Narrow Results

Concentrations of the chemotherapeutic agent, cis-diamminedichloro-platinum(II) (CDDP) in NFSa fibrosarcoma tumors were investigated using a conventional PIXE analysis on the basis of an internal standard method to study enhancement of antitumor effects caused by proton therapy combined with CDDP treatment. Results of the PIXE analysis showed that platinum concentration of the tumors treated with CDDP at a single dose of 10 mg/kg was 2.0±0.1 µg/g and persisted at the level at least 6 hours after the administration. The present study demonstrated that the presence of CDDP in the tumor caused an enhanced therapeutic effect on tumor growth delay when CDDP treatment was combined with post proton-irradiation in comparison with CDDP treatment alone or proton therapy alone.

History has shown that energetic particles can be useful for medical applications. From the time, in 1895 when Roentgen discovered X-rays, and in 1913 when Coolidge developed the vacuum X-ray tube, energetic particles have been an important tool for medicine. Development of the appropriate tool for effective and safe radiotherapy requires an in-depth understanding of the application and constraints. Various solutions are possible and choices must be analyzed on the basis of the suitability for meeting the requirements. Some of the requirements of charged particle therapy are summarized and various accelerator options are described and discussed.

The goal of this work is to increase the beam transmission from the cyclotron to the patient location of ocular tumor treatment facility Optis 2 at the Paul Scherrer Institute and thus to reduce the patient treatment times. The examined options for such transmission increase were the installation of local degraders in the patient treatment room and modification of the energy selection collimator settings. The experiments have shown that an improvement of the beam transmission is possible to achieve, however on a cost of an increase in lateral or distal penumbra of the beam. The benefits and drawbacks of the examined options are discussed.

The document summarizes the recent papers, presentations and other public information on Radio-Frequency (RF) Linear Accelerators (linacs) and Fixed-Field Alternating-Gradient (FFAG) accelerators for hadron therapy. The main focus is on technical aspects of these accelerators. This report intends to provide a general overview of the state-of-the-art in those accelerators which could be used in short and middle-term for treating cancer.

Due to the unique “Bragg peak” dose-distribution characteristics of proton beams, the proton therapy (PT) is recognized as one of the most precise and effective radiotherapy methods for tumors. A gantry is required to project the beam onto a tumor at various angles for multiple-field irradiation, and a superconducting beamline can significantly reduce the size and weight of the gantry. A PT system is under development at Huazhong University of Science and Technology (HUST), and this paper presents a comparison study of the beam optics and related design considerations for normal conducting and superconducting gantry beamlines.

A novel concept for a superconducting, fixed-field bending section is presented for use in a proton therapy gantry. The large momentum acceptance of this design allows for treatment over the full proton energy range of 70–220 MeV with fixed field in the superconducting magnets, eliminating the technical risks associated with fast-field ramping to match beam energy changes during treatment. A combined study of beam dynamics and magnet design is shown for such a system in which a simple magnet geometry with straight Nb–Ti racetrack coils is used to produce the desired fields. Particle tracking through this design is compared with clinical requirements for beam spot shape and size at isocenter over the full range of proton energy.

In proton therapy, the last part of the beam transport system is installed on a rotatable gantry, so that the beam can be aimed at the tumor from different angles. Since such a gantry system consists of many dipole and quadrupole magnets, it is typically a 100–200 tons device of more than 10 m in diameter. The use of superconducting (SC) magnets for proton therapy allows gantries to be significantly lighter and potentially smaller, which is attractive for this medical application. In addition to that, SC combined function magnets enable beam optics with a very large momentum acceptance. The latter can be advantageous for patient treatment, since the irradiation time can then be significantly reduced by avoiding magnet current changes. To design such an achromatic system, we performed precise high-order calculations. To reach the required accuracy and to check consistency of the obtained results, we have used different simulation tools in our iterative design approach. Here, we will describe our beam optics calculations in the code COSY Infinity and particle tracking using OPAL (open source software from PSI) in 3D field maps obtained from detailed magnet calculations performed in Opera. Our method has shown to be advantageous in a complicated beam optics study and it reduces the risk of systematic errors in a design.

