Preliminary study of metabolic radiotherapy with $^{188}$Re via small animal imaging
A. Antoccia\address[biorm3]{Dept. of Biology, Univ. Roma3, V.le G. Marconi, I-00146 Roma}\address[infnrm3]{INFN, Sezione Roma3, Via della Vasca Navale 84, I-00146 Roma}
G. Baldazzi\address[fisbo]{Dept. of Physics, Univ. Bologna, V.le C. Berti-Pichat 6/2, I-40127 Bologna}\address[infnbo]{INFN, Sezione Bologna, V.le C. Berti-Pichat 6/2, I-40127 Bologna}
M. Bello\address[fispd]{Dept. of Physics, Univ. Padova, Via F. Marzolo 8, I-35131 Padova}\address[lnl]{INFN - LNL, V.le dell'Universit\`a 2, I-35020 Legnaro}
D. Bernardini\address[vetpd]{Dip. Scienze Cliniche Veterinarie, Univ. Padova, c/o Agripolis, V.le dell'Universit\`a 16, I-35020 Legnaro} P. Boccaccio\addressmark[lnl]
D. Bollini\addressmark[fisbo]\addressmark[infnbo]
F.~de~Notaristefani\address[fisrm3]{Dept. of Physics, Univ. Roma3, Via della Vasca Navale 84, I-00146 Roma}\addressmark[infnrm3]
F. Garibaldi\address[iss]{Ist. Superiore di Sanit\`a, V.le Regina Elena 299, I-00161 Roma} G. Hull\addressmark[fisrm3]\addressmark[infnrm3]
U.~Mazzi\address[scfarmpd]{Dept. of Pharm. Sc., Univ. Padova, Via F. Marzolo 5, I-35131 Padova}
G. Moschini\addressmark[fispd]\addressmark[lnl]
A.~Muciaccio\address[facfarmbo]{Faculty of Pharmacy, Univ. Bologna, Via S. Donato 19/2, I-40126 Bologna}\thanks{present address: Via Parigi 5, I-06019 Umbertide}
V. Orsolini Cencelli\addressmark[infnrm3]
G.~Pancaldi\addressmark[infnbo]
R. Pani\address[fisrm1]{Dip. Medicina Sperimentale e Patologia, Univ. Roma1, V.le Regina Elena 324, I-00161 Roma}\address[infnrm1]{INFN, Sezione Roma1, P.le Aldo Moro 2, I-00185 Roma} A.~Perrotta\addressmark[infnbo]
M.~Riondato\addressmark[scfarmpd]
A.~Rosato\address[sconcpd]{Dept. of Oncological and Surgical Sc., Univ. of Padova, Via Gattamelata 64, I-35128 Padova}
A.~Sgura\addressmark[biorm3]\addressmark[infnrm3]
C.~Tanzarella\addressmark[biorm3]\addressmark[infnrm3]
N. Uzunov\addressmark[lnl]\address[shumen]{Dept. of Natural Sciences, ``K. Preslavsky'' Univ. of Shumen, Bulgaria} and M. Zuffa\addressmark[infnbo]
$^{188}$Re is a $\beta^-$ (Emax = 2.12 MeV) and $\gamma$ (155 keV) emitter. Since its chemistry is similar to that of the largely employed tracer, $^{99m}$Tc, molecules of hyaluronic acid (HA) have been labelled with $^{188}$Re %rhenium-188 to produce a target specific radiopharmaceutical. The radiolabeled compound, i.v. injected in healthy mice, is able to accumulate into the liver after a few minutes. %it can be linked to molecules of %hyaluronic acid (HA), which carry it around in the body to specific sites, %e.g. to the liver. To study the effect of metabolic radiotherapy in mice, we have built a small gamma camera based on a matrix of YAP:Ce crystals, with 0.6$\times$0.6$\times$10 mm$^3$ pixels, read out by a R2486 Hamamatsu PSPMT. A high-sensitivity 20 mm thick lead parallel-hole collimator, with hole diameter 1.5 mm and septa of 0.18 mm, is placed in front of the YAP matrix. %%The detector is triggered using the last dynode and the photon impact is %%reconstructed by charge division reading x1, x2, y1, y2 lines. Preliminary results obtained with various phantoms containing a solution of $^{188}$Re and with C57 black mice injected with the $^{188}$Re-HA solution are presented. To increase the space resolution and to obtain two orthogonal projections simultaneously we are building in parallel two new cameras to be positioned at 90 degrees. They use a CsI(Tl) matrix with 1$\times$1$\times$5 mm$^3$ pixels read out by H8500 Hamamatsu Flat panel PMT. %%Parallel-hole collimators 20 mm thick, with 1 mm diameter hexagonal holes %%and 0.18 mm thick septa, are mounted in front of the scintillators. %%The front-end electronics has been designed using MPX-08 chips. \vspace{1pc}
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% declarations for front matter
\title{
Preliminary study of metabolic radiotherapy with $^{188}$Re via small animal imaging
}

