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In the present work, an educational experiment is presented for the estimation of the focal lengths of the individual lenses that compose a two-lens system. The method is based on the measurement of the back focal length and the equivalent focal length of the two-lens system. The experimental setup is simple, two convex lenses of equal focal lengths are positioned at a distance d and by measuring the back focal length of the two-lens system the unknown focal lengths are derived. In addition, the image size observed by the two-lens system is compared to that of different single test lenses in order to derive the equivalent focal length. The experimental methodology is straightforward and provides all the important information that can be obtained for a two-lens system in a geometrical optics laboratory, without expensive equipment. [ABSTRACT FROM AUTHOR]

A study of two-lens system is presented using the Newton's lens formula. Two convex lenses of equal focal length are positioned in variable distances d and their principal focal length is calculated using the Newton's method. Initially, the equivalent optical power of the two-lens system is derived. This optical power is then plotted as a function of the distance d. The related graph provides the information for the optical power of each lens. Eventually, the focal length of one convex lens is depicted. This method can be applied in Physics Laboratories (Geometrical Optics) for undergraduate students that want to study the behavior of a two-lens system. [ABSTRACT FROM AUTHOR]

The aim of this study is to examine the impact of dark signal on assessing the image quality in computerized mammography. A GE analogue mammography unit was calibrated to be used with an Agfa CR35-X system. Tests for quality control were performed and Image Plates (IPs) were erased by the CR system. All IPs were first exposed to known amounts of scatter radiation and then used to take mammographic images of phantoms with varying density (a PASMAM-1054 Phantom with PMMA and Al inserts). Since high Signal-to-noise ratio (SNR) and high Contrast-to-noise ratio (CNR) are of great importance in mammographic image quality, we measured SNR and CNR of the taken images. Our results show the effect of scatter radiation on SNR and CNR. Scatter radiation increases SNR and decreases CNR. The impact of background signal was found not to be negligible. Dark signal deteriorates image quality in CR mammography. Consequently, further investigation may be warranted and daily erasure of the IPs is recommended in order to limit dark signal effect on image quality. [ABSTRACT FROM AUTHOR]

This study presents an attempt to compare individualised palliative treatment absorbed doses, by planar images data and Monte Carlo simulation, in two in vivo treatment cases, one of bone metastases and the other of liver lesions. Medical Internal Radiation Dose schema was employed to estimate the absorbed doses. Radiopharmaceutical volume distributions and absorbed doses in the lesions as well as in critical organs were also calculated by Monte Carlo simulation. Individualised planar data calculations remain the method of choice in internal dosimetry in nuclear medicine, but with the disadvantage of attenuation and scatter corrections lack and organ overlay. The overall error is about 7 % for planar data calculations compared with that using Monte Carlo simulation. Patient-specific three-dimensional dosimetric calculations using single-photon emission computed tomography with a parallel computed tomography study is proposed as an accurate internal dosimetry with the additional use of dose–volume histograms, which express dose distributions in cases with obvious inhomogeneity. [ABSTRACT FROM PUBLISHER]

Abstract: The aim of this study was to calculate the absorbed dose of 22 patients that were diagnosed for neuroendocrine tumours in liver and had received therapeutic dose of 111In octreotide. In-111 Octreotide infusion, via intrahepatic catheterization is well established technique in our Institution in hepatocellular carcinoma and neuroendocrine tumours treatments. The patient specific dosimetry calculations, for this way of treatment, were based on anterior and posterior scintigraphy images that were acquired immediately after radiopharmaceutical infusion, through hepatic arterial port and at 24 and 48 h post-infusion. Gamma – camera was calibrated in order to estimate source organ activity considering count rate, patient’s body diameter and source organ size. The results showed that the tumour absorbed dose ranged from 2.5 to 18.4 mGy/MBq, depending on the lesion size. Patient specific dosimetry calculations helps the physician to optimize the planning of the treatment, avoid side effects to healthy tissue and assign administered dose to treatment results. [ABSTRACT FROM AUTHOR]