dose must cover 95% of the PTV

• Prescription isodose line between 60% to 90%.

Prescription isodose line between 60% to 90%.

• Ignore lung heterogeneity for calculation of M.U.

Ignore lung heterogeneity for calculation of M.U.

• Submit hetero. plan based on homo. M.U. set

Submit hetero. plan based on homo. M.U. set

Phantom Results Phantom Results

• A total of 33 irradiations were processed

A total of 33 irradiations were processed

• The 6 MV photon beam was used most often

The 6 MV photon beam was used most often

• The

The TPSs TPSs used to plan the cases were: used to plan the cases were: Pinnacle, BrainLab, XiO, Precise, Eclipse Pinnacle, BrainLab, XiO, Precise, Eclipse Ergo and Hi Ergo and Hi-

• ART.

ART.

• Superposition/Convolution algorithm was

Superposition/Convolution algorithm was used most often. used most often.

Phantom Results Phantom Results

0.98 0.98 ± ± 3.8% 3.8% 2 2 AAA AAA Eclipse Eclipse 0.97 0.97 1 1 Superposition/Convolution Superposition/Convolution Hi Hi-

• ART

ART 0.96 0.96 ± ± 1.8% 1.8% 6 6 Superposition/Convolution Superposition/Convolution XiO XiO 0.99 0.99 ± ± 2.1% 2.1% 10 10 Adaptive convolve Adaptive convolve Pinnacle Pinnacle 0.98 0.98 ± ± 3.2% 3.2% 2 2 3D 3D Convol

• Convol. Pencil Beam

. Pencil Beam Ergo Ergo 0.96 0.96 ± ± 1.8% 1.8% 5 5 Pencil Beam Pencil Beam Eclipse Eclipse 0.96 0.96 ± ± 2.4% 2.4% 5 5 Clarkson & Pencil beam Clarkson & Pencil beam BrainLab BrainLab 0.99 0.99 ± ± 3.1% 3.1% 2 2 Scatter Int. Clarkson Scatter Int. Clarkson Precise Precise Center of Tumor Center of Tumor Measured Measured D DTLD

TLD/

/D Dhetero

hetero

# irradiation # irradiation Dose Calc. Algorithm Dose Calc. Algorithm TPS TPS 0.97 ±2.8%

Profile analysis Profile analysis

Right Left Profile Convolution Superposition example

10 20 30

• 7
• 6
• 5
• 4
• 3
• 2
• 1

1 2 3 4 5 6 7 Distance (cm) D o s e (G y )

RPC Film Institution hetero Institution homo

Right Left

PTV

D2cm Prescribed D

Profile analysis Profile analysis

Right Left Profile Pencil Beam example

10 20 30

• 7
• 6
• 5
• 4
• 3
• 2
• 1

1 2 3 4 5 6 7

Distance (cm) Dose (Gy)

RPC Film Institution hetero Institution homo

Right Left

PTV

D2cm Prescribed D

Phantom Phantom analysis analysis

Criteria Criteria on

• n heterogeneous

heterogeneous case case DTLD/ DTLD/DInst DInst : 0.97 +/ : 0.97 +/-

• 5%

5% DTA DTA ≤ ≤ 5mm 5mm at at all all side side of

• f PTV

PTV An An analysis analysis of

• f the

the dose dose distribution distribution was was done done over

• ver

the the central 80% central 80% of

• f the

the PTV PTV for for these these 23 23 irradiations irradiations. . 23 23 irradiations irradiations passed passed the the test test. .

Superposition/Convolution R Superposition/Convolution R-

• L Profile

L Profile

Right Left Profile Axial plane

10 20 30

• 7
• 6
• 5
• 4
• 3
• 2
• 1

1 2 3 4 5 6 7

Distance (cm) Dose (Gy)

RPC Film Institution hetero Institution homo RPC Regression Institution Regression

Righ Left

PTV

D2cm Average displacement Rigth side:

• n: 1 mm
• ff: 5 mm

Average displacement Left side:

• n: 3 mm
• ff: 1 mm

Prescribed D

Superposition/Convolution R Superposition/Convolution R-

• L Profile

L Profile

Right Left Profile Axial plane

10 20 30

• 7
• 6
• 5
• 4
• 3
• 2
• 1

1 2 3 4 5 6 7

Distance (cm) Dose (Gy)

RPC Film Institution hetero Institution homo RPC Regression Institution Regression

Righ Left

PTV

D2cm Average displacement Rigth side:

• n: 1 mm
• ff: 5 mm

Average displacement Left side:

• n: 3 mm
• ff: 1 mm

Prescribed D

21 23 25

• 1.6
• 1.2
• 0.8
• 0.4

0.4 0.8 1.2 1.6

Superposition/Convolution D Superposition/Convolution DRPC

RPC/

/D DInst

Inst

DRPC / DInst over 80% of PTV on Rt Lt profile

0.80 0.85 0.90 0.95 1.00 1.05 1.10

• 2
• 1.5
• 1
• 0.5

0.5 1 1.5 2 distance (cm) DRPC/DInst

5%

Pencil Pencil-

• Beam profile

Beam profile

Right Left Profile Axial plane

10 20 30

• 7
• 6
• 5
• 4
• 3
• 2
• 1

1 2 3 4 5 6 7

Distance (cm) Dose (Gy)

RPC Film Institution homo Institution hetero RPC Regression Institution Regression

Right Left PTV

D2cm

Average displacement Right side:

• n: -4 mm
• ff: 0 mm

Average displacement Left side:

• n: -2 mm
• ff: -4 mm

Prescribed D

Pencil Pencil-

• Beam profile

Beam profile

Right Left Profile Axial plane

10 20 30

• 7
• 6
• 5
• 4
• 3
• 2
• 1

1 2 3 4 5 6 7

Distance (cm) Dose (Gy)

RPC Film Institution homo Institution hetero RPC Regression Institution Regression

Right Left PTV

D2cm

Average displacement Right side:

• n: -4 mm
• ff: 0 mm

Average displacement Left side:

• n: -2 mm
• ff: -4 mm

Prescribed D

• 1.6
• 1.2
• 0.8
• 0.4

Pencil Beam D Pencil Beam DRPC

RPC/

/D DInst

Inst

DRPC/DInst over 80% of PTV on Rt Lt profile

0.80 0.85 0.90 0.95 1.00 1.05 1.10

• 2
• 1.5
• 1
• 0.5

0.5 1 1.5 2 distance (cm) DRPC/DInst

5% 7% 10%

Summary of Systems Passing Summary of Systems Passing Existing Criteria Existing Criteria

Percent of Points Within: Percent of Points Within: System/Algorithm System/Algorithm 5% 5% 7% 7% 10% 10% Pencil Beam Pencil Beam-

• Clarkson

Clarkson (n=9) (n=9) 69 69 ± ±27% 27% 83 83 ± ±14% 14% 92 92 ± ±8% 8% S Superposition

uperpositionC

Convolution

• nvolution/

/ AAA AAA (n=14) (n=14) 87 87 ± ±20% 20% 95 95 ± ±13% 13% 99 99 ± ±5% 5%

Conclusions Conclusions

• The average target TLD/Inst ratio is 0.97 (range 0.96 to 0.99).

The average target TLD/Inst ratio is 0.97 (range 0.96 to 0.99).

• The calculation from Superposition Convolution and AAA

The calculation from Superposition Convolution and AAA algorithms agree well with the measurements. algorithms agree well with the measurements.

• New evaluation methods needed to assess each algorithm

New evaluation methods needed to assess each algorithm’ ’s s accuracy. accuracy.

Thank you Thank you