Activities for Proton Computed Tomography PCT

Loma Linda University Medical Center

Hartmut F.-W. SadrozinskiSanta Cruz Inst. for Particle Physics SCIPP

State University of New York at Stony Brook

UCSC Santa Cruz Institute of

Particle Physics

INFN Florence & Catania

The Proton CT Collaboration

• Proton Treatment: LLUMC

• Particle Tracking Systems: SCIPP, INFN Firenze

• Energy Detectors: BNL, LLUMC, INFN Catania

• Monte Carlo Simulation (GEANT 4): BNL, SCIPP, INFN, SLAC

• Image Reconstruction: SUNY Stony Brook

http://scipp.ucsc.edu/pCT/

•Goal

–Develop proton CT for applications in proton therapy

•Specific Aims

–Design, construct and test components of a modular proton CT system

–Develop, test, and optimize a dose-efficient image reconstruction algorithm

–Evaluate performance of proton CT prototype

Why Proton CT?

• Major advantages of proton beam therapy:

– Finite range in tissue (protection of critical normal tissues) since cross section fairly flat and low away from peak

– Maximum dose and effectiveness at end of range (Bragg peak effect)

• Major uncertainties of proton beam therapy:

– range uncertainty due to use of X-ray CT for treatment planning (up to several mm)

– patient setup variability

Goal of pCT Collaboration

Develop proton CT for applications in proton therapy

Computed Tomography (CT)

X-ray tube

Detector array

XCT:• Based on X-ray absorption• Faithful reconstruction of patient’s

anatomy• Stacked 2D maps of linear X-ray

attenuation• Coupled linear equations• Invert matrices and reconstruct z-

dependent features

Proton CT: • replaces X-ray absorption with proton

energy loss • reconstruct mass density ( distribution

instead of electron distribution

Proton CT System (Final & prototype)

Comparison pCT - X-ray CT

52

2

~ Dd

E

b

a

Challenge One: Calorimeter Resolution

• Can achieve proton energy resolution much better than energy straggling (~1%)

52

2

~ Dd

E

• Dose to the patient during imaging depends on the square of the effective energy resolution (including beam straggling)

“First Experimental Calorimeter Studies for Proton CT at LLUMC”, M. C. L. Klock, R. W. Schulte, V.Bashkirov, et al., submitted to Nucl. Inst. Meth.

Challenge Two: High-speed DAQ

SSDPFME

FPGA

Hardware:

Modular

Commercial

Hartmut Sadrozinski et al., IEEE TRANS ON NUCL. SCIE., VOL. 51, NO. 5, 1

(NI 6534).

Fig. 7. Reference system for the simulation study. The phantom is centered at u =15 cm, t = 3.5 cm. The protons arrive along the u direction at plane u = 0 cm. The entry and exit detector planes are at u = 0 cm and u = 30 cm respectively. Images of the phantom shown in Fig. 7 reconstructed from a simulated data set of (a) 35,000 proton histories and (b) 8,750 proton histories per projection. In the left images all holes had an object contrast of 100%, in the center images the contrast of the top, center, and bottom row of holes was 30%, 20%, and 10%, respectively, and in the left images

3 m

m

2 m

m

1.5

mm

0.5

mm

4 m

m

1 m

m0.

75 m

m

b

a

Challenge Four: Low-Dose Image reconstruction

0.1

1

10

100

0.1 1 10

Object diameter (mm)

Ob

ject

co

ntr

ast

(%)

5.48 mGy

1.37 mGy

Challenge Four: Image of Al AnnulusSubdivide SSD area into pixels1. Strip x strip 194um x 194um2. 4 x 4 strips (0.8mm x 0.8mm)

Image corresponds to average energy in pixel

“Initial studies on proton computed tomography using a silicon

strip detector telescope”, L. Johnson et al., NIM. A 514 (2003) 215

Beam Test Improvements

• Improvements: – Increased precision of input parameters (entrance angle) needed to

correct for beam divergence

– Calorimeter DAQ

– Geant4 description of data and understanding of “Banana” in non-uniform medium

• Next Steps: NON-uniform phantom (non-uniform density and/or shape, small aninal?)

• pCT Reconstruction: FBP, Layer-by-layer deconvolution

Banana Improvements

• Add non-uniformities of phantom to “banana”• Needs to be validated with GEANT4• How to add into reconstruction?

Beam Test Improvements: Resolution• Theoretical Resolution in pCT set-up as a function of distance z1 in first telescope.

• In Tel

• L= 20 cm

• z4=3cm

• Measure x1, x2, x4, x5 and , reconstruct displacement d and entrance angle and exit angle

In Tel

Out Tel

xy

Si

N - m plates

m plates

z1

L

z4

1

)12(

z

xx

111 6

0236.012

0236.0

22zzz

x

Lz

xxxxLxxd

1

12)24()24(

2

1

2

1

2 2 21

6

0236 . 0)

6

0236 . 0( )

6

0236 . 0( ) ( ) 2 (

z

LL

zL x d

1

12

4

45

4

45

z

xx

z

xx

z

xx

2

4

2

1

2

1

2

4

2

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11

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0236.022)(

2

zzzzzxxx

Beam Test Improvements: Resolution• Theoretical Resolution in pCT set-up as a function of distance z1 in first telescope.

• Measure x1, x2, x4, x5 and , reconstruct displacement d and entrance angle and exit angle

z1

[cm]

[rad]

d

[cm]

[rad]

[rad] (z4=6cm)

Theo 3 0.0032 0.0649 0.0045 0.003591

10 0.0010 0.0215 0.0034 0.001873 30 0.0003 0.0116 0.0032 0.001638

BT ’05 0 0.0050 0.1005 0.0059

AcknowledgmentsLLUMC

Reinhartd Schulte, MDVladimir Bashkirov, PhDGeorge Coutrakon, PhDPeter Koss, MS

SUNY Stony BrookJerome Z. Liang, PhDKlaus Mueller, PhDTianfang Li (grad student)

INFN Catania Pablo Cirrone, PhDGiacomo Cuttone, PhDNunzio Randazzo, PhDDomenico Lo Presti, EngineerValeria Sipali (grad student)

Brookhaven National LaboratorySteve Peggs, PhDTodd Satogata, PhDCraig Woody, PhD

Florence U. Mara Bruzzi, PhDDavid Menichelli, PhDMonica Scaringella (grad student)

Santa Cruz Institute of Particle PhysicsHartmut Sadrozinski, PhDAbe Seiden, PhDDavid C Williams, PhDZhan Lang, PhDBrian Keeney (grad. Student) Jason Feldt (grad. Student) Jason Heimann (undergrad student)Dominic Lucia (undergrad student)Nate Blumenkrantz (undergrad student)Eric Scott (undergrad student)