an-automated-radiosynthesis-of-68gaga-fapi-46-for-routine-clinical-use

An Automated Radiosynthesis of [<sup>68</sup>Ga]Ga-FAPI-46 for Routine Clinical Use

[68Ga]Ga-FAPI-46 is a promising new tracer for the imaging of fibroblast activation protein (FAP) by positron emission tomography (PET). Labeled FAP ...

Sir Charles Gairdner Hospital

This study examined the response characteristics of three commercially available radiochromic films when exposed to low energy (50 kVp) X-rays. The aim was to evaluate the films for potential use in 2D dosimetry for a low-kV intraoperative radiotherapy (IORT) device known as the 'Intrabeam'. Dose-response relationships were obtained for Gafchromic EBT, XR-RV2, and XR-QA film in water at several distances from the Intrabeam device. It was found that the dose rates from the source were excessive for use of the XR-QA film, and that all three film types showed significant energy dependence within the limits of measurement uncertainty. Basic modeling of primary X-ray spectra indicated large changes in the lower energy components with distance from the source, and it is hypothesized that the changes in film response are a result of changes in film energy response. This is in contrast to previous studies indicating less or negligible energy response. All films showed non-linearity in response over the ranges examined. These results imply significant limitations for the use of these films for low-kV dosimetry.

Suitability of radiochromic films for dosimetry of very-low energy X-rays.

We measured the excitation functions of (nat)Zn (p,x) reactions up to 17.6MeV, using the stacked-foils activation technique. High-purity natural zinc (and copper) foils were irradiated with proton beams generated by an 18MeV isochronous cyclotron. Activated foils were measured using high-purity Ge gamma spectroscopy to quantify the radionuclides (61)Cu, (66)Ga, (67)Ga, and (65)Zn produced from the reactions. Thick-target integral yields were also deduced from the measured excitation functions of the produced radioisotopes. These results were compared with the published literature and were found to be in good agreement with most reports, particularly those most recently compiled.

Excitation functions of (nat)Zn(p,x) nuclear reactions with proton beam energy below 18 MeV.

The proton beam energy of an isochronous 18MeV cyclotron was determined using a novel version of the stacked copper-foils technique. This simple method used stacked foils of natural copper forming 'thick' targets to produce Zn radioisotopes by the well-documented (p,x) monitor-reactions. Primary beam energy was calculated using the (65)Zn activity vs. depth profile in the target, with the results obtained using (62)Zn and (63)Zn (as comparators) in close agreement. Results from separate measurements using foil thicknesses of 100, 75, 50 or 25µm to form the stacks also concurred closely. Energy was determined by iterative least-squares comparison of the normalized measured activity profile in a target-stack with the equivalent calculated normalized profile, using 'energy' as the regression variable. The technique exploits the uniqueness of the shape of the activity vs. depth profile of the monitor isotope in the target stack for a specified incident energy. The energy using (65)Zn activity profiles and 50-μm foils alone was 18.03±0.02 [SD] MeV (95%CI=17.98-18.08), and 18.06±0.12MeV (95%CI=18.02-18.10; NS) when combining results from all isotopes and foil thicknesses. When the beam energy was re-measured using (65)Zn and 50-μm foils only, following a major upgrade of the ion sources and nonmagnetic beam controls the results were 18.11±0.05MeV (95%CI=18.00-18.23; NS compared with 'before'). Since measurement of only one Zn monitor isotope is required to determine the normalized activity profile this indirect yet precise technique does not require a direct beam-current measurement or a gamma-spectroscopy efficiency calibrated with standard sources, though a characteristic photopeak must be identified. It has some advantages over published methods using the ratio of cross sections of monitor reactions, including the ability to determine energies across a broader range and without need for customized beam degraders.

A new, simple and precise method for measuring cyclotron proton beam energies using the activity vs. depth profile of zinc-65 in a thick target of stacked copper foils.

Article	Year
Suitability of radiochromic films for dosimetry of very-low energy X-rays. Journal of applied clinical medical physics\| PubMed ID: 19918224	2009
Excitation functions of (nat)Zn(p,x) nuclear reactions with proton beam energy below 18 MeV. Applied radiation and isotopes : including data, instrumentation and methods for use in agriculture, industry and medicine\| PubMed ID: 25108597	2014
A new, simple and precise method for measuring cyclotron proton beam energies using the activity vs. depth profile of zinc-65 in a thick target of stacked copper foils. Applied radiation and isotopes : including data, instrumentation and methods for use in agriculture, industry and medicine\| PubMed ID: 26226219	2015

Ali H. Asad

Biography

JoVE Journal Publications

Other Publications