\author{A. Antoccia\address[biorm3]{Dept. of Biology, Univ. Roma3, V.le G. Marconi, I-00146 Roma}\address[infnrm3]{INFN, Sezione Roma3, Via della Vasca Navale 84, I-00146 Roma}, 
        G. Baldazzi\address[fisbo]{Dept. of Physics, Univ. Bologna, V.le C. Berti-Pichat 6/2, I-40127 Bologna}\address[infnbo]{INFN, Sezione Bologna, V.le C. Berti-Pichat 6/2, I-40127 Bologna},
        M. Bello\address[fispd]{Dept. of Physics, Univ. Padova, Via F. Marzolo 8, I-35131 Padova}\address[lnl]{INFN - LNL, V.le dell'Universit\`a 2, I-35020 Legnaro},
        D. Bernardini\address[vetpd]{Dip. Scienze Cliniche Veterinarie, Univ. Padova, c/o Agripolis, V.le dell'Universit\`a 16, I-35020 Legnaro}
        P. Boccaccio\addressmark[lnl],
        D. Bollini\addressmark[fisbo]\addressmark[infnbo], 
        F.~de~Notaristefani\address[fisrm3]{Dept. of Physics, Univ. Roma3, Via della Vasca Navale 84, I-00146 Roma}\addressmark[infnrm3],
        F. Garibaldi\address[iss]{Ist. Superiore di Sanit\`a, V.le Regina Elena 299, I-00161 Roma} 
        G. Hull\addressmark[fisrm3]\addressmark[infnrm3],
        U.~Mazzi\address[scfarmpd]{Dept. of Pharm. Sc., Univ. Padova, Via F. Marzolo 5, I-35131 Padova},
        G. Moschini\addressmark[fispd]\addressmark[lnl],
        A.~Muciaccio\address[facfarmbo]{Faculty of Pharmacy, Univ. Bologna, Via S. Donato 19/2, I-40126 Bologna}\thanks{present address: Via Parigi 5, I-06019 Umbertide}, 
        F.-L.~Navarria\addressmark[fisbo]\addressmark[infnbo]\thanks{e-mail: navarria@bo.infn.it},
        V. Orsolini Cencelli\addressmark[infnrm3],
        G.~Pancaldi\addressmark[infnbo],
        R. Pani\address[fisrm1]{Dip. Medicina Sperimentale e Patologia, Univ. Roma1, V.le Regina Elena 324, I-00161 Roma}\address[infnrm1]{INFN, Sezione Roma1, P.le Aldo Moro 2, I-00185 Roma}
        A.~Perrotta\addressmark[infnbo],
        M.~Riondato\addressmark[scfarmpd], 
        A.~Rosato\address[sconcpd]{Dept. of Oncological and Surgical Sc., Univ. of Padova, Via Gattamelata 64, I-35128 Padova}, 
        A.~Sgura\addressmark[biorm3]\addressmark[infnrm3],
        C.~Tanzarella\addressmark[biorm3]\addressmark[infnrm3],
        N. Uzunov\addressmark[lnl]\address[shumen]{Dept. of Natural Sciences, ``K. Preslavsky'' Univ. of Shumen, Bulgaria}
        and         
        M. Zuffa\addressmark[infnbo]
        } 
       
