Yuan-Hao Liu

BNCT for locally recurrent head and neck cancer: preliminary clinical experience from a phase I/II trial at Tsing Hua Open-Pool Reactor.

To introduce our preliminary experience of treating locally and regionally recurrent Head and Neck cancer patients at Tsing Hua Open-Pool Reactor in Taiwan, four patients (M/F=3/1, median age 68 Y/O) were enrolled. BNCT with BPA (400 mg/kg) injected in 2 phases and prescription dose of 12-35 Gy (Eq.)/fraction for 2 fractions at 30 day interval can be given with sustained blood boron concentration and tolerable early toxicities for recurrent H & N cancer.

Neutron spectra measurement and comparison of the HFR and THOR BNCT beams

This paper aims to measure the spectra of HB11 (high flux reactor, HFR) and the Tsing Hua open-pool reactor (THOR) boron neutron capture therapy (BNCT) beams by multiple activation foils. The self-shielding corrections were made with the aid of MCNP calculations. The initial spectra were adjusted by a sophisticated process named coarse-scaling adjustment using SAND-EX, which can adjust a given coarse-group spectrum into a fine-group structure, i.e. 640 groups, with excellent continuity. The epithermal neutron flux of the THOR beam is about three times of HB11. The thermal neutron flux, boron and gold reaction rates along the central axis of a PMMA phantom are calculated for both adjusted spectra for comparison.

Fractionated BNCT for locally recurrent head and neck cancer: experience from a phase I/II clinical trial at Tsing Hua Open-Pool Reactor.

To introduce our experience of treating locally and regionally recurrent head and neck cancer patients with BNCT at Tsing Hua Open-Pool Reactor in Taiwan, 12 patients (M/F=10/2, median age 55.5 Y/O) were enrolled and 11 received two fractions of treatment. Fractionated BNCT at 30-day interval with adaptive planning according to changed T/N ratios was feasible, effective and safe for selected recurrent head and neck cancer in this trial.

BNCT EPITHERMAL NEUTRON BEAM MAPPING BY USING INDIRECT NEUTRON RADIOGRAPHY

Abstract This paper aims to measure the neutron flux distribution over the cross section of the boron neutron capture therapy epithermal neutron beam at the Tsing Hua Open-pool Reactor (THOR) by using indirect neutron radiography. It is successfully performed using an aluminum plate coupled with an imaging plate (IP). The developed high-resolution image represents the relative distribution of the neutron flux across the aluminum plate. The horizontal profiles of 28Al activity, according to the measurement using IP and calculations using MCNP with different angular source distributions, were given. In addition, horizontal profiles of 56Mn and 198Au activities measured using AuAl and MnNi foils, respectively, were provided. From the comparison between the measurements and calculations, source angular characteristics of the beam were inferred.

A preliminary study on using the radiochromic film for 2D beam profile QC/QA at the THOR BNCT facility

The GAFCHROMIC(®) EBT2 dosimetry film has been studied as a rapid QC/QA tool for 2D dose profile mapping in the BNCT beam at THOR. The pixel values of the EBT2 film image were converted to the 2D dose profile using a dose calibration curve obtained by 6-MV X-ray. The reproducibility of the 2D dose profile measured using the EBT2 film in the PMMA phantom was preliminarily found to be acceptable with uncertainties within about ±2 to ±3.5%. It is found that the EBT2 measured dose profile consisted of both gamma-ray components and neutron contributions. Therefore, the dose profile measured using the EBT2 film is significantly different from the neutron flux profile measured using the indirect neutron radiography method. Further study of the influence of neutrons to the response of the EBT2 film is indispensible for the absolute dose profile determination in a BNCT beam.

Neutron flux mapping inside a cubic and a head PMMA phantom using indirect neutron radiography.

This study aims to measure the two-dimensional (2D) neutron spatial distribution inside a cubic and a head PMMA phantom for the purpose of further comparison with the treatment planning. The measurements were made by using the indirect neutron radiography (INR), which utilized a thin copper foil and the imaging plate. The developed image provides satisfactory spatial resolution and very low statistical error (< 1%). As to the time cost, the whole procedure normally takes less than 3 h. The result shows that the indirect neutron radiography can be a quick and reliable method to provide a 2D neutron spatial distribution inside a phantom.

Quality control and quality assurance procedures at the THOR BNCT facility.

Various quality control (QC) and quality assurance (QA) procedures of the boron neutron capture therapy (BNCT) beam at the Tsing Hua Open-pool Reactor (THOR) are established to ensure beam availability and quality. The QC/QA methods mainly employ foil activation and paired ionization chambers, respectively, for beam intensity check and dose assessment. Beam intensity is monitored on-line by using three dead-time corrected fission chambers. In addition to the periodic QC/QA activities regarding beam quality and the monitoring system, the quick QC/QA performed in an all-in-one phantom will be executed less than 70 min before the clinical treatment to guarantee beam quality. The QC/QA procedures have been gradually established and the actual performance satisfied the preset criteria defined for the BNCT facility at THOR.

Performance evaluation of the source description of the THOR BNCT epithermal neutron beam

This paper aims to evaluate the performance of the source description of the THOR BNCT beam via different measurement techniques in different phantoms. The measurement included (1) the absolute reaction rate measurement of a set of triple activation foils, (2) the neutron and gamma-ray dose rates measured using the paired ionization chamber method, and (3) the relative reaction rate distributions obtained using the indirect neutron radiography. Three source descriptions, THOR-Y09, surface source file RSSA, and THOR-50C, were tested. The comparison results concluded that THOR-Y09 is a well-tested source description not only for neutron components, but also for gamma-ray component.

The refinement of dose assessment of the THOR BNCT beam.

A refined dose assessment method has been used now in the THOR BNCT facility, which takes into account more delicate corrections, carefully handled calibration factors, and the spectrum- and kerma-weighted k(t) value. The refined method solved the previous problem of negative derived neutron dose in phantom at deeper positions. With the improved dose assessment, the calculated and measured gamma-ray dose rates match perfectly in a 15×15×15 cm(3) PMMA phantom.

Improvement of Activation-Detector-Based Spectrum Unfolding Technique for BNCT

Energy spectrum determination of an epithermal neutron beam for BNCT is always a critical issue to its dose accuracy. The spectrum is generally determined by multiple activation foils with few-channel unfolding codes. This study aims to make improvement to the activation-detector-based unfolding technique via introducing specially designed detector complexes in addition to the commonly applied multiple activation foils. The extra detector complexes can obtain valuable information from planned, artificial perturbations posed on the incident epithermal neutron beam, without the need of modifying the unfolding algorithm. Two different types of BNCT beams, one is based on nuclear reactor and the other one is based on low energy accelerator, with two different conditions were tested: under- and over-moderated cases. The spectra adjusted by using the original foil package containing 11 foils and the improved system are compared based on the square root of the sum of deviation squares. The specially designed detector complexes have shown the great ability to significantly reduce the deviations between the unfolded spectra and standard solutions. For a seriously under-moderated case tested in this work, the improvement can even reach more than 400% in deviation reduction.