Abstract
The main objective of the present study was to upgrade a clinical gamma camera to obtain high resolution tomographic images of small animal organs. The system is based on a clinical gamma camera to which we have adapted a special-purpose pinhole collimator and a device for positioning and rotating the target based on a computer-controlled step motor. We developed a software tool to reconstruct the target's three-dimensional distribution of emission from a set of planar projections, based on the maximum likelihood algorithm. We present details on the hardware and software implementation. We imaged phantoms and heart and kidneys of rats. When using pinhole collimators, the spatial resolution and sensitivity of the imaging system depend on parameters such as the detector-to-collimator and detector-to-target distances and pinhole diameter. In this study, we reached an object voxel size of 0.6 mm and spatial resolution better than 2.4 and 1.7 mm full width at half maximum when 1.5- and 1.0-mm diameter pinholes were used, respectively. Appropriate sensitivity to study the target of interest was attained in both cases. Additionally, we show that as few as 12 projections are sufficient to attain good quality reconstructions, a result that implies a significant reduction of acquisition time and opens the possibility for radiotracer dynamic studies. In conclusion, a high resolution single photon emission computed tomography (SPECT) system was developed using a commercial clinical gamma camera, allowing the acquisition of detailed volumetric images of small animal organs. This type of system has important implications for research areas such as Cardiology, Neurology or Oncology.
Highlights
In the last decades, and mainly since the development of knockout animals, small animals have become important tools in preclinical research, as models of the most different human diseases [1]
There is no evidence of the star pattern associated with point-like sources, when the filtered back projection (FBP) algorithm is used for reconstruction
We determined the spatial resolution as the full width at half maximum (FWHM) of the point-like pattern in Figure 3, by adding the central 10 planes and fitting a two-dimensional Gaussian function
Summary
Mainly since the development of knockout animals, small animals have become important tools in preclinical research, as models of the most different human diseases [1]. In order to assess the effect of the experimental protocol, many procedures are based on the sacrifice of the animal to remove and process the organ or tissue of interest. On the other hand, imaging techniques allow in vivo sequential evaluation of functional and structural organ changes caused by the pathologic process or experimental protocol. On this basis, the same animal can be studied several times along the experiment and can be used as its own control. In vivo imaging techniques are useful to reduce the duration of the experiment, diminishing costs and reducing ethical problems.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
