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This work evaluates the entrance skin dose (ESD), the body organ dose (BOD) and the effective dose (E) for chest X-ray exposures of paediatric patients. Two Moroccan university hospitals in Rabat, composed of two departments, and one in Casablanca with one paediatric compartment has been considered. For reasons of confidentiality, the departments are named A, B and C. Patients were divided into four age groups: 0-1, 1-5, 5-10 and 10-15 y, so that the results could be compared with previous published data found in the literature. The results have been calculated with the use of the Dose Cal software. Results of mean ESD for the age interval 1-5 y and antero-posterior (AP) projection are: 162 µGy for hospital A, 91 µGy for hospital B and 105 µGy for hospital C. The diagnostic reference levels (DRLs) of 100 µGy for this age range is exceeded in hospital A, while in the other two hospitals results were within the DRL and comparable with the results found in Brazil, Soudan, Nigeria and other radiological centres inpean Countries. The results of BOD and E showed that for the three departments, the BOD varies in the same proportion as the ESD. The highest values are those of hospital A. For the PA examination, the dose is reduced compared with the AP projection, especially for sensitive organs.

For the head-and-neck cancer bilateral irradiation, intensity-modulated radiation therapy (IMRT) is the most reported technique as it enables both target dose coverage and organ-at-risk (OAR) sparing. However, during the last 20 years, three-dimensional conformal radiotherapy (3DCRT) techniques have been introduced, which are tailored to improve the classic shrinking field technique, as regards both planning target volume (PTV) dose conformality and sparing of OAR’s, such as parotid glands and spinal cord. In this study, we tested experimentally in a sample of 13 patients, four of these advanced 3DCRT techniques, all using photon beams only and a unique isocentre, namely Bellinzona, Forward-Planned Multisegments (FPMS), ConPas, and field-in-field (FIF) techniques. Statistical analysis of the main dosimetric parameters of PTV and OAR’s DVH’s as well as of homogeneity and conformity indexes was carried out in order to compare the performance of each technique. The results show that the PTV dose coverage is adequate for all the techniques, with the FPMS techniques providing the highest value for D95%; on the other hand, the best sparing of parotid glands is achieved using the FIF and ConPas techniques, with a mean dose of 26 Gy to parotid glands for a PTV prescription dose of 54 Gy. After taking into account both PTV coverage and parotid sparing, the best global performance was achieved by the FIF technique with results comparable to that of IMRT plans. This technique can be proposed as a valid alternative when IMRT equipment is not available or patient is not suitable for IMRT treatment.

Purpose: In yttrium-90 (Y-90) single-photon emission computed tomography (SPECT) imaging, the choice of the acquisition energy window is not trivial, due to the continuous and broad energy distribution of the bremsstrahlung photons. In this work, we investigate the effects of the energy windows on the image contrast to noise ratio (CNR), in order to select the optimal energy window for Y-90 imaging. Materials and Methods: We used the Monte Carlo SIMIND code to simulate the Jaszczak phantom which consists of the six hot spheres filled with Y-90 and ranging from 9.5 to 31.8 mm in diameter. Siemens Symbia gamma camera fitted with a high-energy collimator was simulated. To evaluate the effect of the energy windows on the image contrast, five narrow and large energy windows were assessed. Results: The optimal energy window obtained for Y-90 bremsstrahlung SPECT imaging was 120–150 keV. Furthermore, the results obtained for CNR indicate that the high detection is only for the three large spheres. Conclusion: The optimization of energy window in Y-90 bremsstrahlung has the potential to improve the image quality.

Introduction: The choice of the radionuclide has a key role in nuclear medicine which appearing the lowest scatter fraction. In addition, the presence of penetrated and scattered photons from collimator in single-photon emission computed tomography images degrades resolution and contrast. Thus, image quality depends on sensitivity and resolution of the collimator–detector system. The goal of this study was to compare the image quality that can be achieved by three radionuclides: technetium-99 m (Tc-99 m), iodine-123 (I-123), and samarium-153 (Sm-153). Materials and Methods: Tc-99 m and Sm-153 were imaged with low-energy high resolution (LEHR) collimator, while I-123 was imaged with medium-energy (ME) collimator. We modeled the Siemens Symbia Medical system using Monte Carlo simulation code SIMIND. The imaging characteristics of each radionuclide were investigated by simulated data: point spread function, sensitivity (Cps/MBq) and geometric, penetration and scattering distribution. Results: Tc-99 m and Sm-153 give best and results with LEHR collimator for spatial resolution (full width at half maximum [FWHM] = 3.19 mm; full width at tenth maximum [FWTM] = 6.73 mm) and (FWHM = 3.22 mm; FWTM = 7.39 mm), respectively. Whereas, I-123 provided with ME collimator a lower resolution (FWHM = 4.89 mm; FWTM = 9.89 mm). The sensitivity recorded by Tc-99 m, Sm-153, and I-153 were (31.21 Cps/MBq), (10.16 Cps/MBq), and (51.22 Cps/MBq), respectively. Conclusion: Tc-99 m and Sm-153 give the best and generally similar imaging properties with LEHR. For I-123, the ME collimator helps lowering the influence of high-energy gamma rays.

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Purpose: In single-photon emission computed tomography imaging, the presence of scatter degrades image quality. The goal of this study is to optimize the main- and sub-energy windows for triple-energy window (TEW) method using Monte Carlo SImulating Medical Imaging Nuclear Detectors (SIMIND) code for samarium-153 (Sm-153) imaging. Materials and Methods: The comparison is based on the Monte Carlo simulation data with the results estimated using TEW method. Siemens Symbia gamma-camera equipped with low-energy high-resolution collimator was simulated for Sm-153 point source located in seven positions in water cylindrical phantom. Three different main-energy window widths (10%, 15%, and 20%) and three different sub-energy window widths (2, 4, and 6 keV) were evaluated. We compared the true scatter fraction determined by SIMIND and scatter fraction estimated using TEW scatter correction method at each position. In order to evaluate the image quality, we used the full width at half maximum (FWHM) computed on the PSF and image contrast using Jaszczak phantom. Results: The scatter fraction using TEW method is similar to the true scatter fraction for 20% of the main-energy window and 6 keV sub-energy windows. For these windows, the results show that the resolution and contrast were improved. Conclusion: TEW method could be a useful scatter correction method to remove the scatter event in the image for Sm-153 imaging.