Proton therapy is an advanced particle radiotherapy technology. Lanzhou University recently designed a new linear accelerator system for proton therapy. In the system, a 750MHz radio frequency quadrupole (RFQ) accelerator was used to complete the initial acceleration of particles. The RFQ can accelerate a proton beam intensity of 1mA from 30keV to 3MeV kinetic energy within a length of 2m. This paper aims to complete the physical design of this high-frequency RFQ, including beam dynamics design, radio frequency (RF) design, and multiphysics analysis. In the dynamics design, a novel design strategy for controlling the longitudinal emittance was adopted to improve the output beam quality of the RFQ. The simulation results showed that the RFQ outlet longitudinal emittance was controlled below 0.1 $\pi$ mm mrad. In the RF design, the pi-mold rod structure was applied to RFQ at such high frequencies for the first time. After the whole cavity simulation, it was found that the separation between the operating frequency of the RFQ cavity and its closest dipole mode reached 58.3MHz, and its quality factor reached 6352. Finally, a multiphysics analysis was performed. The analysis showed that the maximum temperature rise of the RFQ cavity was less than $2.5^{\circ }$C and the frequency drift due to heating was 18kHz. This paper presents the current status of the design of this new linear accelerator. Compared with previous RFQs, the new RFQ has a very high transmission efficiency and higher RF stability.

The use of radiofrequency linacs for hadrontherapy was proposed about 20 years ago, but only recently has it been understood that the high repetition rate together with the possibility of very rapid energy variations offers an optimal solution to the present challenge of hadrontherapy: "paint" a moving tumor target in three dimensions with a pencil beam. Moreover, the fact that the energy, and thus the particle range, can be electronically adjusted implies that no absorber-based energy selection system is needed, which, in the case of cyclotron-based centers, is the cause of material activation. On the other side, a linac consumes less power than a synchrotron. The first part of this article describes the main advantages of high frequency linacs in hadrontherapy, the early design studies, and the construction and test of the first high-gradient prototype which accelerated protons. The second part illustrates some technical issues relevant to the design of copper standing wave accelerators, the present developments, and two designs of linac-based proton and carbon ion facilities. Superconductive linacs are not discussed, since nanoampere currents are sufficient for therapy. In the last two sections, a comparison with circular accelerators and an overview of future projects are presented.

Dielectric wall accelerators, a class of induction accelerators, employ a novel insulating beam tube to impress a longitudinal electric field on a bunch of charged particles. The surface flashover characteristics of this tube may permit the attainment of accelerating gradients on the order of 100 MV/m for accelerating pulses on the order of a nanosecond in duration. A virtual traveling wave of excitation along the tube is produced at any desired speed by controlling the timing of pulse-generating modules that supply a tangential electric field to the tube wall. Because of the ability to control the speed of this virtual wave, the accelerator is capable of handling any charge-to-mass-ratio particle; hence it can be used for electrons, protons and any ion. The accelerator architectures, key technologies and development challenges will be described.

Particle therapy is the expanding radiotherapy treatment option of choice for cancer. Its cost, however, is currently hindering its worldwide expansion. Also, the ideal application of particle therapy is restricted by a series of unsolved technical challenges. Both the cost and technical limitations are directly traceable to dependence on legacy accelerators and their associated treatment possibilities. This chapter is written to address these needs. Firstly, a technical overview is presented of photon and particle therapy for cancer tumours. Secondly, the underlying limitations of the existing legacy systems are identified, especially those related to accelerators, and suggestions are made for current and future developments to address these shortcomings. The legacy systems referred to here are of the slow scanning variety using large, circular accelerators.

This paper also attempts to make a scientific comparison of the various types of accelerators currently used or being developed for particle therapy.

