Operation of the preclinical head scanner for proton CT

Sadrozinski, H. F-W.; Geoghegan, Theodore; Harvey, Evan; Johnson, R. P.; Plautz, Tia; Zatserklyaniy, A.; Bashkirov, V.; Hurley, Robert F.; Piersimoni, Pierluigi; Schulte, R.; Karbasi, Paniz; Schubert, Keith E.; Schultze, Blake; Giacometti, Valentina

doi:10.1016/j.nima.2016.02.001

Cited by 35 publications

(40 citation statements)

References 15 publications

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“…The most inner planes (P1 and P2) were at a distance of 164.3 mm from the isocenter, while the most outer (P0 and P3) at 214.35 mm. Each plane was made of 2 silicon boards, 349 × 86 × 0.4 mm 3 , each of them used to score the position of the tracked protons . The MSS aperture was 37.5 × 10 cm 2 , designed to optimize the accuracy of the WEPL measurements while simplifying the detector construction and the performance requirements of its components.…”

Section: Methodsmentioning

confidence: 99%

“…The system, completed in 2011, is capable of imaging phantom heads and QA phantoms with protons of a nominal energy of 200 MeV. The device dimensions and the position‐sensitive detector modules are similar in essential characteristics to the first generation system, with the exception of a larger sensitive tracking area (9 cm × 36 cm instead of 9 cm × 18 cm) and replacement of the original RERD by a multi‐stage scintillator (MSS), consisting of a stack of five fast plastic scintillators, read out by photomultiplier tubes . This design provides a more accurate determination of the residual energy/range of protons, compared with the calorimeter of the first generation system .…”

Section: Introductionmentioning

confidence: 99%

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The effect of beam purity and scanner complexity on proton CT accuracy

et al. 2017

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Purpose To determine the dependence of the accuracy in reconstruction of relative stopping power (RSP) with proton computerized tomography (pCT) scans on the purity of the proton beam and the technological complexity of the pCT scanner using standard phantoms and a digital representation of a pediatric patient. Methods The Monte Carlo method was applied to simulate the pCT scanner, using both a pure proton beam (uniform 200 MeV mono-energetic, parallel beam) and the Northwestern Medicine Chicago Proton Center (NMCPC) clinical beam in uniform scanning mode. The accuracy of the simulation was validated with measurements performed at NMCPC including reconstructed RSP images obtained with a preclinical prototype pCT scanner. The pCT scanner energy detector was then simulated in three configurations of increasing complexity: an ideal totally absorbing detector, a single stage detector and a multi-stage detector. A set of 15 cm diameter water cylinders containing either water alone or inserts of different material, size, and position were simulated at 90 projection angles (4° steps) for the pure and clinical proton beams and the three pCT configurations. A pCT image of the head of a detailed digital pediatric phantom was also reconstructed from the simulated pCT scan with the prototype detector. Results The RSP error increased for all configurations for insert sizes under 7.5 mm in radius, with a sharp increase below 5 mm in radius, attributed to a limit in spatial resolution. The highest accuracy achievable using the current pCT calibration step-phantom and reconstruction algorithm, calculated for the ideal case of a pure beam with totally absorbing energy detector, was 1.3% error in RSP for inserts of 5 mm radius or more, 0.7 mm in range for the 2.5 mm radius inserts, or better. When the highest complexity of the scanner geometry was introduced, some artifacts arose in the reconstructed images, particularly in the center of the phantom. Replacing the step-phantom used for calibration with a wedge phantom led to RSP accuracy close to the ideal case, with no significant dependence of RSP error on insert location or material. The accuracy with the multi-stage detector and NMCPC beam for the cylindrical phantoms was 2.2% in RSP error for inserts of 5 mm radius or more, 0.7 mm in range for the 2.5 mm radius inserts, or better. The pCT scan of the pediatric phantom resulted in mean RSP values within 1.3% of the reference RSP, with a range error under 1 mm, except in exceptional situations of parallel incidence on a boundary between low and high density. Conclusions The pCT imaging technique proved to be a precise and accurate imaging tool, rivalling the current x-rays based techniques, with the advantage of being directly sensitive to proton stopping power rather than photon interaction coefficients. Measured and simulated pCT images were obtained from a wobbled proton beam for the first time. Since the in-silico results are expected to accurately represent the prototype pCT, upcoming measurements using the wedge p...

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The effect of beam purity and scanner complexity on proton CT accuracy

et al. 2017

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“…By measuring the positions and residual energies of the protons behind (and in some designs also in front of) the patient in a series of projections, a RSP image can be reconstructed . Currently, several groups are known to be designing, building, or operating pCT (or heavier ion CT) prototypes and initial reports of RSP accuracy are encouraging …”

Section: Introductionmentioning

confidence: 99%

“…The eventual use of pCT for frequent imaging in treatment position is supported by the fact that pCT dose efficiency, evaluated by metrics such as contrast to noise ratio, is superior to x‐ray CT and may allow lower imaging doses. Recently, pCT scans using imaging doses as low as 1 mGy have been achieved . The imaging dose from pCT may be further reduced by employing the concept of fluence field modulation, where the fluence of particles used for imaging is adjusted within a projection to yield spatially varying image quality.…”

Section: Introductionmentioning

confidence: 99%

“…FMpCT may be achieved by acquiring pCT scans using the pencil beam scanning (PBS) functionality of modern proton therapy facilities instead of the broad beams (cone or wobbled beams typically) currently employed in most pCT prototypes . The use of PBS would greatly simplify the fluence modulation task by allowing the prescription of proton fluence on a pencil beam by pencil beam basis.…”

Section: Introductionmentioning

confidence: 99%

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Experimental fluence‐modulated proton computed tomography by pencil beam scanning

et al. 2018

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In vivo range verification in particle therapy

2018

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Exploitation of the full potential offered by ion beams in clinical practice is still hampered by several sources of treatment uncertainties, particularly related to limitations of our ability to locate the position of the Bragg peak in the tumour. To this end, several efforts are ongoing to improve the characterization of patient position, anatomy and tissue stopping power properties prior to treatment, as well as to enable in-vivo verification of the actual dose delivery, or at least beam range, during or shortly after treatment. This contribution critically reviews methods under development or clinical testing for verification of ion therapy, based on pre-treatment range and tissue probing as well as detection of secondary emissions or physiological changes during and after treatment, trying to disentangle approaches of general applicability from those more specific to certain anatomical locations. Moreover, it discusses future directions, which could benefit from integration of multiple modalities or address novel exploitation of the measurable signals for biologically adapted therapy.

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Operation of the preclinical head scanner for proton CT

Cited by 35 publications

References 15 publications

The effect of beam purity and scanner complexity on proton CT accuracy

The effect of beam purity and scanner complexity on proton CT accuracy

Experimental fluence‐modulated proton computed tomography by pencil beam scanning

In vivo range verification in particle therapy

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