Advanced Radiation DOSimetry phantom (ARDOS): a versatile breathing phantom for 4D radiation therapy and medical imaging.

A novel breathing phantom was designed for being used in conventional and ion-beam radiotherapy as well as for medical imaging. Accurate dose delivery and patient safety are aimed to be verified for four-dimensional (4D) treatment techniques compensating for breathing-induced tumor motion. The phantom includes anthropomorphic components representing an average human thorax. It consists of real tissue equivalent materials to fulfill the requirements for dosimetric experiments and imaging purposes. The different parts of the torso (lungs, chest wall, and ribs) and the tumor can move independently. Simple regular movements, as well as more advanced patient-specific breathing cycles are feasible while a reproducible setup can be guaranteed. The phantom provides the flexibility to use different types of dosimetric devices and was designed in a way that it is robust, transportable and easy to handle. Tolerance levels and the reliability of the phantom setup were determined in combination with tests on motion accuracy and reproducibility by using infrared optical tracking technology. Different imaging was performed including positron emission tomography imaging, 4D computed tomography as well as real-time in-room imaging. The initial dosimetric benchmarking studies were performed in a photon beam where dose parameters are predictable and the dosimetric procedures well established.

On the applicability of [18F]FBPA to predict L-BPA concentration after amino acid preloading in HuH-7 liver tumor model and the implication for liver boron neutron capture therapy.

INTRODUCTION: In recent years extra-corporal application of boron neutron capture therapy (BNCT) was evaluated for liver primary tumors or liver metastases. A prerequisite for such a high-risk procedure is proof of preferential delivery and high uptake of a 10B-pharmaceutical in liver malignancies. In this work we evaluated in a preclinical tumor model if [18F]FBPA tissue distribution measured with PET is able to predict the tissue distribution of [10B]L-BPA. METHODS: Tumor bearing mice (hepatocellular carcinoma cell line, HuH-7) were either subject of a [18F]FBPA-PET scan with subsequent measurement of radioactivity content in extracted organs using a gamma counter or injected with [10B]L-BPA with tissue samples analyzed by prompt gamma activation analysis (PGAA) or quantitative neutron capture radiography (QNCR). The impact of L-tyrosine, L-DOPA and L-BPA preloading on the tissue distribution of [18F]FBPA and [10B]L-BPA was evaluated and the pharmacokinetics of [18F]FBPA investigated by compartment modeling. RESULTS: We found a significant correlation between [18F]FBPA and [10B]L-BPA uptake in tumors and various organs as well as high accumulation levels in pancreas and kidneys as reported in previous studies. Tumor-to-liver ratios of [18F]FBPA ranged from 1.2 to 1.5. Preloading did not increase the uptake of [18F]FBPA or [10B]L-BPA in any organ and compartment modeling showed no statistically significant differences in [18F]FBPA tumor kinetics. CONCLUSIONS: [18F]FBPA-PET predicts [10B]L-BPA concentration after amino acid preloading in HuH-7 hepatocellular carcinoma models. Preloading had no effect on tumor uptake of [18F]FBPA. ADVANCES IN KNOWLEDGE: Despite differences in chemical structure and administered dose [18F]FBPA and [10B]L-BPA demonstrate an equivalent biodistribution in a preclinical tumor model. IMPLICATIONS FOR PATIENT CARE: [18F]FBPA-PET is suitable for treatment planning and dose calculations in BNCT applications for liver malignancies. However, alternative tracers with more favorable tumor-to-liver ratios should be investigated.

Analysis of computational problems expressing the overall uncertainties: photons, neutrons and electrons.

In the frame of the EU Coordination Action CONRAD (coordinated network for radiation dosimetry), WP4 was dedicated to work on computational dosimetry with an action entitled 'Uncertainty assessment in computational dosimetry: an intercomparison of approaches'. Participants attempted one or more of eight problems. This paper presents the results from problems 4-8-dealing with the overall uncertainty budget estimate; a short overview of each problem is presented together with a discussion of the most significant results and conclusions. The scope of the problems discussed here are: the study of a (137)Cs calibration irradiator; the manganese bath technique; the iron sphere experiment using neutron time-of-flight technique; the energy response of a RADFET detector and finally the sensitivity and uncertainty analysis for the recoil-proton telescope discussed in the companion paper.