The following procedure is pursued to perform a comparison between various types of accelerators:

• ⁽¹⁾The parameters which are pertinent to particle therapy accelerators (‘specified parameters’) are identified from clinical efficiency and overall cost considerations.
• ⁽²⁾The range and values of ‘specified parameters’ associated with each type of particle therapy accelerator are identified.
• ⁽³⁾A comparison is made on the best match between the various types of accelerators for each of the ‘specified parameters,’ i.e., the best in class accelerator, when compared to each criterion.
• ⁽⁴⁾Based on this match, an overall conclusion is made on the type of accelerator which best fits the needs for particle therapy.

Particle detection instrumentation to address the in vivo verifications of proton dose and range is under development as part of a proton therapy research program focused on patient quality assurance. For in vivo proton range verification, a collimated gamma detector array is under construction to indirectly measure the position of the Bragg peak for each proton beam spot to within 1–2 mm precision. For dose flux verification, a proton fluence detector based on the technology of the Micromegas is under construction. This detector has an active area of about 100 cm², coordinate resolution of better than 1 mm, and handling of incident proton beam fluxes of 10⁹–10¹³ particles/s.

Particle therapy is the expanding radiotherapy treatment option of choice for cancer. Its cost, however, is currently hindering its worldwide expansion. Also, the ideal application of particle therapy is restricted by a series of unsolved technical challenges. Both the cost and technical limitations are directly traceable to dependence on legacy accelerators and their associated treatment possibilities. This chapter is written to address these needs. Firstly, a technical overview is presented of photon and particle therapy for cancer tumours. Secondly, the underlying limitations of the existing legacy systems are identified, especially those related to accelerators, and suggestions are made for current and future developments to address these shortcomings. The legacy systems referred to here are of the slow scanning variety using large, circular accelerators.

This paper also attempts to make a scientific comparison of the various types of accelerators currently used or being developed for particle therapy.

The following procedure is pursued to perform a comparison between various types of accelerators:

• The parameters which are pertinent to particle therapy accelerators (‘specified parameters’) are identified from clinical efficiency and overall cost considerations.
• The range and values of ‘specified parameters’ associated with each type of particle therapy accelerator are identified.
• A comparison is made on the best match between the various types of accelerators for each of the ‘specified parameters,’ i.e., the best in class accelerator, when compared to each criterion.
• Based on this match, an overall conclusion is made on the type of accelerator which best fits the needs for particle therapy.

The use of radiofrequency linacs for hadrontherapy was proposed about 20 years ago, but only recently has it been understood that the high repetition rate together with the possibility of very rapid energy variations offers an optimal solution to the present challenge of hadrontherapy: “paint” a moving tumor target in three dimensions with a pencil beam. Moreover, the fact that the energy, and thus the particle range, can be electronically adjusted implies that no absorber-based energy selection system is needed, which, in the case of cyclotron-based centers, is the cause of material activation. On the other side, a linac consumes less power than a synchrotron. The first part of this article describes the main advantages of high frequency linacs in hadrontherapy, the early design studies, and the construction and test of the first high-gradient prototype which accelerated protons. The second part illustrates some technical issues relevant to the design of copper standing wave accelerators, the present developments, and two designs of linac-based proton and carbon ion facilities. Superconductive linacs are not discussed, since nanoampere currents are sufficient for therapy. In the last two sections, a comparison with circular accelerators and an overview of future projects are presented.

Dielectric wall accelerators, a class of induction accelerators, employ a novel insulating beam tube to impress a longitudinal electric field on a bunch of charged particles. The surface flashover characteristics of this tube may permit the attainment of accelerating gradients on the order of 100 MV/m for accelerating pulses on the order of a nanosecond in duration. A virtual traveling wave of excitation along the tube is produced at any desired speed by controlling the timing of pulse-generating modules that supply a tangential electric field to the tube wall. Because of the ability to control the speed of this virtual wave, the accelerator is capable of handling any charge-to-mass-ratio particle; hence it can be used for electrons, protons and any ion. The accelerator architectures, key technologies and development challenges will be described.