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Imaging for Planning and Treatment Verifica4on
(Rota&on 7)
Mentor: Ryan Flynn, Ph.D. (12/16/09 – 01/15/10)
By Vibha Chaswal, Ph.D.
2/24/14 1
Syllabus
PHEW!!!!!!!
2/24/14 2
EPID QA
• Uniformity versus thickness (across flat-‐field images)
• SNR versus thickness of solid water • MTF
• CNR • SNR • EPID’s alignment with gantry isocenter
2/24/14 3
Addi4onal
• CNR vs Thickness vs Dose • Effect of filtraRon on images
• MTF calculaRon validaRon
• Contrast calculaRons for Air & Bone in water • DidacRc
2/24/14 4
EPID QA: Image Uniformity vs Thickness
2/24/14 5
0.800
0.830
0.860
0.890
0.920
0.950
0.980
1.010
0 5 10 15 20 25 30 35
Uniform
ity (Normalized
mean PV
in an RO
I)
Solid Water Thickness (cm)
Image Uniformity vs Solid Water Thickness
ROI_1 (top) ROI_2 (boaom) ROI_3 (right) ROI_4 (leb) ROI_5 (center)
1
2
3 45
2/24/14 6
EPID QA: Signal-‐to-‐Noise raRo vs Thickness
2/24/14 7
2/24/14 8
0
50
100
150
200
250
300
0 5 10 15 20 25 30 35
SNR
Sold Water Thickness (cm)
Signal-‐to-‐Noise Ra4o vs Thickness of SW slab
2/24/14 9
EPID QA: Imaging Parameters
(SNR, CNR, MTF, Dose dependence)
2/24/14 10
0.1 lp/mm
0.23 lp/mm
0.2 lp/mm
0.43 lp/mm
0.76 lp/mm
15 mm PVC
15 mm Al
5 mm lead
7.5 mm Pb
11 mm Pb
Material Physical density (g/cm3)
PVC 1.00
Al 2.6
Pb 11.34
QC - 3V Phantom s/n 104
2/24/14 11
MTF Calculation Validation
2/24/14 12 Droege R.T, Morin R. L, ‘A practical method to measure MTF of scanners’, Med. Phys. 9(5), 1982
lp/mm Std Dev
0.1 663.45
0.2 1342.163
0.23 2066.66
0.43 2315.17
0.76 2825.81
EPID spatial resolution: MTF Calculation
0.00
0.20
0.40
0.60
0.80
1.00
1.20
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
MTF
line-‐pairs/mm (lp/mm)
MTF measured using QC-‐3V phantom
2/24/14 13
Imaging Parameters: SNR Region Physical
density (g/cm3)
Depth (cm)
Radiological Path-‐length (g/cm2)
1 (Pb) 11.34 0.75 8.505
2 (PVC) 1 1.5 1.5
3 (Pb) 11.34 0.5 5.67
4 (Al) 2.6 1.5 3.9
5 (Pb) 11.34 1.1 12.474
6 (Pb) 11.34 0.75 8.505
0
20
40
60
80
100
120
140
0 2 4 6 8 10 12 14
SNR (stand
ard de
via4
on)
Radiological pathlength (g/cm2)
SNR versus Radiological Path-‐length
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SNR analysis ROIs 1 & 6
ROI 1 ROI 6
2/24/14 15
10-QC-10 1MU 2MU 3MU
20-QC-10 1MU 2MU 3MU
30-QC-10 1MU 2MU 3MU
EPID QA: CNR vs Thickness vs Dose
(QC-3V as tumor inside varying solid water thickness patients)
2/24/14 16
10 cm
20 cm
30 cm
-‐
10.00
20.00
30.00
40.00
50.00
60.00
0 2 4 6 8 10 12 14
Contrast-‐to-‐Noise Ra4
o w.r.t. 15m
m PVC
Radiological Thickness (g/cm2)
CNR of QC-‐3 phantom vs Radiological Thickness (for different doses and solid water thicknesses)
20 cm
2/24/14 17
10 cm
30 cm
1 MU
2 MU
3 MU
Gantry 0 degree Gantry 90 degree
Gantry 270 degree, Gantry 180 degree
EDPI QA: EPID Alignment (Oncor A)
2/24/14 18
Fig 4(c): Gantry 180 degree, distance measurements between x-retic and e-retic.
Fig 4(d): Gantry 180 degree, distance measurements between x-retic and e-retic at the central ISIS sphere
region that coincides with radiation isocenter; note that distance between x-retic and e-retic is 2.3mm, which is more than the tolerance value of 2mm.
Hence, EPID is not aligned within specifications at Gantry angle 180-degrees. 2/24/14 19
Fig 4(e): Gantry 180 degree, distance measurements between x-retic and center of pinhole of ISIS.
Fig 4(f): Gantry 180 degree, distance measurements between e-retic and center of pinhole of ISIS.
2/24/14 20
Clinical ObservaRon
• Whole brain x 1 • Head and neck x 2 (MVCBCT)
• Pelvis x 1 (portal) x 3 (MVCBCT)
• Thoracic x 1 (portal) x 2 (MVCBCT)
• Extra-‐cranial lung x 1 (MVCBCT)
• Supine Breast x 1 (portal)
2/24/14 21
2/24/14 22
Head & Neck Pelvic Extra-Cranial Lung
Treatment Verification: MVCBCT
Whole Brain DRR
Reference DRR Right Lat Treatment day Right lat portal image Registered DRR and portal image
2/24/14 23
Reference Planning PA DRR Treatment day PA portal image Registered PA images
Pelvic DRR
Treatment Verification: Portal Imaging
Thoracic DRR
Reference Planning AP setup DRR
Reference Planning Left Anterior Oblique field DRR at Gantry 45-deg
Treatment day AP double exposure portal image
Treatment day Left Anterior Oblique field portal image at Gantry 45-deg
Registered AP DRR and portal images
Registered Left Anterior Oblique DRR and portal images
Reference Planning field DRR Left Lat Gantry 90-deg
Reference Planning Right Anterior Oblique field DRR at Gantry 344.9-deg
Treatment day Left Lat field portal image at Gantry 90-deg
Treatment day Right Anterior Oblique field portal image at Gantry 344.9-deg
Registered Left Lat DRR and portal images
Registered Right Anterior Oblique DRR and portal images 2/24/14 24
THANK YOU!!!!!
2/24/14 25