**7. Radiograph data analysis**

*Applications of Optical Fibers for Sensing*

range shifter of about 10 mm thickness.

mized using multiple PSD at different depths in the RRD.

undergone a negligible deflection traversing the medium. This error could be mini-

The z value in **Figure 9** is the centroid of the range distribution, expressed in numbers of RRD layers, pixel by pixel. Notice that the empty quarter-circle sector refers to the thickest step, 15 mm thick, of the ladder. The 58 MeV protons of the CATANA beam have insufficient energy to exit after passing through the thickness of the A12 range shifter and 15 mm of PVC. Moreover, border effects due to the nonorthogonality of the ladder with respect to the beam axis and the unavoidable divergence of the beam caused by the use of range shifters are visible in the radiography. The void pixels within the spot correspond to pixels where the range measurement statistics is too low. Many of these pixels are aligned along the same row or column, suggesting a correlation to low efficiency of the tracker in those areas. Two different 3D perspectives of the radiography are shown in **Figure 10(a)** and **(b)**. The last step in the analysis is the calculation of the relation between the measured range and the ΔE energy lost by the particles. The ΔE calculation must also take into account the energy lost by the particles in the PSD, which is placed between the target and the RRD. Since the sensitive areas of both detectors consist of 500 μm layers of SciFi, the PSD can be considered as an extension of the RRD. The residual proton range in the PSD and RRD was simulated as a function of the particle initial energy in the tracker E.

The range values thus obtained were fitted to the power law reported below in the equation, where R is the particle range in the RRD and PSD, expressed as the number of layers, and the resulting fit parameters are A = −0.191 ± 0.311 and B = 0.0370 ± 0.0006

The final radiography obtained after applying the energy-range conversion

*Two different perspectives of the 3D representation of the radiography: (a) lateral view and (b) isometric* 

\_\_\_\_ *R* − *A <sup>B</sup>* )

1/1.75

(R - square = 0.998). Therefore, the energy loss ΔE can be easily calculated as

Δ*E*[*MeV*] = 58 − (

formula is shown in **Figure 11**.

A simple PVC target with the shape of a ladder was designed for the radiography test. Due to the homogeneous density of the target, in the radiography, only the differences in thickness traversed by the protons can be distinguished. The radiography image reported in **Figure 9** refers to a 3.5 cm diameter beam crossing a PMMA

**90**

**Figure 10.**

*perspective.*

As mentioned earlier, radiography images reconstructed from range measurements are subject to some limitations: (i) lack of knowledge of the effective paths of the particles crossing the phantom because only one PSD was used. In this case, particle trajectories cannot be corrected according to the effect of Multiple Coulomb; (ii) further beam divergence was introduced by the tolerances in the alignment of the target, not exactly placed at isocenter and perpendicular to the incident beam direction. The reduction of the error in the calculus of the target thickness is obtained by the data filtering of range measurements. From the simulations, protons with an initial energy of 58 MeV crossing A12 range shifter, the target and the tracker, and stopping in the RRD have a maximum range straggling of σstr = 0.4 mm, which already includes the effects of initial energy spread (0.3 MeV). So, in a region of interest (ROI) corresponding to a homogeneous quarter of the target, a range of measurements around the expected value from the simulation can be selected plus or minus two layers (equal to six times σstr).

Subtracting the square of the maximum range straggling value of σstr = 0.4 mm from the standard deviation of range measurements, it is again possible to find the a priori range resolution of about 170 μm. These mean range values can be converted into proton energy loss and subsequently into energy loss.

### **8. Future developments**

The combined use of a pencil beam facility and the radiographic system, presented in this chapter, could allow the development of a faster real-time

### **Figure 12.**

*The real-time reconstructed pattern. The x and y for each point are measured by the PSD. The z is the range measured by the RRD. The color is proportional to the measured fluence.*

radiographic technique. Furthermore, the acquired radiography will be spatially correlated with the treatment plan applied to the patient. Exploiting the features of the described proton imaging system, a new method of quantifying treatment plan quality will be investigated.

