Francisco Malano

Development and characterization of a microCT facility

This work reports the design, construction, characterization and application of a novel X-ray imaging beamline at Laboratorio de Investigación e Instrumentación en Física Aplicada a la Medicina e Imágenes por Rayos X - LIIFAMIRx - University of Cordoba and Institute of Physics E. Gaviola - CONICET, Argentina. This development is the first phase in the construction of the integral facility for combining different imaging modalities, like absorption contrast images by primary and scattering contributions, high-resolution micro-tomography, elastic scattering and X-ray fluorescence scanning for chemical composition and surface characterizations. The progress and results here reported concern mainly to the micro-tomography beam-line. This technique is already operative and it was used for several academic researches, application studies and services. The obtained results for the characterization of organic and inorganic samples demonstrated the feasibility and reliability of the developed facility. Accordingly, this work reports specific characteristics about its design, construction, and operation supporting its employment in a wide range of especial applications that might not be accomplished by other available techniques. Moreover, some application studies, mainly focused on biological samples, are presented.

Optimization of the sensitivity/doses relationship for a bench-top EDXRF system used for in vivo quantification of gold nanoparticles

The present work is devoted to optimizing the sensitivity-doses relationship of a bench-top EDXRF system, with the aim of achieving a detection limit of 0.010mg/ml of gold nanoparticles in tumor tissue (clinical values expected), for doses below 10mGy (value fixed for in vivo application). Tumor phantoms of 0.3cm3 made of a suspension of gold nanoparticles (15nm AurovistTM, Nanoprobes Inc.) were studied at depths of 0-4mm in a tissue equivalent cylindrical phantom. The optimization process was implemented configuring several tube voltages and aluminum filters, to obtain non-symmetrical narrow spectra with fixed FWHM of 5keV and centered among the 11.2-20.3keV. The used statistical figure of merit was the obtained sensitivity (with each spectrum at each depth) weighted by the delivered surface doses. The detection limit of the system was determined measuring several gold nanoparticles concentrations ranging from 0.0010 to 5.0mg/ml and a blank sample into tumor phantoms, considering a statistical fluctuation within 95% of confidence. The results show the possibility of obtaining a detection limit for gold nanoparticles concentrations around 0.010mg/ml for surface tumor phantoms requiring doses around 2mGy.

Internal dosimetry for alpha emitters radiopharmaceuticals in biological tissue studied with the FLUKA code

Nuclear medicine clinical practices for neoplasic disease diagnose and treatment are based on the incorporation of α , β and γ radiotracers and radiopharmaceuticals, which might be associated with potential damage. Thus, being necessary accurate dosimetry strategies. In vivo absorbed dose appears as an ideal solution. However, its implementation in clinics does not attain enough reliability. In this sense, different approaches were proposed for internal dosimetry calculations. This work presents a novel analytical-numerical approach for internal dosimetry purposes. Dedicated Monte Carlo simulations were performed by subroutines adapted from the FLUKA code. In-water EDK were evaluated at different photon energies and some typical γ-emitters radiopharmaceuticals; whereas DPK were obtained for both αand β emitters. Additionally, EDK and DPK were calculated for several biological tissues.

Intrinsic spatial resolution limitations due to differences between positron emission position and annihilation detection localization

Since its successful implementation for clinical diagnostic, positron emission tomography (PET) represents the most promising medical imaging technique. The recent major growth of PET imaging is mainly due to its ability to trace the biologic pathways of different compounds in the patient’s body, assuming the patient can be labeled with some PET isotope. Regardless of the type of isotope, the PET imaging method is based on the detection of two 511-keV gamma photons being emitted in opposite directions, with almost 180o between them, as a consequence of electronpositron annihilation. Therefore, this imaging method is intrinsically limited by random uncertainties in spatial resolutions, related with differences between the actual position of positron emission and the location of the detected annihilation. This study presents an approach with the Monte Carlo method to analyze the influence of this effect on different isotopes of potential implementation in PET.

3D dose and TCP distribution for radionuclide therapy in nuclear medicine

A common feature to any radiant therapy is that lesion and health tissue dosimetry provides relevant information for treatment optimization along with dose‐efficacy and dose‐complication correlation studies. Nowadays, different radionuclide therapies are commonly available, assessing both systemic and loco‐regional approach and using different alfa‐, beta–and gamma‐emitting isotopes and binding molecules. It is well established, that specific dosimetric approaches become necessary according to each therapy modality. Sometimes, observed activity distribution can be satisfactory represented by simple geometrical models. However, Monte Carlo techniques are capable of better approaches, therefore becoming sometimes the only way to get dosimetric data since the patient‐specific situation can not be adequately represented by conventional dosimetry techniques. Therefore, due to strong limitations of traditional and standard methods, this work concentrates on the development of a dedicated and novel calculation s...

A computational tool for evaluating the exposure risk in nuclear medicine treatments

A computational tool was developed with the aim of evaluating radiation exposure levels corresponding to patients and other exposed people, such as medical staff or chaperones, during typical nuclear medicine procedures. The calculation system is based on Monte Carlo subroutines adapted from the code PENELOPE and devoted to perform energy deposition according to the user-defined set-up. The computation tool offers a comfortable and user-friendly graphic interface for results processing and visualisation. Relevant procedure features, such as treatment room and facility, spatial distribution, source and target phantom as well as radioisotope type, can be easily introduced to the calculation code; this emphasises the versatility and potential of the computational tool. The application of the developed system to simple situations in nuclear medicine showed the reliability and feasibility of the proposed method. The obtained exposure risk maps proved to be useful to establish safe zones there where expositions do not exceed radioprotection tolerances.