\begin{document}

\begin{abstract}
$^{188}$Re is a $\beta^-$ (Emax = 2.12 MeV) and $\gamma$ (155 keV) emitter. 
Since its 
chemistry is similar to that of the largely employed tracer, $^{99m}$Tc, 
 molecules of hyaluronic acid  (HA) have been labelled with $^{188}$Re
%rhenium-188 
to produce a target specific radiopharmaceutical.
The radiolabeled compound, i.v. injected in healthy mice, is able to 
accumulate into the liver after a few minutes.
%it can be linked to molecules of 
%hyaluronic acid (HA), which carry it around in the body to specific sites, 
%e.g. to the liver. 
To study the effect of metabolic radiotherapy in mice, 
we have built a small gamma camera based on a matrix of YAP:Ce crystals, 
with 0.6$\times$0.6$\times$10 mm$^3$ pixels, read out by a R2486 Hamamatsu PSPMT. A 
high-sensitivity 20 mm 
thick lead parallel-hole collimator, with hole diameter 1.5 mm and septa 
of 0.18 mm, is placed in front of the YAP matrix. 
%%The detector is triggered using the last dynode and the photon impact is 
%%reconstructed by charge division reading x1, x2, y1, y2 lines. 
Preliminary results obtained with 
various phantoms containing a solution of $^{188}$Re and with C57 black mice 
injected with the $^{188}$Re-HA solution are presented. 
To increase the space resolution and to obtain two orthogonal projections 
simultaneously we are building in parallel two new 
cameras to be positioned at 90 degrees. They use a CsI(Tl) matrix with 
1$\times$1$\times$5 mm$^3$ pixels read out by H8500 Hamamatsu Flat panel PMT. 
%%Parallel-hole collimators 20 mm thick, with 1 mm diameter hexagonal holes 
%%and 0.18 mm thick septa, are mounted in front of the scintillators. 
%%The front-end electronics has been designed using MPX-08 chips.
\vspace{1pc}
\end{abstract}

% typeset front matter (including abstract)
\maketitle

\section{INTRODUCTION}

$^{188}$Re is an attractive therapeutic radioisotope with broad clinical 
applications. Oncology applications range from palliation of metastatic 
bone pain to bone marrow ablation 
%%% needed in case of generalized lymphoproliferative disorder (gld) ?
%%% or in case of cancer that has spread from the original (primary) tumor to the bone marrow ?
and in general to the use of $^{188}$Re labelled therapeutic agents to 
target specific cancerous tissues (see for instance reference \cite{iaea}).
Other therapeutic applications comprise the inihibition of restenosis 
after Percutanueous Transluminal Coronary Angioplasty (PTCA), 
%%% also called coronary artery radiation therapy - german clinicians first demonstrated the promise of intravascular irradiation in the early 1990s using gamma radiation to prevent restenosis in leg arteries
radiation synovectomy,
%%%surgery for rheumatoid arthritis pain 
and intravasal brachytherapy. 
%%%Brachytherapy is a minimally invasive procedure that implants small radioactive pellets (called seeds) that are about the size of a grain of rice into the prostate where they irradiate the cancer from inside the gland. 
In the field of metabolic radiotherapy  
%%%NOT QUITE, this is referred to using monoclonal antibodies
%%%or radioimmunotherapy 
$^{188}$Re shows several 
favourable characteristics. It can be produced carrier free using a 
W-Re generator (see for instance reference \cite{ornl}) and its chemistry 
is similar to that of $^{99m}$Tc which is the most used radioisotope in 
nuclear medicine (medical imaging). 
The $^{188}$W parent has a 69 d half-life, which permits to use 
the generator for a relatively long period, the equilibrium between 
parent and daughter setting up within about two days. 
$^{188}$Re decays to $^{188}$Os$^*$ in about 0.7 
days via the emission of a $\beta$-ray with a maximum energy of 2.12 MeV 
(0.78 MeV average energy), 
which can be used for destroying cancerous cells. In addition $^{188}$Os$^*$
emits promptly (0.69 ns) a 155 keV $\gamma$-ray (15\%), which can be used for 
imaging. Given the chemical similarity with $^{99m}$Tc, it can be linked 
to molecules of hyaluronic acid (HA) which have the function of carrying 
it to specific sites in the body, e.g. with the production of an 
accumulation and retention of the drug in the liver \cite{sirr}. 
Hence the potential interest for treating liver cancers. 
On the other hand the $\beta$ radiation could interfere with the labelling 
process and destroy the molecule used to carry the radioisotope in the body 
to the target organ, thus reducing the therapeutic effect. Two additional 
points have to do with the 
relatively long lifetime and with the rich photon spectrum of $^{188}$Re, 
which extends to high energy, compared to the single 140 keV photon emitted 
by $^{99m}$Tc with a half-life of about 6 h. Taking into account the 
branching ratios (BR) and the lifetimes, the relative $^{188}$Re/$^{99m}$Tc 
counting rate, for an equal number of $\mu$-moles, is about 9\%. This 
implies that photon detectors developed for imaging with $^{99m}$Tc are 
not necessarily sensitive enough. The usual thickness of a 
low-energy Pb collimator, 
say 20 mm, will be almost transparent to $^{188}$Re photon lines at 300 keV or 
higher energies, even with BRs depressed by a factor of ten or more, 
producing background counts which blur the image and worsen the spatial 
resolution. To study the effect of metabolic radiotherapy in mice, we have 
therefore built a new small high-sensitivity $\gamma$-camera, following the 
experience with the YAP-camera \cite{yap}\cite{yap1}\cite{yap2}, which is used routinely to 
image small animals (mice) 
with  $^{99m}$Tc-HA at the Laboratori Nazionali di Legnaro, Italy (e.g. \cite{habut}\cite{99mtc}). 
  
