Nunzio Burgio

Monte Carlo simulation and radiometric characterization of proton irradiated [18O]H2O for the treatment of the waste streams originated from [18F]FDG synthesis process

The aim of this work is quantifying the radionuclidic impurities of the irradiated [(18)O]water originated by the [(18)F]FDG synthesis process, and characterizing, from a radioprotection point of view, the waste streams produced. Two samples of 2.4ml [(18)O]H(2)O, contained in two different target cells, have been irradiated with a proton current of 37μA in a PETtrace cyclotron for about one hour each; after irradiation, without performing any chemical purification process but waiting only for the (18)F decay, they have been transferred in two vials and measured by HPGe gamma spectrometry and, subsequently, by Liquid Scintillation Counting. Previously, Monte Carlo calculations had been carried out in order to estimate the radionuclides generated within the target components ([(18)O]H(2)O, silver body and Havar® foil), with the aim to identify the nuclides expected to be found in the irradiated water. Experimental results for the two samples, normalized to the same irradiation time, show practically the same value of tritium concentration (about 36kBq/ml) while gamma emitters activity concentrations exhibit a greater spread. Considering that tritium derives from water activation while other pollutants are caused by activated cell materials released into water through erosion/corrosion mechanisms, such a spread is likely to be attributable to differences in the proton beam shape and position (production of different natural circulation patterns inside the target and different erosion mechanisms of the target cell walls). Both tritium and the other radioactive pollutants exhibit absolute values of activity and activity concentrations below the exemption limits set down in EURATOM Council Directive 96/29.

Experimental Results of an Accelerator-Driven Neutron Activator for Medical Radioisotope Production

In the framework of the EC funded INBARCA project (Innovative Nanosphere Brachytherapy with Adiabatic Resonance Crossing using Accelerators) a compact, accelerator driven neutron activator has been designed and constructed, with the aim of efficiently utilising ion-beam generated neutrons for the production of radioactive nanoparticles for brachytherapy. The design is based on a modified version of the Adiabatic Resonance Crossing concept, first proposed by C. Rubbia of CERN. The neutron activator has been tested in two experimental configurations, with and without a central lead block. The activation performance on different materials was quantified by γ-spectrometry. Monte Carlo simulations accompanied all experimental runs, and neutron unfolding techniques were used to derive the experimental neutron spectrum. This paper compares the simulated and the unfolded neutron spectra thus obtained, as well as the experimental and simulated activation results for pure Au, Ag, Mo, Ni, Ho and Re foils as well as for Re and Ho nanoparticles.

Imaging evaluation of CsI(Tl) arrays for scintimammography

We propose the use of Hamamatsu R7600-C8 position sensitive photomultiplier tubes (PSPMTs) as a practical tool for imaging in scintimammography, through the evaluation of performance as a function of scintillation array pixellation in collimated configurations. A number of CsI(Tl) scintillating arrays with different pixel size and thickness are tested. The very high intrinsic spatial resolution of R7600 PSPMTs made it easy to implement a look up table to correct accurately the gain nonuniformity response and position distortion. Finally, an SNR analysis of a small tumor in scintimammography as a function of crystal pixellation is performed by means of a simple breast phantom.

New localization technique for breast cancer biopsy: mammotome guidance with imaging probe.

Aims and Background The “Imaging probe” (IP) is a small, portable, high-resolution gamma camera to be used in radioguided surgery. The present work discusses a special prototype designed for guiding biopsies. The IP was mounted to a Fischer digital X-ray stereotactic core biopsy system in such a way that biopsy could be guided simultaneously by X-ray stereotaxis and 99mTc-Sestamibi (MIBI) images from IP. Methods The IP field of view was 22.8 × 22.8 mm2, with a spatial resolution of approx. 2.5 mm. We used off-line software for image fusion on a dedicated Pentium III portable PC. It was matched with a Fischer digital X-ray stereotactic biopsy system dedicated to direct the mammotome towards breast opacities. The operator was allowed to slightly correct the direction of the mammotome needle taking into account stereotactic X-ray, scintigraphic and fused images. Biopsy samples were counted by IP before they were sent to the pathologist. Results High-resolution IP scintigraphy showed substantial, though not exact, matching between MIBI hot spots and X-ray opacities. More than one hot spot was detected even in the smallest (0.6 cm) lesion. Post-biopsy scintigraphy showed absence of significant hot spots in two patients, whereas in the third patient one of the three hot spots was still partially present. All lesions showed cancer on histological examination. Conclusions Measurement of radioactivity in biopsy specimens confirmed the heterogeneous distribution of radioactivity within cancers that IP had detected before biopsy.

Clinical use of an imaging probe in breast cancer surgery

Aim Portable cameras allow easy transfer of the detector, and thus of radioisotope imaging, to the operating room. In this paper we describe our preliminary experience in radionuclide imaging of breast cancer with a 22.8 × 22.8 mm2 field-of-view minicamera called “Imaging Probe” (IP). Methods Breast cancer detection by IP was performed to guide biopsy, in particular open biopsy, or help fine-needle or core-needle positioning when the main guidance method was ultrasonography or digital radiography. 99mTc Sestamibi (MIBI) was injected 1 h before imaging and biopsy to 14 patients with suspected or known breast cancer. Scintigraphic images were acquired before and after biopsy in each patient. The surgeon was allowed to take into account scintigraphic images as well as previously performed mammograms and ultrasonography. Results High-resolution IP images were able to guide biopsy toward cancer or toward washout zones of cancer, which are thought to be chemoresistant, in seven patients out of 10. Four patients in whom IP and MIBI were unable to guide biopsy were found not to have cancer. Conclusions Our study confirms the ability of IP to guide breast biopsy even when our minicamera has to be handled manually by trained physicians during surgery.

DISIS - a computer simulation code for discrete scintillation imagers

A computer simulation code has been developed in order to foresee the response of discrete scintillation imaging devices. Discrete Scintillation Imager Simulator (DISIS) has been designed for imagers based on a scintillation array coupled to a position sensitive light sensor (like position sensitive photomultiplier tube or avalanche photodiode array) by a planar light guide. The simulator is a deterministic code that uses: (i) a model describing the single photon light distribution emerging from a crystal pixel for charge integrals evaluation; (ii) the assigned algorithm for centroid calculation; and (iii) the Gaussian spread for localizing, crystal by crystal, the events on the image. In particular DISIS allows us to study the spatial response over the imager field of view changing parameters individually. The imager optimization can be obtained searching an acceptable pixel identification. To this aim a good trade-off between the spread of light distribution, the light sampling capability over the light-sensor area and the centroiding algorithm has to be found.