Search

The capability of the scintimammography to diagnose subcentimeters sized tumors was increased by the employment of a dedicated gamma camera. The introduction of small field of view camera, based on pixellated scintillation array and position sensitive photomultiplier, allowed to enhance the geometric spatial resolution and contrast of the images due to reduced collimator-tumor distance. The aim of this paper is to investigate the realistic possibility of T1a tumors detection (~5 mm size) by comparing the signal-to-noise ratio (SNR) values obtained by different imagers. To this end, we have utilized a self-designed solid breast phantom with different sized hot spots (tumors). The phantom consists of seven disks with different thickness, molded from resin epoxy activated with [Co.sup.57] isotope. The overlapped disks represent a pendula breast with about 800 cc volume. Hot spots have not wall. One disk has holes to fit the hot spots representing the different sized lesions. The imagers utilized were: a standard Anger Camera and three different cameras based on scintillator array, CsI(TI) or NaI(TI), coupled to position sensitive photomultiplier with different technologies, to make detectors with field of view of 3 and 5 inch. The experimental results are supported by Monte Carlo simulation. It was highlighted how spatial resolution is a predominant element in tumor visibility and how background causes a reduction of the image contrast. All gamma cameras show close results at SNR values less than 10 and a full detectability of 8 mm tumor size. However, the results show the 5 mm tumor size is lower detection limit for all cameras. Index Terms--Biomedical nuclear imaging, photomultipliers, scintilation detectors.

We have developed a TDC+Transputer-based acquisition system to study the X-ray imaging capabilities of a silicon [micro]strip detector with 100 and 200 [[micro]meter] read-out pitch. This system allows real-time image acquisition and display. We present images obtained with an X-ray mammography tube using sub-millimeter high contrast test objects on a 16*16 channels prototype.

Double-sided microstrip silicon crystals are being tested as detectors for X-rays in the diagnostic energy range (10-100 keV) for digital radiography. We have developed an ADC&CAMAC-based acquisition system to study the imaging capabilities of a silicon |micro~strip detector with 100 and 200 ||micro~meter~ read-out pitch. We present the first images of submillimeter high contrast phantoms obtained with an X-ray mammography tube operating at high flux density.

We are investigating the use of a double side |micro~-strip silicon crystal for X-ray detection. The detector is 300 ||micro~meter~ thick and the read-out pitch is 100 ||micro~meter~ for both sides. It operates in capacitive charge division mode by means of floating strips between read-out strips. The detector has been irradiated by 241Am and 109Cd sources. Different zones within the 100 ||micro~meter~ read-out pitch have been individually exposed. Thus, the following characteristics have been studied as a function of the impact point of the photon: (a) the charge collection mechanism; (b) the relative detection efficiency; (c) the energy resolution; (d) the spatial resolution. The absolute efficiency of the detector has also been measured at three energy values.