\section{THE GAMMA CAMERA}

The gamma camera is based on a matrix of yttrium aluminium perovskite doped 
with cerium (YAP:Ce or YAlO$_3$:Ce) crystals \cite{preciosa}, with 
friendly mechanical properties (no igroscopicity), fast response ($\sim$25 ns 
decay time),   
high density (5.37 g/cm$^3$) and good X- and $\gamma$-ray absorption. 
There are 66$\times$66 pixels, each 0.6$\times$0.6$\times$10 mm$^3$, covering a field-of-view 
(FOV) of 
40$\times$40 mm$^2$. The pixels are covered laterally by a special 5 $\mu$m thick 
reflective coating which provides also the optical separation between 
neighboring elements. The scintillator is read out by a R2486 Hamamatsu 
PositionSensitivePMT \cite{hamamatsu} with a 76 mm diameter photocathode.
The anode consists of 16 plus 16 wires crossing at 90$^o$ and connected by 
two resistive chains, defining the $x$ and $y$ directions. The wires define 
an active area with a diameter of about 50 mm.   
A 20 mm thick lead parallel hexagonal-hole collimator \cite{nuclfields}, 
with hole diameter 1.5 mm and septa of 0.18 mm, is placed in front of the 
YAP matrix. The detector is triggered 
using the last dynode and the ends of the $x$ and $y$ resistive chains 
(x$_1$, x$_2$, y$_1$, y$_2$) are amplified, stretched and read out 
by a PC using 
a PCI 6023E card \cite{national}. The coordinates of the photon impact 
point are then reconstructed by charge division, 

\begin{equation}
x = {\rm {(x_1 - x_2)}}/{\rm {(x_1 + x_2)}}
\end{equation}
 
\noindent and similarly for $y$. 

\section{CALIBRATIONS}

The energy response of the detector to a spatially uniform source (flat 
field) of $^{99m}$Tc 140 keV photons prior to energy equalization has 
been determined using a solution containing $^{99m}$Tc which covered the 
whole FOV and was located a few centimeters in front of the collimator 
surface. The $xy$ has been arbitrarily divided in pixels and the 
average energy computed in each pixel.  The corrections to the measured 
energy extracted from this 
calibration are shown in Fig.~\ref{fig:flat} and have been used in the 
following. As shown below with the $^{188}$Re spectrum, these 
corrections improve the energy resolution of the detector. Apart from 
the energy equalization, no other correction has been applied. 
With $^{99m}$Tc the sensitivity of the gamma camera is found to be 
$\sim$2$\times$10$^{-4}$ or $\sim$7$\times$10$^3$ cps/mCi, which 
agrees roughly with calculations.

\begin{figure}[htb]
\vspace{9pt}
%\framebox[55mm]{\rule[-21mm]{0mm}{43mm}}
%\includegraphics[width=2.7 in]{flatfield.eps}
\includegraphics[width=6.9 truecm]{fig/FlatFieldCorr-n.eps}
\vspace{-1.5pc}
\caption{Flat field calibration with $^{99m}$Tc.} 
\label{fig:flat}
\vspace{-1pc}
\end{figure}

