Low current performance of the Bern medical cyclotron down to the pA range

Abstract

A medical cyclotron accelerating H − ions to 18 MeV is in operation at the Bern University Hospital (Inselspital). It is the commercial IBA 18/18 cyclotron equipped with a specifically conceived 6 m long external beam line ending in a separate bunker. This feature is unique for a hospital-based facility and makes it possible to conduct routine radioisotope production for PET diagnostics in parallel with multidisciplinary research activities, among which are novel particle detectors, radiation biophysics, radioprotection, radiochemistry and radiopharmacy developments. Several of these activities, such as radiobiology experiments for example, require low current beams down to the pA range, while medical cyclotrons are designed for high current operation above 10 μA. In this paper, we present the first results on the low current performance of a PET medical cyclotron obtained by ion source, radio-frequency and main coil tuning. With this method, stable beam currents down to (± 1.5 0.5) pA were obtained and measured with a high-sensitivity Faraday cup located at the end of the beam transport line.

Study of the Extracted Beam Energy as a Function of Operational Parameters of a Medical Cyclotron

“…The beam current may vary from a few pA to 150 µA. Currents below 1 µA are a special feature and are obtained by means of a method developed by our group [10] based on the variation of the magnetic field produced by the main coil and the peak voltage of the Radio Frequency (RF). The RF operates at the constant frequency of 42 MHz.…”

Design and verification of an external radiobiological beam port on a 16.5 MeV GE PETtrace proton cyclotron

“…Ohio, United States) was used to measure the proton beam current using the Faraday cup principle. 7 Additionally, an "in-house" developed LabVIEW program was used for more accurate real time measurement and logging of the beam current at a pA level. This system was used for proton transmission measurements and to normalize beam intensity measurements to beam current.…”

“…The preclinical proton beams not using clinical proton therapy accelerators constitute of either modified Van de Graaff accelerators, 3,4 singletron accelerators, 5 or radioisotope production cyclotrons. [6][7][8][9][10] Even if trying to achieve conventional dose rates of 3-5 cGy/s or dose rates larger than 40 Gy/s for flash irradiation, the main obstacle to overcome on a medical cyclotron is to reduce the proton beam current. 11 Proton beam currents during radioisotope productions can range up to 150 µA.…”

“…11 Proton beam currents during radioisotope productions can range up to 150 µA. 7,10,12 Proton beam currents of 2 nA with a proton energy of 15.2 MeV have been assessed by Ghithan et al 13 to generate dose rates in the order of 5 kGy/s in the Bragg peak region.…”

Optimization of Ion Source Head Position in the Central Region of DECY-13 Cyclotron

“…As in the general installation of the ion source in a small cyclotron, a PIG ion source is placed internally to produce H -ions [4][5][6]. Simulations that examine patterns of the beam path in the central region have also been performed [7], but it has not been optimized by means of varying the width of the head-puller gap to obtain the high efficiency of the ion beam extraction and initial ion beam acceleration processes.…”