A demonstrative measurement has been performed at CNAO in Pavia. A simple pattern of point in the field of view of the radiographic system, presented in this chapter, was covered by the pencil beam. The same pattern was modulated in energy, in the range of energy compatible with the range in the RRD, in order to obtain a 3D matrix. Each point in the matrix was covered by the pencil beam in one spill delivering a fixed dose, up to 109 protons per spill. The PSD measured the centroid, the FWHM and the fluence of the beam delivered in each position. The RRD measured the centroid, the FWHM of the range of the protons delivered in each spill. **Figure 12** shows the real-time reconstructed pattern.

The results demonstrate the potentiality of the system. Accurate measurements will be performed in order to refine these statements in a quantitative way at TIFPA in a treatment room. In these future tests, a calibrated phantom will be used for the measurement.

The definition of the optimal parameters for the radiography, e.g., beam energy and fluence to be chosen in order to obtain the required spatial and density resolution will allow the definition of the specifications for the design of the final detectors.

### **9. Conclusions**

This chapter presents the design and characterization of an innovative imaging system for charged particle beam based on SciFi. The system consists of a positionsensitive detector and a residual range detector. Both prototypes, with a sensitive area of 90 × 90 mm2 , have cutting-edge performances, which distinguish them from

**93**

**Author details**

be tested.

Daniele Giuseppe Bongiovanni2

provided the original work is properly cited.

© 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

, Fabio Longhitano2

1 Department of Physics and Astronomy, University of Catania, Catania, Italy

,

and Santo Reito2

Domenico Lo Presti1,2\*, Giuseppe Gallo1,2, Danilo Luigi Bonanno2

2 Istituto Nazionale di Fisica Nucleare, Catania, Italy

\*Address all correspondence to: domenico.lopresti@ct.infn.it

*Real-Time Particle Radiography by Means of Scintillating Fibers Tracker and Residual Range…*

all other devices designed for the purposes considered in this chapter. In addition, improvements in the DAQ chain and the use of SiPM arrays make possible the use of the PSD as a beam monitoring and quality assurance system, by measuring real time the center and the shape of the spot, the fluence, and residual energy of the beam. The verification of this feature was investigated and demonstrated in beam tests. The performance of the PSD and RRD was tested at CATANA proton therapy facility with energies up to 58 MeV. Moreover, Monte Carlo simulations of the RRD detector response and the radiography of a calibrated target were measured by the system. From the analysis of the results and by a comparison with data from simula-

Tests at CNAO and TIFPA validated the functionality of these devices with active beam shaping systems using protons with energies up to 250 MeV. Future developments concern the real-time qualification of a treatment plan and the comparison of the results with those provided by the official dose delivery system. Furthermore, the feasibility of a real-time radiography exploiting pencil beam will

*DOI: http://dx.doi.org/10.5772/intechopen.81784*

tions, the architecture and the technology were validated.

## *Real-Time Particle Radiography by Means of Scintillating Fibers Tracker and Residual Range… DOI: http://dx.doi.org/10.5772/intechopen.81784*

all other devices designed for the purposes considered in this chapter. In addition, improvements in the DAQ chain and the use of SiPM arrays make possible the use of the PSD as a beam monitoring and quality assurance system, by measuring real time the center and the shape of the spot, the fluence, and residual energy of the beam. The verification of this feature was investigated and demonstrated in beam tests. The performance of the PSD and RRD was tested at CATANA proton therapy facility with energies up to 58 MeV. Moreover, Monte Carlo simulations of the RRD detector response and the radiography of a calibrated target were measured by the system. From the analysis of the results and by a comparison with data from simulations, the architecture and the technology were validated.

Tests at CNAO and TIFPA validated the functionality of these devices with active beam shaping systems using protons with energies up to 250 MeV. Future developments concern the real-time qualification of a treatment plan and the comparison of the results with those provided by the official dose delivery system. Furthermore, the feasibility of a real-time radiography exploiting pencil beam will be tested.