Pointlike $^{241}$Am (60 keV photons), $^{57}$Co ($\sim$122 keV photons) 
and $^{137}$Cs (660 keV) sources located 
in different positions a few millimeters distant from the collimator 
have been used  
both to simulate the $^{188}$Re energy spectrum and to evaluate 
the spatial resolution of the detector. In addition $^{241}$Am and $^{57}$Co, 
together with $^{99m}$Tc photons, permit the calibration of energy 
scale. 
%%%NOT AT ALL
%%%The data with the different sources 
%%%have been collected in different runs and merged in software.  
The overall energy spectrum is 
presented in Fig.~\ref{fig:acc-en} and the cumulative image of the sources is 
visible in 
Fig.~\ref{fig:acc-im}. The 60 keV is well prominent and a 122 keV shoulder 
is also visible; $^{137}$Cs instead produces a broad shoulder at about 
half of the photon energy.  
%%%Even with the merged runs, u
Using appropriate energy cuts the three images 
can be separated. 
%%%A preliminary value for the spatial resolution at 
%%%122 keV is $\Delta$$x$ $\sim$ 3 mm FWHM. Note however that in 
%%%Fig.~\ref{fig:acc-im} the $^{57}$Co source is seen to shine through 
%%%several adiacent collimator holes and that the shadow of the septa is 
%%%visible, which would imply in practice a somewhat worse spatial resolution. 
The intrinsic spatial resolution of the system is quite good, since 
individual collimator holes can be clearly seen in Fig.~\ref{fig:acc-im}. The 
resolution however is worsened in practice by the small thickness of the septa 
relative to the hole diameter of the present collimators, making them 
partially transparent to radiation, so the actual effective  
resolution is $\Delta$$x$ $\sim$ 3 mm FWHM at 122 keV.

\begin{figure}[htb]
\vspace{9pt}
%\includegraphics[width=2.7 in]{amcocs-en.eps}
\includegraphics[width=6.9 truecm]{fig/AmCoCsSpectrum-n.eps}
\vspace{-1.5pc}
\caption{$^{241}$Am, $^{57}$Co and $^{137}$Cs superimposed spectra measured with the YAP camera.}
\label{fig:acc-en}
\vspace{-1pc}
\end{figure}

\begin{figure}[htb]
\vspace{9pt}
%\includegraphics[width=2.7 in]{amcocs-im.eps}
\includegraphics[width=6.9 truecm]{fig/AmCoCsImage-n.eps}
\vspace{-1.5pc}
\caption{$^{241}$Am (center), $^{57}$Co (top) and $^{137}$Cs (bottom) images measured with the YAP camera.}
\label{fig:acc-im}
\vspace{-1pc}
\end{figure}

%- Distributed $^{99m}$Tc and $^{188}$Re sources

The $^{188}$Re photon spectrum measured with a Ge detector is shown in
Fig.~\ref{fig:re-ge}. The 155 keV line is prominent, but many more lines 
are present at higher energy, in some cases, e.g. at $\sim$300 keV, with 
BRs only a factor of ten lower, or at 800-1200 keV with intensities 
lower only by a factor of 100 \cite{nndc}. 

\begin{figure}[htb]
\vspace{9pt}
%\includegraphics[width=2.7 in]{re-ge.eps}
\includegraphics[width=8.2 truecm]{fig/Re188Spectrum-Ge-n.eps}
\vspace{-2pc}
\caption{$^{188}$Re spectrum measured with a Ge detector.}
\label{fig:re-ge}
\vspace{-1pc}
\end{figure}

The $^{188}$Re spectrum measured with the YAP camera 
during the imaging of a C57 mouse (see next section) 
%%%NOT AT ALL
%%%produced by a spatially uniform solution located at a 
%%%few centimeters distance from the collimator 
%%%and measured with the YAP camera 
is shown in Fig.~\ref{fig:re-yap}. The spectrum is shown before and after 
applying the corrections for energy non-uniformity, and a clear improvement 
is observed with the shrinking of the 155 keV peak. After the corrections,
the energy resolution is $\Delta$E/E $\sim$ 33\% $@$ 155 keV. 

