Characterization of the INFN proton CT scanner for cross-calibration of x-ray CT

Six decades after its conception, proton computed tomography (pCT) and proton radiography have yet to be used in medical clinics. However, good progress has been made on relevant detector technologies in the past two decades, and a few prototype pCT systems now exist that approach the performance needed for a clinical device.The tracking and energy-measurement technologies in common use are described, as are the few pCT scanners that are in routine operation at this time.Most of these devices still look like detector R\&D efforts as opposed to medical devices, are difficult to use, are at least factor of five slower than desired for clinical use, and are too small to image many parts of the human body.Recommendations are made for what to consider when engineering a pre-clinical pCT scanner that is designed to meet clinical needs in terms of performance, cost, and ease of use.

Section: Detector Requirements For Pctmentioning

confidence: 99%

Section: Infn Prima-rdh Systemmentioning

confidence: 99%

Section: Infn Prima-rdh Systemmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Meeting the detector challenges for pre-clinical proton and ion computed tomography

Johnson

2024

“…The images of the anatomical insert were acquired in extremities configuration by a pCT apparatus, developed by the Italian National Institute of Nuclear Physics and directly mapping SPR. Details and performances of the apparatus are described elsewhere (Fogazzi et al 2023. The instrument is based on a tracker, four-planes of silicon micro-strips respectively two upstream and two downstream the phantom to measure the position and direction of each proton, and a scintillating calorimeter to measure its residual energy (Civinini et al 2020).…”

Section: Pct Apparatusmentioning

confidence: 99%

Proton CT on biological phantoms for x-ray CT calibration in proton treatment planning

Fogazzi,

Bruzzi,

D’Amato

et al. 2024

Self Cite

Objective. To present and characterize a novel method for x-ray computed tomography (xCT) calibration in proton treatment planning, based on proton CT (pCT) measurements on biological phantoms. Approach. A pCT apparatus was used to perform direct measurements of 3D stopping power relative to water (SPR) maps on stabilized, biological phantoms. Two single-energy xCT calibration curves—i.e. tissue substitutes and stoichiometric—were compared to pCT data. Moreover, a new calibration method based on these data was proposed, and verified against intra- and inter-species variability, dependence on stabilization, beam-hardening conditions, and analysis procedures. Main results. Biological phantoms were verified to be stable in time, with a dependence on temperature conditions, especially in the fat region: (−2.5 土 0.5) HU °C−1. The pCT measurements were compared with standard xCT calibrations, revealing an average SPR discrepancy within ±1.60% for both fat and muscle regions. In the bone region the xCT calibrations overestimated the pCT-measured SPR of the phantom, with a maximum discrepancy of about +3%. As a result, a new cross-calibration curve was directly extracted from the pCT data. Overall, the SPR uncertainty margin associated with this curve was below 3%; fluctuations in the uncertainty values were observed across the HU range. Cross-calibration curves obtained with phantoms made of different animal species and anatomical parts were reproducible with SPR discrepancies within 3%. Moreover, the stabilization procedure did not affect the resulting curve within a 2.2% SPR deviation. Finally, the cross-calibration curve was affected by the beam-hardening conditions on xCTs, especially in the bone region, while dependencies below 2% resulted from the image registration procedure. Significance. Our results showed that pCT measurements on biological phantoms may provide an accurate method for the verification of current xCT calibrations and may represent a tool for the implementation of a new calibration method for proton treatment planning.

The INFN proton computed tomography system for relative stopping power measurements: calibration and verification

Scaringella,

Bruzzi,

Farace

et al. 2023

Self Cite

Objective: This paper describes the procedure to calibrate the 3-dimensional proton stopping power relative to water (SPR) maps measured by the proton Computed Tomography (pCT) apparatus of the Istituto Nazionale di Fisica Nucleare (INFN, Italy). Measurements performed on water phantoms are used to validate the method. The calibration allowed for achieving measurement accuracy and reproducibility to levels below 1%. Approach: The INFN pCT system is made of a silicon tracker for proton trajectory determination followed by a YAG:Ce calorimeter for energy measurement. To perform the calibration, the apparatus has been exposed to protons of energies ranging from 83 to 210 MeV. Using the tracker, a position-dependent calibration has been implemented to keep the energy response uniform across the calorimeter. Moreover, correction algorithms have been developed to reconstruct the proton energy when this is shared in more than one crystal and to consider the energy loss in the non-uniform apparatus material. To verify the calibration and its reproducibility, water phantoms have been imaged with the pCT system during two data-taking sessions.Main results: The energy resolution of the pCT calorimeter resulted to be σ(E)/E≅0.9% at 196.5 MeV. The average values of the water SPR in fiducial volumes of the control phantoms have been calculated to be 0.995±0.002. The image non-uniformities were below 1%. No appreciable variation of the SPR and uniformity values between the two data-taking sessions could be identified.Significance: This work demonstrates the accuracy and reproducibility of the calibration of the INFN pCT system at a level below 1%. Moreover, the uniformity of the energy response keeps the image artefacts at a low level even in the presence of calorimeter segmentation and tracker material non-uniformities. The implemented calibration technique allows the INFN-pCT system to face applications where the precision of the SPR 3D maps is of paramount importance.