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.  

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Syllabus  

PHEW!!!!!!!  

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EPID  QA  

•  Uniformity  versus  thickness  (across  flat-­‐field  images)  

•  SNR  versus  thickness  of  solid  water  •  MTF  

•  CNR  •  SNR  •  EPID’s  alignment  with  gantry  isocenter  

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Addi4onal  

•  CNR  vs  Thickness  vs  Dose  •  Effect  of  filtraRon  on  images  

•  MTF  calculaRon  validaRon  

•  Contrast  calculaRons  for  Air  &  Bone  in  water    •  DidacRc    

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EPID  QA:  Image  Uniformity  vs  Thickness  

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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

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EPID  QA:  Signal-­‐to-­‐Noise  raRo  vs  Thickness  

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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  

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EPID  QA:    Imaging  Parameters  

(SNR,  CNR,  MTF,  Dose  dependence)  

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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

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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    

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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

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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)

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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

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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)

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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.

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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)  

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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

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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!!!!!  

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