\begin{figure}[htb]
\vspace{9pt}
%\includegraphics[width=2.7 in]{re-yap.eps}
\includegraphics[width=6.9 truecm]{fig/Re188Spectrum-YAP-n.eps}
\vspace{-1.5pc}
\caption{$^{188}$Re spectrum measured with the YAP camera: the shaded spectrum has been corrected for energy non-uniformity.}
\label{fig:re-yap}
\vspace{-1pc}
\end{figure}

%%%- Energy and spatial resolution ($\Delta$$x$ $\sim$ 3 mm FWHM $@$ 122 keV, 
%%%$\Delta$E/E $\sim$ 33\% $@$ 155 keV)    

\section{FIRST MEASUREMENTS WITH $^{188}$Re}

%%%- Verification of the chemical stability of the $^{188}$Re-HA molecule 
%%%(stability of the radioisotope labelling)
%The chemical stability of the $^{188}$Re-HA molecule has been verified after 
%the labelling process. 
The labelling reaction of HA using $^{188}$Re
%rhenium-188 
was carried out with good 
yields (65-70\%). 
The radiolabelled compound was purified with a size exclusion
chromatographic method before being used for biodistribution studies. 
Stability studies in rat serum confirmed the maintaining  of the Re linked 
to the polymer and there was no evidence of radio-decomposition after a few 
hours. 
%The labelling/milking (?) efficiency is $\sim$70\% (?) 
%and there is no evidence of a decrease within a few hours. 

The radiotoxicity of $^{188}$Re has been tested ``in vitro''  and compared 
with $^{99m}$Tc, with which no effect is expected.  Cells of the 
M5076 tumor line have been treated with $^{188}$Re and  $^{99m}$Tc solutions,
and irradiated with X-rays. The number of binucleate cells and of micronuclei 
in the cells is then counted. 
M5076 cells turn to out to be highly sensitive to X-rays (0.25-2 
Gy)\cite{sirr}. Activities of 150-300 $\mu$Ci of $^{99m}$Tc show no effect, 
but $^{188}$Re $\beta$-rays, with similar initial activities integrated 
during 72 h, seem to be quite efficient in inducing DNA damage\cite{sif}. 

To test the full chain, from the radiolabelling to to the imaging ``in vivo'',
a C57 black mouse (healthy, female) has been injected with  $^{188}$Re-HA.
After general anesthesia, the solution with an activity of about 
250 $\mu$Ci was injected in the caudal vein.
The mouse was positioned along the diagonal of the FOV, with the locus of 
injection outside it, and was monitored for about three hours.
The  image collected in the first five minutes shows a large spot close to 
the locus of injection in the tail (Fig.~\ref{fig:c57a}). After 5 mins the 
activity concentrates roughly in the centre of the body, in a volume which 
contains the liver (Fig.~\ref{fig:c57b}). The activity is slowly 
decreasing during the 3 h of the measurement. After 3 h the mouse was 
sacrificed, and the organs were extracted and measured with a microcurimeter
(Fig.~\ref{fig:att}). The liver contains 60\% of the residual activity 
and close by organs another 20\%, in agreement with the scintigrafic 
image (Fig.~\ref{fig:c57b}), where individual organs are not 
resolved. Even with limited resolution the test shows that it is 
possible to monitor the biodistribution of $^{188}$Re in mice, with a 
potential saving in the number of animals needed for testing the 
$^{188}$Re therapy. 

\begin{figure}[htb]
\vspace{9pt}
%\includegraphics[width=2.7 in]{c57-a.eps}
\includegraphics[width=6.9 truecm]{fig/MouseTailImage-n.eps}
\vspace{-1.5pc}
\caption{The image of the C57 mouse integrated for the first 5 minutes after the injection of $^{188}$Re-HA in the caudal vein.}
\label{fig:c57a}
\vspace{-1pc}
\end{figure}

\begin{figure}[htb]
\vspace{9pt}
%\includegraphics[width=2.7 in]{c57-b.eps}
\includegraphics[width=6.9 truecm]{fig/MouseBodyImage-n.eps}
\vspace{-1.5pc}
\caption{The image of the C57 mouse integrated between 5 and 185 minutes after the injection of $^{188}$Re-HA in the caudal vein. The volume of large activity corresponds to the liver.}
\label{fig:c57b}
\vspace{-1pc}
\end{figure}

%%%- Measurement of the activity of the mouse's organs ``$post$ $mortem$''
%%%(Fig.~\ref{fig:att})

%%%\texttt{sidewaysfigure}
%%%\texttt{rotating}
\begin{figure}[htb]
%\begin{sidewaysfigure}[htb]
\vspace{9pt}
%\includegraphics[width=2.7 in]{activity-r.ps}
%\includegraphics[width=2.7 in]{AttivOrgani.eps}
\includegraphics[width=6.9 truecm]{fig/AttivOrganiEng.eps}
%\includegraphics[width=2.7 in]{activity.eps}
%\includegraphics[width=2.5 in]{activity.eps}
\vspace{-1.5pc}
\caption{Activity of various organs ``$post$ $mortem$''.}
\label{fig:att}
\vspace{-1pc}
\end{figure}
%\end{sidewaysfigure}

\section{CONCLUSIONS}

Preliminary results obtained using a new YAP camera in imaging 
$^{188}$Re sources
%with various phantoms containing a solution of $^{188}$Re and 
and C57 black mice 
injected with a $^{188}$Re-HA solution have been presented. 
To increase the space resolution without 
losing sensitivity, and to obtain different projections simultaneously, 
we are building two new 
cameras to be positioned at 90 degrees around the animal. 
They use a CsI(Tl) matrix with 1$\times$1$\times$5 
mm$^3$ pixels read out by H8500 Hamamatsu Flat panel PMT \cite{hamamatsu}. 
Parallel-hole Pb 
collimators 20 mm thick, with 1 mm diameter hexagonal holes and 0.2 mm 
thick septa, will be mounted in front of the scintillators. 
Also specially made collimators with thicker septa and/or different 
absorber material will be used. The front-end 
electronics for the 64 channels of the H8500 has been designed using 
MPX-08 chips \cite{nova}. The system will be mounted on a rotating support 
in order to produce tomographic images. 

\begin{thebibliography}{9}

\bibitem{iaea} Labelling techniques of biomolecules for targeted radiotherapy, IAEA-TECDOC-1359, Vienna July 2003  
\bibitem{ornl} {\tt http://www.ornl.gov/sci/nuclear\_
science\_tecnology/nu\_med/188info.htm}
\bibitem{sirr} A. Antoccia et al., Dati preliminari e danno al DNA del $^{99m}$Tc-HA in sistemi ``in vitro'' ed ``in vivo'', Suppl. Boll. SIRR VII (2004) 43 
\bibitem{yap} F. de Notaristefani et al., YAP Camera: a small field camera with sub-millimiter spatial resolution, Eur. J. Nucl. Med. 22 (1995) 337
\bibitem{yap1} F. de Notaristefani et al., First Results from a YAP:Ce Gamma Camera for Small Animal Studies, IEEE Trans. Nucl. Sci. 43 (1996) 3264 
\bibitem{yap2} F. de Notaristefani, F. Vittori and T. Malatesta, Development of YAP:Ce multi-crystal detectors, Physica Medica 13 (1997) 237 
\bibitem{habut} R. Rossin et al., In vivo Biodistribution Studies on Hyaluronan Butyrate by Means of 99mTc Direct Labelling and YAP Camera, In: Technetium, Rhenium and Other Metals in Chemistry and Nuclear Medicine (M. Nicolini, U. Mazzi Eds.), pp 689-693, SGEditoriali, Padova, 2002.  
%ABSTRACT
%The glycosaminoglican hyaluronan is one of the main components of the extracellular matrix. The primary receptor for HA (CD44) is
%overexpressed on the surface of most malignant tumour cells, suggesting the use of HA for the targeted delivery of antitumour drugs
%such as butyrate. In this study the potential anti-tumour prodrug HA-But, directly labelled with 99mTc, has been injected in mice
%intravenous, intraperitoneum and subcutaneous, and its biodistribution has been studied by means of a YAP camera. The collected
%scintigrafic images showed a rapid blood clearance and liver uptake after i.v. injection and a slow diffusion after i.p. and s.c. injection.
%These results confirm for HA-But the biodistribution of native HA and suggest its use for local therapy of solid tumours.
\bibitem{99mtc} M.C. Giron et al., YAP-Camera Device for Biodistribution Studies in Mice of 99mTc-Radiotracers, Poster at the 6th Int. Symp. on Technetium in Chemistry and Nuclear Medicine, Brixen, Italy, 2002 \\
{\tt http://tc2002.unipd.it/posters\_main.htm} 
\bibitem{preciosa} CRYTUR Preciosa a.s., Palackeho 175, 511 19 Turnov, Czech Republic. 
\bibitem{hamamatsu} {\tt http://www.hamamatsu.com/} 
\bibitem{nuclfields} {\tt http://www.nuclearfields.com/}  
\bibitem{national} {\tt http://www.ni.com/} 
\bibitem{nndc} {\tt http://www.nndc.bnl.gov/nudat2/\\
index.jsp}
\bibitem{sif} A. Antoccia et al., Study of metabolic radiotherapy with $^{188}$Re via small animal imaging, presented at the annual meeting of the Italian Physical society, Brescia 20-25 Settembre 2004 {\tt http://www.sif.it} 
\bibitem{nova} {\tt http://www.novarad.com/}
\end{thebibliography}

\end{document}


physics0506008.extracted_bib
\begin{thebibliography}{9}

\bibitem{iaea} Labelling techniques of biomolecules for targeted radiotherapy, IAEA-TECDOC-1359, Vienna July 2003  
\bibitem{ornl} {\tt http://www.ornl.gov/sci/nuclear\_
science\_tecnology/nu\_med/188info.htm}
\bibitem{sirr} A. Antoccia et al., Dati preliminari e danno al DNA del $^{99m}$Tc-HA in sistemi ``in vitro'' ed ``in vivo'', Suppl. Boll. SIRR VII (2004) 43 
\bibitem{yap} F. de Notaristefani et al., YAP Camera: a small field camera with sub-millimiter spatial resolution, Eur. J. Nucl. Med. 22 (1995) 337
\bibitem{yap1} F. de Notaristefani et al., First Results from a YAP:Ce Gamma Camera for Small Animal Studies, IEEE Trans. Nucl. Sci. 43 (1996) 3264 
\bibitem{yap2} F. de Notaristefani, F. Vittori and T. Malatesta, Development of YAP:Ce multi-crystal detectors, Physica Medica 13 (1997) 237 
\bibitem{habut} R. Rossin et al., In vivo Biodistribution Studies on Hyaluronan Butyrate by Means of 99mTc Direct Labelling and YAP Camera, In: Technetium, Rhenium and Other Metals in Chemistry and Nuclear Medicine (M. Nicolini, U. Mazzi Eds.), pp 689-693, SGEditoriali, Padova, 2002.  
%ABSTRACT
%The glycosaminoglican hyaluronan is one of the main components of the extracellular matrix. The primary receptor for HA (CD44) is
%overexpressed on the surface of most malignant tumour cells, suggesting the use of HA for the targeted delivery of antitumour drugs
%such as butyrate. In this study the potential anti-tumour prodrug HA-But, directly labelled with 99mTc, has been injected in mice
%intravenous, intraperitoneum and subcutaneous, and its biodistribution has been studied by means of a YAP camera. The collected
%scintigrafic images showed a rapid blood clearance and liver uptake after i.v. injection and a slow diffusion after i.p. and s.c. injection.
%These results confirm for HA-But the biodistribution of native HA and suggest its use for local therapy of solid tumours.
\bibitem{99mtc} M.C. Giron et al., YAP-Camera Device for Biodistribution Studies in Mice of 99mTc-Radiotracers, Poster at the 6th Int. Symp. on Technetium in Chemistry and Nuclear Medicine, Brixen, Italy, 2002 \\
{\tt http://tc2002.unipd.it/posters\_main.htm} 
\bibitem{preciosa} CRYTUR Preciosa a.s., Palackeho 175, 511 19 Turnov, Czech Republic. 
\bibitem{hamamatsu} {\tt http://www.hamamatsu.com/} 
\bibitem{nuclfields} {\tt http://www.nuclearfields.com/}  
\bibitem{national} {\tt http://www.ni.com/} 
\bibitem{nndc} {\tt http://www.nndc.bnl.gov/nudat2/\\
index.jsp}
\bibitem{sif} A. Antoccia et al., Study of metabolic radiotherapy with $^{188}$Re via small animal imaging, presented at the annual meeting of the Italian Physical society, Brescia 20-25 Settembre 2004 {\tt http://www.sif.it} 
\bibitem{nova} {\tt http://www.novarad.com/}
\end{thebibliography}